On my quest for the "scope of a lifetime", I think I have narrowed the choice to a Tak FS-128 or TEC 140. I have compiled the following information and am hoping for comments.
Tak FS-128
Advantages: lower weight 16.5 vs 18.8 lbs for TEC140, flourite doublet- faster cooling?, air-spaced- don't have to worry about oil leaking or oil degrading over time, less expensive on used market, dew shield easier to move
TEC 140
Advantages: triplet - slightly? better color correction,
10 mm greater apeture, better focuser - smoother, fine focus knob and rotatable.
I haven't heard many people buying synta's matched with a chromacorr so am thinking there performance must be a notch below a true apo like a TAK or TEC but would welcome any comments on this. I saw that APM used to sell 120 mm synta's matched with chromacorrs for ~1,500 or so.
I thought a 2 element air spaced lense would cool faster due to less mass up front but someone mentioned to me that the air space acts as a thermal insulator so that the inside lense takes a long time to cool. Has anyone compared the cooldown times of an oil spaced triplet to an air spaced doublet?
Also, on another list, someone mentioned that the oil in a triplet can degrade over time affecting the performance of the scope. The degredation mentioned was not great but enough that owners of some oil spaced triplets payed to have them refurbished with new oil. Has anyone heard of this issue?
Dave Adams
Tak FS-128
Advantages: lower weight 16.5 vs 18.8 lbs for TEC140, flourite doublet- faster cooling?, air-spaced- don't have to worry about oil leaking or oil degrading over time, less expensive on used market, dew shield easier to move
TEC 140
Advantages: triplet - slightly? better color correction,
10 mm greater apeture, better focuser - smoother, fine focus knob and rotatable.
I haven't heard many people buying synta's matched with a chromacorr so am thinking there performance must be a notch below a true apo like a TAK or TEC but would welcome any comments on this. I saw that APM used to sell 120 mm synta's matched with chromacorrs for ~1,500 or so.
I thought a 2 element air spaced lense would cool faster due to less mass up front but someone mentioned to me that the air space acts as a thermal insulator so that the inside lense takes a long time to cool. Has anyone compared the cooldown times of an oil spaced triplet to an air spaced doublet?
Also, on another list, someone mentioned that the oil in a triplet can degrade over time affecting the performance of the scope. The degredation mentioned was not great but enough that owners of some oil spaced triplets payed to have them refurbished with new oil. Has anyone heard of this issue?
Dave Adams