Skip to main content

Active Region 2738

3 posts / 0 new
Last post
tst
Active Region 2738

Hi All, 

I had a question regarding AR2738 currently crossing the face of the sun. I've noticed that the umbra appears to have split in two (light bridge?), and was wondering if it should be counted as two spots?

My observations were made in white light with a 6" F/8 Newtonian equipped with a Baader solar filter and continuum filter at the eyepiece  magnification was 50X.  

Thanks in advance. 

Steve

HRHA
HRHA's picture
Active Region 2738

Hi Steve, 

Good question. There could be a debate about that. I would count them as two spots, but other folks might disagree.  Here are a few guide lines from Frederic Cletter (SILSO). 

  • Umbral splitting:
    • –  Each umbra in common penumbra is counted as a separate spot (Wolfer rule)
    • –  Two umbrae considered as split only if separated by a complete light bridge
    • –  Prone to interpretation
    • –  Can lead to a net bias in the Wolf number

 

Rodney

tst
AR2738

Rodney,

Thanks for the response. I'll follow your lead and count it as two spots.

Regards

Steve

Log in to post comments
AAVSO 49 Bay State Rd. Cambridge, MA 02138 aavso@aavso.org 617-354-0484