Small Scopes

Eyepiece Comparison: Premium Zoom vs. $8.95 Cheapie

Here's an eyepiece comparison between an apple and an orange, but interesting nonetheless.

As discussed in earlier posts, my Pentax 65mm scope is often packaged and sold with the Pentax XF Zoom eyepiece. The XF Zoom is sold at a premium price (roughly $250 street), and generally receives solid evaluations. Now, a match-up with the extreme opposite in price. Adorama.com is selling the Celestron 10mm SMA (Super Modified Achromatic) eyepiece for $8.95 plus shipping. This makes it essentially the cheapest 1.25" eyepiece on the market.

I purchased the Celestron SMA thinking it would serve as a "poor quality benchmark" to counterbalance the XF Zoom as a "high quality benchmark," but things didn't turn out exactly as I expected.

The XF Zoom results in 20x to 60x power in the Pentax 65mm scope, and the fixed power SMA falls right in the middle at 39x. Here's a comparison of the two:

Field of View

• XF Zoom: Feels fairly wide at all magnifications, it's easy to find objects at 20x.
• SMA: Relatively narrow and tight, requires substantial hunting to find a target.
  

Image Clarity

• XF Zoom: Sharp at 20x with slight chromatic fringing, remains sharp through 40x. Gets progressively worse beyond 40x and resolves less detail at 60x than 40x.
• SMA: Very sharp, minimal color fringing, resolves slightly greater detail than the XF Zoom at any magnification. Stars and lights are round and well defined.
  

Eye Relief

• XF Zoom: Good 15mm relief at 20x makes it comfortable for basic scanning. It shrinks to 11mm at 60x, which feels as if the eyepiece is declining in performance. Actually it's pretty decent unless you wear glasses. The fancy screw up cover allows precise eye positioning.
  
• SMA: Terrible eye relief. It's an eyelash tickler. The cheap rubber eyecup folds down for a little more room.
  

Apparent Brightness

• XF Zoom: Very bright at 20x and still quite usable in low-light at 60x. It creates an unnaturally bright image in some situations.
  
• SMA: Not as bright as the XF Zoom at low magnification, but always usable.
  

Comments and Conclusions

• XF Zoom: I greatly prefer this eyepiece for locating objects and casual browsing that involves near and far objects. The zoom feature is often worth the lack of clarity at high magnification.
• SMA: This stomps the zoom for extended viewing of stationary targets. The narrow field of view makes it less than ideal for general use.

posted by Tako John @ 8:09 PM