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Is this Celestron C90 "Classic" or "Used?"

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#1 Joe Cepleur

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Posted 25 November 2012 - 06:13 PM

I have an opportunity to buy an older C90 from a member of my club. I'm interested if the price is right, but have no idea how much to offer. It strikes me as an excellent birding scope and a better-than-expected, grab-and-go, ultralight astronomy scope. I was impressed upon first reading Uncle Rod's assessment last year, yet had never seen one in person until now. An apparently classic article in "Better View Desired" praises this scope highly, suggesting its a real sleeper. Views are about as good as a Questar's at a fraction of the price, which is actually not surprising.

What's the drill with this scope? If a 4" refractor is suitable for various authors to use in publishing books about the Messier objects, how much different could at 3.5" be? According to the article in "Better View Desired," the C90 offers basically perfect color correction, 3.5" of resolution, 3.25" of brightness, and the contrast of a 60mm. That last may not be much to brag about, but for a lightweight rig used more for practicing finding Messier objects than studying them in detail, may not be so bad. Portability is key here. A C90 would not replace my C8, nor would it need to.

So, here's the first picture. This C90 is a black tube with helical focuser and a 0.965" visual back (if it's called that when it is integral to the scope). One respected opinion is that it was made by Vixen in Japan; can anyone attest to that? The undersized tripod is what I had on hand, but the case would be sold with the scope. No eyepieces or diagonal are included, so I used a set from my Jason 313. It will not focus with the extra back focus created when using a 0.965'-to-1.25" adapter before a 1.25" diagonal, so I'd need to buy a good hybrid diagonal. I suspect the optics are excellent, but can not confirm so by star test with the junky high-powered eyepieces currently at my disposal. I must say, the detail seen a mile and further away in daylight was astonishing!

Before I questioned whether he might like to sell it to me, the seller commented that the focuser was so tight that it was impossible to focus without knocking the scope off its target. I'd think that's a matter of cleaning away old grease and relubing with Mobil 1 Synthetic Grease (any other recommendations?). He also said that he paid little for it, because it "had problems," but I suspect he and the former owner were simply baffled by the need to use a diagonal. It will not focus when viewed straight through. The seller bought his dream Questar Birder, and so has no further use for the C90.

I have found no indication of where the scope was made. Torrance would be cool, Japan perfectly acceptable, but maybe not China in this vintage. What do I have here, a "Classic," or a "used telescope," and how much is it worth?

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#2 Joe Cepleur

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Posted 25 November 2012 - 06:14 PM

The "Special Coating" sticker exactly matches those on older C8s made in Torrance, which does not necessarily mean it was made there.

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#3 CHASLX200

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Posted 25 November 2012 - 06:15 PM

Looks like a much later version compared to when they fisrt came out.

Chas

#4 Joe Cepleur

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Posted 25 November 2012 - 06:23 PM

The 8x20 finder is a bit of a joke, but it works. Might want to replace it with a 6x30. It focuses easily, but has a narrow field of view, and it is impossible not to bonk one's head somewhere on the scope when attempting to use the finder. I have not decided whether that's a hazard of the overall small size, or a result of bad design. This finder was from the spotting scope package. The astronomical package had a 6x30; was it discontinued by the time this scope was made? Anyway, the rest of what you see is all metal. Was it cast from the same molds as the Orange Tubes?

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#5 Joe Cepleur

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Posted 25 November 2012 - 06:25 PM

Looks like a much later version compared to when they fisrt came out.

Chas


Yes, thanks; note that all of the writing and the orange stripe are on a sticker! No early Celestron would have that!!

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#6 Joe Cepleur

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Posted 25 November 2012 - 06:27 PM

Serial Number 887061. Note also that this is the f/11 version, not the later f/5.6 sold for photography with supposedly inferior optics.

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#7 Joe Cepleur

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Posted 25 November 2012 - 06:29 PM

Here's a shot for all you Forensic Lenscapologists, which also shows the interior of the case and the business card of the vendor who sold it to my seller.

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#8 Joe Cepleur

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Posted 25 November 2012 - 06:30 PM

Forensic Lenscapology being a popular sport, here is the other side.

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#9 Joe Cepleur

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Posted 25 November 2012 - 06:32 PM

Nice case, cut to fit a camera.

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#10 actionhac

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Posted 25 November 2012 - 06:37 PM

It looks very similar Joe.
I paid $100 for mine not long ago and I really like using it. Except I don't like the helical focuser for astronomy, anything else it's fine especially nature. The focusing is very fast, too fast for astronomy but it is just my opinion.
Its a excellent value at what seems to be a regular average price, approximately $100 for the spotter.
I bought a Meade adapter #07036FL that screws on to the port and then you can use your C8 visual back and accessories.

