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Equipment Discussions >> Cats & Casses

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RogerRZ
Whatta you lookin' at?
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Reged: 01/09/06

Loc: West Collette, NB, Canada
Re: "But Maks have a narrow FOV" - WTH??? new [Re: ColoHank]
      #5670867 - 02/09/13 02:44 PM

Quote:

Which explains why there are more Chevrolets than Rolls Royces, but we all know which is the better automobile.




If you could get a RR for Chevy money, I doubt there would be many bowties on the road.


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: "But Maks have a narrow FOV" - WTH??? new [Re: Eddgie]
      #5671944 - 02/10/13 08:07 AM

Quote:


Maksutov-Cassegrains have a narrow maximum possible true field of view, have difficulty achieving large exit pupils and low magnifications and move on.

Quote:


Ah, but it is all relative, isn't it? And that is what telescope design is about.







Relative or not, it just is... Design is about accepting the restrictions and limitations as engineers do, as another parameter. You recognize it, accept it and consider it when making choices.

If you want to look at history, there always were large Newtonians and there still are. If one wants the best possible planetary views and the seeing is sufficient to support a large aperture...

Just to note:

"And that remains the case today. I don't know why anyone in their right mind would buy a 7" f/18 achromat when they could buy a 180mm MCT and get esentially the same performance for a fraction of the price."

Once it's cooled down, maybe...

Jon


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Eddgie
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Reged: 02/01/06

Re: "But Maks have a narrow FOV" - WTH??? new [Re: Jon Isaacs]
      #5672198 - 02/10/13 11:43 AM

I'd rather carry a 7" MCT, mount, and cooling fan than carry out a 7" f/18 refractor and the mount for it.

For what I would pay for the mount for the refractor, I could have a custom made cooling fan for the MCT.

It is of course my own opinion, but I am sure that for every 7" f/18 achromat sold today, there are a couple of hundered 7" MCTs that get sold.

There really isn't anything a 7" f/15 MCT can't do as well or better than a 7" f/18 achomat. Saying cooling is some kind of obstacle seems to me to be less than solid logic when it is a problem that is easily delt with.


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RichD
Carpal Tunnel


Reged: 11/08/07

Loc: Derbyshire, UK
Re: "But Maks have a narrow FOV" - WTH??? new [Re: Eddgie]
      #5672834 - 02/10/13 06:36 PM

I love my little 5" mak. I got it originally as a grab and go scope for looks at the moon and planets as I was getting tired of lugging out the 12" dob all the time. I wasn't expecting much in the way of deepsky from it but I was very pleasantly surprised, after all it has a max true field of 1 degree so will fit about 95 of the messier catalogue objects.

I think the saying that Maks have narrow fields of view has come about maybe from advertising and advice given to new astronomers in part. You could imagine a noob being slightly disappointed with a Mak if they pointed it at the pleiades or M31. More experienced observers know that it is horses for courses and that MCTs are better suited to those objects that fit a 1 degree field or thereabouts, but how are beginners supposed to know this? they don't so sayings like these get thrown around and after a while they become believed by people.


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: "But Maks have a narrow FOV" - WTH??? new [Re: RichD]
      #5672922 - 02/10/13 07:35 PM

Quote:


I think the saying that Maks have narrow fields of view has come about maybe from advertising and advice given to new astronomers in part. You could imagine a noob being slightly disappointed with a Mak if they pointed it at the pleiades or M31. More experienced observers know that it is horses for courses and that MCTs are better suited to those objects that fit a 1 degree field or thereabouts, but how are beginners supposed to know this? they don't so sayings like these get thrown around and after a while they become believed by people.




And you are saying that the maximum possible field of view of a Mak-Cassegrain is not narrow in comparison other telescopes of the same aperture? Saying that more experienced astronomers know that a 5 inch Mak-Cass is limited to a 1 degree TFoV seems to me to be saying that a 5 inch Mak-Cass has a Narrow Maximum Possible Field of View in comparison to other 5 inch scopes.

