Deep Sky Colors - Astrophotography by Rogelio Bernal Andreo http://blog.deepskycolors.com/ Deep Sky Colors es 2012-01-01T03:54:00-08:00 Sat, 04 Feb 2012 13:34:34 GMT hourly 1 2000-01-01T12:00+00:00 ZoomBlog http://www.zoomblog.com/pics/blogs/ZoomBlog_mini.gif http://www.zoomblog.com/ San Francisco New Year 2012 Fireworks http://blog.deepskycolors.com/archive/2012/01/01/san-Francisco-New-Year-2012-Fireworks.html http://blog.deepskycolors.com/archive/2012/01/01/san-Francisco-New-Year-2012-Fireworks.html
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My idea was to build a panorama that would continue the above image both left (to show more of the Bay Bridge) and right (to show more of the city all the way to the Golden Gate bridge), but the road was small, we weren't legally parked, and right after the moment I decide to take the tripod out to take some photos, a friendly CHP car drove by and started kicking everyone out. At least they arrived near the end and just enough time for me to take this shot while the police officers were asking others to leave.

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]]> 2012-01-01T03:54:00-08:00 RBA Lunar Eclipse http://blog.deepskycolors.com/archive/2011/12/11/lunar-Eclipse.html http://blog.deepskycolors.com/archive/2011/12/11/lunar-Eclipse.html
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On December 10th, 2011, I woke up at 4:45am, loaded my mount, Canon camera and the FS152 in the car and headed to the Windy Hill area in Skyline Boulevard.

My original plan was driving to San Francisco and hopefully catch a wide view of the Moon during totality with the Golden Gate bridge in the foregraound, but unfortunately, I didn't get up early enough, so I went for Plan B (Skyline).

Once there, by the road, there were a few cars from people who had also got up early (or simply hadn't gone to bed yet) to catch a glimpse of the eclipse.

I mounted the stuff,not even sure if I'd be able to reach focus with the adapters Ibrought with me (I had never put the Canon on the FS152).I didn't power up the mount, so I pointed at the Moon manually, gotfocus swapping adapters after a few "oh shut..." and captured a few shots of the eclipse.

I made however one bBig mistake: I didn't realize I was shooting at the highest ISO of thecamera, so noise was bad.... Because of that, and also because of the very low altitude of the Moon during totality (barely 10-15 degrees above the horizon), the image could not stand any deconvolution, so what you see is the image pretty much as it came out of the camera.

After totality and as the Moon was about to disappear behind a hill, Itook the camera out of the scope, did and shared some visual views,put the camera on a tripod with a camera lens, and shot this one:

Unimpressive, and not nearly as sexy as having the Golden Gate bridge or someother cool land features, but the whole event was fun and I had someinteresting talk with the folks that also went up there to watch theeclipse (and who were rather impressed with that big scope the FS152is :-). As one friend said, rather than a great picture, it's just a testimonial image: I was there, and this is the souvenir that I took with me. That's all!

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]]> 2011-12-11T23:38:00-08:00 RBA Simeis 147 and surroundings http://blog.deepskycolors.com/archive/2011/12/08/simeis-147-and-surroundings.html http://blog.deepskycolors.com/archive/2011/12/08/simeis-147-and-surroundings.html

Simeis 147, a supernova remnant also known as Sharpless 2-240, is an object typically photographed with narrowband filters, because under visible light it just appears too "poor" in comparison, mainly due to the fact that this object is extremely faint when imaged through RGB filters - and not too bright when using narrowband filters either! Narrowband data however deprives us from viewing the many other things happening around it.

Most narrowband+broadband compositions I've seen (usually H-Alpha + RGB or H-Alpha + LRGB) haven't been able to "fix" that, so I decided to give it a try, also expanding the typical already-wide FOV, to hopefully capture and visually document more of what's around.

The image being presented above includes the entire field I photographed, in a 3x1 mosaic, but down here you can see a composition that focuses on the supernova remnant itself:

Successfully combining narrowband data (H-Alpha in this case) and (L)RGB data can be tricky. One of the usual results is that, since H-Alpha data tends to produce very small stars, when combined with broadband data, the resulting image often presents a rather severe ringing around the stars. Also, some conventional techniques rely on mixing H-Alpha with the red (R) and blue (B) data, but in this case, my RGB data was rather poor so I couldn't rely on just this technique. Therefore, for this particular image I followed a number of conventional as well as non-conventional methods that proved to be rather successful in producing an image that visually documents this area of the sky. Also, as usual in many of my recent images, a multi-scale approach dominated post-processing, in particular to bring out the fainter details that hide behind the swarm of stars.

My daughter says this supernova remnant looks like a Christmas tree ornament, although I kind of see a piggy's head instead! :-)

]]> 2011-12-08T22:19:00-08:00 RBA The Great Square of Pegasus http://blog.deepskycolors.com/archive/2011/11/10/the-Great-Square-of-Pegasus.html http://blog.deepskycolors.com/archive/2011/11/10/the-Great-Square-of-Pegasus.html
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Earlier this year, when I was done with one of my projects (I think it was the teapot), I told Eric Zbinden "I'm not sure what to go for next"...With a mysterious voice he said "I have a suggestion for you" ... "Yeah, what?" ... "The square in Pegasus".

We both laughed. Yeah... sure!

But despite I didn't even consider for a second to go for Eric's "suggestion" at that moment, I did a bit of study on the area that revealed that there are indeed some high latitude molecular clouds floating around that area, and that was enough for me to start planning a macro-mosaic on the not-so-small square... With my current equipment, that meant a 20 pane mosaic of an area of the sky presumably unexciting from an aesthetic point of view, but hopefully interesting from a documentary standpoint. I tell you, mosaics aren't easy, but large ones are a pain in the butt. When you plan a mosaic this large - and remember, this is still a hobby - you hope to be somewhat rewarded, but in this case I really wasn't sure what I was going to get. Of course, there's only one way to find out.

Many miles of driving to dark sites, and hours of sleep lost, here's the results.

The data for this image was so scarce (75 minutes total LRGB per pane with just a few exceptions) that I was on the verge to put the project to sleep and get more data some other time.

Still, after some post-processing, and presented at the "right" scale, I felt the image met the criteria of at least visually documenting some of the clouds that populate the Great Square, and that's all the image aims to achieve: nothing but "there is a lot of stuff there and the image hints you about the position, shape and brightness of these clouds", and have it rest until someone else comes along and either does the whole area again but in great detail and depth, or produces imagery of smaller areas in this field.

