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Maksutov's


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Hi

Can somebody please explain a little about maksutovs to me as i dont quite understand how they work or what type of observing they are best used for.

i notice that they look rather small but have large focal lengths (much larger than they physically look) how is this achieved?

Cheers!

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Maksutovs have long focal lengths because the light enters the front through a thin correcting lense to the primary mirror at the back of the scope. The light is then reflected back up to the front of the tube to a small secondary mirror attached to the centre of the correcting lense and then back down to the other end of the scope through a hole in the centre of the primary mirror and through the eyepiece. This longwinded 3 step reflection path provides the long focal length in such a short tube.

Maks have the reputation of being excellent at providing clear crisp views for lunar and planetary observing owing to the long focal length and relatively large aperture that would normally be provided by a much bigger refracting scope.

I came close to buying a Mak 127 but decided on a shorter focal length 102mm refractor instead, which cools down a bit quicker and doesn't attract dew so quickly. I wouldn't rule out buying one myself in the future though.

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I got a Celestron 127 SLT mak. Love it so far, managed to get my first views of Saturn last night which was pretty breathtaking. If portability/storage space is an issue then mak's are better suited than some other scopes, which is one of the reasons I went for one.

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A Mak will be as good on on a DSO as a reflector of the same aperture. Never sure why it is said they are poor on DSO's.

For a DSO's you simply need to collect as much light as possible, as long as the aperture is large it does not matter what scope type it is.

A Mak is a folded scope. It is a simple spherical mirror of some focal length. the front glass is a corector plate to compensate for the errors of the spherical mirror.

The reason they are long focal lengths is simply that it is easier and so costs less to make a corrector for a long focal lengh spherical mirror then it does for a short focal length one.

As the focal length is long people are tempted to go for magnification, all well and good but as the image gets bigger the brightness gets lower, so on DSO's the answer is simple, don't go pushing the magnification just because you can.

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Only the very largest DSOs are too big for my Mak - the Pleiades and M44 most notably. You could argue that other DSOs are not seen to their best effect as there is not much framing darkness around the object, but that also applies to only a few objects.

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This longwinded 3 step reflection path provides the long focal length in such a short tube.

- but perhaps not in the way people might expect :)

The primary mirror is actually a very "fast" mirror, but the secondary acts like a kind of mega-barlow, slowing it down to the famously "slow" focal ratio that Maks have.

So the effective focal length is a lot more than 3x tube length.

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Only the very largest DSOs are too big for my Mak - the Pleiades and M44 most notably. You could argue that other DSOs are not seen to their best effect as there is not much framing darkness around the object, but that also applies to only a few objects.

Completely agree. Whilst it's true Maks miss out on some "showcase" DSOs, there's nothing that makes them intrinsically unsuitable for the vast majority of other DSOs.

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In addition to the correct information posted by great_bear, the corrector "lens" of the Maksutov is quite thick, around 10mm for a 6"-8" and 18mm for a 12". The refractive index of the glass and its thickness are important factors in the corrective power of the "lens".

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-The primary mirror is actually a very "fast" mirror, but the secondary acts like a kind of mega-barlow, slowing it down to the famously "slow" focal ratio that Maks have.

So the effective focal length is a lot more than 3x tube length.

Aaah, now that I didn't know.

@Spitfire12 - please excuse my overly simplistic explanation above, The Mak is more ingenious than I realised! :)

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Of course there is more than one kind of "Mak" design. The conversation here has concentrated on the Maksutov-cassegrain design, which is the most common one found. There is also the Maksutov-newtonian which is a true all-round scope in my opinion. I have a 6" Mak-Newt made by the Russian company Intes. It is a relatively fast scope (F/5.9) so you can get very nice wide field views but it's very small secondary mirror also means that it delivers superb lunar and planetary views as well. The best of both worlds for visual use :)

Edited by John
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And with Mak-Cass's there are two popular designs. The Gregory Mak(with silvered spot on the miniscus) and the rumak, or Rutten Mak(seperate mirror fitted to the miniscus).

Intes and Intes-Micro seemed to have popularised the latter. I've had the fortune of using a 5" and 7", both F10. Superb optics and build. Not cheap, but simply wonderful optics.

To confuse matters still, there is the Klevtsov Cassegrain and Vixens Sub Aperture Mak-Cass(VMC). I currently use an 8"F10 version of the former.

Andy.

Edited by AndyH
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I'll second nightfisher on that. M42 looks fabulous in my mak, as do many other dso's. The long fl allows you to use ep's with plenty of eye relief and they have great contrast. Globulars look amazing! As has been said, there are only a very few objects too big for the fov

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the best view i have had of M42 has been with my omc-140 deluxe

I looked up your scope - the OMC140 Deluxe - on the Orion Optics web site. Looks like a particularly lovely Mak scope indeed... Very nice :)

Edited by great_bear
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I looked up your scope - the OMC140 Deluxe - on the Orion Optics web site. Looks like a particularly lovely Mak scope indeed... Very nice :)

cheers, it is a very good scope, superb optics and to be honest a bit of an all rounder, it very nearly went up for sale this week as i was tempted by a larger mak, but in the end i decided to keep it

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  • 2 weeks later...

Thanks for all the info!

looks like i will be considering a mak however im happy with any type of scope, im just on a mega budget so im keeping my eyes peeled for a bargain and cant afford to be choosy.

im sure anything is going to be better than my cheapo jessops scope, complete extra wobbly mount!

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cheers, it is a very good scope, superb optics and to be honest a bit of an all rounder, it very nearly went up for sale this week as i was tempted by a larger mak, but in the end i decided to keep it

I swear that one day that mak WILL be mine!!!:D

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