Well, haven't posted in awhile. the weather has not cooperated for critical viewing but I can make the following comments:
The FS-102 has an incredibly good star test ... a keeper for sure. The TSA-120 has virtually a perfect star test ... need to check it a few more times.
The SV105T has an excellent star test as well. At first, it seemed identical to the FS-102 but the Tak I think tests a tad better. All are
well above acceptable, or even good.
The FS-102 has a slightly different character than the SV-105 for planetary. Both are very sharp and contrasty but the FS102 somehow is a tad more engaging when viewing Saturn and lunar. The SV105 was delightful for low power, wide field viewing. My favorite for just scanning the milky way and getting lost in stars. The TSA was also quite nice being brighter but, the focal length wasn't as conducive for LP viewing. No color seen on the lunar limb with all three.
Hard to call. I wish I could afford to keep all three. They each have a different personality. Definitely keeping the TSA-120 due to aperture and exquisite optics.
The fluorite doublet FS102 has always been among my favorites but, too close in FL to the TSA. The SV105 is a delightful apo, friendly, and a performer.
If I could keep two I'd keep the SV105 and the TSA120, even though the optics on the FS102 seem a bit superior to the SV.
If I couldn't afford the TSA-120, I'd keep the FS-102. Always loved Tak fluorite doublets.
Anyway, enough rambling .... the clouds are starting to affect my thought precesses.