I erased the previous PEC training, so I'm starting from scratch to train the RA
drive for PEC. I'm no longer really interested in the PEC curve as such. It would
be interesting to get one, but by using autograb and slide show, I can get a
pretty good idea of whether the PEC training was good by observing the slide show
results. After I use autoguide (You mentioned selfguide below, but did you mean
selfguide? It seems like autoguide would be more appropriate.), I then create
about 96 exposures of three seconds in length. Given the download time, that
covers almost 10 minutes of time. When I play them back, I can see if there is
left-right movement of whether the star field stays steady. If it stays steady,
then all is OK.

I was able to achieve that once last night, but some weird things happened and I
had to erase that training. I'm doing it again tonight, but I got a late start
and probably will stop shortly. The fact, that I got a good PEC training last
night is encouraging. I took a 2 minute exposure of M57 with no guiding and got
pretty close to round stars. I then shot some other shorter exposures and my
drag/shift problem had disappeared. This of course says all my problems have been
to what I guess was an accidental erase of the PEC--how that happened I haven't
got the foggest.


> In a message dated 7/20/01 3:44:03 AM Eastern Daylight Time,
>
> <<
> I'm PEC training in the ST-7's autoguide mode, but it strikes me that
> one should probably do this with a pretty bright star, short exposure,
> and exposing in the tracking chip. Downloads via the tracking chip are
> quick and should be helpful in keeping up with potentially many or
> large quirks in the worm gear. Comments?
> >>
>
> Wayne,
>
> I forgot to suggest something to you. Sorry. I think what you would be best
> doing, for your particular problem, is to first, yes, use self guide. That's
> correct. And probably, to get a decent pattern in the graph that won't be so
> large as to hide the irregularities, is use perhaps one second update times.
>
> But the part I should have mentioned was, before starting the self guide,
> TURN OFF ALL CORRECTIONS! That way, even though it's going through the self
> guide, it will show us what the self guide is TRYING to correct for!
> Otherwise, your graph will show errors after having already corrected to some
> degree.
>
> Doing it and actually allowing the corrections to take place will probably
> work to a good degree, but assume, for example, that the camera is over
> correcting while guiding. That would mean that the next 'correction' would
> actually have to correct for the over correction it just made, as well as
> whatever mechanical error you have.
>
> Aslo, I'd say to use as dim of a star as is practical for the self guide.
> This does help, to a degree, in reducing the effects of bad 'seeing'. Not a
> major difference, but we want to know as much as possible about the
> mechanical error and eliminate as much as possible, the effects of any other
> causes of guide. Under normal, true self guide, I'd say that your reasoning
> is right on. That's how I self guide... mostly. <G>
>
> The graph, then, would show us exactly what took place mechanically, via the
> graph showing us what it *tries* to correct for.
>
> Hope this helps. Sorry for the afterthought.
>
> Bruce Johnston
>
> Bruce Johnston Computing
> <http://members.aol.com/bjohns7764>
> Internet home for "SuperFix" and "MegaFix" image processing software.
> Personal page: <http://members.aol.com/ccdastro>

--
Wayne T. Watson (121.015 Deg. W, 39.262 Deg. N, 2,701 feet)

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