ASI120MC fisheye lense

buschwick

Hey there. I'm new to the forum.

I have the 120MC and I'm trying to get a time lapse image of the night sky. How should I go about focusing the fisheye lense? I ask because I need about 1 minute exposure to see the stars, and that makes focusing very hard. I have to adjust, and wait a minute to see the results. I could be up all night trying to focus it before I even start the longer exposures for the image I want.

Is there a quicker/more clever way of doing this?

Thanks!

riklaunim

1 minute exposures seems way to long to be able to see stars. You probably would have to increase the gain to see them on 1sec or shorted exposures - and then focus... or focus at day or on the Moon if available.

Sam@ZWO

focus position won't change with exposure

so just use short exposure and try a far away buiding to focus

100 meter away should be far enough

buschwick

Thanks for the responses. IIRC I had the gain at 0. I didn't think to bump it up as I was afraid my 10 minute exposures would be washed out.

I'll try both suggestions. I'm just trying to get one of those images of the stars spinning around Polaris.

Thank you.

sgazer

hi, as suggested, you need short exposures with high gain just to focus the image. Focus on any bright stars anywhere. Then adjust your gain/exposure/position to capture what you want, it won't affect the focus.

I believe the stars orbit polaris every 24 hours (well actually we're just spinning around of course) so even a 10 min exposure will only capture a short streak of individual stars. The best thing to do is take shorter exposures, eg 30s, then stack them. There's software available to make this easy.