I know this will stir up a lot of people, and any list is necessarily subjective, but I perceive that many inexperienced amateurs don't really know how much better APOs are, perhaps believing marketing hype and assuming they are all perfectly corrected.
Nevertheless here is my stab at a listing of relative color correction. Perhaps the group mind can add to--or rearrange--the list. Based on a combination of impressions over the years, ray tracing of some designs, and the occasional A-B comparison. Some of the subjective element I believe is to personal preference, for instance I find red error to be far more annoying than blue, whereas photographers may disagree.
The chromacor is not included because the correction depends on aperture and F#, can vary from essentially perfect down to 2.5x on very large achromats like my 8"F12.
1x achromat
1x semi-ED (meaningless)
2x semi-APO (meaningful, Zeiss and others)
3x Pentax EDUF
4x Meade ED/APO doublets
5x Pentax SDUF, original TV Genesis, TMB EDStar, 66mm F6 doublets, Nikon FieldScope ED.
6x Vernonscope/AP 94mm, TV Oracle, TV60
7x Vixen ED doublets
8x Fluorite doublets, Takahashi, Vixen, etc.
10x FSQ
12x TEC 110, 140 oiled triplet
16x TMB Russian triplets, TV NP101, Takahashi TSA, Astro.Tech.90EDT, WO 132 triplet
I haven't seen recent APs or the Tak TOA, but I expect they are at the top in correction, ie, bottom of my list.
Nevertheless here is my stab at a listing of relative color correction. Perhaps the group mind can add to--or rearrange--the list. Based on a combination of impressions over the years, ray tracing of some designs, and the occasional A-B comparison. Some of the subjective element I believe is to personal preference, for instance I find red error to be far more annoying than blue, whereas photographers may disagree.
The chromacor is not included because the correction depends on aperture and F#, can vary from essentially perfect down to 2.5x on very large achromats like my 8"F12.
1x achromat
1x semi-ED (meaningless)
2x semi-APO (meaningful, Zeiss and others)
3x Pentax EDUF
4x Meade ED/APO doublets
5x Pentax SDUF, original TV Genesis, TMB EDStar, 66mm F6 doublets, Nikon FieldScope ED.
6x Vernonscope/AP 94mm, TV Oracle, TV60
7x Vixen ED doublets
8x Fluorite doublets, Takahashi, Vixen, etc.
10x FSQ
12x TEC 110, 140 oiled triplet
16x TMB Russian triplets, TV NP101, Takahashi TSA, Astro.Tech.90EDT, WO 132 triplet
I haven't seen recent APs or the Tak TOA, but I expect they are at the top in correction, ie, bottom of my list.
"--Granted, that's a worse case scenario. The destruction might in fact be ... limited to our own galaxy."
