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REVIEW : Skywatcher 4" F500mm Refractor
4" SKYWATCHER Refractor on AZ3 mount. Focal length= 500mm.
This telescope is great for daytime use. The AZ3 mount along with the supplied erecting prism keep the orientation correct for land use. As an astronomical telescope it gives deep space views similar to my 4.5" Newtonian reflector, but with it's shorter focal length it shows a wider field of view with the same eyepiece.
The supplied 7x30 finderscope matches the finish of the main tube, and comes in an easily adjustable removable bracket. Two thumbscrews and one spring loaded brace make lining it up a snap. The focusser is metal, and will accept both 2" and 1.25" eyepieces (adapter included). The focusser travel can be locked in position if desired.
The Moon and brighter planets can be viewed, but their comparative brightness and the short focal ratio of the telescope produce some "false color", which appears as a purplish glow around them. With the use of filters you can eliminate the spectrum of light which doesn't come to focus with most of the colours. I use a Baader Fringe Killer, along with a Neodymium filter to reduce the green tinge brought on by the Fringe Killer. The resulting image is slightly dimmer and not quite true colour, but is noticably sharper than without the filters.
All in all this isn't a bad grab and go scope. The alt/az mount is more convenient for storage as opposed to an equatorial mount, and the views aren't bad for something so small. I am hoping to try some deep sky imaging with this it when I get the opportunity. It doesn't collect a lot of light, but it does cover a wider field of view at a lower power than a telescope with a longer focal length. Fellow enthusiast Bob used my DSI through his 4" 500mm short reftactor, and allthough the image wasn't very bright, on the first attempt spiral arms were just visible in M51.