You all know how big this area is, but we're so used to see deep sky images covering much less sky, that the sense of scale may be hard to grasp at first. The FOV is about 18.3 x 15.3 degrees.

A side note: This was the first time I attacked two mosaics almost simultaneously. During the month of October, my main project was the From Pleiades to Hyades mosaic, but I was splitting my time to capture this mosaic in Pegasus during the first hours of darkness, then switch to the (more visually rewarding) Pleiades/Hyades mosaic. This, perhaps extreme, ambition of capturing and finishing both mosaics in a one month time is what resulted in both mosaics - particularly this one - having less than ideal data. Lesson learned: just don't do that again! :-)

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]]> 2011-11-10T14:15:00-08:00 RBA From the Pleiades to the Hyades http://blog.deepskycolors.com/archive/2011/11/06/from-the-Pleiades-to-the-Hyades.html http://blog.deepskycolors.com/archive/2011/11/06/from-the-Pleiades-to-the-Hyades.html
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Here's one of the projects that kept me busy the month of October.

It's a 12 pane mosaic of the area that goes from the Pleiades (M45) all the way to the Hyades. An area that we know well it's quite "dusty" around M45, in part contributed by the Taurus molecular cloud, but that as this image shows, and as expected although not commonly imaged, it really extends all the way to the famous V-shaped open cluster that lies behind the red giant Aldebaran.

I wasn't quite sure in which section I should post it: Star clusters or nebulae. Clearly the reference objects are two open clusters - M45 and the Hyades - both of which are in fact visible naked eye even from moderately light polluted skies. Yet, the predominant structures in the image are the dusty clouds that swirl across the entire field of view. I guess that's the problem with very wide field views: they get a bit of everything!

My favorite presentation is vertical (portrait), as this is how I get to see this part of the sky as it comes from the eastern horizon, although for presentation purposes, the smaller version up there is shown in landscape orientation.

As usual, capturing this data required me some "unusual" amount of driving to dark sites, this time reaching over 1,650 miles.

Data was rather minimal almost by design (click on the "Show image details" below to see the number of subexposures, etc). On top of that, transparency was quite poor during the whole month, and I was getting barely 21.1 ~ 21.2 SQM readings every night at the dark site I usually go to capture the data, while the average at the site is around 21.5, and all the way to up to 21.8 on exceptional nights. Still, despite all that, I think the image came out okay in general, and pretty good considering the amount of data and transparency conditions. More data wouldn't have hurt, particularly color data, but what's new? :-)

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]]> 2011-11-06T17:52:00-08:00 RBA Overcast in the Constellation of Aries http://blog.deepskycolors.com/archive/2011/11/01/overcast-in-the-Constellation-of-Aries.html http://blog.deepskycolors.com/archive/2011/11/01/overcast-in-the-Constellation-of-Aries.html
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The constellation Aries is bathed with numerous dust clouds. This image shows a small region - small in comparison to the constellation - near the also dusty constellations of Taurus and Perseus.

The dusty clouds you see in the image may feel a bit soft, prompting the trained observer to think that noise reduction was heavily applied. However, that's not the case in this image. Although I did apply a bit of noise reduction during the post-processing, it was in fact very mild, and the reason for the clouds having that soft appearance is because in the original data these structures were already lacking the tri-dimensionality and wispy appearance one would usually expect.

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]]> 2011-11-01T00:00:00-08:00 RBA The making of Clouds of Perseus - Part I http://blog.deepskycolors.com/archive/2011/10/29/the-making-of-Clouds-of-Perseus--Part-.html http://blog.deepskycolors.com/archive/2011/10/29/the-making-of-Clouds-of-Perseus--Part-.html Bob Caton, Eric Zbinden, Al Howard and myself. This article describes how this project came to be, from beginning to end.

Part I mainly talks about the planning and data acquisition.
Part II will talk about the post-processing of the data into the final image.
Part III will talk about the making and testing of the light box.




The idea
Early in the summer of 2011, Bob Caton approached Eric and I and told us this idea he had to build a huge lightbox to display at the following AIC (Advanced Imaging Conference), displaying some astrophoto. Of course, the idea was to capture the image by ourselves.

Eric and I agreed to work on capturing the data (Al would join later). Of course, we also had to decide what to photograph. Originally Bob had the idea to do a large mosaic in the Cygnus area. I hesitated alleging that the Cygnus area had been photographed plenty of times, and although it would certainly look amazing in the lightbox, we should try to go for something less "ordinary".

I suggested something in the region of Perseus and Taurus that would include the California nebula, or the Pleiades, or both. This suggestion came from knowing well this area is crowded with interstellar dust. Eric immediately agreed and so did Bob.

Timing is everything
We had one problem, and not a small one. In order to have the light box ready for the AIC, we only had until September's New Moon period to finish capturing the data, as the printing of the negative had to be done by mid-October.

It takes a quick look at any planetarium software to see that this area of the sky is impossible to photograph early in the summer, and if we were to use the months of August and September, we would have to wait until at least 1-2am in August to start imaging, and not much earlier than that in September. This limited our imaging time considerably, to the point the idea was almost rejected thinking that we might just not have enough imaging time.

It is worth mentioning at this point that neither Al, Eric or I have permanent or remote observatories, and all the data would have to be captured "in the field", that is, driving to dark sites every night we had to capture the data. Also, because we wanted to go deep, moderately dark skies were not sufficient - more on that later.

The framing
Because the light box was going to have very specific dimensions, we had to define our mosaic according to the proportions of the light box. Although the idea of an image including the California nebula and M45 was very appealing (I would know, as I captured this area back in 2009), this constraint with the proportions forced us to choose one or the other, and then try to define a field of view that would "make sense". We settled for the California nebula, and defined the FOV towards IC 348 and NGC 1333. It took a few tries... We first agreed we didn't want NGC 1499 too much to the left of the image, and with that in mind, Bob presented a framing very well balanced, I made a small adjustment, and we agreed to go with it. Bob punched in the coordinates so we all would get the very same numbers, and we finally were in agreement. Although Eric and Al were going to use a FLI PL 16803 camera, we agreed to define the mosaic using the FOV of the 11000 CCD - basically, using the smaller FOV that was going to be used.




