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Sky-Watcher 150 f5 refractor

Started by David Simons, 07/15/2004 08:59AM
Posted 07/15/2004 08:59AM | Edited 01/12/2007 03:55PM Opening Post
Sky-Watcher 150 f5 refractor

I just received this scope a few weeks ago, and finally had a chance to use it a little.

Mechanicals: Very front heavy, I had to remove the heavy dew shield to get it to balance on my Quickset photo tripod. The scope is heavier than it looks at around 13lbs, and is really the limit of this tripod. The tube without the dew shield is very short. It almost does not look like a "classic" refractor. I like this OTA format, as tilting the tube does not require too much raising or lowering of the tripod. The coatings were OK, a little brighter than I would have liked, not stunning or nearly invisible like a Tak or AP. No streaks or anything like that, just a little bright. The lens cell is not adjustable (see concerns below) The focuser is a typical 2" Synta type, lightweight, but functional. The lens cap has a nice large secondary cap that gives about a 4" opening for better color correction at the expense of aperture.

Optical: To cut to the chase, the views are sharp, but start to show color after about 75X. I was very nervous the collimation would be off since the lense cell is not adjustable, but the in and out of focus images were nice and round, so far so good. I tried to get diffraction rings, but could only get a hint of such things around 125X, the highest power I tried that night. Other refractors I have used such as a Vixen 4" f9 fluorite showed a beautiful 1st ring around 200X. Since I really bought this as a wide field scope I wanted to know if I could get tight star images at the 25-60X range I was planning to mostly use this scope at. No problem here, I used a 27mm Panoptic which gave a stunning 2.4 degree 27.8X wide field sharp to the edge view. The stars focused to pinpricks and many dim little stars popped into focus at the sweet spot. The Cygnus region was filled with stars and large clusters. The bright side of the Veil was obvious without a filter. One of my favorite large open clusters, NGC6940 near the veil was glittering with faint pinpoint stars. I wanted to see where the scopes color error was starting to be objectionable, and at around 100X, the purple halo starts to be fairly obvious. I tried to reach Vega, but the tripod I was using did not want to reach the zenith, so I settled for Deneb. Stars were still very sharp at this magnification.

A scope like this is kind of a niche instrument. It allows for sharp very wide bright field of views. Big clusters and star clouds are it's game. Large dim structure that is only hinted at in binoculars become star filled swathes of sky. Extreme low powers like this sometimes don't work as well with similar size newtonians, as the secondary mirror needs to be full size to get good field illumination, and the obstruction can start showing a shadow at the lowest powers. The Sagittarius region will be a treat this summer. These type of scopes may be for the refractoraholic only, but I am curious to see how wide a field I can get before my exit pupil starts to clip the entrance aperature. Anybody have a 35mm Nagler ? smile

David Simons

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David Simons
Posted 07/15/2004 03:22PM #1
David, everything is good in my 6" F5 newt with a 22Nagler, and Jupiter looks good at 200x to boot. Not all 6" F5 newts are bad.

Congrats on the scope. It is an excellent quick look with the size to really do some work.

Clear Skies,
Posted 07/15/2004 09:38PM #2

Goes to show you that a 6" f5 achro has its uses. I'll bet it is a sweet wide field scope.

clear skies,

Larry Citro