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Greg, Polemaster is to align the polar axis of the mount correctly. Nothing less, nothing more. To correct for cone error and/or align the scope to the sky, other routines are necessary but the correct pointing of the polar axis is a prerequisite and will help with those other routines.
I’ve been trying to understand why PoleMaster isn’t working for me. It seems like the procedure would insure that the mount is correctly aligned but the scope itself could still be off a bit due to cone error since the procedure doesn’t involve the scope. What am I missing?
I believe Pole Master works regardless of cone error.
From: Greg Salyer <astronutcase@...
To: main <email@example.com
Sent: Fri, Nov 1, 2019 11:59 am
Subject: Re: [ap-gto] Orthogonality question
Sounds great. I've never been able to get PoleMaster to work. The best I can do is about 8' off (so I use PEMPro). Do you think it could be because of Cone Error?
Cone error correction. There is an easy way to detect it. In this new keypad routine, you simply go to a star on one side of the meridian, center it and press Recal. Then send the mount to a star the other side of the meridian with the same or similar Dec, center it and press Recal. The cone error is extracted and set in the servo. From then on any time you flip sides the cone error will be compensated. The only place where this cannot work is around the poles because it is a physical impossibility.
Cone error correction? or detection?
We will have a cone error correction in our upcoming keypad software.
Another name for orthogonality error is cone error. Site https://www.sharpcap.co.uk/conesharp has a good description of the problem and software to measure it. Apparently some mounts do allow an adjustment to correct for it. If you search for cone error I'm sure you will find more.
Suresh, I also have a couple of questions about Orthogonality error (OE). I hope you don’t mind me jumping in on this thread.
Can OE lead to issues with Guiding? I have continued to struggle to dial in my guiding and keep the total RMS error below 1.00. It is usually closer to 1.20 arc minutes. I have tried using the PHD2 settings recommended in a previous post by Rolando, and although they did help, I still struggle with guiding my Mach1 with a TEC140 attached (with or without an APPM pointing model). According my PemPro my polar alignment is +/- 2 arc mins. So, I suspect the issue is caused by OE. I am not that familiar with OE or how to correct for it.
Is OE something that can be detected by PemPro? It seems like that would be the right tool for the job. My rig is used solely for imaging, so I am looking for an imaging solution to help identify and recommend the OE adjustments that need to be made to correct for it. I have seen instructions where it ask to point the OTA towards zenith on one side of the pier, then set a 1-hour meridian delay and slew to the same spot on the other side of the pier. The problem I have is that with the TEC140 and my imaging gear, I am almost hitting the pier when the scope is pointed at Zenith. So, setting a 1-hour meridian delay (which I assume means a weights up position) is not really a good option. Finally, is the best option to adjust for OE to put strips of cut up soda cans in the saddle to push the back end of the scope one way or the other? I am surprised someone has not produced a saddle that has OE adjustments built in. The Soda can method does not seem like an easily repeatable process.
Anyway, as I have never had to adjust for OE, I am looking for advice on the best way to go about detecting it and then fixing it on the Mach1. Any advice would be greatly appreciated.