Re: Just for fun with AP1200GTO


Roland Christen
 


I suppose a mount with optical encoders would probably do better, but for me this is largely well enough.
Drift rate is not dependent on whether you have encoders. The primary drift rate is dependent first and foremost on your polar alignment. This is especially true of Dec. The RA drift rate will be affected by how close to sidereal the clock motor is running, and that depends on the crystal frequency accuracy inside your CP controller. These usually are accurate to better than 1 second per day.

Encoders provide precise pointing in both axes and moment to moment tracking accuracy that does not vary due to worm and gearbox errors. Since in your case you were not changing the position of the Dec axis or tracking in Dec, then the motor in Dec was stationary and would be stationary the same way with or without encoders.

Rolando


-----Original Message-----
From: Geert <geert.vandenbulcke@...>
To: main@ap-gto.groups.io
Sent: Tue, May 5, 2020 9:55 am
Subject: [ap-gto] Just for fun with AP1200GTO

Hello,
 
On 2 May 2020, over a period of 4 hours I took 120 images, each 60s exposure and 60s interval with a 150mm refractor at 1093mm focal length, unguided with my AP1200GTO mount, periodic error correction enabled.  So the mount was just running without autoguider inputs during this period.  This was to measure the changing brightness of a HADS variable star GSC3810-1553. 
 
As I had all those images anyway, I wanted to see how much the mount drifted in this 4 hour period, so I stacked the first and last images and measured a drift in RA of 14.08 arcseconds in RA (3.52"/h) and 66.56 arcseconds in Dec (16.64"/h).  This star is at +55° declination.
 
I suppose a mount with optical encoders would probably do better, but for me this is largely well enough.
 
The image stack can be seen on https://astrob.in/pve8nm/0/
 
Best regards from Belgium,
 
Geert Vandenbulcke

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