"Believed by some people", it's just how it is, there is nothing to believe or disbelieve, it's a matter of understanding...

Jon Isaacs


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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: Eddgie]
      #5672936 - 02/10/13 07:40 PM

Quote:

There really isn't anything a 7" f/15 MCT can't do as well or better than a 7" f/18 achomat. Saying cooling is some kind of obstacle seems to me to be less than solid logic when it is a problem that is easily delt with.




If you want to play games... a 7 inch F/12 or F/15 or whatever focal ratio achromat does provide a substantially brighter image than an 7 inch F/15 Mak.

Disassembling the scope, cutting holes in the tube, installing fans, how many really do that???

The proper scope to compare to a 7 inch Mak is a longer focal length Newtonian, the achromat is red herring.



Jon


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Asbytec
Guy in a furry hat
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Reged: 08/08/07

Loc: La Union, PI
Re: "But Maks have a narrow FOV" - WTH??? new [Re: Jon Isaacs]
      #5672954 - 02/10/13 07:53 PM

Jon, Rich may have a point. Seems, per the OP, they have a rep for a narrow FOV and for some reason thats a bad thing.

As you correctly say, without understanding, such a rep - no doubt promoted by the 'fracter crowd through fear of Mak 'fracter like performance - gives MCT FOV a bad name. It might turn some folks off, those who prefer wide fields and those who do not understand.

Same with cool down.


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RichD
Carpal Tunnel


Reged: 11/08/07

Loc: Derbyshire, UK
Re: "But Maks have a narrow FOV" - WTH??? new [Re: Asbytec]
      #5673476 - 02/11/13 04:16 AM

I didn't explain my point very well. I was trying to say that the term "narrow field of view" is often mentioned of MCTs and that the uninitiated may think that this really limits their use drastically to a small range of objects.

It is true that a 5" MCT has a narrower TFOV than an similar sized reflector or even an SCT, but the above saying though it is true also, gives the MCT a reputation which is not fully deserved IMO.

Of course I take your point John and indeed this is the way I think about the matter, but when I am out with my Mak and looking at M41 or M50 say with a 24mm Panoptic giving a hair over a 1 deg field, I sometimes find myself thinking of all the comments I have heard or read over the years that a small mak is no good for deepsky and smiling to myself.


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ColoHank
Carpal Tunnel
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Reged: 06/07/07

Loc: western Colorado
Re: "But Maks have a narrow FOV" - WTH??? new [Re: RogerRZ]
      #5673746 - 02/11/13 10:10 AM

Quote:

If you could get a RR for Chevy money, I doubt there would be many bowties on the road.




If you could get a Rolls Royce for Chevy money, it wouldn't be a Rolls Royce; it would just be another Chevy.


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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: RichD]
      #5673757 - 02/11/13 10:14 AM

Quote:

Of course I take your point John and indeed this is the way I think about the matter, but when I am out with my Mak and looking at M41 or M50 say with a 24mm Panoptic giving a hair over a 1 deg field, I sometimes find myself thinking of all the comments I have heard or read over the years that a small mak is no good for deepsky and smiling to myself.




There is no doubt there are plenty of wonderful DSOs to be seen with a 5 inch Mak..

I am an admitted Widefield/Richest field Junky, I spend a good amount of time looking more than small, named objects This is the way I look at it:

There are many objects with in the range of a 5 inch Mak with a 1 degree maximum True Field of View. Granted, this is is significantly narrower than the 1.35 degree TFoV possible with a 16 inch F/4.4 and M7 in the big scope will show details just not visible in any small scope. But still, there are a great number of objects, visible in a 5 inch with a 1 degree TFoV.

However, if one looks at the things that a small aperture scope does better optically than a large scope, that is, "What can a small scope show me that a large scope cannot?" Resolution, contrast, light gathering, these are all on the side of the larger scope. And certainly the portability factor of a small scope is important. But at the eyepiece, the right small scope can offer wider fields of view than a large scope, otherwise that's about it.

