Peter,

The photometry I'm using for the 12P lightcurve is unfiltered referenced
to Gaia G so your luminance filter will be fine. The key thing is to use
a photometic aperture radius near to 9 arcsec.

Nick.

On 15/01/2024 10:17, Peter Tickner - peter.tickner1472 at btinternet.com
(via baa-comet list) wrote:
> Hello Nick
>
> Like almost everyone in the UK and nearby countries I've had nothing but cloud at the times I could observe 12P.   I have however taken the opportunity of the enforced break to acquire a mono camera I can use with my 14inch SCT for comet observation (I admit it was mainly bought with occultation work in mind) - this may enable me to be able to measure things with Astrometrica more easily.
>
> I don't have any Sloan filters though - what would be the recommended best alternative?    I can image with no filter, with a luminance/IR cut or a plain red filter.   Is there a preference?
>
> Kind regards,
>
> Peter