Quote:
Originally Posted by bojan
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Thanks for the advice Bojan, with the weather predicted to improve here nearer the weekend, I'll try out that suggestion from home because it won't require dark skies to conduct the experiment.
Quote:
Originally Posted by strongmanmike
Some cool results there Michael. Using old lenses for digital photography can be a lot of fun but yes many old lenses produced bloated stars because of the CA, which as you point out tended to be somewhat hidden with film. These results suggest that persevering with some longer exposures would be worth it 
I dabbled in using a Pentax lens, that I had used in the mid 80's, using a small CCD, back in 2006. The Pentax 200mm F2.5 was a cool lens for photography but not up to speed for the sensitive CCD era. I haven't gone back down that route again since but have always wanted to have another go with some Pentax 6X7 lenses (ala Greg Bradley), the later models of which were pretty sharp 
Mike |
Thanks Mike, the Pentax 300mm is a fairly sharp lens so I may just try Bojan's method of creating an external aperture to lessen the affects of CA. I agree longer exposures would have made these better images but dew defeated my attempts on the Witch Head this night from capturing more. Also, 3mins was the best I could do unguided at 300mm, I can't be bothered auto guiding when I have to drag all the gear to a dark sky site for one night. By the way, how would you attach the Pentax 6X7 lenses to a ccd camera? Are adapters available? Those lenses would create a nice big image circle enabling most of the coma at their edges to be cropped out by the sensor.
