Wed, 11/30/2022 - 18:40
I have been observing the Sun for a few weeks and wanted to ask some questions. I read in Jenkins' book that each isolated spot (distant more than 10° from the others) should be counted as a group. Sometimes on the sites (SDO etc.) they report the isolated spot, but they don't count it... For example today 2022/11/30 at 10.45UT I marked a spot in the Southern hemisphere (about -31.5° latitude, 36.1° longitude con software Heliov41). Should I include it as a group?
An unspotted facula often occurs at the edge of the Sun: I evaluate it as an active region, but obviously I don't count it.
Maurizio Cervoni
Italy (Rome)
Hi Maurizio,
Spot counting is indeed both a science and an art. The 10-degree rule is generally a good guideline, but there are always exceptions. Learning the difference in appearance between a pore and small sunspot is important and a challenge, but also remember all counts are really estimations that are averaged among many observers whose counts vary throughout a day.
Faculae without a visual spot would not be counted even with an AR number assigned. A sunspot or group without an assigned AR number would be counted. To be assigned an AR number several solar observatories must report it to the NOAA before a number is given. Hence a new spot can appear on a SDO image before a number is given it.
Also, download and read the AAVSO Solar Observing Guide for their recommendations for sunspot counting, etc.
https://www.aavso.org/solar-observing-guide
Jamey Jenkins (JENJ)
Hello and thanks for the info!
I've read the guide, but I preferred to clarify some points that weren't reported, or contrast with other readings.
I take the opportunity to ask one last thing: what magnifications to use!!
Is it true that in order not to count the pores, you shouldn't use a magnification higher than 63? Ideal between 45 and 60? So I go about buying an eyepiece for my Mak127/1500
Hi Maurizio,
I don't believe there are any firm "rules" regarding magnifications. The solar observer Wolf in the 1800's used an 80mm refractor at 64x for his spot counts. Think of that as a guideline if you wish. The usual recommendations I've heard and use myself, are to choose a magnification that allows viewing the whole disc to locate and count spot groups, then switch to a higher magnification (usually 100x or less) for counting individual spots within the groups. Seeing conditions tend to limit the higher magnification chosen on any given day. The key in my mind is to find a routine that works for you and then use that plan daily. Be consistent in your observing routine.
Best of luck in your observing...
Clearest Skies!!
Jamey (JENJ)