Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

  • Announcements


  • entries
  • comments
  • views

Second light, a little wobbly



The forecast was spot on for a change. Clear all afternoon into the evening, clouding over later. So it was worth a good run at fixing the issues I had with my first attempt at polar aligning the new AVX mount and maybe, finally, getting some subs.

I've noticed a few extra things this time:

  • the tripod is much lighter than the Evolution one. They share the same legs so it's just down to the mounting plate and the accessory tray being much smaller. It's a one hand job rather than two for the Evolution. It still feels as solid. In fact, it was quite windy last night and it seemed to handle it ok.
  • Likewise, the mount itself is lighter, though it's more awkward to carry. I do like that Celestron have now added carry handles to its latest mounts.
  • The mount seems to remember the time/date. It must have an internal battery clock. I have to set the time each time I used the Evolution, so this is a nice quality of life improvement.

Last night it took about the same 25 minutes to get set up and everything connected. I decided to use the USB hub and also connect the mount to the PC in the hope of testing mount control from within SGPro. This gave me even more cables to deal with. Having powered up and roughly aligned the mount using a compass, I checked my time, date and location data and set StarSense to auto align. It hung on the first slew with a message on the handset that it was trying to read the alignment. After repeating this a few times and getting the same result I restored the handset to factory settings, rebooted and tried again. This time it worked. It seems I'd saved alignments on the previous session and this was messing with the process. 

I finally got aligned and slewed to Betelgeuse. It was in the field of view so I started the Polar Alignment routine. It slewed again (as expected) but no sign of Betelgeuse in the field of view. I did a blind plate solve and I was about one frame to the west. I adjusted the azimuth bolts and finally found the star and centred it. I ran StarSense auto align again and slewed back to Betelgeuse. No sign again! I took a test shot anyway, and was seeing significant trails even in a 30s shot. Something wasn't right. I'd forgotten to calibrate StarSense.

I reset the alignment model and started again from the beginning. It seems to get a good alignment I need to complete a calibration step each time. So my new alignment process is:

  1. Roughly align the mount with a compass
  2. Set the mount to its home position
  3. Check time, date and location data in handset
  4. Run a StarSense auto alignment
  5. Select and slew to polar alignment star (close to meridian and ecliptic)
  6. Press Align to calibrate to this star, then move it into centre of cross-hairs using handset
  7. Run Polar Alignment, centring star using the alt and az bolts
  8. Run StarSense auto alignment once more

Even with this, I can't have been spot on. I slewed to IC443 (bang on) and framed it. I then took a series of single exposures from 30s to 180s to see how well the mount tracked unguided. Here's the series with the same auto stretch. The 60s and 180s show trailing but I was pleased I could get a 120s sub without trailing.

30 seconds


60 seconds


90 seconds


120 seconds


180 seconds


Having run these quick tests I wanted to gather some data so I set a sequence of 30 x 120s subs running on IC443 and went and caught up on some TV for an hour. By this time the clouds had come over so I packed up and transferred the files to the main PC for processing. After weeding out cloud covered images I found that about a quarter of the subs showed a lot of trailing. Also, between the first and last sub, the frame had moved significantly in RA and a small amount in Dec. I definitly need to spend a little more time on getting my PA right, maybe even running it twice. I also need to start guiding!

IC 443 Jellyfish (if a little wobbly)

Choosing the best 21 images (though some still showed trailing), here's a quick process of 42 minutes at gain 139 offset 21 and cooled to -20C on IC443 using the Celestron AVX mount, Skywatcher Esprit 80, ZWO ASI1600MM-C and the Astrodon 3nm Ha filter. It's noisy, the stars are elongated because of trails, but it's a image (and considerably better than the one I took on the Evolution)!


  • Like 2


Recommended Comments

There are no comments to display.

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