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Tamron 200mm lens on QSI583. H-alpha (red) and O-3 (blue/green). 12 x 15 minutes each at -15C.

  • Currently 3.66667/5 stars.

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Comment by Greg Marshall on July 15, 2011 at 9:00am
Thanks for comments, Derek. I've been wondering (in general) whether RGB data would add significantly to these images. In the case of the Veil I'm skeptical, but for brighter objects that are mostly hydrogen it probably would.

The lens is stopped down to f/4, approximately. This is a tricky part of the adapter I made: There is a small piece that pushes the aperture actuator on the lens to the right place, but I set it by just visually comparing the aperture appearance with how it looks on my Nikon camera at f/4.

I wish that I had ordered the 31mm filters, but I didn't know about them at the time. However, vignetting with this lens is not very different from what I get with my 'scope. In both cases the optics are more complicated than a simple refractor (retro-focus design in the Tamron lens and focal reducer on the 'scope), so I don't really know how to apply the specification for minimum focal ratio - I just try it and see.
Comment by Derek Baker on July 15, 2011 at 4:57am
Two questions for you Greg:

1. What f-stop did you use on the lens?
2. Do you use the less-obstructed 31mm filters that you can get for the QSI cameras, or were you able to flat-field any vignetting out with the regular filters?


Comment by Derek Baker on July 15, 2011 at 4:53am
Great image Greg! I liked the preview of it, but when I looked at the Full Size version, I was blown away with what I saw. Lovely focus, nice flat evenly-illuminated field, great colours, and a lot of detail.

Perhaps, after you have had your nap, you could aim to get some RGB data for the stars to take it from an "A+" image to an A++ . :-)
Comment by Greg Marshall on July 14, 2011 at 10:19pm
I made an adapter to attach Nikon F lenses to a camera with T threads. It was originally designed for a different camera, but just happens to work perfectly with my QSI583. That is, the thickness of the adapter puts the lens at just the right distance so that "infinity" focus is where it's marked on the lens.
Comment by spike77 on July 14, 2011 at 6:32am
i have two tamron lens also i love em i had no idea u could get this with it tho
Comment by Trevor Woodrow on July 11, 2011 at 12:45am
Nope, you need to get out and shoot some more!
Comment by Greg Marshall on July 10, 2011 at 9:15pm
Thanks, guys. Can I take a nap now?
Comment by spike77 on July 10, 2011 at 8:05pm
wow very nice man
Comment by Trevor Woodrow on July 10, 2011 at 7:58pm
Beautiful...well done, calendar worthy. Love the huge fov.


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