Planning
We agreed that Bob would capture H-alpha data from his observatory in Modesto, for the area of the California nebula, and then, Eric, Al and I would go for the LRGB data. I pointed out that the best way would be if each of us were assigned certain panes, and then did the complete LRGB for those panes - as opposed to, say, have Eric capture the red data, Al the green and me the blue.

As the New Moon period for August was approaching, and since nobody else was "making the decision", I quickly assigned panes this way:

Bob: Panes 2 and 7, H-Alpha only
Eric: Panes 5, 9, 10 (LRGB)
Al: Panes 3, 4, 8 (LRGB)
Rogelio: Panes 1, 2, 7 (LRGB)

This selection wasn't completely random. Eric and Al's areas were for the most part, adjacent, which made sense since they were going to use the same type of camera. And the area of the California nebula was assigned to the STL 11000 (me), since it is a high signal area compared to the more dusty areas. Yes, pane 1 (also assigned to me) only contains extremely faint dust, but in order to meet the other conditions, it was either pane 1 or 6 for me.

If you notice, yes, pane 6 is missing in the list above. With three panes per person (fair and square), what I suggested was that whomever finished his three panes first, would go for pane #6. By the way, ultimately it would be Eric the one who captured pane number 6.

We also agreed on capturing a minimum of 4 hours of luminance per pane, as well as 2 hours per color channel, all bin 1x1 of course, and with 15 minutes subs.

When doing the numbers, counting the nights, considering the target wasn't well positioned in the sky until late at night, etc. we knew that the weather had to cooperate 100% every single "New Moon night" we could go out to image, or we would just not make it. Stressful? Just a bit :-)

Capturing the data
Al, Eric and I started collecting data on August 27th, 2011, at the DARC Observatory, while Bob also started capturing H-Alpha data at his home-based observatory in Modesto.

Eric and Al used a very similar setup, with AP900 mounts, Takahashi FSQ106 scopes and the FLI Proline 16803 camera. I used a Takahashi EM400, another Takahashi FSQ106 scope, and the SBIG STL11000 camera. Bob also used a SBIG STL11000 camera, and yet another Takahashi FSQ106 telescope, all on a Paramount ME mount. The fact we all were using the same type of scope and that all cameras had the same pixel size, made everything a bit easier, as no resampling would be needed during mosaic assembly or post-processing.

A few words about the DARC Observatory. It is actually property of Bob, sitting in the blue zone (Bortle scale), and it's about 120 miles away from where Eric and I live, and about 110 miles from Al's home.

This means that every time we would go to DARC to capture data, we would have to drive 120 miles to the site, usually fighting the evening rush hour traffic, and then 120 miles back, in the wee hours of the night - most of the times fighting the morning rush hour traffic! That's not just 240 miles for every single single session, but 240 miles that includes dealing with rather heavy traffic conditions for about half of the trip. An of course, taking everything out of the car and setting everything up at the beginning of the session, and tearing down and packing it back to the car at the end, every... single...  night.

Here's an image of the three scopes, set up in the open dome at DARC, capturing data for the project:

Left to right: Eric's, Al's and my scope. The distortion you see in the image is due to a 10mm lens being used to take this photo. If you pay attention you might even see Eric's "ghost" sitting at his table :-)

I believe Eric imaged almost 14 days in a row (!!!). I know I did  8 days in a period of 14 days, and although I don't remember Al's schedule, it was just a tad shorter than mine. Some simple math then tells us that if you were to add the miles driven by Eric, Al and I during these14 days of New Moon period to the DARC Observatory, we'd be talking about approximately 7,000 miles and over 110 hours at the wheel. I've lost track of the time spent at the site, but the numbers are probably just as crazy. The fun part? We were not even nearly done, and another Herculean... I mean Perseulean effort coming up for the next New Moon.

Besides everything I've mentioned, driving 2 hours to a dark site during weekdays is also not easy business, as we all have to, well, WORK the next day, so although neither of us were using automated software to program our sessions, whenever we had a chance, we would set up a cot inside the observatory and try to catch a few zzz's... just not too many, and certainly, never more than a few in a row... here's my cot waiting for me:



By the way, don't be fooled :-) Although the image is all bright and the room looks nice and lively, during our imaging sessions we keep the building with minimum red lights only, so the atmosphere in the room is always rather gloomy when we're there doing our thing. Don't get me wrong, I love DARC, I just don't want you to get the impression that during our imaging sessions we enjoy "normal" lighting and activities :-)

More data!
The new moon during late August and early September wasn't nearly enough to complete the mosaic. We needed great weather during the next New Moon, and so we waited patiently for it. And when it came, although the forecast for the first few days wasn't so great, Mother Nature gave us a break, just long enough.

This time around, Al and Eric continued going to DARC, but I actually headed to the Central Nevada Star Party (CNSP), seeking some of the darkest skies in the country. A rather moody weather didn't give me those greatest skies the CNSP is famous for, but I was able to finish my part under fairly good skies after all - just not nearly as dark as the site for the CNSP could get. Al and Eric also managed to finish their part, not without some sacrifice as in "I wish I were done, I could use some rest, but I need to go again tomorrow" perhaps a couple of times.

Take away one night and we would have not been able to finish. It was THAT close!

But the weather cooperated and gave us all the nights we needed, and finally, after another intense New Moon period, we were ... done!!

Of course, I had this little incident I wrote about the other day, but the outcome from that night was good, and so we finally had all the data we wanted.

With all the data, what was left for us to do was to calibrate our subs, generate our own master L, R, G and B - and H-Alpha for Bob - and share the masters with the team.

There was not one particular person assigned to do the processing. The idea was basically to share the data and whomever wanted to have a go, just do it. In the end, only Eric and I decided to go for it, and he ended up having to concede the work to me, as he got extremely busy at work and with not enough time to do his processing on time. In the next part of this article I will talk about how I processed the data, from mosaic construction to final presentation, and everything in between.

]]> 2011-10-29T00:58:00-08:00 RBA Clouds of Perseus http://blog.deepskycolors.com/archive/2011/10/23/clouds-of-Perseus.html http://blog.deepskycolors.com/archive/2011/10/23/clouds-of-Perseus.html
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This image is a collaborative project between Bob Caton, Eric Zbinden, Al Howard and myself. A 2x5 mosaic of sorts. Four FSQ106 scopes, two SBIG STL11k and two FLI Proline 16803... Some insanity and a lot of coffee (for me at least, the others I think only drink Red Bull :-).

