Lunt Terrestrial Star Diagonal
Erect Image Views For Daytime Terrestrial Use
These are 1.25 inch prism diagonals that Lunt supplies for daytime and terrestrial work rather than for solar observing. The 45 degree unit uses a full size Amici prism to give a fully corrected image, left to right and up and down, which is what you want for reading distant signs, watching birds, or scanning a landscape through a refractor.
The 45 degree angle also sits at a comfortable head position for horizontal targets, where a 90 degree diagonal forces you to crane your neck. The GSOPD90 covers the other case: a conventional 90 degree prism for night time astronomy and for terrestrial targets high above the horizon, giving an up and down correct, left to right reversed view.
Both use full size prisms so the field stays fully illuminated and free of vignetting. Neither of these diagonals is a solar filter and neither makes a telescope safe for the Sun. Point a telescope at the Sun only when the correct certified solar filtration is fitted at the front of the instrument or in a dedicated Lunt solar system.
Key Features
- Fully Corrected Image - the GSOPD45 Amici prism returns a left to right and up and down correct view for terrestrial targets.
- Comfortable Angle - 45 degrees puts your head in a natural position when the target sits near the horizon.
- Classic Ninety Degree - the GSOPD90 prism suits night time astronomy and high elevation daytime targets.
- Full Size Prism - the prism is large enough to illuminate the whole field, so there is no vignetting at the edges.
- Standard Fitting - 1.25 inch barrel and 1.25 inch eyepiece holder work with refractor and Cassegrain telescopes.
- Solar Warning - neither diagonal filters sunlight, so the telescope must supply its own certified solar filtration.
| Specifications | |
|---|---|
| Type | 1.25 inch prism star diagonals for terrestrial and night time use |
| Model / SKU | GSOPD45, GSOPD90 |
| GSOPD45 angle | 45 degrees, erect image Amici prism |
| GSOPD45 image orientation | left to right correct and up and down correct |
| GSOPD90 angle | 90 degrees, prism |
| GSOPD90 image orientation | up and down correct, left to right reversed |
| Barrel and eyepiece fit | 1.25 inch on both models |
| Prism size | full size, delivering a fully illuminated field with no vignetting |
| Telescope types | refractor and Cassegrain |
| Recommended use | terrestrial observing; the GSOPD90 is also suited to night time astronomy |
| Prism coatings | Not published |
| Clear aperture | Not published |
| Solar safety | not a solar filter; solar viewing requires certified solar filtration on the telescope |
| Shipping weight | 2.0 lb each |
| Warranty | 5 years from date of purchase, original purchaser, manufacturing and workmanship defects |
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