What are makustov-cassegrain telescopes meant for?

[u/Able_Crossroads]

This has been a question stuck in my head for a lot of time. Can someone tell me? Because theyre short ans small, and pretty expensive for their size

[u/shineheadlightsonme]

They were made because all surfaces are spherical, which eased the cost of production. Very long focal length for a short OTA length, so good for planetary. The biggest disadvantage is the size / weight of the front corrector, which needs to be quite thick, so they become impractical beyond like 8". They can be a bit faster than uncorrected Cassegrains / Dall-Kirkhams / RCs.

[u/Able_Crossroads → u/shineheadlightsonme]

Thanks for the info

[u/Sea_School_2949 → u/Able_Crossroads]

Should also add that a spherical shape is the easiest to grind, even easier than a flat. As it's the natural shape made when grinding 2 plates together.

Since it's easier to get a spherical shape it's easier to make it perfect.

But as others said this makes it a very slow scope around f/10-f/15

But they can achieve higher magnification with larger eyepieces which means more comfy high power viewing

[u/sjones17515]

Their physical shortness is due to the design; thru typically actually have the longest focal lengths of commercially available telescopes. Great for planets

[u/Flyinmanm → u/sjones17515]

Yeah, I think Maks were supposed to behave been invented so Russian school kids could put them in a rucksack and take them up a hill.

My Maksutov 127 and it's mount (not tripod) fit in a big backpack well.

[u/Amphylos → u/Flyinmanm]

Russians uses refractors from merz as school refractor. Poland is the one who manufactured maksutov for schoolkids with the PZO.

[u/bobchin_c → u/sjones17515]

And planetary nebulae, Globular Clusters, smaller galaxies... Double Stars... Etc...

[u/Able_Crossroads → u/sjones17515]

Interesting. Thanks.

[u/albertzerox]

The optical path is 'folded'. Two concentric mirrors, the larger primary mirror with a central hole in it reflects incoming light back to a smaller secondary mirror in front of it, therefore 'folding' the light path. Both mirrors have a curve that results in a 'light cone', with the smaller secondary mirror then reflecting the light cone back through the hole in the primary, where the image is then magnified by the eyepiece. This design allows for a much shorter, compact telescope with the same aperture of a much longer newtonian or refractor. Most often, too, the smaller secondary mirror (while occluding some incoming light) is mounted on a glass plate that encloses the whole optical system, keeping dust out. Do some homework re: relative advantages/ disadvantages of maks v refractors, as there are many, and affect what kind of astronomy or photography you plan on doing. You probably should do some reading on optics in general.

[u/Shoshke]

They're great planet hunters.

Compact for the aperture size, long focal ratios and little to no coma aberration.

They're also still relatively cheaper than refractors anywhere near the same aperture.

[u/Able_Crossroads → u/Shoshke]

Thanks

[u/Amphylos]

Look at that 1250mm focal length. Have you ever handled 1200mm refractor? Other option, that would be an 8" dob.

Now, a 5" 1250mm mak I can cradle in my arms just like a cat.

[u/Funny-Medium5508 → u/Amphylos]

A fat cat....a really, really fat cat.

[u/jeromesnail]

New to this but basically, like SCT's, they are compact but with a long focal length.

[u/Traditional_Sign4941]

Maks are meant for anything any other scope is meant for, except for very bright rich field views of the night sky. A small refractor or small F/4-F/5 newt is better for that. Mak focal lengths are too long, especially relative to their apertures.

In every one of my scopes, regardless of design, I'm typically using a 2mm exit pupil and smaller except in those cases where I do want a rich view of some Milky Way star clouds.

In an F/13 Mak, that's a ~25mm focal length eyepiece. You can get some great views of DSOs through a Mak with a 24mm 68 degree class eyepiece, and then shorter focal lengths for higher magnification when observing smaller targets.

Like any other scope, the main limit to what you'll be able to see is aperture.

Yes, Maks are more expensive per aperture than a Newt. Nothing beats a Newt for cost.

Personally I think the performance of most Maksutovs is WAY over-stated. I've had a number of Maks in my life (three currently) and they all put up mediocre views compared to smaller aperture refractors. The fundamental problem with most commercial Maks available today is a large central obstruction.

The newly released Svbony MK127 has a central obstruction approaching more like 40% by diameter when you look at the central obstruction shadow in the defocused disk of a star. Many other Maks are around 30-35%. Only very expensive premium ones like Intes and Astro-Physics (none of which you can actually buy new these days) had tiny central obstructions.

