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Equipment Discussions >> Cats & Casses

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rmollise
Postmaster
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Reged: 07/06/07

Re: Celestron F6.3 Reducer for visual with C8? new [Re: Joe Cepleur]
      #5608067 - 01/06/13 10:56 AM

Quote:



Try it before you sell it. It's probably fair to say that using both a focal reducer and a two-inch diagonal puts each at cross purposes, but there are folks who leave focal reducers on always, and Celestron designed the scope with the focal refucer in mind. Although Meade's new LX600 breaks the trend, it was thought that SCTs natively faster than f/10 had harmfully large obstructions. I just bought a focal reducer and would like to hear what you think of yours.




The reducer/corrector in no way is at "cross purposes" with a 2-inch diagonal, and works just fine with one.

The C8 was not designed with the r/c in mind; it was designed by Jim Riffle about twenty years after the C8.

Not sure how the LX600 breaks the trend. It has a larger central obstruction, just like the LX-6 and the f/6.3 LX200s had a larger central obstruction...



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yonkrz
scholastic sledgehammer


Reged: 11/16/06

Loc: SW Minnesota
Re: Celestron F6.3 Reducer for visual with C8? new [Re: rmollise]
      #5608083 - 01/06/13 11:05 AM



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Joe Cepleur
Carpal Tunnel


Reged: 03/18/10

Loc: Dark North Woods
Re: Celestron F6.3 Reducer for visual with C8? new [Re: Joe Cepleur]
      #5608275 - 01/06/13 12:40 PM

Quote:

Fair question. The early focal reducers were 0.50, not 0.63. I'll have to research my source, but it's true. The thought upon design was that the central obstruction became too large below f/10, so for wider fields or faster exposures, the f/10 native optical tube would be modified with a focal refucer.

I'll try to find and post the source.




I have in my hands an original instruction manual for the C5 and C8. (Copies are easily downloaded.) There is no date of publication, but the cover shows a C8 with a sand cast fork, suggesting the material inside predates my particular scope. The "Recommended Reading" on Page 29 further shows my copy to have been printed no earlier than 1973. Page 22 describes an optional telecompressor that brings the optical system to f/5. The f/6.3 Field Flattener/Focal Reducer would appear to be an improvement on this earlier f/5 variant.

This does not wholly answer the question, so I'll keep looking for my source on the notion that Celestron always intended the C8 to be dual focal length with a telecompressor. If I find my source, we'll be able to ponder whether it distorts the actual history, or reveals something not widely known.


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magnus
professor emeritus


Reged: 03/17/04

Loc: Visby, Sweden
Re: Celestron F6.3 Reducer for visual with C8? new [Re: Joe Cepleur]
      #5609108 - 01/06/13 07:36 PM

With my Orange C8 Pacific -73 (deforked, on my CG-5 with vixen rail) and f/6.3 reducer I do not reach focus with my 2" WO diagonal. Instead I bought a 1.25" WO diagonal and with that I have no problems. Very happy with it! The f/6.3 is permanetly mounted on my C8. When I want high mag. I use my 2.4X Intes barlow, rather than threading the f/6.3 off. Simple and convinient at least in my opinion.
/Magnus 57N.


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ensign
scholastic sledgehammer


Reged: 12/16/08

Loc: Southwestern Ontario
Re: Celestron F6.3 Reducer for visual with C8? new [Re: magnus]
      #5609137 - 01/06/13 07:56 PM

Quote:

With my Orange C8 Pacific -73 (deforked, on my CG-5 with vixen rail) and f/6.3 reducer I do not reach focus with my 2" WO diagonal. Instead I bought a 1.25" WO diagonal and with that I have no problems. Very happy with it! The f/6.3 is permanetly mounted on my C8. When I want high mag. I use my 2.4X Intes barlow, rather than threading the f/6.3 off. Simple and convinient at least in my opinion.
/Magnus 57N.




I had the same problem. A simple, inexpensive solution is to get an SCT nosepiece for the WO diagonal (approx $40 shipped). I did this and had no problems reaching focus with any of my eyepieces.

Of late I abandoned my trusty C8 with a .63 reducer for a 9.25 Edge HD. I find the views through the Edge somewhat better.


