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The Stellarvue SV90T Fluorite

Posted by Ivan Ong   04/29/2009 12:00AM

The Stellarvue SV90T Fluorite
Back in WWII North American Aviation came out with the P51 Mustang fighter. With a subsequent grafting of the excellent Rolls Royce engine in place of the lower powered Allison, a compact air frame with low drag laminar wings, and heavy armament, suddenly everything became right and the allies had a legendary fighter that could escort bombers deep into enemy territory and all the way back.

I regard the Stellarvue SV-90T Fluorite as also one of those instances where the confluence of design factors has made everything wonderfully right. The scope’s raison d'être is super righteous optics and portability. So what makes this scope so über super?

Focuser: The Feather Touch focuser is so creamy smooth that it brings back memories of the vacuously endowed Fabio saying, “I can’t believe it’s not budder” on TV. But this Feather Touch is no tacky beef cake. The tension adjuster is in the bottom, and I can achieve an unbelievably wide range of tension adjustments to cater for loads ranging from my lowly 1.25” diagonal (hey, who uses these anymore?) to my fully loaded DSLR. The preciseness of the Feather Touch is a hands-down winner and turns the Stellarvue into a pleasurable visual instrument and a precision platform for astrophotography. The only other focuser I truly admire is that piece of art on my A-P Traveler.

I have an earlier version of the SV90T without the rotating focuser. While it would be a nice add on, I don’t miss it as I use this scope primarily in Alt-Az mode.

Optics: Here is a potentially explosive topic, judging by many posters who have reported having their socks and other clothing items “blown away” by various and sundry scopes. I therefore take extra precautions by donning on a pith helmet and ankle length gold toe socks each time I take to the field with my Stellarvue SV-90T. Folks, there is something really special with Fluorite lenses done right, and the Stellarvue triplet fluorite has certainly been done very right indeed. All my current and previous fluorite scopes (Vixen 80F, 90F, Celestron 102F, Tak FS-102 and now the Stellarvue) have the same school book approach of tight stars with clean diffraction rings, no false color, excellent contrast, and snappy focus. If you do a lot of bird watching, particularly those with wings, you will find that the Stellarvue gives extremely pleasant out of focus branches and leaves bokeh that are free of color tinting at the edges especially when illuminated with a strong low sun. This is purely a personal taste- but I rather have that than doublet scopes that immediately show irritating color the moment you move out of focus.

The 90mm Aperture of the scope is small, but not too small as to become unreasonable for light observation and study. The planetary and double star performance of this scope is very good. The 630mm focal length of the scope is useful for this aperture class (As a reference, the A-P Traveler is 610mm, and a Vixen 80mm FL is 640mm). The 630mm focal length allows planetary and double star observation with a 4mm at 160X, and a wide field 21X with a good 30mm ocular. This is a useful spread of magnifications. I’ve also barlowed my 4mm Radian with a Baader Barlow on Saturn and had very sharp views on steady nights. I’ve seen the E and F of the Orion trapezium on clear steady nights with no issues. The Rigel double star is gorgeous. The nice focuser certainly helps high magnification work.

The contrast of the Stellarvue is exquisite- M42 under dark skies simply explodes into an orgy of visual delights of Caligulaic proportions. I don’t think those chaps wore socks back then- but they would have been blown away if they had. There, I said it. No scope review is complete without the requisite hosiery blow-off.

Size and Length: In designing the Stellarvue SV90T, Vic Marris has done a commendable job in optimizing the portability of the OTA. For example, the large dew shield extends out. Waaay out. I’m sure you have seen “play thing” sliding dew shields that extend a modest few centimeters before getting stage fright. The Stellarvue goes all the way out by design. This is an important consideration for travel because one cannot always haul a 12V gel cell and dew heaters around the world. It is always good to get as much passive protection as possible from dew.

The length of the SV90T is about that of the Traveler (about 19.5”) and there is great opportunity to achieve good balance. The scope is neither front nor back end heavy. I’ve used the optically superb TV-76 in the field and have had some issue with balance with the short tube. There are other scopes that also require off-set plates- which translate as added weight to haul around. I have rings (instead of the clam shell) on the SV90T and that allows a wide range of adjustments depending on what I am hanging on the end.

Airline portability was a consideration in my decision to get this scope. You never want to check in a scope. I’ve seen some baggage handlers from my window seat and some of these talented gentlemen remain sadly undiscovered for the Olympic hammer throw event. That said, the C4 Stellarvue case is a tad big although still carry on portable. I am using my Traveler case with the SV90T for travel, and that cuts a good 3 inches in the width while carrying everything the C4 case can hold. The reason here is A-P’s case uses Velcro pads while Stellarvue uses block cut foam, which takes up more physical space for padding.

Weight-The SV90T OTA is very light, weighing in around 8 lb or so with rings. The scope can be used with lighter field mounts like a Vixen Porta. The vibration suppressor pads do help a great deal for double star and planetary observation. I’ve recently shifted to a Tak Lapides Modified Teegul with a tangible improvement in stability.

Finish-Well, here, I would rate my Stellarvue just a slight tad behind Takahashi, Televue and A-P in terms of machining. I noticed that the retention ring on the hood had some roughness/sharpness to it. Unscrewing the dew shield also felt like opening a rusty gate. Still, it is not a complaint and overall the fit and finish of the scope is very solid. The design intent of the SV90T was not to be built like a tank but with an eye on weight and portability. Happy to say, the objective was well fulfilled. The powder-coated Stardust blue finish is very attractive and many people have commented on how beautiful it looks. It is not waxable and very low maintenance (many Tak owners wax their scopes with the frequency spandex-clad weekend bikers shave their legs. I do- wax, that is).

In conclusion, this is a really good scope, and an excellent choice as a travel instrument. It is good value and a good buy. I know the import dealers always seem to want to imitate high end companies like Stellarvue model for model and feature for feature but there is a definite advantage in getting the real deal. I’ve talked to Mr. Marris on the phone twice and I agree with this guy’s reputation of offering receptive, no nonsense customer service.

I’m done. Thanks for reading and I’m off with my pith helmet and black ankle length socks.