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"But Maks have a narrow FOV" - WTH???

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#101 orion61

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Posted 11 February 2013 - 05:05 PM

For photography the FL of a Mak is not nearly the issue than it used to be. I remember guiding until my head felt like it was going to fall off.
Now we can do it in a small fraction of the time.
Both SCT'S AND MAKS HAVE ADVANTAGES over the other.
I am mainly a Lunar/Planetary/Double Star viewer.
for photography the SCT gets the nod.
You guys remember photography through a Newtonian?
6-10 mph winds had my Cave bouncing all over.

#102 Asbytec

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Posted 11 February 2013 - 06:59 PM

LOL, Ed. A few of us know that 'wink.' My 'eye' is wide open and performing beautifully, NFOV and all.

#103 BigC

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Posted 12 February 2013 - 11:35 AM

Does a 7" f"X" Mak have a narrower FOV than a 7" f"X" refractor ?

Comparing scopes of the same focal length would seem to be more "fair";and really they should have the same clear aperture in order to compare two optical systems that begin with the same amount of light.So maybe I would discover that my 5" f13?(just a guess,it is a Bushnell)Mak would equal a 4" f13 APO.

And the Mak is easier to mount and store.

It SEEMS obvious to me one needs at least two scopes:one widefield and one long focus!

A universal tool is one that does all jobs equally poorly.

#104 KerryR

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Posted 12 February 2013 - 12:48 PM

Does a 7" f"X" Mak have a narrower FOV than a 7" f"X" refractor ?

Comparing scopes of the same focal length would seem to be more "fair";and really they should have the same clear aperture in order to compare two optical systems that begin with the same amount of light.So maybe I would discover that my 5" f13?(just a guess,it is a Bushnell)Mak would equal a 4" f13 APO.

And the Mak is easier to mount and store.

It SEEMS obvious to me one needs at least two scopes:one widefield and one long focus!

A universal tool is one that does all jobs equally poorly.


Depends on the baffles, focuser diameter, and diagonal diameter, I think, in the refractor, all of which affect TFOV. In most cases, I believe the refrator will have a wider available light cone, and so should be capable of a wider field, even at the same focal length.

Then there's also the issue that the refractor can be used at larger exit pupils, exceeding 7mm, without a secondary shadow dimming the center of the FOV (effective aperture reduced in both cases)

As you point out, the big advantage to the Mak is not it's performance characteristics relative to the refractor, but it's cost, weight, shortness, ease of mounting, and, arguably, it's fairly refractor-like performance, which sums up the whole reason the design ever came about in the first place. Same arguments would apply to an SCT.

But really, how many f12-15 refractors, not to mention Newts, do we see anyway?

#105 Asbytec

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Posted 12 February 2013 - 02:52 PM

Id need to look up the specifics, but the CAT design - not only the Mak - will vignette the field. However, there is also the usable field to consider. If a CAT vignettes some of the usable field, that may rub wide field folks the wrong way. I cant pull figures from memory, but I believe spot Maks have smaller usable fields than Rumaks. Those in turn differ from refractor and other CAT designs, including classical Cassegrains, etc. All designs have some level of usable fields and vignetting.

#106 Ed Holland

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Posted 12 February 2013 - 03:08 PM

There are some odd artifacts, IIRC with all Cassegrain variants. These can lead to edge vignetting due to the presence of a baffle, and (I think) central FOV dimming at very low magnifications due to the CO.

Someone may want to comment on the validity of my second comment.

Ed

P.S. I like my f/10 and longer scopes, but I'll consider a wide field instrument if you can get me nearer to Jupiter or Saturn ;)

#107 Asbytec

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Posted 12 February 2013 - 03:11 PM

Yea, Ed, same here.

#108 Jon Isaacs

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Posted 12 February 2013 - 03:50 PM

Comparing scopes of the same focal length would seem to be more "fair";and really they should have the same clear aperture in order to compare two optical systems that begin with the same amount of light.So maybe I would discover that my 5" f13?(just a guess,it is a Bushnell)Mak would equal a 4" f13 APO.



