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Re: [APML] Re: [Astrophotography] Auto Guiders
Hello everybody,
I too missed the original post, but since this subject has come out, I take
a chance to pose some questions:
1) I was looking into a webcam autoguiding system (partly
do-it-yourself-made) with a guidescope: I would need a laptop, of course,
but it would be a very cheap way of getting started witha autoguiding. I
only have doubts as to how the faintest usable stars. Anybody have any
experience/pointers/opinions on this?
2) As a matter of fact, I have an SCT OTA, which I read is a pain the neck
to guide with a separate guidescope. Do I have to give up my hopes and
stick with an off-axis guider?
Thanks
Emmanuele
At 10.11 11/09/2002 -0700, you wrote:
>Hi Nelson,
>
>I missed the original post, so I'm sorry this is late.
>The 201s chip is not cooled, this is why it's not as
>sensitive as the ST-4. I have used both of these and I
>liked the 201 better. Here's why:
>
>1. The 201 is completely self contained. The ST unit
>has a separate control box that I found to be a pain
>to deal with in the dark.
>
>2. The 201 retains its settings from night to night.
>The ST-4s settings need to be re-entered after every
>power up.
>
>3. The 201 is operated by a single button on the back
>of the unit. I found this much more convenient than
>having to locate buttons on a separate control box.
>
>4. The 201 is extremely light, and requires little if
>any counter balancing.
>
>Having said that, you need to understand that focus
>issues are critical when dealing with the 201. You
>will need to be able to easily repeat your focus from
>night to night, and shot to shot. I use the Taurus
>Tracker III which does make it easy. I do guide
>off-axis with a LX200. It's easy once you have the
>proper tools and experience.
>
>Read what Herm says below and keep in mind that there
>may be some equipment issues depending on what you
>use. I would not recommend the 201 to you unless you
>will use a quality off axis guiding system. Through
>the TTIII, I do NOT see out of focus blobs. I can
>easily get in-focus stars. This is a BIG reason why I
>can use the 201 with my equipment.
>
>I do think part of the 201's bad reputation has to do
>with the fact that many tend to try it as their first
>autoguider. I could not use my 201 for the first 18
>months I had it because I did not know how critical
>the focus issue really is. Once that is dealt with
>it's a piece of cake.
>
>Good luck,
>Alan
>
>
>--- Herm <hermperez@worldnet.att.net> wrote:
> > Sensitivity can be dealt by using longer exposures,
> > probably safely up to
> > 10 seconds or so.. while an ST4 will easily guide
> > with 1 second exposures.
> > Longer exposures will allow your mount to drift too
> > much. Since sensitivity
> > is low, sharp focus is extremely critical.
> >
> > Simultaneous corrections can be a problem with
> > certain mounts.. usually not
> > an insurmountable problem if you do a careful polar
> > alignment. 99% of your
> > corrections will be in the RA axis anyways. Losmandy
> > mounts WILL work with
> > a 201XT as long as the x axis of the 201XT
> > corresponds to RA.. the losmandy
> > will just ignore DEC corrections until no correction
> > is issued on RA.
> > Obviously this is not a problem with Meade mounts.
> >
> > The st4 will compute the centroid position of a blob
> > of light.. thus it can
> > guide extremely accurately on a distorted star or
> > out-of-focus blob (even
> > guide on the head of a comet). This feature is what
> > really makes the ST4 so
> > well loved. To compensate for this, make sure the
> > 201xt is precisely
> > focused to make the star as small as possible on the
> > ccd chip.. avoid using
> > a 201XT with an off-axis guider and an sct..
> >
> > SCT off-axis stars are distorted blobs (usually
> > crescent moon shaped), the
> > 201xt has difficulty locking on these.
> >
> > I would recommend you use the 201xt with a refractor
> > guidescope, preferably
> > 80mm and up so it delivers sharp bright stars.. if
> > you carefully make a
> > mark on the focuser you may never have to refocus it
> > again for a 201xt. You
> > cant use a guidescope on an sct due to mirror flop
> > issues, so avoid an
> > 201xt for an sct.
> >
> > Also note that the command flowchart tree that meade
> > includes with the
> > 201xt is wrong, there are correct ones avaialble in
> > the web.
> >
> >
> > biggsnj@cs.com wrote:
> >
> > > Does anyone use an autoguider for their long
> > exposure photograhy? SBIG has discontinued their
> > >ST-4 Autoguider, the only other stand alone unit I
> > have found is Meade's Pictor 201XT. Has anyone >used
> > the Meade unit? Would you recommend it? I'm on a
> > budget.
> > >
> > >Nelson Biggs
> >
> > Herm
> > Astropics http://home.att.net/~hermperez
> >
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>
>
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