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Equipment Discussions >> Refractors

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JJK
Carpal Tunnel


Reged: 04/28/08

Re: AP 10" Maksutov vs TEC 200 Fluorite apo new [Re: Mike Clemens]
      #5582231 - 12/21/12 10:27 AM

Quote:

I'm on team TEC but I've got to say those two images by the 10" mak are just awesome.




You should see how the AP Mak-Cass performs at the eyepiece.


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Scott99
Carpal Tunnel
*****

Reged: 05/10/07

Loc: New England
Re: AP 10" Maksutov vs TEC 200 Fluorite apo new [Re: Peter Natscher]
      #5582411 - 12/21/12 12:27 PM

Quote:

You're right! That's why I'm observing with the largest ap scope I can manage (a 24" SST) while I'm able to. I'm 62 now, strong and healthy and will surely someday become less interested in transporting this large scope to and from dark sites. Right now, It takes no more energy for me to transport to a remote site my 24"er than my AP 175 along with at it's ATS transportable pier, its AP 900 GTO mount, its 2 x 19 lbs. of counter weights, etc. I have been observing frequently with a friend who has always used his AP 155EDFS on a 900GTO and AP pedestal for his observing of DSO's. He is very satisfied with how deep he gets with DSO's with his 6" ap scope. He has just completed the H400 list. He wants to do the HII list next but I recommended that he get at least a 12" Dob to do that with to enjoy them more. I've observed both of these lists years ago with 18"-20" Dobs -- totally enjoyable! He comes over and occasionally takes a look through my 24" scope and is WoWed at how bright and easily seen my objects are, but happily returns to his dimmer looking DSO's in his 6" APO. He says the sharpness of his views always make him the happiest -- it's the pin-point stars with nice diffraction patterns. The brightness factor with a larger ap Dob isn't as important. Dobs slightly mushy stars just don't do it for him. I say he hasn't seen really deep stuff after 20 years of observing, and I'm glad I am enjoying the deep stuff. To each his own




Peter, yes there's nothing I enjoy more than making the rounds of the big scopes to check out the views! That's the fun of observing clubs & events, I always take home some unforgettable views.

I actually enjoyed doing the H400 with a Star 12 ED. It's been done with scopes as small as 55mm, although you're pretty much doing a survey at that point, not going to see much detail.


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Rachel W
member


Reged: 07/10/12

Re: AP 10" Maksutov vs TEC 200 Fluorite apo new [Re: Mike Clemens]
      #5583424 - 12/22/12 12:19 AM

Hi All:

Loved reading this entire thread, wow! There's just a wealth of deep and wide knowledge and so many love affairs with each to their own favorite mistress of the sky. And let's not kid ourselves, in the end we view with what we love to view with - it's personal and it's special; just like any mistress should be. For after all, they are expensive, fickle and can make for heated household debate (lol).

I can't appreciate large aperture viewing to a great extent yet, having recently moved up from a C80 achro to a TEC 140 APO. Of course, I'm completely blown away and have been since I got the 140 in September - it's a keeper for sure. I also like my 9x63 and 25x100 binos too for that quick and lazy tour around the sky; life is good, well except I have to view in LA and have only made it once out to my friend's home in the desert where the sky is awesome.

However, I can't get over the idea of using a world-class 10" mak, f10. I'm 70 and a robust lady and I can handle the TEC 140 and the CGEM well enough by myself, but they aren't light by my reckoning - a 10" mak, hmmm. What I'd love to do . . . (fantasy time) is to partner with a great designer/builder and create a really light-weight 10" mak that cools down fast and follows the naturally occurring lapse rate and mount it on something that is super accurate and truly easy to move/transport/set-up, and has a 1/10th-1/12th wave front at the business end of the scope - that's all. If I were younger, I'd seriously think about financing such a project (it's just money, right?!), with a great decade or two to enjoy and truly master a very special precision instrument.

This thread got me to thinking again . . . and heck, 70 is the new 60 - right?

Thanks to every one here for the wonderful thread; it was delicious. I'll keep checking in here.

Clear skies and great views,

Rachel


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Daniel Mounsey
Vendor (Woodland Hills)
*****

Reged: 06/12/02

Re: AP 10" Maksutov vs TEC 200 Fluorite apo new [Re: Rachel W]
      #5583550 - 12/22/12 03:05 AM Attachment (74 downloads)

I spent extensive hours working with the TEC200 apo, TEC200 Mak cass and the TEC250 F-20 Mak cass in this image. The TEC200 apo and TEC250 cass were owned by a good friend of mine John Curry. The TEC250 Mak was pitted against a particular C9.25 and a world class 8" TMB triplet. Each one left indelible memories. The TEC250 was technically challenging.

