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B filter question

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KevinBr's picture
Joined: 2014-01-01

I am returning to some ccd photometry after only some modest experience years ago.  I have been a frequent visual observer, especially of SN (when within visual range).

I have a partial set of Schuler JC filters.  I seem to have lost my Bu filter.  Is there a difference in actual data between the Schuler B, and a Bessel B or are they the same thing? 



B filters
HQA's picture
Joined: 2010-05-10

Hi Kevin,

The Schuler B and the Bessel B are identical.  They are both colored glass filters, formed out of stacking two different glass types.  There is a slight possible difference, in that Bessel gives two prescriptions, depending on the desired final thickness of the filter (I think 4mm and 5mm).  Schuler's is the same for whatever thickness that filter is.  If you get a filter from another vendor, or one of the Astrodon dielectric filters, there may be a thickness difference, which usually translates into a focus difference.  As long as you have an electronic focuser and program in the focus offsets between filters, it will be transparent to you.


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