Re: Mach2 and APCC last night


Roland Christen
 


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.
I think people misunderstand what is a tracking error coming from a mount and an atmospheric seeing error caused by random motions of a star.

Certainly a star will bounce around more when it is low in the atmosphere, but that is NOT a tracking error. That is atmospheric motion which is easily enough measured simply by looking at the moment to moment position of a guide star in Declination when the guiding is turned off. As soon as you turn guiding off, the reported position of the guide star is exactly that of the atmospheric motion, and has zero to do with any king of tracking. That motion will also be present in the same amount on RA whether you are simply tracking or actively guiding. That amount is the floor below which you cannot go.

Rolando


-----Original Message-----
From: Allen Ruckle <aruckle@...>
To: main <main@ap-gto.groups.io>
Sent: Mon, Mar 16, 2020 9:22 pm
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

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