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  1. #1
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    Default Accessories for 180mm Maksutov-Cassegrain?



    Hi all, I have an Orion 180mm Mak-Cass arriving soon. Orion doesn't recommend a 2" diagonal be used with the scope. What do you think? Would a 2" diagonal and 2" EPs help widen the FOV, or would this simply not work? I know that a scope with a focal length of 2700mm is naturally going to have a tight FOV, and that's fine, but I would like to take in a wider view sometimes if possible.
    Also, would an Antares 0.5x focal reducer work well to widen the FOV? I am only a visual observer at the moment, but may venture into astrophotography in the future.
    Paul
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  2. #2
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    Default

    If the manufacture does not recommend something that they also sell....

    One nice accessory I got from my MAK was a SCT thread adapter for the rear of the scope made by Baader. This lets me use my SCT accessories on my MAK, including my 0.63 SCT focal reducer (Hirsch). The focal reducer does widen the field of view making it possible to view DSOs that cover large areas of the sky. I'm sure that there are many optical reasons not to do this but I am not that particular. I don't use my MAK for photography due to its high focal ratio even with a focal reducer installed.
    SXINIAS

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  3. #3
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    Default

    Hi Paul
    i don't know if this helps its a Telescope Field Of View And Power Calculator
    Telescope Field Of View And Power Calculator
    mike
    "It's not that I'm so smart , it's just that I stay with problems longer ."

  4. #4
    47Tuc's Avatar
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    Default

    Thanks for that Mike, but I already have one here:

    N.A.A. Telescope Math Calculator

    Cheers.
    Paul
    36.85 S 174.57 E
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    Orion 180mm Maksutov-Cassegrain, 8" Richey-Chretien, HEQ5Pro mount
    Explore Scientific 30mm, Baader Hyperion 24mm, 17mm & 8mm, Pentax XW 10mm, TV 2x Barlow

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    Default

    Quote Originally Posted by mikeyfly View Post
    Hi Paul
    i don't know if this helps its a Telescope Field Of View And Power Calculator
    Telescope Field Of View And Power Calculator[/url]
    mike
    Quote Originally Posted by 47Tuc View Post
    Thanks for that Mike, but I already have one here:

    N.A.A. Telescope Math Calculator[/url]

    Cheers.
    These are useful links and new to me. Thanks!

  6. #6
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    Default

    Hi.

    I have an Orion Optics (UK) 200mm mak, 4000mm focal length. The field of view is always small, no matter what you do but I confess I use a 2" diagonal and ep's in it. The main exception would be a 13mm ethos which is as high as I normally go. Because of the long f/l, I normally use relatively long f/l ep's to keep the magnification reasonable and just find the 2" ep's more comfortable to use. To be honest, I am not sure they genuinely give a wider fov, and I am sure the manufacturer would say don't bother. Because I have other scopes which benefit from them, I choose to go that route.

    In my scope, a 28mm 82° UWAN gives x142 with a .57° fov. The only other ep which I could compare which I used to have was a 40mm 42° fov 1.25" which gave x100 and only 0.42°.

    A fairer comparison maybe my 22mm 2" nagler which gives x 181 and 0.45° vs a 24mm tv panoptic 1.25" giving x166 and only 0.4° fov.

    So there is something to be gained but I would say nothing too dramatic.

    To return to my earlier point, it's more about comfortable viewing and maybe better eye relief. If I only had the mak, I would probably keep with good quality 1.25" ep's.

    Stu

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  8. #7
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    Default

    Dont forget as you add a 2" diagonal you increase the scopes focal length.

    I have a 180 Mak and have it fitted with a Moonlite focuser and a 2" diagonal very often. Thats mostly for the ease of focusing as I found the image shift with thye scopes own focuser too much iof a headache.

    The nice thing with the 180 is the F ratio is so high that almost any EP will work well with it. Widefield targhets are a complete no-no (stuff like M45 for instance) but in fact there are only a handful of targets you cant fit in the FOV with something like a 25mm Plossl.

    The upside is the scope is an absolute planet killer. I use mine with UO orthos for lunar and its totally jaw dropping stuff.

    Also had the best views ever of Saturn with it.

    There is an argument that by adding to the focal length you are effctively reducing its aperture - I am not overly sure of this as the 2" fittings dont introduce vignetting unless you use super wide FOV EPs.
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  10. #8
    BigMakStutov's Avatar
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    Default

    Hi Astro Baby

    Can you explain how the 2" diagonal changes the focal length? I've not heard that before so would be interested to understand the technical explanation.

    Thanks

    Stu

 

 

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