Sky Watcher 102mm f/5 refractor (SW102)

The Sky Watcher 102 is a small rich-field refractor. It is very similar in design to the Orion ShortTube 80 and it's variants. Since the two instruments are so similar in design, it was of interest to me to see how the SW102 compared to the ST80.

Dealer: Hands on Optics (Gary Hand)
Price: $300 plus shipping. OTA only. Includes 6 x 30 finder scope, tube rings & 2"-1 ¼" adapter.
Make: It says Sky Watcher on the side of the OTA.
Country of Origin: China
Color: Blue
Focal Length & Ratio: 500mm f/5
Aperture: 102mm
Construction: Very solid. The focuser knobs are plastic but everything else is metal.
Fit and Finish: Very good. It is a nice looking instrument.
Baffles: The SW102 has 2 baffles. The ST80 has 1 baffle.

Objective Cell: Unlike the ST80, the screws holding the objective in place are not readily accessible. There is a substantial threaded metal collar surrounding the objective. Removing it does not permit access to the objective cell. It appears that a special tool might be needed. There is no indication of pinched optics.

Focuser: A little stiff to engage initially but moves quite smoothly after it has been used for a while. The rack and pinion mechanism is encased in the inscrutable and impervious mystery lubricant so popular in the country of it's origin. At least as good as the ST80. Also has a focuser lock.

Finder scope: 6x30 on a Vixen-style dovetail mount. Actually comes to focus. Has two set screws with a spring loaded peg for the third point of contact. The new ST80s use the same setup. I did not actually try the finder scope, although it does appear to be of slightly better quality than the one on my ST80. With the generous FOV (3 degrees with a

30mm Celestron Ultima) afforded by this fast refractor, a Celestron Star Pointer is more than adequate.
Drawtube: 2 inch with a 2" to 1 ¼" adapter.
Dewshield: Quite substantial. Metal. Press fit.
Tube Rings: Each ring has a ¼"-20 fitting on top. One ring has a ¼"-20 post (piggyback camera attachment). Felt lined. Quite easy to rotate tube in the rings.

Length: 20 inches long (not including diagonal).
Weight: About 6 ½ lbs. with the tube rings and dovetail base plate attached.
Lenscap: Plastic with removable center plug.

On balance the attention to detail on the SW102 seems a bit better than on the ST80. The front end of the drawtube could probably stand a little flat black paint. Other than that there isn't much to be done on the sample I received. I didn't notice any of the shiny screws inside the optical tube which are common on the ShortTube 80.

Mounting Options:

Bogen: I have a Bogen 410 geared head/ 3021S tripod combination which works extremely well with the ST80. At the time I ordered the SW102, a ¼"-20 mounting block was not available although I understand that it will be in the near future. Using just one of the tube rings, I set out to attach it to the Bogen head. Unfortunately, the threaded hole in the base of the tube ring is not ¼"-20. I was able to firmly attach it to the quick release plate using a "modified" 6mm flat head bolt. While this arrangement does work, it does not work as well as with the ST80. There is a noticeable amount of vibration. It takes a couple seconds to settle down. Those people who are a bit impatient (like me) will find this annoying. It is possible that the ¼"-20 mounting block will provide a bit more longitudinal support, but I would not bet on it. The Bogen equipment line is excellent but it is designed for photographic gear, most of which is not very long.

Altaz: I have a Vixen Custom D altaz mount which is far more mount than is required for this telescope. Any altaz mount similar to the Orion AZ-3 would be more than adequate for the SW102.

Eyepieces: Like it's smaller brother, the SW102 is very fond of costly eyepieces (7mm Pentax XL, for instance).However, it did perform quite nicely with the 30mm Celestron Ultima, 25mm Orion Ultrascopic, 9mm Vixen Lanthanum and 6mm Vixen Lanthanum.

Observations:

Location: Suburban (mag 4 skies).
Latitude: 30 degrees N.
Conditions: Acceptable but no better than that. Quite breezy.

Performance: No surprises. The optics seem to be the equal of those in the ST80. The difference in aperture on DSOs is quite apparent. The maximum useful magnification is around 110x. It may be possible to go a bit higher on nights of better seeing. My ST80 usually does it's best work at about 80x.

Planetary/Lunar Observations: Like the ShortTube 80, the SW102 is not well suited for serious planetary observation. Lots of secondary spectrum visible. The false color seems a bit more pronounced than in the ShortTube 80 but this may be a function of the greater aperture. Not an issue on DSOs.

DSOs:

M63 (Gx in CVn). M63 is virtually invisible from my house in the ST80. Rather easily detected in the SW102.

M104 (Gx in Vir). Certainly better than in the ST80. Far easier to detect the orientation and shape of the object at 111x
(Vixen 9mm Lanthanum & Ultima Barlow) .

M13 (GC in Her). Partial resolution with averted vision at 71x (7mm Pentax XL). My 6" Newt does a better job on M13 but the SW102 did a better job than expected. M13 is just a bright glow in ST80.

M4 (GC in Sco). Partial resolution with direct vision at 83x (6mm Vixen Lanthanum).

M57 (PN in Lyr). Far easier to detect the ring than in the ST80.

IC4645 (OC in Oph) - very nicely framed at 34x (30mm Celestron Ultima & Ultima Barlow).

Cr350 (OC in Oph) - rather tough in the ST80. Easily picked out with the SW102 at 23x (22mm Vixen Superwide).

Comments

If a person is looking for an inexpensive, 4 inch rich-field refractor, this is probably a good choice. It may not serve as a direct replacement for the ST80 since the ST80 is really extremely small and may be easily mounted on any Bogen tripod and head. However, the SW102 is certainly very compact and takes but a moment to set up. I'm very pleased with my purchase and feel comfortable recommending it to anyone who enjoys using this type of instrument. I certainly recommend Hands on Optics. Gary Hand is very pleasant and helpful.

Bill lives in Central Texas (30 degrees N) and has been involved in amateur astronomy for just over a year. Being retired, he reports, allows him to squeeze more mistakes into a shorter period of time. At the moment he has the following curious collection of instrument

Edmund’s Astroscan (the start of it all)
Orion ShortTube 80
Vixen 80mm Fluorite
Orion 6" Newt on SVD EQ
Sky Watcher 102mm refractor
Orion Argonaut 150 (Intes MK-67) - waiting to arrive

Bill has a self-confessed bias for small refractors but is working on expanding his biases to include any equipment that happens to strike his fancy.