non-LiveStack dithering

Discussion of using SharpCap for Deep Sky Imaging
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psy1280
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non-LiveStack dithering

#1

Post by psy1280 »

I'd like to make captures and stack later with APP. I'm familiar with using dithering when Live Stacking, but can SharpCap dither when just capturing images? Or do I need to do this through LiveStacking and use the raw images for later stacking?

Thanks much,
Joe
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Re: non-LiveStack dithering

#2

Post by admin »

Hi Joe,

you can dither while capturing, but you must use SharpCap 4.0 and either the sequencer or sequence planner - see

https://docs.sharpcap.co.uk/4.0/#!2!Dee ... %20Planner
https://docs.sharpcap.co.uk/4.0/#The%20 ... e%20Editor

cheers,

Robin
psy1280
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Re: non-LiveStack dithering

#3

Post by psy1280 »

Thank you Robin,
Just to clarify, if I use livestack (which I'm already quite familiar) without flats or bias applied and just saved the raw files...would this be all I need in order to dither and then stack later in APP where I would apply both flats and bias?

Thanks in advance,
Joe
chongo228
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Re: non-LiveStack dithering

#4

Post by chongo228 »

psy1280 wrote: Thu Sep 02, 2021 9:46 pm Thank you Robin,
Just to clarify, if I use livestack (which I'm already quite familiar) without flats or bias applied and just saved the raw files...would this be all I need in order to dither and then stack later in APP where I would apply both flats and bias?

Thanks in advance,
Joe
You are correct, Just use live stack and save the raw files without any processing and you can process them later. If you need to save computer power just uncheck the align button and it won't stack images as they roll in. Make sure you select Save except when Paused/Dither under the "Raw Frames" drop down menu. I prefer to save any non-dither frame and sort them out later. In other options SC will discard any that are below the stacking threshold.

If you're still manually focus you can watch the FWHM filter and know when focus is drifting out. Manual focus would take me a while and I'd use this to avoid wasting time focusing too often in the past. Auto-focus is much faster so I don't use it anymore but it's a good tool to have.
psy1280
Posts: 208
Joined: Wed Oct 24, 2018 4:52 pm

Re: non-LiveStack dithering

#5

Post by psy1280 »

Chongo,
Thank you so much for your explanations. If you don't mind, I'd like clarify the following:

1.) You say to 'Save except when paused/dither'...I know I've seen this somewhere...you said under the Raw Frames drop down menu...is this in the LiveStacking area/menu?
2.) Why would you want to save non-dithered frames?
3.) To be clear, if I move the sliders during LiveStacking (just to play around a bit), this will NOT effect the raw files to be stacked later? Saying this differently, the LiveStacking manipulations are independent of the raw files. Is that right?
4. Yes, I manually focus. I've just started using the FWHM filter. I thought if I set the threshold to a certain acceptable level, then anything that drifts beyond that would simply not be saved. Am I wrong about this? Do you do autofocus within SharpCap?

Thanks again for all the valued help,
Joe
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Re: non-LiveStack dithering

#6

Post by admin »

Hi Joe,

1) You are looking for the 'Raw Frames' dropdown - see https://docs.sharpcap.co.uk/4.0/#Left%20Panel

2) 'Save except when paused/dithering' will save the frames captured from the camera, but not those captured when dithering is happening or when live stacking is paused. This is usually a good choice as it saves all the frames that you would expect to be useful in later restacking.

3) That's correct - mess around with the sliders as much as you like - the raw frames saved are not affected by them (they also do not have dark/flat etc applied to them). They are the data exactly as it comes from the camera to SharpCap

4) This depends on the 'Raw Frames' dropdown setting. If you select 'Save except when paused/dithering' then frames that have a higher FWHM than your threshold *will* get saved. If you select 'Save Stacked' then only frames added to the stack will get saved, meaning that the bad FWHM frames will not be saved.

cheers,

Robin
psy1280
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Re: non-LiveStack dithering

#7

Post by psy1280 »

Robin,
Thanks for clarifying all this...If I may, one further clarification: So, if I apply a flat +bias + dark, these will ONLY affect the LiveStacking. The raw data is not affected by these? I just want to be sure before heading out tonight.

Thank you,
Joe
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Re: non-LiveStack dithering

#8

Post by admin »

Hi Joe,

sorry for the delay replying - I was away Friday PM and Saturday. Yes, the affect of darks/flats is only on the live stack data when used while live stacking (you cannot use Bias frames in SharpCap itself).

cheers,

Robin
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