A well tuned C8 on Jupiter
Posted 20 November 2012 - 08:21 PM
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
Posted 20 November 2012 - 08:31 PM
Posted 20 November 2012 - 08:36 PM
Great! Jupiter is a wonderful sight. Looks like you have a fine telescope. Enjoy.
Posted 20 November 2012 - 09:20 PM
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.
Posted 20 November 2012 - 09:41 PM
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.
Posted 20 November 2012 - 10:24 PM
Posted 21 November 2012 - 06:18 AM
Posted 21 November 2012 - 07:33 AM
Posted 21 November 2012 - 09:17 AM
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.
Posted 21 November 2012 - 10:45 AM
Posted 21 November 2012 - 11:36 AM
On the night in question, magnifications up to 200x were used - as much as was useful given the disturbed atmosphere.
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.
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
Posted 21 November 2012 - 12:11 PM
Posted 21 November 2012 - 12:58 PM
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.
Posted 21 November 2012 - 02:39 PM
Posted 21 November 2012 - 02:52 PM
Posted 21 November 2012 - 06:13 PM
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
Posted 22 November 2012 - 08:33 AM
Posted 22 November 2012 - 04:27 PM
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.
Posted 23 November 2012 - 12:46 PM
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.
Posted 25 November 2012 - 09:43 PM
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.
Posted 25 November 2012 - 10:04 PM
Posted 26 November 2012 - 10:47 AM
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.