Wednesday, November 11, 2015

"I accidentally a good equatorial mount."

That's the gist of it anyway. I bought a Celestron AVX mount for peanuts because it said it was defective. I figured that the mechanics of it were well liked on the internet, but that some of the early versions had electrical problems. My goal was either to fix the control boards (if I could find something fixable) or to replace it all with my own control system.

When it arrived on my doorstep I disassembled it completely and started looking over everything. Checked all the components that were check-able with a multi-meter and couldn't find a darn thing wrong. The control board was also the brand new version...something just didn't add up.

The mount came bare (no tripod, motor cables, power adapter, hand controller, weights, etc), so I had to get a few things before I could test it. Here are some mysteries I spent too much time researching, but solved:

  • The 8 pin, RJ45 connector between the DEC motor and port is, in fact, just a standard straight-through cable like those used for networking. I made this to size using some CAT-5 and connectors I had.
  • The Nextstar+ hand controllers are all the same, the two model numbers for EQ and ALT-AZ are basically just there to let you know which firmware was loaded on the board. I know this because the budget friendly used one I acquired turned out to be loaded for ALT-AZ and gave me all sorts of trouble before I reloaded it (twice, the update software defaults to what it has regardless of which mounts it detects). Note the "+" though, the non-plus ones use different things inside and probably won't run the newer firmware.
  • You can use a regular 12v power adapter and ignore the fancy thread-on-overpriced one Celestron sells. I recommend tying it off though, the clipping part of it is rather weak and you don't want it to get pulled out of the connector if you can help it. I will probably replace this connector with either a standard one or a waterproof one in the future.
Once I plugged everything in the darn thing fired right up. I pointed it around during the day until I was satisfied there was nothing wrong with it, and then later on that night I tried to align it. That's when I discovered the ALT-AZ vs EQ firmware thing. Even though "EQ North" was a tracking option in the menu, it has no idea how to deal with the mount.

I managed to get a few images out of it with nothing more than a "that looks about right" aiming of the scope at Polaris and then manually pointing it at things, but nothing to write home about.

Orion Nebula: Fuji X-T1. 30 second exposure, ISO 1000 @ 200mm F4.8
Things are forgiving at 200mm. It takes a lot more to get things right through a real telescope...

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