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#11 Joe Cepleur

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Posted 25 November 2012 - 06:40 PM

The outside of the case. The 32mm Plossl is not included in the sale, but is there to show comparative size.

So, a black C90 with a helical focuser and 0.965" back:

*** "Classic" or "Used?"

*** Torrance, Vixen Japan, or China?

*** What might it be worth?

*** Lucky find, or best to pass?

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#12 Joe Cepleur

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Posted 25 November 2012 - 06:47 PM

I don't like the helical focuser for astronomy... The focusing is very fast, too fast for astronomy...

I bought a Meade adapter #07036FL that screws on to the port and then you can use your C8 visual back and accessories.


I'd imagine the helical focuser could be difficult for astronomy. Still, Uncle Rod's article notes that there is no mirror flop possible with helical focusers, so that this model of C90 can be used as a guide scope!

The adapter sounds interesting. I wonder whether the optics differ between your Orange Tube and this scope. Just extending the back focus with a 0.965"-to-1.25" adapter made it impossible to focus.

#13 actionhac

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Posted 25 November 2012 - 06:47 PM

Mine doesn't have special coatings which is very desirable and may make a C90 worth considerably more.
The tube and focuser grip are cast as one and made out of Bakelite on the orange version.

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#14 Joe Cepleur

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Posted 25 November 2012 - 06:50 PM

Actionhac, you paid $100 for a clearly classic Orange Tube. Is a later black tube of lesser value, even if the optics proved to be comparable?

#15 Joe Cepleur

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Posted 25 November 2012 - 07:04 PM

Mine doesn't have special coatings which is very desirable and may make a C90 worth considerably more.


Yes; important point. I've read that in the articles linked in the first post above. I'd love to see the two scopes side-by-side. The difference is said to be appreciable, maybe not so much because it's eye-popping, but because it squeaks the best possible image out of a small aperture scope. An 8" without Special Coatings may be said to work like a 6-inch, but there's less headroom with a C90. Still...

The tube and focuser grip are cast as one and made out of Bakelite on the orange version.


An Orange Tube will always be cooler! Great collector's piece, and I'm sure the images are great.

#16 actionhac

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Posted 25 November 2012 - 07:11 PM

I wouldn't think the black tube would be worth less given

equal optics. The C90 seems to be more a working telescope

as opposed to being a collector. And really the newer the
better is the general rule :gotpopcorn: when it comes to

CAT's and this may apply to MAK's as well.

The Meade #07036LF adapter is a ETX 90 accessory, I'm not sure if its still available. Basically it is the same as the original LAR adapter for the C90. Here it is:

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#17 H.S.

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Posted 25 November 2012 - 11:39 PM

I think mine is a 1976 model. Hybrid diagonal with a 32mm UO Konig. I don't know what the coatings are.
Harry

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#18 Ducky62

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Posted 26 November 2012 - 12:10 AM

I've got a black one in the tacklebox case. I bought it on astromart for $120 shipped back when I really needed the finder and a "better" .965 diagonal, Barlow and some EPs for another 'scope.It isn't terrible but I don't like the helical focuser. I'll probably keep it until I find a deal on a nice Orange Astro model. I have a Chinese-sourced Vixen-branded 90mm Mak with a flip mirror which blows it away optically and is my primary grab-n-go telescope.Both were 1/20th the cost of a used Questar but I do love 90mm Maks so one of those is on my bucket list too.

I think my point is I wouldn't give more than about $50-60 for an untested black C-90 with no mount or accessories.
If it performs well and the case is nice the C-90 might be worth a C-note, but no more. JMHO.

(I'd add at least $25 for a LAR but the 'scope in question doesn't have one.)

#19 actionhac

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Posted 26 November 2012 - 12:24 AM

Now here's a good idea:
http://www.cloudynig...5475652/Main...

Robert

#20 Joe Cepleur

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Posted 26 November 2012 - 12:28 AM

I have a Chinese-sourced Vixen-branded 90mm Mak with a flip mirror which blows it away optically and is my primary grab-n-go telescope.


I've seen that scope advertised. Neat scope. The 110mm version has had mixed reviews. It may be that if people expect more than so small a scope can deliver, they are disappointed; but, it they appreciate its limits, it becomes a favorite grab-and-go. They are inexpensive even with a Porta II Mini mount. Good deal!

