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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