Posts Made By: Wayne Wlocka

I recently saw an ad for Explore Scientific's 127mm and 152mm f/6 achromatic refractors and at $600 and $700 for the OTA plus case and accessories these really fit well into my budget. Apo's at these apertures are out of the question.

However my question is if anyone knows the weights of these OTA's and what are the accessories that come with them?

I realize that these are medium focal length and may exhibit CA but if they're at least close to Orion's 120 f/8.3 achro. I can live with that. The tubes should be about 3 feet long, no problems there.

Thanks for any info.

I'm confused as to the correct use of ED and Apo terminology, upon reading some books that give a history on the development of telescope optics it seems that the term Apochromatic applies when there are 3 lens elements that bring the red, green and blue parts of the visible spectrum to a common focus thus eliminating chromatic aberration (CA).
So it would seem to me that ED is a two-element doublet with a different glass type (than an achro.) to acheive nearly the same result but is not quite as good as a "true" Apo, looks like the terms are used interchangeably but I'm not sure which is correct

Thanks. :S