zen99c2
50,8mm-es zenittükör 99% reflexióval, dielektrikus védőréteggel, L/10 PtV
Marke: Castell
Csatlakozás: 50,8mm
Reflexió: 99%
Eltérítési szög: 90°
Versandgewicht: 1kg
EAN Code:
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139.90 EUR
(inkl. MWSt)
Perhaps the lowest price in Europe ...
... for a dielectric zenith mirror with 99% reflection?
99% reflection and long life
Thanks to dielectric (non-metallic) coating, the Castell zenith mirror not only has a high reflectance of 99%, but also a long service life. The long service life is achieved because the non-metallic dielectric surface reacts much less with the acids and bases in the air than an aluminum coating with a quartz protective layer.
Ring clamping instead of fixing screws
The 50.8mm socket of the diagonal itself, as well as the 31.7mm reduction have ring clamps with large knurled screws.
Test: checking the reflection
Test procedure: Take a test photos
with a camera through the diagonal (ISO200, manual mode), then measure
the brightness value in Photoshop using a histogram.
This test serves as an estimate of the zenith reflection. The following models were tested:- LACERTA
(nominal value:99%)
Measured: Luminance = 98.9% Green / Visual = 99.2%
(Very high
reflectivity in the entire RGB range, but also the most expensive zenith
mirror in this test series. It is identical to other well-known models)
- SkyWatcher
(nominal value:99%)
Measured: Luminance = 96.1% Green / Visual = 95.3%
(evenly in the entire RGB range, but shows less reflectivity than advertised both in luminance and in green / visual)
- Castell
(nominal value:99%)
(Visually, it
reaches almost 99%; in the blue area, however, a little less
reflectivity and therefore a slightly yellow tinge; but is advantageous
for Fraunhofer refractors with blue halos)
Measured: Luminance = 95.3% Green / Visual = 98.2%
- SkyWatcher
(nominal value:91%)
Measured: Luminance = 90.3% Green / Visual = 92.4%
(As
advertised, a good zenith mirror without higher reflectivity criteria.
The image is, however, much darker than in the other three zenith
mirrors)
