Kevin_A I would like the option to try reducing the sawtooth patterns.
Methinks you would like it. The sawtooths really calm down.
But it won't help the sporadic jumps that you are seeing, though. That has to some mechanical flaw if it were not caused by wind gusts.
Next, they need to allow more flexible guide rates than the four that ASIAIR provides. This way, if the mount has too much error to use 0.25x sidereal, you can choose 0.3x siderate rate or 0.4x sidereal rate, which would still be better than 0.5x sidereal. Or, at least provide 4 more useful rates, by dropping the 0.75 and 0.9x rates.
Funniest thing is that I have seen people push an RST-135 to 0.9x sidereal rate, in the hope to correct faster. Based on the sawtooths, it is the opposite of what you want to do. to a mount with large slopes :-).
By the way, although I did not buy the RST-135E to use as an auto-guided mount, I will be spending a few months with the encoder mount in place of my primary RST-135 to further study the problem. Conveniently, its encoder can be turned off. I do not expect the encoder to be able to smooth out the higher harmonics, and therefore not really improving the autoguided numbers by any substantial amount, if at all. I.e., just because the p-p periodic error is now 5 arcseconds instead of 50 arcseconds, I don't believe that it means that I can start using 2-second guide exposures. It is not the p-p error, but the slope of the error that determnes the needed frame rates. But we shall see.
Chen
