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Charlie HeinAdministrator
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Reged: 11/02/03

Loc: 26.06.08N, +80.23.08W
EIGHT-INCH SHOOTOUT
      #5317069 - 07/14/12 08:07 AM

review of 3 eight-inch telescopes

By Lawrence Carlino


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mwedel
Works with Sauropods
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Reged: 12/16/07

Loc: Claremont, CA
Re: EIGHT-INCH SHOOTOUT new [Re: Charlie Hein]
      #5317719 - 07/14/12 04:01 PM

Very interesting, fair, and useful review. Many thanks for doing all the work, and writing it up so the rest of us can benefit.

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Scott in NC
Mad Hatter
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Reged: 03/05/05

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Re: EIGHT-INCH SHOOTOUT new [Re: mwedel]
      #5317750 - 07/14/12 04:26 PM

Nice review, Larry, and a very interesting read! I've never looked through a Mak-Newt before, and always wondered how they were optically.

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David Knisely
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Reged: 04/19/04

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Re: EIGHT-INCH SHOOTOUT new [Re: mwedel]
      #5317830 - 07/14/12 05:30 PM

Quote:

Very interesting, fair, and useful review. Many thanks for doing all the work, and writing it up so the rest of us can benefit.




I dunno about being exactly 'fair'. The Mak-Newt is Intes, which is a premium telescope maker. The others are mass-market and probably can't match the Intes optical quality (kind of like comparing the performance of a Ferrari to a Chevy). Maybe if the Dob's mirrors had been refigured by Lockwood, and an optical window installed, then one might be able to come to some conclusion, but as it stands now, all we can say is that the author compared the scopes. Clear skies to you.


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mwedel
Works with Sauropods
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Reged: 12/16/07

Loc: Claremont, CA
Re: EIGHT-INCH SHOOTOUT new [Re: David Knisely]
      #5318052 - 07/14/12 08:49 PM

Quote:

Quote:

Very interesting, fair, and useful review. Many thanks for doing all the work, and writing it up so the rest of us can benefit.




I dunno about being exactly 'fair'. The Mak-Newt is Intes, which is a premium telescope maker. The others are mass-market and probably can't match the Intes optical quality




All points that Larry acknowledged, frequently, in his writeup. For example:

Quote:

Having obtained an 8” Russian-built Intes-Micro Maksutov-Newtonian from Astronomics last spring, I was anxious to determine if a standard Newtonian and a Schmidt-Cassegrainian could stand up against its well-documented optical quality.




and, regarding the dob:

Quote:

This scope was the real surprise of the trio. Despite its bargain price, this conventional Newtonian optic delivered sharp, high-contrast images.




and concluding:

Quote:

Overall, considering the strengths and weaknesses of all three telescopes, one might conclude that no instrument “blew away” the other two. That COULD occur with a defective unit, pinched optics, bad collimation, or a thermal disaster – but it didn’t happen here. In essence, you do “get what you pay for,” and only each individual’s priorities can determine if a premium instrument is worth its purchase price.




So, since Larry acknowledged that the three scopes come at different price points up front, and still found that no one scope consistently blew away the other two, what part of that is unfair?

Or are you saying that it's not Larry's shootout in particular that is unfair, but that any comparison of three scopes at such wide price points would be unfair?

In which case, and speaking as a Chevy driver, I appreciate knowing that the Ferrari did not blow the doors off the other two. My "car payments" are already expensive enough!


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jrbarnett
Eyepiece Hooligan
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Reged: 02/28/06

Loc: Petaluma, CA
Re: EIGHT-INCH SHOOTOUT new [Re: Charlie Hein]
      #5318162 - 07/14/12 10:30 PM

I certainly concur with your conclusion, Larry. A well-made refractor of larger than 5" is more than a match for *any* 8" obstructed scope in my experience, at least on double stars, planets and the Moon. On the other hand, give the Tak and any of those 8-inchers a go on something dim and extended, and see if it changes your ranking (NGC 188 about 4 degrees from the Pole Star, for example).

Regards,

Jim


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jrbarnett
Eyepiece Hooligan
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Reged: 02/28/06

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Re: EIGHT-INCH SHOOTOUT new [Re: David Knisely]
      #5318167 - 07/14/12 10:33 PM

Intes is Russian. Ever been in a Russian car? Plane? Tank? I think you're putting too much stock in Intes word-of-mouth marketing and the little pieces of paper they ship with their scopes. Ferraris are Italian. Ladas are Russian.