128 hours of data. Many more hours accumulated in driving to darksites - mainly to the DARC Observatory and the Central Nevada Star Sarty - and over 7,500 miles driven, just by Al, Eric and myself.

I did the post-processing for this version, and it probably took me over 12 hours to put everything together up until the final version.

There was a "deadline" for this image, so we had to workon this one around the clock to the point at times it didn't even feel this was a hobby but a job, but still, now I think it was well worth it. Of course, the image is not perfect, but what is?

Colors are stronger than what I'd usually process them but there's a reason for that: the image will be printed on a 14 feet wide duratran-like transparency for a lightbox display at some upcoming event, so I prepped it for that by pushing saturation more than whatI usually do, and then figured I'd let it stay that way for regular"web" presentation since it was looking cool enough that way.

I must say I've enjoyed very much to work on this collaborative project, and I hope there'll be more to come!

This image was selected as NASA's Astronomy Picture of the Day on October 21, 2011

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]]> 2011-10-23T18:01:00-08:00 RBA Extreme Nomadic Astrophotograpy http://blog.deepskycolors.com/archive/2011/10/06/extreme-Nomadic-Astrophotograpy.html http://blog.deepskycolors.com/archive/2011/10/06/extreme-Nomadic-Astrophotograpy.html
...

Well, it's no secret anymore that a few colleagues (Bob Caton, Al Howard, Eric Zbinden and myself) have invested over 125 hours of imaging (and probably even more of driving combined) in producing a macro-mosaic that will be displayed at this year's Advanced Imaging Conference 2011.


Bob Caton standing in front of the huge light box

Despite we haven't started to process the data just yet, what has been done so far is quite a feat. Still, two days ago I realized that the green data for one of the frames assigned to me was just rubbish (I'll spare the details), so here I am sitting, Thursday October 6th, loading up my car, because tonight, with a big bright Moon that sets at 3am, I have the very last chance to head up to a dark location and capture the minimum 2 hours of green data that I need - from 3am to 5am - otherwise the project will not see the light in time for AIC.

Yes, I work tomorrow. And yes, I'm tired and sure enough, ready to go to bed... otherwise... And although the forecast is for clear skies, temperatures in the mid 30s are expected (hey, those of you up north, this is California and it's only early October... ok? ;-), and extreme high humidity. I would never go out to capture data for a 3-5am session only, but if I don't do it, all the hours already invested would have been worthless, meaning the image will never make it on time for the AIC event.

Where to go? I could go Montebello, an easy 30 minutes drive from home, but the skies really have little to do with the skies we all have taken the data. Sure, it's "just" color data, but still. That would also mean breaking the Montebello OSP rules, which dictate that we can be there for astronomy up until 2am and no later than that!

I could go Henry Coe... This target will be up at the zenith between 3-5am and Coe's skies would likely be sufficient for green data, but let's face it, Coe can feel spooky at times when you're up there all alone (or in the company of mountain lions), and the of arriving at Coe around 2am, under near freezing temps and over 95% humidity, just is NOT my idea of having fun. Or I could go to the DARC Observatory, a rather safe and not spooky at all site,  but the 2 hours drive that requires to get there - or better said, to get back home - would conflict with my schedule: I would get out of there not earlier than 5:30am, meaning getting at home - after fighting morning rush hour traffic - around 7:30 or later, and my kids would be late for school...

So the choice is between Spooky Coe or Bright Sky Montebello (and risk my access to the site if caught there after 2am). Since I don't want to break any rules that would compromise my access - or anyone else's - to Montebello, I guess the choice is clear, and in about 2 hours I'll leave for Henry Coe State Park, and deal with the spookiness, the cold and the humidity all night long pretty much until sunrise. That of course, assuming my access to the overflow parking lot is not stopped by a gate I cannot (legally) unlock, as I haven't been there in months!

Now, I mentioned earlier that having to leave at midnight to a far dark location and fight with the cold, humidity, and yeah, spookiness, is anything but fun, but here's the thing... Despite it would be very very nice to simply hit a few buttons from home and capture the data remotely while I just go to sleep, as many people do nowadays, nomadic imaging is not only about the data, the processing or the presentation, but also about the adventure and a million other things. And despite the difficulties, the inconveniences, the lack of sleep, the expense (gas is not cheap!) and everything else that comes with it... At least today, in the end, it makes it all much more worthy, at least to me, and I wouldn't change that for the world.

And trust me when I tell you that Eric and Al also had their share of issues, such as driving 2 hours to DARC and then being able to capture data for barely one hour due to clouds, then drive 2 hours back home late at night, tired and all...

Maybe to some people - not everyone! - astrophotography does taste better when you actually have to sweat it, I don't know... I still dream about a remote observatory, don't get me wrong. But that won't stop me from taking trips to dark sites. The best image cannot compare to being under the stars.

And in the end, if everything goes according to plan, I'll get that green data and on November 4th, there'll be a giant lightbox at the AIC for everyone to, hopefully, enjoy.

Well, everyone but myself, as, things being what they are, and despite I haven't missed one AIC ever since I'm into this hobby, this year my "astro budget" has severely reached its limit and I cannot afford the registration fee for this year's AIC. Either way, if you go AIC this year, I hope you enjoy the exhibit and maybe remember that getting all the data wasn't all that easy :-) ...

]]> 2011-10-06T22:41:00-08:00 RBA Circumpolar from the Central Nevada Star Party http://blog.deepskycolors.com/archive/2011/09/24/circumpolar-from-the-Central-Nevada-St.html http://blog.deepskycolors.com/archive/2011/09/24/circumpolar-from-the-Central-Nevada-St.html
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Here's a circumpolar image I captured the last night at the 2011 Central Nevada Star Party.

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]]> 2011-09-24T21:59:00-08:00 RBA The Teapot in Sagittarius http://blog.deepskycolors.com/archive/2011/09/14/the-Teapot-in-Sagittarius.html http://blog.deepskycolors.com/archive/2011/09/14/the-Teapot-in-Sagittarius.html
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This is a 16 pane mosaic of the "Teapot", a famous asterism in the constellation Sagittarius.

I started this project early June from DARC. I didn't continue capturing data for it during the GSSP early July because at 41 degrees of latitude, this object was just way too low in the sky (not that it isn't at 36-38 degrees).

So it was only during my visit to Spain that I finished it during several visits to the Pinar de Araceli in the province of Granada.