Widefields of view may or may not matter... They do to me. If I am out where the skies are dark and clear, I have some sort of glass and plywood and aluminum contraption setup and I am checking out the Veil Nebula, it's pretty sweet with a 6mm exit pupil at 70x with an O-III filter but I can only see part of it at one time. A 5 inch Mak-Cass is not going to show me anything new but a 4 or 5 inch F/5 or F/6, it'll show me a view of the Veil that is not possible with the larger scope.

The "limited" possible field of view of the Mak-Cass just is. It's not something to argue about, it's not something to deny, it's something to understand, to be aware of and to accept. It just is, the same way a 25 inch F/5 Newtonian is about 10 feet tall. It's not something to deny, to argue about, it's something to understand, to be aware of and to accept.

Jon

Edited by Jon Isaacs (02/11/13 02:07 PM)


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KerryR
Carpal Tunnel
*****

Reged: 12/05/07

Loc: SW Michigan
Re: "But Maks have a narrow FOV" - WTH??? new [Re: Jon Isaacs]
      #5673801 - 02/11/13 10:38 AM

It's worth noting the the narrow FOV reputation IS a worthwhile consideration for neophytes, for whom ANY long focus scope, and it's inherent narrower FOV, can impose difficulties in target acquisition when learning to star hop. I believe it is with beginners in mind that the narrow FOV thing is promoted, for good reason. This doesn't have to be a hard and fast 'rule', especially in consideration of other important factors such as cost, size, weight, and ease of mounting, not to mention (accurate) go to, but certainly worth consideration.

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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: "But Maks have a narrow FOV" - WTH??? new [Re: KerryR]
      #5673817 - 02/11/13 10:52 AM

Quote:

It's worth noting the the narrow FOV reputation IS a worthwhile consideration for neophytes, for whom ANY long focus scope, and it's inherent narrower FOV, can impose difficulties in target acquisition when learning to star hop. I believe it is with beginners in mind that the narrow FOV thing is promoted, for good reason. This doesn't have to be a hard and fast 'rule', especially in consideration of other important factors such as cost, size, weight, and ease of mounting, not to mention (accurate) go to, but certainly worth consideration.






It is certainly more difficult to starhop with a 90mm F/14 Mak than a 80mm F/5 ST-80...

Jon


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Asbytec
Guy in a furry hat
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Reged: 08/08/07

Loc: La Union, PI
Re: "But Maks have a narrow FOV" - WTH??? new [Re: Jon Isaacs]
      #5673969 - 02/11/13 12:28 PM

Quote:

The "limited" possible field of view of the Mak-Cass just is. It's not something to argue about, it's not something to deny, it's something to understand, to be aware of and to accept.




Again, that is a most excellent point, Jon. Seems, though, too often the FOV is portrayed as a bad thing to be avoided. Along with cool down, these two aspects are driven home giving the MCT an undeserved bad reputation. Those two conditions are almost synonymous with MCTs. Mention a Mak, and someone will bring either or both into the discussion almost as if a Mak has a form of cancer. It simply perpetuates the myth and does nothing for understanding the design.


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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: Jon Isaacs]
      #5674011 - 02/11/13 12:52 PM

Quote:

If I am out where the skies are dark and clear, I have some sort of glass and plywood and aluminum contraption setup and I am checking out the Veil Nebula, it's pretty sweet with a 6mm exit pupil at 700x with an O-III filter but I can only see part of it at one time.





That must be a really small part of the veil. Or is that 70x with a 31mm Nagler in the 16" scope? Or do you have a scope with a 21000mm focal length and 4200mm aperture to get to 700x and a 6mm exit pupil? Or a 310mm Nagler? I know that Newtonians are fantastic scopes, but . . . maybe I am misplacing a decimal point somewhere?


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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: spencerj]
      #5674024 - 02/11/13 01:01 PM

I think as a general rule, people who buy a 2 door coup understand that the vehicle does not have seatbelts for 9 passengers. Maybe it just doesn't need to be pointed out repeatedly in the the 2-door-coup forum. Maybe we could just all assume that we understand the personal choice and "compromise" that was made when the car was bought.

