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Porro or roof prism binoculars for astronomy?
https://popastro.com/forum/viewtopic.php?f=4&t=20107
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Author:  brian livesey [ Wed Sep 28, 2016 1:46 pm ]
Post subject:  Porro or roof prism binoculars for astronomy?

Which are the best of the two types of binoculars for astronomy? Porro prism binoculars used to be King, but what's the present state-of-play?
Has the traditional prismatic binocular been ousted by the less-bulky roof prism type? It used to be said that the optical construction of the porro prism glass was superior to the split roof prism type.

Author:  David Frydman [ Wed Sep 28, 2016 2:40 pm ]
Post subject:  Re: Porro or roof prism

Brian, it is a question of what is available.
In performance very little difference, although roofs are usually a bit more expensive.
Roofs may hold collimation better.
I you look at OVL site you will see both.

Regards,
David

Author:  brian livesey [ Thu Sep 29, 2016 3:36 pm ]
Post subject:  Re: Porro or roof prism binoculars for astronomy?

Thanks David. The fact that, as you say, roof prism bins are often more expensive than the traditional porro-type, might explain why retailers almost always seem to promote the latter type for astronomy.
Do you know when the roof prism binocular first came out? Was it originally a military glass?

Author:  David Frydman [ Thu Sep 29, 2016 4:31 pm ]
Post subject:  Re: Porro or roof prism binoculars for astronomy?

1870.
1899, 1905.
I think they tried to get over Porro prism patents.
Hensoldt founded 1849 were early makers. Dialyt 1905, very fine binoculars.
I think either civilian or military.

Originally less transmission and more difficult to make, but now up to 92% or more transmission.
Porro up to 96%.

Regards,
David

Author:  mike a feist [ Fri Sep 30, 2016 5:36 am ]
Post subject:  Re: Porro or roof prism binoculars for astronomy?

The cheaper sports optics roof prism binoculars / monoculars produce a smear-line or flare through bright objects which can be very annoying, and this can be especially irritating in binoculars if the flare in left and right eye are at a different angle! I believe that this flare is caused by reflection of the edge of the prism and that this requires a better-made and therefore more expensive prism/prisms. maf

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