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Powermates and. Fracs


cyborg421

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I've just got a 4" frac and have a range of TV eyepieces including the 31mm T5. I was wondering if anyone has any experience of using a 2x 2" Powermate and a 2" diagonal combined with a heavy eyepiece such of the 31mm although some of my other TVs are almost as heavy.

Thanks for any replies.

Simon

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I have tried using the 2" 2x Powermate with the 31mm Nagler and Explore Scientific 20mm 100 degree eyepieces. Optically it works extremely well but the sheer size and weight of the combinations were more than I was comfortable with. The 2x PM adds over 1lb in itself.

post-118-0-46064400-1386531336_thumb.jpg

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Hiya Simon,

Strangely just today I have been pondering about the very same thing as I too have concerns about the weight / additional length :shocked:

I was also looking at the TV " Big Barlow " as they are not as heavy but the description states it is mainly for Newts and do not recommend them with scopes that use diagonals :smiley:

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I have tried using the 2" 2x Powermate with the 31mm Nagler and Explore Scientific 20mm 100 degree eyepieces. Optically it works extremely well but the sheer size and weight of the combinations were more than I was comfortable with. The 2x PM adds over 1lb in itself.

You've got a tower there, John. :)

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As the magnification multiplier of Powermates and other four element tele-centric designs are virtually unaffected by the distance to the eyepiece, could you not insert it ahead of the diagonal in the telescope focuser tube?

It would depend on how much in-focus you have to play with, but it will result in a shorter Eyepiece with less turning moment applied to make things come loose.

Russell

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As the magnification multiplier of Powermates and other four element tele-centric designs are virtually unaffected by the distance to the eyepiece, could you not insert it ahead of the diagonal in the telescope focuser tube?

It would depend on how much in-focus you have to play with, but it will result in a shorter Eyepiece with less turning moment applied to make things come loose.

Russell

I was thinking about this. I do have an 8cm extension rube before the diagonal. I was wondering if I could swap the extension tube for the Powermate as this would create less moment on the diagonal. I have a 3" Starlight focuser so I don't think weight is an issue, just the turung force and security.

Simon

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I considered the same thing not that long ago until I saw Johns non-leaning tower of Pisa. Decided on dedicated FL EP's instead. As good and strong a focuser I may have been putting the contraption in, ultimately it was myself I didn't really trust!

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Do they make a 1.5 Powermate ?

No. Antares do a very good 1.6x 2" barlow though. While it does alter the focus position and eye relief, as barlows do, it works really well with the Ethos eyepieces and it's shorter and lighter than a Powermate.

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Is Russell's idea of putting the Powermate before the diagonal a good one?

Does anyone do this?

It would seem to solve the "tower" problem.

Simon

I've not tried it but I've read somewhere (probably Cloudnights) that, while it does not affect the magnification boost, some scopes will have difficulty in bringing the combination to focus so I guess the focal plane is altered.

My Powermate 2" 2x (and I think all are like this) did not have a safety undercut in the barrel so I think I'd have some nervousness about hanging a 2" diagonal and a 1kg eyepiece off it.

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My Powermate 2" 2x (and I think all are like this) did not have a safety undercut in the barrel so I think I'd have some nervousness about hanging a 2" diagonal and a 1kg eyepiece off it.

Very scary thought if that were to happen :shocked: makes me cringe just thinking about it :smiley:

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I've not tried it but I've read somewhere (probably Cloudnights) that, while it does not affect the magnification boost, some scopes will have difficulty in bringing the combination to focus so I guess the focal plane is altered.

My Powermate 2" 2x (and I think all are like this) did not have a safety undercut in the barrel so I think I'd have some nervousness about hanging a 2" diagonal and a 1kg eyepiece off it.

I was thinking about this and couldn't convince myself that the extra inward travel inserting a PM/FE/etc requires when inserted after the diagonal, should be any different because it is inserted before the diagonal. I was about to try it out when I remembered that my diagonal is 2", whilst my FE is 2". Drat,

Russell

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