Day 9 - Observatory Build - Polar Alignment

Last evening it was time to do a complete polar alignment (PA) of the mount. With the sky clear (hazy but very few clouds) I set out around 8:30 to get all the equipment hooked up. Since the new mount is located further north from the old pier I couldn't use the network cable directly, so coupled another cable with an adapter which seemed to work to extend it to the new mount location. I had to restart my iPad remote session a few times because of connection issues (probably the coupler and the fact that I now had a very long cable run). But it finally settled and stayed running for the rest of the evening.

Now that the mount is perfectly level on the new pier (never that case for the old one) I should get excellent PA when the job is complete.

I installed my PoleMaster system to the AP1100, downloaded the new drivers and software, and started the alignment run. PoleMaster is a very accurate system for getting precise PA. On my old mount/pier I really didn't bother with it since the pier was never solid and the PA changed a lot - I just used NINA's Three Point Alignment app. But with a permanent setup, PoleMaster is the best option. In about an hour or so of work I locked down the axes on the mount. For grins I ran Three Point Alignment to see what it claimed for the PA values and ALT was spot on with AZI about 2 arc minutes off. Not sure if I trust Three Point Alignment to give me the most accurate answer, but a total of 2' is pretty low. Since it is easy to adjust AZI on the AP1100 I could tweak it later if needed. ALT adjustments are tricky because whenever you tighten the bolts to hold the mount's DEC axis after an ALT adjustment it always moves the AZI position a bit.

Now to try a few imaging runs to see what results I can get with the new pier/mount setup. I mounted my GT102 APO refractor with the ASI533mc camera. I had originally opted to use the ZS61, but it had a lot of flexure due to a single mounting point - not a good idea when you're trying to align a mount. Needed a bit of extra time though as I had to reinstall the auto focuser to the GT102.

First up were the slew tests. I slewed the scope from the park 3 position (pointing to north pole) to various objects in the sky - east, west, near zenith, near Polaris and due south at low altitude. In all cases the objects were within 0.5 degree of center. Keep in mind that an equatorial mount needs to flip when crossing the meridian from east to west and vice versa, yet the objects stayed well within the camera's FOV. This is an excellent result.

Next up, the tracking tests. I slewed to a star near the meridian at the celestial equator. Executed a 60 second exposure run and got perfectly round stars indicated a good start so far. Mind you, I'm not using any active guiding - just the AP1100. Then a 300 second sub. Same result. Finally, a 10-minute sub (longest sub I will ever take in practice) and still, perfect stars! All with no active guiding.

Spent another 45 minutes targeting various stars at different locations in the sky with 5 min exposures and all subs presented perfectly round stars. Success!

Now, it's off to getting the building up ... as soon as the weather is more reasonable (today temps reached 100 degrees with 116 feel-like temp) ... yikes.