Equatorial Platforms - Advice Needed
James M. Cate
Hello,
I would appreciate getting suggestions and advice
regarding the use of an equatorial platform with a
medium-size Dob (mine is the 16-inch Meade). My
understanding is that these systems is that they can be
used with any Dob within the size-weight capabilities of
the particular unit to provide tracking with sufficient
accuracy to keep objects within the field of view for a
period of time, up to about 15- 30 minutes, but not
sufficient accuracy for DSO photography. There seem to be
quite a wide variety of designs, with some units having
dual axis control, etc., and some being provided in
semi-finished form for under $500 or so. - - Any advice
regarding good sources, models, and important features
would be appreciated. If there are any that could be used
for more accurate tracking, as with an off-axis scope, or
go-to computer control, I would like to know what's
involved, whether such a system is available as an
integrated system with all components included (as opposed
to: you could get such-and-such parts from sources such
asA, B, or C, put it together yourself, and maybe get
great results. - I don't have that much available free
time.).
Thanks for any information.
Jim
Bill G.
www.equatorialplatforms.com
Bill G.
"James M. Cate" <jim...@pdq.net> wrote in message
news:C745FB7478444372.7D2ABCC2...@lp.airnews.net...
Chris L Peterson
>I would appreciate getting suggestions and advice
>regarding the use of an equatorial platform with a
>medium-size Dob (mine is the 16-inch Meade). My
>understanding is that these systems is that they can be
>used with any Dob within the size-weight capabilities of
>the particular unit to provide tracking with sufficient
>accuracy to keep objects within the field of view for a
>period of time, up to about 15- 30 minutes, but not
>sufficient accuracy for DSO photography.
This is generally true. The problem with photography isn't so much the accuracy
of the drive (which can be made arbitrarily good), but with the fact that guided
imaging requires 2-axis tracking. There are equatorial platforms with that
capability, and they are used to get first-rate astrophotos. Have a look at some
of the things Del Johnson has done with his Dob on a dual-axis platform.
> There seem to be
>quite a wide variety of designs, with some units having
>dual axis control, etc., and some being provided in
>semi-finished form for under $500 or so. - - Any advice
>regarding good sources, models, and important features
>would be appreciated.
<Shameless plug...>
A friend of mine, Art DeBrito, has recently established a small company to
produce inexpensive equatorial platforms. He's got a nice design, and one of our
club members is happily using this platform with his 16" Meade Dob (a monster of
a scope). You can check out his stuff at http://eqplatforms.0catch.com/ , and
call him if you have any questions. He loves talking this stuff.
If you want to image, check out the Osypowski platforms
http://www.astronomy-mall.com/regular/products/eq_platforms/pg1.htm . But be
warned: these platforms are in the same price range as decent GEMs.
_________________________________________________
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
Robert Cuberly
"James M. Cate" <jim...@pdq.net> wrote in message
news:C745FB7478444372.7D2ABCC2...@lp.airnew
s.net...
> Hello,
> I would appreciate getting suggestions and advice
> regarding the use of an equatorial platform with a
> medium-size Dob (mine is the 16-inch Meade). My
> understanding is that these systems is that they can be
> used with any Dob within the size-weight capabilities of
> the particular unit to provide tracking with sufficient
> accuracy to keep objects within the field of view for a
> period of time, up to about 15- 30 minutes, but not
> sufficient accuracy for DSO photography.
Hi Jim and all,
If you are tool-handy and like doing woodwork there are
apparently some good kits for the home builder that will work
well if built properly. I recommend if you go that route that
you do your homework and find good drive motors and controllers.
I would like to correct a few of your misconceptions. I bought
one of Tom Osypowski's Equatorial Platforms over 6 years ago and
have used it extensively all over half of this country. More
than a few here on saa have looked thru my improved 15"
Obsession at star parties at over 500x and enjoyed its steady,
sharp images. I often use more magnification. You must perform
star drifting to get it into really accurate alignment just like
a GEM mount. It takes a while to get it right on the money if
you are being picky, but a quick 20 second ball-park
approximation does fine for a night outside with friends and
public. If you ever decide to go the more expensive route you
will find Tom builds a high quality well designed and made
product. Each one is really totally custom made for the desired
latitude and your needs. Mine matches the build quality of my
Obsession. The electronics are first rate. There is an input
for an autoguider input so you can indeed do long time
exposures--see his site for fine examples of other owner's
astrophoto work as well as his own. There is no image rotation
problems with an Equatorial Platform. Weight of the driven
scope is not a problem either. Tom uses (or did use) the same
high torque dual parallel driven stepper motors on his drives for
my size mount as for the bigger 30" scope mounts. I use one deep
cycle RV battery for all my dew heaters, lights and drive system.
