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| This sky is completely cloudy and very tricky. It appears to have open spaces in the sky, yet the spaces are all covered with obstructions. There are large amounts of upper atmospheric haze in addition to clouds closer to the ground. At the top, thousands of small clouds have gaps which are changing too fast and are too small for reliable telescope observations. It is possible to observe directly through the haze and apply methods to subtract the haze when the photo is taken or after through software image processing. |
We talked about telescope observing through holes that appear in clouds and then we heard the expression "Sucker Holes" used. Surprisingly the term is real and can apply to both astronomy and aviation.
Sucker hole is a colloquial term referring to a short spate of good weather that "suckers" sailors into leaving port just in time for a storm to resume at full force. It can also refer to breaks in cloud cover, which lead astronomers into trying to make observations, only to have the cloud close in again.
A sucker hole is an unsuccessful observation break in the clouds. Maybe an opening is seen, the telescope is set up, and by the time the telescope is ready, the hole is gone! To deal with the phenomena, the rate of change in position of the cloud is measured per unit time and this can determine how much time might become available for the clearing to remain open before changing. Typically high level atmospheric clouds can move at speeds up to 1,000 mph and bring about changes in only 20 minutes or less. Meandering cumulus clouds can also bring about short term changes just when you least expect it. Upper atmospheric haze is more tricky and can affect celestial objects as if they are being viewed through a thick filter. This may in some instances help when looking at the Sun, Moon or bright planets. On the other hand, contributory dimming of the object, added water vapor, and particles held in suspension may ionize and polarize the region, absorbing, blocking, and scattering light, thus degrading the image.
Astroimaging Through Cloud Cracks & Holes
