BST 1.25" 58-deg UWA Planetary Eyepiece - 4mm
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- Designed primarily for planetary observation but great for deep sky objects too
- Wide 58 degree Field of View (FOV) in 2.5mm to 25mm focal lengths
- Comfortable eye relief averaging 16mm across the series
- Exceptional at nearly eliminating lateral color aberration and light scatter while retaining excellent sharpness, contrast and definition
- Modified Plossl design with five lenses in three groups (except for the 20mm which has four groups)
- In field use, perform as well as other, more expensive Orthoscopic and Plossl eyepieces
- Excellent fit and finish with fully multicoated lenses and flat black anodized internal baffles and field stop
Outstanding Planetary and Lunar Eyepieces
These BST 1.25" fully multicoated (FMC) eyepieces give maximum detail and definition across the entire 58 degree field of view (FOV). A great value, these eyepieces are exceptional at nearly eliminating lateral color aberration and light scatter often associated with more expensive eyepieces that are better suited for deep space objects. Though primarily made for planetary observation, these eyepieces still excel when viewing deep sky objects.
More expensive eyepieces that have similar wide fields of view need many exotic glass elements to achieve that wide view - as many as 9 lenses or more. More lenses mean more cost and more glass, which attenuates the amount of light you see. That also means there are more air-to-glass surfaces that can scatter light - reducing contrast and sometimes causing multiple reflections (ghosting) when viewing very bright objects such as the Moon and planets. Extra lenses can also mean compromises in the overall design that can often lead to other issues.One such issue of all that glass is lateral color aberration that appears as a cloud of false color around bright objects. Another issue is light scatter seen as a distracting halo or glow around bright objects. This can also reduce contrast.
Each BST UWA Planetary eyepiece has 5 lens elements in 3 or 4 groups. These eyepieces provide high contrast, no scattered light, and the highest possible definition.
Comfortable Eye Relief
The eyepiece eye relief averages around 16mm for the entire series. The 25mm eyepiece features 20mm of eye relief. Even the 2.5mm eyepiece has almost 17mm of eye relief! Experienced observers will truly appreciate such generous eye relief at significant magnifications.
Excellent Fit and Finish
These eyepieces are fully internally baffled and all internal spacers have antireflection microbaffles on their edges with flat black anodizing to reduce reflections. Every air to glass surface is broadband multicoated for peak light transmission and outstanding contrast on subtle lunar and planetary detail. The lens edges are blackened to eliminate internal reflections.
Each eyepiece has a flexible rubber fold-down eyeguard. Dust covers are provided for both ends of each eyepiece. A groove is machined into the nose piece barrel to ensure the eyepiece is less likely to fall out of the diagonal or focuser.
Please Note: While these eyepieces look similar to the TMB / TMB II ED eyepieces (and are also sold by some other sellers incorrectly under the TMB label), they are not the same as or copies of the 6-element TMB eyepieces. The factory making these eyepieces just uses the same external housing for the eyepieces.