In the Beginner's forum . . . fair enough, but here . . . it should not be necessary.


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KerryR
Carpal Tunnel
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Reged: 12/05/07

Loc: SW Michigan
Re: "But Maks have a narrow FOV" - WTH??? new [Re: spencerj]
      #5674088 - 02/11/13 01:41 PM

I wouldn't expect folks new to the hobby to limit themselves exclusively to the beginners forum. They can and should investigate and partake in any forum of interest. Otherwise, when would one 'graduate', specifically, from the beginners forum?

I'm unaware of a forum where any scope's short comings are not a constant source of discussion. For example, it's rare for someone to post a question on a short focus achromat in the refractor forum and not have someone point out, obvious though it is to many of us, that the poster may find chromatic aberration limiting. If the poster was already aware, no harm done. If not, they learned something, even less harm done. And, let us not forget the many folks who read but don't post who may have learned something.

Point is, we're ALL here to discuss scopes, even though we have varying expertise and experience, so why wouldn't we discuss the most relevant attributes (comparatively narrow FOV in this case), and even the less relevant attributes (does narrow FOV matter and to whom)? It's certainly what I see going on in the other forums.

I think the source of the sore spot may be that limited FOV is less frequently mentioned with other Cats, particularly the SCT. It should be. But that's a different argument to one that suggests discussion or mention of certain inherent design limitations should be taboo in a given forum.


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: "But Maks have a narrow FOV" - WTH??? new [Re: spencerj]
      #5674141 - 02/11/13 02:14 PM

Quote:

I think as a general rule, people who buy a 2 door coup understand that the vehicle does not have seatbelts for 9 passengers. Maybe it just doesn't need to be pointed out repeatedly in the the 2-door-coup forum. Maybe we could just all assume that we understand the personal choice and "compromise" that was made when the car was bought.

In the Beginner's forum . . . fair enough, but here . . . it should not be necessary.




I would say this: Why then the complaining... Everyone knows a Mak has a narrow FOVin comparison to other designs of equal aperture, so are we even bothering with this thread?

Jon


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Asbytec
Guy in a furry hat
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Reged: 08/08/07

Loc: La Union, PI
Re: "But Maks have a narrow FOV" - WTH??? new [Re: KerryR]
      #5674143 - 02/11/13 02:16 PM

Good comment, Kerry.

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Ed Holland
Carpal Tunnel


Reged: 06/16/10

Loc: San Jose, CA and Oxford, UK
Re: "But Maks have a narrow FOV" - WTH??? new [Re: Asbytec]
      #5674183 - 02/11/13 02:53 PM

On the flip side, one nice thing is that one can reach the higher useful magnifications for planetary with longer focal length eyepieces. That is a helpful feature (to me) for Lunar & planetery work & the occasional double star viewing.

My 127mm (118 ) f/12 Mak has served very well as a planetary scope, giving views that complement those I can obtain from a 5" refractor of f/9.3. The refractor has a little more to offer on feignt targets, but I'm pretty limited by haze & light pollution most of the time. The refractor is not immune to cool down issues in the form of tube currents. On the flip side, these issues are easily avoided in either scope by planning equiment setup ahead of viewing.

A telescope collection is like a socket set - pick the right one for the job. I'm dead lucky to have a few modest but fun instruments to enjoy. Each has a character of its own which adds variety to viewing the heavens


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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: Asbytec]
      #5674188 - 02/11/13 02:55 PM

It is just that sometimes, certain things get repeated so often that they become disconnected from their original purpose--as pure and chivalrous as that may have been.

There is currently a post in this very forum where an experienced observer is truly baffled with the performance of a 41mm Panoptic and 26mm Nagler in a C6. He expected disastrous results based on the math and ray traces and the factual drop in edge of field illumination (and probably posts from members of this community). Yet when he actually tried it . . . the combination worked fine. He was pleased with the view.


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