SharpCap Forums

Hi folks,

currently I am reworking the code that deals with dithering (and monitoring guiding) while live stacking, and I've come across a question that it would be interesting to get some additional viewpoints on...

The question is

If you have set the application up to stop stacking if guiding is lost, what does that really mean?

* Should any loss of guiding during a frame count as 'guiding lost'? Even if it is just 1-2s during a relatively long frame like 120s?
* Should there be a limit - ie guiding lost for more than 5% of frame length means lost, otherwise ignore?

For reference, the way it currently works in live stacking is that if guiding is active at the end of a frame then the frame is considered good, which isn't right whichever way you look at it. For capture with the sequencer, it works a different way - if the frame is more than 95% complete when guiding is lost then it is kept, otherwise it is cancelled.

Anyway, if there is a 'right' answer then it is probably to throw away the frame if guiding is lost at all, but it's not necessarily the best practical answer.

Any opinions?

cheers,

Robin

Hi Robin,

Interesting questions. If guiding is lost, it probably means clouds or a large movement. Either would suggest not stacking the frame. But perhaps that depends on how far in it is. Beyond some fraction (say 80%), perhaps it’s best to keep that frame (FWHM, Brightness filter or post-processing will sort out the fallout).

If guiding comes back on during the acquisition of a frame, I like the way it works now, where the frame is accepted. It all depends on the settling time and whether tracking had settled for long enough before “guiding again” so that the frame is good. Best to keep it and sort that out in post processing (I use “saved stacked”).

A related question concerns how camera APIs work. Is there a command to “abort an acquisition”? In the guiding lost case, aborting would make sense. You then revert to 2s frames, which makes sense marking time.

Cheers, Chris.

Hi Chris,

thanks for the input - useful thoughts.

Most cameras allow you to abort an exposure one way or another (either there is a direct way to do it, or as a side effect of something like changing the exposure). SharpCap is typically set up to do this if the current exposure is long and you change the exposure slider for instance... You don't want to wait for the end of a 60s exposure already in progress - you want the new length to be used right now!

I had also been thinking about dropping to shorter exposures when guiding is lost, although I haven't written any code to handle that yet. It's certainly a possibility.

cheers,

Robin