Description
This compact device contains three different sensors that provide complete information about the current ambient conditions. The field of view is about 30 degrees, so the multi-sensor needs to be mounted in such a way, that there will be no obstacles in its field of view (like for example dew cap).
3 in 1 multi-sensor is supported by AstroLink 4 mini II, AstroLink 4 micro, AstroLink 4 Bee, and AstroLink 4 Pi. Parameters read from this sensor are exposed in the ASCOM Observing Conditions interface and in the INDI Weather interface.
The following values are measured and calculated by a 3-in-1 multi-sensor:
- temperature
- relative humidity
- dew point temperature
- sky temperature
- cloud coverage
- sky brightness
Each of these measurements is described in detail below.
Mounting dovetail can be small, Vixen standard or finderscope shoe standard.
Temperature/humidity
Temperature and humidity sensor provides measurements of two values:
- relative humidity accuracy: 2%
- temperature accuracy: 0.3C
Additionally, the dew point temperature is calculated and displayed.
If you choose the temperature sensor index to be secondary, then read values will be presented in the #2 column in the panel, the sensor can be used for focuser compensation, but temperature and humidity will not be available in the ASCOM driver. Only primary temperature sensor readings are available in the ASCOM driver.
Alternatively, you can order this multisensor without a temperature sensor inside, so you can purchase a temperature sensor separately and place it in a convenient location in your setup.
Sky temperature/cloud coverage
Sky temperature seems to be an abstract value, but this is quite a good indicator of current conditions. Even under a dark sky far away from light pollution, when high clouds are present, the sky background meter may show very low values. However high clouds will affect astrophotography significantly. The sky temperature sensor will detect high clouds as well as any other clouds, fog, haze, and similar obstacles in the air.
Sky temperature is the measured value, but the informative value is the difference between the sky temperature and ambient temperature. If there is no difference it indicates 100% clouds or dense fog. If the sky temperature is 20-25 degrees lower than ambient, it means very few obstacles in the air, so the transparency should be good.
This sensor can also be used for contactless temperature measurements of any object (like house walls, radiators, floors, etc).
Technical data:
- ambient temperature range: -40C … +50C
- sky temperature range: -70C … +380C
- field of view: 30 degrees
Sky brightness
The read values are presented in the AstroLink panel as sky brightness expressed in magnitude per square arc second, and also as estimated NELM – naked eye limiting magnitude. The actual reading may differ from other commercially available devices in terms of the offset. But the relative changes will be presented correctly. The sky brightness value is can be also displayed by any software that uses the ASCOM Observing Conditions interface (like Sequence Generator Pro or N.I.N.A.). Depending on the sky brightness the update time may vary from a few seconds (bright sky) up to 2.5 minutes (very dark sky).
You may accurately calibrate the sky brightness sensor yourself. Here is a simple tutorial.
The operating range of the sensor is 16.00 – 22.50 mag / arcsec2. Values outside the operating range are also displayed in the panel, but accuracy is getting low in this range.
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