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binoviewer ep upgrade


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Can any fellow bv user give any advice on any future ep purchases, I have got 2x wo20mm ep's, a 2x Barlow and a 1.6x corrector. My range of mags with said ep's are 12.5mm, 10mm and 5.5mm. In an ideal world I would get 2 televue plossls but I'm not sure what mag ep's to go for, I'm not sure I could get away with 30mm ep's in the bv. Any ep recommendations would be most welcome.

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I would never go back to Cyclops mode, if someone offered me an ethos for my bv's I'd turn them down.

So I take it you like them :smiley: I'd love to try some, anything that adds to the experience of observing is worthwhile in my book.

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Earl had a couple of TV plossls for sale a few weeks ago but the ad has since expired; not sure if he ever sold them or not and I can't remember what they were, but it might be worth a pm??

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I have a couple of pairs of the TV plossls and they are nice for binoviewing without having to spend a fortune. There are better options but the cost to purchase will increase alot more than the performance gains.

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It all depends on the model of binoviewer and the size of the prism.

Most sub-£150 binoviewers have prisms limited to about 20mm clear aperture, which is pretty restrictive. You have to pay quite a lot for 26mm clear aperture binoviewers.

Adding a "1.6x" barlow on the end of the binoviewer to get focus in a lot of scopes, actually acts at about 3x and you're in high magnification territory! I think there are better barlowing systems that don't give such high magnification.

I have a Denkmeier binoviewer, which is lovely as I can use 32mm plossls without vignetting, and only multiplies 1.4x with the extra optic.

Andrew

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Vignetting is darkening at the edges of the FOV. Basically your field of view is restricted and you see a dark ring at the edge.

32mm plossls will certainly show vignetting.

Astigmatism often appears if an optic is under uneven pressure for some reason, but can also show in a poor optic. It often shows stars as radial lines on one side of focus, and circumferencial lines on the other. (or ovals that change axis through focus) The in-focus image is generally blurred, and stars can look like little crosses.

Andrew

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Thx Andrew, the 20mm ep's I use have 66 degree fov, I can just about get the whole moon in, it would benice if I could get the moon with some background stars too, I tried sw 25mm plossls and got a little less magnification but the fov was smaller, so still no background sky with the moon. Was hoping I could get away with 2 30mm ep's but it looks like I will have to do with what I already have.

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Interesting write-up, but one part made me chuckle, " you may get a decent view of Saturn, Jupiter as long as you don't push the power too high" with a 2x Barlow and the 1.6x nosepiece using the 20mm ep's I calculate this to be about 5.5mm giving me about 216x magnification, the views I've had of Saturn, Jupiter and mars have been nothing short of spectacular. If all goes to plan and I get my hands on a pair of 15mm televue plossls then I expect the views could be even better

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