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Thread: Max Magnfication for Lunar Observing

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    Default Max Magnfication for Lunar Observing



    Hi,
    I have a 10" Dob with a focal length of 1200mm and a focal ratio of f/4.7. With a 6.7mm eyepiece I get a magnification of 179x which is great for observing the moon, but I would like to get closer. The question is, will I be able to achieve focus with a 2x Barlow (x358) or even a 3x Barlow (x537).
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    Roger
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    Default Re: Max Magnfication for Lunar Observing

    Moon takes high magnifications extremely well. I was able to push productively to x425 with 8" SCT under excellent seeing. The difference of cause that my 8" SCT is F10 scope, so your F4.7 DOB may not be as sharp at such high magnification. But there is no harm in trying .
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    Default Re: Max Magnfication for Lunar Observing

    I routinely use 255x with my 10" Orion dob on the moon But thats about tops for my location.
    Adlartok...Chris

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    Default Re: Max Magnfication for Lunar Observing

    I have a 10" dob as well. Give your 6.7mm a try with a 2X barlow. I've squeezed out 534X with good to excellent seeing using a 4.7mm teamed with a 2X Focal Extender. Must have checked the label on a the EP a dozen times that night to make sure it was actually my 4.7mm EP. That was back in April when the nights were cooler and the air more stable. Right now I can push to 284X or slightly better if I catch the moon high enough. Lately, beyond that the image starts to boil.
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    Default Re: Max Magnfication for Lunar Observing

    You can definitely try to push your scope with a 2x Barlow. I think the max useful magnificacion is the double of your aperture in mm so for you it will be something like x508. With the 3X you are exceeding those limits so you may have a slightly issue with focusing.
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    Default Re: Max Magnfication for Lunar Observing

    Thanks for the input. I'm thinking the 2x might work. I have 4 ES 82° EPs - 6.7mm, 11mm, 18mm & 30mm. A 2x Barlow would give me 3.35mm, 5.5mm, 6.7mm, 9mm, 11mm, 15mm, 18mm & 30mm. Looks like a pretty good spread. Problem is of course, I'll have to get one with a 2"-1.25" adaptor, as I have both 2" and 1.25" barrels. ES make one, but it's $200. On the bright side, it's a Focal Extender which has added advantages, and I would be pretty much future proofed.
    Roger
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    Default Re: Max Magnfication for Lunar Observing

    Rick, I've just had a look at your equipment list. Do you have the focal extender with the adaptor? You probably don't need it as you have the full spread, but I'm interested to know your thoughts on which ES extender you would get if you had my kit.
    Roger
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    Default Re: Max Magnfication for Lunar Observing

    I have a 3mm Zhumell Planetary eyepiece that works fine on the moon in my 10" Dob. You'll have no issues with your 2x Barlow.
    John (Urban Astronomer)
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    Default Re: Max Magnfication for Lunar Observing

    Quote Originally Posted by rogercorbett View Post
    Thanks for the input. I'm thinking the 2x might work. I have 4 ES 82° EPs - 6.7mm, 11mm, 18mm & 30mm. A 2x Barlow would give me 3.35mm, 5.5mm, 6.7mm, 9mm, 11mm, 15mm, 18mm & 30mm. Looks like a pretty good spread. Problem is of course, I'll have to get one with a 2"-1.25" adaptor, as I have both 2" and 1.25" barrels. ES make one, but it's $200. On the bright side, it's a Focal Extender which has added advantages, and I would be pretty much future proofed.
    If you can live without 15mm I highly recommend TeleVue 2x 1.25" barlow. They are on sale now brand new for $100. My ES 6.7mm barlows nicely with it.

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    Default Re: Max Magnfication for Lunar Observing

    Quote Originally Posted by Lowjiber View Post
    I have a 3mm Zhumell Planetary eyepiece that works fine on the moon in my 10" Dob. You'll have no issues with your 2x Barlow.
    Good to hear! Many thanks.
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    Roger
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