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Trading a C11 for a C9.25

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#51 astro_bob

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Posted 21 November 2005 - 05:44 PM

Jerry,

No I welcome your test... I'm not familiar with what you are planning to do (test methodology), but any good semi-controlled test are better than impressions... I realize it's hard to control every variable short of taking both OTA's to have them tested in an optics lab for mirror and corrector plate quality, but a good out-in-the-field testing methodlogy will catch my attention any day over impressions... It's not that I don't believe people but I think it's all too easy to be misled by uncontrolled variables and thus misequate a poorer seeing evening with scope a was better than scope b. I'm sorry if I came across like a putz :) it was not intended!

Dixie: I agree, but it should be possible to control for this too, it just requires leaving both scopes out for an extended period of time (ideally with the OTA open in the back to allow ambient air in (probably not the best idea on a night with lots of dew)...

Coming from the medical science realm, I know how easy it is to miss a variable and come away with the wrong interpretation entirely... Also, our perceptions are highly (mis) influenced by the black box between our ears :), and so impressions are hard to 100% trust esp. if there are other (i.e. financial, or personal) motives involved (e.g. one scope belongs to the reviewer and one does not).

Bob
 

#52 Derwin Skotch

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Posted 21 November 2005 - 06:08 PM

Thank you!!! :) It seems as if a few opinions (albeit ones reported on in text) have been inappropriately turned into a broad generalization about the quality of 1 vs 2... Unless a proper statistical analysis is done and the proper tests are performed to "prove" the 9.25 is a better optical instrument, all bets are off... Some of the these tests could be nothing more than good examples of the 9.25 vs. a poor example of an 11... It seems far more likely to me that mirror to mirror variances are leading to these conclusions.


As I understand it, the 9 1/4 has longer focal length optics and longer focal length optics are easier to manufacture. Could it be that the 9 1/4's perform consistently better because of this?
 

#53 jrcrilly

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Posted 21 November 2005 - 07:29 PM

As I understand it, the 9 1/4 has longer focal length optics and longer focal length optics are easier to manufacture. Could it be that the 9 1/4's perform consistently better because of this?


That's probably not significant. The primary is about F/2.4 instead of F/2.2 or thereabouts. That's not a huge difference. It's spherical anyway - paraboloids are the ones that are harder to make at faster F ratios.
 

#54 JerryWise

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Posted 21 November 2005 - 08:48 PM


Hey Bob, I was more throwing out the intentions of the test hoping to subject the test to constructive criticism. I did some comparisons on EPs a few months ago and got an excellent suggestion from Don P. and some others. I also hope to get some test on a Radiological Test Wedge with line pair readings to get true resolution (on that target under the conditions at the time). Here is how I will run the test:

1. Setup the CGE with the STV autoguider.

2. Put both OTAs in the observatory in the early afternoon so they will ride the ambient temp down.

3. Have the stock (so it will represent visual response) Canon 300d cooling also.

4. I'll then mount one of the OTAs determined by a coin flip and slew to Vega. There I'll focus using a Celestron 12mm illuminated reticule with gradient marks. I'll defocus until the concentric rings exactly fill the central gradient circle (about 1/3 the EP area). I'll then mount the camera at prime focus and take a photograph (if it represents a good collimation image). This image will be used for collimation representation of each OTA.

5. Then using a Stiletto I'll focus using the Canon 300D adapter. I'll then but a Hartman mask on and photograph the Hartman image. This will be done for both OTAs so the focus can be compared by a reader.

6. Then I'll slew to a cluster (to be determined that night) overhead and photograph it. This will be done with both OTAs inside 30 minutes.

7. I'll then move to Andromeda and photograph that.

8. Then maybe Neptune or Uranus but I don't want to get into planetary becuase one shot images just don't cut it. Toucam stacks seem to be the way to get detail and that can be another test.

