Info | Votes | Messages | More Stats | Up One Level |
Subject: Re: vote by xxx.xxx.134.49 By: Anonymous (xxx.xxx.93.16) In Reply to: Anonymous (xxx.xxx.134.49) (Original Vote) Date: 10/24/2003 11:21:28 am PST >No ED-doublet refractor should ever be called "apochromatic"! Not even the fluorite-doublets are! True apochromatic refractors are of true triplet or quadruplet design - which for example excludes doublets with additional field flattener lenses... The above is a political statement more than a rating of the product. With modern glass and lens design it is possible to build an APO in a doublet configuration. The ED114SS review in S&T (5/02) called it an APO and compared it to other APO scopes. Some quotes from the article: "Jupiter looked neutral white when sharply focused, with no surrounding halo of blue light, remarkable for such a fast-foca-ratio refractor." "Bright 1st-magnitude stars appeared clean white, with no halos from chromatic aberration." This is not a fluke, many Tele Vue scopes are doublet APOs also. Subject: Re: vote by xxx.xxx.134.49 By: Anonymous (xxx.xxx.74.5) In Reply to: Anonymous (xxx.xxx.93.16) (Original Message) Date: 11/20/2003 08:31:18 pm PST "This is not a fluke, many Tele Vue scopes are doublet APOs also." As are the Takahashi FS series. The modern definition of Apochramatic from the TMB website: "An objective in which the wave aberrations do not exceed 1/4 wave optical path difference (OPD) in the spectral range from C (6563A - red) to F (4861A - blue), while the g wavelength (4358A - violet) is 1/2 wave OPD or better, has three widely spaced zero color crossings and is corrected for coma." As you can see, it has nothing to do with whether it's a doublet, triplet .... all reports so far rate the Vixen EDs as apochromatic. Page 1 of 1 |
|
©2023 by Excelsis Consulting. All Rights Reserved. E-mail webmaster to report abuse, problems, or comments.