Stitching the 16 panes for this mosaic turned out to be harder than what I had anticipated - and I've done a few mosaic to know what it takes. The good news is that the new GradientsMergeMosaic tool in PixInsight (which I didn't use for this mosaic) is just amazing, so stitching new mosaics should be much much easier regardless.

Also, the are of the Lagoon nebula wasn't in the plan originally, but I ended up deciding to add it, from the macromosaic I captured last year of the "From Rho Op to M16" area. The original framing only included the Teapot area and nothing else, but, although the framing may feel a bit unbalanced now, I feel the Lagoon gives some sense of position and reference that I personally like.

Here's a small version of the image with the asterism and most significant objects:

And here is the same but at a larger size.

 

]]> 2011-09-14T22:43:00-08:00 RBA The value of an astrophoto http://blog.deepskycolors.com/archive/2011/09/12/the-value-of-an-astrophoto.html http://blog.deepskycolors.com/archive/2011/09/12/the-value-of-an-astrophoto.html reality of what is out there? Can an aesthetically-driven astroimage have scientific interest? Can we talk about science versus art, when comparing astroimages that have been minimally processed with images that have gone through some more complex post-processing? Do minimally processed astroimages have more value than those with a more involved post-processing?

These being recurring topics in the astroimaging community, I've decided to post my thoughts here  - it will make it easier next time someone brings these issues, once again, somewhere.... :-)

(I use the terms "minimally processed" and similar throughout this article referring to images that may only include during post-processing a small set of operations such as deconvolution, DDP, some non-linear histogram transform and little more. It is not meant to be a derogatory term in any way.)

And here's what I think...


Can an astrophoto represent reality of what is out there?

I believe that in astrophotography there's no such thing as a natural or realistic appearance. Reality in an image is just impossible to depict, and even more so in  astrophotography. The reasons why I strongly believe this might take some writing, and there are other points I'd like to cover without you falling asleep before you get to them, so I'll probably go back to this topic at a future date. For now, just think for a second: we're trying to represent objects and structures that are thousands or millions of light years away and that are often larger in size than what our mind can even conceive... and we're doing that right in front of our eyes, and in a monitor that at most is just a few inches wide (not to mention the extremely poor dynamic range they can represent). How's that for real?


Can an aesthetically-driven astroimage have scientific interest?

Actually, I don't think scientific interest is something that needs to pass the "is it minimally post-processed?" test.

The way I see it, there will be aesthetics-driven images that might ignite some scientific interest, and likewise, there will be images minimally processed that may never attract the interest of scientists at all. It's quite simple. For example, when some astronomers saw this image I took of the Virgo galaxy cluster, (overprocessed to some, of course) they contacted me to provide them with a non-linear stretch of the raw data - which I did, and it proved to be quite interesting (I cannot say more than that at this time, sorry). Should I have not pushed post-processing with some techniques such as HDRWT, wavelets, morphological transformations, etc. the image likely wouldn't have ignited any "scientific interest" at all. Need I say more?

Yes, if your post-processing has introduced artifacts that haven't been seen before, you might ignite some scientific interest for the wrong reasons, and that's why you must be careful not to introduce such artifacts! But other than that, this debate is quite simple, there shouldn't be a debate.


Can we talk about science versus art, when comparing astroimages that have been minimally processed with images that have gone through some more complex post-processing?

 This is another topic that I don't quite know why it's brough out so often. It's as if there's some sort of consensus that astrophotography needs to be separated into the "science approved" images and "astro art" or something, when the way I see it, that's a neither and nor...

I don't usually consider an astrophoto to be pure "science" once the image is no longer linear, so, unless the post-processing involved incurred in blatant inventions, I don't usually make the distinction of "science vs art" with images that are non-linear when presented to the viewer, regardless of the amount of post-processing.

So when these topics come up at mailing lists, web forums or even conversations, I don't think it's correct to talk about "science vs art" as if those folks who do minimal processing to their images are producing science-approved images while everyone else is doing just "astro art".

Of course, some of these folks will tell you otherwise, but the way I see it, in most cases, both groups are producing something that has inherited qualities from combining both disciplines - art and science. And that is what astrophotography really is, as far as I'm concerned. In simple terms, if it's only science, you're doing astronomy, and if it's about aesthetics and nothing else, it's likely just art. To me, astrophotography is a bit of both - yet not a whole lot of either - and if one of them is missing, then it's something else.


Are we not respecting the data when we apply post-processing techniques such as the star reduction method described here? Are we being unethical?

I disagree that techniques such as the "star reduction" method (link above) and many others show no respect for the data (more on that later) or are unethical, but regardless of what you think, to me, bringing up that question is, once again, missing the point completely about what the value of astrophotography is. In the next paragraph you'll probably understand -  agreeing or not - what I mean by that.


Do minimally processed astroimages have more value than those with a more involved post-processing?

What I believe is that an image can have documentary value, whether the pixels around a star have been dimmed, have inherited values from the surrounding pixels, or have been left intact after some operator-chosen non-linear histogram stretch. And such documentary value can be just as valid regardless of which of the previous operations have been performed.

What matters is the intent of the operator and there's a lot one can say about that. Of course, one can start "inventing features" to the point the image may lose its documentary value. This is not to say that doing such things are necessarily "wrong", because astrophotography can also have a worthwhile emotional and aesthetic value despite some people who say are science-driven may ridicule the idea... When you go that far, it simply means that the image no longer has documentary value, and it should be treated, viewed and analyzed as such.

The issue about "respecting the data" and "ethics", when brought up as a matter of keeping the post-processing to a very minimal set of operations, besides being quite recurrent, usually brings issues that to me, don't mean much because, as I said, to me, they often miss the mark.

As I said earlier, to me, generally speaking, if you like to analyze data, you should stay in linear-land, and once you cross that line, what matters is whether your image has documentary value. Whether you are content by doing a couple of post-processing operations such as deconvolution, a non-linear stretch, and a few more, or take advantage of many other post-processing techniques that can indeed enhance the documentary value of your data, that's a personal choice.

And within that personal choice, in some cases, and depending on the goals, a minimalist processing may in fact be a very good choice for bringing up some very good documentary value in an astroimage (some people in fact favor the look of such images, but we're not talking about the look of astroimages here, so comments in that regard aren't needed in this discussion).