I think my point is I wouldn't give more than about $50-60 for an untested black C-90 with no mount or accessories.


Good to hear that a comfortable price would also be fair.

(I'd add at least $25 for a LAR but the 'scope in question doesn't have one.)


What's a "LAR?"

I just took the scope out with the 21mm Kelner (53x) and the tabletop photo tripod, and succeeded only in proving what we already know, that the mount is half the telescope. Somehow, I managed to find Jupiter. Moons were fairly sharp, and I could see faint cloud bands. Focusing proved difficult, and after I did manage a decent focus, it was too easy to knock it out again!

By whatever miracle, I then found the Orion nebula hand-held, by scanning the skies. Impressive nebulosity, but it was not possible to simultaneously hand-hold and focus sharply.

A better mount and tripod would ease the situation.

#21 Joe Cepleur

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Posted 26 November 2012 - 07:54 AM

Now here's a good idea:
http://www.cloudynig...5475652/Main...

Robert


Yes, Actionhac; thanks, that's slick! Funny to see that adapter used successfully, since I could not get the scope to focus with even the added back focus of a 0.965"-to-1.25" adapter. I'll have to try again. Alternatively, since the scope needs a new hybrid diagonal anyway, does anyone make one with a built-in, helical fine focuser?


DREAMING OF ASTRONOMY -- LEARNING IN MY SLEEP

I dreamed last night about the images of Jupiter and the Orion Nebula seen through the scope. They answered the question about the relationship between resolution, brightness, and contrast.

Other than the trouble getting the scope to focus, images seemed sharp and detailed. That is "resolution."

The Moon was bright, so conditions were not ideal. Still, the sky and my targets were brighter through the scope than with the naked eye, a function of "brightness."

Trouble was, stars did not pop against the background, the cloud bands of Jupiter were barely discernible, and the nebulosity surrounding the Orion Nebula, while impressive for so small a scope, did not extend further into the sky. These were problems of "contrast." The image was however bright, but the difference between the brightest and darkest parts of the image was insufficient to make observed objects pop. Still, the view was pretty good for a scope that weighs almost nothing, and is small enough to carry anywhere! Presumably, this is the quality that would be most improved by trading the little Mak for a refractor or off-axis reflector. The contrast would be more suitably appropriate to the other qualities of the view. It was likely good luck for my understanding that I tested this on a moonlit night, when this issue would be at its worst. The views would be much better, and the importance of contrast less obvious, in dark skies.

In sunlight, it's a different story altogether. I'm still impressed with the detail seen on objects between half a mile and a mile-and-a-half away. I can see why birders love this scope without reservation.

#22 actionhac

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Posted 26 November 2012 - 10:59 AM

I like that idea too. It does solve the problem of the camera lens style focusing which is the only thing I don't like about the C90 for astro work. Now for action like animals, sports etc. the camera type helical is great because of its speed and you can hold the C90 like you would a SLR camera.
I guess I need to go to a hardware store and look at the plumbing section.

The contrast problem is probably the secondary obstruction. with any CAt or Mak I feel like I forgot to take my sunglasses off.
I have done side-by-side tests with my C8 and Optical Craftsmen 8" Newtonian and the difference is very obvious, especially the Orion Nebula.
But this is one of the sacrifices we make to have such a compact instrument. Sometimes I'm willing to give up some precious contrast. When I want to observe seated the C8 is great. Just imagine taking a 60X1000 refractor to a baseball game.

Robert

#23 Ducky62

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Posted 26 November 2012 - 10:59 AM

Large Accessory Ring. It is the Celestron part that allows the use of 1.25" accessories. I don't know if the Meade one fits later C-90s.

#24 Joe Cepleur

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Posted 26 November 2012 - 11:59 AM

If the C90's mathematics say it should have the contrast of an unobstructed 60mm, why are the dimmer images of Jupiter's cloud bands through my Jason 313 so much more vivid and beautiful? So much for theory. It's as though the view through the C90 was washed out and overexposed. Still, at the right price, it's a tempting keeper for birding, or for astronomy from the trunk of the car. It's just so perfectly portable.

#25 Geo.

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Posted 26 November 2012 - 02:33 PM

Large Accessory Ring. It is the Celestron part that allows the use of 1.25" accessories. I don't know if the Meade one fits later C-90s.


Fits some, tight on others. I've found the helical focuser's action is much better on the later C90's. The early black tubes in f/11 and f/5.6 were for use as camera lenses and were not coated. The OT C90s had a coated menicus. Probably why this post OT period specimen is denoted as special coatings, meaning it was intended as a scope not a lens.






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