Many of us buy mounts and have no idea what the Periodic Error is for our mount.  We have gotten the manufacturers specifications and hope that our mount is better than what is stated.  Until now it was almost impossible for one to figure out the Periodic Error of their mount.  Take my mount for instance, an AstroPhysics 1200 mount.  I believe the stated Periodic Error for this mount is +-/5 arc seconds.  Up until now I was not sure how my mount actually compared to that.  Well after last night I know that my personal mount has a Periodic error of -3.9 / +3.5 arc seconds .  PemPro modeled my Periodic error over 5 worms cycles, and not only was I able to determine the Periodic Error but I also now know how smooth that error is.  Now for the amazing part, after PemPro modeled my Periodic Error and played it back to my mount I find my Periodic Error is now an amazing -0.4/+0.5 arc seconds.  Having the exact Periodic Error of ones mount can be a powerful tool especially when one is imaging.

PemPro is a great program to record your Periodic Error than to model it and create a smooth graph to play back to your mount in order to record a nice even graph of your Periodic Error from more than one cycle of your worm.

Below are a few screen captures of the program and what it looks like with PER recorded, then the smooth curve made to play-back to the mount to record the PER.  Then after play back what the Periodic Error of the mount became.

This is the initial recording of the Periodic Error of my AP 1200 mount.  The graph is nice and smooth of my worm
This is the curve of the DEC worm.  This is not used for anything but just here for comparison
This graph shows the actual Periodic Error of your mount.  This AP 1200 mount's Periodic Error is actually +3.9/-3.5 arc seconds.  Much better than the +-/5 arc seconds that that manufacturer stated
This is the play-back graph.  This is the window being displayed as PemPro plays back the fitted Periodic Error graph after it has been modeled
After PemPro has programmed the Periodic Error to the mount, I once again collected data on the NEW Periodic Error of the mount.  This is what is now looks like with the new PEM model recording from the mount.   Almost looks like the DEC axis look at next image
This is the DEC axis with the PEM running from the mount.
So how did this new program work?  As the graph displays the new Periodic Error of the mount is +0.4/-0.5 arc seconds almost no error now running on the RA axis.
This is the Histogram of the above graph.  I looked at this to see how accurate my data was and see that the Histogram is nice and symmetrical.  Nice fit and data looks right

This site was last updated 12/08/04