FS: 2 inch 99% reflectivity dielectric version star diagonal

denebman · Post by **denebman** » Fri Sep 16, 2005 10:37 am

This is my first introduction of homemade brand new 2" dielectric star diagonal.

The dielectric version star diagonal is made from 10 mm thick fully annealed BK7 glass. The dielectric coating was done by a research inistitute of Chinese Science Academy. The OTA adapter tube is made of stainless steel and the eyepiece tube of aluminium alloy. The mirror cell is crafted from one-piece aluminium block to insure permanent alignment. Other specs. include:

1. Surface flatness: 0.053 lambda, rms: 0.010 lambda
2. Reflectivity: >99% from 400 to 730 nm
3. Dielectric coating: 24*4=96 layers of transition metal oxide plus SiO2
4. All compression rings are made of more durable phosphorous bronze
5. True clear aperture: 47.25 mm circle

Attached below is the test report on a randomly chosen piece out of a ten-piece batch. More comparison with Televue 2" everbrite diagonal will be ready soon.

My price is S$ 199 each, I've got FIVE pieces this time (one reserved already).

Interested party pls sms me at 93626105.

denebman · Post by **denebman** » Fri Sep 16, 2005 10:45 am

The first one is the interferometer results, the second is reflectivity test. Please note that the reflectivity test is destructive, the test sample was abandoned.

denebman · Post by **denebman** » Fri Sep 16, 2005 10:46 am

reflectivity results

ariefm71 · Post by **ariefm71** » Fri Sep 16, 2005 8:59 pm

an article why dielectric diagonals are better than non-dielectric ones: http://www.astrosurf.org/lombry/reports ... agonal.htm

SingAstro