practical tips for multistar alignment #question

Mark Copper

I'm working through Quick Start for Basic Ops, Alt/Az (as I should have done before my first post...).

I can do 1 star OK but not great. That is, even at 167x with illuminated reticle, there is some drift away from center in the time between sighting and sync in SiTechExe -- even using Polaris as the first star.

But upon slewing to a second star -- I used Arcturus the other night -- the drift away from center was quite significant, moving to the edge of field of view before I could enter the data.

On one hand, the note in the checklist says not to worry. But on the other, I'm wondering what others are doing. Is method "A" (Skyview) faster than "B" (catalog)? Do errors propagate, or are they reduced as one adds in more collimating stars?

By the way, is alignment data saved when the controller is powered down?


Don W

Hi Mark,
The QuickStart process was developed by Chuck Shaw.  The QuickStart for Alt-Az describes a Single Star and a 3 star process - these inits use DIFFERENT calibration points.  So you have to understand how to do a star init.

For single star inits, you do an "OffsetInit".  This is the basic method of doing a star init in SiTech.  A window pops up with a count-down timer (default timer is 15 seconds but you can change this in ChangeConfig).  That window allows you to choose the multi-star type of init called a CalStar Init.

The OffsetInit is a single init and doesn't allow multiple stars to be used.  Each "new" offsetInit simply "Replaces" the previous one.

CalStars are used to create a sky model, and they keep track of the time between inits and each CalStar adds to the model of the sky.  So a 3 star init will be better than a 1 or 2 star init.  To do a 3 star init, all the inits must be CalStars.  If you do an OffsetIinit between CalStars, your model will be trash. 

However once you have initialized with a 3 star init,  slewing across the  sky to a new target, you CAN do an OffsetInit to correct the pointing to that new target.

In answer to your question about using SkyView vs Star Catalog, the SkyView will be much faster, and I think much easier.  You can set Skyview to show just the brightest stars to make it easy to identify them.

Don W