Televue have always been known for their fine eyepieces, the head of the company Al Nagler is a keen astronomer himself, this love of astronomy is what sets Televue apart from it’s rivals. Rather than just churning out eyepieces in the pursuit of profits Televue take time and care that results in an end product that might be a little more expensive than some but is definitely worth those extra pennies.
Televue have stayed true to typical plossls using 4 lenses (or elements as they’re known) in a symmetrical design, that is two groups of two lenses. Using the fewest number of lenses in an eyepiece often means a clearer and sharper image quality, with less glass to potentially distort any object through the eyepiece. The down side of using so few elements is that it produces a smaller field of view than a similarly focal lengthed eyepiece with more lens elements. The 15mm Plossl has a rather small 50 degree field which is okay if you own a clock drive to automatically move your telescope but if not the constant readjustment and manual movement of the telescope to keep the object in view can become a little tedious. As well as being annoying it stops you from focusing 100% of your brain power on observing, this may sound strange but it really is true, when you’re not holding back some of your brain for manual tasks you can actually observe fainter details in objects.
Thankfully the optical quality of the 15mm more than makes up for the small field, Televue use a fine and even coating for their lenses and a high quality glass to get the maximum amount of light through that eyepiece and into your eye. There are no optical flaws, scattered light or other such aberrations to spoil your observations.
As well as being impressive optically the 15mm has a pleasing eye relief for a plossl of this focal length and is around 10mm. The field stop diameter is just under 13mm and makes for comfortable viewing.
I use the 15mm on two telescopes, an f8.3 120mm refractor and a 300mm f5 Dobsonian, the eyepiece performs at it’s best in the Dobsonian. Images stay sharp throughout the field with no degradation even in the outer reaches of the fov.
A definite recommendation, optically brilliant whilst still being comfortable to look through. Worth every penny of it’s £70 price tag!