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Old 01-11-2007, 09:28 PM
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5ash is offline
Join Date: Mar 2005
Location: Hunter valley. nsw
Posts: 1,003
Originally Posted by Terry B View Post
I superimposed the little image on the big one using the gimp and got a rough measurement of 150 pixels wide compared to the big image of 720 pixels. This gives you a focal reduction of ~0.21x
I don't know the focal length of your scope but just multiply it by ~0.2 to give a pretty close estimate.
To get a much more accurate estimate you need to plate solve a star field through the focal reducer. I have an old version of AIP for windows that I would use to do this. I'm sure there are other programs that can do the same.
Hi terry thanks for the help. The focal length of the LX90 is 2000cm , so 0.2 of that is 400cm, F2 .The image looks very good for f2 , didnt think that was possible with an LX90 , cant wait to see how astropics come out.
regards philip
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