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    Default maksutov-cassegrain?



    I am looking for some pros and cons for the maksutov-cassegrain from people who own them or have used them in the past? I am mainly a planetary observer? I am think the long FL will be good for that? also how easy is Planetary Imaging with one of these scopes? I know they can take a long time to reach thermal thermal equilibrium but that is not a big problem for me know becuase i have a backyard i can leave it out in for a while before use. so no CA or collimation needed?

    Cassandra

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    Default Re: maksutov-cassegrain?

    Maks are good for planetary observing. It is not so much that they are better at planetary observing than other types, but more that they aren't very good for wide-angle observing, such as DSOs. Their suitability for other observing can be improved by adding a focal reducer.

    Maks tend to be made in smaller apertures. 6" is the largest I have ever heard of; most are smaller. So, in spite of the slow focal ratio, the focal length is not particularly long. A modest SCT will have a longer focal length than most Maks, and will therefore be better for planetary imaging.

    What a Mak excells at is as a grab-and-go scope. Because of the small size, they are extremely portable.

    Maks don't need much collimation. Some are in fact permanently collimated at the factory, with no provision for collimation in the field.
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    Default Re: maksutov-cassegrain?

    I use them, I like them. In fact my 127 Mak is probably the one I use the most, followed by my grab and go 90MM. I'm maybe looking into getting a 180MM Mak in the future. People claim they're only good for planetary objects and the moon, but I find them more flexible then that. With my 1.14 degree FOV, I can fit in all but 5 of the Messier objects. I may be the exception, but for me my "widefield" scopes (my 102 and 70MM Travelscope) are my specialty scopes, while my Maks are my workhorses.

    The long focal length does a couple of things. First of all, it allows you to use longer focal length eyepieces to achieve the same magnifications. For example, let's compare the Explore Scientific 127MM Apo refractor, with a focal length of 950MM, with my 127MM Mak, with a focal length of 1500MM. They both have a generally useful magnification of 127x, and a theoretical max of 254. In the 127 Mak, you get that with a a 12MM eyepiece and a 6MM eyepiece respectively. For the refractor, you need a 8MM and 4MM eyepiece. If you're picky about eye-relief, that greatly reduces the eyepieces you have available.

    Long focal length scopes also tend to be far more tolerant of imperfections in the optics, either in the telescope or the eyepieces - certain eyepieces just don't do well in short f/ratio scopes, and the ones that do tend to be much more expensive.

    I've never found cooldown a problem, even in the winter, I just start off with a 35MM eyepiece, usually after 30-40 minutes or so, I'm good to go even if its stupid cold out. Your bigger issue is probably going to be dew (unless you observe on some sort of concrete surface, like a roof). It takes me around 10, 15 minutes to setup my scope, and I usually start observing some things at low magnification for another 15, 20 minutes or so. By then I'm ready to go. It could also be I'm pretty tolerant to some of the aberrations that occur when it isn't in thermal equilibrium, sometimes it can be hard to tell when you're looking at stuff in NYC.

    Because Mak's don't have much material between the corrector plate and the air, they are natural dew magnets. You'll want to pick up a dew shield, or make one on your own, and possibly a dew heater with strips. I recommend picking a dew shield regardless, because they help obscure outside light, and its a hell of a lot easier then reflocking the interior of your Mak (I am NOT doing that again). But before you get the dewheater and strips, try it out just with the dew shield first.

    You won't get much CA in a properly figured Mak, and yes, they're very tolerant of rough use if you're a klutz like me. Most of the Synta Mak's can be collimated if you need to using the screws in the back, but I haven't ever had to, even on my 90MM which I've taken on the AT a couple of times. They're also small and handy, which is really important if you don't have a car, like I do, or if you're a smaller individual. Or a weakling like me.

    If you're primarily interested in planetary stuff, the two "best" options are either an APO refractor or a Maksutov, with the former being significantly more expensive per inch then a Mak. The ES runs around $1900 for just the OTA, you can pick up the Nexstar 127SLT Mak on Amazon for around 400 bucks. To be clear, if money is no object, get a Takahashi or an Astro-Physics, and some Televue's and you're all set. Now, that being said, aperture is still going to be king, and the best scope is probably going to be a 25" dobsonian, but that's always the trade off, how much aperture can you stand.
    Last edited by Diogenes; 06-01-2015 at 12:44 AM.
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    Default Re: maksutov-cassegrain?

    Intes makes at least an 8" Maksutov-Cassegrain. Astro-Physics has made a 10-inch. I think bigger have been made but I'm not sure about that.

    The optics on a Mak-Cass seem to be relatively good. It is really nice for their size on planetary targets because the optics can be very satisfying and the slow optics means you use relatively long focal length eyepieces and thus even with a Plossl you get good eye relief for comfortable viewing.

    If you go for the big ones you really need a CAT Cooler since fairly rapid temperature drops are too fast for them and you can end up never reaching thermal equilibrium until the temperature starts increasing as the Sun comes up.
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    Default Re: maksutov-cassegrain?

    Cassandra,

    I have a 102mm f/13 Mak and a 120mm f/5 achro.
    I have started with the Mak and was very happy with planets, but not satisfied with DSOs.
    Now my Mak has better planetary views than my achro, whereas the achro gives me wider views and helps me better with DSOs.
    I am considering a FR for my Mak, but have not made my mind yet.

