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The focal length does matter though in the sense that in many cases it's easier to fabricate high quality slower optics than it is to fabricate high-quality fast optics

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I'm in the dangerous realm of knowing almost enough to follow all these cool discussions of wavefronts and such, but have certainly not played with enough examples of all these scopes to offer any but one maybe useful question. Most SCTs are f/10. Most Maks are longer, maybe f/15. Would not the typical Mak's additional focal length by itself make for a narrower field, but also inherently greater clarity at the eyepiece? Longer focal lengths are more tolerant of optical imperfections, making this an apples-to-oranges comparison (or, at least "Red Delicious" to "Granny Smith").

This thread mentions the importance of assuring that every component of an SCT is properly centered and rotated. Orion61, if anything salvages the salt-encrusted C8 you are fixing for me, it will be the careful adjustment of its optical train.

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If we assume identical apertures which scope design tends to be the better planetary performer the Mak Casses or SCTs? The Maks tend to be considerably more expensive especially in the larger apertures

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my 8 inch STF-Mirage is an f/10 Mak and I am comparing it directly to my former C8 SCTs (regular and Edge)

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my 8 inch STF-Mirage is an f/10 Mak and I am comparing it directly to my former C8 SCTs (regular and Edge)

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That is the perfect technical comparison! Would you be comfortable commenting on the relative prices of these scopes? Not what you paid if you found a great deal, but typical street prices. Then again, it may be that Russian manufacturers have a significant advantage in pricing. What might a similar scope cost if Takahashi or Astro-Physics built it? It's a big world, with many factors distorting the purely technical discussion. 

Enough soap boxing from me! Point made, or, with apologies, over-made. Honestly, with the distortions of cost in mind, the technical discussions are far more interesting! Certainly there are connoisseurs who pay what they must for that last edge of performance, and lucky buyers paying little for great scopes. So, before I have to discipline myself for hijacking the thread, which'll it be, which is better for planetary work: Schmitt or Mak?!

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This is a fair question. My STF-Mirage is similar to the TEC and A-P Maks, with super smooth optics and machined parts fitting perfectly together. They don't make a lot of these, the optics have been tested and certified to be better than 1/8 wave, and the "street price" to get one into the US is about $4000.00. Compare that to the cost of a mass-produced SCT: C8 ($1000) or C8-HD Edge ($1300) and you can see why more folks opt for the mass-produced SCT, even with average optics.

Are the views $3000 better? Maybe not, but I like the views through my scope and I also enjoy the fit, finish, and no-hassles of quality merchandise.

Cheers,

Ron

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Hey Mark,
In the null test image the dark and lighter areas represent imperfections on the order in this case of somewhere on the order of a little more than a millionth of an inch from perfect which since the shadings are very subtle suggest this is a very good scope optically. I have done the same test on numerous other scopes and have seen all forms of aberrations quite obviously as the test is very sensitive. I have recently thought of the idea of starting an image gallery of various scopes showing the null test images along with pics of the scopes. Would anyone be interested in this??

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I have recently thought of the idea of starting an image gallery of various scopes showing the null test images along with pics of the scopes. Would anyone be interested in this??

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This is first time that I heard a Questar 3.5" outperforms a 130mm APO refractor. It is even more surprised it is Tak TOA 130 which is among finest refractors.

Theoretically it is completely impossible for 3.5" Mak to outperform 5" APO refractor: aperture and central obstruction unless something is way off with the 130mm.

Was your scope fully cooled? How about collimation? was it spot on?

Few reviews that I read say a quality 4" APO refractor outperform a Questar 3.5" which does make sense to me.

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Linear resolution is a function of focal ratio and focal ratio alone.

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...Mak-Casses have fast primary mirrors, maybe F/3 or so, with a magnifying secondary and a corrector...In my way of thinking, one has to think of a compound scope as having fast, generally spherical optics.

A MAK-Newtonian is like a standard Newtonian...no trick secondary mirrors to slow down the focal ratio by a factor of 4 or 5... this is probably another reason, besides the small secondary, that makes the MAK-Newt a good performer at high magnifications.

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Here is a series of very revealing comparisons from Rohr's site. I think the best SCT here is maybe the C8 Nextstar from 2005 and the best Mak is the 8 inch Intes Alter. Rohr has many other examples on his website but this is a revealing series nontheless.

http://translate.googleusercontent.com/translate_c?depth=1&ie=UTF8&ru...

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Ugh! That is the most frightening thing I've ever seen Darren! This makes me reconsider the C11 EdgeHD I had my eye on... Surely a Tec Mak, Intes Micro or Mewlon would be a better bet for a smoother mirror. Those commercial mirrors are just ghastly.

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Here is a series of very revealing comparisons from Rohr's site. I think the best SCT here is maybe the C8 Nextstar from 2005 and the best Mak is the 8 inch Intes Alter. Rohr has many other examples on his website but this is a revealing series nontheless

http://translate.googleusercontent.com/translate_c?depth=1&ie=UTF8&ru...

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Ugh! That is the most frightening thing I've ever seen Darren! This makes me reconsider the C11 EdgeHD I had my eye on... Surely a Tec Mak, Intes Micro or Mewlon would be a better bet for a smoother mirror. Those commercial mirrors are just ghastly.

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Actually I don't believe the mirrors are the cause of some of the roughness. I believe the corrector plates are the cause of most of he errors but that's only a suspicion since the correctors are much more difficult to fabricate than a spherical mirror.

Edited by Darren Drake (01/03/13 02:17 PM)

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Here is a series of very revealing comparisons from Rohr's site. I think the best SCT here is maybe the C8 Nextstar from 2005 and the best Mak is the 8 inch Intes Alter. Rohr has many other examples on his website but this is a revealing series nontheless.

http://translate.googleusercontent.com/translate_c?depth=1&ie=UTF8&ru...

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Ugh! That is the most frightening thing I've ever seen Darren! This makes me reconsider the C11 EdgeHD I had my eye on... Surely a Tec Mak, Intes Micro or Mewlon would be a better bet for a smoother mirror. Those commercial mirrors are just ghastly.

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I wouldn't worry about the C11 Edge HD. Darren's good example here is his C8, my C8 1990s vintage is also an excellent performer. An Edge HD C11 should be much much better than those classic C8s.

Mark

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What is that strange radial spider pattern on the 2004 c11? I have seen this on one other c11...

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And whose C11 might that be ?

Yeah I figured it out last week when I was looking at pictures of a disassembled C14 and noticed the ribs on the back of the mirror. Also, as the mirror cools, those ribs will probably show themselves as well. I notice in my C11 they're much less visible but still there and fairly easy to see even after the scope has stabilized thermally . I catch a very faint hint of them in the C14 as well but I never would have gone looking if I had not seen the photo of the back of the C14 mirror.

Jeff

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