DSS vs Siril vs ASTAP

[Carles]

Carles

I have just begun working with Siril as an alternative to DSS this past week, and am also liking what I am seeing so far. It seems that the stack produced by Siril shows a bit more detail than the DSS result. My particular interest is in Siril's capacity to apply background extraction from individual subs before stacking, as I image in a very light-polluted area and gradients are complex and fierce after stacking in DSS. Early results are promising but there is more testing to follow. I will be watching this thread with interest.

Bob

Hi Bob!

Yes I'm quite intrigued so far about the differences.
I stack using the scrip " OSC_Preprocessing"
this is what comes out when stacking
"Integration of 206 images:
15:26:36: Pixel combination ......... average
15:26:36: Normalization ............. additive + scaling
15:26:36: Pixel rejection ........... Winsorized sigma clipping
15:26:36: Rejection parameters ...... low=3.000 high=3.000
15:26:37: Background noise value (channel: #0): 1.181 (1.803e-05)
15:26:37: Background noise value (channel: #1): 1.103 (1.684e-05)
15:26:37: Background noise value (channel: #2): 1.180 (1.800e-05)
15:26:37: Saving FITS: file ../result.fit, 3 layer(s), 6080x4048 pixels"

So it seems it does Normalization, which I don't know to what point is good or not. I think to remember usually not recommended for StarTools but I don't know.
Haven't tested manual stacking parameters , so far only the default script and it looks pretty good to me...

What I don't like much is that it makes quite a lot of "mess" with files, not a mess as in disorganized but rather the amount of storage used!!

I've stacked 206 images, using 33 darks 30 dark flats and 2 master flats (haven't got the original flats since this is from few months back and I'm using different Gain/Offset so didn't see a point on keeping them.

Point is; I've used Drizzle processing this time and the "Process " folder has 82 Gb!!! worth of files! The final file , usually called "Target" <--- FYI, after stacking better change the name or make a copy, as it will overwritte it next stack.. <-- that is using the script, if you do manual I guess you can just select a file name.

So it makes a lot of in termediate files.. even more than ASTAP I think. But this time since it was drizzle, each file was resized so from the original 12mb , each file drizzled is 288mb. Might be a problem depending on the available disk space. But you can always keep emptying this folder after the stack.

I am stacking other old files, and they look better so far as well.

Will keep testing! ^^
If you guys do too, let me know what are the results and or settings used : )

Regards

Carles

[Carles]

Hi everybody,

with my last image I had some problems with the stack generated by DSS. Because of the 80% moon it was difficult for me to seperate the outer parts of M106 from the noisy background. After seeing the processed DSS stack the first conclusion was that it's just stupid to image broadband during a bright moon. But with this thread in mind I had a try with ASTAP and got a much better result.


Stefan

Hi Stefan!

That's an awesome result with full moon!! I was shooting M101 yesterday too to stack with some days back data, and but haven't done it yet since tonight seems to be clear too and want to add some more
And your result encourages me to capture during the moon too! Still, M101 and M106 are "far" from the moon so guess it can be done more safely than, for instance, galaxies in Leo hehe but well, will see!!

Give it a go at Siril too, it is a lot faster than ASTAP! See if the result is any good for you But for now, that ASTAP result looks great! ^^

Carles.

[bigjy989]

I’ll also vote for Siril with the key feature being background gradient removal prior to stacking. Able to remove what should have been an impossible gradient from bortel 5 shooting over a rotating light dome with clouds on an object between 16 and 32 degrees above the horizon. Completely neutralized the gradient such that NO background WIPE was required on the Lum channel. Quite impressed. Additive normalization was used but Startools seemed to have like the input with the Dev home-in auto search stopping at 95% instead of the usual 89% level.

https://www.astrobin.com/0t6hzy/

[Carles]

I’ll also vote for Siril with the key feature being background gradient removal prior to stacking. Able to remove what should have been an impossible gradient from bortel 5 shooting over a rotating light dome with clouds on an object between 16 and 32 degrees above the horizon. Completely neutralized the gradient such that NO background WIPE was required on the Lum channel. Quite impressed. Additive normalization was used but Startools seemed to have like the input with the Dev home-in auto search stopping at 95% instead of the usual 89% level.

https://www.astrobin.com/0t6hzy/

Hi Jonathan, that's an interesting feature I didn't know of! I usually stack using the Scripts, and I am guessing this feature isn't included in the Script itself (nor I don't know how to compile Scripts myself to add it.. ) but sounds very interesting!!

Can you explain to me how does it work and how to activate it?
I'm at Bortle 7 and that would be useful too!
Thank you!

Carles.

[Cheman]

Hi Carles
A script was added for Siril on July 18. Its OSC_Preprocessing_withbackgroundextraction.ssf I have not tried it yet, but you can get it from the Siril script page https://free-astro.org/index.php?title=Siril:scripts
Che

[Carles]

Hi Carles
A script was added for Siril on July 18. Its OSC_Preprocessing_withbackgroundextraction.ssf I have not tried it yet, but you can get it from the Siril script page https://free-astro.org/index.php?title=Siril:scripts
Che

Hi Che!!
that's awesome! Thank you

Will try it straight a way!

Carles.

[Cheman]

I actually just tried it. I dont use darks so I had to modify the script, but it seemed to do a good job
Cheers
Che

[Carles]

Just did one test, but it seems to work well.

how do you modify the scripts? what software do you use and how?

Thanks!

Carles.

[Cheman]

Hi Carles
Open the script file in a text editor. Any line that starts with a #is just a comment. So, since I dont use darks, the script is looking for darks or it will fail. Either delete the lines or put a # on any line that had to do with darks. Except that to calibrate it has a line that uses darks, so I had to change that line to use bias instead. Here is the script after I modified it, you can compare it to the original. ############################################
#
# Script for Siril 1.0
# July 2020
# (C) Cyril Richard
# Preprocessing v1.0
#
########### PREPROCESSING SCRIPT ###########
#
# Script for color camera preprocessing
#
# Needs 4 sets of RAW images in the working
# directory, within 4 directories:
# biases/
# flats/
# darks/
# lights/
#
############################################

requires 0.99.4

# Convert Bias Frames to .fit files
cd biases
convert bias -out=../process
cd ../process

# Stack Bias Frames to bias_stacked.fit
stack bias rej 3 3 -nonorm
cd ..

# Convert Flat Frames to .fit files
cd flats
convert flat -out=../process
cd ../process

# Pre-process Flat Frames
preprocess flat -bias=bias_stacked

# Stack Flat Frames to pp_flat_stacked.fit
stack pp_flat rej 3 3 -norm=mul
cd ..

# Convert Dark Frames to .fit files
#cd darks
#convert dark -out=../process
#cd ../process

# Stack Dark Frames to dark_stacked.fit
#stack dark rej 3 3 -nonorm
#cd ..

# Convert Light Frames to .fit files
cd lights
convert light -out=../process
cd ../process

# Pre-process Light Frames
preprocess light -bias=bias_stacked -flat=pp_flat_stacked -cfa -equalize_cfa -debayer

# Extract linear gradient
seqsubsky pp_light 1

# Align lights
register bkg_pp_light

# Stack calibrated lights to result.fit
stack r_bkg_pp_light rej 3 3 -norm=addscale -output_norm -out=../result

cd ..
close

[Cheman]

I forgot to mention for anyone doing Mono, there is also a script for that.
Also Ivo advises about the use of background extraction here viewtopic.php?f=7&t=2205
Regards
Che