From: "Milton Aupperle" <milton@outcastsoft.com>

Date: March 22, 2009 4:09:58 PM MDT

To: Astro_IIDC@yahoogroups.com

Subject: Re: Enhanced Big Saturn as Milton suggested

Hi Folks;

I already asked Alberto for more details off list on his guiding issue.

One thing people can do themselves is to check the "Guiding Log" that Astro IIDC will create for you. It records everything (calibration, calculations, results and all tracking corrections) to do with guiding. If you have a problem ,I need to see the log. It has enough information that I can feed the data back into Astro IIDC and see what it generates out, so it's essential thing needed to diagnose any problem.

If you suspect there is some mechanical issue (i.e. backlash, over tightened gear tension etc.), you can check for this after you've done a calibration by looking at the log.

In the log, look for the block of text that starts with

---------------- Starting Calibration----------

and ends with 

---------------- Calibration Completed----------

Inside of this block of text are usually four lines of information which will look something like this (the values may be different):

mPixelPerMillSecXRight = 0.00720

mPixelPerMillSecXLeft = 0.00705

mPixelPerMillSecYUp 0.007526

mPixelPerMillSecYDown 0.007604

These indicate the measured move rates on each axis (assuming you calibrated on all 4 axis, which can be optional).

If you compare mPixelPerMillSecXRight to mPixelPerMillSecXLeft or mPixelPerMillSecYUp to mPixelPerMillSecYDown, the values should be quite close, usually < 5% difference. If they are significantly different, then there is problem.

Most likely the problem is that the calibration could be bad (i.e. burst of turbulence, bumped scope, satellite, clouds) or a mount electrical /  mechanical issue. If you repeat the calibration and the issue persists, it's most likely a mount issue.

Backlash should not show up in these calibration, unless it's really really excessive. And if it's that excessive, the there is no point trying to guide with that axis. If it takes 10 seconds to reverse directions (especially Dec), then your guiding basically goes uncorrected for 10+ seconds.

As far as mechanical issues go, one I am currently struggling with a tension issue on my HEQ5 mount's Dec gears, and it shows up like this.

mPixelPerMillSecYUp 0.009401

mPixelPerMillSecYDown 0.007903

What happens is that when the gears engage to move, the over tension causes the gears to rotate back up, which cause more motion than expected in the up direction and less motion in the down position. That's why the rates are so different. If you manually move it at a slow guide rate (using the buttons in the guide sheet or hand controller), you can see this happen if your paying attention (I wasn't) when you change direction.

Hope that helps..

Milton Aupperle