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Old 08-10-2008, 02:21 PM
mbaddah (Mohammed)
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mbaddah is offline
Join Date: Aug 2007
Location: Sydney
Posts: 803
Originally Posted by dugnsuz View Post
Sold my ED80 in order to buy the 70-200mm f4L so hopefully can help...

Purchased my L lens 2nd hand for approx $650, so roughly same ball park price as ED80

I would disagree that both systems give the same results on the stars though. The L lens is very well corrected, resulting in pinpoint stars to the edge of the frame. The ED80 suffers from field curvature which needs to be remedied by using a flattener/reducer which is an additional $200 cost.
Alternatively, you may need to crop out the offending stars.

The 600mm focal length of the ED80 will let you get up close and personal with your DSOs much more so than with the lens at 200mm. I used a 1.4x extender with the 70-200 to push the focal length to 280mm f5.6 for some shots.
Here are a couple of Eta shots, first at 280mm with the 70-200mm, 2nd done with ED80. Don't judge performance on the Eta lens pic as I this was done with subs I think were not 100% focussed (excuses excuses!!)
You can see the field curvature in the 2nd pic quite clearly

...and with the lens you can take killer daytime pics too...

All the best with your decision
Thanks guys for the response. Doug those pictures were beautiful, you are right though the shot taken from the 70-200 is definitely more corrected, I'm surprised! You have made my decision even more difficult now

Wouldn't the 200mm + 1.4x = 448mm on a 1.6x Crop body?
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