Substitute a Sloan g' filter for a Johnson B filter ?

American Association of Variable Star Observers (AAVSO)
Mon, 06/20/2016 - 01:36

Hi Arne,

At one time you'd recommended that I could use a Sloan i' filter, reporting it as an Ic filter then putting a comment in: Actual filter used was Sloan i'.   I 
have done tranforms based on Johnson V and Ic(really Sloan i') and successfully submitted those observations.  Thanks for that guidance.

A related question would be; do you think I could do essentially the same thing but substituting Sloan g' for Johnson B?  The response curves for Sloan g' and Johnson B look pretty close except that Sloan g' cuts off the shortest 50nm or so (350-400nm) of the Johnson Blue.  With the advantage of sharper cutoffs, the Astrodon Sloan g' (Gen 2) also excludes sky glow at 557.7 nm.

I'm just trying to avoid purchasing a $200 Johnson B filter then maybe 6 months to a year later purchasing a $200 Sloan g' when AAVSO fully adopts the Sloan standard.


John Ott