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Equipment Discussions >> Cats & Casses

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Ed Holland
Carpal Tunnel


Reged: 06/16/10

Loc: San Jose, CA and Oxford, UK
A well tuned C8 on Jupiter
      #5530970 - 11/20/12 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


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Asbytec
Guy in a furry hat
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Reged: 08/08/07

Loc: La Union, PI
Re: A well tuned C8 on Jupiter new [Re: Ed Holland]
      #5530983 - 11/20/12 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.

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Mitchell Duke
Post Laureate
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Reged: 04/22/08

Loc: Georgia
Re: A well tuned C8 on Jupiter new [Re: Asbytec]
      #5530986 - 11/20/12 08:34 PM

Great! How did you align the optics?

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Starman27Moderator
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Reged: 01/29/06

Loc: Illinois, Iowa
Re: A well tuned C8 on Jupiter new [Re: Asbytec]
      #5530989 - 11/20/12 08:36 PM

Ed,

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


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Eddgie
Postmaster
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Reged: 02/01/06

Re: A well tuned C8 on Jupiter new [Re: Ed Holland]
      #5531067 - 11/20/12 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.


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charen
Carpal Tunnel
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Reged: 05/28/05

Loc: New Zealand
Re: A well tuned C8 on Jupiter new [Re: Eddgie]
      #5531105 - 11/20/12 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 C8ís with superior coatings. A well collimated, well cooled C8 really is a great 'all round', portable, cost effective scope.
Donít forget the Celestron C8 was the scope that helped revolutionize amateur astronomy in the 1970ís and has been Celestronís best selling scope for decades.

Chris


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doug mc
super member
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Reged: 03/21/09

Loc: Tamborine Mountain Australia
Re: A well tuned C8 on Jupiter new [Re: charen]
      #5531178 - 11/20/12 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.

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Dixie
super member


Reged: 03/30/06

Loc: UK Latitude 53.3 north
Re: A well tuned C8 on Jupiter new [Re: doug mc]
      #5531564 - 11/21/12 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.

Edited by Dixie (11/21/12 06:35 AM)


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Steve Darden
professor emeritus


Reged: 07/29/07

Loc: GA
Re: A well tuned C8 on Jupiter new [Re: Dixie]
      #5531606 - 11/21/12 07:16 AM

Ed, what magnification were you using?

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thomas68
professor emeritus


Reged: 01/25/11

Loc: North west Indiana
Re: A well tuned C8 on Jupiter new [Re: Steve Darden]
      #5531616 - 11/21/12 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


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t.r.
Post Laureate
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Reged: 02/14/08

Loc: Upstate NY
Re: A well tuned C8 on Jupiter new [Re: thomas68]
      #5531750 - 11/21/12 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!

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Eddgie
Postmaster
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Reged: 02/01/06

Re: A well tuned C8 on Jupiter new [Re: t.r.]
      #5531794 - 11/21/12 09:37 AM

Quote:

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.


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GeneT
Ely Kid
*****

Reged: 11/07/08

Loc: South Texas
Re: A well tuned C8 on Jupiter new [Re: Ed Holland]
      #5531924 - 11/21/12 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.

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Ed Holland
Carpal Tunnel


Reged: 06/16/10

Loc: San Jose, CA and Oxford, UK
Re: A well tuned C8 on Jupiter new [Re: GeneT]
      #5532053 - 11/21/12 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


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saemark30
Pooh-Bah


Reged: 02/21/12

Re: A well tuned C8 on Jupiter new [Re: Ed Holland]
      #5532129 - 11/21/12 12:11 PM

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

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Ed Holland
Carpal Tunnel


Reged: 06/16/10

Loc: San Jose, CA and Oxford, UK
Re: A well tuned C8 on Jupiter new [Re: saemark30]
      #5532227 - 11/21/12 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.


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w orchid
Pooh-Bah


Reged: 04/23/07

Loc: Tampa, Fl
Re: A well tuned C8 on Jupiter new [Re: Ed Holland]
      #5532405 - 11/21/12 02:39 PM

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

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dscarpa
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Reged: 03/15/08

Loc: San Diego Ca.
Re: A well tuned C8 on Jupiter new [Re: Ed Holland]
      #5532427 - 11/21/12 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

Edited by dscarpa (11/21/12 04:25 PM)


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Ed Holland
Carpal Tunnel


Reged: 06/16/10

Loc: San Jose, CA and Oxford, UK
Re: A well tuned C8 on Jupiter new [Re: dscarpa]
      #5532754 - 11/21/12 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


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Dan McConaughy
sage


Reged: 11/11/06

Loc: LA
Re: A well tuned C8 on Jupiter new [Re: Ed Holland]
      #5533525 - 11/22/12 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.

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saemark30
Pooh-Bah


Reged: 02/21/12

Re: A well tuned C8 on Jupiter new [Re: Dan McConaughy]
      #5534182 - 11/22/12 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.


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Ed Holland
Carpal Tunnel


Reged: 06/16/10

Loc: San Jose, CA and Oxford, UK
Re: A well tuned C8 on Jupiter new [Re: saemark30]
      #5535425 - 11/23/12 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.


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Steve Darden
professor emeritus


Reged: 07/29/07

Loc: GA
Re: A well tuned C8 on Jupiter new [Re: Ed Holland]
      #5539463 - 11/25/12 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.


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Asbytec
Guy in a furry hat
*****

Reged: 08/08/07

Loc: La Union, PI
Re: A well tuned C8 on Jupiter new [Re: Steve Darden]
      #5539485 - 11/25/12 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.

