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Re: [APML] Re: [Astrophotography] Auto Guiders
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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