Orion Expanse 15mm

Here is my short review of the Orion 15mm Expanse eyepiece. This eyepiece is of an Erfle design,it is not meant to be used with short/fast focal ratios. To get straight to the point the 15mm performs poorly in telescopes with short focal ratios (f/6 and shorter); however, if you have a refractor with a long focal ratio, like f/8, f/10,f/11.7, or f/15 this is the eyepiece for you. In the 4.5"EQ f/4 a lot of field curvature, astigmatism, and blurring is evident. This eyepiece came with the 4.5" EQ Orion. Like I stated earlier it is NOT an eyepiece to be used with telescopes with a short focal ratio. I wish Orion would supplement this eyepiece with something different for this instrument. An eyepiece designed to work with short focal ratios. In the 60mm f/11.7 the eyepiece performs well beyond what words can describe, especially for the price. The double cluster (NGC 869 and NGC 884) in Perseus fits easily in the FOV at 47x in the 60mm. The Pleiades Cluster fits in the FOV as well. The Orion Nebulae fits in the same FOV and the trapezium is split nicely and cleanly at 47x. A LOT of nebulosity is revealed with this eyepiece, especially for just 60mm of clear aperture. The views given are exquisite! This eyepiece also works well with a decent Barlow. I have split the double double with the 15mm Expanse and a 2x Barlow @94x in the 60mm f/11.7. I realize that is not all that impressive, but for 60mms of aperture it is a feat. This eyepiece also gives very good views of Jupiter and Saturn even when used with a Barlow. DSOs also appear sharp with a lot of contrast in the 15mm Expanse. M15 shows a lot of detail and M32 and M110 stand out nicely. This eyepiece shows a nice wide field of stars pinpoint across 95% of the FOV I would highly recommend this eyepiece to anyone wanting to upgrade a department store refractor or a scope with a long focal ratio(f/8 or longer). For the $49.95 price tag it is a good find. If used with a short focal ratio telescope though, the views will be disappointing. Overall rating in a short focal ratio scope: 4/10 poor Overall rating in a long focal ratio scope: 10/10 excellent

Pros

Excellent choice for long focus ratios.
Good price, Nice quality for the money.
Great wide views.

Cons

Does poorly in fast focal ratio instruments.

Rating

8/10