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DSLR red channel transformed magnitudes

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arx
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DSLR red channel transformed magnitudes

I became interested in Roger Pieri’s paper on a synthetic filter for DSLR photometry JAAVSO Volume 40, 2012.

On page 835, Section 2, third paragraph Roger wrote "The DSLR R channel is too far from the Cousins Rc to be faithfully transformed."

I was interested to know if the author meant that this comment should apply generally, or specifically to considerations of the synthetic filter described in the paper.

I tried to reach him a week ago but without success, hence the posting here.

The reason for the above is that, in my experience, DSLR red channel transformed magnitudes are at least as accurate as green channel transformed magnitudes for bright (5th to 7th magnitude in V) standard stars from the E Regions (Menzies J.W. et. al. 1989, S. Afr. Astron. Obs. Circ. 13, 1) with B-V colour indices between 0.3 and 1.5 approximately. Phil Sullivan (SPP) has seen the graphs supporting this statement.

Can anyone comment?

Roy

AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484