I believe my drive uses about 1/4 amp at fast speed, which is
pretty slow, and 1/10th amp at normal tracking rate. I reset my
table position often to keep the dob base more horizontal for
convenience, but it will track for about one hour (15 degrees) if
I don't. I have made 45 minute film exposures. I originally
ordered mine with the single axis drive for a 15 -18" dob. I
later had him install the 2nd axis drive. When I buy a larger
Obsession someday I will buy another EP from him to fit it. I
do not need the go-to capability as much as I like the capability
of prime focus film exposures at f/5.15 with a Paracorr. I have
also occasionally stuck one of my smaller portable dobs on top
the EP for quick high power planetary viewing and on several
occasions have set a Bogen tripod mounted Canon EOS A2 with
camera lenses on it for comet and star cloud/constellation time
exposures with great success.
Best wishes,
Bob Cuberly
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Del Johnson
information is all wrong. I don't mean to be unpleasant but a little
homework on your end will go a long ways. FYI, these platforms are good for
80+ minutes between resets and are excellent for astrophotography.
http://astronomy-mall.com/regular/products/eq_platforms/
Del Johnson
"James M. Cate" <jim...@pdq.net> wrote in message
news:C745FB7478444372.7D2ABCC2...@lp.airnews.net...
>
> Hello,
>
> I would appreciate getting suggestions and advice
> regarding the use of an equatorial platform with a
> medium-size Dob (mine is the 16-inch Meade). My
> understanding is that these systems is that they can be
> used with any Dob within the size-weight capabilities of
> the particular unit to provide tracking with sufficient
> accuracy to keep objects within the field of view for a
> period of time, up to about 15- 30 minutes, but not
> sufficient accuracy for DSO photography.
>
> Jim
James M. Cate
Chris L Peterson wrote:
>
> On Sat, 23 Mar 2002 09:50:17 -0600, "James M. Cate" <jim...@pdq.net> wrote:
>
> >I would appreciate getting suggestions and advice
> >regarding the use of an equatorial platform with a
> >medium-size Dob (mine is the 16-inch Meade). My
> >understanding is that these systems is that they can be
> >used with any Dob within the size-weight capabilities of
> >the particular unit to provide tracking with sufficient
> >accuracy to keep objects within the field of view for a
> >period of time, up to about 15- 30 minutes, but not
> >sufficient accuracy for DSO photography.
>
> This is generally true. The problem with photography isn't so much the accuracy
> of the drive (which can be made arbitrarily good), but with the fact that guided
> imaging requires 2-axis tracking. There are equatorial platforms with that
> capability, and they are used to get first-rate astrophotos. Have a look at some
> of the things Del Johnson has done with his Dob on a dual-axis platform.
_______________________________________________
Thanks to everyone for the helpful advice. I am probably
not going to invest in one of the high-end, two-axis
systems at the present time.
Speaking of Del Johnson, I'm posting, below, some comments
he sent me by e-mail, in case anyone want's further
information.
Jean-Marc Becker
your
> information is all wrong. I don't mean to be unpleasant but a little
> homework on your end will go a long ways. FYI, these platforms are
good for
> 80+ minutes between resets and are excellent for astrophotography.
>
> http://astronomy-mall.com/regular/products/eq_platforms/
>
>
James M. Cate
Platform web page to which you are referring. - Searching
for a FAC on this ng, I don't get a response. The link
given in your note is to a commercial site of a supplier
of such EQ platforms.
Jim Miller
has numerous pictures of long duration photography. how long do you expect
your exposures to take?
jtm
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"James M. Cate" <jim...@pdq.net> wrote in message
news:2A597D93D34EF2DD.7FF73AA2...@lp.airnews.net...
Shneor Sherman
long-duration photography. I have has one of his "compact" platforms
for 5 or 6 years, and my 18" tracked well seven degrees south of the
latitude it was built for (with the help of a piece of 2x4).
Clear skies,
Shneor Sherman
"Jim Miller" <j...@NOSPAMjtmiller.com> wrote in message news:<uafe817...@corp.supernews.com>...
James M. Cate
Jim Miller wrote:
>
> www.equatorialplatforms.com
>
> has numerous pictures of long duration photography. how long do you expect
> your exposures to take?
>
> jtm
Something like 5 - 6 hours, since I will be using 64 ASA
film for increased resolution.
Jim
(And, if it wasn't so close to April 1, probably more like
10 - 30 minutes.)
Jim Miller
work are frequently on TomO's platforms.
First class workmanship.
jtm
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> probably more like 10 - 30 minutes.
Del Johnson
platform drive. Scanning and stacking the negatives allows one to go as
long as one likes.
Del Johnson
"James M. Cate" <jim...@pdq.net> wrote in message
news:B20061ACC6145A93.0E6FFD4C...@lp.airnews.net...