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Daniel Mounsey
Vendor (Woodland Hills)
*****

Reged: 06/12/02

Re: AP 10" Maksutov vs TEC 200 Fluorite apo new [Re: Daniel Mounsey]
      #5583551 - 12/22/12 03:07 AM Attachment (69 downloads)

TEC250

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Daniel Mounsey
Vendor (Woodland Hills)
*****

Reged: 06/12/02

Re: AP 10" Maksutov vs TEC 200 Fluorite apo new [Re: Daniel Mounsey]
      #5583552 - 12/22/12 03:08 AM Attachment (58 downloads)

Here it mounted in on a 16" LX200 mount. It was a beast.

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Astrojensen
Post Laureate
*****

Reged: 10/05/08

Loc: Bornholm, Denmark
Re: AP 10" Maksutov vs TEC 200 Fluorite apo new [Re: Daniel Mounsey]
      #5583589 - 12/22/12 04:31 AM

But the views! We want to hear about the views!


Clear skies!
Thomas, Denmark


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Paul G
Post Laureate
*****

Reged: 05/08/03

Loc: Freedonia
Re: AP 10" Maksutov vs TEC 200 Fluorite apo new [Re: Daniel Mounsey]
      #5583612 - 12/22/12 05:53 AM

Quote:

The TEC250 was technically challenging.




Can you elaborate?


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Peter Natscher
professor emeritus


Reged: 03/28/06

Loc: Central Coast California
Re: AP 10" Maksutov vs TEC 200 Fluorite apo new [Re: Paul G]
      #5584072 - 12/22/12 01:11 PM

I bet it was in its thermal characteristics.

Quote:

Quote:

The TEC250 was technically challenging.




Can you elaborate?




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Daniel Mounsey
Vendor (Woodland Hills)
*****

Reged: 06/12/02

Re: AP 10" Maksutov vs TEC 200 Fluorite apo new [Re: Peter Natscher]
      #5590525 - 12/26/12 11:36 PM

That is correct. You could ask Yuri, but I would imagine the meniscus must have been pretty thick. The OTA weighed ton. I had a lengthy conversation with Bryan Greer about it while we were hanging out in New York during NEAF a few years back. If I recall correctly, Bryan had been trying to assist Yuri with working the fans internally within the OTA but at the time it was being done, it still seemed to be in the experimental phases. Bryan could probably elaborate more accurately if asked.

The TEC250 was a beautiful scope. When I first saw it, Curry had it up at Pinos. One of the guys I was with was one of the most experienced planetary observers in the group and it was our impression that Curry had little experience at Pinos because we were wondering why he would even bother setting up such elegant for such a crummy location for seeing. Pinos isn't my favorite location for planets in fact I hate the place for that. We invited Curry to Charlton. The temperature drop was quite subtle but even still, Curry had some issues stabilizing the thing. Maybe it was caused from head in his vehicle, who knows.

We spent a few sessions with it. We had some beautiful telescopes set up at the time and some great observers present. The idea was that the internal fans were to "stir" the thermals, but it was still too difficult in fact after the fans were turned off, Curry expressed some issues about actual heat plumes coming off the tiny, heated electrical motors. He even tried putting compressed gas into the OTA which turned cool upon release and we knew there was no way that would work.

I realize the AP is well ventilated, but even still, the entire optical train has to work in harmony. An anonymous owner in the CN forums has expressed that it's been easier for him to use his 5" AP apo with pleasing results. Larger aperture of high quality will produce the best angular resolution on planets, but thermals can degrade any aperture. The best results come from hard labor at the eyepiece. I can not state that enough. People can throw the numbers around all they like, but until an observer is actually in the field dealing with this stuff, it's just a numbers game.

It doesn't tell the truth about what really happens. People think I'm a refractor lover and I'm not. I love Newtonians and my experience has taught me that ultimately, the Newtonian with proper tuning is the ultimate setup, but it comes with some work. The reason I'm suggesting the 8" apo is because there are many observers who have no idea how amazing they can be and I mean STUNNING! So much detail it would blow your mind, all in high definition. I've tested several large apos and the image quality is consistently reliable; you can count on it to work if it's a good sample. If people are just going to throw numbers around, then I can assure others they need to spend some time in planetary bootcamp. I'm talking about visual planetary observations, not imaging.

If you can get a large scope working on a good night then boy are you in for a beautiful surprise, but the key is that it's gotta work for you! I love the TEC200 Mak. I have nothing but admiration for Yuri. He does beautiful work overall, particularly his refractors.


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Paul G
Post Laureate
*****

Reged: 05/08/03

Loc: Freedonia
Re: AP 10" Maksutov vs TEC 200 Fluorite apo new [Re: Daniel Mounsey]
      #5590963 - 12/27/12 10:45 AM

Quote:

Maybe it was caused from head in his vehicle, who knows.




You guys obviously have more fun observing than I!

