Mosaics+calibration frames+stitching+StarTools: How?

[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

Many many thanks in advance!!!!

[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

[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

[Carles]

happy to help

let us know how it went

Clear skies

Carles

[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

[kodo]

Perfect Jochen! Many thanks

[Carles]

...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

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.

[kodo]

Hi Carles!

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

Cheers

[Carles]

Hi Carles!

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

Cheers

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

Clear skies!

Carles