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Hello Gemini I.? I realize I may also have an MI-250 problem, so I've cross-posted this.??

I've been working through all the growing pains of a new imager.? I think I'm close to getting useable data, but a couple of things stopped me last night.? I got a warning from PHD2 during calibration as well as a repeated error message.??

Every few minutes during guiding "practice" and when trying to take a modest 15 second image, I'd get this message: "Guiding stopped: the scope started slewing."? My mount was not slewing.? I have a theory, but some old posts here and in the MI-250 forum make me think it's not right.

The warning I got during my guiding calibration runs: "The RA and Declination angles computed in the calibration are questionable.? Normally, these angles will be nearly perpendicular,.." (the rest of the message is cut off).? PHD2 reports RA orthogonality error is 65.8, which I don't believe, even though I have no idea what the units are.? I have a photo of the message, if that will help.

Can someone help me with this???

I have found that bad polar alignment can affect orthogonality measurements as the star drifts while phd tries to measure dec movement. Also large PE can affect that as RA drifts during the measurements too. I’d try a better polar alignment and try again, and then do a guiding assistant run to measure PE.?

As for the mount slewing while guiding, you got me, someone else will likely chime in but i have no clue other than some button acting up on your hand controller or something but, if the mount is guiding, pressing on a button will not send the mount slewing so, who knows?

Lastly, maybe post the logs to phd and gemini.net to better see what’s going on

good luck

jonathan

Hi,

With Gemini 1 you'll want to make sure that the Gemini.NET ASCOM driver is set?not to use precision pulse-guiding option. That didn't work well in G1, but became the default, and only option in G2.?

Make sure it's unchecked, and Asynchronous Pulse Guiding is checked:


Regards,

? -Paul

Jonathan and Paul Kanevsky,?

Thank you for responding.? I hate to think my polar alignment is bad.? I spent a long time over two nights doing an old school drift alignment.? It takes five minutes for a star to drift off my reticle line.? However, I'll check it again.

My ASCOM driver was set up to use BOTH Precision Pulse Guide and Asynchronous Pulse Guide.? I've deselected the former and re-saved my settings/ profile.? I hope I remember to double check that the next time I go to my observatory.

FWIW, I received a suggestion that polar alignment might be a problem from a member of the MI-250 forum.? He also suggested the L4 EEPROM is the best version to use; mine's already been updated.??

Macdonjh,

I have experienced the very same slewing error at times but it is intermittent. I doubt it is your alignment; I drift align every time and check with PHD2. I also can easily hold a star for 5 min with no drift.? I have found that on breezy nights, I'm more likely to get the error. The strangest thing is that I never get this error when shooting targets in the northern sky, even with a slight breeze. My Precision Pulse Guide is checked; I will uncheck it and see what happens.?

Thanks for the discussion.

I made a trip out to my observatory last night.? I went through the list of ideas provided by the good folks here, on the MI-250 forum and on the SGP forum.??

Oldham couplers: tight
Precision Pulse Guide is not checked in my profile
Ran the PHD calibration (more below)
Ran the Guide Assistant, including backlash measurement (more below)
I also refocused my guide camera, it was pretty far out

My problem last night: I still got the "guiding stopped, mount started slewing" error once.? More frustrating, SGP and PHD wouldn't talk, when I started a sequence in SGP it would try to start guiding, but guiding wouldn't start.? I tried starting sequences with guiding not running as well as with guiding already running.? Same trouble.? I'll be reading up on SGP today...

Some unexpected results from PHD utilities:

I ended up running calibration four times last night.? The first time my orthogonality error was 65, then 34, then 18 and finally 18.5 (I rejected that last calibration run).? The change between the first and second calibration runs I maybe could explain because I refocused between those runs.? The last three runs, I can't explain.

Similarly, I ran Guiding Assistant twice.? Guiding suggestions were similar in both runs, so that's not interesting.? The backlash measurements are, though.? The first time my backlash was 0 +?1469ms, and the plot (photo attached) was all over the place.? After my last calibration run (after focusing) I ran the GA assistant again.? Backlash then measured 183 +?58ms, and the graph was textbook.??

In addition, while I was watching the first Guiding Assistant run, I noticed my Polar Alignment error varied between 3' and 30', depending on the sample.? During the second GA run, polar alignment error was consistent at 2.3'.??

I didn't spend much time guiding last night, but it did seem to settle down after a minute or two of running.? But, guiding by itself is no fun, so I didn't do it for long.