Post Processing blues!!! Ready to call 911

[bradn801]

There has to be an easier way to post process an image after you stack a photo. I took several photos of the Orion Nebula in RAW format following the instructions given by the Deep Sky Stacker site. Let the software do its thing and the end result is a very dark photo with zero color. So now I move on to the Post Processing adding the color levels and I have spent well over 8-10 hours fidgeting here and there with colors and no matter what I do I cannot make the colors even close to what the picture would look like if I didn’t stack it and just used 1 photo and convert it to .jpg.

I have tried using the RGB levels in DSS, I have tried Paint Shop Pro, and I have tried GIMP. Is there anybody who can steer me in the right direction? I know the nebulosity is there and the colors are there I just cant get them to come out with a desirable outcome.

Thanks for your help

Brad

[Adrena1in]

Afraid I can't help, but from my own past experience I've also had huge problems with RAWs. The finished stack never looks anywhere near as good as when I stack JPGs. Mine have always been really dark too, and have required so much extra PP that the quality just goes down the toilet. I don't take RAWs anymore.

I know it's just me, and the way I'm doing it, but I've never seen a good tutorial as it seems a lot harder than using JPGs.

[chris.bailey]

If it was easy it would be no fun and everyone would be doing it. DSS is a fantastic tool (considering its free) and a lot easier to use than something like Maxim DL. I am using it myself right now for processing data I got last night of...M42. I always process RAW if using a DSLR and FITS if using a CCD.

The Autosave output from DSS is a linear 32 bit Tiff. It will look dark and colourless but WILL have a higher signal to noise ratio than a single image and WILL withstand much higher levels of subsequent processing without breaking up. The stacked image is almost the same as the sum of the exposure time so a 10 x 1 minute stack is roughly similar to a single 10 minute exposure (there are different opinions on this but for our purposes its good enough). Dont try and do any post processing in DSS, its not what its good at AT ALL.

You now have a lovely 32 bit data image so what to do with it? My choice is to save out from DSS as a 32 bit -rational FITS file and then use the Histogram function in PixInsight (I have the core edition but there is a free to download earlier version) to carry out a Stretch. Essentially this remaps all the midtones in the image without clipping any highlights or shadows. The result SHOULD be an appearance of all that lovely Nebulosity. The beauty of PixInsight is that uit works throughout with 32 bit data and the Histogram tool is far more controllable that any others I have seen. PixInsight also has some very powerful tools for PP aimed specifically at Astro Images. Lots of tutorials on their website but it is initially a bit daunting, make that a lot daunting.

If you want some good tutorials on using DSS and then Photoshop I suggest you head over to http://ukastroimaging.co.uk/forums/index.php. More stuff on there than you can shake a stick at and a member who goes by the handle of dciobota has written several bookworthy ones. A generally friendly lot if you have abny queries.

If I get some decent output from my M42 later this evening I will post up a bit more info on post processing it.

[Adrena1in]

I wonder if it's Adobe Photoshop that's part of my problem...I think I read it can't handle 32-bit...not sure... I certianly never use DSS for PP. I just save the TIFF and head over to PS with it.

[bradn801]

Thanks so much for the input and suggetion. I will give Pixinsight a shot when I get home tonight. I hope it produces what I know I captured on the camera. thanks again and I look forward to showing you what the outcome is and I also look forward to your stacking effort.

Brad

[troypiggo]

What exposures did you take and at what settings?

If you're having no luck in photoshop, and you typically use that for processing "normal" photos, I doubt using gimp will change/improve that.

PS - this is the "photo sharing" forum. Probably more on topic in the "discuss astro" forum. ;)

[chris.bailey]

http://www.pbase.com/chris_bailey/image/108873090.jpg ... is straight out of DSS

http://www.pbase.com/chris_bailey/image/108873093.jpg ...is the same file after a simple histogram stretch in PixInsight.

There is lots more in it still but it is then down to a matter of taste i.e.

http://www.pbase.com/chris_bailey/image/108862621.jpg ... after Background Modelling and a bit of HDR Wavelets in PixInsight. Needs Flat frames really and a bit more work in noise reduction but Stage 1 to Stage 3 is about 30 minutes work.

[chris.bailey]

PS - this is the "photo sharing" forum. Probably more on topic in the "discuss astro" forum. ;)

Wow. Been here for years and did not even know that existed. :-)

[bradn801]

Now I am excited that is exactly the outcome I am looking for. I am leaving work early to go attempt! Hope to post in a few hours my results.

