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Would you buy a old C8??

Started by Guest_**DONOTDELETE**_* , Nov 07 2003 05:00 PM
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21 replies to this topic

#1 Guest_**DONOTDELETE**_*

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Posted 07 November 2003 - 05:00 PM

Just need an advise.. :confused:
Would you buy a C8 ( 20 year old, the orange one )in good condition. Pls consider that I want use it for webcam imaging (70%) and to look at globular/open clusters + nebulae who seems to me not very detailled in my 80mm
refractor.
The price requested is 250 USD ( OTA ) with glass solar filter and finder.

SeB

Visit my website : http://users.skynet.be/astroseb

#2 matt

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Posted 08 November 2003 - 02:36 AM

Seb, If you don't buy it I WILL! :cool:
Pending inspection.
SOME of the older C8s can be very good optically. Plus as the tube is closed the mirror is usually clean and does not require re-coating.

True story:
My father owns a '79 C8. We let it (5 years ago) to a local octical store / telescope reseller for recollimation and whatever checkup a 20 year old scope needed. First the guy realized he did not have much to do. Then we toyed with him about the idea about upgrading to a C11 or maybe the 12" Meade. The optician told us he did not wnt us to sell the scope, and that he'd rather miss the sale of a C11 than see us sell that C8. :foreheadslap:

#3 Stelios

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Posted 08 November 2003 - 03:08 AM

I sold my 20 yo C8 to a friend for $425 -- the price was so low because he IS a friend and I was upgrading anyway.

Much depends on the telescope itself. Recently there was a review (in a comparison with a 4" APO) of a C-8 that NOBODY would want. But if you can find a telescope such as mine was (Built 1982 with a working drive. Tripod and wedge. Trunk case for OTA. Excellent optics -- to judge them allow 2 hours for cooldown and DO check the collimation on the scope) you should JUMP at it. The only negative part of that generation of C-8's was the aluminum tripod that has almost no stability (but because of its light weight, it's trivial to carry the entire set up scope from house to garden -- under 35 lbs all-inclusive).

#4 Guest_**DONOTDELETE**_*

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Posted 08 November 2003 - 04:19 AM

Thanks guys, I'm going to mount it on my GP equatorial mount with my Vixen ED 80 mm, I got a good tripod so I don't worry about that.
I heard that Celestron and Meade SCT have bad reputation mainly because people who uese it don't collimate their scopes very often.

#5 Guest_**DONOTDELETE**_*

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Posted 09 November 2003 - 09:40 AM

Seb,
Id ask the owner if it at least has starbrite coatings on the corrector if it has them its a deal if not it will reflect a lot of unnecessary light back before it reaches your eyepiece. I personally wouldnt a C8 that didnt come with anti-reflective coatings on the corrector as there are plenty of used ones that are coated already out there already and with having a large central secondary hanging there already you need every bit of help already. My .02 being a used C8 owner & yes mine has Starbrite coatings. I admit finding one for that price range probably isnt going to happen with the coatings and for solar its a steal, but deep fuzzys will loose some contrast if its uncoated on the corrector. Depends on what your going to use it for mostly I suppose. Dave

#6 Guest_**DONOTDELETE**_*

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Posted 11 November 2003 - 04:13 PM

Well, I'm not sure that a 20 year old C8 has starbrite coatings, I think that this kind of coatings release came after this C8?
I bought this C8 and I'm going to install it on my GP equatorial mount but the seller didn't have mounting rings, I saw helios mounting ring if 200 mm does somebody know if these rings are compatible?

#7 Don W

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Posted 11 November 2003 - 05:31 PM

Even if it doesn't have Starbright coatings, it does have some antireflective coating so reflections won't be a problem. As to SCT primaries not needing to be re-coated, well they do. Yes it's a closed system and the coatings will last a long time, but eventually they will need to be redone.