9. Then M45 and M27

10. If I get the time I'll move both OTAs downstairs and setup the X-Ray test wedge and do a line pair resolution test.

In the past, many have question aspects of these test. Focal length, what the instrument was really intended for, design, etc. For me, nothing matters but the side by side comparision of what the two instruments actually "see". If one instrument or EP can "see" more then..... well... you can "see" more with it.

I got myself in trouble running test like this. I did this with my Meade 102ED and Takahashi FS-102II. I knew how the test would come out before ever cranking it up. Decided to go ahead anyway even though the Tak was going to slay the Meade. Resolution, stars, deep sky... all just as I layed out above. Went over and over the results. The Takahashi now belongs to another. It did great in the test. Flawless. I saw more with the Meade.
 

#55 mistyridge

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Posted 21 November 2005 - 10:48 PM

Bob,
I think thats an issue as is atmospheric conditions, a 11in scope is going to be more picky then a 9in scope when it comes to seeing.

i agree with this since I use both. Rarely are the conditions at my location good enough to make the C11 shine.
 

#56 LittleDob

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Posted 21 November 2005 - 11:41 PM

While I totally agree with the statements that variance in quality between individual scopes can significantly influence perspectives that are then generalized to include all 9.25s and 11s, the fact that we are even having this debate makes me think the 9.25 is a great scope.

For fun, lets call it a tie and assume both scopes produce exactly the same view and image. The fact that the 9.25 is cheaper and lighter makes it a really appealling option. In particular, the lighter weight should make it more stable on a given mount. These are serious considerations when purchasing.

Having said that ain't nothing wrong with a C11.

Jason
 

#57 Guest_**DONOTDELETE**_*

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Posted 22 November 2005 - 12:06 AM

I am amazed that after all these years, there is still this debate going on.

The 9.25 is a sharper scope than the 11" period, end of story.


If it were that simple, the debate would have been over by now. Some folks prefer one, other folks the other. Neither group is more correct than the other.



Geez John, you have owned just about every scope out there. Yet I have yet to see you buy a 9.25.

What do you average? A new scope every two months or so. Stick up an 11 vs. a 9.25 --- the differences are in favor of the 9.25.

My pal Ed Ting and Dan Mounsey years ago came to this conclusion. And those guys are pretty heavy hitters in my book.
 

#58 astro_bob

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Posted 22 November 2005 - 12:08 AM

Interesting, so even with extended cool down time the C11 never equilibrates? Do you open the cell up?
 

#59 Guest_**DONOTDELETE**_*

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Posted 22 November 2005 - 12:16 AM

I think you were unhappy with your C11 because you were unable to collimate it, you said so in the previous C11 vs. C9.25 thread.
 

#60 Guest_**DONOTDELETE**_*

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Posted 22 November 2005 - 12:20 AM

Interesting, so even with extended cool down time the C11 never equilibrates? Do you open the cell up?


In my experience with the carbon C11 the cool down time was very long. I'd open the cell up for about an hour and then start using it. It took from 10pm to 3:30 AM on colder nights for cool down. Several times it never cooled down. With a C11 cabon tube a CAT cooler is a very good investment.
 

#61 astro_bob

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Posted 22 November 2005 - 12:23 AM

Jerry, Your testing methodolgy seems spot-on insofar as one can as one cannot clone a mount to avoid the need to switch the OTA :) When you say, Radiologic Test Wedge - are you using this instrument as a means of proper positioning of the OTA for a line pair test? I am unfamiliar with optical testing protocols... I think I've seen a CT of a small Meade once, looked neat but I'm uncertain as to whether or not mirror flaws can be seen with the limiting resolution of a CT.
 

#62 Guest_**DONOTDELETE**_*

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Posted 22 November 2005 - 12:24 AM

I think you were unhappy with your C11 because you were unable to collimate it, you said so in the previous C11 vs. C9.25 thread.


Absolutely Robert! The C11 never seemed to deliver the sharpness I had with my previous 9.25. SO I TWEEKED AND TWEEKED... and I never could get that C11 to 9.25 sharpness.

