So here I stand at the top of the abyss looking down. Got myself a 600D for birthday/christmas now trying some widefield shots in the direction of Lemmon.
I have 15 subs but when I stack them in DSS it just doesn't look right.
I have 15 x 15sec, f5.6, ISO3200.
Attached is one of the original frames, output from DSS and my result after doing things to it.
Doesn't look too bad to me, you've got the SMC and 47-Tuc and the comet in that pic.... image scale/focal length is on the short side of course, but a good image nonetheless.....
Are you shooting from a light polluted area?
If so this would account for the redish background.
I find auto white balance is the best, at least for the 1100D, this may help if your not already setting to this.
Doesn't look too bad to me, you've got the SMC and 47-Tuc and the comet in that pic.... image scale/focal length is on the short side of course, but a good image nonetheless.....
Thanks Lee. Just working with the 18-55 kit lens for now so yes fl is less than ideal.
Quote:
Originally Posted by tilbrook@rbe.ne
Hi Michael!
Are you shooting from a light polluted area?
If so this would account for the redish background.
I find auto white balance is the best, at least for the 1100D, this may help if your not already setting to this.
Otherwise it's actually not a bad result.
Cheers,
Justin.
Yes, shooting from my backyard in the middle of the burbs. Not doing myself any favours there, a short drive may be in order if I can escape one night.
White balance was set to daylight, I could give auto a try.
Should I be using a longer exposure for this? Although from my testing that just pickes up too much sky glow at home.
You could push out 20 sec, but it may be worth the drive for darker skies.
If You shoot at 18mm go for 30 sec, won't be a problem around the SCP.
Take as many subs as you can get, and some darks frames.
Should I be using a longer exposure for this? Although from my testing that just pickes up too much sky glow at home.
Sky glow can mostly be removed by adjusting the black point of the histogram while processing.
I usually try to expose as long as I can before the white end of the histogram begins to clip. I have read it is best to shoot with a peak around 1/4 to 1/3 of the way from the left of the histogram, but I have gone 1/2 and 2/3 of the way before without clipping the highlights (overexposed, image shifting off the right side of the histogram.)
See link: http://www.astropix.com/HTML/I_ASTROP/QUICK2.HTM
f5.6 is a struggle with such short subs, do you have another lens?
I'm getting great results with 30s at f2.8 and f1.8.
Even on a 35mm lens, 30s is fine.
I have given it a crack in DSS and have posted some settings for you that I used.
First of all, I am not in any way a guru when it comes to DSLR processing, plus, my PC has conniptions when I try to use Startools on such large files.
That said, there IS some data there, which I have stacked and adjusted in DSS 3.3.3.47 beta. I have attached the settings pics as well as the settings files for you to try.
One of the "dark arts" things that I do when I get an output from DSS which more often than not looks almost white, is I adjust the colour, luminance and saturation sliders using some tricks I have learnt.
Basically, first thing I do is on the colour RGB page. (first attachment)
What you want to do is STRETCH the histogram to be as WIDE as possible on the display, rather than having 3 narrow mountains, for each colour, you want 3 WIDE hills. As wide as you can make them.
1) Slide the RED black point slider to the RIGHT which moves the RED histogram LEFT on the screen display at the bottom. What you want to do is watch the screen till the RED hump CLIPS which shows up as a vertical SPIKE on the left of the hump. THEN, back it off one notch till the spike disappears. This should mean the red channel is as WIDE as it can be.
2) Repeat, using the black point slider ONLY on the Green and Blue channels until all histograms are stretched as wide as they can go without the left side SPIKE appearing. Hopefully, they will all be lined up and all the same(ish) shape and vertical size. (see the first attachment again)
3) Now, adjust the MIDDLE grey point slider on each channel until they all line up with each other and sit on top of each other, as close as you can make them, as sometimes, each channel has a slightly different curve shape.
4) Now click on the APPLY button before moving to the LUMINANCE TAB. The picture will now "paint" itself with blocks, using the new colour settings. If the Luminance CURVE is off to the right of the colour humps, then it will be blackish and too dark. Now we are going to adjust the LUMINANCE.
