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#26 astroneil

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Posted 18 July 2014 - 03:42 PM

Ed,

I feel the same way. Never let equipment get in the way of having a good time. It was never meant to be anything otherwise.

Would love to hear of your adventures comparing the 4" achromat with your 5" Maksutov in due course.

Best,

Neil. ;)
 

#27 astroneil

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Posted 18 July 2014 - 03:47 PM

Hey Ed, I'm also waiting for that comparison :grin:

But if you want to know, I put my 127Mak up against my 1/10th wave 6"F5 Newt during some very good seeing last week and the difference was so slight you really had to look for it. The Newt was a bit brighter of course and had a bit more resolution, but you really had to look hard. They both showed colour very well and the detail was pretty much the same. But I find that the Mak needs good seeing to perform well and falls a bit behind the Newt when the seeing is average (this was first pointed out to me by a fellow CN'er and I also noticed it). The Newt also has better thermal control. But the little Mak is an amazing performer and definitely a keeper. Amazing optics in these little packages.

Eric


Hi Eric,

Interesting results!

Maks are super cool!

Best wishes,

Neil. ;)
 

#28 Eric63

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Posted 18 July 2014 - 05:07 PM

Hi Neil

I could not agree more, Maks do rock. After I had my Newt refigured I thought about selling my Mak because both scopes gave similar high power views. But then I used it and fell in love all over again. :grin: Something so compact that performs so well cannot be disposed of. :D

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#29 astroneil

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Posted 18 July 2014 - 06:14 PM

I have a TEC Maksutov of 8-inch aperture, f/15.5 which cost me $4000. RMS 1/45 wave, PTV 1/9 wave, Strehl 0.99. To equal it with an APO I would have to get a TEC 180 or an AP 175. The latter two scopes go for 3x to 5x as much money! To get a noticeable improvement I would have to go to a 200mm Apo which gets into $30 000 territory......

The TEC 202 is, perhaps, the perfect scope for everything visual except wide field viewing. It is not fast enough for reasonable use as a Deep Sky photography instrument. (I wonder if I can get a focal reducer that will bring it to better than f/10.....) It can do wonderful high res lucky imaging of lunar, planetary and double stars.

As for the major 'knocks' against the Maksutov design: 1. the central obstruction is 25% which has only a very small effect on the diffraction pattern. I really don't see it as a problem. 2. the 'cool down' problem is NOT a problem if I can get the scope out about 1 hour before sunset. The scope performs beautifully from late dusk and seems to 'keep up' with a night of rapid cooling. I would add that nights of rapid cooling almost invariably have bad to terrible seeing which overpowers any cooling problems anyway...

I will add that the TEC has the best focuser in the world. Yes, the best. Despite being the 'moving main mirror' type it has absolutely zero image shift. It holds position perfectly and, with its micrometer dial, can actually be pre-set accurately by reading the dial.

Dave


Thanks Dave; a very important post from someone in the know. ;)

Best wishes,

Neil. ;)
 

#30 astroneil

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Posted 18 July 2014 - 06:21 PM


I am not surprised that the OP took a liking to a 7" Mak over his 5" achro. Not really a fair comparison. If we set aside logistics of long/heavy tubes, cool-down times, viewing conveniences and cost, I find that inch-for-inch the humble colorful 6" achro with a CA ratio of around 1.5 offers better views at any magnification than any of the obstructed designs. Conrady 'fracs are even better. And this is coming from a Newt-guy even after I discovered the Paracorr.


Ken that.

Thanks Shane.

Regards,

Neil. ;)
 

#31 BKBrown

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Posted 18 July 2014 - 07:10 PM

...The people lust over large refractors but soon discover they are made from unobtanium. They are simply beyond the means of the vast majority. The large colour free refractors are ridiculously expensive for what they deliver and require if not equally expensive mounts.

