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    claycarr's Avatar
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    Default Beginner - Need advice on eye pieces and accessories



    I just purchased this telescope on craigslist:

    Celestron Advanced Series C8-SGT (XLT) Computerized Telescope - Discontinued

    It came with an Diagonal Mirror and a 1.25" 25mm eyepiece. What are you thoughts on upgrading to a 2"Diagonal Mirror:

    Amazon.com : Celestron 2-Inch XLT Diagonal Mirror (for SCT Telescope) : Camera & Photo

    And getting 2" eye pieces: Amazon.com : Celestron 93434 Luminos 23mm Eyepiece (Silver/Black) : Telescope Eyepieces : Camera & Photo

    The problem I see is that the 2" only comes with limited MM ranges and its my understanding the lower the MM number the more 'zoom' I will get, and its what I want. Should I stay with the 1.25" so I can get more Luminos eye pieces MM ranges? Is Luminos the highest quality for Celestron? What is the hierarchy of their eyepieces based on quality?

    My ultimate goal is to do astrophotography using my Canon 6d (he included the adapter ring for connection). I also want to use it for my family. What is the best way to broadcast what we are seeing thru the telescope besides using live view on camera? If the eyepieces give you zoom, is my telescope static in regards to the zoom when taking photos with the camera attached?

    How did this user from amazon reviews get the mirror and camera setup, is this a simple accessory? http://www.amazon.com/Celestron-S-GT...rds=C8-SGT+%28

    Lots of questions. Thank you.

  2. #2
    KathyNS's Avatar
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    Default Re: Beginner - Need advice on eye pieces and accessories

    Welcome to the forum, and congratulations on the new (to you) scope.

    A 2" diagonal will give you access to wider fields of view. That is all it does. Wide fields of view are only relevant to wide angle eyepieces - those with long focal lengths (the mm numbers) and those with wide apparent fields of view. A high magnification eyepiece is deliberately limiting the field of view in order to give you the high magnification, so the 2" diagonal is of no benefit. That is why you won't find short focal length eyepieces made in the 2" size.

    You can still use 1.25" eyepieces in a 2" diagonal, because it will come with an adapter.

    When doing astrophotography, the telescope becomes a giant telephoto lens. Your C8 will act like a 2000mm camera lens, and will have the image scale of a 2000mm lens. As with all camera lenses, you have to change the focal length in order to change the image scale. You can do that by using a barlow to increase the effective focal length or a focal reducer to decrease it.

    To broadcast an image from the camera, you need to use a video camera. A DSLR in video mode or live view mode will do, as will a webcam or astro-specific video camera.

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    Default Re: Beginner - Need advice on eye pieces and accessories

    Keith just answered your question BUT most of us do buy a 2 inch Diagonal ..

    I use a 2" Denkemier P/S S1 diagonal ...which sure is not cheap BUT it does contain a built in 2x Barlow as well as a focal reducer so it functions as 3 separate items )

    Every one of my 26 mm and lower power (higher mm numbers) are 2 inch eyepieces because I want a larger FOV when viewing under low power...

    All my higher Power eyepieces ( 8 thru 25 mm) are 1.25 inch eyepieces because frankly I do not need ..nor want..large Fields of view when viewing under high power...

    8 mm is about the highest power I find I ever use and 35 seems to be the lowest power . I could go all night with just my 27 31 and 35 mm because I am into DSO observing...

    Bob G
    CPC1100 housed in a slotted domed observatory (Exploradome) 4 and 5 inch refractors for use from the lawn, a 8" Sct (NS 8i) for star parties...
    I Hate the winter so I use heated Motorcycle clothing to stay warm while observing in winter
    Retired, also have 2 other hobbies
    1. tinker with older Corvettes (6 in garage)
    2. make a heck of a lot of sawdust in my wood shop.

 

 

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