[AZ-Observing] Re: Troubles on the Pole
- From: gene lucas <geneluca@xxxxxxxxxxxxx>
- To: az-observing@xxxxxxxxxxxxx
- Date: Sun, 25 Feb 2007 14:16:12 -0700
I think this is incorrectly stated (in the manual). We can live with
the OTA not pointing in a direction "perpendicular" to the declination
axis; in fact, given the way that the OTA and finders, etc. are usually
mounted, it is probably inevitable. (The OTA still describes circular
paths in the sky.) Furthermore, it should be relatively simple to
correct the OTA pointing (mounting) error (to a tolerable level),
assuming the operator is willing to make the necessary tests and
adjustments (to the saddle assembly on a GEM). IF the mounting carries
the OTA around the declination axis TRULY PERPENDICULAR to the RA, then
there would be NO pointing error.
What creates the "bad" error (built-in mechanical error that is
difficult to correct) is the declination axis NOT being perpendicular to
the RA axis. In the definition in the manual, the manufacturer is not
"owning up" to the inevitable errors inherent in making commercial grade
mountings, and not providing any means to shim or adjust/correct that
machining/assembly error (to a tolerable level). This has nothing to do
with the basic mount design, GEM or fork (putting aside the mechanical
arrangements, weight balancing, and inherent differences in flexure).
It has everything to do with how much time and money you have to throw
at the problem (in design and manufacturing). That is not to say that
million-dollar mounts can't be improperly installed !!
IMHO, If the CGE computer can compensate for the (inevitable) residual
mechanical errors, then it is up to the observer to learn the "cone"
procedure and put it into use.
Gene Lucas
(17250)
Jimmy Ray wrote:
>...
>"Cone" as defined in the manual:
>"it calculates and compensates for "cone" error inherent in all German
>equatorial mounts. Cone error is the inaccuracy that results from the optical
>tube not being perpendicular to the mounts declination axis."
>
>[my earlier stuff snipped, to keep the net nanny happy....GL]
>
>
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