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Viewing Mars

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Posted by Gary A. Baker on August 28, 2001 22:53:48 UTC

I recently purchased an 8" LX200 (f/10) and various eyepieces, including a Televue 18 mm Radian and a 4.8 mm Nagler.

I'm trying to see Mars and I'm surprised how small it is. I expected to see much more than I am.

With the 18 mm, I should get 111x magnification and an actual field of 0.6 degree (68 degree apparent divided by 111x magnification). If Mars is 13", at 111x, it should be 0.4 degree (13 times 111 divided by 3600 seconds per degree). It should fill over half the field, but it's a small orange dot, I'm guessing about 5% of the eyepiece field.

With the 4.8 mm, I should get 417x magnification and an actual field of 0.2 degree (82 degree apparent divided by 417x magnification). Mars should be larger than my actual field. But it's still a small orange dot, not much bigger than with the Radian.

Is my arithmetic wrong or is there another problem?

When I try to focus to a larger image, it doesn't look sharp and the center obstruction of the SC comes into play.

I think I've aligned everything properly. I've used Arcturus and Antares and when I GOTO "STAR904", the orange dot is right in the middle of the field. When I GOTO "STAR903" I get the Moon. The Moon looks good.

Obviously, I'm a novice and any help anyone can provide would be appreciated.


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