Affiliation
American Association of Variable Star Observers (AAVSO)
Wed, 11/18/2020 - 19:13

Hi, Currently I'm using SLOAN g´r´i´ filters. Which filter shoudl I select in variable star ploter to proper do the photometry ?.

Thanks!

Affiliation
American Association of Variable Star Observers (AAVSO)

Hello Martin--

I did defer to the experts on this question, but I understand the broad answer is that there is no good answer to that question. You can select stars with colors that match the target variable using VSP, but you will need to look up Sloan photometry on-line for the comp stars you have chosen. I invite the experts to weigh in.

Richard

Affiliation
American Association of Variable Star Observers (AAVSO)

You could make your own Sloan comp sequences using APASS data and report the Sloan magnitudes to the AID.    

I would start with the VSP chart for your target that matches the FOV of your system.  Then use the APASS query  ( https://www.aavso.org/download-apass-data ) to identify the AAVSO comps shown in the VSP chart.  Use the APASS Sloan magnitudes for the AAVSO comp stars.

Phil

Affiliation
American Association of Variable Star Observers (AAVSO)

Thanks Richard and Phil. Understood. One more: Would be really useful to report SLOAN photometry to AID ? I'm asking because typically the aavso alerts/campaigns use to request Johnson photometric system measures rather than Sloan.

Affiliation
American Association of Variable Star Observers (AAVSO)

Jose´,

Yours is a timely question.  Access to Johnson-Cousins filters for amateurs is getting difficult.  Some traditional sources have decreased production, resulting in long back order waits.  Some have stopped producing J-C filters entirerly, in favor of Sloans.   Others have switched to offering "Bessell" filters which are neither Bessell nor J-C.  It seems possible we all may have to switch to Sloan filters sooner or later. 

I think Sloan data would be useful and welcomed in the AID for the usual long term surveillance practiced by many AAVSO observers. 

As for Pro-Am Special Alert projects and observing campaigns, we will have to hear from the Pro's.

Phil

Affiliation
American Association of Variable Star Observers (AAVSO)

Thanks for your response. Actually I've just renewed my CCD+filters and decided to "invest" in the future (i.e. Sloans), maybe to early eventhough Sloans has been around for some years. I still have the Johnsons with my venerable ST10 CCD just repaired and back fully operative. I might be rolling back if that makes sense at the current stage of development. JL.