posted on Dec, 6 2007 @ 08:59 AM
The hubble ABSOLUTELY can focus on the moon. It is essentially at infinity.
The ONLY REASON the hubble wouldn't be used to take photos of the moon might be that the brightness of the moon would saturate the ccd detectors used
to image whatever the telescope is looking at.
The moon is very bright compared to most deep-sky objects. Considering the hubble has a 78" mirror, it would gather up a lot of light at its focus,
perhaps too much.
Many people who use their amateur telescopes at home to image the moon find it more comfortable to look through them using a filter to tone down the
brightness. Anything over 6" of aperture can be quite a strain on the eyes.
This doesn't mean the hubble can't view the moon; certainly they could have designed in some kind of filter so that the imaging detectors wouldn't
be overloaded. I think they just decided against it, because most of the scientific work of telescope study of the moon can be done with ground-based
telescopes much more economically.