Alignment isn't finding stars

[PetePeterson]

Been working with SC for 6 months now and the align and stack is always a crapshoot. Camera is an ASI2600MC-P. Worked 2 hours on the Perseus Cluster last night with exposures as long as 5 minutes. Played with all the options in the alignment menu, including increasing alignment gain up to 8X. Lots of bright sharp stars but, no joy.

Sometimes align/stack it works, sometimes it doesn't, and sometimes there are many discards for no apparent reason. Gave up on NGC 1275 and went on to a target that had even brighter stars. And after some false starts got align/stack working. Can't remember the align settings offhand.

Any suggestions as to how to make the align work a bit more dependably?

Thanx,

Pete Peterson

[turfpit]

Pete

Some ideas to systematically take control of this:

• On the Alignment tab check Highlight Detected Stars

• Adjust Digital Gain

• Set Minimum Star Width lower

• Is there a Hot Pixel warning?

• Check for Stars Detected messages in the Log tab

I see you got the Digital Gain to 8x which I have found helps.

If you try some of these and report back with settings and outcomes an experienced Live Stacker should be able to give some pointers. Full screen images of capture are helpful.

Dave

[chongo228]

Can you post a photo of the alignment tab during a live stack?

Try adjusting your maximum star size. With 5 min subs you might be exceeding the max star size so SC won't use them for alignment. Adjust settings until your star count is at least 50. I usually shoot for 100 to 200 or more. When I stack that's really all I pay attention to. Make sure your min star size is set so it doesn't count noise. I think mine usually stays around 2 or 4.

[oopfan]

Hi Pete,

I find that alignment lacks good visual feedback. When I have trouble, I switch to the FWHM Focus tool, and play with different levels of black point, etc. At least there you get good feedback. Once you discover something good, then copy those settings into Live Stack alignment.

You are much more patient than I am. I wouldn't have the patience to fiddle with it for 2 hours. You need a Plan B. Go old school and stack in DSS or whatever. Where I live, clear nights are a rarity, so it is best to have a fallback plan of action. Also remember that if you have the frames then you can always play with Live Stack afterwards in the comfort of your home using the Folder Camera, but you need data. If Live doesn't work then passively capture data, old school.

Brian

[PetePeterson]

Thank you very much for the input guys. I'll try all suggestions tonight and report. My understanding of the features in the alignment tab is somewhat crude. Couple of follow up questions before I head out tonight.

STAR COUNT - I've assumed that I'm not detecting enough stars of the requisite brightness, so have set at the minimum 10 guide stars. Do I have this wrong? Should I be setting to 50?

POST PROCESSING - Friends put me on to ImagesPlus and I am using it to stack, etc. But I'd not considered using the Folder Camera.

OTHER: When it's not aligning NO stars will highlight. Just started experimenting with digital gain last night. There was a hot pixel warning and I did set minimum star size a bit higher - possibly from 2 to 6. I'm still to ignorant to utilize/understand the LOG tab. But will try it.

I did play with black levels but don't understand this function or what it accomplishes.

P

[turfpit]

Pete

https://docs.sharpcap.co.uk/3.2/#Alignment%20Tab might be a good read now you have some practical experience. The text is short but it is a 'hard' read.

As Brian mentioned, saving all the frames and replaying using the Virtual camera/Folder Monitor allows you to experiment with Live Stack settings in the comfort of the house. https://docs.sharpcap.co.uk/3.2/#Virtual%20Cameras

Dave

[admin]

Hi,

If the alignment isn't working, have a look in the 'Log' tab of the live stacking area - that will usually contain some information that might point you in the right direction. Most likely though, it's going to be down to not detecting stars properly. As others have pointed out, having a look at the 'Alignment' tab and getting it to highlight the stars that it's detected can help lots. Ideally you will have it detecting about 50 to 200 stars of which it will use 15 to 24 the actual alignment process. The stars that are detected, particularly the brighter ones, should stay consistent from frame to frame rather than jumping around.

Cheers, Robin

[chongo228]

STAR COUNT - I've assumed that I'm not detecting enough stars of the requisite brightness, so have set at the minimum 10 guide stars. Do I have this wrong? Should I be setting to 50?

OTHER: When it's not aligning NO stars will highlight. Just started experimenting with digital gain last night. There was a hot pixel warning and I did set minimum star size a bit higher - possibly from 2 to 6. I'm still to ignorant to utilize/understand the LOG tab. But will try it.

I did play with black levels but don't understand this function or what it accomplishes.

P

Leave the minimum guide stars set to 10 or 15 in the upper left field of the alignment tab. Is your camera cooled?

When I said detected stars I'm talking about the number of stars detected, not used to align. Keep the stars used to align at 15....I've never adjusted this setting. You want SC to detect a good number more than it needs. It will switch which stars it uses to align every frame. Having more than it needs gives you a buffer for bad "seeing", thin clouds, etc.

When I start out all I look at is how many stars it can see. I don't care which ones it's using to align or anything else. Reset everything to factory defaults and start adjusting. Set min to 2 or 4 so you don't pick up hot pixels or noise. I'd probably set my max star width to 14 or so with long exposures....maybe even 12. Your stars will over expose and get fat with longer exposures making them unstable for stacking. You're after the nice, medium size, medium brightness, steady stars. Too faint and they are washed out by seeing or light pollution, Too bright they are bloated and can't be used to align. With 5 minute exposures I'm thinking you are blowing out a lot of stars and they are too fat to be aligned well. Black level and noise reduction will need to be adjsuted to dial it in once star size is set. I don't think I've ever messed with digital gain.

Another tip to save time....Go down to 20 or 30 second exposures and adjust everything until you get 75 or 100 stars and it stars stacking. This way you can learn how the adjustments work without waiting 5 minutes to check. If you get tangled up just reset defaults and start again. Once you're comfortable with the settings go up to however long you want. I've found that I usually/never have to adjust my settings at 30 seconds vs. 1-2 minutes of exposure.

If you don't have any luck post a screen shot.