Mapping the Sun
The Sun's axis of rotation varies in relation to the solar North pole over the course of a year. Interesting article in Sky at Night magazine about using freeware programs "Helio" and "Tilting Sun" to measure the tilt and overlay a grid for any solar image taken at a particular time. 0-180 line is true North-South and on the 30th September 2017, the axial tilt (P0) was 25,93 degrees.
There is also variation on the forward tilt of the Sun over the year. You can see more grid lines at the North Pole than the South in this instance. The angle of tilt is given as B0 and varies between plus and minus 7 degrees over the year.
The article also quoted the Mount Wilson Solar Seeing Scale - there was good seeing on the day this image was taken - probably a 4:
4: Sun is sharp for more time than it is fuzzy. Solar granulations visible for most of the time. Limb motion and resolution are in the 1-2 arcsecond range.
Equinox ED 120mm scope with Baader Herschel wedge
ZWO ASI174 MM cooled to 14c
Mapping the Sun
The Sun's axis of rotation varies in relation to the solar North pole over the course of a year. Interesting article in Sky at Night magazine about using freeware programs "Helio" and "Tilting Sun" to measure the tilt and overlay a grid for any solar image taken at a particular time. 0-180 line is true North-South and on the 30th September 2017, the axial tilt (P0) was 25,93 degrees.
There is also variation on the forward tilt of the Sun over the year. You can see more grid lines at the North Pole than the South in this instance. The angle of tilt is given as B0 and varies between plus and minus 7 degrees over the year.
The article also quoted the Mount Wilson Solar Seeing Scale - there was good seeing on the day this image was taken - probably a 4:
4: Sun is sharp for more time than it is fuzzy. Solar granulations visible for most of the time. Limb motion and resolution are in the 1-2 arcsecond range.
Equinox ED 120mm scope with Baader Herschel wedge
ZWO ASI174 MM cooled to 14c