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No 63 - July 2010

Recent observations


Martin Allan took this picture of the Sun on 2010-03-14, when it showed one of the more complex sunspot groups of recent years. He took a 1/250 s exposure with a digital SLR through a 5 in. refractor (1180 mm focal length) with a solar filter.

Horst Meyerdierks takes an image of the Sun whenever possible and averages his spot counts in 30-day intervals. He reports the following R numbers (number of spots plus ten times the number of spot groups):

2008-10-01 / 2008-10-30 2.8 2009-07-28 / 2009-08-26 0.0
2008-10-31 / 2008-11-29 5.9 2009-08-27 / 2009-09-25 3.8
2008-11-30 / 2008-12-29 0.0 2009-09-26 / 2009-10-25 1.5
2008-12-30 / 2009-01-28 0.0 2009-10-26 / 2009-11-24 4.3
2009-01-29 / 2009-02-27 1.8 2009-11-25 / 2009-12-24 7.4
2009-02-28 / 2009-03-29 0.9 2009-12-25 / 2010-01-23 13.7
2009-03-30 / 2009-04-28 0.0 2010-01-24 / 2010-02-22 15.8
2009-04-29 / 2009-05-28 0.8 2010-02-23 / 2010-03-24 19.0
2009-05-29 / 2009-06-27 3.6 2010-03-25 / 2010-04-23 9.1
2009-06-28 / 2009-07-27 5.0 2010-04-24 / 2010-05-23 2.8

Noctilucent cloud

Noctilucent cloud panorama
David Small took this 180° panorama of noctilucent cloud on 2010-06-20/21 at about 01:00 UT. Click on the image for larger version.

In 2009, Horst set up a digital SLR with a controlling laptop to take pictures of any NLC that might show. The camera was located at the Royal Observatory, but in 2010, the scaffolding for repair of the Observatory's copper domes gets in the way. Horst has teamed up with David Small to run the camera from David's kitchen window in the Borders.

In 2009, after a false start with a webcam, the camera missed the first few NLC sightings at the end of May. In June about half the nights, and in July virtually all nights, showed NLC. There were no sightings in August. The 2010 NLC season started later, this camera had no sightings in May, and the first NLC only on 11/12 June.

Full reports and imagery are at

ε Aurigae

Horst also collects photometry of the 27-year period eclipsing binary ε Aur with a dSLR. The light curve shown runs from 2008-10 to 2010-05 and shows "unfiltered" magnitudes; they are filtered by the green filters of the dSLR, but not corrected for the difference to a proper V filter. Each of the more recent data points is the result of ten raw-format images that contain the variable and the comparison star η Aur. The early data, covering the 2008/2009 autumn and winter, are not as good, because only four raw images were used. The group of data in summer 2009, just before the main decline in brightness, were extracted from noctilucent cloud photographs in JPG format. The JPG data format is unsuitable and the low position of Auriga on the northern horizon does not help the quality of these data.

Light curve of epsilon Aurigae
Horst's light curve of ε Aur. See text.

Although you couldn't really tell from these data, there are brightness variations outside the eclipse. The decline to eclipse began in August or September 2009. By January 2010, the decline began to level off. The last two points may indicate a brightening, or they may just be an effect of the comparison star sitting a few degrees lower and closer to the horizon.


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