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Originally Posted by janoskiss
Stu, have you looked through a less expensive apo, like the Synta ED100 for about 1/6 of the price of the TV NP101 or one of the Vixen 4" apos for about 1/3, or a Tak 4" for less than 1/2? I wonder if the Televue betters all these scopes by such a huge margin...
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Not really. I have looked through a 5" FS Tak (Doublet with flourite at front) which I think was great, but they are not made anymore. Replaced by triplets.
The thing I am concerned about is compromising, and everything starting off OK and after at few weeks I can't overlook the faults. The advantage with the NP101 is that the Petzal design is better corrected and has an incredibly flat field, which is awesome when panning around in wide field. Even the AP triplet above is not as good in this regard (and the shorter you go with a triplet the more field curvature you get).
According to reviews on cloudy nights a long focal length triplet can beat the Petzval design but a long focal length can't get shorter. A short scope can get longer by using powermates or shorter EP's. Most doublets are long.
ED100 F9, NP101 F5.4. I would like to compare them though.
The intresting thing is that the TeleVue NP101 ($7000) and TeleVue TV102 ($4300) share the same front lens cell from all reports. The difference is the NP101 then uses another (flourite) doublet near the focuser to correct the image further and bend the light to F5.4 from F8.6. This is why the tube size of the two scopes is identical.
Takahashi make a short dual flourite Petzval, the FSQ106 I think, which is supposed to be stunning. Expensive too.
I guess I won't know how much better the NP101 will be. But I have plenty of time to figure that out and I am the type person that will choose performance over cost. If it is only a little bit better, I will spend the extra money. Some poeple may not agree with that, but when I am looking through the eyepiece I am not thinking about money.
The trade off is I don't want to die before I get I good scope, so can't save for too long.
