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Just a word on the Tak Sky 90. Don't own one, spent a bit of time with one.
It does offer an excellent portable package as a travel scope and probably maximises 90mm of aperture into the smallest most transportable easily mountable package you will find.
It's a 90mm F5.6 Flourite Doublet which is exceptionally fast for the design and borders on whether it qualifies as a true apochromat. Most apochromatic flourite doublets are significantly slower. For instance the TV 85 is F7.5 and has less false colour than the Sky 90, but is a significantly longer package with sligthtly less aperture. In a small aperture wide field refractor that you intend to mainly use for low medium power wider field views the Sky 90 is excellent and probably as good a choice as you could make. If you want a small aperture portable scope that you can also use for planetary and lunar work, whilst the Sky 90 will do the job and pretty well, there are better choices around this aperture for that purpose. For instance while the TV 85 is longer, I think it better suited to lunar / planetary and double stars, than the Sky 90. Similarly, just about any decent triplet around this aperture will give slightly better colour correction and high power views than a doublet, but it will also be heavier and generally more expensive. You need to determine what are the most important criteria in your decision process.
Cheers
John B
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