Help with M104

[mhamburg]

I doubt it because my rig is under a dome in my observatory, but I wasn't looking for any moisture. What intrigues me (okay, annoys me) is that I might not have the best settings in DSS. Can someone chime in, please?
Michael

[admin]

I think the oddly shaped stars are more of stacking problem, trying to stack stars that have been deformed by coma in some frames but not in others, or some other aberration. It happens unfortunately. I don't see any clipping though...

[Rowland]

I've lost track of which version we are talking about. I sampled the pixel values in the second dropbox link in the first post. The processed stack? I thought.

This is the latest dropbox image. I am presuming a single light sub, uncalibrated. No master flat, no master bias (fixed pattern template), no master dark application? Pixel values are OK.

Can you send me a bias and an uncalibrated dark and uncalibrated flat for this image. Just as they came out of the camera - tiff or png is OK to keep the file size down. I'll just convert the sub to whatever you send. Narrow things down and see what's going on, if that is OK with you?

There is no evidence of weird stars. They look OK. I'm not the expert but I find certain techniques produce better results.

[mhamburg]

DARK_120s_1600iso_+11c_20150419-02h32m33s894ms.jpg (475.48 KiB) Viewed 8068 times

Hi Rowland,
I can only post a resized individual dark frame (120s @iso1600). Unfortunately, I wasn't able to shoot any flats and I usually don't shoot bias either. I hope this helps a bit. Many thanks for your help.
Michael

[Rowland]

Can you upload a dark fits to dropbox, it's near impossible to work with jpeg due to compression.

In hindsight, and while flats are highly desirable, if the only calibration to this image is dark frames, it's likely the problems lie elsewhere than calibration. The application of a stack of darks is optimal for DSLR data, and as far as DSLR images are concerned, the only purpose of bias frames is to calibrate flats - and so, unlikely that calibration truncated the pixels

[mhamburg]

Here is the link to the dark raw file. I hope this helps the analysis.

https://www.dropbox.com/s/i8zpqt4awp569 ... s.CR2?dl=0

[Rowland]

Michael.

It just occured to me that the fts file is a stack. If your patience is not strained to breaking point, a single light .CR2 file is what's needed. Have you compared your light frames to the stack individually? On second look the values in the fts file are not what they should be.

[mhamburg]

Hi
Rowland,
Let me provide a link to a single raw light: https://www.dropbox.com/s/51k6jpi50fxl3 ... s.CR2?dl=0

[Rowland]

Michael.

A quick look before heading off to work. I think the subs are too short, or possibly the focal ratio to high for the subexposure time. The images calibrate quite well but the remaining values are quite low with a very noisy background. At a glance raising the background is probably the key thing here. I imaging that DSS may not have helped and the settings are probably critical. If you can, in DSS, stack your darks separately and then apply the master to your light frames. Don't apply pixel rejection to your darks, if that is the default in DSS and use an average combine, with no noise evaluation, if DSS does that - just a plain unadulterated stack applied to your light frames. See how that goes.

ST will handle the noise very well. But there is not a lot of data in total to start with.

[mhamburg]

I will follow your advice and thanks for the continued support. Michael