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PostPosted: Wed Sep 28, 2016 1:46 pm 
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Location: Lancashire
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.

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Last edited by brian livesey on Thu Sep 29, 2016 3:30 pm, edited 1 time in total.

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 Post subject: Re: Porro or roof prism
PostPosted: Wed Sep 28, 2016 2:40 pm 
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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.

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David


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PostPosted: Thu Sep 29, 2016 3:36 pm 
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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?

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PostPosted: Thu Sep 29, 2016 4:31 pm 
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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%.

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David


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PostPosted: Fri Sep 30, 2016 5:36 am 
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Location: Portslade, Sussex Lat 50deg 51min Long 0deg 13mins West
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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