Re: PEMPro and accurate polar alignment
Here's what I do at the zenith. I link to the mount via MaximDL, acquire a guide star and start a guide exposure with aggressiveness set to zero. I open the tracking Error Graph and watch the RA drift. After a few minutes it is apparent that the drift is either + or -. In my case I know that with my camera orientation a minus drift means I need to raise the altitude axis, but in your case you need to make that determination by trial and error.toggle quoted messageShow quoted text
How much to lower or raise? Usually from a PEMPro drift method to the zenith adjustment the difference is about 1/4 rotation of the altitude adjustment wheel. In my case, after this adjustment I get less than 1 arc sec drift in a 15 minute time period on either side of the zenith up to about +-1 hour. Beyond those boundaries that, the drift begins to increase, but even though there is slightly more drift I can still do 5 to 10 minutes with no ovality showing up in the stars.
For those wishing to wade thru more rigorous methods of polar alignment and a handy calculator, here are two websites:
From: Hemant Hariyani hemanthariyani@... [ap-gto]
Sent: Mon, Sep 25, 2017 12:54 pm
Subject: Re: [ap-gto] Re: PEMPro and accurate polar alignment
I tried measuring drift using PEMPro at zenith and am a bit surprised by the result.
I first tried to change position of altitude drift measurement in PEMPro slew dialogue but I was not able to select a degree offset less than 30. So I slewed my mount to zenith using my latitude as declination and a close to zero degree offset from meridian. I chose to be on the west of meridian.
I then started measurements in PEMPro to start with, it showed a huge offset and asked me to lower my altitude by 60 odd arc minutes. This reduced over a period of time and by the end of 5 minutes run, it was around 15 arc minutes. Without re-positioning the mount to zenith I let it continue for more time, restarting measurements and after about 20 minutes, this was down to 2.8 arc minutes. I tried this again and the results were fairly consistent. I have no idea on what is going on here. I did not affect this significant a change in measurements in such a short period of time. Any guesses on what can be going on? I have encoders enabled.
On Mon, Sep 25, 2017 at 10:01 AM, chris1011@... [ap-gto] <ap-gto@...> wrote: