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Roof And Porro diffrence

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#1 Guest_**DONOTDELETE**_*

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Posted 28 July 2004 - 06:01 PM

Sorry if this has been asked befor i searched for a while for my answer but i dont have time to sit and read all over for my answer..

so what is the diffrence between roof and porro..and which would be better for astro viewing in the night sky..

one other question why are Fujinon binos so expensive whats the deal.. they must kick butt...

#2 jack savard

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Posted 28 July 2004 - 06:51 PM

about your head

may be it a GOAOUL like in the door of star serie

ha ha ha


I am not from here like we said on my star
:tonofbricks:

#3 Craig Simmons

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Posted 28 July 2004 - 08:15 PM

A link to some information.

http://www.telescope...626&CCNavIDs=19,20,82

#4 BillC

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Posted 29 July 2004 - 03:24 PM

so what is the diffrence between roof and porro..and which would be better for astro viewing in the night sky..

one other question why are Fujinon binos so expensive whats the deal.. they must kick butt...


a) The difference is mentioned in any number of places on the net. The BENEFIT in Porro Prisms for astronomy may not be.

Porro prisms do not require ant-phase shifting coatings to work well, they are much less expensive to make and test, and they do not cause bright stars and planets to spike, as do some roof prism models.

b) Not only do the Fujinon's (MT / FMT Series) "kick butt," they will continue to kick butt long after you have become fertilizer.

Cheers,

Bill Cook

#5 craig_oz_land

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Posted 30 July 2004 - 02:18 AM

Hi Bill,

I woukld like to know why you rate the Fujinon MT and FMT so highly, or is it because the reference was made to Fujis in the first place.

Regards, Craig.

#6 BillC

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Posted 30 July 2004 - 12:26 PM

Hi Bill,

I woukld like to know why you rate the Fujinon MT and FMT so highly, or is it because the reference was made to Fujis in the first place.

Regards, Craig.


After you have been INSIDE several thousand binoculars, and worked with two or three generations of corporate leaders, you get some idea of how to seperate the caviar from the *bleep*.

To give you a list of reasons why I like the big Fujinons (and their Nikon cousins) would take more time than I will have for the next few days.

Cheers,

Bill

#7 Guest_**DONOTDELETE**_*

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Posted 02 August 2004 - 01:53 AM

Holger Merlitz reviews some of the smaller Fujinons on his excellent site. He too reckons they are first rate.

There is another advantage of porros, namely greater light transmission. The reflecting surfaces of porro prisms use total internal reflection (TIR), a phenomenon that occurs when the angle of incidence is in a certain range. Basically this means that 100% of the light is reflected without the need for coatings. Roof prisms do not use TIR and hence need expensive mirror coatings. These always lose some light. I suspect that the Leica BN range transmit no more than ~80% of the incident light (an educated guess but not based on actual measurements: it would be interesting to see if I am right). Cheaper roofs might even transmit as little as 50% of the light. I once compared a Pentax 8x42 DCF WP (made ~1997) to a cheap Nikon 8x42 Egret. The former gave a sifnificantly darker image.

#8 BillC

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Posted 02 August 2004 - 11:46 AM

Holger Merlitz reviews some of the smaller Fujinons on his excellent site. He too reckons they are first rate.


So far, each of my comments concerning Fujinon binoculars has addressed only the big Fujis. I do not offer my name as an endorsement for any of their third-party products. They may be very good--and usually are. But . . .

Cheers,

Bill


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