#8 Guest_**DONOTDELETE**_*

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Posted 12 November 2003 - 08:19 AM

Good news!
Another question, how it is possible to check the correct position of the secondary mirror on a old C8?
Is there any marks?
The owner told me that this scope was maintenanced in the past and I would like to check that this mirror was set back to the initial factory position.
Thanks,

SeB
http://users.skynet.be/astroseb

#9 Guest_**DONOTDELETE**_*

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Posted 12 November 2003 - 09:31 AM

SeB,
You will have to do a star test on a reasonably calm nite on a medium bright star, with the scope at ambient temp. All these factors are importaint when doing collimation. Also you will need to place the star exactly in the center of the field and dont use a dia. place the eyepiece directly into the visual back when doing the test. If at hi-mag the stars concentric rings all look equal and not off center your good to go. Otherwise you will have to recollimate, Polaris is a good star to do the test on it wont move out of field, be sure to re-center it ( the star)after ea, adjustment if you have to adjust the secondary.Did you get a operating manual with it? If you did it explains how to adjust the secondary. If not Ill explain further. Dave

#10 Guest_**DONOTDELETE**_*

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Posted 12 November 2003 - 11:22 AM

I do not have documentation for this C8.
I did a collimation with the owner who knows about that ( using the tree screws located at the front ) but the nite wasn't very good, so we planed to redo it again when conditions will be better and then get an accurate collimation. Anyway the images of Saturn I saw using this scope were quite ok when turbulence was going down. But we still don't know if the secondary mirror was re-mounted the correct way. I know that in the factory they rotate the secondary mirror to find the best match with the primary mirror. I do not know if they trace some marks to find this setting during a disassembling and reassembling of the scope
Do you know it?

SeB

#11 Guest_**DONOTDELETE**_*

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Posted 12 November 2003 - 06:07 PM

Ive read that the corrector is the one thats most importaint to re-assemble back into the same location IF you had to remove it for some reason. On a C8 it has been hand figured to match the primary, did he tell you he removed it or something? Why do you worry about the secondary being misplaced? Collimation has nothing to do with centering the secondary its just adjusting the angle to maximum focal point at the visual back. Getting everything concentric....Schmidts must be collimated very close for everything but the moon and DSOs. They loose importaint contrast necessary for faint planetary details if off even a smudge. Thats one reason I like my Mak so much over my C8, no collimation issues ever.Dave

#12 Guest_**DONOTDELETE**_*

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Posted 12 November 2003 - 06:08 PM

I believe you can download the manual from Celestron id check their website. Otherwise Meade has data on their Schmidt and it collimates the same as the C8 does so no diff. Dave

#13 Guest_**DONOTDELETE**_*

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Posted 15 November 2003 - 06:48 AM

In fact the secondary dropped on the primamy.. :foreheadslap:
The primary was damaged on the edge, but a really tiny damage. Hopefully the secondary was directly blocked!.
So the owner went to an astronomy store to fix it and clean the inside of the tube. We just would like to check that the optician did re-assemble it correctly.
So if you turn the secondary away from the original position, does it matter? Ok for the centering but what about if you remount the secondary upside down?

SeB

#14 Guest_**DONOTDELETE**_*

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Posted 15 November 2003 - 07:07 AM

Seb,
You cant physically mount the secondary upside down. You can however mount the correctorplate upsidedown. The secondary is the small mirror thats silvered on 1 side and attached via a hole in the corrector. It is the central pc with the 3 adjusting screws. It sounds like your talking about the corrector being inverted. Personally I dont have a clue if you can replace just a secondary but I have read several times that primarys and correctors are supposed to be matched or handfigured sets as close as can be had anyway. The secondary is supposed to be as perfectly centered as poss ive read also then just collimate as usual if its been removed. Putting the corrector back in the same spot requires making marks on the lens edge and the OTA before removal. I guess a look thru it on a nice nite will tell you whats up tho. Id be VERY leary of any Schmidt thats been screwed with and opened up and had optical parts replaced especially if not a matched set. Id definatly have to look thru it first and looking thru one that is still stock first would give you an idea of what you should expect to see and not see, IMHO. Dave

#15 Guest_**DONOTDELETE**_*

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Posted 16 November 2003 - 03:51 PM

Thanks for these info you gave me Dave ( and thanks to the others of course!!)
I will pick up the scope this monday or tuesday and I will try to check it on a stable sky when clouds will be gone..
I found a very interesting website about how to dismantle a C8. Unfortunately for you it is in French ( my main langage is french by the way..) but you can still visit it because this website is full of pictures taken during the dismantling. This is a great tools!!

