SharpCap Forums

Tonight I was trying to use the Polar Alignment tool and followed the instructions exactly, and a star was select in the lower right of the window showing how it needed to move in order to complete the alignment. I then zoomed the image so I could see it better when adjusting the knobs and then SharpCap selected a DIFFERENT STAR over on the very right of the screen. It did this several times, switching from one star to another. Any ideas what's going on?

Thanks,

Mark

Hi,

SharpCap tries to keep the same star selected, but there are a couple of cases where it will change

1) If the selected star goes off screen
2) If the selected star doesnt get detected for some reason in one or more images (this can happen particularly in noisy images).

I suspect it may have been the second cause in this case.

cheers,

Robin

Thanks Robin. I had the camera doing 1.5 second exposures at a fairly high gain. If I reduce the gain (to reduce the noise), then I'll have to go to longer exposures, which means I'll have to wait longer after each change of the mount's alt/az dials in order to see the change. Assuming that noise was the reason, what do you recommend as a prioritized list of solutions?

Mark

Hi,

the first starting point would be to turn up the 'Noise Reduction' setting in the polar alignment star detection settings -this applies a smoothing to the image that will reduce the noise levels and could help here.

Secondly, I wonder if you really need to zoom in - typically getting to within 1 minute of arc is good enough for PA accuracy, which shouldn't require zooming. Chasing the error down to 00:00:00 is not really worth the effort.

cheers,

Robin

Great, thanks! The reason that I zoom in during polar alignment is that my laptop isn't positioned very close to the mount and the "arrow and box" diagram on the screen is pretty small, so zooming in just lets me see it better.

Mark

Hi,

maybe checkout SharpCap 4.0 - there is an option for showing the alignment adjustments in large text over the image to try to help in this sort of situation : https://docs.sharpcap.co.uk/4.0/#Adjustment%20Stage

cheers,

Robin

Yes! The added text will be very helpful. Thanks Again for all of your work to make SharpCap such an excellent tool.

Mark