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Milky way around Deneb


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About this observation
Kevin Gurney
Time of observation
24/09/2017 - 01:30
Deneb, surrounding star fields, and nebulosity
Observing location
Kelling Heath campsite
Tokina 70-200mm lens (MF)
Atik 460EX mono, SX guide cam
Skywatcher AZ-EQ6-GT
Geoptik EOS CCD adaptor, Fotodiox EOS adaptor
5min subs, bin 1x1, 4 subs.

The weather at Kelling was 'mixed'.... So I decided to try a 'simpler' rig that did not demand as much exposure time (in principle) to get something worth having. This used an old  70-200 zoom Camera lens I inherited from my Dad (he was a keen and technically accomplished film photographer but was always terrestrial in his pursuits). I had bought adaptors to fit my CCD to this lens with a view to doing some wide field imaging. Here was the perfect  opportunity...

A first experiment with the lens wide open at f4 showed severe coma around the edges (I had read about this but needed to see it first hand :). I stopped down to f8 and you can see the result. The zoom was set to 70mm to get widest field possible. The effective aperture here is pretty small but there is a relatively large amount of light being recorded.

I would like to use filter sets with this rig (and with different lenses) but the backfocus on camera lenses is limited, making focus impossible with a filter wheel (I did try). The only solution I can see is from Starizona (replace the Geoptik) , or to use the Baader UFC system in front of the lens.

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