The site address is :
http://www.bbayle.co...if_c8/index.htm

Clear skies!

SeB
:cool:

#16 matt

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Posted 16 November 2003 - 04:52 PM

AAARGH! This guy is pulling the guts out of a perfectly good C8, and he's neither an ordained minister or a doctor! Good the kids are in bed and don't have to see this!

Great link Seb. I always wondered how I'd do it if I had to. So far I've never done more than take out the corrector / secondary assembly. It's like the Heimlich maneuver: you feel you have to know it, but you dread having to perform it!

#17 Guest_**DONOTDELETE**_*

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Posted 30 November 2003 - 10:38 PM

been seeing a few C8s passing through astromart as of late. do these pop up for sale, regularly? saw one for $800, but i don't know much about these to know if that's a good deal or not.

best,
Chris

#18 miniventures

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Posted 01 December 2003 - 12:08 PM

Funny you should be asking this now. Just last night, a member of my astronomy club (and published astrophotographer) chastised me that I didn't have a scope or a camera available on my last cross country trip--I don't have a travel scope and haven't used a 35mm camera in years. I only missed a marvelous opportunity to photograph the aurora and a beautifully clear total lunar eclipse last month :tonofbricks: He suggested that I start looking NOW for an older, orange C8 to use for prime focus photography. NOW YOU HAD TO COME UP WITH ONE FOR $250 sigh. Well, actually, it wouldn't work for me as I need a mount too so I guess I'm saved :whistle: for now. I suppose I would say that I would jump on a deal like this in the state of mind that I'm in atm. LarryC

#19 Guest_**DONOTDELETE**_*

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Posted 07 December 2003 - 09:28 PM

I would....in a heartbeat! My own C8 is vintage 1982, and I can honestly say I would NEVER part with it! The optics (with Starbright)have always performed magnificently, and I am now planning on buying an LXD-55 and mounting my OTA to the mount. I will always have a use for my C8, and if you have a chance to buy an older C*, don't hesitate!

#20 Guest_**DONOTDELETE**_*

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Posted 08 December 2003 - 05:09 PM

SeB,
Have you had a chance to use the C8 yet? Ive been waiting a month and cant take the suspense anymore! or was it :grin:

#21 Guest_**DONOTDELETE**_*

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Posted 11 December 2003 - 06:00 AM

No, we got bad weather during few weeks in Belgium, I just received the rail to use it with my GP mount. Now weather is better but it is full moon...:foreheadslap:
I'll let you know the results after my first observation.

SeB :cool:

#22 Guest_**DONOTDELETE**_*

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Posted 18 December 2003 - 09:09 AM

SeB,
Have you had a chance to use the C8 yet? Ive been waiting a month and cant take the suspense anymore! or was it :grin:


Hello,

We got a very nice night!! :jump:
I did try the C8, after a quick collimation it gaves me very nice and sharp images. Saturn was great, jupiter too.
Open clusters in perseus were magnificent!!! :p
I did observe Orion's trapeze and saw 5 of the 6 six stars !! So finally I'm very happy that I bought this old C8. Only bad point is the focussing who is very difficult with a barlow 2X and a webcam. :( It is why I decided to build my own motorized crayford. I plan to replace my aluminium tripod by a wood one, too much vibrations...
Cheers, :roflmao:

SeB :cool:
Thanks again for all the advise you gave me guys!!
:bow:
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