Galileoscope - Plastic vs Glass Lenses

A day and a half ago I made my first lunar observations with the Galileoscope. I took that opportunity to also experiment with eyepieces.

The Galileoscope's eyepiece and barlow lenses are all made of uncoated plastic. From a cost point of view the decision to make them so was a good one. A single eyepiece with coated glass lenses tends to cost substantially more than the whole Galileoscope kit.

I had noted in an earlier post that glare, or scattered light, was evident when observing Jupiter. When I observed the moon the glare was once again evident. As with Jupiter, at 25x the glare was confined to the region around the limb of the bright object (in this case, the moon).

When I used more costly eyepieces with coated glass lenses the views of the moon became very sharp, contrasty, and glare-free. Yet, the view with the Galileoscope's plastic lenses (at 25x) wasn't too terribly worse. The moon itself looked very similar, virtually identical except for the glare around the lunar limb.

At 50x using a quality eyepiece composed of coated glass lenses the moon was very sharp, contrasty, crisp, and glare-free. But the finest detail visible with the quality eyepiece became very difficult or even impossible to see with the Galileoscope's stock eyepiece and barlow. The moon appeared 'washed out' with the plastic lenses. Nevertheless, one could still see more lunar detail at 50x than at 25x with the plastic lenses.

What about the Galileoscope's glass, achromatic objective? The eyepiece experimentation revealed that the objective is capable of producing very sharp, contrasty images. I was impressed by the quality of the objective, but at magnifications greater than 25x one needs to use higher quality eyepieces to make the most of what the objective has to offer.

On the same night I made observations of Jupiter, Neptune and Uranus with the Galileoscope. The latter two looked indistinguisable from stars. Nevertheless it was a pleasure to see them with the Galileoscope.

While observing the moon and trying out different eyepieces I noticed that an occultation of a star was going to take place. I observed the occultation using the Galileoscope with a far more expensive 7mm Nagler eyepiece. Of course, the occultation could have been observed with the Galileoscope's own eyepiece with or without the barlow. It was with the stock, 25x eyepiece that I became aware that an occultation was imminent.