Question: Focal length calculation

Hey everyone, Question: How do you figure the F number when using eyepiece projection? I have been "trying" to get planetary images, they never turn out good. Images are usually pretty pixelated. I read in S&T that I should be between F2O and F3O, is that correct? My scope is a 6 inch F5 reflector. I'm using a digital camera. I have been using a 2x barlow and a 5.5mm eyepiece, the camera lense is about 1CM from the eyepiece. When I upload the pictures to the PC, the planets look pretty small, but not sure how big or small they are image scale-wise for you guys who are getting all these awesome images! Thanks for any help! Ron

Ron,

Try

http://www.covingtoninnovations.com/astro/astrosoft.html

This free program helps calculate all types of exposure, including eyepiece projection.

Alex

Hi,

check this formula:

http://www.licha.de/AstroWeb/articles_fullsize.php3?iHowTo=2

Hamp