1 reply to this topic

[GregsCNAccount]

For many years I have been less than happy with the RA guiding performance of my Losmandy G11 with Gemini 1.  The RA RMS was almost always about 1.5 times what the Dec RMS numbers were.  I had carefully tuned the mount and made modifications that should have made things better, but it never quite got there.

 

I had always used a guide rate of 0.8X, thinking that the faster guide rate meant faster corrections.  That was bolstered by the recommended rate for my AP 1100GTO being 1X.  Seemed faster must be better.  I had also had nothing but trouble trying to use PEM-Pro to create a usable PEC curve.  Then I found this video discussing the idiosyncrasies of the Gemini guide rates and their effect on minimum guide steps:

 

https://www.youtube....h?v=KOJ4SXWzLCc

 

The issue is that the minimum RA moves are asymmetrical and vary with guide rate.  They are most different and larger at the 0.8X guide rate.  They are least different and smaller at the 0.2X guide rate.  The 0.2X rate is recommended in the video for generating and using a PEC curve from PEM-Pro.

 

Last night I tried the 0.2X rate and had the best RA guiding relative to the Dec RMS numbers that I have ever had.  It was always at least very nearly as good as the Dec and occasionally ever a bit better.  I have never seen that on this mount.

 

I'd be interested in hearing what others have experienced in this regard.

[macdonjh]

Interesting, in my short time imaging I haven't heard about anyone using a guide rate slower than 0.5x.  I'm using 0.5x.  I asked about using a faster guide rate (for the same reason you gave), but Brian Valente recommended against it, so I haven't tried it.

 

I also haven't had much luck with PEM Pro.  

 

Before trying 0.2x guiding rate, I'm going to experiment a bit more with keeping my mount balance a bit east heavy.  That also helped my mount.