Thanks again

Brad

[troypiggo]

Chris - great work, but quick question. The first 2 images appear mirrored about the horizontal from the last one. Is that intentional? Why? Oh, wait... not shot prime focus and so camera captured mirrored image? Sorry for dumb question, I'm new to all this.

[chris.bailey]

Chris - great work, but quick question. The first 2 images appear mirrored about the horizontal from the last one. Is that intentional? Why? Oh, wait... not shot prime focus and so camera captured mirrored image? Sorry for dumb question, I'm new to all this.

Actually that is not the reason. Pixinsight carries out the mirroring (something to do with the way it reads FITS files) which I always correct as the last step of the process.

[chris.bailey]

As a tip for DSS or indeed any other programme that stacks multiple images, do be ruthless with your culling of errant frames. Out of 30 or so frames there will always be some that dont come up to standard (plane trails, satellite trails, kick of the tripod, kids shining torches at the business end of the scope). Boot them out of the stack (the frames that is, not the kids)! The Score value in DSS does not mean much per se but is a good indicator of a frame that is below the quality of the rest.

[bradn801]

Ok Mr. Bailey. Do you have any tips or comments for PixInsight? I attempted to post process my stacked photo last night and while PixInsight is more powerful by a long shot than DSS for PP, I am still having trouble. I know it’s a lot to ask but could you tell me your process for your shot of M42? I realize that my picture isn’t going to be as good as yours but this PP is kicking my butt. This is getting very frustrating. Any guidance you can give is GREATLY appreciated.

Thanks

Brad

[chris.bailey]

Yes PixInsight does have a BIG learning curve. If you open your image in Pixinsight just try and do a Histogram stretch (Process>Histogram). Drag the LH cursor to the start of the curve and move the midtone cursor to just inside the peak. I only have the newer version here at home try this tutorial for the LE version
http://www.davesastro.co.uk/techniques/pixinsight_tutorial/pi_le_tut2.html

[chris.bailey]

Here you go. PixInsight LE (Free to download).

http://www.pbase.com/chris_bailey/image/108920734.jpg

Process>Transfer Curves>Histogram

http://www.pbase.com/chris_bailey/image/108920735.jpg

http://www.pbase.com/chris_bailey/image/108920736.jpg

Lots you can play with from there but i always do that quick post process with every image I stack to get a quick a dirty view of what I have got. I then plan a processing strategy a little more. The above gets you most of the way there in one step though.

[bradn801]

I guess I am either an idiot or I dont have this tool but how did you select the area around the nebula? I cant weem to find any tools that let you pick an area on the picture? Thanks for the posts by the way Mr. Bailey I apprecaite it more than you know.

Brad

[chris.bailey]

Its not selective, it acts on the whole picture. There is a box marked R/T that gives you a real time preview of what you have done, is that what you mean? You can also zoom in to the histogram in PixInsight. Note that it is quite an extreme Stretch/Mid Tones Transfer as most of the data is in a very narrow portion of the available brightness values.

~chris~

[bradn801]

Yeah I knew about the R/T It just looks like that you were able to select an area that you wanted to edit in your first picture with the histogram. That bubble looking outline in the preview. None of the black outside of it seems to be affected. Everytime I amke a change the whole picture is altered. I noticed when you zoom in with the histogram I assume its in the right corner where teh 1:1 button is..it doesnt let you make changes at the zoomed in level. I dunno ......this is either too sensitve for me or I am a complete moron. I wouldnt think PP would be this difficult to even get a moderate improvement.

Brad

[chris.bailey]

Brad, the bubble is just the fact that the realtime preview is bubble like is due to the fact that it is a low res representation (we are talking a lot of data in one of these images, 60gb Fits files in my case) made worse still by jpg artefacts for posting here. The changes made do effect the whole image. I may well have a darker background than you due to use of a light pollution filter or less light pollution. Just means you wont be able to stretch quite as far. The background should NOT be black. This whole area of Orion is filled with faint nebulosity so even at a very dark site, the background will not be black, probably a faint red but dark grey is good.

You can zoom in (yes the 1:1) and make changes, it is very senstive at 1:1. Remember the LH slider affects the black point, dont move it further than the bottom of the steep part of the histogram. Then move the mid tone carat to the left to somewhere just inside the right hand side of the histogram.

[bradn801]

Well I am getting closer! I have spent more time on this than I did on my resume. Right direction???? Any guidance?

Thanks Chris

Brad

[chris.bailey]

Hoorah. Black point looks a little clipped...aim for a dark grey background not black or have you done it to hide general noise in the background. How many subs in that and what length? Did you take some darks?

[chris.bailey]

Also try running DSS again with the Per Channel Background Calibration option checked.