Regards,

Jim


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stevew
Now I've done it


Reged: 03/03/06

Loc: British Columbia Canada
Re: EIGHT-INCH SHOOTOUT new [Re: jrbarnett]
      #5318194 - 07/14/12 10:55 PM Attachment (271 downloads)

Excellent article.
Although I was not surprised at the results.
As the Lawrence said, if I was only able to own one scope it would be the C8.

Steve


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Mauro Da Lio
professor emeritus


Reged: 09/12/04

Re: EIGHT-INCH SHOOTOUT new [Re: stevew]
      #5318432 - 07/15/12 04:49 AM

I think that comparison has been carried out at too low magnification to be meaningful. I read of 140x on Jupiter and 240x on Mars.

A well cooled scope, decent figured, on fair seeing should be able to get crisp images at higher magnifications. I used to go 400x and more with a GSO 8" dobsonian on Mars, revealing crisp images with details not seen at 200x. Jupiter holds less magnification but still a lot more than 140x (300x and plus were not infrequent with the GSO).

Overall, the magnification that a scope can hold while keeping crisp images (the roll-off magnification, see Mel Bartels' page on the end http://www.bbastrodesigns.com/ratemirrors.html ) is the primary indicator of image quality.

Overall I think that comparing scopes at so low magnification means that the bottleneck is not the scope but some environmental condition such as seeing, local seeing, local thermal disturbances, internal thermal disturbance, and so on.

One question: did the newtonian have a boundary layer extraction fan? It makes a huge difference: http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/4122861/page/0/view/collapsed/sb/5/o/all/fpart/1/vc/1


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rflinn68
Carpal Tunnel


Reged: 03/09/12

Loc: Arkansas
Re: EIGHT-INCH SHOOTOUT new [Re: Mauro Da Lio]
      #5318556 - 07/15/12 08:49 AM Attachment (247 downloads)

I own an 8" & 10" Newt and a 8" & 10" SCT. I just bought the 2 sct's used for a great price thinking I would sell one but I love them both and dont see me parting with this lightweight jewel anytime soon.

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Daniel Mounsey
Vendor (Woodland Hills)
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Re: EIGHT-INCH SHOOTOUT new [Re: rflinn68]
      #5318623 - 07/15/12 10:04 AM

This is a great comparison because it teaches beginners what really happens in real world situations. Members should take note of this and start making comparisons of their own. There's WAY too much optical theory going on in the forums and way less hands on experience in real world comparisons and it shows. There's not enough reviews like this anymore.

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Daniel Mounsey
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Reged: 06/12/02

Re: EIGHT-INCH SHOOTOUT new [Re: David Knisely]
      #5318624 - 07/15/12 10:06 AM

Quote:

Quote:

Very interesting, fair, and useful review. Many thanks for doing all the work, and writing it up so the rest of us can benefit.




I dunno about being exactly 'fair'. The Mak-Newt is Intes, which is a premium telescope maker. The others are mass-market and probably can't match the Intes optical quality (kind of like comparing the performance of a Ferrari to a Chevy). Maybe if the Dob's mirrors had been refigured by Lockwood, and an optical window installed, then one might be able to come to some conclusion, but as it stands now, all we can say is that the author compared the scopes. Clear skies to you.




Regardless, it helps others understand how certain telescopes compare to others in real world situations.


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Jim Rosenstock
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Reged: 07/14/05

Loc: MD, south of the DC Nebula
Re: EIGHT-INCH SHOOTOUT new [Re: Daniel Mounsey]
      #5318689 - 07/15/12 11:02 AM

Quote:

Regardless, it helps others understand how certain telescopes compare to others in the real world situations.




Concur.


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Mauro Da Lio
professor emeritus


Reged: 09/12/04

Re: EIGHT-INCH SHOOTOUT new [Re: Daniel Mounsey]
      #5318778 - 07/15/12 12:14 PM

Quote:

There's WAY too much optical theory going on in the forums and way less hands on experience in real world comparisons and it shows. There's not enough reviews like this anymore.




I totally disagree. Any experience has to be "interpreted" (it is so even when it does not seem). In facts "conclusions" are nothing but "theories". The conclusion that scope A is better than B might be flawed by some factor that has been not recognized (it was the case of boundary layers before Alan Adler for example).

