Weather: Cerro Tololo

Updated about 11 minutes ago (24 November 2017 07:05 UTC)

Current status: Open/ Ready to open

Air Temperature and Dew Point

A plot showing the temperature and dew point

Latest Values

Air temperature
(Acceptable range: -20.0°C to 40.0°C)
Dew Point-8.9°C
Temperature - Dew Point
(Lower limit: 2.0)

This graph represents the current air temperature and dew point in degrees Celsius. When any of the values on these two lines approach or cross their maximum thresholds, horizontal yellow lines will appear. Similarly, if any of the values approach or cross their minimum thresholds, dark blue lines will appear. The dashed cyan line represents the values derived from subtracting the values of the dew point curve from the temperature curve. The threshold associated with this line will appear as a dashed dark blue line when any of the values cross or approach their minimum threshold for the allowed difference between the temperature and dew point. If any of these three lines cross their maximum or minimum thresholds it indicates that it was unsafe to open the dome at that time.

Barometric Pressure

A plot showing the barometric pressure

Latest Values

Barometric Pressure626.7 mmHg

Barometric pressure, also called atmospheric pressure, is a measurement of the force per unit area exerted against a surface by the weight of air above that surface from the atmosphere. Generally, the higher in elevation a surface is, the less barometric pressure it will have.

Relative Humidity

A plot showing the relative humidity

Latest Values

Relative Humidity
(Upper limit: 92.5 %)
21.2 %

Download data

Relative humidity is a percentage representation of the amount of moisture present in the air. If a yellow horizontal line appears at the top of the graph, this means that one of the data points in this time range came within 10 percent of, or surpassed, the upper limit threshold of the amount of moisture acceptable to open the telescope dome safely.

Wind Vector

A plot showing the wind speedA plot showing the distribution of wind speeds and directions

Latest Values

Average Wind Speed
(Upper limit: 15.0 m/s)
1.14 m/s
Average Wind Direction152.0°SSE

The wind speed is measured in meters per second. If a yellow horizontal line appears at the top of the graph, this means that one of the data points in this time range fall within 10 percent of, or surpassed, the upper limit threshold for the max wind speed acceptable to open the telescope dome safely.

The wind rose plot represents the wind data grouped by speed and direction from North. Each of the 16 triangles represents the percentage of the data that came from a specific direction. The color represents the speed, and the size of the color bar represents what percentage of the wind data was recorded at that speed.

Sky Brightness

A plot showing the overall solar power and sky brightness

Latest Values

Solar Power
(Upper limit: 140.0)
0.0 W/m²
Sky Darkness21.59 mag/arcsec²

This graph shows the total sky brightness represented by the solar power collected from the pyranometer sensor and what can be called 'sky darkness' measured by the sky quality meter. Solar power is the amount of power (in Watts) collected from light falling on an area of one square meter. This line is drawn on a logarithmic scale. When the points on the graph drop to values of zero on the y-axis, this usually indicates that the sun has passed below the horizon. If a yellow horizontal line appears, this means that one or more of the data points is within a ten percent range of, or has surpassed, the upper threshold for how bright the sky can be and it is unsafe to open the dome.

Sky darkness is measured in magnitudes per arcsecond squared and is graphed on a linear scale. Although this measurement is formally known as sky brightness, it is often more helpful to think of it instead as sky darkness because the values increase as the sky gets darker, and decrease as it gets lighter.

Cloud (Sky - Ambient Temperature)

A plot showing the overall sky temperature

Latest Values

Sky - Ambient Temperature
Sky - Ambient Temperature 2
Dew Point-8.9°C

The purple line in this graph represents an average of the sky temperature data taken from two of the Boltwood sensors. The sky temperature will generally increase when there are clouds present, indicating that the viewing conditions may not be ideal. It is currently graphed against the dew point to show the amount of moisture that may also be present in the sky.

Observatory Status

Live Site Camera

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