Monday 23 November 2009

Messin' with filters

Lumicon’s 1 ¼" UHC filter is a superb addition to my visual astronomy toolkit. I’ve seen the stringy, fluorescent shockwaves of the supernova remnant in Cygnus, the North America nebula, and now I have faintly seen the glow behind the horse head nebula. But for photography it is a bit disappointing. The light is mostly rejected - it seems to be too narrowband for good imaging and the light really should be collimated first for it to block the correct wavelengths. I can’t quite work out why the photographic result should be so different to the visual experience at the eyepiece. Any comments welcome. I did 5 exposures that tested the tracking of the 20” scope (60-90 seconds each). Detrailing, stacking and processing resulted in this faint but fairly decent picture of the Horse head nebula's Hydrogen Beta (H-β, λ = 486.1342 nm) emission.

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