I am sure I would have been very happy with the C11 had I never had the experience with that wonderfull 9.25 I first purchased.
 

#63 Guest_**DONOTDELETE**_*

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Posted 22 November 2005 - 12:33 AM

Piano,

You seem to be the only one here making emphatic statements, however I have yet to see any scientific data, let alone planetary sketches or planetary images from you, demonstrating the sharpness or advantages you keep talking about.
 

#64 Guest_**DONOTDELETE**_*

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Posted 22 November 2005 - 12:52 AM

Well, I state my experience. Personally, I don't want wishy washy advice from people. I'm giving it straight as I experienced it.

As for scientific data... give me a break Robert! Good gosh, I have a real job.;)

People come here to get advice from people who have real world experience. I'm just stating mine.

I purchased a 9.25, sold it for an 11 and then sold that for a 9.25. That's putting your money where your mouth is in my book.

Besides, my advice is not for those who have already made a commitment. It's for those about to make the plunge.

I don't want them to have to spend the kind of money I did to find out the 9.25 was best.
 

#65 Guest_**DONOTDELETE**_*

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Posted 22 November 2005 - 01:02 AM

Right, eveyone respects your personal experience and opinion.

I think it's the emphatic statements premised on a C11 that was not properly collimated that some might take issue with.

I am amazed that after all these years, there is still this debate going on.

The 9.25 is a sharper scope than the 11" period, end of story.


 

#66 Guest_**DONOTDELETE**_*

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Posted 22 November 2005 - 01:33 AM

The C11 was collimated quite well. The C11 was not as sharp as my 9.25's. Simple as that for me.

And if you really respected my opinion and experience you would not attack it so.

If there is such an issue with this, go out and buy a 9.25 and do a comparison --- then let others know your impressions. Personally, I'd rather hear advice from someone who has tried both scopes for a while rather than use statistics alone.

Let's take the binoviewer for example. Using numbers alone, you get less light into each eye using a binoviewer. This would leave a person with no experience with a binoviewer to conclude that single viewing is better for dimmer objects. BUT, in practice, use of a good bino with batwings, allows your eyes to relax and assimilate more information. In practice, I see fainter objects with my binoviewer. That is MY personal experience and one many people who thinking about buying one would love to hear about.

It's the same with my 9.25 -- I see a sharper image.

That's why people read these boards.
 

#67 Guest_**DONOTDELETE**_*

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Posted 22 November 2005 - 01:54 AM

Ok, since there is no scientific data, planetary sketches or planetary images to back up your emphatic statement, how about a detailed planetary observation report describing the seeing conditions, magnification used and which high resolution features were sharper in the C9.25 vs. the C11?

I am simply addressing the "unequivocal" comment you made above, which appears again to be based on a C11 that was not properly collimated. Larger scopes are more difficult to collimate and take longer to cool down. However the effort is certainly worth it. Not saying so is misleading to new buyers as well.

I am amazed that after all these years, there is still this debate going on.
The 9.25 is a sharper scope than the 11" period, end of story.


 

#68 sixela

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Posted 22 November 2005 - 04:52 AM

I am simply addressing the "unequivocal" comment you made above, which appears again to be based on a C11 that was not properly collimated.

According to *you*. You have nothing to back up the fact it wasn't collimated, except for your belief that it must not have been well collimated because it doesn't fit your view of the world. The owner did in fact state that it *was* well collimated.

I have no trouble believing the C9.25 was sharper. It's more forgiving with respect to collimation, the baffling *is* better, it cuts through bad seeing just a tad better, it's slightly easier to focus it, and the nights the additional resolution advantage of an 11" scope with respect to a 9.25" scope is noticeable could, for that poster, have been scarce.

9 inches of aperture support 400x on planets with ease, and there aren't that many of us who can claim to use much more on planets *regularly*. I have nights where my 6" mask for the 16"er shows me more detail at 200x than my full aperture...and the nights that my 16" is not humbled by a good 8" APO for a good view of planets are not nonexistent, but they're rare indeed┬╣.

