meteoblue SKY
| With SKY, meteoblue is building services for astronomers, meterorologists and other users who depend on a good forecast of sky visibility and atmospheric conditions during the coming days. SKY started in June 2009 by showing in p☼int+ the well known meteoblue astronomy seeing predictions from myMapServer for all p☼int locations. Further services will be added over time. Currently, the experimental astronomy seeing prediction can be accessed on myMapServer. Register / log in and navigate to "Astronomy Seeing". Select a location on the map, and click "Make Map". The seeing prediction for your selected location will be produced. Please be patient, as this may take up to a minute to compute. |
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Astronomy seeing prediction: Use instructions and tips
| Cloud cover is given in 3 different layers (0-4 km asl, 4-8 asl, 8-15 km asl, . Cover is given in Percent for the time of display. Percent integrates the volume of clouds and density of clouds which are expected to be present. Partial cover in 2 layers can result in total obstruction of sky visibility, due to cloud overly. For high clouds, partial cover can results in total interception of star visibility. In very high mountains on altittude above 4000 m asl (average of the surrounding), the lower loud layer forecast will be empty and should be ignored, since it is only relevant for valley laying below 4000 m. Seeing1 and Seeing2 are two different models to calculate visibility, and are independent of cloud cover. They only represent the visibility through assumed clear portions of air, and differ in the way how atmospheric density gradients influence visibility. Seeing2 gives more weight to the effect of density fluctuations, and is more likely to indicate air "flickering" due to turbulence. Seeing does NOT include the cloud cover. It is possible that no observation is possible with a seeing index of "5", if cloud cover is 100%. Conversely, it is possible that there is no cloud cover 0% (and all stars are "visible"), but observation is severely reduced by low seeing index ("1"), due to air turbulence. Note: There are 2 reasons for not including the cloud over in the seeing index calculation: 1. Seeing is a state of the air - it is therefore independent of cloud cover. 2. Sometimes, clouds are sparse, and then observations can be made between clouds. In this case, it would be very difficult to set a "limit" for cloud cover which influences the Seeing Index and satisfies all users. High jetstream speeds (>35m/s) usually correspond to bad seeing, as well as very low speeds (<5m/s). More information can be found on: http://en.wikipedia.org/wiki/Astronomical_seeing. Bad layers are the atmosphere layers in which turbulence is producing disturbance of air and particles, and thereby influencing the astronomical "Seeing". These indication should help you identify if the turbulence is above or below your observation spot. |
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Arcseconds
Arcsecond is unit of angular measurement equal to 1⁄3,600 of a degree, or 1⁄1,296,000 of a circle
To estimate seeing, arcsecond can be used to estimate the minimal size of an object which is still visible using telescope aimed at the open sky, expressed as an angle.
The arcsecond measures shown are based on "Seeing 1", "Seeing 2" and "Bad layers", and do therefore not directly correlate with each parameter.
To estimate seeing, arcsecond can be used to estimate the minimal size of an object which is still visible using telescope aimed at the open sky, expressed as an angle.
The arcsecond measures shown are based on "Seeing 1", "Seeing 2" and "Bad layers", and do therefore not directly correlate with each parameter.
Basic information about calculations