Eliminating white balancing when using DSS

Questions and answers about processing in StarTools and how to accomplish certain tasks.

Re: Eliminating white balancing when using DSS

Postby admin » Sat Nov 19, 2016 2:11 am

ecuador wrote:I still can't see an advantage of going the longer TIFF route to be able to use the "not whitebalanced" option in ST


In this case, me neither! :think:

Thanks for uploading the median stacks.

It definitely looks like something funky is going on during stacking - the data simply isn't as deep as the "regular" non-pre-debayered stack. No question.

I don't know what the cause of that could be. I assume you pre-debayered any calibration frames as well, right?

I'm not sure if related, but by coincidence, I noticed a faint, but noticeable cross-hatch pattern in the AutosaveTIFFmedian data on 1st AutoDev, which happened to scale the image at 26% to fit the image (intentional aliasing is one of the features of the scaling algorithm in StarTools). StarTools showing a pattern like this betrays an underlying pattern (repeating artefact) at a different frequency. It's possible that it is not significant, but it's not present in AutosaveRAWmedian and I thought I'd mention it;

crosshatch.jpg
crosshatch.jpg (425.27 KiB) Viewed 314 times


As a sanity check, I did two processing runs of AutosaveTIFFmedian with the exact same parameters + settings, however with the only difference choosing between the two different options when loading/activating Tracking. As expected, the option that weighs channel precision as 1:2:1 for R:G:B (because a camera with a Bayer matrix records 2x more green samples) rather than 1:1:1, provides a tiny (tiny!) bit more small detail and definition (and has the nice side effect of killing more red hot pixels than it emphasises green hot pixels). With the data quite noisy the improvement is really marginal and you'd have to look closely while before/after toggling to appreciate it though...
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Re: Eliminating white balancing when using DSS

Postby ecuador » Sat Nov 19, 2016 1:22 pm

Yes I did the same DCRAW command on all calibration frames, weird, huh? I'll do the process again. This time I'll use an M31 set, DSS 3.3.4 (I thought 3.3.6 gave a bit better result processing RAW, but perhaps it has bugs and that's why it was pulled, so I'll go back to 3.3.4) and I'll use your command "-r 1 1 1 1 -4 -T -S 32767 -k 0 -o 0 -q 0 -t 0" instead of "-r 1 1 1 1 -4 -T -o 0 -q 0 -t 0" on all frames (it did not seem to be better with the Heart Nebula set, but perhaps I was too hasty in my judgement). I'll keep it at median for light and calibration frames.
I am preparing a tutorial for my local club and everyone doing astrophotography is using a DSLR under the same skies as I do, so the noise situation will be similar, hence I am testing with these sample sets to make sure I'll give the best advice. If I can get an advantage with the TIFF process, I will put it in the tutorial for people who want to do it. And I'll follow it myself of course ;)

DSS has at times given me some funky results so it is a bit "temperamental", perhaps a different set will make a difference. The same (being "temperamental") is true about a few other astro-software (registax comes to mind immediately), so it seems they are written by people who know about algorithms, but are not software engineers. On the other hand, StarTools shows that the developer knows about software engineering in addition to image processing and I have said this before but I consider it silly that the 1.4 version is still marked as "alpha". Leave it at "beta" if you feel you haven't decided on the feature set, but "alpha" at such maturity is very old school IMHO ;)
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Re: Eliminating white balancing when using DSS

Postby ecuador » Sat Nov 19, 2016 7:48 pm

Hmm, I don't know. Here is the TIFF and RAW-processed of M31: https://drive.google.com/open?id=0B1c3jz2L9HfgNXRJTW5QZWJ6Qkk.
On the one hand, the TIFF seems to have some easier to handle noise. On the other hand, when I try to get up to the faint edge of M31 and then make that edge more prominent e.g. with "moderate" or "heavy" life, the RAW gives me more of what I want (more cowbell anyone?). Anyone feels like looking at them, I'd welcome a comment.

Don't mind the weird purple artifact on the left, it appeared in both the sessions I tried using the TRF-2008 reducer, so it is probably from that. Strange though, a TeleVue lens causing reflections, but I've never seen it without that reducer.

On an unrelated note, how come the autodevelop that wipe shows temporarily, gives a much more proper development than the actual autodevelop without a ROI? It happens often for me.
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Re: Eliminating white balancing when using DSS

Postby ChrisLX200 » Sat Nov 19, 2016 11:08 pm

ecuador wrote:...
Don't mind the weird purple artifact on the left, it appeared in both the sessions I tried using the TRF-2008 reducer, so it is probably from that. Strange though, a TeleVue lens causing reflections, but I've never seen it without that reducer.


Do you have a LP filter between the reducer and the camera? I found I could not use my IDAS filter together with a reducer (Televue NP127is and Televue 0.8x reducer) due to reflections. The filter was the source of the reflections and the reducer is fine without it.

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Re: Eliminating white balancing when using DSS

Postby ecuador » Sun Nov 20, 2016 9:53 am

ChrisLX200 wrote:Do you have a LP filter between the reducer and the camera? I found I could not use my IDAS filter together with a reducer (Televue NP127is and Televue 0.8x reducer) due to reflections. The filter was the source of the reflections and the reducer is fine without it.

ChrisH


Yep, I did have a CLS filter between the reducer and the camera. That's unfortunate if I can't use it there - it works fine if it is between the camera and the field flattener. Thanks for the tip, I have only used the reducer on one session, it's been dreadful weather since then, so I haven't been able to do any testing.
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