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Eyepieces still available!
Sorry for the delay in response, recuperating from a fall lately. Here's a little more information on the eyepieces:
1) XP3.8
Eyepiece Focal Length: 3.79mm
Element Placement/Design: 3 groups, 5 elements
Weight: 40g
Eye relief: 2.7mm
Barrel Diameter: 24.5mm (0.965")
2) XP8
Eyepiece Focal Length: 8.02mm
Element Placement/Design: 5 groups, 6 elements
Weight: 50g
Eye relief: 2.1mm
Barrel Diameter: 24.5mm (0.965")
The Pentax XP eyepieces were originally designed for eyepiece projection photography, and hence have superb 45 deg FOV flat field performance. They have been increasingly used for visual planetary/lunar usage and is a lower cost alternative to the prohibitively expensive ZAO I and IIs collection. For those looking for long eye relief performance, these are not what you should be getting, but they are IMHO usable without glasses and are valued based on their extreme sharpness and high contrast performance. They perform very well as planetary eyepieces on scopes beyond 2000mm (mewlons, etc) without the need for barlow lenses. Coatings on these eyepieces are exceptional, and there is little or no light scatter compared to the cheaper Tak Hi-orthos and UO orthos. Excels in light transmission throughput as well compared to equivalent eyepiece designs. From what I have heard elsewhere, these eyepieces have been used extensively in star testing in Astrophysics and personally been used frequently by the late Thomas Back master optician. Hope this helps in your decisions!
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