Quote:

We spent a few sessions with it. We had some beautiful telescopes set up at the time and some great observers present. The idea was that the internal fans were to "stir" the thermals, but it was still too difficult in fact after the fans were turned off, Curry expressed some issues about actual heat plumes coming off the tiny, heated electrical motors. He even tried putting compressed gas into the OTA which turned cool upon release and we knew there was no way that would work.

I realize the AP is well ventilated, but even still, the entire optical train has to work in harmony. An anonymous owner in the CN forums has expressed that it's been easier for him to use his 5" AP apo with pleasing results. Larger aperture of high quality will produce the best angular resolution on planets, but thermals can degrade any aperture. The best results come from hard labor at the eyepiece. I can not state that enough. People can throw the numbers around all they like, but until an observer is actually in the field dealing with this stuff, it's just a numbers game.

It doesn't tell the truth about what really happens. People think I'm a refractor lover and I'm not. I love Newtonians and my experience has taught me that ultimately, the Newtonian with proper tuning is the ultimate setup, but it comes with some work. The reason I'm suggesting the 8" apo is because there are many observers who have no idea how amazing they can be and I mean STUNNING! So much detail it would blow your mind, all in high definition. I've tested several large apos and the image quality is consistently reliable; you can count on it to work if it's a good sample. If people are just going to throw numbers around, then I can assure others they need to spend some time in planetary bootcamp. I'm talking about visual planetary observations, not imaging.

If you can get a large scope working on a good night then boy are you in for a beautiful surprise, but the key is that it's gotta work for you! I love the TEC200 Mak. I have nothing but admiration for Yuri. He does beautiful work overall, particularly his refractors.




Your experience with thermal issues with the large TEC Mak doesn't really apply to the AP Mak. It isn't a matter of the AP being better ventilated, in fact the ota from the primary mirror to the meniscus is sealed and isn't ventilated at all, nor are there mixing fans for the air mass inside the ota. It isn't necessary as long as the main heat sink, the primary mirror, is cooled. The thick meniscus has no problem cooling rapidly since it is exposed to the night sky, in fact the only problem it poses is that it cools too fast, too far, and can be a dew magnet unless one takes steps to slow its cooling.

The AP Mak was designed to be used for planetary observing in the sometimes very stable air at dusk when the temperature is dropping rapidly. After comparing many different permutations of instrumented scopes Roland pinpointed the sources of the thermal problems and addressed them effectively in the 10" Mak. There are many things that went into effective thermal management, I will touch on only the ones Roland discussed publicly on various forums:

-- the focal ratio of the primary was chosen in part to be less sensitive to temperature changes
-- the Corning quartz primary doesn't change much with temp changes
-- the primary is a truncated cone to reduce thermal mass
-- the back of the primary is polished to increase thermal emissivity
-- all surfaces of the primary are ground, no "skin" left to cause the mirror to pretzel when its temp changes
-- the back of the scope comes off to expose the back of the primary
-- fans that blow on the back of the primary to speed cooling
-- the paint used on the ota improves thermal characteristics
-- Roland even addressed the final small heat plume that rises from the baffle tube

The end result is a scope that not only cools rapidly but gives a good image while it is still cooling down. I don't have a 200mm apo, but the 10" Mak cools faster and tracks dropping temps better than my 175mm apo; the 200 would be even slower to acclimate.


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Aquatone
sage


Reged: 03/23/06

Loc: California Bay Area
Re: AP 10" Maksutov vs TEC 200 Fluorite apo new [Re: Paul G]
      #5591127 - 12/27/12 12:38 PM

A comment from the eyepiece that fully concurs with the above. I also rarely have cool-down issues with my 10" AP Mak-Cass. Usually it is ready for observing as soon as it is hoisted onto the mount early in the evening. Any residual thermal variations dissipate quickly even while the outside temperature is falling. (I have also tested with a laser thermometer) I know this seems really hard to believe for those who do not have direct first hand experience with this instrument and who compare it to other Maks or other larger telescopes. Frankly I am not fully sure what is going on either, I suspect it is not any one big design trick, but rather that Roland hit upon a certain combination of thermal management methods that in aggregate just work together at a very high degree of efficiency. Gus's comments about the baffle tube which is not solid but perforated with holes to dissipate the heat plume is a good example of the attention to detail.

Chris


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Daniel Mounsey
Vendor (Woodland Hills)
*****

Reged: 06/12/02

Re: AP 10" Maksutov vs TEC 200 Fluorite apo new [Re: Aquatone]
      #5592061 - 12/28/12 01:14 AM Attachment (39 downloads)

Gus, Chris,

Both of you shared good points and Roland has done a wonderful job with his OTA in order to minimize thermal issues. I agree it does have advantages over the TEC250, however, all instruments of this nature still have to acclimate. Contrary to popular belief, optics which are exposed to their immediate surroundings often face thermal challenges. It's like dropping fish into a fish tank with new water.