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orion61

*****

Reged: 10/20/07

Loc: Birthplace James T Kirk
Re: Celestron F6.3 Reducer for visual with C8? new [Re: magnus]
      #5609144 - 01/06/13 07:59 PM

I use my MIJ R/C all the time, It makes a great dust seal and gets rid of quite a bit of coma!
My opinion is it is a must have for any Standard Schmidt.
I have noticed it does induce a small bit of Spherical Aberration to my C8. I did have a C8 a few years ago that had a bit of SA and it cancelled most if it out!
I'd like to see someone build a corrector into a 2" Diagonal barrel, Inserted inside not screwed on sticking out.
That could eliminate 2 problems!!


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Joe Cepleur
Carpal Tunnel


Reged: 03/18/10

Loc: Dark North Woods
Re: Celestron F6.3 Reducer for visual with C8? new [Re: orion61]
      #5609161 - 01/06/13 08:12 PM

Quote:

I'd like to see someone build a corrector into a 2" Diagonal barrel, Inserted inside not screwed on sticking out.




That strikes me as a truly great idea. Would the right design allow a standard SCT with an inexpensive accessory to pretty well mimic the performance of the fancy new EdgeHDs and LXs? Optically, anyway. I know there is a lot about their focusers and mounts contributing to their overall performance.


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orion61

*****

Reged: 10/20/07

Loc: Birthplace James T Kirk
Re: Celestron F6.3 Reducer for visual with C8? new [Re: Joe Cepleur]
      #5609179 - 01/06/13 08:26 PM

Quote:

Quote:

I'd like to see someone build a corrector into a 2" Diagonal barrel, Inserted inside not screwed on sticking out.




That strikes me as a truly great idea. Would the right design allow a standard SCT with an inexpensive accessory to pretty well mimic the performance of the fancy new EdgeHDs and LXs? Optically, anyway. I know there is a lot about their focusers and mounts contributing to their overall performance.



Thats what gave me the idea, the corrector lens in the focuser baffle,
But then they couldnt sell those 2K tubes SHHH...LOL


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mclewis1
Thread Killer
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Reged: 02/25/06

Loc: New Brunswick, Canada
Re: Celestron F6.3 Reducer for visual with C8? new [Re: orion61]
      #5609751 - 01/07/13 08:34 AM

Moonlite sells an external focuser that has the option of placing a modified SCT focal reducer into the barrel. There are also other sources on the web of repackaged focal reducers and kits that fit inside many 2" barrels.

http://www.optecinc.com/astronomy/catalog/17408.htm

http://www.observatory.org/vpacs.htm (low profile adapters ... no focal reducers)


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Joe Cepleur
Carpal Tunnel


Reged: 03/18/10

Loc: Dark North Woods
Re: Celestron F6.3 Reducer for visual with C8? new [Re: mclewis1]
      #5613493 - 01/09/13 10:55 AM

In the last sentence of the Overview, B&H continues the notion that Celestron sells an f/6.3 focal reducer because, "a f/6.3 Schmidt-Cassegrain telescope... is impractical with a large central obstruction and a resulting loss in contrast." That is not the source I intended to quote, so I'll keep looking for a better source, yet it is interesting to see this notion out there, especially in light of Meade's new LX600. Maybe fast focus Schmidt-Cassegrains require fancy, modern optics, or is this entire notion really just a myth?

I'll continue searching for a primary source stating that Celestron originally intended its f/10 SCT as the fastest natively practical, with a reducer intended to reach faster speeds with a reasonable obstruction.


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Joe Cepleur
Carpal Tunnel


Reged: 03/18/10

Loc: Dark North Woods
Re: Celestron F6.3 Reducer for visual with C8? new [Re: Joe Cepleur]
      #5613512 - 01/09/13 11:11 AM

Is this notion beginning to sound familiar? Same exact wording! This still does not prove or disprove that the focal reducer was intended to be part of the C8 kit from the beginning, but it suggests that recycled advertising copy could distort the actual history. This site is British, so the notion is spreading world-wide:

"Celestron doesn’t offer a f/6.3 Schmidt-Cassegrain telescope, because the design is impractical, with a large central obstruction, and resulting loss in contrast. This, added to the inability to utilize longer focal ratios for certain objects, led Celestron to design the four-element, fully multicoated f/6.3 Reducer/Corrector."


