GOALS AND PRESENTATION

It would be easy to produce a "standard looking" image with this data. Truly minimal processing would be required, but in this case and at this time, for me that wouldn't be nearly as fun neither challenging.

The goals when producing this image were very precise. Just a glance at the image should reveal what these goals are, and I am somewhat satisfied with the results - meaning the goals were achieved to an extent. Clearly the main goal was to reveal any subtle and faint data - the data that typically sits right above the noise. A secondary goal was to do this while containing galaxy brightness and at the same time, being able to bring out small scale details in such galaxies.
 
To enhance details in the galaxies, a dynamic range compression process was applied to reduce brightness in the larger galaxies, as well as wavelets-based HDR enhancements. Preserving background illumination was accomplished by very careful gradient reduction and further non-selective histogram adjustments.

There may be some people who find all the "dust" in the background distracting, or the small details in the galaxies somewhat the result of processing and not a "natural" depiction of the field, but ...In order to appreciate this image you need to understand the goals set for it, then conclude whether those goals were met or not, rather than whether you would have aimed for different goals.

DETAILS IN THE DUST

In order to better see the "dusty background" I have also prepared a monochrome image that you can see here:

Click on the image for a larger version.

It may be surprising to see an image with all this dusty appearance in this direction, out of the galactic plane.  To be honest, that is not for me to judge, but this is what came out of my data, and the processing involved was as careful as possible. Data capture wasn't perfect but all the data was taken from the same location, during the same hours on three different nights, and on nights I was very discriminative as to whether  I should capture data for this project or not: all nights displayed an SQM reading of magnitude 21.7 or higher at the zenith at some point during the session, and were all consistently above 21.5 at any time.

Although most of the dust above the background you see in this image is likely from our own galaxy, if you look closely, on top of NGC 4435 (the "eyes"), you may see a thick faint tail moving towards 10-11 o'clock, and that is most likely pulled from that galaxy, not a foreground cloud. The "1" arrow in the image below points to this area. There's also some even fainter strikes visible (barely) going from M86 towards NGC 4435. The lines to the right of the "2" in the image show where these strikes are happening. You will need to go back to the larger version of the above image to better discern them (the green lines in the image below are covering the most visible strikes).

There's also some intergalactic "fluff" - though very diffuse in the image - from M87 to NGC 4461 and NGC 4473. And of course, the well-known interaction between IC 3481 and IC 3483 is clearly visible towards the bottom of the image:

Other than that, I personally cannot tell whether other faint signal is intergalactic, it belongs to our Milky Way or, suffice to say, might be an enhanced artifact during capture or processing.

BACKGROUND MODELING

The hardest part in processing this image was the gradient removal process. It's not that the gradients were complicated or severe. In fact, they were very smooth and subtle, thanks to the dark skies of the DARC Observatory, and if I hadn't gone after the fainter signal, it would have been quite easy to deal with it, but there was a great mix of very light gradients from so many frames, and it took me a lot of trials and analysis until I was convinced I had built a background model that would mainly subtract gradient signal and nothing else (and nothing more). Although it's quite possible that not ALL of the faint but visible data is 100% accurate, I believe most of it is. Here's some of the data and processing involved to "flatten" the master luminance data.

Below you can see the master luminance after being cropped (to remove "bad" edges due to misalignment between frames) and with nothing else done to it but a non-linear stretch tailored to reveal the gradients in the image:

And here you can see a non-linear stretch version of the final background model applied to the image:

As you can see the background model is very smooth and gradual even after a strong stretch - obviously when the background model was subtracted, it was in linear form and visually it looked like a completely dark image.

PROCESSING

The processing of the data did not include at any time any curves transformation, DDP nor selective or masked histogram stretch. All data stretching was done by unmasked and non-selective non-linear histogram adjustments.

More specifically, after the gradient removal, a rather standard process was done to the luminance/lightness data, that mainly included:

1. Slight deconvolution, with masks at three levels: local, global and external. The purpose of the local and global masks was to avoid the Gibbs effect, and the external (lightness-based) mask was used to avoid applying deconvolution to areas low in SNR, and increase the deconvolution effect as the SNR improved.
   
2. A first non-linear unmasked histogram stretch.
3. Masked ACDNR (noise reduction). The lightness-based mask here served the opposite effect of the external mask used for the deconvolution: applying the noise reduction only on areas low in SNR and gradually reduce the effect as the SNR improved.
4. A second non-linear unmasked histogram stretch. This is because after the noise reduction, our histogram has been altered, and so it allows for a new adjustment.
   
