Surplus Shed Erfle 47mm

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Brand and Model:	Surplus Shed Erfle 47mm
Price ($USD):	39.50
Type:	Erfle
Focal Length:	47 mm
Barrel Size:	2
Apparent FOV:	45.0 degrees
Field Stop Dia.:	35.0 mm
Eye Relief:	20 mm
Elements:	5
Weight (lbs):	0.75
Description:	Surplus Shed Description: This is the second in our 2 inch 5 element erfle design series. We used surplus optics to build these. Some elements originally cost our government hundreds of dollars each. Fits standard 2 inch telescope focuser. Coated optics. 60 degree field of view, 20mm eye relief, and 35mm clear exit aperture. Super eyepiece for the price. Unused.

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Surplus Shed Erfle 47mm

I purchased this eyepiece for use in my 5 inch F 9.3 refractor. I found it to be an excellent performer giving sharp bright images to the edge. The field and eye lens measure 35mm, with a useable field of 45deg. I found no problems with eye position or "black out" when used with my refractor. In fact I found it a very comfortable to use eyepiece. Although the apparent field may not be as wide as advertised, it nevertheless covers a big chunk of the sky with its long 47mm focal length. Almost 2 degrees of sky entering your eye at 25x in a 1200mm focal length instrument is nothing to complain about for an outlay of $40!

Overall Rating: 9
Optics:8 Value:10
Weight: 1 (Unreliable Vote)
Date: 05/14/2004 04:49:41 pm PST
By: Anonymous (xxx.xxx.253.9)
Link to this vote: http://excelsis.com/1.0/displayvote.php?voteid=359674

Reply Replies: 0

Surplus Shed Erfle 47mm

This eyepiece promises to deliver the widest true apparent field of view (AFOV) possible in a 2 inch barrel due to its claimed 60 degree field. In fact, I found the field to be closer to 45 degrees. Certainly less than a typical plossl of 50 degrees AFOV. The problem appears to be due to an undersized field lens.

The actual image it presents is fairly sharp across what field is there, though not as sharp as an Orion 32mm Sirius plossl, for instance. Wider for certain, but not sharper despite the narrower AFOV. Eye placement is tricky due to the long eye relief of 20+ mm and narrow field of view. Blackout was difficult to avoid compared to other designs such as Rini's MPL.

I decided to return it and wait to see if they correct the design to yield a true 60 degree AFOV.

Overall Rating: 7
Optics:8 Value:6
Weight: 1 (Unreliable Vote)
Date: 11/19/2003 06:10:59 am PST
By: Anonymous (xxx.xxx.253.65)
Link to this vote: http://excelsis.com/1.0/displayvote.php?voteid=320215

Reply Replies: 0

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