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Equipment Discussions >> Cats & Casses

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coopman
Post Laureate
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Reged: 04/23/06

Loc: South Louisiana
Re: "But Maks have a narrow FOV" - WTH??? new [Re: Jon Isaacs]
      #5665247 - 02/06/13 01:18 PM

Many observers today have no firsthand experience of what looking thru an f/15 refractor is like, so Maks DO indeed have a narrow FOV by the standards that they are used to. I've been observing since I was a teenager (45+ years ago now)and I've never looked thru a long focal length refractor.

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hottr6
Carpal Tunnel
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Reged: 06/28/09

Loc: 7,500', Magdalena Mtns, NM
Re: "But Maks have a narrow FOV" - WTH??? new [Re: KerryR]
      #5665279 - 02/06/13 01:35 PM

Quote:

Even for same aperture and same focal length:
Take an 4" f12.72 refractor and an Orion 102mm Mak. Doesn't the refractor inherently permit a wider TFOV because the light cone is (usually) less restricted than the Mak, the Mak having it's necessarily narrow baffle and visual back?




Jon has alluded to this, and I do agree that vignetting will occur in the Mak, but if a Mak and a 'frac have the same focal length, they will still have the same FOV when using the same eyepiece, regardless of the size of the eyepiece's field stop (but the Mak will be vignetted). Is this a correct statement?

I don't have much experience with many Maks, but I have been working under the assumption that the Synta Maks have narrow baffle tubes that will contribute to vignetting. Do Questars, Russian Rumak-Maks and the 7" Meade have "undersized" baffle tubes that contribute to vignetting?


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orion61

*****

Reged: 10/20/07

Loc: Birthplace James T Kirk
Re: "But Maks have a narrow FOV" - WTH??? new [Re: Eddgie]
      #5665310 - 02/06/13 01:49 PM

Quote:

When I say that MCTs have narrow fields, it is relative to other telescopes of the same aperture.

A 5" SCT will generally have a wider true field capability than a 5" MCT.

An 11" SCT can have about the same true field as a 7" MCT.

Relative to other designs, MCTs often do have much narrower true fields.

When made at f/10, they loose the advantage of having a smaller central obstruction than an f/10 SCT. They get the same true field capability, but loose the contrast advantage. And of course they are very expensive.

The truth may hurt, but it is the truth. Compared to similar aperture reflectors, MCTs generally do have a much narrower true field capability.

But this only matters if one needs a bigger field. The contrast advantage tha an f/15 MCT offers over an SCT of the same aperture makes them better (for inch of aperture) planetary scopes.

All scope have compromises. The compromise of the MCT is that unless you take special steps (which makes them very expensive to make) you wind up with a longer focal lenght scope than you get with SCTs or with Reflectors.

Or, you can take those steps and get it f/10, but then you limit the contrast potential to the same as the f/10 SCT.

Pick your poison. Higher contrast but at the expense of being limited



Wouldn't that then call for the comment that a Mak should be far superior than the same size SCT for Planetary viewing useing the same eyepieces?
but we never hear the Positive aspects of Maks..
WE NEED A MAK FORUM..
Heck, we can have one for audio equipment and pets??
this way us true Maksutov fans can have a safe haven for
a Big Mak chat..LOL


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Eddgie
Postmaster
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Reged: 02/01/06

Re: "But Maks have a narrow FOV" - WTH??? new [Re: hottr6]
      #5665335 - 02/06/13 02:00 PM

The baffle tube is not "Undersized." It is the right size for the secondary mirror in the scope.

The contrast of f/15 MCTs can approach that of a refractor because the central obstruction is very small.

The Baffle doesn't need to be any wider (and in fact can be smaller) than the diameter of the secondary baffle, though usually they are made a bit narrower than this.

If you make it fatter, you have to make it shorter so that light leaving the inside edge of the primary can make it to the center of the secondary.

In other words, the size of the baffle is a function of the diameter of the secondary and the spacing between the primary and secondary.

It would not make sense to use a bigger baffle because light could squeek past the secondary mirror and fall directly into the baffle.

This means that the price you pay for having contrast that approaches that of a refractor with the same aperture is that you have to have a small baffle, and this is what limits your true field.

Again, this is why MCTs generally have narrower fields than similar or even much larger SCTs (as my earlier example of the 180MCT vs a C11 clearly shows). To keep the contrast high, you have to use a small secondary, and then you get stuck with a soda straw baffle, which limits the field.

This is what made the MCT popular when refractors were achromats. You could get better contrast from a 7" f/15 MCT than you could get from a 7" f/18 achromat!

But you can get even better contrast peformance out of a C11, and get about the same true field as the MCT and a bigger field than a 7" f/18 achromat.

Again, you can get f/10 out of the MCT, but only with a SCT sized secondary. The only advantage of an f/10 MCT over a similar aperture SCT is that the MCT is better corrected for coma.

