Tracking Problem - Checking my AZ-EQ5

[Jim Smith]

I have a SW AZ-EQ5 GT. I thought I would check how well I had it set up before I make another attempt at autoguiding and using bigger focal length optics.

It is mounted on a pier and I have polar aligned it with Sharpcap to within about 2 arcminutes, I believe. I took 100 x 30 second exposures of NGC7000 with my ASI 533 MCP through my Redcat 51. The mount was unguided but I did use PPEC as that seems to help the RA tracking.

The exposures are 2.5 degrees across. The total sequence of images is 52 minutes long.

I stacked all of the exposures without aligning to create the image below. I also made a video at 12.5 frames(images) per second.

In these images NORTH is horizontally LEFT (See stacked and stretched image at bottom). The little wiggly star lines are about 3 arcminutes long. I think the 5 or six wiggles in each line are the residual periodic error.

It seems that my mount was drifting DOWN (decreasing altitude) at about 3 to 4 arcminutes per hour. The drift looks about the same for RA and DEC.

Does anyone know what the problem might be?

 

 

 

[jambouk]

I’d say this is pretty good for an unguided 52 minute exposure. You could try tightening up the PA, but guiding should smooth this out, unless you are planning 30 minute subs or the like.
 

[Jim Smith]

1 hour ago, jambouk said:

I’d say this is pretty good for an unguided 52 minute exposure. You could try tightening up the PA, but guiding should smooth this out, unless you are planning 30 minute subs or the like.
 

Fortunately, I have now got autoguiding working so the drift shown above is a thing of the past...I hope.