American Association of Variable Star Observers (AAVSO)
Tue, 11/11/2014 - 20:06


Meade ETX 125 +30mm(x63) EP.; 1000 Oaks film filter show a solar feature labeled AR2201 (right side)

But I am unable to see anything (no spot or discolaration) at that location?

Is is just not visable in white light?




white light vs Boulder active regions

 Hi David, uses the Boulder group designation for the Active Regions.  These AR numbers come from the Boulder observatory, and the USAF ISOON observatories and a few others scattered around the world. They are made up of H -alpha and Ca II spectral lines.  So there will be AR numbers for groups that you wont see with a white light filter. They may evolve into visible groups and sunspots, but not always.  Only record what you can see thinking in the Zurich classification scheme.  


attached is a short description of the Boulder method