What I believe however is that by limiting yourself during post-processing to a restricted set of techniques "because I want to respect the data", laudable as it might be, you might also be missing an opportunity to increase the documentary value of your image, while still respecting your data. And here's the thing... As long as you are increasing the documentary value of your image, you are respecting the data, simply because you're utilizing the data to present an image that not only holds value above purely aesthetics, but it also maximizes what is really worth. It is only when you depart from that documentary value when your respect for the data decreases.

So, if maximizing the possibilities of your data with the purpose of increasing the documentary value of your image is - according to some people - a "disrespect" for your data, what exactly is to NOT maximize it and produce an image with a likely less documentary value?

Of course, some people may not buy this explanation about "documentary value" or may view it differently. If they did, I wouldn't have a reason to write this, now would I? :-)

In any case, if you want your image to possibly miss on that increased documentary value because of the way you value your data or because of your beliefs of what is ethical or not, that's fine. As I said, that can be a valid option. However I have no desire to show complacency to any statement that regards astrophotography as a discipline that should limit itself to a couple of simple techniques during post-processing in order to have value or to be considered ethical, because, as stated, IMHO, where those who think that way believe the value ends, some of us take on and keep on adding the value they ignore, disregard or are simply shortsighted enough to not recognize it.

From this point of view, I don't think minimally processed astroimages have more value than those with a more involved post-processing - to me, often times it's quite the opposite, in fact. And this is without getting into the topic of aesthetic value, because that's another deal, not to be disregarded.



An image is worth a thousand words

Recently I took an image of the Great Square of Pegasus, a 20 panes mosaic. After all the work of putting the mosaic together seamlessly, my first post-processing steps were basic non-linear histogram adjustments. Right before I started to utilize more advanced techniques, the image looked pretty much like this:


That is the equivalent of what some would describe as "minimalistic processing". And I could have stopped there. And that image has some undeniable value. But a strong (linear or not) inverted stretch revealed a lot of faint structures, and I wanted to visually document those structures. Not measure, not analyze, simply trying to produce an image that would be able to show the shape, position and relative surface brightness of those structures, hopefully without destroying the appeal of this starry area of the sky. For that task I knew I had an arsenal of techniques - not tricks - that could aid me in reaching that goal (and for those interested, no, such techniques don't involve the use of the brush, lasso or similar tools). So there was my choice. Should I stop here and present an image of lots of stars, or go further in the post-processing? Well, to me it wasn't even a choice. I knew I wasn't going to stop there... A reduced version of the final image is here:

Now, when you end up with an image like the one above, you have to expect that some people is going to say - or think - that the image has been overprocessed, perhaps even say things like "those clouds of dust look like made out of plastic" and other nasty stuff. Um... How is it possible that supposedly smart people can in fact react with such ignorant comments? Let me tell you upfront that the dust clouds you see above not only exist and are up there, but their shape and position match exactly what you see in the image, at least to the point I was able to capture (not post-process) their signal. All that stuff was in my data, but the only way to make it surface was by using post-processing techniques that those who defend minimally processed images either don't know or at best, don't want to use (more often than not, they really don't know - after all, why learn about something you're not interested anyway?).

Is this all about beauty? If I cared about just beauty, why would I want "my" dust clouds to look like plastic? (that's assuming that's how they really look like)... Now I ask you... which photograph better documents what's going on up there? Why should I limit the processing on this image, due to whatever some ethics dictate, and show a patch of the sky with nothing but stars and a few tiny galaxies, when I could greatly increase its value and show all what really is going on, even if that means pushing the data to its very limits? Maybe ethical in this case means we'd rather not see what's behind all those stars?  Well, I do.


Final words

Everything you've read so far is not meant to justify aesthetics, documentary driven astrophotography or advanced astroimage processing techniques. To me, they're plentifully justified and need no exculpation. This article is simply an attempt to share my views on a much discussed topic, for which I think some people, for whatever reason, tend to disregard or downplay astroimages that include more than a simple non-linear stretch, while, in my very humble opinion, as stated, applying advanced post-processing techniques can be used to increase the documentary value of your data.

Last, let me add... While it's true that some people resort to "easy Photoshop tricks" to post-process their astroimages,  advanced image processing techniques aren't what I'd call "easy" tasks, and calling tricks to anything that goes beyond a non-linear stretch often simply denotes either ignorance or arrogance - usually both. Advanced post-processing techniques require study, learning, experimentation, patience and sometimes frustration, unlike minimalist processing which often times doesn't require any of that. You can choose to use them or not, but be respectful with your peers when you state your opinios, otherwise, the only one who may look clueless will be you - although of course, you will never ever think that's the case (back to arrogance and ignorance).

Of course, learning and experimenting with new post-processing techniques and paradigms can too be challenging, rewarding and fun. And who is to tell others how they should have fun? Aren't those some of the most valuable reasons for which we embarked in this journey after all?

Happy processing!

]]> 2011-09-12T00:30:00-08:00 RBA Pinar de Araceli, Summer 2011 http://blog.deepskycolors.com/archive/2011/09/11/pinar-de-Araceli-Summer-2011.html http://blog.deepskycolors.com/archive/2011/09/11/pinar-de-Araceli-Summer-2011.html This past summer I visited Pinar de Araceli 6-7 nights, and although I didn't take many images of the scenery, I did manage to take a few, and I decided to write this small photo-documentary, hoping to transmit a bit of the experience, although of course, as with any photograph, nothing beats to actually being there.

Most of the nights, my SQM easily reached 21.7 which I consider pretty good and average for the site. Anyway, here's the report... Enjoy!!

The road to Pinar de Araceli from Murcia - where I live when I'm in Spain - is quite comfortable for the most part. Lots of highway and only for the last 20 minutes, climbing up the mountain, it gets narrower and winding, but nothing we're not used to, right? This photo below is actually from the easier part of the drive to the top, but I like the stone-made blocks at the side of the road.



By taking a quick detour, you go through narrow roads such as this one...


...that'd take you to a nice vista point of La Sagra, a 2,383 meter (7,811 feet) mountain peak formed mainly by limestone and loam. Beautiful in winter when it's all covered in snow, can't keep up with the hot summer months. It looks like a peaceful, nice mountain top, but it's not always like that (check this video on YouTube from a few guys at the summit during less than ideal conditions).


