Solar activity October 6th

[brianb]

A disappointing day today, a front was supposed to be clearing through by lunchtime but it dragged its feet & conditions were too poor to observe until the sun was getting very low. Even then the transparency was poor, with thin high cloud adding to low altitude absorbtion, and the seeing was not good either.

The large "hedgerow" prominence which has adorned the NNW limb recently has decayed to insignificance, but there is an interesting complex prominence group on the WSW limb.

2009 Oct 06, 1607 UT. Solarscope SV60 @ f/16. Lack of light prevented me from using the 4x Imagemate.

[Dave Smith]

In spite of the conditions a nice capture Brian.

Do you mind me asking here, but how do you deduce the compass settings?

Dave

[brianb]

how do you deduce the compass settings?

The scope is on an equatorial mount. The camera is rotated until the long side of the frame is parallel to the apparent motion of the sun's limb when the mount is moved back and forth in RA. North (increasing declination) is now at the top of the frame. This is not the same as solar north, the angle the solar axis of rotation makes with the lines of constant right ascension has to be deduced from tables in e.g. the BAA Handbook.