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Some Technical Infos about Binoviewers

Started by apmtelescopes, 02/24/2003 09:08AM
Posted 02/24/2003 09:08AM Opening Post
This morning I have had the chance to talk with the old Masteroptician in Eastgermany who producing the BW optik Binoviewers and my questions he answered as follow

1, Question: what is better Bak4 or BK 7?
Answere: Bak 4 is used to compensate some spherical aberrations, but prism made without real spherical aberration better using BK 7, because that BK 7 glas is way better in homogeneity than Bak4 and can be much better polished

2, Question. what kind of coating is used in BW optic Binoviewers
answere: Braodband spectral coating with 99.5 5 transmission per surface over the visual spectral range

3, Questions: why one side is in most dimmers than on other side and why some are more similar on each side ?
answere: standart nonobstructed systems with best coatings show and must show a bit diffrenc ein brightness due diffrent long optical path. Binoviewers showing equal brightness on both sides using a design with 30~50% obstruction at one side . Some technics excist to make a binoviewer looking equal bright on each side, but it requires very special ultraexpensive coatings and such binoviewers going for not less than $ 2,000 worldwide on the market

I hope this info helps a bit

best wishes

Markus

clear skies

Markus Ludes
APM-Telescopes/Germany
Posted 02/24/2003 12:07PM #1