I am surprised to see the tracking you report as being .5 arc Sec. 35° above the Southern Horizon and .8
seconds of arc at 23° above the Horizon.
It would seem to me that if the Mach II mount with the encoders that almost completely eliminates all periodic error
would have that much tracking error.

Does the atmosphere produce that much error? I share an observatory with a friend who has a 14.25"
Newtonian f5.6, fork mounted with a 11" Byers gear on the RA and a SiTech II drive corrector. We have gotten
guiding with PHD-2 of .21 RA and .27 Dec rms. using the Tik management feature. The Observatory is located at
the SDAA dark sky site in Tierra Del Sol about 60 miles east of San Diego at about 3600' elevation.

Periodic error is completely corrected by the encoders but there are other sources of tracking error that must be minimized.

The level of tracking error will depend on the amount of uncorrected drift from polar alignment error, refraction, equipment flexure, tube currents, etc. Even with a good pointing model tracking quality is of course still dependent on the quality of local seeing and guiding algorithms.

-Ray Gralak
Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro
Author of PEMPro V3: https://www.ccdware.com
Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver

-----Original Message-----
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Allen Ruckle
Sent: Monday, March 16, 2020 7:22 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Mach2 and APCC last night

Terry,
I am surprised to see the tracking you report as being .5 arc Sec. 35° above the Southern Horizon and .8
seconds of arc at 23° above the Horizon.
It would seem to me that if the Mach II mount with the encoders that almost completely eliminates all periodic error
would have that much tracking error.

Does the atmosphere produce that much error? I share an observatory with a friend who has a 14.25"
Newtonian f5.6, fork mounted with a 11" Byers gear on the RA and a SiTech II drive corrector. We have gotten
guiding with PHD-2 of .21 RA and .27 Dec rms. using the Tik management feature. The Observatory is located at
the SDAA dark sky site in Tierra Del Sol about 60 miles east of San Diego at about 3600' elevation.

I am waiting to be notified that the AP Mach2 I ordered last year. I have been thinking it would have more
accurate tracking than what I already have access to. am I going to be disappointed?

aruckle