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Equipment Discussions >> Cats & Casses

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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
Pooh-Bah


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: Woodstock, 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
Pooh-Bah


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: Woodstock, 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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