Following the detour to La Sagra, in the middle of absolutely nowhere, this house appears. It has a name but forgot... No, it's not a Mission. This is Spain, not California :-)




Only 4km from El Pinar, you find a sign telling you that you're 27km from Nerpio. Why do I mention that? Well, if you've ever used any of the GRAS telescopes, you probably know that the scopes they have in Spain they're actually in Nerpio. Guess it's also kind of like "you're in dark skies country" zone or something ;-)


Once at the Pinar, you see some of the famous cabins. They have about 20 of them...


It's getting late, so we'd better start setting up!


So here's my gear in front of the cabin, one of the nights I was up there all by myself.


And here's another photo of my setup capturing photons!


I couldn't leave without taking a photo of the majestic Milky Way and the cabin. This was actually on a night when there were several of us doing our thing...


As the Sun starts to rise, some amazing colors make you feel the night was good, and worth the trip.


Here's a few photos I took going back home one of the times I went there. This one is at one of the peaks, at around 1600 meter high (5,250 feet), right before sunrise:


And what do you know... Once you're out of the sierra, on the way from La Puebla to Caravaca... Fog!! Yeah, we get that here too ;-)


If you're like me, and tend to head home around sunrise, on the way back you may get rewarded with some nice vistas such as this one...


Or this one...

Then... Back to reality! It was good to be there. Hope to be back soon!

]]> 2011-09-11T15:48:00-08:00 RBA Star size reduction via Morphological Transformations http://blog.deepskycolors.com/archive/2011/09/08/star-size-reduction-via-Morphological-.html http://blog.deepskycolors.com/archive/2011/09/08/star-size-reduction-via-Morphological-.html IntroEvery once in a while, when we are processing our data, in order to craft an image aimed at communicating or displaying something specific, we run into a "problem": the stars in the field are so conspicuous that either distract our attention from the structures behind them, or simply don't allow us to display clearly such structures.

When that happens, one of the solutions is what in simple terms is referred as "star size reduction".

Reducing the size of the stars in our images may sound a bit dramatic. Some people have even declared that such procedures are a sure way to produce fake images.

The truth is that, if we are trying to produce an image of aesthetic and/or documentary value, as long as we apply this star size reduction homogeneously and following a well established criteria - that is, if we "dim" all the stars that share certain characteristics, and such reduction is homogeneously applied to all of them - what we are doing is perfectly acceptable. And while these debates often ignite endless and repetitive discussions, my aim here is not to justify these methods but to show you one way to apply them. For those of us who find these methods perfectly acceptable in order to attain the goals we have set beforehand, there's nothing fake about applying star size reduction techniques via post-processing, and it can sometimes be an enhancement to our images, while preserving and sometimes even increasing documentary value.

Strategy

The choice we need to make is whether star size reduction is what we want for any given image, in order to achieve our goals, and if so, which type of stars need to be dimmed down: the ones that present a very large size in our image, the very dim ones, mid-sized stars...

Usually, very large stars don't need to be reduced in size. At most, they're creating a large glow around them, and if our goal is to show what's behind that glow, other techniques such as dynamic range compression may be more suitable for the task.

Mid-sized stars may be a target, although most commonly, when "stars get in the way" these are small to tiny stars in fields packed with thousands of them.

This tutorial will show you one way to reduce the size of small stars. Unfortunately, I started this exercise with an image that by itself really didn't need any star size reduction. Although this may sound counterproductive and it may not show very clearly the benefits of these techniques, the concepts utilized are perfectly acceptable and the image serves the purpose of showing how it can be done. Just for the sake of argument, at the end of the tutorial I will too present a before/after example of an image that does benefit from star size reduction techniques in order to achieve the goal of not letting the stars block what's behind them.

The Data

The tutorial is based on a set of 4 exposures of 30 minutes each of the Andromeda galaxy, at -10C temperature, with a SBIG STL11k camera and a Takahashi FSQ106EDX telescope. The data was captured at the DARC Observatory in California, on August 28th, 2011. We will be processing this data with PixInsight v1.7.

1 - Building the Star Mask

The very first step in star size reduction via Morphological Transformations (MT for short) is to build a proper star mask. This is to avoid the MT process to actually be applied to non-starry structures. Building the mask is crucial, as it will determine what stars - and in this particular example, also what areas of the stars - will be affected.

Here's a screen shot of part of the M31 image we're going to be working with:



As mentioned, this image does not really call for star size reduction, but nonetheless it presents an interesting situation. We're going to be building our star mask with PixInsight's StarMask tool, and the brightness of the core of the galaxy and surrounding areas may produce a lack of star detection around these areas. Further, we're attacking mid-sized to small stars in the field, but we do not want the young, blue stars that sparkle in the disk of the galaxy to be reduced at all, yet, such structures might be assumed to be what visually may appear as "small, tiny stars".

To solve the first problem, we need to create a duplicate of our image, and "dim" the bright areas of the galaxy without dimming the stars. This can be achieved in different ways, and in this case I have chosen to use the HDRWT tool in PixInsight, which effectively applies a dynamic range compression. Here's the result of applying a rather aggressive HDRWT to the duplicate image:



Now, the above image is better prepared to produce a suitable star mask. Depending on the case, one can apply an even more aggressive HDRWT by either increasing the number of iterations or even reapplying it several times.

It's time to adjust all parameters in the StarMask tool to produce a star mask the way we want it in all aspects. In this case I've chosen the following parameters:



First, I've assigned a value of 0.15 to the Threshold parameter. The threshold parameter is meant to isolate noise from valid structures, but because a higher value will discriminate smaller structures, rising the 0.1 default a bit may help us not only avoiding noise, but also excluding the tiniest of stars in our mask.

The Scale and and Small parameters help us define the type of stars we're after: small to mid-sized stars but not the very tiny ones. While the growth parameter is often times quite useful - it determines how much to increase the masking area - because later we've checked the Contours option,  in order to have a well-defined contour (more on that in a bit), it's better not to grow the masking area. Same thing with the Smoothness parameter. We don't want to smooth out the masking areas too much, just enough, so I reduced the default value of 16 all the way to 5.

Now, the reason I've checked the Contour option is because, whenever possible, I want the mask to only leave unprotected the contour of the stars, which is effectively the area where the "reduction" really takes place. While going for a standard mask is often just as good, I have experienced that going for the contour exclusively gives me better results overall.

Last, note the Midtones parameter, that has a default value of 0.5, has been reduced to 0.25. This simply helps the structure detection to "stretch up" the image - equivalent to moving the midtones in the histogram to the left - which usually results in more stars being detected, and the masks being a tad thicker, since the structures are brighter after pushing the midtones to the left.

