Re: How Much RAPAS Misalignment is Too Much ?

M Hambrick

Hi Roland

I guess I am not sure what it is that I am seeing that I am calling field rotation. I have noticed that when I take a series of images, there is a shift in the position of the stars from the first to the last image. I decided to measure this shift using the information window in MaxIm DL to track the centroid location of the same star in successive images from first to last. The example below shows what I am seeing. I plotted the centroid coordinates over time for a series of images that I took.

In this particular example I was imaging M13. I took four 120 second subframes each of L, R, G, and B. The gaps in data are where I checked the focus whenever I switched filters, but I had the guider running continuously the whole time. You can see a relatively constant rate of change in each axis. The camera is oriented so that RA corresponds to the X-axis, and DEC corresponds to the Y-axis.

FYI I do not see any elongation in the stars in my guided images, even for 600 second subframes.

I would be grateful for any insight that you can give on this. I do not want to start messing around with the alignment screws on my RAPAS if it is not necessary. 


Join to automatically receive all group messages.