StarTools

I have 1553 culled lights of NGC 6995 calibrated with bias, darks, flats, no color balancing
etc. as per Ivo's recommened best practices.
Details:
1553 lights x 30 sec, 105 gain, offset 10, -10C, ASI533MC Pro, dithered every frame, Bortle 6
WO GT71, .8x PFlatA6iii reducer/flattener, Optolong L-eNhance
HEQ5 mount
control via KStars/Ekos abort capture set at guide deviation RMS >= 1
dates: July 22,26,27,30,31 / Aug 5,6,15,20,31 / Sept 2
Flats redone as needed with dimmable LED tracing panel atop stretched white cotton membrane (t-shirt).
Calibration, registration, stacking in Siril.
Processed in ST 1.8.512alpha, basic workflow:
Compose (L + synth L R(2xG)B,R(GB(GB) bicolor from OSC/DSLR) loaded red, green and blue channels
Audtodev, Bin 71%, Crop, Wipe, HDR, Sharpen, SVDecon, Color (bicolor), Shrink, SuperStr, Track/NR


I am hoping someone will have a look at my stacked data shared on google drive and let me know
if there is anything suspect. Im not satisfied with the end result and dont know if there is more to improve
on in processing or if my acquisition and calibration fundamentals are off and handicapping my efforts with ST.

Also, is there any benefit to add the data as NB in addition to the r, g, b channels in the Compose module
and then working with NBAccent module ?

Larger version:
https://drive.google.com/file/d/1Am-rCp ... sp=sharing

Final Stack:
https://drive.google.com/file/d/1PpNHMH ... sp=sharing

Sample master flat:
https://drive.google.com/file/d/1dY_bow ... sp=sharing

Master dark:
https://drive.google.com/file/d/1-dy_aC ... sp=sharing

Something doesnt look right to me after initial stretch you can see a sort of bayer matrix pattern i havent seen that in my data ,i would check settings in the FITS settings in siril ,i use ASTAP to stack which seems to work good if you share your data via dropbox i could try stacking in ASTAP just to see what comes out just to compare ,alacant may be able to help with settings in siril .

regards DAVE

thanks for looking. I saw that grid pattern as well but no idea
what would cause it. My Siril process is
- stack bias, no debayer, avg stacking w rejection, no normalization, windsorized sigma clip
- stack darks, no debayer, avg stacking w rejection, no normalization, windsorized sigma clip
- stack flats against master bias, no debayer, avg stacking w rejection, multiplicative normalization, windsorized sigma clip
Im not using flat darks:
calibrated light = (light - masterdark) / masterflat
lights are not debayered until after calibration and then stacked with avg stacking w rejection, no normalization, windsorized sigma clip

What puzzles me is the over abundance of green...even after wipe.
in color module, Max RGB there's a weird pattern too.. This could be the way you did flats?

Don't know about your workflow in Siril, as i use only Script stacking.
but do you need Bias for your camera? I think it doesn't...but no idea.

the only way of getting decent colouring is using the Bicolour preset as you did.
but even though, can see the pattern again. (after Super Struct) Regards

Carles.

I would say the flats are creating issues...
seems very uneven

I tried different types of diffuser materials, different light sources
and settled on the LCD panel + t-shirt. Maybe the ZWO OAG prism
is contributing to uneven falloff or maybe the filter drawer ? Im
re-doing all my master flat/bias/dark calibrated lights from scratch
in Siril to see if I made a blunder somewhere along the way from July to Sept.

What scope are you using? Flats can be a right pain , I find tracing panels to be erroneous as many are lit one edge , I use a El panel with white cotton and an acrylic opaque screen so it’s dim and using flats aid in APT exposure is 3.3 sec , note exposure with el panels need to be over 1 sec so the refresh rate doesn’t cause issues this is using an 8” Newtonian, I use tablet with my 350mm fl refractor.

Regards Dave

scope is William Optics Gran Turismo 71 mm APO . Dew shield is fully extended
always: flats done with 3 layers of white cotton stretched in an embroidery hoop
that fits perfectly around the diameter of the shield and then the LCD trace
panel sits on top of that with a bit of weight to sandwich it flat over the hoop.
The refresh rate isn't the issue: no banding. Ive gone over my Siril process and
Im following the manual exactly (https://siril.org/tutorials/tuto-manual/).
Currently re-calibrating and stacking from scratch 12 hrs of data .... tick tick tick

Hi there,

if your flats are the problem and your process is robust and reproducible, the problem won't disappear. You could stack without applying flats. You will of course see vignetting, but maybe the pattern and the weird coloring will be gone. So you'll know it's actually the flats.

Regards
Stefan

Stefan B wrote: ↑Fri Sep 03, 2021 6:16 am Hi there,

if your flats are the problem and your process is robust and reproducible, the problem won't disappear. You could stack without applying flats. You will of course see vignetting, but maybe the pattern and the weird coloring will be gone. So you'll know it's actually the flats.

Regards
Stefan

<--- I second this!
also

deanST wrote: ↑Fri Sep 03, 2021 5:16 am panel sits on top of that with a bit of weight to sandwich it flat over the hoop.

not sure this is a good idea...unless the weight is equally pushing the panel, and even though
it might get the layers you are using to difuse too tight and thus let more light in the middle to come
through.

As Stefan mentioned, try without flats and see if at least the colour is fine. Is the Bayer matrix correct?
Is normal to see a lot of green before Wipe,but even after wipe seemed like very green to me.

regards

Carles.