Tuesday, 15 March 2011

Argon Sun - 488nm 13th March 2011

ar11166 488nm 127mm lrg, originally uploaded by Mark Townley.

For sometime now i've been contemplating the use of different filters in solar astronomy. I already have a Baader solar continuum filter, this is a 10nm wide bandpass filter centered on 540nm wavelength, this type of filter gives contrasty almost narrowband views of the sun in visible light. I know others have achieved good results in whitelight by using a deep red filter - basically the longer wavelengths are less affected by seeing, so something that has potential in the UK!

Out of curiosity for sometime now i've wondered what can be achieved at different wavelengths, then through talking to my buddy Apollo in the States started to look at filters that are used for lasers and microscopy. I settled on a 488nm filter with a 1-2nm bandpass - this gives cyan coloured views of the sun in 'argon' light.

Through the eyepeice the view was dimmer than with the continuum filter, but this is to be expected with the narrower bandpass. Granulation was larger and more diffuse than with the continuum filter, but the really obvious thing was the plage - this was really bright, almost like in the CaK images. This pic was taken with my 5" refractor with Lunt solar wedge and the 488nm filter. I think it has potential! When this image was taken the sun was only about 10deg above the horizon, with the sun high in the sky the results could be alot better!

I'm going to explore this more, however in the mean time have a 706nm laser filter on order - this is a filter in the titanium oxide band, and is also the same sort as used by the Big Bear Solar observatory. If my cameras can work at this long wavelength in the Infra red then I have hope. Watch this space for updates!