Re: 1100GTO AE PHD2 Settings #Absolute_Encoders #Guiding

Roland Christen

Refocusing does not require re-balancing. I would not worry about it.

Seeing can be judged easily by turning tracking corrections off and watching the star excursions on the tracking graph in Dec. If the star jumps around +- 1.5 arc seconds, then your seeing is 3 arc sec P-P and you can then set your Min Move to that level. Seeing will vary somewhat with altitude, so if you image an object near the zenith, the seeing might be twice as good as it would be if the object is at 30 to 45 degrees above the horizon.


-----Original Message-----
From: Andrew Jones via <andrew.jones@...>
To: <>
Sent: Mon, Aug 2, 2021 12:35 pm
Subject: Re: [ap-gto] 1100GTO AE PHD2 Settings

Hi Roland.
I really appreciate these detailed After Action Reports. 😊  These reports provide useful insight for those of us still learning the art/science of astrophotography and how to get the best experience from our AP Mounts. I recently upgraded my Mach1 to a 1100 AEL. I am still in the process of getting it setup in my observatory (waiting for some cooler weather here in Texas), but once setup these reports will be useful references to help ensure I am able to get everything setup and calibrated correctly.
The info you provided about DEC balance is very interesting. I never really paid that much attention to the DEC balance. I would balance my TEC 140 close to its imaging configuration when putting the scope on the mount in my observatory, but then I really didn’t mess with again. I just weighed my camera/FW combo and it is almost 5lbs. Combined with 85mm of back focus for the TEC 140, I would guess this creates a fairly substantial moment arm on the DEC axis (similar to the recommendation to avoid putting counter weights as the end of the counter weight bar vs. adding more weights). This moment arm could help explain why I always struggled with guiding with my Mach1, particularly on the DEC axis. PEMPro indicated my polar alignment was within 1-2 arc min on both axis, so I don’t think it is an issue with alignment. Your worse RMS of 0.6 arc sec would be a dream for me. On a typical night, I am lucky if I could keep the RMS below 1 arc sec using PHD2. Based on your observation, I will be pay more attention to the DEC balance and balance more frequently for different temperature ranges and see if that helps with my guiding.
I always pay close attention to your experiences with PHD2. As mentioned, I have struggled with guiding. It is helpful to read your(and others) observations and experience with PHD2 and what settings they were using. I wish there was one universal combination of settings in PHD2 that would work in all conditions, but that probably unlikely. It helpful thou to read what settings are working for other AP mount owners that I can try with my own setup, at least as a starting point. I just saved a note with the settings Brian Valente posted earlier and intend to give those a try once I get everything setup.
I have a couple of questions if you don’t mind.
  1. I can balance the scope at the begging of the night close to my last focus position, but as soon as I run auto focus obviously the moment arm will change somewhat. Where I image, it is not uncommon to see a 10°F change in temperature during a given imaging session. I refocus ever 1.5° change in temperature.  To avoid the static friction issue on the DEC axis, is it necessary to rebalance during an imaging session or are the changes to the moment arm due to refocusing insufficient to cause the static friction issue you discussed? In other words, how much out of balance can be tolerated due to refocusing before we should be concerned about static friction?
  1. Kind of unrelated question, but how do you determine what your Seeing is during an imaging session? Are you just using the FWHM as reported by your imaging software or do you have another method of determine what the seeing is on a giving night? Based on what your report regarding the impact Seeing has on guiding, it would be good to have a easy way to determine what the Seeing conditions are for a given night so we can adjust our guiding expectations accordingly. I know there are Sky Quality Meters as well as Clear Sky Charts online. I was just curious if you use one of these tools to determine your seeing or if you have another method. Probably a stupid question, but hey I am still learning…
Clear Skies,
Andrew J

Roland Christen

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