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Maks VS SCTs

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#51 Napersky

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Posted 02 January 2013 - 07:48 AM

Zambuto Mirror referencing Rohr

http://www.zambutomi...oopticalcd.html

#52 skyjim

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Posted 02 January 2013 - 12:33 PM

My take after having owned many Intes Micro and some of the better china import MCT's is that standard C8's will produce a brighter image and some of the best samples of C8's I have owned will come close but a good 7" MCT will win. This changed once I got my hand's on a C8HD, the HD scope was more portable, cool down faster, had pinpoint stars out to the edge of feild and even the focusing system was as good but had a buttery smooth feel which the MCT's never did and no focus shift or flop noted thus far. I did RTFM when I got the edge scope and un locked the mirror locks before ever turning the focus knob, I think that's were many run into isssue's with the scope's focuser. As far as planet's and lunar the C8HD does as well as the IM M703 I owned, same amount of fine detail but a brighter image plus the scope does very well on double's and DSO, spank's the 703 on dso's. As many may rememeber I have alway's had a warm spot when it came to MCT's but here in NY the C8HD has so much more going for it plus if you need service or part's you can get it were the russian mct's are almost imposible. As far as new prices the C8HD is half the cost of a new 7" Russian MCT and about the same as the China made Synta 7" MCT's but the MCT's need around 2 hours plus to cool down were the 8HD is less than an hour.
Happy New Year to all the gang here on CN.
Jim

#53 johnnyha

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Posted 02 January 2013 - 01:14 PM

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.goo...1&ie=UTF8&ru...

Ugh! That is the most frightening thing I've ever seen Darren! :grin: 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.

#54 Darren Drake

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Posted 02 January 2013 - 01:20 PM

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.goo...1&ie=UTF8&ru...

Ugh! That is the most frightening thing I've ever seen Darren! :grin: 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.


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.

#55 johnnyha

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Posted 02 January 2013 - 02:26 PM

Ah! Thanks Darren.

#56 Napersky

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Posted 02 January 2013 - 03:07 PM

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.goo...1&ie=UTF8&ru...

Ugh! That is the most frightening thing I've ever seen Darren! :grin: 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.



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

#57 bcuddihee

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Posted 03 January 2013 - 12:12 PM

What is that strange radial spider pattern on the 2004 c11? I have seen this on one other c11 and wonder if it was just on the 2004 models.

#58 Darren Drake

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Posted 03 January 2013 - 12:52 PM

Brendan
I believe those radial patterns are caused by to much polishing pressure on the primary and the ribbed structures on the back of the primary imprinted into the figure as a result. I'm quite surprised celestron would let such a thing happen.

#59 bcuddihee

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Posted 03 January 2013 - 01:30 PM

Thanks Darren, a friend of mine has on of these c11's and I too am quite surprised that these were sold with this condition. It is evident even on a casual inspection of a due focused star. Bc

#60 Jeff B

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Posted 03 January 2013 - 01:34 PM

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


And whose C11 might that be :4 ?

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

#61 bcuddihee

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Posted 03 January 2013 - 01:37 PM

Hey buddy, Happy New Year!..tomorrow evening look promising for Hisey.
Any chance.

#62 Gord

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Posted 03 January 2013 - 08:04 PM

That was the first thing I thought of when I saw the image. I've heard of this on some newtonian mirrors, but had never seen these images before from SCT's.

I've never noticed anything on my C14 Edge sample.

Clear skies,

#63 TG

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Posted 04 January 2013 - 05:39 PM

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


And whose C11 might that be :4 ?

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


From what I've read, it's nothing to do with the primary but an imprint into the corrector's figure from the grooves in the master block used to facilitate the vacuum. Apparently Celestron later changed their master blocks to avoid this problem. Used to be fairly common, even seen in-focus, in the older Celestrons. Newer Celestrons don't have it.

Tanveer.






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