Tuesday, October 16, 2018

Let Us Now Praise Great Bargain Eyepieces

I think I mentioned the struggle I was having getting my 35mm Plossl sufficiently in focus.  The obvious solution was another low power eyepiece with less in focus.  So I bought this Russell Optics 50mm 2" eyepiece:
Okay the stick on label is cheesy, but it cost me less than $80 delivered.  Wondering what 2" means?  You are obnviously not an amateur astronomer.  Telescope eyepieces come in three common barrel diameters: .965" (an older Japanese standard), 1.25" (the American standard), and 2.00".  The larger eyepiece gives a really glorious feel of looking through the spaceship's portal.  In addition, Televue (an American maker of very fine optics) has produced a great many very wide field eyepieces in 2" format. However, these are eyepieces which are priced accordingly (hundreds of dollars for something that a few amateurs compare to a grenade in mass and dimensions).  

Enough with the tangent.  A 50mm eyepiece gives 18x in my 5" refractor, and 40x in the 17.5" reflector.  So why would I want a low magnfication eyepiece?  The field of view gets larger as the magnification drops.  If you are hunting for low surface brightness, large area objects (like galaxies) a wide field is very useful.  In the refractor this eyepiece gives a 2 degree field of view.  Even in the reflector  this is a .875 degree field.  And objects like the Moon are crisp and beautiful against the inky blackness around it.  My wife was enchanted by how much more AWESOMITUDE this eyepiece gave on the Moon (sorry for breaking into surfer English; I grew up three blocks from the Pacific).

I bought this because some years ago, Russell Optics sold an 85mm cousin at a bargain price.  At the time they said it was a prototype that they had made to decide whether to do these commercially.  It has an acetal barrel which greatly reduces its weight.

As with any long focal length eyepiece, they work great in refractors, but until it gets dark, the central obstruction of the diagonal mirror produces a very noticeable black spot in the field of view.  They warn you about this.  It is a minor nuisance until it gets dark, at which point the dark spot goes away.

Now, what I do with old 50mm eyepiece?  It has no brand name or markings on it.  It is a brass barrel and weighs 15 ozs.  (That weight makes it a bit clumsy on my telescopes because it alters the balance a good bit.)  If it could talk, I suspect that  it would tell stories of sinking Japanese destroyers.  It has the look of something war surplus.  It was one of eyepieces that came with the bargain 17.5" reflector I bought at a Boise Astronomical Society auction some years ago.

Any ideas how to chase down its lineage?

 The  number stamped into the top is 233061-9.

No comments:

Post a Comment