Designing a nice folded refractor with the same attention to detail as a cassegrain would be a game changer; the people would soon forget about how they look and delight in the beautiful images they could serve up. These could be offered at a much lower price than the current options.

In my opinion, the 'apochromat revolution' never happened unlike the Dobsonian revolution.

Bring the people a large, nicely made folded refractor and a true revolution can begin.

Regards,

Neil. ;)




Hi Neil,

Vis-a-vis the strictest interpretation of the term "apochromat" as generally applied I agree...the revolution did not put an inexpensive AP or Tak in every amateur's hands. If however, you use the term in the manner to which it is increasingly being applied, a well corrected multi element refractor that shows essentially no color in focus, it is fair to say the revo has run its course and amateur astronomers are the winners.
There are numerous comparatively inexpensive doublets available today that offer colorless/nearly colorless views...and those views can be quite good indeed. Twenty years ago who would have thought that scopes like the ubiquitous Synta 100ED f/9 would routinely be available for well under $1,000 new and oft times half that used? How about the moderately priced 127mm triplets from Explore Scientific for less than $2,000 and offered with a range of very nice features and extras? And at the higher end, the new Lunt 152mm ED OTA is amazing at under $4,000 new; significantly less than what similarly priced triplet instruments currently command! And in modern dollars these instruments are absurdly inexpensive compared to their predecessors from not-so-long-ago.
Newer materials and optical craft have made instruments like these available that were undreamed of when I was a teenager exploring the universe with my bargain basement 60mm Sears refractor...and I for one am glad. I believe that we are blessed with a wealth of choices here at the front end of the 21st century. And while a folded long focus achro would no doubt provide terrific views (I'd love to see for myself :watching:) and a different kind of viewing experience, could they realistically hope to compete in the market place with the current tsunami of enticingly priced and excellent quality "new Apo" doublets and inexpensive triplets? Just some food for thought...

Clear Skies,
Brian
 

#32 astroneil

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Posted 18 July 2014 - 07:30 PM

Hi Brian.

Intellego.

But my Maksutov would beat arguably all of the above on planets, doubles, smaller DSOs etc etc etc.

Regards,

Neil. ;)
 

#33 BKBrown

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Posted 18 July 2014 - 07:46 PM

It certainly better Neil at 180mm and f/15 or somebody owes you some money! :lol:

Clear Skies,
Brian
 

#34 astroneil

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Posted 18 July 2014 - 07:53 PM

Hi Brian,

Nescio.

Best,

Neil. ;)
 

#35 Ed Holland

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Posted 18 July 2014 - 09:44 PM

A fun halfway-house for the refractor would be to make some ED doublets of longer focal length. In fact I wonder why manufacturers have not sought to expand their range this way with "planetary" and "widefield" versions at each aperture.

But this is Cats and Casses. We know that the useablility of compound designs, and their quality are frequently well up to the job, and ones observing list is only limited by time and enthusiasm.

Only problem I have now is that this thread leaves me wanting a 180mm Mak ;).
 

#36 BillP

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Posted 18 July 2014 - 09:45 PM

Twenty years ago who would have thought that scopes like the ubiquitous Synta 100ED f/9 would routinely be available for well under $1,000 new and oft times half that used? How about the moderately priced 127mm triplets from Explore Scientific for less than $2,000 and offered with a range of very nice features and extras? And at the higher end, the new Lunt 152mm ED OTA is amazing at under $4,000 new; significantly less than what similarly priced triplet instruments currently command! And in modern dollars these instruments are absurdly inexpensive compared to their predecessors from not-so-long-ago.


:ubetcha:

Each design has its charm to it. They are all quite different in how they behave and how they present and how they handle. In the end, no one is better than the other, just different. And it is up to each of us to decide to which we are attracted to most. In the end, the match between man and machine is more about heart, which has nothing to do with trivial things like aperture, cost, or logic. We like what we like, that says it all.
 