5) First thing to do is grab the BOTTOM slider of the MIDTONE section and slide it left or right to place the main bottom part of the curve OVER the colour humps. (see my second attachment). With these sliders, simply click and hold while sliding left or right to move the corresponding section. The BOTTOM slider adjusts the "bias" or amount, and the top slider adjusts the ANGLE of either the Dark, grey or white parts of the Luminance curve.
6) I normally set the MIDTONES slider as shown and then play with the dark and light sliders until the curve looks as per my second attachment. When you have it NICE AND SMOOTH, it should look good. Keep clicking APPLY (and then wait) to repaint the screen with the new settings.
7) (TIP) If the core (of galaxies, or nebulae) is getting blown out, make the HIGHLIGHTS part of the curve LOWER from the top, either by adjusting the angle or bias of the HIGHLIGHTS slider, OR by adjusting the ANGLE slider of the MIDTONES until the S curve FLATTENS out (or leans over to the right) rather than being steeper.
8) Best thing to do initially is to get a "feel" for the luminance curve. Firstly, make it look like my one, a nice smooth, not too steep S. Then, once you have that shape, PLAY with the MIDTONES bottom slider and keep clicking APPLY until you are happy with the adjustment. If you screw it up too much, use the Undo and Redo sliders next to the settings wheel at the bottom.
9) Once I am happy (I take a while on the luminance to PLAY with it for a while), with the luminance curve, I click on the saturation slider and kick it generally to 20%. Adjust this to your taste and click apply, I normally use the range of 15% to 25% depending on the target and camera, but 20% is a good place to try for my DSLR and my Atik cameras. This will restore the star colours and the nebula/galaxy colours etc. Again, adjust this to SUIT the stack you have on the screen.
9) IMPORTANT: SAVE the settings once you are happy with them, or at least have them almost right. Click on the yellow gear wheel and give the settings a meaningful name, so you can come back to that objects settings (they will ALL be different, for different objects and stacks). (Third Attachment). You will see all my recent targets are in my pic, this allows me to reprocess in SECONDS after I do a change in the stacking or file list later.
10) Once you have a more usable (and in most cases if you have nice SNR), more visible, stretched stack output, save the file, using "Save picture to file" on the menu. Save it as TIFF for later processing with Startools, Nebulosity, PS etc.
11) I have added an attachment (4) of the settings I used for these Lemmon pics, I pretty much use Median for all the Stacking Modes for lights, darks, bias etc. unless DSS recommends me to use something else because I have longer subs or something like that. To start with, simply use Median for now as it seems to work the most times. Also, I often default to "Per Channel Background calibration" for both DSLR and CCD pics as it seems to give a better result on the channels (unless I use my CLS filter).
12) I should mention that I set the RAW/FITS DDP settings to DSLR auto white balance and either Bilinear or AHD debayering. Click on an individual sub and then adjust the screen stretch (top right) to check the subject and SEE if the DSLR debayering gives you a COLOUR photo. It should. If not, click on the FITS tab and tick it, then select the correct DSLR or debayer matrix for your camera, go back to the file list, click on the sub and WAIT until it decodes it and the banner on the top of the screen goes BLUE, rinse and repeat with the screen stretch slider, until you can SEE your subexposure in colour and with contrast. (attachment 5).
13) Finally, make sure that you save the FILE LIST and give it a meaningful name, so you can literally start DSS later, open a file list with all the lights, darks and bias etc, load the DSS settings, click register stacked pics and then load the adjustments in the histogram and VOILA, reprocess in minutes, not hours.....hopefully, depending on the speed of your PC and the size of the file stack.
I have attached (6) the output of DSS I got using these methods. It shows some pretty GNARLY light pollution or vignetting in the lower half of the screen around Lemmon, BUT ITS THERE!. Also, the high ISO and I assume high ambient temperature, caused LOTS of thermal noise to show up. You might want to try some longer subs if you can.
