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Old 29-10-2017, 08:30 AM
E_ri_k (Erik)
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Baader refractive index

Hey guys, I'm looking for the refractive index of Baader 36mm filters. Endless googling has left pretty much nothing.

Does anyone here have any information regarding this?

Erik
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Old 30-10-2017, 01:21 PM
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billdan (Bill)
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I can't give you an exact answer Erik, but I would imagine they would use BK7 crown glass with a refractive index of 1.52.
Unlikely they would use the more dense flint glass, which can range from 1.6 to 1.8.
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Old 30-10-2017, 02:15 PM
JA
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Quote:
Originally Posted by E_ri_k View Post
Hey guys, I'm looking for the refractive index of Baader 36mm filters. Endless googling has left pretty much nothing.

Does anyone here have any information regarding this?

Erik
Hello Erik,

If you have the filter itself you could calculate it, based on measurements of the critical angle for total internal reflection, using perhaps a laser, accurate angle measurement and the refractive index of air and the relationship that binds them together solved for the index of refraction of the glass that you want to know.

Best
JA
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Old 30-10-2017, 02:20 PM
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Merlin66 (Ken)
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99% sure itís BK7 glass thatís used.
Why do you need to know?
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Old 31-10-2017, 11:34 AM
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blink138 (Pat)
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there would be no reason for it to be anything other than hard crown glass (1.523) i would i think
pat
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Old 31-10-2017, 11:36 AM
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Merlin66 (Ken)
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I've contacted Baader and asked the specific question Re the filter material.
Erik - why the question??
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Old 31-10-2017, 05:08 PM
E_ri_k (Erik)
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Quote:
Originally Posted by JA View Post
Hello Erik,

If you have the filter itself you could calculate it, based on measurements of the critical angle for total internal reflection, using perhaps a laser, accurate angle measurement and the refractive index of air and the relationship that binds them together solved for the index of refraction of the glass that you want to know.

Best
JA
Thanks JA, a little beyond my capabilities I think but good to know!
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Originally Posted by Merlin66 View Post
99% sure itís BK7 glass thatís used.
Why do you need to know?
Thanks, oh just calculating extender lengths and taking into account optical filters.

Quote:
Originally Posted by blink138 View Post
there would be no reason for it to be anything other than hard crown glass (1.523) i would i think
pat
Thanks for the info Pat

Quote:
Originally Posted by Merlin66 View Post
I've contacted Baader and asked the specific question Re the filter material.
Erik - why the question??
Thank you, sorry for not getting in touch with you sooner, work had different ideas!
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Old 07-11-2017, 11:35 AM
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Merlin66 (Ken)
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Baader got back to me...
They use ďoptical glassĒ for their filters....not very informative!!
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Old 10-11-2017, 06:25 PM
E_ri_k (Erik)
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Quote:
Originally Posted by Merlin66 View Post
Baader got back to me...
They use ďoptical glassĒ for their filters....not very informative!!
Haha, no not very! Itís ok, I gathered 2 pieces of information I found online and compromised in the middle. Fingers crossed.

Thanks for your efforts.

Erik
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