Such comparisons are not about being fair, rather they are about being realistic. 4 inch F/5 refractors with 2 inch focusers exist. 5 inch F/5 Mak-Cass' don't. On the other hand, 5 inch Maks that are 15 inches long exist and 5 inch Newtonians that are 15 inches long don't.

It's not about being "fair", it about what is and what is possible.

Jon

#109 maknewtnut

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Posted 12 February 2013 - 11:30 PM

After reading more input to this thread over the past few days, I have to say something to Jon. I believe the thread was about folks in this forum comparing MakCass telescopes to SchmidtCass telescopes (or other Cassegrain variants). In reading many of your replies, I get the impression your take was MakCass compared to Newt.

To expand on a few points that were made, one has to first consider the strengths and weaknesses of any telescope design type when making comparisons. When it comes to the 80mm refractor v 90mm f/14 MCT comparo, of course the refractor will be the better choice for most...because it is at smaller apertures that the refractor provides the most pros vs cons. At apertures of ~10" and larger, the Newtonian reflector provides the most pros vs cons compared to other designs. It is at mid-apertures where the MCT (and other Cassegrain variants for that matter) provide more pros than cons.

To lump all MCT's into the f/12 and slower 'basket' supports the OP's point more than it supports supposed arguments against it.

(and FWIW, to list only Chinese f/12-f/15 MCT and Questars as the only available options is just plain wrong...or once again, claiming what one 'knows' is what they read from the latest Orion catalog...those were shipped across an ocean to the N America for those who might be under the impression that ordering from a vendor on another continent won't lead to the same method of arrival)

#110 Eric63

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Posted 13 February 2013 - 08:50 AM

My two cents here. I saw the OP’s post as a jab with a touch of sarcasm at those who complain about the narrow FOV of Maks but then go and recommend F10 SCT or F10 to F15 refractor. I have only been in the hobby less than a year but it did not take me long to figure out the difference between scopes, and which ones I like best. In the end the view is not the only thing that counts. Ergonomics, economics and storage are other factors that to me are very important. I got a 127Mak because I did not want to spend a fortune on an apochromat, nor did I want a long tube or a large cumbersome tube. My Mak is very portable, stores easily, I have no vibration issues at all and I can sit comfortably behind it in an area where I have limited space. Oh yes, and the views are fabulous. For my viewing habits, smaller instruments are best and coming onto my 1 year anniversary in the hobby I have found that the combination of a 6 inch F5 newt and a 5 inch Mak best suit my needs. So yes, I knew about the Narrow FOV and I welcomed it since My Mak is my solar system scope for around the house and my Newt is my wide field and DSO scope when I travel to a darker site. And I have to add, that when I do use the Mak for brighter DSO’s, I love the views. Yes they are not wide field, but when I have to come in closer the contrast and sharpness is much appreciated.

Eric

#111 KerryR

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Posted 13 February 2013 - 09:59 AM

...
To lump all MCT's into the f/12 and slower 'basket' supports the OP's point more than it supports supposed arguments against it.
...


There are commercially produced MCT's that are faster than f12? Who and how fast? Obviously, some MCT's can accept a focal reducer, but I don't think that's what you're talking about.

#112 Jon Isaacs

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Posted 13 February 2013 - 10:42 AM

After reading more input to this thread over the past few days, I have to say something to Jon. I believe the thread was about folks in this forum comparing MakCass telescopes to SchmidtCass telescopes (or other Cassegrain variants). In reading many of your replies, I get the impression your take was MakCass compared to Newt.



That might have been the case but I just went back and read the original post and the no mention SCT or other Cassegrain varient. This is what I did find however:

"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."

In any event, the field of view knock referred to is generally in comparison to Newtonians and fast refractors...