I have also attached the DSS settings file for you to load into DSS 3.3.3.47 beta (should work with other versions too). Just change the name to remove the .txt off the end so DSS can see it and load it.
Hope this helps you (and anyone else who may be interested) get some better results out of DSS. You only need to go back in time on my threads to see how cranky I got with the whole deal, especially with my thermonuclear DSLR and high temperature, Light Pollution, vignetting etc.
One blessing is that my little Atik is only 1.3Mp so the files are TINY in comparison to the DSLR Raws and their resultant HUGE stacks......so I can play around with the settings HEAPS now, without getting super annoyed with how long it takes and then find its all crap.
Good luck, I havent tried to process this too much as its only 4 mins and pretty noisy with that large gradient on the bottom (I have attached my output below as a JPEG, you will need more data and exposures with less noise to bring up the SNR with such a wide field.
Whew, hope this helps. Sorry if I have forgotten anything.
Michael, I'm struggling with Lemmon too. I'm imaging through a 10" SCT so have different issues (I might post some of my failed attempts t cheer you up :-) ) - but persevere. We'll nail it before it leaves; it's worth it.
Chris, that was an absolutely AWESOME DSS processing tutorial. Thanks mate, I have been looking for some of those sort of tips for a while.
Wow, thanks Chris for the very detailed description. I'll have to read through it a few times I think to take it all in. I think your post could be turned into an article with almost no changes.
Michael, I'm struggling with Lemmon too. I'm imaging through a 10" SCT so have different issues (I might post some of my failed attempts t cheer you up :-) ) - but persevere. We'll nail it before it leaves; it's worth it.
Chris, that was an absolutely AWESOME DSS processing tutorial. Thanks mate, I have been looking for some of those sort of tips for a while.
lol, i'm not that upset by it. We all have to start somewhere and there's a lot to learn.
You should put yours up, there are lots of helpful people here and if you don't ask...
I downloaded DSS 3.3.3.47 beta and loaded your settings file and straight away that made a huge difference to the result.
I followed your instructions for the colour and luminance adjustments and I can see now it is very sensitive. It also shows me how the finer detail which you can sort of see is overwhelmed by the noise.
I did a final bit of PP and here is the result. Better than the first one but like you say it needs more data.
Michael, I'm struggling with Lemmon too. I'm imaging through a 10" SCT so have different issues (I might post some of my failed attempts t cheer you up :-) ) - but persevere. We'll nail it before it leaves; it's worth it.
Chris, that was an absolutely AWESOME DSS processing tutorial. Thanks mate, I have been looking for some of those sort of tips for a while.
You're very welcome Jon, it was a bit of an essay, but I'm glad you can follow it. I try to put as much info as I can so it can be reproduced easily. Comes from writing so many IT and telephone instruction manuals :-) happy to help as it frustrated the crap out of me for a while....
Quote:
Originally Posted by michaellxv
Wow, thanks Chris for the very detailed description. I'll have to read through it a few times I think to take it all in. I think your post could be turned into an article with almost no changes.
Cheers Michael, such praise! I thought it might take a bit to absorb.I was happy to share some DSS secrets.
Quote:
Originally Posted by michaellxv
I downloaded DSS 3.3.3.47 beta and loaded your settings file and straight away that made a huge difference to the result.
I followed your instructions for the colour and luminance adjustments and I can see now it is very sensitive. It also shows me how the finer detail which you can sort of see is overwhelmed by the noise.
I did a final bit of PP and here is the result. Better than the first one but like you say it needs more data.
Thanks again.
Look at YOU! processing in dss like a champ now! Yep, you need some more signal to play with. Try some other targets to practice the processing in dss, I'm amazed at what comes out now after stacking and tweaking, I only do minor work in Photoshop and star tools now, it's renewed my enthusiasm.
I thought it might take a bit to absorb.I was happy to share some DSS secrets.
processing in dss like a champ now! Yep, you need some more signal to play with. Try some other targets to practice the processing in dss, I'm amazed at what comes out now after stacking and tweaking, I only do minor work in Photoshop and star tools now, it's renewed my enthusiasm.