#37 Asbytec

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Posted 19 July 2014 - 01:35 AM

Neil, after owning a MCT, I am also "...a keen student of the design." I tried to understand why that would be. Got some ideas, but still unsure why I love the design so much. It could just be the fact I own one in mild tropical climate and seeing. Most other scopes I've owned have been in lesser seeing and temperate climates.

When I was putting this cheap scope through it's paces, I became increasingly amazed at how good it appeared to be. Even four years later, I am still very pleased. I stumbled into that "dream environment" mentioned above, and have actually, no kidding, glanced skyward and thanked God for such wonderful skies and a scope that fits the bill.

Whatever the cause, MCT design, climate, or both, I'm keeping mine even realizing there are larger apertures and more purist views to be had. I don't mind at all if my Jaw get's dirty hitting the lawn - cut grass tangled in my 3 day old beard or the neighbor's dog gnawing on it.
 

#38 astroneil

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Posted 19 July 2014 - 06:25 AM

Hello Norme,

Thank you for chiming in. I have followed your work, watching to see if you would change. But you have not. :bow: :bow: :bow:

I have discovered that refractors are vainglorious telescopes that defy logic and bring out the worst in people.

Then sweet Cornelia came along. :flower:

I would like to keep her, my cheap Cornelia.

Best wishes,

Neil. ;)

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#39 Asbytec

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Posted 19 July 2014 - 06:50 AM

She's beautiful, Neil. :drool5:

:)
 

#40 astroneil

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Posted 19 July 2014 - 06:56 AM


I go on holiday now, with my wife and sons.

Thank you all.

Neil. ;)
 

#41 astroneil

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Posted 27 July 2014 - 07:10 PM

We arrived back late today from a fabulous week away. Bonnie Caledonia basked in sunshine all the while.

I had no telescope to use during the trip but I enjoyed watching the last of the noctilucent clouds disappear into the northern sky. Perseus and Pegasus loom large in the east.

After we had all settled in again, I ventured into the garden in the cool of the late evening and set Cornelia on the SkyTee Altaz. I arrived back an hour later, after midnight, when the sky was all but dark again after weeks of twilight.
The stars were calm and the telescope delivered beautiful bright images of some of the toughest double stars I use to test telescopes at this time of year. Some of the treasures of the deep sky were a sight for sore eyes.

I'm tired now and need to turn in. But I'll report back later.

Mirabilia caeli!

Thanks,

Neil. ;)
 

#42 astroneil

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Posted 28 July 2014 - 10:11 AM

When it comes to testing telescopes, the heart is deceitful and so one must never assume anything. One must put everything to the test!
Last night, the 180mm Maksutov underwent a temperature drop of ~8C over a few hours with no repercussions that I could discern.
I coupled the instrument with my Baader Mark III clickstop zoom, which I am enjoying. It provides a convenient way of attaining continuously variable magnification ranges from 113x to 340x without having to change oculars in the field. And with the dedicated Barlow, I can attain further amplifications of 2.25x over the above range.

Delta Cygni is magnificent in this telescope. At 340x the steely blue companion presents as a painfully beautiful Airy disk wide away from its bright companion.
I turned the telescope on Lambda Cygni, the Aa-B components of which are a mere 0.9 seconds of arc apart and have a brightness differential of 1.8 magnitudes (4.5/6.3). At 340x, the large Maksutov easily revealed both components, which were satisfyingly calm to my average eye.

An even tougher test yet came when I turned Cornelia on Zeta Heculis, now well past the meridian. The A-B pair has an even greater magnitude difference (2.8/5.5) and the components are separated by 1.1 seconds of arc. Well, at 340x, the telescope made light work of this system. A perfectly formed, lime green Airy globe cleanly seen due south of the yellow white primary.

I can say with confidence that there is no 6 inch refractor on Earth that can split this system with the efficacy of this high performance Maksutov. You are welcome, indeed encouraged, to test this assertion for yourselves.

