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    grewal630's Avatar
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    Default 80mm mak and 80mm shot tube



    I wants to know the difference between sky watcher's 80mm Maksutov-Cassegrain (SK80MAKSP) and 80mm short tube(SK804AZ3 Achromatic Refractor).How are these two differ in terrestrial and astronomical observations.

  2. #2
    OleCuss's Avatar
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    Default

    First, they are (as I'm sure you noticed) a different optical design.

    The refractor (BK804AZ3) should give you better light-gathering ability and likely a wider field of view. Because it is a fast telescope it will be more demanding of the eyepieces - if you don't use very good (expensive) eyepieces you'll get distortion/softening near the edge of the field of view. Also, it won't do color just right, so you may get some false color around some objects (especially Moon and brighter planets).

    The Mak-Cas is a little trickier. I couldn't find that particular model, but again, the light-gathering of an 80mm Mak-Cas will be a little less than that of an 80mm refractor. It will almost certainly have a longer focal length and that will make it more forgiving of eyepieces (Plossls should work beautifully) and mean better contrast through the eyepiece.

    Focusing is likely to be a little smoother with the refractor.

    FWIW.

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    grewal630's Avatar
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    see these two at ...sky_watcher-india

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    Default

    Thank you for the link.

    No real change in my comments based on that link, however. But it might be interesting to note that the refractor comes with an erecting diagonal while the Mak-Cas does not. Also, the Mak-Cas comes with a bag included?

    FWIW

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    sxinias's Avatar
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    Hi,

    The 80 mm aperture of both telescopes is really too small for satisfactory deep space work. The SK1025AZ3 4 inch refractor will do a far better job ... for space and for terrestrial work. The SK1025AZ3 4 inch refractor will make a sweet starter telescope. The extra aperture is well worth the additional cost. Another excellent starter telescope but not suited for terrestrial viewing is the 6 inch SkyWatcher DOB.

    Between the two telescopes you mentioned. I would select the SK804AZ3 but for different reasons than previously stated. My reason is the SK804AZ3 comes with a nice azimuth mount and tripod while the SK80MAKSP comes with only a cheap cloth bag and a promise in the form of a note to use a camera tripod. Camera tripods and telescopes really don't work that well together. The vibration will be so severe that you probably will never be able to focus much less view anything.... a waste of your money. Either telescope will serve as a terrestrial telescope. The 80 mm refractor comes with an erecting diagonal for use as a terrestrial telescope. The 80mm MAK also has a diagonal and will have erect images.

    Both telescopes have an 80 mm (3 inch) aperture and the same light gathering and resolution capacity. The collimation of both is set at the factory and field adjustments are not needed. The refractor does not have a central mirror; thus, may have slightly better contrast. Chromatic aberration will be present with the 80 mm refractor and bright objects will have a purplish haze; this distracts some people but most ignore it. The MAK will have sharp images with no chromatic aberration.

    Again, if you can possibly afford it, the SK1025AZ3 4 inch refractor will be significantly better than either of the two telescopes you mentioned.

    The difference in focal ratios between the two 80mm telescopes is large but not that significant; f/5 refractor vs f/14 MAK. This large difference can be made up through eyepiece selection. For example, because of atmoshperic conditions, a magnification of around 80 to 100 times is the best that you can really expect from either telescope. You can get this using a 4 to 5 mm eyepiece with the 80 mm refractor or a 12mm eyepiece with the 80 mm MAK. The image in either telescope will be essentially the same size and brightness. The eye relief, thus ease of viewing, will favor the MAK because it will be using the longer focal length eyepiece. On the other end, a 32 mm eyepiece is about as large one that the 80 mm f/14 MAK can handle and a 20 mm about the largest one that the 80 mm f/5 refractor can handle. With a 32 mm eyepiece the 80 mm f/14 MAK will have an image size of 35x while the 80 mm f/5 refractor with a 20 mm eyepiece will have an image size of 20x; so there is not a significant difference on either end. This gives the 80 mm refractor the ability to show a larger area of the sky but with a smaller image. This is useful for many deep sky objects like M45, the Pleiades; however, the image will be small and difficult to see any details.
    SXINIAS

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