Celestron Coma corrector (Important Update!)
Lawrence Sayre
I came across a Marcus Ludes post from ~1998 stating that these were
still being made in Germany, and were still available as of that time.
Therefore, I E-Mailed Marcus, and he responded that the Baader 2" Coma
Corrector (same unit as sold here by Celestron until discontinued) is
still available, and a new one complete with the adapters necessary for
visual use with 1.25" and 2" eyepieces (I'm not exactly sure what he was
referring to here) would go for $200, which includes dilevery to the
USA. Marcus said it is known as the 'MPCC Newtonian Coma Corrector'.
Without the visual use adapters (and possibly without the shipping
charges as well?) the 2" unit costs only $120. I assume that in this
lower priced configuration it would be for photography only.
PS: I forgot to ask Marcus if they still made the 1.25" only size, but
this could be a boon to those looking for coma correction in a 1.25"
only focuser as well.
---------------------------------------------
"Man's mind is his basic tool of survival!"
(a quote from the famous 'John Galt' speech
in the equally famous book "Atlas Shrugged")
Lawrence Sayre <lsa...@stratos.net>
---------------------------------------------
bratis...@my-deja.com
Lawrence Sayre <lsa...@stratos.net> wrote:
> Without the visual use adapters (and possibly without the shipping
> charges as well?) the 2" unit costs only $120. I assume that in this
> lower priced configuration it would be for photography only.
MPCC _is_ for photography only. Being a classic Ross type corrector it
affects the spherical correction quite a lot. Unless you make your
primary deliberately as a hyperboloid (quite possible, but then you
won't be able to use it _without_ MPCC), it cannot be even used in
a low power eyepieces. I can see degradation even with my 32mm 2"
Konig, which is otherwise very sharp in center at ~f/6. Not much,
but once you see it ... And at high magnifications it is painfuly
obvious.
For photography it is even better than Paracorr (as it FULLY corrects
coma), but for visual forget it.
Bratislav
Sent via Deja.com http://www.deja.com/
Before you buy.
Del Johnson
accomodate an off-axis guider. The Lumicon corrector, though not as
good for visual use, works very nicely with their Easy Guider. The
TeleVue Paracorr does not offer this capability, unfortunately.
Del Johnson
In article <390753A7...@stratos.net>,
Lawrence Sayre <lsa...@stratos.net> wrote:
> While doing a 'Deja News' search for the old 'Celestron Coma
Corrector'
> I came across a Marcus Ludes post from ~1998 stating that these were
> still being made in Germany, and were still available as of that time.
>
> Therefore, I E-Mailed Marcus, and he responded that the Baader 2" Coma
> Corrector (same unit as sold here by Celestron until discontinued) is
> still available, and a new one complete with the adapters necessary
for
> visual use with 1.25" and 2" eyepieces (I'm not exactly sure what he
was
> referring to here) would go for $200, which includes dilevery to the
> USA. Marcus said it is known as the 'MPCC Newtonian Coma
Corrector'.
>
> Without the visual use adapters (and possibly without the shipping
> charges as well?) the 2" unit costs only $120. I assume that in this
> lower priced configuration it would be for photography only.
>
> PS: I forgot to ask Marcus if they still made the 1.25" only size, but
> this could be a boon to those looking for coma correction in a 1.25"
> only focuser as well.
>
> ---------------------------------------------
> "Man's mind is his basic tool of survival!"
> (a quote from the famous 'John Galt' speech
> in the equally famous book "Atlas Shrugged")
>
> Lawrence Sayre <lsa...@stratos.net>
> ---------------------------------------------
>
Lawrence Sayre
>
> In article <390753A7...@stratos.net>,
> Lawrence Sayre <lsa...@stratos.net> wrote:
>
> > Without the visual use adapters (and possibly without the shipping
> > charges as well?) the 2" unit costs only $120. I assume that in this
> > lower priced configuration it would be for photography only.
>
> affects the spherical correction quite a lot. Unless you make your
> primary deliberately as a hyperboloid (quite possible, but then you
> won't be able to use it _without_ MPCC), it cannot be even used in
> a low power eyepieces. I can see degradation even with my 32mm 2"
> Konig, which is otherwise very sharp in center at ~f/6. Not much,
> but once you see it ... And at high magnifications it is painfuly
> obvious.
>
> For photography it is even better than Paracorr (as it FULLY corrects
> coma), but for visual forget it.
>
> Bratislav
>
I'm getting advice that this is far better than the Paracorr, and also
advice that it is far worse. Now I'm really confused. My interest is
in visual use only.
Herm
distorted stars at the edge of the FOV, is this coma or astigmatism?..what about
field curvature?
BTW, when you use your MPCC with that 32mm Konig, how far away from CC lens is
the focal plane?, it sounds like you don't have the right distance (too far
out).
Herm
On Wed, 26 Apr 2000 23:12:23 GMT, bratis...@my-deja.com wrote:
>In article <390753A7...@stratos.net>,
> Lawrence Sayre <lsa...@stratos.net> wrote:
>
>> Without the visual use adapters (and possibly without the shipping
>> charges as well?) the 2" unit costs only $120. I assume that in this
>> lower priced configuration it would be for photography only.
>
>MPCC _is_ for photography only. Being a classic Ross type corrector it
>affects the spherical correction quite a lot. Unless you make your
>primary deliberately as a hyperboloid (quite possible, but then you
>won't be able to use it _without_ MPCC), it cannot be even used in
>a low power eyepieces. I can see degradation even with my 32mm 2"
>Konig, which is otherwise very sharp in center at ~f/6. Not much,
>but once you see it ... And at high magnifications it is painfuly
>obvious.