5. Masked HDRWT. This is the process that reduced brightness in the larger galaxies and also revealed some of the data and details in them. The lightness-based mask here is also helping avoid ringing.
   
6. A third non-linear unmasked histogram stretch. Again, we readjust the histogram because after the HDRWT process we have a different scenario that allows a new adjustment.
   
7. Slight masked sharpening using wavelets. The lightness-based mask here kept noise from being sharpened.
   
8. Very light masked morphological transform. This process reduced overall presence of the largest stars, bringing them back to their form as they were prior to the last histogram adjustments. A star-based mask is necessary with every morphological transformation process, otherwise we would be applying the morphological changes to structures that shouldn't be affected by it.
   
9. A last histogram adjustment.
10. A last masked Laplacian sharpening.
    

In between some of these processes, I did integrate scaled before/after images via PixelMath at some stages during the processing, to apply a process only so slightly...

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DATE Feb 22,27, March 9, 29, and 30, 2011 PHOTO Exposure: L: 62 x 10', RGB 15x5' each Total: 14.08 hours Focal: 385mm, f/3.6

EQUIPMENT Imaging Scope: FSQ 106 EDX w/Reducer Camera: STL11k Guide Camera: StarShoot Autoguider Mount: EM-400 Miles driven: 1200 (1930 km)

SITE & CONDITIONS DARC Observatory Seeing: Poor Transparency: Very Good SOFTWARE Stacking: PixInsight Processing: PixInsight

This large panorama (a 3x4 mosaic) presents an unusual view that confronts two of the largest galaxies (as seen from Earth) in the night sky: the Andromeda Galaxy (M31) and the Triangulum Galaxy (M33).

The Andromeda Galaxy (top left corner) is a spiral galaxy approximately 2,500,000 light-years away, in the constellation of the same name. The Triangulum Galaxy (bottom right corner) is also a spiral galaxy, at approximately 3 million light years distance in the constellation Triangulum. The bright star in the middle is Mirach, a red giant star about 470 times as luminous as the sun and approximately 200 light years away.

Between them, and invading the entire scene, the often very elusive galactic cirrus clouds can be seen.

Because of the large field of view required to capture these two galaxies in one image, there aren't many images, if any, presenting these two galaxies in the same composition. For that reason, I find this image to be of unusual beauty as well as perhaps a bit thought provoking.

CAPTURING THE DATA

I had to go "at it" several times for several reasons, so in the end the image is a potpourri of data captured in Spain in August, at the DARC Observatory early September, and at the Central Nevada Star Party last weekend. Same scope and camera, but different skies, different exposure times, different amount of subframes, and in one case, even different binning! This mosaic has it all! (BTW I do NOT recommend messing up like that at all - there are "reasons" for all of this, it's just too long of a story :-)

The FOV can be captured - with the FSQ+reducer and the STL11k - as a mosaic of 3x4 (12 frames), but in reality I ended up shooting 26 different frames, each with its LRGBs... This is because once I was done with the data I captured while in Spain, I didn't like the final FOV, so I rotated it, and then I had to capture more frames to "fill up" the holes, then creating seamless frames became very difficult - first because I used different binning and timing, and second because adding frames to an already processed mosaic is often a VERY BAD IDEA. So anyway, I went again and captured more data at the CNSP last weekend to have frames that would match better when building the mosaic. Even with that, some differences can be obvious if you pay attention, but the only way out of it would be to retake the 3x4 frames that make up the FOV and process them all together at once (and I've rather move onto other projects).

GOALS / INTERPRETATION / FINAL FOV

I was hoping Mirach (the star in the center) didn't end up dominating the image so much. Knowing how bright it is and that it was going to end up in the middle of the image, this was wishful thinking, but in the end I think it balances the image somewhat ok - kind of like the mid pivot of a seesaw between the two galaxies. Not quite the effect I was hoping for, which was more the effect of "confronting" these two monster galaxies, with the added challenge that the galaxies are very far apart and the attention may get lost, not sure where to focus, and Mirach constantly becoming the safe harbor of our attention, but I think something can be made out of it. Or maybe I'm reading the image backwards!!

PROCESSING THE GALACTIC CIRRUS

The signal from the galactic cirrus is quite real, not artifacts, not gradients. Now, if we were to capture it deep enough, and in a perfect world, the cirrus should look a lot wispier than in this image. Instead, it looks more like a blur.

