Field derotator or Wedge?

Skyking159

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Apr 12, 2001, 10:31:55 PM4/12/01

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Hi, I have a LX 200 10" and I am going to do ccd imaging, the question I have
is which is better, wedge or field derotator? both cost about the same and do
the same ...my preference would be the derotator
any info would be great!
thanks
Rick

JFL

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Apr 12, 2001, 11:06:13 PM4/12/01

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I do almost only visual and, as strictly a personal opinion, I want a wedge.
Once adjusted, it only needs slight tweaking to keep objects in the eyepiece for
up to 30 minutes. You can certainly use a derotator, but there are also reason
why the best and smoothest tracking is with a wedge.

Skyking159 wrote:

> Hi, I have a LX 200 10" and I am going to do ccd imaging, the question I have
> is which is better, wedge or field derotator? both cost about the same and do

> the same ...my preference would be the derotator--

But now if you have a purse, take it, and also a bag; and if you don't have a
sword, sell your cloak and buy one.
Luke 22, 36

Jason Lewis

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Apr 13, 2001, 2:00:11 AM4/13/01

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Keep in mind that PEC does not work in Alt-Az. The derotator cannot be used
for objects near zenith. Check the Meade website or a MAPUG website for
details. Having said that, some folks appear to be using them with some
success.

Jason

See Astrophotos at http://www.nomoon.org

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"Skyking159" <skyki...@aol.com> wrote in message
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Michael A. Covington

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Apr 13, 2001, 10:31:47 AM4/13/01

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"JFL" <lyon...@value.net> wrote in message
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> I do almost only visual and, as strictly a personal opinion, I want a
wedge.
> Once adjusted, it only needs slight tweaking to keep objects in the
eyepiece for
> up to 30 minutes. You can certainly use a derotator, but there are also
reason
> why the best and smoothest tracking is with a wedge.

Amplifying that a bit... When you use a wedge, you are only running one
motor, and it is the one with PEC (periodic-error correction). Tracking is
very smooth. De-rotators work, but they require you to run both motors and
sacrifice some smoothness. Also, with a de-rotator you can't do
piggybacking. With a wedge, you can mount a camera piggyback on the
telescope and get wide-field photos at the same time you are taking your CCD
images.

--
Clear skies,

Michael Covington
Author, Astrophotography for the Amateur
(Now working on a book on computerized telescopes)
http://www.CovingtonInnovations.com/astro <><

Al Testani

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Apr 13, 2001, 11:52:46 AM4/13/01

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Does PEC run on one motor when in AltAz or is it turned off altogether in
that mode?

I'm trying to decide it I should buy another wedge for field work (and leave
the one on my pier in place nicely aligned) or put the money into a
de-rotator. This PEC issue may make the decision for me.

"Michael A. Covington" <see.www.covingtoninnovations.com.for.address@x>
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L. Aslan

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Apr 13, 2001, 3:27:21 PM4/13/01

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Hi Al,
There is no PEC in Altaz mode at all.
Hope this makes your decision easier.

Leo

See my page for some SuperWedge modifications I've made:
http://home.earthlink.net/~laslan/camerai.htm

Al Testani wrote in message ...

Al Testani

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Apr 13, 2001, 5:08:21 PM4/13/01

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Hi Leo,

Thanks for the information. Not the answer I was looking for but...

I checked out your SW modifications. Nice job. I decided to build ny own
wedge after I learned of all of the modifications I would have to make, as
you did, to the SW. If you're interested you can check mine out at:
http://pws.prserv.net/testani/wedge.htm

Now I am going to have to decide if I want to build another copy of my wedge
for travel purposes or buy a SW and make modifications like yours. I think I
have ruled out the de-rotator. I use STAR2000 guiding with my CCD setup and
I'm not sure the de-rotator is compatible with that either.

"L. Aslan" <las...@home.com> wrote in message
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Jeff Dillon

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Apr 13, 2001, 6:57:51 PM4/13/01

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On your website, you mention the Superwedge has "many known problems". I
just got one, and hope to use this spring. Can you elaborate?

thx

Jeff

"Al Testani" <ates...@NOSPAMattglobal.net> wrote in message
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Michael A. Covington

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Apr 13, 2001, 9:11:47 PM4/13/01

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"Jeff Dillon" <jef...@fidalgo.net> wrote in message
news:98719916...@localhost.fidalgo.net...

> On your website, you mention the Superwedge has "many known problems". I
> just got one, and hope to use this spring. Can you elaborate?

I, too, would like to know. I'm using one quite contentedly. The only
change I made was to slightly enlarge the holes to make it easier to put the
telescope on it.

Al Testani

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Apr 13, 2001, 11:23:54 PM4/13/01

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This link:
http://www.mapug.com/AstroDesigns/MAPUG/WedgMods.htm
has many articles of problems, modifications, and solutions. When I was
researching which wedge to buy, this set of information steered me away from
the SuperWedge.

Other information on alternative wedges which also describe some of the SW
problems (of course) are:
http://members.aol.com/planclos/index/mettler.htm
http://www.skyvalleyscopes.com/mettler.htm
http://home1.gte.net/kmilburn/page2.html

You can decide for yourself if I was too strong in saying "many known
problems" .

"Michael A. Covington" <see.www.covingtoninnovations.com.for.address@x>
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JEPobs

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Apr 15, 2001, 11:39:47 PM4/15/01

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Hi,

If you are interested by the CCD imaging with the Meade Field Derotator you can
visit my special web site about that.

CCD ALTAZ : http://members.aol.com/ccdalt/

I wait your reply.

See you soon.

Florent Poiget
President of POLARIS Association, France