RE: [APML]: More ST-4 Questions

[charles@jon.cjfny.org]

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AS>Charles wrote:

AS><< I also used the ST-4 successfully for the first time Saturday. >>

AS>Wow -- quite a bumper crop of new ST-4s this week! :-)

AS><< Just wondering why the unit stopped tracking successfully after 15-20

AS>minutes? This happened at about the time I reached the zenith (Cygnus
AS>was passing overhead). >>

Wil:

Thanks for a detailed and highly useful (and humorous) response to my
queries. I now understand the unit a lot better. Since you seem very
patient, I have other questions about the ST4:

Q1. Should I be nervous if I see an EE reading for more than a few
clicks (frames)? Or should I not assume the tracking is in trouble?
Sometimes it would recover and go back to readings of 2 or 4. I suppose
that these "lengthy" EE readings relate to drive errors that will show
up periodically, and are not necessarily caused by poor polar alignment.

Q2. If I remember correctly, I would get a reading such as "A2 E -3". I
would assume that A1, A2, A3 and A4 refer to the direction in which the
drive is deviating from the guide star, or perhaps the direction of the
correction. But is it possible to know which of these designations
corresponds to RA or Dec, and therefore to ascertain the accuracy of
one's polar alignment?

Comment: It seems the ST4 tracking is a neat way of quantifying the
tracking accuracy of the drive, given a certain level of accurate polar
aligning. It allows me to assess the drive given variables such as the
orientation of my assembly, how carefully I counterweigh, and length of
exposure (which opens me up to flexure problem, and tripod sinking).
While viewing a guide star through an illuminated reticle will also give
me an idea of drive accuracy, I am enjoying the suspense of watching
those digits on the control panel light up.

Charles