Hi
Last night I started a astrophotography session with my equipment.
I faced a problem with elongated stars in all my images.
The images of M13 are captured with Vixen VC200L operating at 1280 mm and SBIG ST2000xm.
The autoguiding is done through the ST-237 guide chip of SBIG ST2000XM.
The above setup is loaded on Skywatcher HEQ5 mount.
During the astrophotography session, the telescope was pointing to the East and there's was no problem noticed with PHD guiding. The PHD guiding graph was smooth almost perfect. No wind blowing.
This is what I get after 1 minute exposure, elongated stars...
Here you can see a sequence of M13 images during this session. As you can see the stars do not move between the frames. So this excludes in my opinion any problem of differential flexure or bad polar alignment.
http://www.albireo.gr/tmp/%CE%9C13.rar
The problem must be backlash in the motor gears of HEQ5 mount. But there's a possibility I am wrong with this assumption...
Before opening the mount and adjusting the backlash, do you have any ideas what could be the reason of elongated stars?
Please notice that the elongated stars issue appears more when the telecope is pointing to the East.
With same setup described above I slewed the telescope to Zenith and captured a sequence of 10 minutes exposures of M51.
http://www.albireo.gr/tmp/M51.rar
As you can I still have elongated stars in the full frame of the image, the elongation appears radial this time.
Any comment on these M51 images star elongation will also be welcomed.
Thank you