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Thread: Eyepiece Advice

  1. #1
    omarsultan's Avatar
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    Default Eyepiece Advice



    Hi:

    First time post on the forum.

    So, I recently started on a quest to buy a tracking mount for astrophotography and ended up getting a new mount and new telescope (the Celestron EdgeHD 800) to keep my stargazing wife happy as well. My wife has had a Meade EXT-70 for ages, so this ended up being a big step up for her.

    I am still a noob with the and one of the things that has me puzzled is what kinds of eyepieces to get. With her Meade, we never got anything beyond the kit eyepieces, but with the new telescope, I figure some new eyepieces are in order.

    I have done some web research and read all the sticky posts, but I am still not quite sure what focal lengths to get based on our viewing interests. My wife if primarily interested in checking things out within our solar system--primary the Moon, Jupiter and Saturn. I am more interested in checking our deep space objects like nebula.

    So, based on this info, a) any recommendations on which focal lengths we should start with and b) any particular brands you feel are well suited for viewing planets or DSOs?

    Thanks,

    Omar

  2. #2
    MitchAlsup's Avatar
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    Default

    You are going to want a lowest power EP, and for the C8 class scopes, this will be something like a 35mm Panoptic or a 31mm Nagler. This choice will require a 2" visual back. Both have the same field of view, but the higher power Nagler T5 has a darker background and objects are a little bigger. In a C8 this EP will provide at least 1 degree FoV and you can use it to locate objects before switching to higher power. Since this EP will be used for finding things, The bigger the FoV the better. If you skip the 2" visual back, you can get a 30-35mm Plössl that will fit in a 1.25" focuser.

    {You could go on the lookout for a 70mm EP in order to get a 7mm exit pupil, but don't bother. You could go after a 40-50mm 2" but in my opinion the Panoptics and Naglers are better, Explore Scientific should be on the list also.}

    From the 30-odd mm EP, you will want a spacing of 2/3rds so a 2X barlow will not create redundant focal lengths. Given a 30mm starting point: 30mm -> 20mm = 30*2/3 -> 13mm = 20mm*2/3

    Enter a 2X Barlow (or PowerMate). This device makes any EP deliver 2X the original magnification. So the 30mm becomes a 15mm, the 20mm becomes a 10mm. With such a Barlow, we now have access to the following focal lengths:: 32mm, 20mm, 16mm, 13mm, 10mm from 2 eyepieces and a Barlow.

    These will give you a versitile arrangement of EPs that fit most observing duties.

    At the higher power end of things, there are nights which will allow an EP with a FL as short as 6mm, other nights that won't permit more than 8mm. So for this end of the spectrum, and especialy if you are interested in planets, you may want to supliment the above kit with a few more planetary dedicated EPs.

    --------------------------------

    Apparent Field Of View:: I happen to like the 82dFoV EPs, and the more modern 100dFoV EPs over the 65-70dFoV and especialy over the older 45-50dFoV EPs. This comes with a cost ($$$ actually:i.e. pun intended). But if you plan carefully, and acreate one more EP every year, it does not take long to have a complete set of whatever EPs you want.

    A big apparent FoV makes finding things easier as things are less likely to drift out of the FoV simply because the FoV is bigger. It also gives an emersive effect as if you are not looking through a telescope, but are simply observing stuff directly with your eye.

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    kencrowder's Avatar
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    Default

    Based on your description of your experience, I suggest a Celestron (or equivalent) 8 mm to 24 mm zoom and a barlow. This will take you through the range of both scopes quite nicely. When you know what you like to do with your scopes, you will know which eps to look at for fixed fl.

    At the low mag end, I prefer to search with a finder scope. It doesn't collect as much light but is adequate for my use. I have a 35 mm ep and seldom use it.

    I have an 8 inch goto. The low mag is important for dobs and very large targets.

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    hi and welcome to the forums.
    thanks for joining us here at A.F.
    clear skies,

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    andy

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