Burgess/TMB 6mm Planetary

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Brand and Model:	Burgess/TMB 6mm Planetary
Price ($USD):	$99
Type:	Planetary
Focal Length:	6 mm
Barrel Size:	1.25
Apparent FOV:	60.0 degrees
Field Stop Dia.:	0.0 mm
Eye Relief:	16 mm
Elements:	6
Weight (lbs):	5.8
Description:	Wide angle, long eye relief planetary

Vote Highlights

Burgess/TMB 6mm Planetary

My two or three cents to the 6mm TMB/Burgess planetary. I've got the garage sale version from end of 2005, 49$ or here in Germany 65Euros. First thing I did with, I replaced it with the new microbaffled fitting-ring which was delivered as a spare part with the EP. The field is large enough (~18') to watch Deep-sky objects easily with my light-weight 10inch f/5 truss-Dobson (f=1252mm) and the field is sharp to 90% to the edge, then coma comes in (from the mirror). There is a tiny bit of false color just at the edge of the field, but it is OK, it's not an issue. There is no ep-astigmatism! Eye-relief is enough for me, as I didn't wear my glasses when observing (about 14-16mm stated at the Burgess info-page).
The only thing which is really annoying is the very bright and broad reflection when observing the moon. This optical design has a big issue with internal reflections on very bright objects (read more about that on the Brayebrook Observatory site of Chris Lord). Jupiter is behaving better in the ocular.
But for looking at other things like nebulas or galaxis or star clusters, it is a very good and very sharp eyepiece. I like the adjustable eyecup, I like the decent coatings, but I don't like the safety groove/undercut on the barrel, because I use a HC-2 focuser on my 10inch Dobson with a 1,25inch reduction, which has a locking ring. This combination always tends for complications, taking the eyepiece out of the adaptor without losing the object to watch, because the edge of the undercut could got caught by the clamping-ring.
The backfocus of the ep is in the normal grade, about +2 or 3mm. From stopping the drift time of a star (arcturus, alpha Bootis, time was corrected for declination by using t*cosine dec) through the Field of View on a parallactical mounted 1200 mm (f/8) TAL2M 150mm Newton, I measured an effective fieldstop diameter of 6.6mm, this gives around nice 63Â° AFOV.
I judge this ep just fine for the money.
Randolf K., Germany

Overall Rating: 8
Optics:7 Value:8
Weight: 5 (Veritable Vote)
Date: 06/07/2006 08:32:07 am PST
By: Randolf
Link to this vote: http://www.excelsis.com/1.0/displayvote.php?voteid=508235

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