Re: Observatory Mounts
- From: canopus56 <canopus56@xxxxxxxxx>
- Date: Wed, 12 Sep 2007 11:42:05 -0700
On Sep 11, 4:07 pm, Macro <marcus.je...@xxxxxxxxx> wrote:
What observatory mounts could be used for a Dobsdonian that could be
computer controlled?
Some of this may go over your head; but just file it away for future
reference as you look at mount options. If you go the route of
converting your Dob mounted Newt to a German equatorial mount (GEM),
you'll need the info in the future.
Newts can be removed from their alt-az boxes and converted for
mounting on a GEM.
WRT German equatorial mounts and a 10" Newt, I using a Synta EQ6 -
which is the manufacturer's name for Orion's branded Altas EQ6 mount.
( http://www.skywatchertelescope.com/EQ6SkyScan.html ) This is a
lower cost-end mount with good tracking ability. This mount can be
computer controlled through a laptop by most planetarium programs
through the ASCOM open source telescope interface. (
http://ascom-standards.org/index.html ) In general, ASCOM emulates a
Celestron Nextstar 5i, 8i or Ultima - which can be used by most
planetarium programs. The only hardware add-on usually is a Belkan
USB to serial converter. ( http://www3.shopping.com/xPO-Belkin-USB-Serial-Portable-Adapter-F5U409-CU
)
The 10" Newt did not auto-target properly out of the box using the
Syntax EQ6 mount. An additional extra-heavy duty mounting bar ($175)
had to be purchased to reduce tube and mounting bar flexure that
prevented good perpendicular alignment. The mount will probably work
out of the box with a lighter 8" Newt and is very popular for
astrophotography using relatively lighter 5 1/4 to 6 inch refractors
because of its good tracking ability. If you buy this mount, make
sure you purchase only a newer model with a hand-controller with
version 3.10 software or higher. Used Syntax EQ6s mounts with
pre-3.02 handcontrollers can not be software upgraded and have a
defective hand-controller software design (non-synching dedicated
communications mode). The pre-version 3.02 hand-controller cannot be
used effectively when connected to a laptop program.
In general, Newts take more aligning effort and skill to properly
remove perpendicular error and to keep the scope properly aligned - as
compared to SCTs or refractors. This is because the Newt mirror is
tilted slighty off-axis relative to the physical tube. The objective
in SCTs and refractors are not tilted and the optical axis and the
tube exterior are both parallel to the optical axis.
Celestron's analgous computer-controlled product is the more expensive
CGE mount. ( http://www.celestron.com/c2/product.php?CatID=16&ProdID=93
) I am not personally familiar with that GEM mount but have heard
good comments about and seen good performance of this mount at star
parties. I am not sufficiently familar with Meade products to identify
their GEM version.
There is a price vs. tracking error trade off. Spend more money - get
less tracking error. That's an economic selection that you have
make. To some extent, modern low-end autoguiding mounts can
adequately compensate for tracking error during astrophotography to a
degree that makes them a performance alternative to higher-end
mounts.
For auto-guiding, a Guidedog USB autoguiding adapter is added to the
Synta EQ-6 (or other GEM) mount. ( http://www.barkosoftware.com/GuideDog/
)
This autoguiding product is not directly compatible with autoguiding
feature of Meade's imaging software, e.g. Envisage. Third-party
freeware add-ins will let you autoguide on-axis through the Meade
software - ported through the ASCOM interface and the Guidedog USB
adapter. Typically, a second off-axis scope and a separate web camera
are used for autoguiding Newts, rather than on-axis guiding.
- Canopus
.
- References:
- Observatory Mounts
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