In this example here of the Ceravolo HD216 Mak Newt I've been working with, I have also done lots of testing and it's incredibly well designed to cope with thermal internally back to front. But, even it too, requires some time to reach optimal performance, just like the AP Mak my friend had, who is a member here on CN.


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Mike Clemens
Frozen to Eyepiece
*****

Reged: 11/26/05

Loc: Alaska, USA
Re: AP 10" Maksutov vs TEC 200 Fluorite apo new [Re: Daniel Mounsey]
      #5592118 - 12/28/12 03:13 AM Attachment (40 downloads)

We're in danger of the jury being swayed by these Mak pics.

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Mike Clemens
Frozen to Eyepiece
*****

Reged: 11/26/05

Loc: Alaska, USA
Re: AP 10" Maksutov vs TEC 200 Fluorite apo new [Re: Mike Clemens]
      #5592120 - 12/28/12 03:16 AM Attachment (31 downloads)

OK it does have a lens.

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vahe
scholastic sledgehammer


Reged: 08/27/05

Loc: Houston, Texas
Re: AP 10" Maksutov vs TEC 200 Fluorite apo new [Re: Paul G]
      #5592340 - 12/28/12 09:30 AM

Quote:


The AP Mak was designed to be used for planetary observing in the sometimes very stable air at dusk when the temperature is dropping rapidly. After comparing many different permutations of instrumented scopes Roland pinpointed the sources of the thermal problems and addressed them effectively in the 10" Mak. There are many things that went into effective thermal management, I will touch on only the ones Roland discussed publicly on various forums:

-- the focal ratio of the primary was chosen in part to be less sensitive to temperature changes
-- the Corning quartz primary doesn't change much with temp changes
-- the primary is a truncated cone to reduce thermal mass
-- the back of the primary is polished to increase thermal emissivity
-- all surfaces of the primary are ground, no "skin" left to cause the mirror to pretzel when its temp changes
-- the back of the scope comes off to expose the back of the primary
-- fans that blow on the back of the primary to speed cooling
-- the paint used on the ota improves thermal characteristics
-- Roland even addressed the final small heat plume that rises from the baffle tube






All of the points that you make are valid points, they are obvious and are visible, but the real secret of how the overall system is thermally equalized has never been revealed.
There have been many discussion on this on the web, but the bottom line can be summed up with a reply by Roland in response to a question that someone asked, the overall cooling design is a “house secret” and he is not willing to reveal any of that to the competition.

Vahe


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Daniel Mounsey
Vendor (Woodland Hills)
*****

Reged: 06/12/02

Re: AP 10" Maksutov vs TEC 200 Fluorite apo new [Re: Mike Clemens]
      #5593847 - 12/29/12 06:51 AM

Mike,
You did well sir. I know exactly what you're seeing and if it isn't working, it's because the seeing isn't working and you can pretty much count on it.


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Peter Natscher
professor emeritus


Reged: 03/28/06

Loc: Central Coast California
Re: AP 10" Maksutov vs TEC 200 Fluorite apo new [Re: Daniel Mounsey]
      #5594265 - 12/29/12 12:05 PM

I had a HD216 back in 1998 and it too held onto thermals inside the tube due to its primary holding onto heat longer than necessary. Was its primary a Cervit substrate or something similar, but certainly not Pyrex or quartz which would have released its heat faster. During warm summer nights of observing off of a still-warm paved parking lot and set up along side of a AP180EDT and Tak FS150, the refractors were doing a lot better on Jupiter than my HD216 was. I believe the 8" primary mirror was *glued* to a back wall with one fan blowing air against it through a small hole in the sealed wall. There was still too much warm air volume radiating from the primary into the evening to get out of the tube. I replaced the HD214 with a 14.5" f/5.2 Starmaster and never looked back. I was happier with the Starmaster's summer heat habits.

Quote:

Gus, Chris,

Both of you shared good points and Roland has done a wonderful job with his OTA in order to minimize thermal issues. I agree it does have advantages over the TEC250, however, all instruments of this nature still have to acclimate. Contrary to popular belief, optics which are exposed to their immediate surroundings often face thermal challenges. It's like dropping fish into a fish tank with new water.

In this example here of the Ceravolo HD216 Mak Newt I've been working with, I have also done lots of testing and it's incredibly well designed to cope with thermal internally back to front. But, even it too, requires some time to reach optimal performance, just like the AP Mak my friend had, who is a member here on CN.




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Peter Natscher
professor emeritus


Reged: 03/28/06

Loc: Central Coast California
Re: AP 10" Maksutov vs TEC 200 Fluorite apo new [Re: Mike Clemens]
      #5594269 - 12/29/12 12:05 PM

You da man!!

Quote:

We're in danger of the jury being swayed by these Mak pics.




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