The 10" MCT though will be expensive because in the MCT design, you have to take special steps to eliminate higher order spherical abberation, or the scope will not perform well. You can aspherise, or you can use different curves on the front and rear of the meniscus, and on the secondary, but this makes for an expensive scope.

Otherwise, your MCT will usually be limited to about f/12.5 (and even then will have some HSA), and that means that it will usually be limited to a narrower true field than similar aperture refractors, reflectors, or SCTs.

And hence, for a given aperture, the MCTs usually have the narrowest true field capabilites.


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moynihan
Carpal Tunnel


Reged: 07/22/03

Loc: Lake Michigan Watershed
Re: "But Maks have a narrow FOV" - WTH??? new [Re: orion61]
      #5665337 - 02/06/13 02:02 PM

Quote:

WE NEED A MAK FORUM..






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watcher
Carpal Tunnel
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Reged: 11/21/07

Loc: St. Louis, MO
Re: "But Maks have a narrow FOV" - WTH??? new [Re: orion61]
      #5665365 - 02/06/13 02:13 PM

Quote:


Wouldn't that then call for the comment that a Mak should be far superior than the same size SCT for Planetary viewing useing the same eyepieces?
but we never hear the Positive aspects of Maks..
WE NEED A MAK FORUM..
Heck, we can have one for audio equipment and pets??
this way us true Maksutov fans can have a safe haven for
a Big Mak chat..LOL




Sorry,. There is no safe haven. Jon Isaacs will always be there to tell you that newts are better!


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spencerj
Pooh-Bah
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Reged: 11/17/04

Loc: Londonderry, NH
Re: "But Maks have a narrow FOV" - WTH??? new [Re: moynihan]
      #5665437 - 02/06/13 02:49 PM

A lot of this discussion (small baffle, only 1.25" diagonal) is assuming a Gregory MCT. The MCT also comes in the Rumak flavor. I am a fan of the Russian made Rumak Maksutov Cassegrains--MK66, MK67, M603, M703, among others. Those are still Maksutov Cassegrains. I would confidently take any one of them over a similar sized standard SCT for a number of reasons: less field curvature and less variation in optical quality being at the top of the list.

In my Intes MK66-DX, I use a 26mm Nagler T5. That combination gives me almost 1.2* TFOV at about 70x with an exit pupil of about 2mm. The field is flat and sharp to the edge. For me, this is a fine scope for DSO's and the planetary views . . . they are rather OK as well.

I guess I will just have to thank my lucky stars that I can't afford to own an F20 Dall-Kirkham scope. I can't imagine the ridicule those folks put up with . . . "Don't you know you can't see the whole Pleiades cluster in that fancy new scope?"


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Jon Isaacs
Postmaster
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: "But Maks have a narrow FOV" - WTH??? new [Re: watcher]
      #5665492 - 02/06/13 03:20 PM

Quote:

Sorry,. There is no safe haven. Jon Isaacs will always be there to tell you that newts are better!




I won't tell you they are "better" but I will tell you they are different and how they are different.

It's really choosing equipment that is good at what you like to do. If you are a widefield junky, a Mak-Cass is a poor choice. If a compact, portable scope that does a good job on the planets, double stars and smaller DSOs is in the cards, a Mak-Cass is one to seriously consider.

Jon


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Eddgie
Postmaster
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Reged: 02/01/06

Re: "But Maks have a narrow FOV" - WTH??? new [Re: Jon Isaacs]
      #5665613 - 02/06/13 04:32 PM

Yes, I don't get it..

Why do people get so defensive about this or that design.

All telescopes have some kind of compromise.

Sure a 6" APO can be as perfect as a 6" Aperture can be, but it costs a lot and it is pretty easy to match the performance 100" by using an 8" reflector and a Paracorr, and it will cost 4 to 5 times as much for the 6" APO.

The MCTs that someone else mentioned do indeed have better coma correction than a standard SCT, and have consistently excellent optical quality, but they cost two to three times what a similar sized SCT costs.

Reflectors get very akward to use as they get larger, and pressure the eyepiece performance and the viewers threshold of coma tolerance as they get fast enough to keep one off of a ladder.

Absolutely everything in optics is compromised in some way or other.

No scope is perfect for everyone because everyones needs are different, and most people simply don't have the money to buy 14" APOs or 14" Rumaks.

People like you and me just relate the news. We don't make the news.

I don't really have any interest in what anyone owns, but if they ask a question about "Why is this?" I try to answer.

If it makes me sound biased, I take that as someone just not liking the news.

Having owned refractors, reflectors, and compound scopes in all different shapes and sizes, I like them all, but they all have their compromises.

Why can't people just accept that and move on?


