Alignment error in Live stacking

[chongo228]

I'm pretty experienced with SharpCap and couldn't figure this out. I adjusted and readjusted settings in the alignment tab of live stacking and never got one frame to stack. Attached is a screen shot showing the log.


I could have played with the settings all night until I figured it out but It won't save the unstacked frames. Please change this....The frames were all good quality and I lost 45min worth until I gave up and went to the standard capture. If it saved the unstacked frames I'd have stayed on the problem until I figured it out. In a past post I made you said you would consider changing this. Attached is my log

TMB92
ASI1600mm-c
Shooting though Ha filter

[turfpit]

chongo

The log says "detected 1 star, less than 3 stars found in the frame, alignment failed". From the manual "The absolute minimum requirement is 3 stars detected" https://docs.sharpcap.co.uk/3.2/#Alignment%20Tab .

My next step would be to go to the Alignment tab and check Highlight Detected Stars
to find out what is happening. pay particular attention to the hot pixel warning.

highlight-detected-stars.JPG (101.78 KiB) Viewed 1927 times

I adjusted and readjusted settings in the alignment tab of live stacking

Some detail of the settings you adjusted would be useful to help with this. The necessary parameters are described in the manual link above, together with suggestions for what to adjust in the event of alignment failure. Also posting a camera settings capture file would help. For example, you are using an Ha filter, so what exposure/gain is being used? Has live stacking with an Ha filter ever worked for you or is this a first try?

To reset the Live Stack settings to installation defaults, click the Reset All Settings button in the Log tab. This could be a sensible way to progress if many settings have been changed.

Looking at the image you posted, I can see why the star detection is failing - the stars will look more like hot pixels to the capture program.

I haven't come across the 'wont save unstacked frames' issue before, so will leave Robin to answer that one.

Dave

[chongo228]

Thanks for the reply.....The exposure was 60 seconds at 200 gain. I reset all the defaults under the alignment and log tab and then started adjusting the settings from there. I did have a hot pixel warning at first but got it to turn off after adjusting min star size (I think it was that setting). I've had good luck with aligning in Ha before but I think 60 seconds is my shortest exposure time I've done with Ha.


I picked 60 seconds because the brain said around 30 seconds exposure was the best for my Ha filter.....the smallest setting I had in my dark library was 60 seconds at 200 gain so I just went with that. In the past I usually did 3 min for my NB filters. Perhaps a good experiment would be to up the exposure time and see if it stacks.

[turfpit]

Chongo

60 seconds at 200 gain

From experience, I would consider that a decent choice for objects like M27/M31/M45 unfiltered.

For NB I wouldn't entertain 60s - even 3m is low. Looking at the good images on Astrobin, Ha using 5m+ seems the norm. Have you considered a higher gain for NB?

Dave

[chongo228]

Went out last night and started with some brighter Nebula.....everything stacked fine so I went back to the heart nebula and it stacked perfectly. I hadn't adjusted anything and stayed at gain 200 and 60 second exposure.

The only two differences were I had focused again...so maybe that was slightly better but I doubt it.

I also had dark subtraction on. I thought this was just for visual EAA. Does the live stacking program use the dark subtraction to help with hot pixels?

[admin]

Hi,

The star detection does use the image after dark subtraction so using a dark frame would help correct for any hot pixels being picked up in star detection.

Cheers, Robin