To see what I mean, if I do a heavy stretch on the raw data, I can tell the visible cirrus clouds are quite wispy. Look at this crop of one of the areas (top-middle, though the very top in this stretched image doesn't appear in the final image because it was cropped out):

(yes, in the above image you can clearly see one seam :-)

It would be amazing if this kind of detail could be brought to the final "pretty" image, but unfortunately it was very hard to do, for me at least (it's really dim stuff), so I settled with being able to bring the signal above the noise, but heavily blurred. Also I didn't have a lot of data, so I simply didn't have the know-how or the means of better bringing out this signal that was sitting right with the noise.

BTW the blur doesn't come from applying noise reduction but from separating large and small scale structures in the image. The "à trous" wavelets tool in PixInsight however tends to produce this effect when you abuse it, and although perhaps there's a way to preserve some of this appearance by breaking and processing the image in more than 3 scales, I didn't experiment with that and instead went for what I already know how to do: breaking the image in just 2-3 scale layers (wavelet planes), operating on them separately and then adding them back, rescaling. I don't know if what I just said makes sense but I hope to explain it in detail during my presentation at the Advanced Imaging Conference next month (October 2010).

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DATE August and September, 2010 (8 nights total) PHOTO Exposure:3x4 mosaic. Each frame: L: 3 x 15', RGB: 3x3' each, Total for FOV: 14.4 hours Total acquired: 31.2 hours Focal: 385mm, f/3.6

EQUIPMENT Imaging Scope: FSQ 106 EDX w/Reducer Camera: STL11k Guide Camera: StarShoot Autoguider Imaging Scope: EM-400

SITE & CONDITIONS Pinar de Araceli (Spain), DARC Observatory (California), Central Nevada Star Party (Nevada) Seeing: Average Transparency: Excellent SOFTWARE Stacking: DeepSkyStaker Processing: PixInsight & Photoshop

The image you see above is a mosaic of 10 different frames, each of them was acquired with either 5x5 minutes (around the Milky Way) or 5x3-4 minutes for the rest of the sky. The horizons are superimposed from two 3x1' shots, but they match both what was there and the orientation.

It's interesting to note that when I started shooting at the Sagittarius area, the Pleiades weren't even above the horizon, but by the time I've got to that part of the sky, they were already all the way up there.

Now, for the fun part, if you mouse over the image, you will see a digitally altered image of what our eyes could see that night, more or less. If you move the mouse out of the image, you see what the camera could catch. The idea is for those who have never seen the Milky Way from a very dark site, to give them an idea of what it would look like - so maybe they get excited about visiting a dark site and enjoy the night sky!

Have you ever been to a very dark site? I'd like to hear what you think. Do you see the image of the "visual" Milky Way too bright compared to what you see at a very dark site? Too dark? Perhaps the image is too "glowy"? Not enough contrast? Please let me know in the comments below!

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DATE September 18th, 2009 PHOTO Exposure: 10 frames, 5 x 5' each Focal: 17mm, f/4

EQUIPMENT Camera: Canon 40D Guide Camera: StarShoot Autoguider Imaging Scope: EM-400

SITE & CONDITIONS CalStar @ Lake San Antonio, California Seeing: Good Transparency: Good SOFTWARE Stacking: DeepSkyStaker Processing: PixInsight & Photoshop

L: 18x5' & 10x20'
RGB: 10x5' each channel
Total: 7.3 hours

This is a "mouseover" image that allow us to compare the image I took of M31 with the images taken by the Ultraviolet/Optical Telescope aboard NASA's Swift spacecraft of the same object.

First you see the Swift image (not mine!) and if you move your mouse over the image, you can then see the image I took. Moving the mouse in and out of the image you can compare the two images.

I did this to see how the details in the core of my image matched those details - whenever visible - in the Ultraviolet image from the Swift spacecraft.

L: 18x5' & 10x20'
RGB: 10x5' each channel
Total: 7.3 hours

M31 or Andromeda is without a doubt one of the most imaged objects of the sky, and one I knew I had to come back and try to get an image that at least escaped mediocrity. For that reason I focused on capturing an image that would allow me to get as many details as possible from the bright core that otherwise it tends to be either oversaturated or simply too bright to discern any details. I'm very happy with the results - with a fairly modest equipment I was able to scrap details out of the core that other images taken with much more expensive telescopes simply do not show.

