I have obtained a used Celestron/Vixen C102/1000 refractor, and was hoping Bob May (or some other person more optically savvy than me!) could possibly answer this question:

The objective has what looks like "Newton's Rings" in the objective...they are slightly off to one side.

I have seen these on two optical flats in close contact, and know that it is possible with an air gap(Fizeau Bands?), but does this mean the lenses in the cell are too close together? I can see the 3 small aluminum spacers between the elements, so no one removed them and forgot to put them back...

The images appear fine, and I'm not really not sure what a star test should look like since I'm still in the process of learning how to perform them. The star test rings are round though, and I thought they would appear like little triangles if the optics were "pinched."

The images appear to be really good so far, up to about ~200x on Saturn (about 50x per inch), nice tight little stars, not too much false color, etc

Should I loosen the retianing ring, or just leave everything the hell alone? (the eternal question)

I've heard of refractor owers liking to keep the objective slightly loose in the cell? Some even like it to rattle?!

Joe

• Newton's rings - bobmay - October 17, 2001 - 18:36 UTC