| Free Shipping Graphic | Free US Shipping |
|---|---|
| Eyepiece Series | UWA Planetary |
| Focal Length | 4mm |
| Barrel Size | 1.25" (31.7mm) |
| Apparent Field of View (Mfg Specified) | 58° |
| Eye Relief (Designed) | 16mm |
| Filter Threads | Standard 1.25" Filter Thread (M28.5 x 0.6) |
| Coatings | Fully Multi-Coated |
| Lens Elements | 3 |
| Lens Groups | 5 |
| Blackened Lens Edges | Yes |
| Barrel Type | With safety undercut |
| Protective Plastic Storage Container | Yes - Free Agena Eyepiece Container |
| Protective Plastic Storage Container Size | Agena 52x80mm |
| End Caps | 2 |
| Rubber Eye Guard | Yes |
| Weight | 5.5 oz / 156 g |
| Country of Manufacture | China |
| Hide Found a better Shipped Price on Frontend? | No |
- Designed primarily for planetary observation but great for deep sky objects too
- Wide 58 degree Field of View (FOV) in 2.5mm to 25mm focal lengths
- Comfortable eye relief averaging 16mm across the series
- Exceptional at nearly eliminating lateral color aberration and light scatter while retaining excellent sharpness, contrast and definition
- Modified Plossl design with five lenses in three groups (except for the 20mm which has four groups)
- In field use, perform as well as other, more expensive Orthoscopic and Plossl eyepieces
- Excellent fit and finish with fully multicoated lenses and flat black anodized internal baffles and field stop
Outstanding Planetary and Lunar Eyepieces
These BST 1.25" fully multicoated (FMC) eyepieces give maximum detail and definition across the entire 58 degree field of view (FOV). A great value, these eyepieces are exceptional at nearly eliminating lateral color aberration and light scatter often associated with more expensive eyepieces that are better suited for deep space objects. Though primarily made for planetary observation, these eyepieces still excel when viewing deep sky objects.
More expensive eyepieces that have similar wide fields of view need many exotic glass elements to achieve that wide view - as many as 9 lenses or more. More lenses mean more cost and more glass, which attenuates the amount of light you see. That also means there are more air-to-glass surfaces that can scatter light - reducing contrast and sometimes causing multiple reflections (ghosting) when viewing very bright objects such as the Moon and planets. Extra lenses can also mean compromises in the overall design that can often lead to other issues.One such issue of all that glass is lateral color aberration that appears as a cloud of false color around bright objects. Another issue is light scatter seen as a distracting halo or glow around bright objects. This can also reduce contrast.
Each BST UWA Planetary eyepiece has 5 lens elements in 3 or 4 groups. These eyepieces provide high contrast, no scattered light, and the highest possible definition.
Comfortable Eye Relief
The eyepiece eye relief averages around 16mm for the entire series. The 25mm eyepiece features 20mm of eye relief. Even the 2.5mm eyepiece has almost 17mm of eye relief! Experienced observers will truly appreciate such generous eye relief at significant magnifications.
Excellent Fit and Finish
These eyepieces are fully internally baffled and all internal spacers have antireflection microbaffles on their edges with flat black anodizing to reduce reflections. Every air to glass surface is broadband multicoated for peak light transmission and outstanding contrast on subtle lunar and planetary detail. The lens edges are blackened to eliminate internal reflections.
Each eyepiece has a flexible rubber fold-down eyeguard. Dust covers are provided for both ends of each eyepiece. A groove is machined into the nose piece barrel to ensure the eyepiece is less likely to fall out of the diagonal or focuser.
Please Note: While these eyepieces look similar to the TMB / TMB II ED eyepieces (and are also sold by some other sellers incorrectly under the TMB label), they are not the same as or copies of the 6-element TMB eyepieces. The factory making these eyepieces just uses the same external housing for the eyepieces.
| Free Shipping Graphic | Free US Shipping |
|---|---|
| Eyepiece Series | UWA Planetary |
| Focal Length | 4mm |
| Barrel Size | 1.25" (31.7mm) |
| Apparent Field of View (Mfg Specified) | 58° |
| Eye Relief (Designed) | 16mm |
| Filter Threads | Standard 1.25" Filter Thread (M28.5 x 0.6) |
| Coatings | Fully Multi-Coated |
| Lens Elements | 3 |
| Lens Groups | 5 |
| Blackened Lens Edges | Yes |
| Barrel Type | With safety undercut |
| Protective Plastic Storage Container | Yes - Free Agena Eyepiece Container |
| Protective Plastic Storage Container Size | Agena 52x80mm |
| End Caps | 2 |
| Rubber Eye Guard | Yes |
| Weight | 5.5 oz / 156 g |
| Country of Manufacture | China |
| Hide Found a better Shipped Price on Frontend? | No |
BST 1.25" 58-deg UWA Planetary Eyepiece - 4mm