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Re: Spikes!

 

Dear Jamie,

Let's try to chase the cause...a couple of simple things to try:

1. Balance the mount in RA and DEC.

2. Now unbalance the RA: Wrap a rope or cord around the RA axis so the string drops to the East, and hang a weight on that.? Say 1 to 2 pounds should do it.

3. Try imaging and look for the same glitches.

If this remedies the glitch problem, the root cause is likely something in the RA drive... gear mesh gap.? There are several gaps that are built in.? The transfer gears have a gap (if you have a tucked motor system), and the worm to ring gear has a gap.? The hanging weight torque ensures the axis cannot shift during tracking and autoguilding.??

4. If this does not do the trick, please switch from your SCT to a refractor just to test if the cause is really the mount.? If the refractor imaging shows no glitches, it's possible one of the mirror holders in the SCT is loose.? Or the dovetail plate is not tight, etc.??

It's always hard to chase these glitches down.? Reflective optics are prone to loose optical elements.? ??

All the best,

Michael?

(I'm in Sunnyvale this week, not too far from you...if you want to get together, let me know).





On Thu, Apr 1, 2021, 10:55 PM Jamie Amendolagine <jamie.amendolagine@...> wrote:

[Edited Message Follows]


I've been having what is becoming a frustrating experience with large RA spikes. I've lost track of how many nights that I've focused on just getting guiding under control, maybe 5 or so. I've switched my setup from my APO to my SCT for galaxy season, so there's a bunch of recent changes, but all of the equipment was used before and performed pretty well. This exact setup has performed performed around 1.1 to 0.7 RMS, and this was before multistar-phd2. Right now I'm having a hard time keeping it below 2.0 RMS. There are some huge spikes (10 .. 14 or so) happening somewhat regularly, but not on a precisely regular schedule. Here's some examples of the time gaps between the spikes: 197s, 247,? 412, 485. The setup is an EdgeHD8 with a 0.7 focal reducer and an OAG. 178MC camera for guiding. I'm thinking of switching to the guide scope just to see what I can find. If everything is great there, then maybe there's some sort of flexure in the OAG image train.? I've gone through things carefully, making sure my PA is good, balance is good, wires are not snagging etc. Help!!!

This is not the infamous 76 second spike is it???

It's such a strange spike, maybe there's something going weird with the camera? I'm going to try and guide with the main camera just to see what I see.?

Help!

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