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Cepheus Elf
member


Reged: 08/01/10

Loc: Rainy, Cloudy Lancashire UK
Re: "But Maks have a narrow FOV" - WTH??? new [Re: hottr6]
      #5665626 - 02/06/13 04:38 PM

Quote:

I am always reading the most abused and over-used byline in astronomy.... Maks have a narrow FOV. I'll suggest that such statements are made be people who came down in the last rainstorm.

Anyone ever heard slow 'fracs have a narrow field of view repeated multiple times in the same thread? No? Try saying that in the Refractor forum and be prepared to be stoned with chipped flint glass.

Anyone whoever grew up with 'scopes before the optics revolution in the late 80s grew up with long 'fracs and Kellners (if they were lucky). Magnifications greater than 70x would clip the Moon.

Today, any noob can plop a 70 degree AFOV eyepiece in their long-focus 'scope and enjoy WIIIIDE views.

I'm plenty happy with today's WIIIIDE views offered by long-focus Maks and 'fracs.







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Mary
sage


Reged: 01/29/08

Loc: Highlands Ranch, CO
Re: "But Maks have a narrow FOV" - WTH??? new [Re: Jon Isaacs]
      #5665652 - 02/06/13 04:56 PM

Quote:



If a compact, portable scope that does a good job on the planets, double stars and smaller DSOs is in the cards, a Mak-Cass is one to seriously consider.





Absolutely right. My little 127 really won me over.

Mary


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Mary
sage


Reged: 01/29/08

Loc: Highlands Ranch, CO
Re: "But Maks have a narrow FOV" - WTH??? new [Re: Eddgie]
      #5665654 - 02/06/13 04:58 PM

Quote:



All telescopes have some kind of compromise.






And this is correct as well!

Mary


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Mark Costello
Post Laureate
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Reged: 03/08/05

Loc: Matthews, NC, USA
Re: "But Maks have a narrow FOV" - WTH??? new [Re: Mary]
      #5665701 - 02/06/13 05:25 PM

Quote:

Quote:



All telescopes have some kind of compromise.






And this is correct as well!

Mary





... and I consider it to be my task as an amateur astronomer and potential telescope purchaser to understand the compromises and pick out which features on which I want versus on which I'm willing to compromise.

On my first acquisition in coming back into this hobby in 2003-2004, I wanted ruggedness, portability, ease of setup and teardown, ergonomics of use, relative low cost, and my intrinsic - or insane idea as to what was a telescope, but was willing to compromise a bit on image quality in favor of price, so I settled on a not too large achromatic refractor (first 4" and now 5").

In looking at a possible second and larger telescope, I know I still want some portability and ease of setup and teardown although am willing to compromise some on this (15 minutes versus 5 minutes for my current rig). That mainly limits the scope to some kind of reflector and its size to maybe 10" give or take a bit.

If I want to put a premium on image quality and maybe cost and compromise on everything else, it'll probably be a Newtonian reflector. If it's this, it'll definitely be a dob. And I'll see if I can find a longer focal length Newtonian (about 60" give or take a little).

If I want to insist mainly on ergonomics of use and hold down the cost a little, and a longer focal length (so as not to "compete" with my refractor), it's likely to be the Schmidt Cassegrain telescope (SCT).

If I want to insist somewhat on a combination of high image quality and portability (a bit of compromising in this) and am willing to settle for an even longer focal length and the extra cap on aperture due to availability, it may be a 7"F15 type Maksutov Cassegrain telescope (MCT).


That's a lot of things to consider. Good thing that between my achro's performance and my wallet's, I have a lot of time.

Edited by Mark Costello (02/07/13 01:50 PM)


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GeneT
Ely Kid
*****

Reged: 11/07/08

Loc: South Texas
Re: "But Maks have a narrow FOV" - WTH??? new [Re: spencerj]
      #5665804 - 02/06/13 06:29 PM

Quote:

Any post with the term Maksutov Cassegrain generates a barrage of posts with the term narrow field of view.




I wonder how many of these people had ever done serious viewing with a Mak or SCT. I viewed with a C8 for about 10 years. I never commented or complained about the narrow FOVs. I did comment that I found slower optical systems to be more forgiving of more inexpensive eyepieces. All I could afford in those days were Celestron eyepieces. I was very pleased with the views provided by both the telescope and my eyepieces.


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Scott BeithAdministrator
SRF
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Reged: 11/26/03

Loc: Frederick, MD
Re: "But Maks have a narrow FOV" - WTH??? new [Re: GeneT]
      #5665859 - 02/06/13 07:09 PM

I used to own a very nice Orion Starmax 127 and I called it an "apo in a can"

Great little scope that never needed collimation and in 2003 it provided stunning views of Mars.

From my perspective it did have a narrow FOV but on my intended targets (planets and the Moon) it didn't matter a bit. The fact that my next scope purchase was a SV 80mm f/6 refractor may have an impact on my perception of the Mak's FOV.

