Re: Scope accuracy/limiting mag/RealSky

Robert Burns Nov 20, 2002

Thanks to Bill and Jeff for the info.
It's hard to play with MEC until I get a Tangent style box. (Also,
the link to the latest version of DOS guide on
http://www.projectpluto.com/scope.htm#MEC seems to be broken.)
Anyway, from reading the instructions on the above page, I understand
that I would NOT be limited to a small set of alignment stars but
could align on any stars or objects that I could identify -- true?

Also -- I think I know the answer to this, but I'm grasping -- can
the MEC data created by the alignment process(as I understand the
process) be then utilized by the Windows version or am I stuck in the
DOS version if I want to use MEC? I ask, because in the name of
simplifcation, I want to use the same laptop for auto-guiding and
image acquistion and I need a OS that at least resembles multi-
tasking. Besides, there is no DOS version of my camera control
software available.

Also#2 -- and sorry to sound like a pest -- when you say simply the
procedure, does that mean incorporate MEC into the Windows version or
make the DOS/MEC version a little more user friendly?

Also#3 - - Given what I'm trying to accomplish, (center of FOV
identification to with a couple of degrees), in your opinion would I
be better off abandoning the move to a tangent box, instead bite the
bullet and start gearing to Bartelize my G-11? (Pardon the missmash
of metaphor.)

Robert Burns

--- In guide-user@y..., Bill J Gray <pluto@p...> wrote:
> Hi Robert,
>
> I've heard from one gent with 8192 count/revolution encoders
and a
> Dob mount who, after a bit of playing with MEC, got pointing
> accuracy of a few arcminutes. I dunno how well that represents
> "general" accuracy, but I'd expect it to be about right. He _did_
> have to acquire a couple of dozen stars, as I recall.
>
> I suffer from a lack of data, because not many people have
> actually used MEC. Give it a shot, and you'll see why: it's
> ugly to use. Something I will be remedying...
>
> As Jeff Medkeff mentioned, use of GSC-ACT doesn't help here.
> The only improvement you get with GSC-ACT is that the positions
> are adjusted slightly, to remove systematic errors. For details:
>
> http://www.projectpluto.com/gsc_act.htm
>
> No stars were added or removed, and no magnitudes were
> adjusted. (I started a project to recalibrate the magnitudes, but
> didn't have a great deal of success.)
>
> "... I really don't want to haul USNO A2 outside." In theory,
one
> way around that would be to filter out the fainter A2 stars, and
store
> a subset of A2 on your hard drive. I did some of the math for this,
> long ago, computing how many bytes would be needed to get to
> a certain magnitude:
>
> http://www.projectpluto.com/a2.htm#filtered
>
> However, I don't have software to perform the necessary step of
> creating a "filtered" A2.
>
> A correction to my previous post: I suggested that Alan Cahill
> (and anyone else so inclined) could copy RealSky, in part or
> in whole, to a subdirectory on a hard drive, but would then need
> to use the SUBST command or equivalent to make that subdirectory
> "look" like a drive. I was wrong. All you need do is to edit the
> file ENVIRON.DAT, in the Guide directory on the hard drive,
> and look for a line resembling this one:
>
> DSS_DIR=d:\
>
> Change it to point to the directory on the hard drive where
RealSky
> (or DSS) data is installed, so it looks something like this:
>
> DSS_DIR=c:\realsky\
>
> No playing around with drive letters via SUBST is then required.
>
> -- Bill