Equipment Tuning

I worked with the TV/GM8 and the Meade/G11. This is the second time that I have had both scopes set up at the same time (first time was two nights ago) and it is the first time that I have worked with both on the same night.

My objective for the TV/GM8 was to check backlash. It seems worse than it was two nights ago. It was so bad that PHD2 could not successfully complete a calibration or a backlash test. I “manually” tested the Dec backlash by using the hand controller to nudge it in one direction and then the other. In the first direction, the stars stopped moving at the end of the nudge. In the other direction, they continued to move for ten seconds. That’s a lot of slack in the gears. Maybe I didn’t tighten the worm blocks and they slipped? I’ll work with it today.

I started having issues with the hand controller locking up, so I ended my session with the TV/GM8.

My objective with the Meade/G11 was to do a quick backlash check and to check collimation.

Since I do not have an OAG on this scope, I elected to check backlash by nudging with the hand controller and observe the stars. The stars appeared to stop moving immediately after the nudge in both directions, and on both axes. Maybe I have this one right. In hindsight, there is no reason that I could not have connected PHD to the ASI290MM, because we are using that camera to test guiding on your CG5.

The collimation check started with an email exchange with James Willinghan. I have checked my collimation a couple of times over the 6+ years that I have had the Meade, and have always found that that it appeared to be perfect in a 12mm eyepiece. Since I have not adjusted it, it still has the factory collimation.

I found this odd since I am advised that collimation should be checked frequently, and in fact James checks before every planetary imaging session, and he checks using his imaging configuration.

With this in mind, I checked using my imaging configuration, which is the ASI290MM/TV 2.5x PowerMate/Meade. The total focal length here is almost 7,500 mm. Perhaps this is the best look at my collimation that I have had yet. It looked good in real time on the laptop display. Only after coming inside and looking at it closer was I able to detect what I think is a slight thinning of the diffraction circles toward the 10 o’clock position. Slowing down the frame rate helped me see the eccentricity even better. The seeing wasn’t great, so I don’t know if I would adjust based upon this view, but now I know how to check my collimation in a meaningful way.

Here’s a Firecapture of Vega defocused for a collimation check: Image

A slight regret is that Saturn and then Jupiter would have been coming out of the trees after the Vega capture. I should have stayed up for it.

© James R. Johnson, 2021.

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