>
>For photography it is even better than Paracorr (as it FULLY corrects
>coma), but for visual forget it.
>
>Bratislav
>
>
Herm
nasty f4 newt with a 30mm ultima...I'm sure it introduces spherical error but
its just not visible at that magnigfication..for high power use I simply remove
it, same as a Paracorr.
What you describe is true for the Vixen R200SS coma corrector, I cant stand to
use this corrector even with a low power eyepiece, but its very good for
photography.
Stargate96
>affects the spherical correction quite a lot. Unless you make your
>primary deliberately as a hyperboloid (quite possible, but then you
>won't be able to use it _without_ MPCC), it cannot be even used in
>a low power eyepieces. I can see degradation even with my 32mm 2"
>Konig, which is otherwise very sharp in center at ~f/6. Not much,
>but once you see it ... And at high magnifications it is painfuly
>obvious.
Well Bratislav, I'm afraid I have to disagree with you on this. I have used
the Celestron MPCC on my 24" F/4 (Pegasus Optics) for five years now. When
used with a 27mm Panoptic it provides very pinpoint stars across about 95% of
the field. The same goes when using Naglers, all the way up to the 4.8mm. I
have hauled this scope all over the southern US so there are a few hundred
people who can vouch for this.
Pat Rochford
Stargate Observatory
Fairhope, Alabama
lude...@my-deja.com
Hi Bratislav,
I never used such an MPCC, but here an short brief describtion of the
original Baader Broshure:
2" MPCC Newtonian Comacorrector
matched for the T2 System
delivers a complete comafree field of view, without focallenght
increase, for 1.25" and 2" eyepieces, as well as for photographic use
with 35 mm cameras. Usefull on all Newtonians with f-ratio from f/4 to
f/6. This item we deliver also to Celestron/USA. Please order by
interested our 6 page english informationbroshure.
The lenssystem is installed in a 2"/T2 body, which means it is usefull
in all 2" focusers. On side of cameruse it have an T2 ( M42x0.75")
thread, on which all T2 rings or other T2 adapters can be attached.
I talked now with an friend who used this MPCC visualy and he confirmed
it works very well.
best wishes
Markus
>
> MPCC _is_ for photography only. Being a classic Ross type corrector it
> affects the spherical correction quite a lot. Unless you make your
> primary deliberately as a hyperboloid (quite possible, but then you
> won't be able to use it _without_ MPCC), it cannot be even used in
> a low power eyepieces. I can see degradation even with my 32mm 2"
> Konig, which is otherwise very sharp in center at ~f/6. Not much,
> but once you see it ... And at high magnifications it is painfuly
> obvious.
>
bratis...@my-deja.com
lude...@my-deja.com wrote:
> In article <8e7t4i$64n$1...@nnrp1.deja.com>,
>
> Hi Bratislav,
>
> I never used such an MPCC, but here an short brief describtion of the
> original Baader Broshure:
Hi Markus,
I have the MPCC and I also have a complete optical design (reverse
engineered by measuring the elements with a spherometer). I can't
publish it of course, but it is a typical Ross corrector, having
a negative meniscus followed by biconvex lens. I ray traced it with
many paraboloids from f/3 to f/8 and it does what is supposed to -
eliminates coma and flattens the field. It ALSO introduces spherical
aberration which can be dealt with by overcorrecting the primary.
Look in Rutten & van Venrooij book and see the analysis there (they
used f/6 as an example), that design is similar to Baader's. At faster
f-ratios residual spherical gets even worse.
It is an excellent photographic gadget, but for visual Paracorr is
simply better as it much less affects on-axis performance.
bratis...@my-deja.com
starg...@aol.com (Stargate96) wrote:
> Well Bratislav, I'm afraid I have to disagree with you on this. I
have used
> the Celestron MPCC on my 24" F/4 (Pegasus Optics) for five years now.
When
> used with a 27mm Panoptic it provides very pinpoint stars across about
95% of
> the field. The same goes when using Naglers, all the way up to the
4.8mm.
Maybe we have different MPCCs (which I doubt), or have different
sensitivity to spherical aberration. Apart from using it in a scope, I
also have a complete optical design of MPCC, reverse engineered by
measuring the elements; ray trace show just the same - a moderate
to severe spherical aberration on axis (depending on f/ratio).
This is nothing new - Ross corrector has been discussed for decades,
and it is well known that it cannot simultaneously correct coma and
be completely free from spherical aberration. You need more elements
for that, and that is precisely what Al has done with Paracorr.
bratis...@my-deja.com
herm...@worldnet.att.net (Herm) wrote:
> Bratislav, please clear this up for me..when we use a fast newt and
see
> distorted stars at the edge of the FOV, is this coma or
astigmatism?..what about
> field curvature?
It depends on an eyepiece. Some modern wide field designs have sorted
out their own astigmatism so well that you CAN see paraboloid's coma.
Naglers are one example. In a Konig blobs are DEFINITELY eyepiece's
astigmatism. Ditto even for typical narrow angle eyepieces like
Plossls, Orthos and like.
> BTW, when you use your MPCC with that 32mm Konig, how far away from CC
lens is
> the focal plane?, it sounds like you don't have the right distance
(too far
> out).
MPCC is designed to have BFL of about 63mm from the last surface (or so
if memory serves). I have the exact number somewhere, to within 0.01mm
if you want. It is also specified for T mount, that is the distance from
the back flange to focal plane should be 55mm.
BTW, it is difficult to have 32mm Konig 'too far out' as its field
stop is half way down the chrome barrel. Too much in fact.