Re: [APML] Drift Alignment with STV

[Matt BenDaniel <matt@starmatt.com>]

Don,

There's always more than one way to skin a cat...

Tonight I used the STV's tracking mode to drift align. You can disable the corrections to see the trend. (After you adjust the alt or az, you can briefly enable the corrections to re-center the graphs.) This is essentially the same method I use with the ST-4.

Matt

At 05:31 28-02-03 -0800, westergren wrote:
>Matt,
>
>The info Steve gave you is right on.  I can add a tip in using the STV for
>drift align.  I set the focal length to a fraction of the actual scope fl (I
>set 25mm for the E-finder 100 mm fl).  The reason is that the plot of the
>drift in the Monitor Drive Slow mode is 50 arc seconds high.  You have to
>have a lot of drift before it shows up on the graph.  By setting the fl to
>1/4, or 1/10 the actual fl, you magnify the plot and get much more
>sensitivity.
>
>One more thought on using the E-Finder with the STV.  The first STV exposure
>establishes the reference pixel position of the star.  Subsequent exposures
>are used to calculate the arc second error or movement.  With the short fl
>of the E-Finder, I almost always end up with a very large initial error.
>That can throw the graph off scale sometimes with the E-Finder set as I
>described above to magnify the graph.  I get a lot less initial error offset
>with a longer fl, like using my regular scope at fl=530 or fl=1620.  I
>prefer to use the scopes (with OAG for guiding) rather than the E-Finder for
>both guiding and drift align.  I factor the fl by 1/4 or 1/10 when I drift
>align with the scope.  Just be sure to remember to set the fl back before
>you calibrate and guide.
>
>Don
>
>
>> Hi Matt---"calibrating" allows the STV software to determine the RA and
>DEC corrections to be applied to respond to an error. These corrections do
>not depend on the STV axes being congruent with the mount RA and DEC. For
>drift alignment I believe the STV axes should be congruent to the mount
>axes. There's a few URL's about with "How To's"  for drift alignment with
>the STV or other CCD's. Here's one:
>> http://www.melino.org/astronomy/polar_align.html
>>
>> I believe I've seen others referenced on the SBIG STV Yahoo Group.
>>
>> Steve
>>
>> Matt BenDaniel wrote:
>>
>> > I finally bought an STV. I plan to mount it with an eFinder on a
>dovetail with a Losmandy DCM. I think this should orient the chip
>orthogonally to the mount's RA/DEC axes, although perhaps it may be a degree
>or so off. I used to do drift alignment with a reticle eyepiece, then
>started doing it with an ST-4 last year. I think the mode to use on the STV
>is Monitor Drive Slow. If the STV is calibrated, should the X and Y axes
>correspond precisely to RA and DEC?
>> > --
>> > Matt BenDaniel
>> > matt@starmatt.com
>> > http://starmatt.com

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