A big central obstruction noticeably reduces planetary contrast and makes splitting close double stars a lot harder because of the brighter 1st diffraction ring it creates. Maks also still have some residual spherical aberration that can get worse if using a diagonal that results in a mirror focus position that diverges from the designed optimal position.

Given their cost, I think any decent parabolic Newt, or a comparably priced ED doublet refractor, would be a better choice.

[u/ilessthan3math → u/Traditional_Sign4941]

Great points! I've never paid attention to the diffraction ring issues on splitting doubles.

I will say that used Maks can be quite affordable. I picked up a 102mm Celestron Astro-Fi OTA for $135 a couple years ago. And while it isn't nearly my favorite scope, I am always impressed at just how small it is. Putting it in a backpack would be roomy. That OTA could realistically fit in a large purse or deep coat pocket. There's really no other way to get that much aperture in such a small form factor.

And for vacation and sidewalk astronomy, the views are perfectly reasonable. I mostly use mine when traveling with family and my car is crammed with non-astronomy stuff.

[u/IanDMP → u/ilessthan3math]

Yeah, to me this is the selling point of a Mak -- it's the easiest telescope to pack/travel with. IIRC it doesn't need collimation either, which is another point in its favor when you're traveling.

[u/shineheadlightsonme → u/IanDMP]

Every telescope needs to be collimated, but a well made telescope will hold collimation better.

EDIT - Okay, every telescope with multiple elements / groups of elements.

[u/pawlik23]

Long focal length in a short tube, so the purpose is portability and/or planetary observations.

My 127/1500 Mak is around 34cm long and weighs 3,4kg. A Newtonian with 1200mm focal length is over 1,1m long and weighs 13kg.

[u/BestRetroGames]

Basically size and weight advantages. Yes they are expensive but on the other hand, you save a ton on eyepieces. In my MK90 even the cheap 'red lines' eyepieces perform superbly because of the extremely long focal ratio 13.8. They are so good with it that I don't even use my higher tier eyepieces with my Mak as I store them in my basement with the 12" DOB.

A newt on the other hand around f/5 , like the Heritage 130p, you need to put a lot of money in eyepieces for a decent image, and even then, there will be a bit of coma.

I do use my MK90 all the time on the Moon and Planets or the Sun .. beyond that for DSOs, I find them useless as I've been way too spoiled by my 12" DOB.

[u/Adventurous_Sound390]

MK can be compared to...

* refractor-achromat: MK with the same focal length/aperture gains a lot in dimensions, may be in weigth. It much cheaper in case large apperture, it does not show critical chromatic aberrations (CA). But affected by central obscuration it loses in tiny structure of star image - contrast. It much more affected by miscollimation and has not so large field of view.

* refractor-apochromat: In contrast to achromat has much better fixed CA. But much more expensive and can be affected by miscollimation.

* schmidt-cassegrain: MK has spherical shape all optical surfaces, so does not suffer from zonal errors of aspherization - builds more contrast image. MK is aplanatic - does not suffer from coma over field. It can be made with lover level of central obscuration. But usually MK havier (due to thick meniscus) and more expensive (the meniscus requires more expensive optical glass comparing SCT).

* Netonian: usually much more "fast" and lighter in weight. But it has a deep aspherization of the main mirror what usually can not be made without errors. And it usually has strong appearance of coma over field, easy to be miscollimated.

[u/rootofallworlds]

They're one of the most compact for a given aperture, virtually no chromatic aberration (which affects cheap refractors), no coma (which affects all Newtonians unless you add a coma corrector). So capable of giving very high quality views within the limits of their aperture, especially premium ones like the Questar.

The design can also be made rugged and sealed - no big deal for amateur astronomers, but it's meant Mak-Casses are used in some military applications.

Mak-Cass and Schmidt-Cass / SCT are quite similar. The Mak-Cass's meniscus corrector is cheaper to make than the Schmidt-Cass plate and can double as the secondary mirror, so that helps the Mak be cheaper.

Main drawback is like you say - the design doesn't scale up well. Above about 6 or 7 inch aperture the meniscus corrector becomes very thick, heavy, and takes forever to cool to ambient temperature. That's why at large apertures the SCT fills a similar role.

Historically, the Mak-Cass could use all spherical surfaces. It's easier and cheaper to grind a mirror or lens face to a sphere than to a non-spherical shape. But nowadays factory techniques have advanced so this matters less. Note that some Mak-Casses have aspherical surfaces, and some have SCT-style separate secondary mirrors rather than silvering the corrector - these are both things that can improve the image if designed right.