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Mosaics+calibration frames+stitching+StarTools: How?

Posted: Fri Jun 30, 2023 7:30 am
by kodo
Hi!

Please let me start by saying I'm a complete newbie/noob when it comes to mosaic(s)! Now having got that out of the way I hope I'll be able to explain what I'm thinking about with regards to my topic...

Say I'd like to create a 2*2 mosaic of the Iris nebula. I create a sequence using N.I.N.A and fire away. I dedicate each panel an equal amount of exposures, say 20 * 180s, resulting in four hours in total for the mosaic BUT how do I handle flats? Say I need to make some adjustments between the panels which will, ultimately, alter the image train - maybe not much but as we all know "not much" is a very relative term when it comes to light!

The way I've been thinking about this is as follows:

Code: Select all

foreach night of exposures
   foreach panel
      take lights (only shooting OSC)
      take calibration frames for each panel
Say I have six nights of data captured, using the process above, would it be correct to:

Code: Select all

foreach panel
   foreach night
      stack light frames together with nightly calibration frames for the panel
   stack the result creating a "super panel" with all stacked nightly data + calibration frames
finally stitch all panels into a mosaic (is Microsoft ICE useful here? Other tools?)
load the mosaic into StarTools
I hope I've been able to describe the way I've been thinking about doing this in a "proper" way process wise - if not please point me in the right direction as this is uncharted terrain for me :bow-yellow: :bow-yellow: :bow-yellow:

Many many thanks in advance!!!!

Re: Mosaics+calibration frames+stitching+StarTools: How?

Posted: Fri Jun 30, 2023 9:10 am
by Carles
Hi, I don't see the problem with flats.
If there were taken on different imaging sessions, the flats should've have been taken as well on each session.

Besides, what I do for stitching is stack each pane separately, open in Startools, autodev, crop stacking artifacts then save the linear data.
And as per stitching itself, ASTAP does pretty good job. I stack images without processing (after being cropped only) then process the image in StarTools as usual, like a single image.

Hope it helps.

Carles

Re: Mosaics+calibration frames+stitching+StarTools: How?

Posted: Fri Jun 30, 2023 9:45 am
by kodo
...which was exactly what I wanted to know. Calibration frames taken for each panel every night. Thanks for clarifying - as I said I'm a newbie. Thanks for the stitching workflow. Very much appreciated :bow-yellow:

Re: Mosaics+calibration frames+stitching+StarTools: How?

Posted: Fri Jun 30, 2023 10:32 am
by Carles
happy to help :)

let us know how it went :D

Clear skies

Carles

Re: Mosaics+calibration frames+stitching+StarTools: How?

Posted: Fri Jun 30, 2023 10:56 am
by hixx
Hi kodo,
the thing with the flats is:
1) If You just intend to calibrate for vignetting, You would just need one set of flats per orientation of Your optical train. In such case, a 3x3 blur of the flat may help reducing noise.

2) Flats are also used to compensate for dust specks, stains etc., though. For this purpose, You'd need a new set of flats for each optical train, session, night and orientation, i.e. for each stack of lights.

I use to split sessions between multiple nights, with T-shirt flats taken in the dawn before (low ISO/gain). You could also take 2 sessions in 1 night, adjust in the middle, taking flats in the evening for 1st setup and the morning after for 2nd setup. Remember to use Flatdarks with same ISO/gain and exposure as the Flats to calibrate properly ( May be shot in the morning after the session)

Such process might sound cumbersome, but take Your time, proper calibration pays out in the end and AP is not a rush....

Clear Skies,
Jochen

Re: Mosaics+calibration frames+stitching+StarTools: How?

Posted: Fri Jun 30, 2023 12:44 pm
by kodo
Perfect Jochen! Many thanks :)

Re: Mosaics+calibration frames+stitching+StarTools: How?

Posted: Fri Jun 30, 2023 3:21 pm
by Carles
kodo wrote: Fri Jun 30, 2023 9:45 am ...which was exactly what I wanted to know. Calibration frames taken for each panel every night. Thanks for clarifying - as I said I'm a newbie. Thanks for the stitching workflow. Very much appreciated :bow-yellow:
Some examples with this workflow

https://www.instagram.com/p/Cj3nVubLoyr/

https://www.instagram.com/p/CmCx85wLx1P/

and
https://www.instagram.com/p/CSMk-0_MVrc/

you can also try to process the images separately and then stitch them with microsoft's ICE , although the problem for me with this is that you have to process both panes in very similar way in order to stitch later.. I prefer the ASTAP and process the whole stitched image. but up to you :) try what's best for you.

I'm sure there are other methods out there and different software too.

Regards,

Carles.

Re: Mosaics+calibration frames+stitching+StarTools: How?

Posted: Wed Jul 05, 2023 3:47 pm
by kodo
Hi Carles!

Many thanks for your reply! I finally got a reason to get an Instagram account :)

Cheers

Re: Mosaics+calibration frames+stitching+StarTools: How?

Posted: Wed Jul 05, 2023 8:26 pm
by Carles
kodo wrote: Wed Jul 05, 2023 3:47 pm Hi Carles!

Many thanks for your reply! I finally got a reason to get an Instagram account :)

Cheers

Great! :D i'll be looking forward to your images! :D

Clear skies!

Carles