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rmollise
Postmaster
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Reged: 07/06/07

Re: Celestron F6.3 Reducer for visual with C8? new [Re: Joe Cepleur]
      #5613534 - 01/09/13 11:31 AM

Quote:

This still does not prove or disprove that the focal reducer was intended to be part of the C8 kit from the beginning




Well, what disproves that is that the reducer/corrector did not appear till nearly 20 years after the C8 was first introduced...

There had been reducers (not reducer/correctors) available before then, most of them at f/5, from Celestron and other sources.

Once again, the impetus for the r/c was Meade's release of the LX-6 in the late 80s.



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Joe Cepleur
Carpal Tunnel


Reged: 03/18/10

Loc: Dark North Woods
Re: Celestron F6.3 Reducer for visual with C8? new [Re: rmollise]
      #5613573 - 01/09/13 11:49 AM

Okay, thanks, Uncle Rod; time for me to quit hunting for history I can not find because it does not exist, except maybe in some convincing sounding error I read someplace.

After reading an earlier post about the Meade LX-6, I get it... maybe. Meade introduced a natively f/6.3 SCT, with all the attendant advantages of faster exposures for photographers, but with iffy optics, at least in the early models. To compete with the faster exposures while beating the coma-shaped stars at the edge of the Meade's field of view, Celestron introduced the f/6.3 focal reducer for its f/10 scopes. Along with offering better contrast than the competing Meade, due to the smaller central obstruction, this would have made an arguably better f/6.3 system, at least one well tuned to Celestron's advertising copy.

What's the deal with Celestron's eariler f/5 reducer? Presumably it was great for reducing exposure times, but wreaked havoc on the sharpness of stars toward the edge of the wider field of view? That would explain why Celestron needed to introduce a reducer/CORRECTOR.


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rmollise
Postmaster
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Reged: 07/06/07

Re: Celestron F6.3 Reducer for visual with C8? new [Re: Joe Cepleur]
      #5613797 - 01/09/13 02:14 PM

It was like any other reducer then or now. Yeah, shorter exposure times, but edge of field performance no bettter than--and usually worse than at f/10.

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JamesL
member


Reged: 10/19/12

Loc: Pacific,MO
Re: Celestron F6.3 Reducer for visual with C8? new [Re: rmollise]
      #5614125 - 01/09/13 05:24 PM

My focal reducer came today. I would like to try it out but clouds and rain will prevent me for the next several days.
In the mean time I,ll install this sliding counter weight system and just admire my cat untill the weather clears!


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Eddgie
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Reged: 02/01/06

Re: Celestron F6.3 Reducer for visual with C8? new [Re: Joe Cepleur]
      #5614153 - 01/09/13 05:45 PM

Hello Joe,

There may be some confusion and some of it may be mine.

At one point, you could buy a "Rich Field Adapter" for SCTs and this was indeed f/5.

It was in essence a special 1.25" diagonal with a reducer built right in.

Horrible to use in my opinion. I used to own one maybe 25 years ago. And that would in iteself explain why it is no longer sold. Really terrible. Loaded with astigmatism as I recall, though to be fair, it could have been the eyepeices made at the time were just not working well with the f/5 light cone.

But the coma from the scope and the astigmatism where so severe that I used it once and threw it in my junk drawer.

So, maybe this is what the f/5 was in reference to...


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Eddgie
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Reged: 02/01/06

Re: Celestron F6.3 Reducer for visual with C8? new [Re: Eddgie]
      #5614156 - 01/09/13 05:46 PM

Speak of the devil... Regarding my previous post, here is an example:

Celestron f/5 Rich Field Adapter

And by the way... The focal reducer does not make the obstruction any larger unless it is used in a configuration with a lot of back focus so that the scope is loosing aperture.

