Re: Tracking ISS with Horizons #APCC #Mach2GTO

Ray Gralak

Hi David,

I would need to see the APCC and AP V2 driver logs to see what happened. One possibility is that the computer could not send commands fast enough, but I don't know why any of the rates would go below sidereal unless a limit was hit.


-----Original Message-----
From: [] On Behalf Of David Johnson
Sent: Tuesday, March 16, 2021 7:27 AM
Subject: Re: [ap-gto] Tracking ISS with Horizons #APCC #Mach2GTO

Thanks for the info. Here's what I tried next. I did as you suggested and was able to get 1 hour's worth of data at
1-sec intervals, bounding the time where the ISS would be above the horizon here. I then reset my computer's
clock to be very close to the time of the data that I'm using for test tracking, so the telescope would be pointing
roughly where it should be. I also verified that the mount time was also set to this time. The initial pointing this time
was fine.

What happened was that I still had problems with RA keeping up. The RA custom rate started out okay, and the RA
Delta was okay, but RA started slowing down quickly and even dropped below sidereal rate. Naturally, the RA Delta
went way up. It was pushing 2h when I stopped. Certainly, the tracking should have been well within the Mach2's
slewing capability. I tried it a couple of times, and the same thing happened.

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