Re: New file uploaded to ap-gto

Roland Christen

For those who hate the files section, I have also posted it here on Facebook:


-----Original Message-----
From: chris1011@... [ap-gto]
To: ap-gto ; ap-ug
Sent: Mon, Aug 20, 2018 5:47 pm
Subject: Re: [ap-gto] New file uploaded to ap-gto

Hi Astronuts,
My recent testing of mounts included an 1100 mount set up with my 130 EDX refractor and the analysis software PEMPro. Our runs of the 1100 mount have been very consistent with low periodic error and excellent repeatability. I wanted to do a real-life test on the night sky here at the observatory and show you the results.
The mount's raw periodic error measured at around 3.5 arc seconds on a night of medium seeing conditions. I ran 5 worm cycles due to the seeing being not great and created a PE curve that was then downloaded into the CP4 controller as the picture shows. The curve was run again with PE correction turned on and the result was less than 1 arc second. Analysis showed that the original curve put a 2nd harmonic into the PE playback, so I refined the curve by subtracting the second curve from the first and loaded the result into the CP4. PEMPro saves all the curves, so if you make a mistake, you don't need to start all over again.
The final result was a periodic error of 0.5 arc seconds, and at that point I felt it was good enough for a test run. I ran the mount for several 30 minute unguided test runs and had results of 1 arc sec or less in tracking error. This was done near the meridian and high enough so that atmospheric refraction was not an issue. I also made sure that the polar alignment was adjusted to zero out RA drift, something I did very simply by watching the curves in PEMPro and adjusting the altitude axis accordingly.
I feel that this is quite doable for the 1100 non-encoder mount and shows the level of performance you can achieve with this premium product. PEMPro comes with the 1100 mount, and it really works. It is not difficult at all to use and is very accurate. Just follow instructions ;^))

P.S.  the 1100 mount really is the Cat's meow and a bargain considering what level of performance, usability, portability and overall quality you are getting. There are many 900/1200 mounts out there still in use after 20 years and this mount beats them both.

-----Original Message-----
From: ap-gto gto@...>
To: ap-gto gto@...>
Sent: Mon, Aug 20, 2018 5:40 pm
Subject: [ap-gto] New file uploaded to ap-gto


This email message is a notification to let you know that
a file has been uploaded to the Files area of the ap-gto

File : /1100 Periodic error testing/8-14-2018_1100_PemproRunSm.jpg
Uploaded by : uncarollo2 <chris1011@...>
Description : Measuring and refining periodic error using PEMPro

You can access this file at the URL:

To learn more about file sharing for your group, please visit:


uncarollo2 <chris1011@...>



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