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A well tuned C8 on Jupiter

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#1 Ed Holland

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Posted 20 November 2012 - 08:21 PM

Preaching to the choir this, I know, but still:

Last night was the first opportunity I have had, in nearly 12 months of ownership, to set my C8 upon glorious Jupiter. Previous viewing has been with the 5" refractor or 127mm(118) Mak. Both are of decent, if not outstanding quality, but it is to be admitted that my experience in this matter is limited.

All I can say about the C8 is WOW! despite very variable seeing, I was delighted at the detail and contrast that was evident at the eyepiece. I can't wait for a really steady night. Focussing was very crisp, without ambiguity, and when the sky co-operated Jove's disc possessed a hard edge against a dark night sky and fine detail in the cloud bands. I'm truly impressed with the optics. This performance also demonstrates the value - mentioned recently in other threads - of ensuring correct, precise assembly of all OTA elements - the 'scope was a wonky astigmatic mess when first received even after attempts at secondary collimation.

I do hope the weather co-operates for the next convenient shadow transit visible from this part of the world.

The instrument really seems to be a winner, a great example of its kind, and I couldn't be more pleased with its performance :jump:

#2 Asbytec

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Posted 20 November 2012 - 08:31 PM

Ed, Jupiter has been knocking my socks off. In fact, I think there is a pair over there. I am happy you're out in the elements spying on the King.

#3 Mitchell Duke

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Posted 20 November 2012 - 08:34 PM

Great! How did you align the optics?

#4 Starman27

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Posted 20 November 2012 - 08:36 PM

Ed,

Great! Jupiter is a wonderful sight. Looks like you have a fine telescope. Enjoy.

#5 Eddgie

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Posted 20 November 2012 - 09:20 PM

The C8 is an often under-estimated telescope.

If the optics are excellent (and many of them are) it can produce very satisfying planetary images.

Happy to hear your efforts were rewarded with some excellent viewing.

#6 charen

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Posted 20 November 2012 - 09:41 PM

I regret selling my Classic Orange C8 many years ago - some of the best planatary images I have ever had where though those optics. For some reason that one gave better images then more modern C8’s with superior coatings. A well collimated, well cooled C8 really is a great 'all round', portable, cost effective scope.
Don’t forget the Celestron C8 was the scope that helped revolutionize amateur astronomy in the 1970’s and has been Celestron’s best selling scope for decades.

Chris

#7 doug mc

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Posted 20 November 2012 - 10:24 PM

I am being converted to SCTs. After years observing jove with 6,8,and 10 inch Synta and GSO newts, 4,5, and 6 inch acro refractors from Synta, my latest scope a Celestron C6 SCT gave better images of the planet than all of them. It star tests nigh perfect to my eyes, and would give my 8 inch f/6 newt with a good Parks mirror a real chalenge.

#8 Dixie

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Posted 21 November 2012 - 06:18 AM

We had a night of very good seeing in Scotland over the weekend allowing me to get a decent collimation on my C8 - what a great view. It was the best I've seen Jupiter look in 30 years of observing. Put in the Denk standards it was knock your socks off time. I've owned the scope since 1994 and my love affair grows each year. Cooled and collimated it's an absolutely great scope - and one I can carry in one arm.

#9 Steve Darden

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Posted 21 November 2012 - 07:16 AM

Ed, what magnification were you using?

#10 thomas68

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Posted 21 November 2012 - 07:33 AM

Ed, I went through the same thing.Started with my 127 mak first real catastrophic, great little telescope.Bought a C8 XLT and never looked back! First time on Jupiter was amazing!

Enjoy,Tom

#11 t.r.

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Posted 21 November 2012 - 09:17 AM

I've gone full circle. Started with a small refractor and my first "real" scope was the C8. Got excited about the images in the apo refractors and touted them for many years and still do. A few years ago, wanting more aperture at reasonable cost, I have come back to SCTs with a C11XLT. With this scope, I saw the small white ovals in the polar regions of Jupiter that alluded me for decades with the smaller apos. I now have my eye on a C14. I will always have an apo for the crisp, sharp, wide-field and high contrast views. But now, I will also always have a large SCT in the stable to compliment the apo as well! ;)

#12 Eddgie

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Posted 21 November 2012 - 09:37 AM

I will always have an apo for the crisp, sharp, wide-field and high contrast views.


This has been my message for years now. Where APOs excel is in their superb off axis performance. People don't beleive me (or think I am crazy) when I tell them my primary use of my 6" APO is low power wide field work.

For the center of the field (Planets) it is all to easy to get better performance with a bigger scope. But getting a really wide field view that is free from coma and with a reasonably flat field is better done with a small refractor.

The C8 is a nice compromise though. Most worthwhile targets will fit into the field of a C8 with a 35mm Pan, and it will show them better than a smaller refractor, but still with some come.

And that is why I fell in love with the EdgeHD 8. Equal to to the very best refractors in off axis performance, and better than smaller refractors at the center of teh field.

C8s are excellent though, and as I get older and less inclined to want to mess with the big stuff, I seem my EdgeHD 8" taking a primary role in my observing.

But if the EdgeHDs had not come along, it would have been a standard C8, and I would never have felt bad about it.

