New MEADE scope: RCX400 RITCHEY-CHRETIEN

George Normandin wrote:



Bill, et al:

I own a 10-inch OGS RC Cass that does not have secondary focus, and I've
used a 20-inch OGS RC Cass (Kopernik Obs www.kopernik.org) for about 13
years that does.

It's been a while since I was back there. When did they upgrade from
the 12.5"?


George Normandin

"Richard F.L.R. Snashall" wrote

used a 20-inch OGS RC Cass (Kopernik Obs www.kopernik.org) for about 13
years that does.


It's been a while since I was back there. When did they upgrade from
the 12.5"?


Richard,

The 12.5 Tinsley is still in the north dome. In 1987 or so a C-14/8-in
Schmidt Camera went into the south dome. There was a major upgrade in 1993
that included building another dome that has an OGS 20-in F/8 RC Cass on a
GoTo OGS mount. Somewhere along the way Kopernik also got a 6-in F/12 Astro
Physics refractor, a C-8, a Meade 10-in SCT, and a few Dobs. Now if they
could just get some good eyepieces.....

George Normandin

wrote

.....
What appears disconcerting is there are no screw-/bolt-holes appearing
on the
front and rear cells in the photos, so how is one supposed to mount
other stuff
on the OTA (without opening it up and drilling/tapping mounting holes)?

Duct tape.

George Normandin

wrote

What about cool-down time?
No mention of forced cooling?

Chris,

As others have already said, there is a fan. Also one reason for the
composite tube is to eliminate expansion/contraction as the temp changes.
This helps with holding focus and cutting tube currents. The other reason I
assume is that RC's need a stronger tube than other designs because they are
more sensitive to mis-collimation from tube sag.

They obviously aren't assuming an observatory situation since they are
offering an even more expensive tripod.

I must be getting old or something but I can't imagine taking a 16-inch RC
'to the field'. I know a physically fit woman who has problems setting up
her Meade 10-inch SCT and even some males find the 12-in SCT difficult to
deal with - especially around 2:30am when it's time to take the scope
inside.

Why not a proper pier? No profit margin on something so obviously
simple?

With all the electronics onboard won't it become rapidly obsolescent
(or spend ever increasing amounts of time at the factory being fixed at
the customer's expense). They'll have to have a Yahoo Group where they
can all bemoan Meade's short-comings and short-sightedness.

I wonder whether the electronics will be user replaceable/upgradeable?
Otherwise it will just become a white elephant.

If this scope's optics are as good as advertised I would think that Meade
will sell a lot of tube assemblies to guys with premium mounts from Astro
Physics, Bisque, Mountain Instruments, etc. My MI-250 mount will hold a
14-inch Cass but my wallet can't provide the $18k for a OGS or RCOS 14-in RC
Cass tube.
For the price I may accept some compromise if the Meade's performance is
somewhere between a SCT and a "classical" RC.

No power, no telescope. So you won't be able to take advantage of
future power blackouts! ;-)

Blackouts? That's why Dobs, paper star atlases, and beer were invented......


One thing did concern me about the specs..... The primary is glued into the
tube with no possibility of adjustment and I'm not sure how you get it out
for re-coating. My experience with two RC's is that the main collimation
problem is with the primary, not the secondary. In 7 years I've never had to
move the secondary in my OGS 10-inch RC, but the primary needs adjustment
every year or so. Although I've seen SCT's go 10 years I generally think
that their mirrors need re-coating after 6 to 7 years.

George Normandin

George Normandin wrote:


The 12.5 Tinsley is still in the north dome. In 1987 or so a C-14/8-in
Schmidt Camera went into the south dome. There was a major upgrade in 1993
that included building another dome that has an OGS 20-in F/8 RC Cass on a
GoTo OGS mount. Somewhere along the way Kopernik also got a 6-in F/12 Astro
Physics refractor, a C-8, a Meade 10-in SCT, and a few Dobs. Now if they
could just get some good eyepieces.....

Yup... it's been awhile. Glad to see you've had significant benefaction
since then.

Didn't Gould Optical take over an eyepiece manufacturing business a
ways back? Wonder if they could have donated some...

Excellent point George. Sometimes it's the simple details that elude
even the best engineers...

George Normandin wrote:

One thing did concern me about the specs..... The primary is glued into the
tube with no possibility of adjustment and I'm not sure how you get it out
for re-coating. My experience with two RC's is that the main collimation
problem is with the primary, not the secondary. In 7 years I've never had to
move the secondary in my OGS 10-inch RC, but the primary needs adjustment
every year or so. Although I've seen SCT's go 10 years I generally think
that their mirrors need re-coating after 6 to 7 years.

