Guide scope exposure and guiding accuracy

[GrampyG]

Hi

Did I see somewhere that the exposure time for the guide scope affects guiding performance?

Thank you

G

 

[tomato]

That’s correct. If your exposure time is too short, the guiding can end up ‘chasing the seeing’ and make erroneous corrections. If it’s too long, the correction cycle could be too long and errors will show up on your main image. The ideal exposure time will depend on your set up and the prevailing conditions, but I would suggest you start at 2-3 seconds and experiment from there.

[GrampyG]

Thank you for the reply.

Yes, I read this somewhere. I've been using the minimum that came up on the ASIair Pro, so I'll now try 2 secs instead of 0.5.

Thank you

G

[Clarkey]

The other negative of going too short on exposure time you will limit available guide stars or the s/n ratio will be poor making them easy to 'lose'. I tend to use around 3 secs on a ST80 guidescope and that gives very good guiding (conditions permitting).

[GrampyG]

I'm using ASIair Pro. The guide exposures are 0.5, 1, 2, 4, etc. I'll check top see if I can 'mod' these like exposures for the camera.

Thank you 

 

G

[Chefgage]

I use the asiair and a zwo asi120mm mini guide cam. With the star adventurer I have been struggling to get below 3" error in RA. Well last night the seeing wasn't the best but I experimented a bit with the settings and by using 1 second or 0.5 second exposures my guiding error stayed around 1.5" which for me was a bit improvement. I agree there was less guiding stars available and coupled with the bad seeing did not help. But overall this was an improvement.