Start trailing causes

[Andy56]

Hi,

 

Last night I had an attempt to try wide field ie 50mm+ Optolong L-Extreme on an apsc sensor. 

This on an HEQ5.

I did a crude polar alignment because of technical issues. I put the tripod back in it's marked positions on the ground. This normally give reasonable polar alignment when using Sharcap.

Now I tried 300 seconds and got star trails. OK possible a poor polar alignment.

Now my question is how can I work this out from the image.

I'm guessing that if the polar alignment was good then this would be an RA tracking error. 

I've tried using Stellarium but can't get my head round which direction is which

So are there any tools that I could throw an image out and let me know how the drift aligns with RA.

Cheers

Andy

 

 

Edited October 6, 2022 by Andy56
Added image

[Stefan73]

24 minutes ago, Andy56 said:

So are there any tools that I could throw an image out and let me know how the drift aligns with RA.

You can upload it to https://nova.astrometry.net/upload and that will show you where the area you've photogaphed is in the sky so that helps with orientation then you can see how the star trails line up.

[barbulo]

Astrometry.net is the tool you need. It solves the image and provides orientation, visible objects...

Here is the result:

 

The trails seem to follow the DEC axis so it is likely a bad PA.

 

[alacant]

1 hour ago, Andy56 said:

300 seconds and got star trails

Hi

As @barbulo comments and confirmed on the ground using Siril: drift along DEC.

Over 5 minutes, the mount needs to be mechanically perfect, correctly adjusted and with both -very- accurate polar alignment and tracking. Maybe take more say, one minute frames instead? Or you could guide the mount. 

Cheers and HTH.

Edited October 6, 2022 by alacant

[Andy56]

Hi Stefan73, barbulo, alacant  Many thanks for you replies.

I see that it is just poor PA plus a possibly bit of RA tracking.

Thanks for the suggestion of Astrometry.net. This seems to be a useful tool for this.

Currently I have an issue doing manual PA using my HEQ5 because I have not focussed the PA 'scope, and the graticule illumination is either dark or too bright. Unlike the Star Adventurer which has a nice linear brightness adjustment. 

Now, if I can't resolve this I'll make a up a bracket for my guide scope and camera, then I can use Sharcap and PHD2.

 

Alacant: I was experimenting to see what the RA drift was for 300secs to get some good wide angle shots. I'm using the L-Extreme so I need fairly long exposures to get good signal. I may be wrong about this but I'm experimenting.

Cheers

Andy

Edited October 6, 2022 by Andy56
Added Another thought