Re: In-person mentoring needed

Don W

Hi Rob,

Tracking and GoTo's with an Alt-Az mount depend on accurate setup both of the SiTech system and the overall setup each night in the field.

First your mount must have a reliable drive system that must be setup properly and NOT slip or be loose.  You need to have accurate tics/rev set into SiTech for both axis.  If you use a friction drive, it must not slip.  Any eccentricity on the drive components will affect accuracy - for instance a friction drive with a slightly non circular pinion drive can have a lot of error. 

SiTech can use mount encoders, the higher the tic count the better.  Digital encoders with 4,000 to 10,000 tics can help but they are only accurate to about 1/10 degree.  SiTech can use them to detect any friction drive slippage using polite mode.

Mechanical stiffness of the mount structure and any drive components also affect accuracy.  Check that things like your eyepiece focuser doesn't have sagging or slipping motion.  When you setup in the field, doing a complete and accurate alignment, make sure the latitude is correct, then SiTech has a good chance to work accurately.

Don W

Using a PXP model can correct some of these errors, but it is always best to get the basic mechanical and structure it top shape before relying on the software to fix things.

---In SiTechservo@..., <r2d2b2@...> wrote :

Turns out that I had an issue with a loose screw on a gear! And maybe some other mechanical issues. I’m back to a working scope again, but I could really use some help. What are the top 5 things I need to know to get decent accuracy in Go-To? Right now my PXP RMS error is around 13 arc minutes, maximum 20. But I can’t hit an object unless I first do an offset-init on a star within 5 degrees of my target.


-Rob Brown


From: SiTechservo@... [mailto:SiTechservo@...]
Sent: Friday, May 25, 2018 3:02 PM
To: SiTechservo@...
Subject: [SiTechservo] In-person mentoring needed



I have built an alt-az mount for my 12.5" scope. Until recently, it was working in Go-To (but not well). Then suddenly it is off by tens of degrees in Go-To. Tracking is working acceptably well. I've read the Scitech manual but I am lost. Is there anyone in the Portland Oregon area willing to spend an evening with me going through the calibration and setup? The Moon is up, so it wouldn't be like giving up a dark night! There is so much to learn!


-Rob Brown

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