Jon

#113 RichD

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Posted 13 February 2013 - 10:49 AM

[/quote]

There are commercially produced MCT's that are faster than f12? Who and how fast? Obviously, some MCT's can accept a focal reducer, but I don't think that's what you're talking about. [/quote]

Most Intes Micro MCTs and other high end russian/Euro designs are f/10. Some are slower but most are f/10.

#114 ColoHank

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Posted 13 February 2013 - 11:58 AM

As you point out, the big advantage to the Mak is not it's performance characteristics relative to the refractor, but it's cost, weight, shortness, ease of mounting, and, arguably, it's fairly refractor-like performance, which sums up the whole reason the design ever came about in the first place. Same arguments would apply to an SCT.



I've read somewhere that the design came about because Dmitri Maksutov wanted to create a relatively low-priced, easy-to-manufacture scope (originally all spherical surfaces) to equip Soviet classrooms. His intent, while laudible, wasn't to rival refractor performance or stimulate discussion, though it appears he's done both.

#115 Asbytec

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Posted 13 February 2013 - 12:32 PM

Nice comment, Eric. Id simply add the Mak is a little narrow for some folk's preferences, but its certainly not a debilitating handicap relative to the design strengths. I star hop with mine and love the lunar and planetary views, to some extent thanks to the focal length and narrow FOV.

#116 Mark Costello

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Posted 13 February 2013 - 06:35 PM


...........

(and FWIW, to list only Chinese f/12-f/15 MCT and Questars as the only available options is just plain wrong...or once again, claiming what one 'knows' is what they read from the latest Orion catalog...those were shipped across an ocean to the N America for those who might be under the impression that ordering from a vendor on another continent won't lead to the same method of arrival)





I was one of those, if not the only one who wrote that. Yes, I know I "can" buy an Intes-Micro MCT from a vendor on another continent and it'll get here in a boat as the MCTs come to Orion. But as a practical matter, I stand by what I said. From where I sit I see at least two differences between buying a foreign MCT from an American vendor (Orion) and buying one from a foreign vendor. They are VERY material in any decision I might make on brand IF I decide to buy an MCT.

1) Orion can place an order for several (5, 10, 50 etc.) MCTs on some periodic or occasional basis and probably get a break on shipping. Sometimes they pass that break by offering free shipping (they are doing that right now for bulkier Dobs.) A European vendor will ship one MCT and they have to charge me shipping for that one scope to make a fair profit and so I have to pay the full shipping costs for the one MCT. I see that as a big difference.

2) If there are any problems with a MCT sold in America, Orion, I can get some kind of satisfaction from the vendor within a reasonable time frame. My impression is that that I may be out on a limb if there is a problem of any kind with the particular MCT that gets shipped to me. That makes me pause and stop even though the I-T MCTs evidently have high build quality, it's just the idea that one unit might have a defect and I get it and the vendor is an ocean and a continent away.


NOTE TO ANY FOREIGN VENDOR: In writing what I wrote, I mean no disrespect at all and am only conveying my honest concerns. If I'm in the wrong, I'm willing to learn better from YOU.

#117 Eric63

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Posted 13 February 2013 - 08:02 PM

Hi Norme

I had a new experience in star hopping with my Mak. In addition to my Telrad, I added a 9X50 RACI finder. I was at a dark site last weekend and the finder became a nice little wide field scope that allowed me to scan the sky for something interesting and then zoom in for a closer look with the Mak. It was a new way of using the Mak and I loved it. And all from the comfort of my observing chair :grin:

Eric

#118 Asbytec

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Posted 13 February 2013 - 09:09 PM

:)

You know, Eric, I grind trough it the old fashioned way. Jupiter and the moon are not tough, but a 10th mag double can be. Still, its very doable and sometimes enjoyable. The ~1 degree field is plenty, really, once you get close. But, I like that you found a nice method.

#119 BPO

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Posted 05 May 2013 - 08:59 PM

Yes, that was my point.