As Suiter writes quite correctly, observing is filtered through a wobbly stack. And no matter how precise you are (unless your name is Damian Peach), the C9.25's stack is oh so slightly less wobbly , and the difference in resolution with a C11 isn't *that* large, unless the seeing is stupendous.


Larger scopes are more difficult to collimate and take longer to cool down.

Actually, how difficult a scope is to collimate depends on the f/ratio of the primary, not on its size (if you ever collimated an Orion Astroblast, you'd know ;) ). And yes, the C9.25 has a slower primary.

--
┬╣If you want to tell me the 16" is surely miscollimated, go ahead - but please do so in the reflector forum ;).
 

#69 Guest_**DONOTDELETE**_*

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Posted 22 November 2005 - 05:12 AM

I am simply addressing the "unequivocal" comment you made above, which appears again to be based on a C11 that was not properly collimated.


According to *you*. You have nothing to back up the fact it wasn't collimated, except for your belief that it must not have been well collimated because it doesn't fit your view of the world.




The exact exchange between him and David Knisely in the previous C9.25 vs C11 thread, go back and read it.
http://www.cloudynig...ll/fpart/3/vc/1


David:
"The 11 is a bit fussier than the 9.25 is as far as collimation is concerned, as even slight collimation errors can lead to a slight degredation in the high-power performance.

Piano:
EXACTLY David!
Being a guy who wants a sharp image, I was CONSTANTLY tweaking my collimation knobs on the 11". I was satisfied once in over a year of consistent use - ack!"



If he's not satisified with the collimation, sounds like it's not properly collimated to me.

My "view of the world" has nothing to do with this ;)
But my view of planetary observing and imaging surely does, as well as my view of avoiding making such "unequivocal" comments as

I am amazed that after all these years, there is still this debate going on.
The 9.25 is a sharper scope than the 11" period, end of story.



on Cloudy Nights without any substantial supporting evidence that one's opinion is "the end of story."
 

#70 sixela

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Posted 22 November 2005 - 08:20 AM

If he's not satisified with the collimation, sounds like it's not properly collimated to me.


Not necessarily. Sometimes, when you expect a good image but don't get it, it can prompt you to recheck the collimation - even when collimation has nothing to do with the problem.

That happened to me a few days ago before the mirror was fully cooled down (it was freezing; even though I had put the mirror outside with fans blowing on it for some time, it wasn't enough) - on casual inspection, I mistook a mirror box current (causing a compressed diffraction ring structure on one side) for coma, only to find out collimation was OK (to my utter surprise) when checking it with tools. Closer inspection of the star test pattern revealed it couldn't have been coma, and I just waited 20 more minutes and the effect was gone.

On an SCT, given that star testing is a much more fickle business, I would have come to the same conclusion with respect to the collimation's correctness quite some time later...
 

#71 JerryWise

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Posted 22 November 2005 - 08:30 AM

Jerry, Your testing methodolgy seems spot-on insofar as one can as one cannot clone a mount to avoid the need to switch the OTA :) When you say, Radiologic Test Wedge - are you using this instrument as a means of proper positioning of the OTA for a line pair test? I am unfamiliar with optical testing protocols... I think I've seen a CT of a small Meade once, looked neat but I'm uncertain as to whether or not mirror flaws can be seen with the limiting resolution of a CT.


Bob, here is the linkto a test done on eyepieces with the resolution wedge. I made a test box with rear illumination of the line pair wedge. It determines the ability of an optical chain to discern ever smaller lines. The chain seeing the largest number of lines resolves better.

On the cloning of the mount, actually we may already have that addressed. On the CGE I have a Losmandy Dual Dovetail clamp. The OTAs can be placed side by side. I don't thing that will be necessary though since the test will be run at the same time (within 30 minutes) and the ED80 mounted now will be used for centering targets.

