Livestack alignment settings

[GSBass]

Thanks Robin, hopefully I’ll have better luck next time I go out

[GSBass]

Robin, is manual selection of stars you see on screen possible in a future version? It just seems that would make this process so much easier to simply draw a box around the stars you want to use for alignment and stacking, especially for us with small sensors where we may be lucky to have three stars in the field of view period,

[admin]

Hi,

manual selection isn't really an option – the code needs to find the stars in each new frame as it arrives and since by default you don't see the individual frames while you are watching the stack build up it doesn't really work out.

Hopefully by seeing a few sample frames that cause problems I can either advise on the right settings or make the necessary changes to allow the code to work more reliably.

Cheers, Robin

[Gamewarden]

I am also new at this. I think some problems regarding the inability of livestacking comes with using cameras of small FOV and sensor size. I use a 6SE with .63 reducer and a ZWO 224 camera and experience trouble with stacking all the time. Perhaps I dont have the most optimum equipment for the job at hand. I have been also told that I will be unable to use any platesolving through SharpCap with this sensor size. True?

Thanks Mark

[admin]

Hi,

since you are using a relatively small camera with a long focal length you will get quite a small field of view – plate solving and live stacking will both be harder than usual to get working because there will be a smaller number of stars than usual in view. For the plate solving, you will need to install far more index files to have a chance of it working.

If you really have no luck getting the live stack alignment working after you have adjusted the star detection settings then the best thing to do is to save a frame ortwo to PNG file and then post them here. Either we can give you some suggestions about settings that will work or use those images to try to make the star detection work better.

Cheers, Robin

[risteon]

Reviving this since I found the conversation here useful.

When live stack alignment is doing star detection, does it use the frame's default histogram when processing the image?

Live a previous reply noted, I can take a single non-stacked frame, stretch it, and see plenty of stars. However, the default histogram may only show a faint few, if any. This observation coming from a ~2000mm f/10 scope, ASI533MC, using smart histogram measurement settings for example.

I like the idea of seeing an image of what the alignment/star detection is using, and maybe providing a way to stretch so that star detection is more apparent like it is with the display histogram stretch.

[admin]

Hi,

currently the best that you have is to turn on the option to highlight the stars - I have on my todo list an improved 'star detection' system which will largely auto-set the options like black level, gain, etc, which I hope will mean this needs far less manual attention in future. The idea of being able to 'see' what the adjustments are doing is a good one, but actually hard to implement unfortunately.

cheers,

Robin

[Ddaniel84]

Hi Robin
I'm using SC 4.0 Beta and have issues with alignment in live stacking. It's mysterious: sometimes it works, sometimes not. Siril succeed with the same pictures, rejecting none of them. The setup F 1280mm (F/R= 6.3) camera is ZWO ASI 294 MC. Exposure time: 277s and Gain 119! I join a print screen. Stars are numerous and well lighted. I tried too the Highlighting option. SC only tell "no more than 3 stars founded. I also test activation of FWHM filter. All of that without success.
SC give no information on what to do. I Also tried to do Noise reduction vary from 0.5 to 1.5, Minimum star width from 2 to 5, also Black level Freshhold from 50 to more (55 - 60..). As shown on one of 2 pictures joined, I also test variation in Stacking sub menu..

Live stacking is very used, it will be fine if it works as well as the whole SC!

Best, Dominique

[clouzot]

Hi Robin
I'm using SC 4.0 Beta and have issues with alignment in live stacking. It's mysterious: sometimes it works, sometimes not. Siril succeed with the same pictures, rejecting none of them. The setup F 1280mm (F/R= 6.3) camera is ZWO ASI 294 MC. Exposure time: 277s and Gain 119! I join a print screen. Stars are numerous and well lighted. I tried too the Highlighting option. SC only tell "no more than 3 stars founded. I also test activation of FWHM filter. All of that without success.
SC give no information on what to do. I Also tried to do Noise reduction vary from 0.5 to 1.5, Minimum star width from 2 to 5, also Black level Freshhold from 50 to more (55 - 60..). As shown on one of 2 pictures joined, I also test variation in Stacking sub menu..

@Daniel:
it would be interesting to see the main histogram, because that's where you'll find important information about the level of the background sky in a single subexposure. This is the level that, in turn, will guide the Alignment/Black level setting. Some software (ASTAP, Siril etc) compute that level automatically, but SC doesn't at the moment, so you'll have to set it by hand.

You may also want to set the Alignment/Digital Gain, but start with the above setting first: it will help separating out stars from the background sky.
Depending on my setup and observing conditions, I may use values as low a 10 or 12, or as high as 60.

Check the highlight detected stars box as you did, then gradually decrease that level, while waiting for 1-2 seconds each time to make sure SC has had enough time to detect stars (look for the numbers at the bottom of the Alignment tab). Then proceed with that setting until you find the sweet spot.

(if you need help in French, you know where to find me )

[Ddaniel84]

Thanks Clouzot
for these precious advises.. and the proposal for french! It's more kind for other reader to stay in english.. even if it's not as easy and precise!
I don't keep the histogram, but will do that next time.
I'll follow your advises concerning hightlighted stars. Can you confirm that you are speaking about Gain parameter in main menu, or is it the one inside the Live stacking sub menu? It xist somewhere a "digital gain". I don't realise the importance of threshold and min star size. The problem is that SC don't give some precise information about the reasons of non alignment.
Merci!
Dominique