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Takahashi Sky-90

Bought Sky 90 serial #0010 in Feb 2001 returned it two weeks later. Another person owning serial # 0008 did the same.I bought it with the intention of replacing both my TV101 and Tak FS102 since the Sky 90 could be fitted with the Q extender and transformed into a f/8. I did numerous side by side comparisons with the TV 101(f/5.4 540mm) using matching TV Everbrite diagonals and matching eyepieces.I expected the performance to be virtually identical but with the 90 being a bit dimmer. I found that the Sky 90 was clearly not up to the task of replacing the TV101.It lacked the crispness and contrast of the 101 and had noticeable false color on Venus, Sirius and Rigel.The color was not bad but it was there whereas it was non existent in the TV 101.I communicated a lot with the owner on #0008 and with Mike at Astronomics. He felt some of the problem might be caused be the relatively wide airspace between the doublet. All I know is the scope would not give consistent performance. One night it would perform at 90% of the TV 101 and the next markedly below.Meanwhile the TV 101 would jist keep on giving outstanding performance.It seemed abnormally sensitive to atmospheric and/or thermal distrubance. Mind you both scopes were stored side by side in an unheated garage so it was not lack of cool down. The Tak 1.6 Extender Q helped quite a bit but when I used it with the 101 again the little Sky 90 couldn't keep up.I noted some false color on Venus and bright stars such as Sirius and Rigel.Jupiter was colorfree but iy simply was not as sharp and crisp as I felt a Flourite apo should be. In fact the Sky 90 was not as good as my Celestron C70 Flourite. The C70 is a hard act to followbut the Sky 90 should have been as good. Nor did I feel the 90 was equal to my TV85 but I did no have the 85 to compare it to.Both Mark, the owner of #0008 and I feel that there is perhaps a design problem. Something is going on with the Sky 90 but we do not know precisely what. Ghosting was another problem. Jupiter and venus were surrounded with a ditracting bright halo whereas the TV101 present stark black background.We both concluded that the concept was great, It is a beautiful well made scope but it is not worth $2200 for a plain ota. You are talking $300+ for the Q extender and another $300 for a Tak 7x50 finder and a $100+ for rings and you still have not got a diagonal,case or eyepiece. If you are looking for an excellent travel scope in the 80-90mm range go with the TV85 a much better
choice.If travel isn't an issue stick with the FS102 or TV101 with photo and
visual use is your interest. Is the Sky 90 a bad scope? Not at all.Is it a
great scope? No Way!In some ways it struck both of us as a well above average $2200 Orion Short Tube 90 and that is not a great deal.I may have been happy had I not done the side by side comparison in that I might have concluded it was bad seeing.As I said sometimes it would perform very close but never equal to the TV 101. But when I saw Mark was selling his I felt something was going on and he confirmed my suspicions.If Tak can get the Sky 90 to perform up to the level expected of a Flourite apo they will have a real winner. size and weight are fantastic and it did quite well on richfield work but in my opinion there is a problem or at least there was in Numbers 0008 and 0010.If you buy one be sure you can return it for a full refund if you run into these problems. I might add on the star test outside focus presented sharp but purple diffraction rings. Inside the rings were indistinct and greenish/yellow.By comparison both my TV101 and C70 FL were virtually identical on both sides of focus and very close to prue white.In focus stars were pinpoints but on the Sky90 they were very slightly flared and enlongated. I could not get pinpoints which I have come to expect.Maybe I expected too much but I do not believe so. Mark switched his for a Tak FSQ106 and is quite happy.Buy with caution and a critical eye.
Randy Hester 3/10/2001
Dallas Tx
hesterwil@home.com

Overall Rating: 8
Weight: 1 (Unreliable Vote)
Date: 03/10/2001 01:46:17 am PST
By: Anonymous (xxx.xxx.254.206)
Link to this vote: https://excelsis.com:443/1.0/displayvote.php?voteid=41011

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