Carrying out comparisons, means trying to set the experiment within a theoretical framework and identifying all the interference factors. Otherwise one might come out with believing that "objects only moved as long as they were pushed" as has actually been the case for nearly two thousands years ( http://csep10.phys.utk.edu/astr161/lect/history/aristotle_dynamics.html ).

Were people before Galileo correct? Yet they were doing experiments. The fallacy was they were doing ONLY "interpretation" of the outcome of the empirical data.


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Daniel Mounsey
Vendor (Woodland Hills)
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Reged: 06/12/02

Re: EIGHT-INCH SHOOTOUT new [Re: Mauro Da Lio]
      #5318934 - 07/15/12 02:08 PM

I understand what you're saying and I agree but not entirely. The observer may not know why a certain telescope is performing better of worse than another. It happens sometimes with what little comparisons are made these days but that's not the point. The point is that beginners need to be taught more about what actually occurs in the field. In the meantime, people are throwing numbers around like it's lifes bread. There's plenty of that to gargle in the forums. It's the observers responsibility to get themselves up to snuff on what's going on with the instruments in the field but field testing and comparisons are the REALITY of what is taking place whether the observers know what is going on or not. It may not always be conclusive unless the observer is highly experienced and knows what he or she is talking about but I'd rather see these kind of reviews rather than listening to these continuous lengthy threads from people reading about optical theory, not getting in the field. People are passing judgements about telescopes they have no experience using or comparing and drawing premature "conclusions" based on some stats. So what, anyone can read a brochure. You think all those performance specs on supercars are reality? Not even close. You are correct, but you are also incorrect. I am correct, and I am also incorrect BUT 95% of forums are optical theory NOT actual experience based on enough field comparisons. With that said, it's great to see some comparisons for a change.

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tonyt
professor emeritus


Reged: 09/02/09

Loc: Australia
Re: EIGHT-INCH SHOOTOUT new [Re: Daniel Mounsey]
      #5319363 - 07/15/12 08:30 PM

I think the most important point from the review is that they're all good scopes and observers can be happy with the scope they already own.(assuming it's a decent sample)

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azure1961p
Postmaster
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Reged: 01/17/09

Loc: USA
Re: EIGHT-INCH SHOOTOUT new [Re: tonyt]
      #5319591 - 07/15/12 11:06 PM


I enjoyed Larrys article a lot.

I think the comparisons were fair in that there were not external issues warping the comparisons, ie; one scope over looking a roof another a grassy meadow for example. The scopes are hardly equals but thats what made this review one of the more interesting. I think Larry did a terrific job. He loves his refractors - that I know from previous reviews hes done and done quite well. Still, I never detected an unfair bias that needlessly slighted the other scopes.

Im a big believer that a great factor in leveling the playing field in terms of visual observation is the dedication and persistance of the astronomer. An experienced and seasoned observer often sees more despite CO size, etc etc.

I thought the whole article was a success.

Pete


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KeithC
member


Reged: 08/23/06

Loc: Atlanta GA
Re: EIGHT-INCH SHOOTOUT new [Re: Charlie Hein]
      #5319790 - 07/16/12 04:32 AM

Larry, I had a lot of fun reading your article and it sounds like you had a lot of fun doing the comparisons. I always enjoy it when people do hands on, direct comparisons, in the field. Thank you for sharing your observations with us!

KeithC


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Chucky
sage
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Reged: 04/16/10

Loc: Dublin, Ohio
Re: EIGHT-INCH SHOOTOUT new [Re: KeithC]
      #5319841 - 07/16/12 07:16 AM

<< There's not enough reviews like this anymore. >>

Certainly not in American astronomy magazines.


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Mauro Da Lio
professor emeritus


Reged: 09/12/04

Re: EIGHT-INCH SHOOTOUT new [Re: Chucky]
      #5319936 - 07/16/12 09:17 AM

Filed testing and comparisons is the REALITY under the condition that the "experimenter" perfectly knows what is going on. Otherwise conclusions might establish the wrong cause-effect relation.

It had been so for long time for reflector scopes, addressed as intrinsically poor for high resolution, until the boundary layer phenomenon was discovered.

Knowing from theory that reflection is not different from refraction shuold have forced people making "real life test" to search for another explanation (searching the real cause of poor performance), but that did not happen. So, framing an experiment in a theoretical solid pre-existing background is of paramount importance.

In the case of Larry's test there is a weakness that is worth to be considered: magnification were too low.

Edited by Mauro Da Lio (07/16/12 09:19 AM)


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