The trick to being really happy with a C8 is to learn to star test properly, and buy and sell a few until you get one with really excellent optics. If the optics are excellent (and reasonable percentage of them are), they can be fine performers.

#13 GeneT

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Posted 21 November 2012 - 10:45 AM

I would be interested in an A B comparison of the views of Jupiter between your 5 inch refractor and your 8 inch SCT.

#14 Ed Holland

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Posted 21 November 2012 - 11:36 AM

To Steve Darden:
On the night in question, magnifications up to 200x were used - as much as was useful given the disturbed atmosphere.

To whduke
Achievement of good alignment involved - centering the corrector to place the secondary at the centre of the fromt housing. Then I discovered that the rear cell was tilted on the tube - somewhat loose actually. I corrected the cell tilt by trial and error, using the "concentric reflections" method as a gauge. This approach can be very accurate if one is careful about viewing postion. Lastly, a final fine adjustment of the secondary brought about a nice star test.

The scope fits my needs very well, and does so on a modest budget.

Gene:
I'll try and do an A/B with the 5" and come back to the thread. It's a bit tricky, since I've only one mount capable of carrying these instruments... a lot of juggling involved :)

#15 saemark30

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Posted 21 November 2012 - 12:11 PM

What rear cell, you mean the primary mirror has a cell?

#16 Ed Holland

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Posted 21 November 2012 - 12:58 PM

Yes, the rear casting, assembly, or whatever you want to call it, that comprises the baffle tube, primary mirror and focus mechanism.

I suspect inexperienced hands had tinkered with the assembly - the corrector & secondary were not in the typical orientation with respect to the main tube... Also possible is that the thump(s) it received in transit, severe enough to damage the corrector housing, also knocked the rear assembly loose from the tube. Either way, this was all fixable with care and a methodical approach.

#17 w orchid

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Posted 21 November 2012 - 02:39 PM

A well collimated, cooled down C8 will produce outstanding results.

#18 dscarpa

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Posted 21 November 2012 - 02:52 PM

If SCTs aren't good for lunar-planetary my C-9.25 hasn't heard the news. With very good seeing last night the amount of detail visable on Jupiter with a oh so sharp image using my first time in the SCT 12 Delos for 230X and had it awhile 10 XW for 270X was incredible! Ditto for the Moon with the Delos alone and in a 1.5X Siebert barlow for 350X! My cat has a Crayford so it comes in 20X-30X higher than stock. I keep collimation spot on. David

#19 Ed Holland

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Posted 21 November 2012 - 06:13 PM

Oh, I'm just happy because I feel as if I've finally reached the end of a long journey to see what I was getting with another, different, bigger telescope. Whilst I was very disappointed with my starting point - a scope so nearly ruined in transit, it turns out to have been an enjoyable and worthwhile effort to put things right.

The C8 does seem like a very capable scope - it is great that a modest outlay can put this sort of capability for light gathering and resolution in the hands of so many of us. And I can store it easily without upsetting domestic harmony.

Now many journeys can be enjoyed amongst the Solar system and beyond :)

#20 Dan McConaughy

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Posted 22 November 2012 - 08:33 AM

I had an 8" D&G refractor, but the planetary views were never as good as in my C14, given the seeing.

#21 saemark30

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Posted 22 November 2012 - 04:27 PM

Have you compared the C8 with a better 8" Newtonian?
I know a 8" F/6 can show a lot of white ovals in the eq belts and around the red spot.
A decent 10" F/6 is even better.

#22 Ed Holland

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Posted 23 November 2012 - 12:46 PM

No I have not... And that would make an interesting study.

I chose a C8 (used) as they are inexpensive, could ride on my existing mount and would be easy to store. Plus I was intrigued by the design. I didn't have planetary viewing foremost in mind at the time, so much as light gathering and the chance to view some feinter things - a step up from the 5" scopes.

#23 Steve Darden

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Posted 25 November 2012 - 09:43 PM

I was out tonight viewing Jupiter with my C8 and all I can say is WOW. This was the best view of Jupiter I have had by far since one special night with my 10 inch dob several years ago. The detail tonight was just amazing. At times, it looked like a photo with incredible fine detail across the whole planet.

To be honest, I was beginning to think my C8 was a dog because it usually shows about the same planetary detail as my 4 inch APO. I recently figured out that my local seeing is the problem because no matter which direction I look, I'm looking over someone's roof.

Well tonight, my C8 proved itself to be an excellent sample and the APO got stomped like a narc at a biker rally.

#24 Asbytec

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Posted 25 November 2012 - 10:04 PM

Jupiter has been putting on quite a show, and the best I have seen it - ever. There is a lot going on, and when seeing cooperates with a collimated and cooled scope, yes, the views are just phenomenal.

#25 REC

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Posted 26 November 2012 - 10:47 AM

Steve, encouraging report! Jupiter is now rising a little earlier and from my observing spot (back yard) it's coming up over open field and not neighbor houses so better views.

I too have been seeing more detail than ever on Jupiter on good seeing nights in all my scopes. I do see I need to tweak my 8" SCT as I'm not able to get the moons pinpoint or round shape. The collimation is off a little to one side, so need to fix that.

Enjoy! Bob






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