George Normandin

"Richard F.L.R. Snashall" wrote

The 12.5 Tinsley is still in the north dome. In 1987 or so a C-14/8-in
Schmidt Camera went into the south dome. There was a major upgrade in
1993....

Yup... it's been awhile. Glad to see you've had significant benefaction
since then.

Didn't Gould Optical take over an eyepiece manufacturing business a
ways back? Wonder if they could have donated some...

Richard,

Gould bought VERNONscope. More recently someone else bought Gould and they
are not interested in the VERNONscope line. I believe that Don Yeier is, or
has, bought it back.??

Most of the funding for the Kopernik expansion ($1.2 million) came from
two local foundations and companies like IBM. Unfortunately there's not much
money now. All I know is that I pay my $35 per year dues and I get to use a
$2 million observatory any time I want. If you know Binghamton then you know
it's dark here, but also rather cloudy. Check out the web site:
http://www.kopernik.org and since this is suppose to be about RC's, here
is a picture of the OGS 20-inch F/8 RC at Kopernik:
http://www.kopernik.org/images/archive/20in-1.jpg and a picture of M-43
that I took with it and an SBIG STL-1301E CCD camera a few weeks ago:
http://www.kopernik.org/images/archive/m43.htm

....and I bring my own eyepieces!

George Normandin

"John Savard" wrote

One thing did concern me about the specs..... The primary is glued into
the
tube with no possibility of adjustment and I'm not sure how you get it out
for re-coating. My experience with two RC's is that the main collimation
problem is with the primary, not the secondary. In 7 years I've never had
to
move the secondary in my OGS 10-inch RC, but the primary needs adjustment
every year or so. Although I've seen SCT's go 10 years I generally think
that their mirrors need re-coating after 6 to 7 years.

Hopefully, the primary is float-bonded to a detachable part of the
telescope, even if that is its entire rear assembly.

John,

That is exactly what I expect from the pictures and text. The mirror is
glued into the rear cell.

The intent of the construction, though, is that with nothing that moves,
there is nothing that can get out of alignment, as far as the primary is
concerned. And the secondary is supposed to be kept aligned
electronically.

Back before I bought an RC I considered building one using commercial
optics. How difficult could it be after making a few Newt's? Well I learned
a few things about the RC design from various references that partly
explains the high cost of the OGS/RCOS scopes: The two mirrors have to be
centered on each other within a few thousandths of an inch (the thickness of
a human hair). If they move (de-center), the performance goes south quickly.
Therefore an RC has to have a much stronger tube than any other type. The
normal tube sagging when moving from horizontal to vertical that would not
effect an SCT or Newt at all will badly effect an RC. Also, since the
mirrors have to be collimated within a few thousandths, and hold there, the
collimation adjustments in the mounts have to be very mechanically precise
and robust. Both OGS and RCOS have very precise push/pull micro adjustments
on the primary cell. They both offer invar cages to hold the mirror
seperation as the temp changes. OGS will make the primary cell from Al, Mg,
or Ti, as the customer wishes. One of the main problems with commercial SCTs
is that you can't collimate the primary and they move. If Meade doesn't fix
this with the new scope at least some of them will not perform as well as
they could.

I'm excited about the basic optical design of the telescope, and its
potential to inspire other optical designs. That it seems to rely a bit
too much on electronics is not something I would dispute, though. But it
does make sense to make effective use of current technology on a premium
telescope.

It will be interesting to see what Meade has and I hope that it's great. If
it performs halfway between a SCT and the current crop of RC's it will be an
big advance, particularly considering the price. It helps to remember that
the HST, which is an RC, has about a 2 wave error in its mirrors, all nearly
corrected by the lens system installed by the astronauts.

BTW, both OGS and RCOS have focal-reducer/field flattener lenses that fit up
in the baffle tube. They are based on the designs for large observatory RCs.

George Normandin

That's the way of technology and us amateurs have been and are in for the
treat of our lives.


Hi:

I'm certainly eagerly awaiting reports on the new scopes and am quite excited
about them--I'd love to get my hands on one. That said, I doubt the APO folk
have anything to worry about. Some people just like refractors, expensive
refractors, and I don't think anything Meade can do will change that. ;-)

Peace,
Rod Mollise
Author of _Choosing and Using a Schmidt Cassegrain Telescope_
Like SCTs and MCTs?
Check-out sct-user, the mailing list for CAT fanciers!
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