NOTE: You should not take these StarMask parameters as a cooking recipe! The StarMask tool uses a multiscale algorithm to isolate significant image structures during the structure detection phase that is strongly dependent on large-scale features of the whole image. In plain English this means that for a given set of parameters, the results you can obtain with StarMask when applied to one image, may be quite different than what you may obtain with the very same set of parameters on a different image. So the key is to understand the effects that modifying these parameter can achieve, and adjust them until the resulting mask is what you were after, or at least close enough.

Once applied, here's the star mask we produced:



Since it's hard to see the details in the above image, here's a close-up at a 1:1 scale:



So we apply the mask and here's how it looks (3:1 scale)  when using red color as overlay to see what is being protected (red) and what's not (transparent):



2 - Defining and applying the Morphological Transformation

With the mask in place, we now can invoke and apply the MorphologicalTransformation tool. Here's a screen shot with the image after applying MT, and the MT dialog box displaying the parameters we used (I'll explain them right after the image):



In the MT tool, first I've chosen the Morphological Selection operator. Most people use the Erosion operator, and it is in fact a proper option, but I like using Morphological Selection because it acts as a blend between the erosion and dilation methods, where, with the Selection parameter you can define how much erosion and how much dilation you want to apply (more erosion the closer you are to a value of 0, and more dilation as you get closer to a value of 1). And while the use of a blend of erosion and dilation in stars usually isn't necessary - as neither are other operations that combine them, such as opening and closing - I like the smoother results that they often generate, versus applying erosion and nothing else.

Last, a round structuring element makes a lot of sense of course, and in this case I chose a 5x5 kernel size because the stars being targeted fit well within that kernel.

Once applied, our stars are now less "in your face" as they were before. As mentioned earlier, this particular  image doesn't really benefit from applying this procedure, but leaving that aside, hopefully you can see the difference.

The results we've obtained can be seen more clearly in this x5 zoomed-in before/after animation:



You can see that the very small stars are not nearly as discernible as they were, the small-to-midsized stars are not only "reduced" in size but also their profile is more round in appearance, and the very tiny, almost invisible stars, are untouched.

3 - Sharpening the results

We may consider that the Morphological Transformation process we've applied has been successful and stop right now. However, in practice, I often like to bring back some of the "life" in the stars that are now dimmer and reduced, but of course without bringing them to their previous state - otherwise I may just not do any MT at all to begin with!

This can be achieved in several different ways, and one of such that I use quite often is by defining another star mask that protects everything but the very small scales in the image, and then use wavelets to increase a bit the bias at those scales.

Building the mask this time is very easy. We simply use the ATrousWaveletTransform tool in PixInsight, deselect all scales except scale 1, increase the bias just a bit, and apply this to the duplicate image to which we applied the HDRWT earlier. Here's a screen shot doing just that:



And here's the mask we just created:



We apply the mask to our image, and then sharpen it only in those tiny "holes" defined by the mask, using the ATWT tool, by using the default values except for an increase in the bias at the smallest scale:



I used a bias of 3 in this case, which is A LOT!! In this case the mask was aggressive, and so the effect is greatly reduced, but you will need to dial the bias to a value you're happy with via experimentation. And here's the result:



4 - Before/After animations

The following animation is big, but it shows the image cycling from the original version, to the version after the MT, to the version after the ATWT:



Last, here's an animation that shows a large closeup of a single star as it was originally, and as it finally ended up after the MT and ATWT processes:



While the appearance of our image has changed considerably - ok, picture this effect on an image that was packed with stars, rather than this M31 shot - I think it's safe to say that the data manipulation involved didn't invent any new data around the stars. It simply "dimmed" the stars, and unlike what some people often thing of these methods, without fabricating artificial "nebula" data around them.

5 - Conclusions

If you have read all the way until here... Well.. You've read a lot! ;-)

As it often happens, as I aim at describing each step in details (rather than just saying "do this, then that, then this, you're done"), this tutorial may seem to be describing a rather lengthy process, but in reality it only involves a few simple steps:

  1. Create a star mask suitable for MT, which in this case it involved using the HDRWT and StarMask tools
  2. Apply MT to our image to "reduce" our stars
  3. Create a second star mask, this time with the ATWT tool
  4. Apply ATWT to "sharpen" the image a bit.

That's all.

6 - A more suitable example

Here is a quick before/after animation of an image probably better suited for star size reduction:



The above is an image of some very faint dust clouds in Lacerta, and it accumulated 7 hours of exposure under very dark skies (SQMs at 21.7 or above, at the zenith) with a 4" scope at f/3.65.

There is nothing wrong with the before image. It shows a field packed with stars to the point that it's nearly impossible to discern the faint clouds. That's just a reality. It just happens that there are a lot of stars in that field!

However, by applying the very same "star size reduction" technique described in this tutorial, we have an image that allows us to better see the dusty structures that before were so elusive, and so we have a better visualization of the nebula. The before image tells a story, but so does the after image - and both stories are concordant with facts revealing a reality.

Not only that, after the MT procedure, we can, if we like, continue post-processing the image to even better visualize the faint clouds. The after image not only has aesthetic value, but also documentary value.


]]> 2011-09-08T00:00:00-08:00 RBA Comet Garradd and the Coat Hanger http://blog.deepskycolors.com/archive/2011/09/03/comet-Garradd-and-the-Coat-Hanger.html http://blog.deepskycolors.com/archive/2011/09/03/comet-Garradd-and-the-Coat-Hanger.html
Click here for a larger version

Sweeping through planet Earth's night sky, on September 3rd, 2001, Comet Garradd (C/2009 P1) visited this lovely star field along the Milky Way in the constellation Vulpecula. Suggestively oriented, the colorful skyscape features stars in the asterism known as the Coat Hanger with the comet's tail pointing toward the southeast. Also known as Al Sufi's Cluster, the Coat Hanger itself is likely just a chance alignment and not a cluster of related stars. But compact open star cluster NGC 6802 does grace the field of view just right of the Coat Hanger, near the edge of the frame. Below naked eye visibility but approaching 7th magnitude in brightness, Comet Garradd has been a good target for binoculars and small telescopes. Still, bright moonlit skies this week will make the comet harder to spot. (Text from APOD).

Here's a different composition framing just the comet and the Coat Hanger:

Get a poster, t-shirt, mug, mousepad... with this image!

]]> 2011-09-03T01:09:00-08:00 RBA