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Diagnal and VPCA on LX200ACF

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#1 SamFurkory

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Posted 25 January 2013 - 01:08 AM

Hi, guys.

I'm a newbie to this forum. Hope somebody knowledgeable here can help
me to clear clouds above my head.

Does gear train above give OTA more room for rotation than 45 degree?

I'm planning to buy an LX90ACF or an LX200ACF. Catalog and instruction
manuals are downloaded from Meade site. But manuals say the gear train
of T-adapter or VPCA, Variable Projection Camera Adapter and a camera
limits the vertical rotation of OTA to 45 degree. It looks the train hits the
base of the fork mount. With the limit on rotation, if I'm right, celestial objects
above 45 declination fall outside of the imaging field in the equatorial mode.

The recommended or "Base hitting" accessory train is:
EP holder(#07182) -> VPCA(#07348) -> T-Mount -> Camera

The "Base swaying" accessory train is:
EP holder(#07182) -> Diagonal(#918) -> VPCA(#07348) -> T-Mount -> Camera

The inserted diagonal extends the distance between EP holder and VPCA.
My concern is, extended distance may go beyond the sliding adjustment of
VPCA.

To put another way, what to do to image objects higer than 45 degree in
declination?

Thank you, in advance.

#2 deepwaterescue4u

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Posted 25 January 2013 - 06:09 AM

I am still very new with very limited knowledge on all the different ways to change the optic train, I know that adding a wedge would be one way to solve that problem, I am sure there could be other ways and someone with more knowledge will have to answer that part... :)

Terry

Meade LX200 14" ACF GPS
Meade 4 speed micro focuser
Milburn Wedge
Panama City Florida

Live long and prosper


#3 MistrBadgr

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Posted 25 January 2013 - 03:24 PM

One way is to catch them when they are at a different height. like later in the night or early morning hours.

Bill Steen
Bill Steen, Sky Hunters' Haven Observatory, Broken Arrow, Oklahoma

#4 SamFurkory

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Posted 27 January 2013 - 09:45 AM

Really quick reply. Thanks, Terry and Bill.

I could be entirely wrong with how LX200 operates in EQ mode since I am a very beginner.
Let me illustrate how I think things go. Any correction is appreciated. My favorite Cat’s eye
nebula is at about 66 degree declination. It rotates around the North Pole with the radius
of 90 – 66 =24 degree. The wedge on the tripod gives proper tilt to LX200. The fork arms
of the mount are aligned precisely to the North Pole. The OTA slews upward to the Pole.
But the slewing stops at 90 – 45=45 degree from the North Pole about 20 degree short from
Cat’s eye nebula when T-adapter and DSLR on the back of OTA hit the base of the mount.
Then the nebula never comes into the view of camera although it is always above the horizon
at night all year round; the telescope is located at around 38 degree latitude.

mmmm,,,,. I have a bad feeling. And it often comes true. Diagonal and VPCA don’t work
together. If they would do, should’ve been so written in the instruction manual to get around
the rotation limit on VPCA etc.

I’m expecting comments from the owners of VPCA.

Sam

#5 gspie

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Posted 27 January 2013 - 10:00 AM

I have an LX200 classic, and with a CCD attached to the back, I too am limited as to 'how high can I fly'. If I wantto image anything over about 56-degfrees DEC, I need to piggy-back mount another telescope atop of the LX200 -- then, with no camera at the back of the LX200, I can slew as high as I like.

The unfortunate thing about fork-mounted OTAs -- the slew limit is tight when you add stuff to the optical train.
LX850 with 10" ACF OTA and Takahashi FS 60C OTA -- SBIG STT-8300M CCD with FW8G-STT Self Guiding Filter Wheel and SBIG AO-8 Adaptive Optics -- Camera Control and Image Calibration with Maxim DL/CCD Pro, Image processing with PixInsight, and final composition with Photoshop CS5

http://home.comcast....ie/astroweb.htm

#6 SamFurkory

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Posted 28 January 2013 - 10:25 AM

Hi, Glen.

I see we can’t get around the constraints of fork mount. Thank you for the advice. Your wide field setup is “mind-blowing” to me. LX200 is the guide scope of 60mm refractor on its back. Looks like daddy telling his baby on his shoulder with camera where to shoot. :)

Thank you again.

Sam





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