I swung the telescope a few degrees above Zeta to the great globular cluster In Hercules, M13. The view was magnificent at 113x. I suppose if I had used a dedicated 24mm ocular of high quality I could have squeezed that little bit more form the image but it mattered little. My eye witnessed a great mound of stars, too many to count. Relaxing in my chair I enjoyed the almost translucent (lifelike?) quality of the image as it moved across the field of view at 113x. Hints of the propeller like appendages could be made out from moment to moment. My 5 inch glass cannot deliver what this compact telescope clearly can.

Finally, I moved the ‘scope over to M57, the famous Ring Nebula in Lyra. Again, I was lost for words to see it so distinctly against a coal black sky. The small field of view even at 113x makes it look so much more imposing than in a wide angle eyepiece.

A telescope like this would have astounded an observer in my father’s time and we would have needed the wealth of a Sultan to acquire one of this quality. To think that one can get this kind of performance out of a telescope only half a metre long and weighing a mere 20 pounds is a joyous revelation. This is a magnificent telescope!

Man and his technology!



Neil. ;)
 

#43 astroneil

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Posted 28 July 2014 - 11:18 AM

Big Mak & Fry's :)

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#44 Ed Holland

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Posted 28 July 2014 - 02:44 PM

Ooooooh. Fry's Chocolate Cream :)

Perfect accompaniment to an evening's stargazing.

Thanks for the reports - you surely have a nice example of that telescope. My own 5" Orion Mak star tests beautifully, and is a treat on double stars. Two more inches of aperture can only get better.

Cheers,

Ed
 

#45 astroneil

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Posted 28 July 2014 - 03:20 PM

Ooooooh. Fry's Chocolate Cream :)

Perfect accompaniment to an evening's stargazing.

Thanks for the reports - you surely have a nice example of that telescope. My own 5" Orion Mak star tests beautifully, and is a treat on double stars. Two more inches of aperture can only get better.

Cheers,

Ed


Hey Ed,

My pleasure.

I would gladly share my Fry's Chocolate Cream with you. :bow: :bow: :bow:

Plenty to go around. :)

Regards,

Neil. ;)
 

#46 elwaine

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Posted 28 July 2014 - 03:58 PM

...our individual choices make us content.


Neil, that is the best summary statement I've read on the subject!

Over the past 30 years or so I have owned (at various times) Maks from 90mm to 203mm; apo-refractors from 70mm to 130mm; SCTs from 203mm to 280mm; a 318mm RC, and binoculars from 70mm to 100 mm. They have all taken me places I could not otherwise go to in mind or imagination.

Choosing only one "culture" would be like asking me to choose just one of my three children - or asking me to choose between my favorite foods: hot dogs, donuts, and pizza. :grin: :grin: :grin: Some choices are just impossible to make. And in the end, it comes down to what you said initially: our individual choices make us content.
 

#47 Asbytec

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Posted 28 July 2014 - 06:33 PM

The heart is deceitful, and our scopes become affairs of the heart when we give them a woman's name. :)

I have put my Mak to the test and "she" has performed, when she's cooled, collimated as perfectly as I can get her, and operating in very good tropical seeing.

Some of the more difficult tests "she" has passed include the "apparent" elongation of Io (a diffraction effect), surface albedo on Ganymede, resolving a tiny crater in crater form subtending just 0.7" arc, elongating Chi Aql at a bit less than half the Raleigh limit.

Those are all high res targets, but that's where I get my kicks after discovering lunar and planetary observing with her. After decades of deep sky observing, it's a real treat to explore undiscovered realm including double stars. "She" may not have every advantage on wide field and doubles as a refractor of equal aperture, but she is no slouch on either and on deep sky. Besides she can out resolve the same 6" refractor.

I love this scope because she does what I want her to do and don't have to hide her in the closet if she bores me. You can have as many scopes, of whatever design, as you desire and cherish each of them. You can enjoy other cultures, nothing wrong with that. For me, finding one keeper that does what I want it to do has kept aperture fever at bay, there is less desire for accessories, and no I longer feel the need to divorce her and find a new scope to try. She fulfills every desire.