I use middle focal ratio (f/7 - f/7.8) refractors now but I still have fond memories of the 5" Mak.


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Mark Costello
Post Laureate
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Reged: 03/08/05

Loc: Matthews, NC, USA
Re: "But Maks have a narrow FOV" - WTH??? new [Re: Scott Beith]
      #5665942 - 02/06/13 08:04 PM

Quote:

I used to own a very nice Orion Starmax 127 and I called it an "apo in a can"

Great little scope that never needed collimation and in 2003 it provided stunning views of Mars.

From my perspective it did have a narrow FOV but on my intended targets (planets and the Moon) it didn't matter a bit. The fact that my next scope purchase was a SV 80mm f/6 refractor may have an impact on my perception of the Mak's FOV.

I use middle focal ratio (f/7 - f/7.8) refractors now but I still have fond memories of the 5" Mak.






Scott, if all you had were that SV80mmF6 refractor (was it the old Night Hawk) and the 127mm MCT, I'd say you had two nicely complementary telescopes. I may do that on a larger scale, my 5" achro and maybe a 7"F15 Mak. I'm not sure....

Edited by Mark Costello (02/07/13 01:50 PM)


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Eric63
scholastic sledgehammer


Reged: 06/16/12

Loc: Ottawa, Ontario
Re: "But Maks have a narrow FOV" - WTH??? new [Re: Mark Costello]
      #5665961 - 02/06/13 08:21 PM

Mark, I'm also using complementary scopes as you described. I have a 127mm Mak that I was using with an 102mmF5 Achro, but I have now acquired my son's 150mm F5 Newt. So I think the Achro may go soon. Anyway, I now have the Mak for med to high power and the Newt for wide field and DSO's. They are both very portable, with quick set up and take down, and complement each other nicely. And they both ride nicely on the AZ4

BTW, I use a 2inch 32mm 70 degree EP in my Mak and I find the field of view more than acceptable. In fact the Mak is the scope I use the most right now.

Eric


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orion61

*****

Reged: 10/20/07

Loc: Birthplace James T Kirk
Re: "But Maks have a narrow FOV" - WTH??? new [Re: Eric63]
      #5665982 - 02/06/13 08:43 PM

I have a Meade 7" F15 Mak, my second. It is better than the first optically, I love the field of view but I am not into wide field scanning, I put a 6.3 FF/FR on my C8 for that.
The 7" is my favorite scope, I love it, There are so many details on Jupiter my Brain goes into shock! So much to take in, A Bino viewer adds to that,
I have a 127 SLT that is my Grab & Go, that replaced my ETX 90, The ETX is now my Travel scope, and Solar scope.
Along with a 12" SCT and 4" APO and 6" F8 RV6 I have most bases covered. except the 16" Dob.... Don't you love to hear a grown man whine?
Lets all PM the Admin for a Mak Forum?? HAPPY PM's


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Eric63
scholastic sledgehammer


Reged: 06/16/12

Loc: Ottawa, Ontario
Re: "But Maks have a narrow FOV" - WTH??? new [Re: orion61]
      #5665995 - 02/06/13 08:56 PM

Orion61

I am also sold on Maks and I am considering upgrading to the 6" in the future. I think 7" would be too much since I would like to stay with the AZ4 mount. But that is down the road since the 127mm is providing me with an amazing view right now. As you said in another thread, it's a classic in the making BTW, last year I read many of your comments on the 127 Mak and your views help me a great deal in choosing this telescope.

Eric


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*skyguy*
Carpal Tunnel
*****

Reged: 12/31/08

Loc: Western New York
Re: "But Maks have a narrow FOV" - WTH??? [Re: Eric63]
      #5666064 - 02/06/13 09:33 PM

So what if a Mak has a slightly narrower view than a general purpose scope like a SCT. Its optical design provides a comparable view with an APO refractor (or a f/15 achromat) in a lighter, more compact and more portable OTA ... and at a far lower cost. My long focal length 5" f/15 Mak will reach 257X using only a 7.4mm eyepiece and shows absolutely stunning views of the planets and the moon ... no need to use a barlow that will only "muddle" up the view. Try that with a f/10 SCT or a fast APO refractor.

When I want to go wide-view, I pull out my grab-n-go 5" f/3.64 SNT Comet Catcher that has the finest wide field views I've ever experienced using any telescope.

No one telescope will provide the perfect view for all types of observing ... from low power wide field to high power planetary viewing. I'd rather have ... which I do ... the perfect low power scope and the perfect high power scope ... than a single "middle-of-the-road" general purpose scope, that from necessity has to be a compromise between the two types of "specialty" scopes.

I have been and always will be a big fan of the Maksutov .... however, I'm also a big fan of the SCT, refractor and newtonian scopes. It all depends on the type of viewing I want to do ... and how much money I have to spend!


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