The Celestron marketing positioned the Celestron focal reducer as a better alternative to an Native f/6.3 SCT, which was made by Meade for a while. The Meade f/6.3 SCT had a 40% obstruction, and Celetron's position was that it was better to use the reducer and keep the smaller CO than go to the Meade f/6.3 with the bigger obstruction.

So, it was a marketing thing.

And it must have worked. The Meade f/6.3 SCT bombed in the marketplace. But this was well before digital imageing came into the picture. Hypered film was the leading edge technology, and because of the expense (processing the film was the big cost) the hobby was not as popular as today, and I doubt that they sold enough scopes to make it worth the production time.

But if you can do it wite a telecompressor, then why bother with a native f/6.3 SCT which had wicked field curvature.

Edited by Eddgie (01/09/13 05:56 PM)


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rmollise
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Reged: 07/06/07

Re: Celestron F6.3 Reducer for visual with C8? new [Re: Eddgie]
      #5614195 - 01/09/13 06:13 PM

Quote:

Hello Joe,

There may be some confusion and some of it may be mine.

At one point, you could buy a "Rich Field Adapter" for SCTs and this was indeed f/5.

It was in essence a special 1.25" diagonal with a reducer built right in.

Horrible to use in my opinion. I used to own one maybe 25 years ago. And that would in iteself explain why it is no longer sold. Really terrible. Loaded with astigmatism as I recall, though to be fair, it could have been the eyepeices made at the time were just not working well with the f/5 light cone.

But the coma from the scope and the astigmatism where so severe that I used it once and threw it in my junk drawer.

So, maybe this is what the f/5 was in reference to...




There were numerous reducers at f/5 available, including from Lumicon, Orion, etc., etc. The non-correcting reducer was around since the beginning and even Celestron produced a couple of different iterations.

Many were quite useable for imaging, and that was all we had unless you wanted to shoot the deep sky at f/10.

Edited by rmollise (01/09/13 06:14 PM)


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Joe Cepleur
Carpal Tunnel


Reged: 03/18/10

Loc: Dark North Woods
Re: Celestron F6.3 Reducer for visual with C8? new [Re: Eddgie]
      #5614253 - 01/09/13 06:38 PM

Quote:

Celestron marketing positioned the Celestron focal reducer as a better alternative to an Native f/6.3 SCT, which was made by Meade for a while. The Meade f/6.3 SCT had a 40% obstruction, and Celetron's position was that it was better to use the reducer and keep the smaller CO than go to the Meade f/6.3 with the bigger obstruction.




Thanks, all -- Now the story makes perfect sense. Kinda like the game of "telephone." By the time it got to me thirty years later, either it had morphed or I had morphed it. While a C8 with a focal reducer is not the ultimate rich-field scope, being able to swap between f/10 and f/6.3 is an excellent perk in a flexible system, whatever its origins. Carrying a reducer/corrector beats carrying and setting up a second optical tube!

Celestron's marketing must have been effective. I'm sure I would have bought the pitch. Sounds as though it was true, anyway.

Thanks for the tip on the old f/5 diagonals. I'm a trinkets guy, and love collecting old accessories. I like the feeling of tangible history. I'm happy with my recently purchased, Japanese-made Meade f/6.3 refucer/corrector, happier than with a new Synta! I was the only bidder on eBay, and almost felt sorry for the seller, but fair was fair, he did okay. But -- I've seen these curious f/5 diagonals for sale, and have erased them from my wish list!


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Joe Cepleur
Carpal Tunnel


Reged: 03/18/10

Loc: Dark North Woods
Re: Celestron F6.3 Reducer for visual with C8? new [Re: rmollise]
      #5614280 - 01/09/13 06:53 PM

Quote:

There were numerous reducers at f/5 available, including from Lumicon, Orion, etc., etc. The non-correcting reducer was around since the beginning and even Celestron produced a couple of different iterations.




From a marketing point of view, it would be advantageous for Celestron to let people believe that the better solution to Meade's native f/6.3 had been available from the beginning. It sounds as though the truth was that it became truly viable only with the introduction of Celestron's f/6.3 reducer/corrector, but what a great marketing blitz it must have been! Smothered Meade's native f/6.3 in its infancy, with a seemingly objective argument about the size of the central obstruction. The competition between these companies must have been savage.


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