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REC
Post Laureate
*****

Reged: 10/20/10

Loc: NC
Re: A well tuned C8 on Jupiter new [Re: Asbytec]
      #5540056 - 11/26/12 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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Ed Holland
Carpal Tunnel


Reged: 06/16/10

Loc: San Jose, CA and Oxford, UK
Re: A well tuned C8 on Jupiter new [Re: REC]
      #5540706 - 11/26/12 05:30 PM

Last night, I treated the 5" refractor (Meade AR5) to some Jovial viewing . Whilst not a view for view comparison to the C8 on one night, I believe I am able to offer some interesting points of comparison. Most observations below were made at ~170x

1) Overall brightness - obviously less in the 5", though the C8 is almost verging on too bright for comfort, and I may experiment with a ND filter.

2) Overall presentation: the 5" has some color from chromatic aberration. This is to be expected. There is also some spherical aberration (mild under-correction according to crude star testing). Both these factors give the scope a unique character in image presentation and perhaps a reduction in contrast and difference in colour rendition compared to the C8. That said, during steady moments, some finer structure was glimpsed in the atmospheric belts. The C8 would definitely reach well beyond in terms of detail when seeing allows.

3) Settling time - this was interesting: Conditions were cool, but above freezing, outside temp ~50F and falling. At first I ascribed the unremarkable views to poor seeing, as detail on the Jovian disc seemed to come and go, disrupted in bouts of "high frequency" disturbance. Even during settled moments, however, there seemed to be a soft character to the images with focusing seemingly indeterminate.

BUT, as the glass and tube acclimated over the course of ~30min the view transformed. Focus became sharp & easily found, with the initial softness in the image greatly abated. It also seemed that in the later stages of cooling the purple fringing from CA was much reduced. Quite a transformation! At this point a shadow transit had just begun, and a well defined dark (purple-ish) pin-point shadow appeared on the disc of Jupiter whilst a small pin-point of light hovered just outside.

The fun part for this observer is enjoying the presentation made by any intrument. The 5" and the C8 each have a place in my affections. It was interesting that cooling of the refractor was more an issue than I had anticipated. Yes, it is the instrument of choice if I'm not able to plan ahead, yet not ready to go at full power straight out of the starting block. This offsets a little of the issues one might raise to the C8, or even the 5" Mak. Seeing conditions are the major factor at my location which determine visible detail - often the 5" will show all there is to be seen. On the plus side, it is very resistant to condensation - making it a great (safe) choice on dewy nights.

Ed


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orion61

*****

Reged: 10/20/07

Loc: Birthplace James T Kirk
Re: A well tuned C8 on Jupiter new [Re: Ed Holland]
      #5540748 - 11/26/12 06:08 PM

Ed when you talk about your C8 with optical issues, it is exactly what I have been saying for 30 years, the best optical sets will look bad when not assembled priperly.
When I service scopes this is one of the areas I spend a lot of time. I never trust the marks! I have even found a one owner B7L years ago that was giving horrible views
that had the corrector Facotry installed backward!!
It is not unusual to have correctors over an inch off!
Thanks for the refresher to all of us and don't give up on that CAT. I own a Dynamax DX6, 6" with some of the best optics I have ever seen (once I got everything lined up correctly)
The Primary was mounted at an angle, the secondary was 1/4"
off center! I got it cheap cause it was HORRIBLE! but it was in Mint shape because it sit on a shelf for 30 years, it was so bad.. I must say it is cute, and it turns heads when people look through it and say These are all supposed to be junk arent they?
Peace my friend, great hearing from you.
Larry


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Dwight J
scholastic sledgehammer
*****

Reged: 05/14/09

Loc: Lethbridge, Alberta, Canada
Re: A well tuned C8 on Jupiter new [Re: orion61]
      #5540819 - 11/26/12 06:58 PM

Well the joke is on me. I had a Super C8 for many years and one still night 25 years ago I had it set up observing Jupiter beside a C11 owned by another club member - an orange tubed one. The C8 was easily showing more than the C11 which I judged at the time to be due to the atmosphere not still enough for the bigger scope. I sold the C8 about 10 years ago like an idiot and now own a C11! Looking back at that night I think that the C11 was not in collimation or was a poor example. I have an 8 inch MN now but the OTA weighs as much or more than my old C8 mounted in the fork arms and base. You can't go wrong with a C8 and if you have one hang onto it or you will regret it.

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oldtimer
Pooh-Bah
*****

Reged: 11/13/08

Loc: Lake County Illinois
Re: A well tuned C8 on Jupiter new [Re: Ed Holland]
      #5541124 - 11/26/12 09:47 PM

I have a C8 from 1983 which I keep st up on a super polaris mount in my garage. I often carry it a few feet out onto the driveway for Jupiter peeks. When the air is steady it gives great views. However my best planetary scope is a 10" F6.5 newt which on its massive EQ mount doesn't see much action anymore. Age is catching up on me.

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James_826
member
*****

Reged: 02/09/12

Loc: Beggs, Ok
Re: A well tuned C8 on Jupiter new [Re: Steve Darden]
      #5541952 - 11/27/12 11:51 AM

Quote:

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.




What EP were you using?


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Steve Darden
professor emeritus


Reged: 07/29/07

Loc: GA
Re: A well tuned C8 on Jupiter new [Re: James_826]
      #5542196 - 11/27/12 01:58 PM

I was using a 17mm Sirius Plossl (120X), 14mm ES82 (145X) and 11mm Televue Plossl (185X). It's rare that I can ever get a clear view with anything near 200x but everything came together that night. The 14mm was the best, though. Prior to viewing, I was able to tweak the collimation at 580X (7mm ortho + 2X barow)which is just amazing because I normally can't get a clear airy disk to form due to the seeing. In fact, I never saw an airy disk with the 10 inch dob I used to own. I can see the air disk most nights with smaller scopes such as my APO and the 127 Mak I use to have.

Edited by Steve Darden (11/27/12 02:00 PM)


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