Re: [APML] sharp image with 5 mm lense

["Bert Katzung" <katzung1@comcast.net>]

Hi Mango:
All of the things you mention can contribute to a fuzzy image, but probably
the most important is the focal length of your eyepiece. Unless you have
superb optics (both eyepeice and mirror), a 5 mm eyepiece is pushing the
magnification too high in this scope. Your 1000 mm focal length with a 5 mm
EP gives 200x and that's asking a lot! A reasonable rule of thumb is 20x per
inch of aperture, so with your 114 mm aperture, about 80-90 x is the maximum
magnification you should expect to give nice clear images. I know that the
books claim a maximum of 40 to 50x per inch of aperture, but that's assuming
perfect optics and perfect seeing conditions.
Hope this helps,
Bert

Bert Katzung
katzung1@comcast.net
www.astronomy-images.com

----- Original Message ----- 
From: "mango" <j.kolling@chello.nl>
To: <astro-photo@seds.org>; <videoastro@yahoogroups.com>
Sent: Monday, November 10, 2003 9:11 PM
Subject: [APML] sharp image with 5 mm lense


>
> I have a new telescope, a newtonian 114/1000
> and when i used it to watch the moon yesterday
> when i put in a 5 mm lense the image wasn't clear,
> could this be because of the quality of the 5 mm lense,
> the weather (it was not very clear and a little misty, but just a
> little), the mirrorsize, the focal length, or something else?
>
>
>
>
>
>
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