I "blinked" several images from other authors - sometimes after a bit of tweaking to reveal the details in the core in such images - to make sure the details I was obtaining were not processing artifacts, and also made this animation:

Please note:

• The quality of the images used in this animation is not great. In particular the "slides" from Tony Hallas and Robert Gendler are at a much lower resolution than the original images from these two fine astrophotographers. The purpose of this animation is not to compare the QUALITY of the images, but only to verify whether the details in my image are real or artifacts - or both.
• Just because a particular image does not show more details in the core than another does NOT mean the image is of a lesser quality, not at all. Different images will have different goals when imaging M31 (or any other target). Again, the only reason to post these images is verify if the details in mine are real, not a competition to see who revealed more or less details.
• To me, the most revealing comparison is the one with the image from Mark Jenkins and Roland Christen, and that's why I placed their "slide" right after the visualization of my image.
• While none of my images are subject to traditional copyright and instead use a Creative Commons License, because this animation uses images subject to copyright by their authors as indicated in the next bullet, copy or reproduction of this animation is not allowed.
• Portion of M31 image from Tony Hallas is Copyright by Tony and Daphne Hallas
  Portion of M31 image from Robert Gendler is Copyright by Robert Gendler
  Portion of M31 image from Vicent Peris and JL Lamadrid is Copyright by Vicent Peris and JL Lamadrid
  Portion of M31 image from from Mark Jenkins and Roland Christen is Copyright by Mark Jenkins and Roland Christen
  
 

The view of the Milky Way at the 2009 Golden State Star Party was amazing. As such, I couldn't stop from taking this 5x5 exposure. ¡Beautiful! What you see is a composition of two images, one taken with the camera on the mount, and another one on a tripod. Despite being a composition, the scene is real in the sense that the image taken with the tripod (from where I used the scope/tent part of the composition) was taken so that the Milky Way was positioned right behind, as if the scope was pointing at it.

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DATE June 22nd, 2009 PHOTO Exposure: 5 x 5' (25 minutes total) Focal: 85mm, f/5.6

EQUIPMENT Camera: Canon 40D Guide Camera: StarShoot Autoguider Imaging Scope: EM-400

SITE & CONDITIONS GSSP @ Adin, California Seeing: Very Good Transparency: Very Good SOFTWARE Stacking: DeepSkyStaker Processing: PixInsight & Photoshop

L: 12x5', RGB: 4x5' each channel
Total: 2 hours

On Saturday April 24th, since I had to wait over 3 hours for Rho Op. to show up, to "kill" time I captured some data from M104 (Sombrero Galaxy) and later some from M63 (not shown in this entry) with the FSQ 1.6x extender. What you see up there is a rotated crop at the original image size.

It was the first time I was using the extender and I only ran one V-curve with FocusMax, so the focusing wasn't great. In addition to that, in the middle of the session a really gusty wind started to blow for over 1 hour. Guiding became a bit jumpy at that time, but surprisingly all subs were usable.

800mm FL - which is what I get with the extender, plus f/8 focal ratio - is not the best focal length for this object, but I figured I'd try it with the FSQ extender to see what came out.

Oh and I didn't frame the object incorrectly. The original field is huge and what you see is a rotated & cropped version. I don't know... I felt like tilting the galaxy and placing it on the side. If you want to see a reduced version of the original stretched luminance, click on the image, and you'll see how little space the galaxy actually occupies in the field of view.

L: 6x5', RGB: 4x5' each channel
Total: 90 minutes

The night of 4/24 while "killing" time waiting for the main target of the night, I got some data from M104 and the galaxy shown here: M63.

It's not a jaw dropping image by all means, but considering it's only 90 minutes of data I think it turned out ok, and considering this kind of target is not ideal for the FSQ, I think it turned out much better than what I expected after seeing the calibrated image.

L: 22x10'
RGB: 5x5' each channel
Total: 3.6 hours

This image is a reprocess done on March 2010 of the original image taken on April 2009

L: 9x10' (bin 1x1)
RGB: 4x5' each (bin 2x2)
Total: 2 1/2 hours

Short session and even shorter time processing the image. I was trying to put in the same field of view both, the Whale galaxy with its classic companion galaxies, as well as the tiny Mice galaxies despite the mice would end up with about the same size as a bright star. If you cannot find the mice, they're around the top-left corner of the large image ;-) Don't look for it in the image above, as it's a crop of the entire feld of view, focusing on the Whale (NGC 4631) and Hockey Stick (NGC 4627) galaxies

This by the way is probably the last time I bin 2x2 for the RGBs. IMO, it's not worth it. Also, despite I spent processing the image not much longer than one hour, I think I over processed the main galaxies a bit more, and left the background a bit too dark.