Re: Mach2 Unguided testing continues

Roland Christen

"So you are doing several quick keypad models in the course of the night - about every 1.5 hours."

Not exactly. I simply move the mount by 1.5 hours, do a short drift measure, move the mount again by 1.5 hours, do another, etc. until all 8 points are entered. Then I turn on the Drift model and let it run the rest of the night. The data collection (i.e. modeling) is done during twilight when the imaging system can first record stars but when it is too bright to take actual images.

There are two possible ways to do the model. Measure drift or measure the exact position of known stars which have extremely accurate data (needs a planetarium program with accurate data to .1 arc sec). In this instance I have chosen to simply measure drift along a path. Does not need a planetarium program at all or any knowledge of star names or star locations.

Step1: gather short drift measurements along the object path. Start at the object in the east, take a short exposure. Pick a star in the field (any star) and place a crosshair on it. Let it drift for 4 to 6 minutes. Recenter the star and press ENTER. You have recorded data point #1.

Step2: The keypad will now display > W 7.5 Deg. and < E 7.5 Deg. Pressing > or < advances the mount 1/2 hour. You can press it as many times as you want, each time it advances another 1/2 hour.

Step3: Pick any star in the field, place crosshair on it and repeat. (you can do this from 1 to 8 times for any constant Dec line)

When you have gathered enough points, press ESC and turn on the Drift Model. Then send the mount to the object and begin imaging. The mount will continually calculate the exact RA and Dec drive rates to keep the object centered. If done carefully you should be able to get 5, 10 and even 20 minute exposures drift-free.

This way you can quickly move across the sky along the path that the object takes and record what the drift is at each point. You do it all at once, not every few hours. That way you have a model for the entire path. You can use it every time if the mount/scope physical setup is not disturbed. If you tear down and setup next time, the model will be no good and would need to be re-done. This, of course, is fundamental to any modeling with any mount, ours as well as any competitor mount.

Is it foolproof? No, nothing is foolproof. You can certainly mess up a model and then tracking will be no good. You can also mess up guiding same way and get bad results.


-----Original Message-----
From: Dean Jacobsen <deanjacobsen@...>
Sent: Thu, May 28, 2020 1:45 pm
Subject: Re: [ap-gto] Mach2 Unguided testing continues

OK, I'm following you.  Thanks.  So you are doing several quick keypad models in the course of the night - about every 1.5 hours.  For a meridian flip, then do a quick keypad model and maybe another one in about 1.5 hours.

I am looking forward to the manual.
Dean Jacobsen 
Image Gallery -
Astrobin - 

Join to automatically receive all group messages.