I offer nothing but praise for the MCT design, understanding her performance has very much to do with the care taken to collimate and cool her and the excellent tropical seeing. With such care and conditions, you can really see what a scope can do. And she is impressive.

She just needs a name.
 

#48 Starman27

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Posted 29 July 2014 - 01:00 AM

Thanks for the report. Looks like your heart is in the right place.
 

#49 Asbytec

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Posted 29 July 2014 - 02:32 AM

:)

Yea, this scope just drove itself home, spent the night, and stayed. Surely others feel the same about their "culture." That's understandable. And when you have a scope you love, this hobby rocks.
 

#50 astroneil

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Posted 31 July 2014 - 03:28 PM

Hello Larry,

Thanks for your comments and I readily concur.

Norme, you are clearly far more skilled than I am with your beloved Maksutov. I have much to learn but I'm very excited about putting Cornelia through her paces on a wider variety of celestial targets now that the darkness has returned.

My achromatic culture is old and distinguished. Its achievements in the hands of skilled observers are rich beyond measure, indeed unparalleled in some respects to anything achieved in modern times. Its voluminous literature inspires and warms the heart. It needs no justification for its continued existence, for it has taken on the mantle of an art form and art is timeless. So long as humans survive, the classical refractor will survive.

I am the proud owner of a most elegant 5” f/12 achromatic aka ‘Tiberius’. He’s long and heavy, built like a tank, but when I sit and imbibe in his unique images, he reels the spirit like no other instrument I've had before. Yet, the arrival of Cornelia, the large Maksutov Cassegrain, has opened my eyes to the impracticality of larger refractors. The cost to make and mount them quickly spirals out of control, so much so that they can’t be justified on practical or economic grounds. Professional astronomers have long known this, yet we are being asked by refractor buffs- the ‘pretty boys’ - to lavish exorbitant sums of money in the pursuit of what is, at its heart, a nonsense.

A historical account from my own culture provides an instructive moral in this matter. Ole Percival Lowell was a big fan of stopping down the aperture of his large Clark refractor, finding that on many nights on Mars Hill, the image improved significantly when the great 24-inch glass was stopped down to 18 or even 12 inches! I can understand Lowell’s motivations for doing so. Stopping down does indeed make the images better in large classical refractors, simply by increasing the relative aperture and utilising what often proves to be the best part of the object glass. Lowell was a skilled practitioner of ‘prettifying’ his Mars images in the mistaken belief that it would yield finer details. Yet the maths graduate from Harvard was quite wrong in his beliefs. Subsequent work by E.M. Antoniadi using the 32.75 inch refractor at Meudon, France, as well as the observations of E.E. Barnard, employing the full aperture of the Great 36 inch Lick refractor in the United States, failed to see any canals. Instead, they suggested (correctly) that the ruler straight lines seen by Lowell and others disappeared into a plethora of mottled spots when the greater resolving powers of the world’s largest refractors were pressed into action.

I have no doubt that Lowell saw more beautiful images of Mars with his stopped down Clark than either Antoniadi or Barnard did with their larger telescopes. But pretty ain’t everything. You see, when reality is soberly sought, aperture trumps beauty!
The views through the ergonomic and ultra-portable Cornelia would undoubtedly reveal more of the Universe than my luxurious Tiberius can possibly offer. She’s not a refractor but so what? It makes far more sense than securing and using a larger glass. I am grateful to her for bringing me to my senses and I'm sure that St. Barnard fae Tennessee would have approved of my reasoning. My 5” refractor will remain in my stable but I will not countenance a larger one.

I need to go now. But I promise to write a full CN review of my ongoing experiences with Cornelia, my refreshing new compound telescope.

Thank you all.

Best wishes,

Neil. ;)
 






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