Aperture size question

[l3gendluk3 (Luke)]

I took a nice picture of M42 a couple of nights ago even though it was really close to the moon. My friend and I had a discussion about what will get a better image my 5" or his 6". In normal situations we would have both agreed it would have been the 6" but M42 was really close to the moon. Would the larger aperture be worse in this case, bringing in more of the moonlight?

Thanks,

Luke

[glend (Glen)]

As long as the moon light is not coming directly into the tube the effect should be the same for both (meaning the General sky glow is the same). However, a larger aperture will gather more light, and usually in newts means a longer focal length which can give you higher magnification with the same eyepiece. Magnification being the focal length of the scope divided by the focal length of the eyepiece. In this case I will assume the f ratio is close to the same.