(Viewed 2,203 times)

[-=CROMAN=-]

I found a listing for a Celestron C8 or C8+, the owner doesnt know, CL. The asking price is $500.

She told me it comes with the mount but one of the legs is broken. What do you guys think?

Celestron 8" Schmidt Cassgrain Telescope - great condition. Comes with various sized lens's. case, lens cap, adjustable, capability to connect to a 35 mm camera ( camera available on separate listing ). I contacted skiesunlimited.com for the information, and was told it is a rare telescope, great condition, very clean.

[patrickm]

In my ignorance, $500 for a working 8" scope and mount seems a good deal, tripod or no. Am sure the wiser amongst us will chime in.

[wwpierre]

Yes, yes, a thousand times yes.

The Byers drive is superior.

adsabs.harvard.edu/full/2000IAPPP..79...17B

I have been watching these on eBay because I don't have a Schmidt-Cassegrain in my collection. $500 is the going price for the OTA only. This has a (probably repairable) tripod, wedge, 50mm right angle finder, and the best drive. Please let me know if you pass up the deal.

[Paulie pchris00]

I was thinking along Patrick's line, only it seems that the wiser has already chimed in.

[-=CROMAN=-]

I picked up the super c8 this evening. couple things wrong so far. The wedge bolts that secure it to the tripod are missing. I need to find those.

The power cord for the byers worm drive is missing. this may be a beast to find. so the drive is useless right now

2 of the 3 tripod leg clamps are broken off. I may need to drill through the tubes and use pins to hold the legs in place.

Collimation is completely off! Jupiter was nothing more than a blur. unfortunately i have never collimated one of these so i have zero idea what to do. Advice?

most of the issues are very minor. The corrector plate looks like it has dried dew internally but the mirror is almost spotless.

ill post some pics throughout the weekend. I do have some on facebook now.

[-=CROMAN=-]

i collimated as best i could tonight. i have the secondary disk in the center of the defocused star. Jupiter came into view but it was nowhere near as sharp as my z10. Ill take apart the diagonal tomorrow morning and give it a good cleaning.

I did hit the orion nebula and was able to get a nice view of the trapezium with a 20mm plossl. Still, not the type of view i was expecting.

The scope also came with an off axis solar filter. The instructions for cleaning the filter say to use isopropyl alcohol. This filter had been used and has a couple finger prints on the glass. if the prints have been on there for over 8 years can it decay the glass coatings? should i even try to clean this and use it?

[Chicago Astronomer - Astro Joe]

Rich,

Excellent on your new acquirement.

If it weren't so cold now, I would recommend removing the corrector plate, cleaning and re-installing - making sure it's orientated properly in the OTA. SCTs are a delicate beast. It likes it's mirrors close to alignment, lest it delivers poor views - like coma and blurring. Unlike a robust Newt reflector that can still deliver views way out of collimation...not so with a SCT.

By pass the right diagonal for now, pop in an eyepiece right into the the OTA and view your targets straight through...and see if it improves the image.

Collimating the secondary is not as simple. You can follow along with my collimation adventures on the C11, but...

Pop off the orange cap covering the secondary and put a mark on the three screw orientations. Then with a phillips screwdriver set them in all the way in. Do not over tighten, just let the driver turn the screws and let the tip of the driver slip off when it wants to.

This should set the secondary equally down and provide a starting point to adjust the screws outward in small increments. A star is good, but I have found that Jupiter makes for a good coarse object to adjust the secondary to start out with. Target the planet and unfocus. Then, when you get the secondary equally centered, focus and see if you get good views of Jupiter, then move on to a star and finish with precise concentric ring adjustments.

Prints on coated glass can eat away at the surface with the acids. The alcohol will not destroy the filter, unless it's so far gone that the coating will flake/rub off. And if it does that...then it would be unsafe to use anyway. Go for it with cotton balls and use a lot of them. But use 90% Isopropyl Alcohol, not the stuff you find in the dollar store. Walgreens has it and it's much purer.

Then, when you get it all together...I would flock the OTA and bring out as much dark contrast as you can.

I hope to see this scope soon.

[patrickm]

What Joe said, and here:
uncle-rods.blogspot.com/2009/07/zen-and-art-of-telescope-collimation.html

If you have a hard time finding 90+% IPA, let me know. I've got a guy.

[-=CROMAN=-]

I think im going to need that 90+% Patrick!

I found an issue with the OTA while collimating. I noticed that when I leveled the tube to perform a daytime collimation the tube moved about a 1/4". When I put the ota at 90 degrees the ota slid back into seated position.

I thought that maybe the screws that hole the tube to the back bracket were loose. I tightened them all up a bit and put the tube back at horizontal to the ground. the tube slide down and out of the back again.

Seeing as though i have not opened anything up yet do you think it could be the mirror not seated correctly? Does the mirror even have part in this?

Im not going any further until i get this corrected. Its not wonder i cant get this collimated! I dont see any signs of damage anywhere.

Please chime in...

[erikruud]

I got 99% IPA at Meijer.

[-=CROMAN=-]

What are your opinions on the Celestron cg-5 computerized mount? Would it be adequate for my C8?

www.telescopes.com/telescope-accessories/mounts-and-tripods/celestroncg5computerizedmount.cfm

[Chicago Astronomer - Astro Joe]

It would work just fine.

But, are you going to install a dovetail rail on the OTA to mount it on the new mount..(if you get it).

[-=CROMAN=-]

I would have to install a dovetail correct?

Perhaps I could pay a certain someone with the proper tools to do it for me? Someone into chainsaws and old records would most likely have the required skills to perform such a task.

But where do you find such a person?

[Chicago Astronomer - Astro Joe]

Done.

If we are going to do that, then a thorough cleaning and modding is called for, since we will be opening the OTA for the dovetail job.

I recommend Flocking as well.

The problem now is the cold temps, as the Astro workshop is not heated. We may have to wait till early spring, but it gives you the time to assemble the parts needed.

No pay, just a favor.

Could be next week, could be in five years at 3am. That or a MaxwellSt, hotdog.

[headdunce]

Dec 20, 2011 16:32:07 GMT -6 Chicago Astronomer - Astro Joe said:

The problem now is the cold temps, as the Astro workshop is not heated.

What ya need?
www.carguygarage.com/garageheaters.html


www.carguygarage.com/staff.html

[RobbW]

Dec 20, 2011 6:58:34 GMT -6 -=CROMAN=- said:

What are your opinions on the Celestron cg-5 computerized mount? Would it be adequate for my C8?

www.telescopes.com/telescope-accessories/mounts-and-tripods/celestroncg5computerizedmount.cfm

That's the same one I have on my C8! Works well enough for me, especially after I Hypertuned it. Just make sure you use proper voltage and amps when powering the mount, otherwise it acts all whack on crack!

[-=CROMAN=-]

Joe... I put protostar flocking in a couple weeks ago. I cleaned the corrector plate and air dusted the primary. It was in great shape, hardly any dust.

Robb... I'm probably going to order the mount after the holidays. Perhaps you can give some advice on hypertuning. I was reading that teh mount, as is, performs bad in cold weather due to some cheapo gunk smeared on the gearing at the factory.

[Chicago Astronomer - Astro Joe]

Oh hell then...

It's a hour project.

Zip, zip....done.

[-=CROMAN=-]

The last time I heard zip, zip done I ended up in the emergency room!

[Chicago Astronomer - Astro Joe]

I first heard - zip zip done - here...



It'll take care of itself.