    If I had to start again, I might consider a 6" SCT with a focal reducer - maybe not the best of both worlds but close enough in just 1 scope. As Keith mentioned, you can get 1500mm instead of 1325mm - together with a significant increase in aperture, more light...

    Having said that, 2 toys is always more fun to play with - and my Mak is a great grab and go, with the additional easyness of a flip mirror for AP...

    Good luck with your choice!

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    Default Re: maksutov-cassegrain?

    As others have said, Maks make great planetary scopes for visual and also for good affordable planetary imaging. An equatorial mount is a plus but not necessary for planetary imaging, you can make due with a tracking alt/az mount. I have two very affordable webcams (Phillips and Logitech) that I use with Registax (free software) to make impressive planetary images with my 90mm Mak as well as both my SCTs.
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    Default Re: maksutov-cassegrain?

    For a start, the synta maks (celestron orion sky-watcher) have slightly reduced aperture than the number stated on their model, but there is no visible reduction in image quality compared to their Meade mak counterparts with a proper oversized primary mirror.
    127 = 120 , 180 = 170
    The reduced aperture pushes the focal ratio up slightly.
    The obstruction % stated on Orion's website is not accurate as it is only the mirror spot and not the bigger secondary baffle cup that open slightly wide like a trumpet. Closer to 40% obstruction for the mak127.
    Skywatcher Mak127 sold with 2" setup is closer to 1770mm focal length , not 1500mm

    Personally, I like it very much.
    It attaches easily to binoviewer without needing any troublesome barlow or corrector accessories. The whole weight (1.7lbs for binoviewer + 2 eyepieces) is not placed on the focuser unlike a newt or refractor. The image shift from focusing in/out on my mak127 is only 1-2 diameter of Jupiter, I experienced the same on my previous mak90.
    SCT and Mak will increase their focal length about 30% if you pop in a binoviewer simply , due to the mirror moving forward to push the focal point another 100mm further out the diagonal. I see it as a pro compared to newt users who have to use their 2x barlow to get it to focus.
    Last edited by apple123; 06-01-2015 at 04:10 AM.
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    Default Re: maksutov-cassegrain?

    The synta maks are not preferable for terrestrial viewing though, the baffle tube that goes through the primary mirror is not adequately black.
    The stray light causes the image to be washed out, less vibrant colors.
    Some of us mak users slide in a roll of (reversible and removable) flock material (painted and baked sandpaper for some extreme modders) to absorb light at this critical area.

    In my case , I flocked the primary baffle, secondary baffle, tube interior and added a dewshade made with black craft foam .....
    At minimum magnification of 48x at the mak , the daytime colour are not as vibrant as a 80mm F/5 achromat refractor at 16x magnification
    Chromatic aberration in the little refractor can be ignored casually and I like the wider field. I also noticed my eyeball could focus easier on the low magnification 80mm while the mak would need actual turns on the focus knob if I want to look at objects at different distance.
    Last edited by apple123; 06-01-2015 at 04:37 AM.
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    Default Re: maksutov-cassegrain?

    Quote Originally Posted by apple123 View Post
    The synta maks are not preferable for terrestrial viewing though, the baffle tube that goes through the primary mirror is not adequately black.
    The stray light causes the image to be washed out, less vibrant colors.
    Some of us mak users slide in a roll of (reversible and removable) flock material (painted and baked sandpaper for some extreme modders) to absorb light at this critical area.

    In my case , I flocked the primary baffle, secondary baffle, tube interior and added a dewshade made with black craft foam .....
    At minimum magnification of 48x at the mak , the daytime colour are not as vibrant as a 80mm F/5 achromat refractor at 16x magnification
    Chromatic aberration in the little refractor can be ignored casually and I like the wider field. I also noticed my eyeball could focus easier on the low magnification 80mm while the mak would need actual turns on the focus knob if I want to look at objects at different distance.
    Actually, I've found is that having a dew shield attached (at least on my C90) is pretty good on its own, and haven't felt the need to flock my C90. I did with my 127, but going forward, the dew shield is enough for me. I'm lucky enough to have found a 35MM Celestron Ultima, its a fantastic eyepiece and while it doesn't make the Mak a widefield instrument, I like it a lot for both daytime and nighttime viewing. Then again, the 90 MM only has a mag of 36x, so that might be it.
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    Default Re: maksutov-cassegrain?

    The reason a Mak generally not only does not require collimation but often cannot be collimated is because the secondary mirror usually isn't a separate component. It is usually a silver-painted section on the inside of the corrector plate (it's literally a coated circle directly on the front glass). Hence no adjustment screws and the only way it could possibly become mis-aligned is if the entire front corrector plate were to somehow become loose and go askew.

    On *some* Maks the primary mirror can be shimmed -- but usually not. The primary mirror usually rides on a central baffle (typical of the Cassegrain design). It'll get "image shift" depending on whether you are turning the focus knob clockwise vs. counter-clockwise. I always "finish" my focus by turing the focus knob in the direction that "pushes" the mirror forward (and usually that's counter-clockwise.)
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