As the participants here are still jockying for position in the opinion polls (seems the thing to do lately in politics as well) one has to wonder if personal preference has anything to do with OTA choice. Would the world not be a mess if we all preferred the same thing. Everybody would want to marry the same rare perfect person. And some, like myself, would never get pair-bonded. :(


I mean, I compared the Meade 102ED to my Tak FS-102II. I like the performance of the 102ED better. Just a personal thing. I see some referencing of previous post here illustrating a given poster may be contradicting themselves. I have to say things change over time. I posted glowing opinions of the FS-102. As more information came online (I bought a 102ED) my opinions changed. That's the way it works. If somebody has a tough time early on collimating an OTA and works it out weeks or months later this doesn't negate their current opinion. Also, the quest for scientific proof to validate a position brings a smile. Not a lot of that floating around on either side that I see. I don't see scientific proof as a requirement for someone to state in their opinion a given OTA is sharper. The "end of story" is taken by me to mean end of story in their opinion. I think there is something there worth investigating if someone is willing to make the statement.

And for cool down time...... :grin:. Won't be long before there will be a cool down edict for this thread
:grin: :grin:
 

#72 LivingNDixie

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Posted 22 November 2005 - 08:33 AM

piano,

I got two questions for ya.
1. What would you say your main observing site has for seeing conditions on average?

2. When viewing the Moon did your C11 ever show more detail then the C9.25 while side by side when conditions allowed?

For me, my site at home has some interesting seeing. If an object is above the neighbors house the seeing is no where near as nice as when it is over the grassy area in front of that same house. Also I tend to get more glare while observing since the neighbors love running their dusk to dawn porch lights. My dark sites are a mixed bag with one being on the side of a mountain and the other being in a cleared area of a state wilderness area. The mountain site is ok because its cooler in the summer but the seeing is not as good becuase of constant breezes. The wilderness area is darker and less windy, but dew is more of an issue. I rarely do planetary viewing from either dark site since I can do that at home.
 

#73 astro_bob

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Posted 22 November 2005 - 01:47 PM

Jerry,

I'm impressed with the previous tests... Very well thought out. It would be interesting to add some blinded subjective opinions to the mix too... If you have a few buddies around, it would be interesting to cover the OTA to disguise it (east to do as the 9.25 and 11 are the same length just not the same diameter) and tell them to judge the image qulaity based upon a few predetermined parameters (sharpness, detail, etc.)... This of course would be easier if both OTA's were setup at the same time.

I'm eagerly awaiting the results and wish I was a bit closer to you as I would invite myself over for this shootout :lol: As you have probably read, I'm thinking of picking up a new scope and am curious as the C11 interests me but if the 9.25 performs at the same level, it may be a better choice for future astrophotgraphy as it would present less of a weight burden on a mount. Interestingly you have pretty much ever scope I am considering (the Orion 80ED will be purchased no matter what) - the RCX (hesitant as the QC bugs seem bad at the moment and Meade's customer service seems to be below Celestron and that scope could be an electronic nightmare!!! :) ), the Celestron C11 (actually the Orion rebadged C11, but customer service is great), the LX200GPS (QC better, but again I have a classic so I'm not sure this is a good route), or the Meade SN10 (neat scope for fast imaging but I'm not sure it would be the best for observing).
 

#74 JerryWise

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Posted 22 November 2005 - 01:58 PM


Thanks Bob for the compliments on the scopes. I wish I could say they were all well thought out but the "on sale" factor often determines what comes here. Matter fact, everything in the signature was either EBay, Astromart or on sale. You can get more stuff that way.

On the blind test. What I am going to try is do the whole test photographically. Then write an article with the images at each stage side by side. At the end I'll add some observations only available visually. This way everyone can decide for themselves. The images may not turn out but this is the plan so far.
 

#75 Don W

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Posted 22 November 2005 - 07:46 PM

Ok people, we have been down this road far more times than I would care to count. This issue has been beat to death and the same people show up and say the same things over and over again. I'm going to lock this thread and ask you all to move along to something else.
 


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