Askar FRA400 tilt issue?

[Dave kay]

Hi Folks,

I am looking for some advice. I have recently purchased an Askar FRA400 and took it out for the first time last night. I took images of two targets, the Sadr region and the Eastern Veil, and both show some odd shape stars in the corners of the image. Strangely though, the odd shaped stars are in different corners of the two images. 

I was imaging with a ZWO294MM and guiding with an ASIAIR plus at 0.4 RMS total. 

The SADR region FWHM eccentricity report from Pixinsight looks like this.

The Eastern Veil FWHM eccentricity report from Pixinsight looks like this.

Any help / advice / guidance would be much appreciated,

Thanks in advance

Dave. 

[michael8554]

Hi Dave

Not much info on your setup and exposure duration.

I assume these are "long exposures" ?

IMO both shots display guiding errors - all the stars are elongated in the direction top left to bottom right.

I would eliminate guiding errors, then test.

Look at a single short exposure, stretched if necessary.

0.4RMS means nothing if individual RA and Dec errors are not similar.

Michael

[Adam J]

20 hours ago, Dave kay said:

Hi Folks,

I am looking for some advice. I have recently purchased an Askar FRA400 and took it out for the first time last night. I took images of two targets, the Sadr region and the Eastern Veil, and both show some odd shape stars in the corners of the image. Strangely though, the odd shaped stars are in different corners of the two images. 

I was imaging with a ZWO294MM and guiding with an ASIAIR plus at 0.4 RMS total. 

The SADR region FWHM eccentricity report from Pixinsight looks like this.

 

The Eastern Veil FWHM eccentricity report from Pixinsight looks like this.

Any help / advice / guidance would be much appreciated,

Thanks in advance

Dave. 

Got to be honest in my practical experience most "tilt" issues turn out to be optical collimation issues. Is the pattern changing as you rotate the camera. If it's not then it's tilt. If it is then it is collimation. In a fast flat field refractor it's more likely to be collimation. However looking at the images themselves and ignoring the  pixinsight contribution completely it's the bottom left looking soft so you may well have a combination of both issues. 

Adam

Edited August 27, 2022 by Adam J

[Dave kay]

On 27/08/2022 at 10:33, michael8554 said:

Hi Dave

Not much info on your setup and exposure duration.

I assume these are "long exposures" ?

IMO both shots display guiding errors - all the stars are elongated in the direction top left to bottom right.

I would eliminate guiding errors, then test.

Look at a single short exposure, stretched if necessary.

0.4RMS means nothing if individual RA and Dec errors are not similar.

Michael

Thanks for the input Michael.

I was guiding on an EQ6-R and the subs were 300s each. 

I'll have a look around my guiding when the next clear night arrives, hopefully it is just a guiding issue. 

[Dave kay]

On 27/08/2022 at 12:01, Adam J said:

Got to be honest in my practical experience most "tilt" issues turn out to be optical collimation issues. Is the pattern changing as you rotate the camera. If it's not then it's tilt. If it is then it is collimation. In a fast flat field refractor it's more likely to be collimation. However looking at the images themselves and ignoring the  pixinsight contribution completely it's the bottom left looking soft so you may well have a combination of both issues. 

Adam

Thanks for this Adam.

I'll rotate the camera on a single target when the next clear night appears. 

Fi gers crossed its just a bit of tilt or guiding errors, collimation issues would be a pain. 

Dave.