Jump to content

 

1825338873_SNRPN2021banner.jpg.68bf12c7791f26559c66cf7bce79fe3d.jpg

 

Oval Stars


Recommended Posts

I have recently started using a 8x50 finder scope as a guider,and since adjusting the settings in the Brain,to around 2000 ,i was getting good results the other night.However last night i tried for high up targets in Draco,the calibration usually completes within 27 steps,and kept the guide star bang on the cross wires.After a 10 min exposure,my image was really dissapointing.The stars were slightly oval,and spoilt the image.I have an omni 120mm refractor with a 80 ed piggybacked ontop,well within the cababilities of the EQ6.Since i have a lot of cables,dangling about,although i have tried to secure them,although difficult with a long refractor,as some slack is required by the nature of the mount.

Do you think the Finder is not upto the job,of guiding a long scope at high altitudes.Or do you think there is flexture creeping in some where.

Sorry for the long post,just trying to explain things.

A 5 min exposure just starts to show the stars becomming elongated.

Cheers. Mick.

Link to comment
Share on other sites

Hi Mick,

Sounds like an alignment error to me. If the alignment of the mount is slightly off in either altitude or azimuth from true polar alignment, then tracking over a period of time would begin to show image drift... hence oval stars.

Check your polar alignment before trying anything else. It is the easiest to fix and usually the first thing to check.

Dan

Link to comment
Share on other sites

Don't forget that even if you are guiding the Earth is still rotating under the mount. So it really needs accurate polar alignment for a 10 mins exposure or you'll get star trailing, or in this case, slightly oval stars. :)

Link to comment
Share on other sites

  • 5 months later...
Thanks for the replys guys.

I thought my alignment was pretty good,because guiding at F7.5 produced round stars,its only since using the finder,that oval stars have crept in.

However i will check again.

Cheers.

Mick.

I thnk i have that also, im going to look at the images i took last night in better detail later.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.