oil spaced triplet or air spaced?

Can anyone help me understand the difference between an oil spaced triplet and an air spaced triplet? Also what is the benefit and downside of each in cooling time, maintainance, etc...
danny

Daniel Janosick said:

Can anyone help me understand the difference between an oil spaced triplet and an air spaced triplet? Also what is the benefit and downside of each in cooling time, maintenance, etc...
danny

Hi Daniel:

This is one of those topics that has been covered a few times in the past. I encourage you to use the search function to read the old threads, paying particular attention to the posts by experts like Roland Christen and Roger Ceragioli. My understanding is that a well executed refractor lens of either type will be an outstanding instrument. An oil spaced lens might have a bit less scatter and a very slightly higher transmission, due to fewer air to glass interfaces. An air spaced lens might have equivalent transmission given the efficiency of modern coatings. An oil spaced lens might cool down a bit quicker, depending on the size of the air gaps. An air spaced lens will potentially give the designer more degrees of freedom to cancel secondary aberrations. Both should be maintenance free for life.

Roland Christen (who has made superb lenses of each type) recently posted on the TEC Yahoo forum that the cost and skill involved in making a good lens of either type is equivalent.

Jim