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Edmund Astroscan



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Date: 7-31-2001 corrected and re-posted 12-29-2001
Price: approx $299
Design: 4.5 inch hand hold able reflector operating at f/4.2
Description: Small reflector that includes a 28mm RKE eyepiece.

The Review with Corrections from the Original

It seems this wonderful 'scope is passing by the wayside. [NOT TRUE, ES has no plans to stop selling the Astroscan] Too bad. It has a very wide field of view, is stable, portable,
easy to set up, requires no collimation or other maintenance, is inherently apochromatic (all newts are), is very intuitive to use, and has excellent optics.

The 'scope currently sells for $299 (4-2001), and includes the OTA, mount (though you'll want a tripod too... it can be adapted to fit most camera tripods), a 28mm RKE eyepiece, and a simple peep site. (The peep-site is way low-tech, but works perfectly.) It's a Newtonian, focal length is 445cm, apture is 4 1/4" (105mm), size is ~17"x10"x10", weighs ~11 pounds ('scope and base).

The mount is a "ball and socket" mount. The mechanics are immediately obvious when you see a pictuure of the 'scope at One of the nice perks of this mounting system is that it allows the scope to be rotated to any angle, even with the target
in sight, which means the eyepiece is always placeable at a convenient angle; something that is not possible with most other 'scopes. It's very easy to point, and very stable/well balanced, and tracking is easy. It was released sometime near 1976, and has been in production continuously, un-revised, since then. That's quite a testimonial!

Optics and collimation are said to vary in quality from instrument to instrument. As collimation is permanent, a mis-collimated 'scope must be exchanged under the 5 year waranty. Mine ,an older one, is opticly excellent and perfectly collimated. As the mirror is permanently installed, it is not capable of re-coating [NOT TRUE, Edmund can re-coat your mirror], should the mirror show oxidation. I asked Edmund via e-mail if they offered any help in this regard, and never recieved a response.

The views are bright and sharp, with very little edge of field distortion. There is coma, as in all short focal length Newts, but I find it unobjectionable. The 'scope often gets a bad rap because it's short focal length makes powering the 'scope tough (I use a 7mm Nagler and a 2.5x Powermate). But, for most targets the attainable power is adequate. Like most small, short focus 'scopes, it's power is maxed at ~130x, which is just enough to resolve some detail on planets, split fairly close doubles (I can split the Double Double fairly easily), and resolve pleasing detail in most Messier's (M13 looks granular, M27 has whisps on the ends of it's dumbell, M82 shows texture and a dust lane, the Ring Nebula easily shows it's anularity...) The addition of a UHC or OIII filter helps tremendously on nebulous objects. At lower powers, its 3 degree+ field is a beauty to behold. I must mention that premium EPs seem to make quite a difference at higher powers.

The focuser is the weak link. It's a friction-fit tube that is moved in the focuser by a rubber cylinder which rotates when the focus knobs are turned. There is no set screw to hold the
eyepieces in the tube, rather, it uses small springly flaps, which means that some ep's, fit quite loosely (my Meade 26mm Super Plossl fits loosely, the rest are fine). Without lubrication, the focuser always seems to skip perfect focus. Most people end up doing coarse focusing with the knob, and fine focusing by sliding the ep up or down a little in the focus tube. I used a bicycle chain lubricant called "White Lightning" on the tube. The lube consists of paraffin particles suspended in alcohol. I removed the focus tube and applied the lube with a cotton swab, on the side away from the roller, and allowed the alcohol to evaporate. This fixed the problem completely, though the treatment is not permanent. Cleaning the rubber roller with
alcohol seems to help, too. I have no trouble with fine focus after the lube.

In general, I feel a 6" dob is the best starter, and/or quick look second 'scope. But, the Astroscan is more portable, basically maintenance free, easier to use, and is the least
intimidating 'scope around. I have several 'scopes: ETX90, C102, Celestar 8 Deluxe, and 6,8,10 & 16" Dobs. The 'scope, tripod, base, 4 eyepieces (with a Barlow and filters) a red LED light, and Tirion's Bright Star Atals all fit nicely in one small package that can be taken nearly anywhere, including on a plane in the overhead compartment. After the fuss of larger apertures, it's pleasing to walk out the door with a single small duffel bag that contains
everything I need for a night of enjoyable star gazing.

It's a pleasure to pick off Messier after Messier simply by eyeballing the general location of the obejcts and scanning the area with a 40mm EP. The Astroscan is my most often used
'scope, which, according to conventional wisdom makes it my best 'scope. Absolutely love it! Highly recommended.

Submitted by "k" - - USA

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