#120 Eddgie

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Posted 06 May 2013 - 07:59 AM

I've read somewhere that the design came about because Dmitri Maksutov wanted to create a relatively low-priced, easy-to-manufacture scope (originally all spherical surfaces) to equip Soviet classrooms. His intent, while laudible, wasn't to rival refractor performance or stimulate discussion, though it appears he's done both.



In fact, his attempt was indeed to rival refractors, and he no doubt succeeded.

But you have to remeber that the refractors he was attempting to rival were the refractors that existed at the time, which were long focus achromats.

And with long focus achromats, once you get bigger than about 4", you are limited by chromatic abberation.

Now the funny thing is that with MCTs, once you get bigger than about 4", you are limited by higher order spherical abberation.

If you keep the focal lenght long though (f/15 to f/18) you get three big benefits.

The first is the very small obstruction, and while this slighly lowers contrast, it would be no worst then the chromatic abberarion caused by using a similarly fast large achromat.

The second is that that the system is somewhat easier to make, though this is in fact not a major benefit becuse there are three spherical surfaces vs four for a refractor.

THe last is the mounting, where you can easily mount a 6" f/17 MCT vs a 6" f/17 achromat.

There is another issue as well. When this design was first created, there were no modern coatings. This meant the MCT acutally enjoyed a slight advantage in light transmission. Silvered optics required recoating, but were very high tranmsission. Large refractors had much more light loss than can be achieved today.

So in fact, the MCT design was superior in many ways.

As for the field of view, at f/17 each instrument would have esentiall the same field.

Once again, one must remember the state of the art during that time. Eyepicees were mostly Orthos or Kellners, and these eyepecies were rarely allowed to an apparent field of more than about 40 degrees. This means that if you had a 1" eyepeice, you were limited to a field stop size of about 20mm.

The MCT baffle and secondary was allowed to be very small because once again, eyepeices of the day simply did not need a big baffle.

Bottom, line... Back when the design was introduced, it was in fact a better telescope than the long focus achroamt that it very quickly replaced.

#121 bierbelly

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Posted 06 May 2013 - 10:59 AM

The solution


<----------

#122 Classic8

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Posted 06 May 2013 - 01:15 PM

I suppose if you're used to Newts, the typical FOV in a Mak seems constricting. If you're used to an SCT or long f/l refractor, the difference probably doesn't seem nearly as noticeable. Most of the objects I've looked at fit into a Mak's FOV at low power. It isn't THAT narrow.

#123 Eddgie

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Posted 06 May 2013 - 02:05 PM

It's all relative of course.

I find that even with the C14, the great majority of deep sky objects easily fit into the field.

In fact, I have been using Binoviewers for the last year and a half, and even limited to 1.25" format, most things I like to look at still fit into the field.

But then there is the really big stuff. Large open clusters, and even larger star clouds.

Even a 2 degree field will not allow you to frame many of these objects.

There are always tradeoffs. Even the finest APO made is limited by the diffraction of its own aperture and to break that limit (by going progressively larger) starts to impose other limits (cost and the increasing concern of chromatic aberration).

The tradeoff of the MCT is an excellent one. If well designed with a very small central obstruction, if offers contrast performance with no meaning full difference to a similar sized APO.

The tradeoff is that it will not be able to show as wide a field.

Is that bad? I don't think so.

It just is what it is.... A design that has to made to a long focal length to maintain contrast to a similar sized refractor. The penalty is a narrower field.What is wrong with that?

#124 Ed Holland

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Posted 06 May 2013 - 07:34 PM

^Nothing, and one benefit, usually, is lower cost :)

#125 Jon Isaacs

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Posted 08 May 2013 - 06:34 AM

I find that even with the C14, the great majority of deep sky objects easily fit into the field.



This has something to do with the fact that historically, telescopes that were used to discover DSOs had a narrow field of view. If one has dark skies, there is a whole big world out there beyond what can be seen with a focal length approaching 13 feet.

Jon






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