[Aavso-photometry] Mixing filter brands and transformations

[arne]

Gerald Bokowy wrote:
> I just changed from a manual filter wheel to one that is motorized.
> 
>  While doing so I noticed that my V filter has a bad case of crud.
> 
> All of my current bvri filters are Schuler.
> 
> I am considering getting a custom scientific V filter to replace the
> corroded one.
> 
> Will mixing this new V filter with the anti reflective coatings and
> different thickness, with the remainder of my schuler filters.
> 
> cause problems when doing transformations?
> 
> I intend to slowly move to all custom scientific filters in time but not
> immediately.
> 
>  
> 
> Do I 
> 
> 1)      Replace the crud coated schulerV filter with a new one and wait to
> buy a full set in the future.
> 
> 2)      Or slowly convert from schuler to custom scientic as funds are
> available one filter at a time
> 
>  
> 
> Does everyone use a matched set of filters? Does it matter beyond focusing
> differences?
> 
> My biggest concern is will there be any systematic problems for color
> transforms using a mixed set
> 
There are systematic trends for *any* filter set (which is the
whole purpose of transformation), so it really
doesn't matter whether you mix and match filters.  Your coefficients
will be somewhat different than with Schuler.  You will
probably have a focus difference, depending on the thickness
of the filters.  I'd do #2, buy the custom scientific V filter
for now, and convert the others as funds permit.  The V filter is
the one you will use most of the time anyway, so having it be
the best quality can't hurt.
Arne