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Thread: 30mm eyepiece recommendation 16" lightbridge

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    Default 30mm eyepiece recommendation 16" lightbridge



    Hi all,
    I am having trouble selecting a 30 to 40mm 60 degree plus eyepiece for deep sky. At f/4.5 I expect coma towards the edge but anything would be better than the 26mm 2" supplied with the scope. I am leaning towards skywatcher panaview 32 70 degree. Baader hyperion is another choice but opinion differs between feedback/reviews. Meade 5000 get good reviews. How does SkyWatcher 32mm 70° Wide Angle Long Eye Relief Eyepiece compare with the others. Please don't recommend more expensive eyepieces as they are not close to my budget. Just feedback please about the mentioned eyepieces, I can live with edge coma. Thanks in advance for your thoughts

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    Default Re: 30mm eyepiece recommendation 16" lightbridge

    I'm not sure we can help you all that much.

    There are not a whole lot of us who have F/4.5 Newtonian reflectors so we won't have a large base of people who have tried those particular eyepieces with a sufficiently similar scope. There are a fair number who have F/4.7 10" Dobsonians and they will have experiences which are at least relevant.

    The problem is that no one will know what works for you.

    I have the fairly fast Orion XX12g. Good scope but I got a 35mm Panoptic when I first got it since I knew the included eyepiece was not going to control the coma. I've since gotten a number of Explore Scientific 100° eyepieces and the XX12g doesn't get used with anything else.

    Some people have high tolerance for the coma and I have little tolerance. I probably couldn't tolerate your scope without getting a Paracorr for the thing.

    And the above is where the problem is. What one person will find to be quite good might drive you insane. What might drive me nuts might be perceived by you as very pleasurable.

    My best hope if I were in your situation is to go observing with your local astronomy club and let it be known that you are trying to learn what eyepiece(s) will work for you with that telescope. There is a good chance people will offer to let you try out their eyepieces in your scope and you will get an idea what works for you.

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    Default Re: 30mm eyepiece recommendation 16" lightbridge

    The thing that worries me is the minimum magnification that your scope can do without your exit pupil becoming smaller than 7mm : 16" X 3.6 = 57.6. so your minimum limit is about 58 magnification. With 40mm eyepiece your magnification is less (1829/40 = 45.72). Now we have not even considered problems with the central obstruction with a low focal ratio of 4.5. The 30mm
    looks better because it gives you a 60 magnification and lets you stay in the safe margin.
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    Default Re: 30mm eyepiece recommendation 16" lightbridge

    Quote Originally Posted by Piet Le Roux View Post
    The thing that worries me is the minimum magnification that your scope can do without your exit pupil becoming smaller than 7mm : 16" X 3.6 = 57.6. so your minimum limit is about 58 magnification. With 40mm eyepiece your magnification is less (1829/40 = 45.72). Now we have not even considered problems with the central obstruction with a low focal ratio of 4.5. The 30mm
    looks better because it gives you a 60 magnification and lets you stay in the safe margin.
    Sorry I said "smaller than 7mm" it should be bigger than 7mm.

    my limit on the 15" Obsession is about 54 magnification and the 27mm Panoptic does a great job for wide views for me.
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    Default Re: 30mm eyepiece recommendation 16" lightbridge

    For basic observing I don't mind the GSO Superview 30mm Erfle. This is an economical 2" barrel eyepiece that originally came with my Zhumell Z10. While there is a bit of coma at the edges of the field of view I don't mind it. Slightly worse in my 18" scope because it is even faster in terms of f-ratio than my Z10, but I still use it on occasion in that scope. Works great and is coma free in my 6" refractor. I consider it a good all-around low power eyepiece. For example, I used it to observe all 110 of the Messier objects.

    Here's a link to an outlet that has it for sale for $70.

    https://agenaastro.com/gso-30mm-superview-eyepiece.html
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    Default Re: 30mm eyepiece recommendation 16" lightbridge

    Another formula that is used by the makers of Obsession is this one:
    exit pupil = focal length of eyepiece / F-number
    in the case of my 27mm its 27mm/4.5 = 6mm. They also recommend a exit pupil of 4MM for pleasing viewing.
    At my age 6mm is what my pupil size would be so there's no point for me to go bigger than the 27mm. One of the downsides of a big dobsonian with a low F-number is the coma effect ( as mentioned by Michael) and the wider you go the more apparent it becomes.
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    Default Re: 30mm eyepiece recommendation 16" lightbridge

    You really need to dertermine your max dark adapted eye pupil before deciding on an EP. the 30mm produces a 6.66 mm exit pupil in your scope. If you’re not that young you may find this alreday exceeds your max pupil. Mine has been measured at 6.1mm so I would never own an EP above 27mm since my scope is f/4.6
    if you don't routinely observe in truely dark skies your max exit pupil will be evn smaller ...

    if the exit pupil of your EP is larger than your eye exit pupil it won’t matter what quality the EP is ..,.
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    Default Re: 30mm eyepiece recommendation 16" lightbridge

    Thanks for the replies. I have been into astronomy for near on 50 yrs. I have had this scope for around 12 years and used the same eyepieces I had for my previous scope, a 10" f6. 30mm plossl, 10mm plossl and 7.5mm plossl. I also have a 1.8x televue barlow, all 30+ years old. I was never satisfied with the eye relief with the shorter fl plossls and excellent seeing near the coast is rare, so magnification is not useful. However I am lucky enough to have fairly dark skys so dso can be quite spectacular. I was after a good low magnification eyepiece with wider fov. I have purchased some starguider eyepieces for moon and planets, 18mm and 12 mm. These are enormously superior to my old plossls and even barlowed to 200 to 250x show some amazing views of Jupiter and Saturn. Thats with average seeing and un acclimatized primary. I am aware that the exit pupil @ 30mm might be testing my eyes, but the clarity and brightness of my old plossl tell me that I am still getting plenty of light. As stated, I am mainly after the wide fov and better optics. I'm sure eyepieces have improved over the last 30yrs, better coatings, less reflections etc.. with the advantage of 2" focusers. The meade 26mm is bright and wide but seagulls not far out from the centre. None in my 30mm plossl by the way. I might give the 30mm GSO sv a go. Once again thanks for your views.

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    Default Re: 30mm eyepiece recommendation 16" lightbridge

    My bad, 180x with 18mm barlowed, 270x with 12mm barlowed

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    Default Re: 30mm eyepiece recommendation 16" lightbridge

    Quote Originally Posted by Fleegal View Post
    I might give the 30mm GSO sv a go. Once again thanks for your views.
    Its a pretty safe choice. I used mine in a F5 dob for over a year and it was the last eyepiece I ended up replacing. I still use it from time to time.
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