Lunar Photography-Keeping ourselves out of trouble;) hahahaha…not really:)
Photography, both Mike and I have a passion for what we do, his type of photography is far more difficult than mine. I can grab my camera and pop out to shoot a sunset or some amazing flowers, or sit quietly and wait for the hummingbirds (it is good for the soul, this patient waiting) Mike well, he has to set up his telescope, that is an effort in itself….
First it, the telescope, I don’t think it has a name;) has to be rolled out of the pass through storage on finger pinching ramps, speaking from experience, provided it is even a clear cloudless day/night. Then assembled, not too much of a chore, he waits until dark and starts to check the conditions. It is an 18″ Starstructure aluminium Dobsonian telescope with a fabulous Zambuto mirror for inquiring minds. Earlier he would have been looking through his virtual moon atlas deciding what he might want to focus on, and what phase the moon is in decides that. Once it is dark, and he has checked that the atmospheric conditions are good, “whaaaat is that you ask?” well, steady non turbulent air, and what the heck does that mean. Just like ocean currents, air currents can be clear, or not really murky, but not steady. Mike’s good friend and fellow OAF (Ottawa Astronomy Friends) Attilla and Alan Rahill started Clear Sky Charts.
This particular one is for the ranch in Baja but there are over 6000 worldwide! They are astronomer forecasts for “seeing” conditions. It predicts cloud cover, obviously a big deal;) no clouds good, cloudy…very very bad:) as well as transparency, as Attilla wrote: ‘transparency’ means just what astronomers mean by the word: the total transparency of the atmosphere from ground to space. It’s calculated from the total amount of water vapor in the air. It is somewhat independent of the cloud cover forecast in that there can be isolated clouds in a transparent air mass, and poor transparency can occur when there is very little cloud.
Then there is: Seeing, it forecasts astronomical seeing. (It’s an experimental forecast.) Excellent seeing means at high magnification you will see fine detail on planets. In bad seeing, planets might look like they are under a layer of rippling water and show little detail at any magnification, but the view of galaxies is probably undiminished. Bad seeing is caused by turbulence combined with temperature differences in the atmosphere. This forecast attempts to predict turbulence and temperature differences that affect seeing for all altitudes.
Bad seeing can occur during perfectly clear weather. Often good seeing occurs during poor transparency. It’s because seeing is not very related to the water vapor content of the air.
Then there is: Darkness, not the Darth Vader kind my geek friends but it shows when the sky will be dark, assuming no light pollution and a clear sky. Black is a dark sky. Deep blue shows interference from moonlight. Light blue is the full moon. Turquoise is twilight. Yellow is dusk and white is daylight. For those who prefer numbers, the scale is also calibrated. The numbers are the visual limiting magnitude at the zenith. (The brightness of the faintest star a standard observer can see straight up.
Then there is Wind-This forecasts wind speed at about tree-top level. The wind forecast won’t determine whether or not you can observe, but it may affect your comfort and the type observing you might be limited to. In particular, long-focal length astrophotography, or observing with large dobsonians require light wind conditions. High wind may be particularly dangerous for larger truss-tube dobsonians which must be disassembled in the vertical position.
and humidity-This forecasts ground-level relative humidity.
Humidity variations can indicate the likelihood of optics and eyepieces dewing.
But dewing is not simply correlated to relative humidity. Dewing tends to happen when the sky is clear, the temperature is dropping and there isn’t much wind. Being on a hilltop or in a small valley can make the difference between no dew and dripping telescopes. Unfortunately, the humidity forecast does not have the spatial resolution to know about small hills, valleys, or observatory walls. All of which can reduce dewing.A sudden spike in the humidity forecast, an hour or so after the cloud forecast predicts a sudden transition from cloudy to clear, when there is no wind, means that ground fog will form. Also, when the cloud forecast is opaque and the humidity forecast is 95%, rain is likely: a good time to cover the telescopes.
and then-temperatures-This forecasts temperatures near the ground. While temperature variations won’t determine if you can observe, the forecast can be handy choosing clothing for cold observing conditions. (In general, dress as if it were 20 degrees F or 10 degrees C colder than the forecast.) Observers with thick primary mirrors should take note of falling temperature conditions because their mirrors may require additional cooling to reach equilibrium and so prevent tube currents.
Cold temperatures also mean reduced battery capacity, stiffer lubricants, stiffer electrical cables and slower LCD displays. Camera sensors will have reduced noise. But, in general, electronics have a lowest temperature at which they will work.
Thank you Attilla for all this amazing information, all this before Mike even gets his camera out…I think I have it easy, I just put my camera under my shirt if it starts to rain:) As I’ve said, Mike’s work is an amazing undertaking. Everything has to be just right to capture the types of images he did above. I can tell when it is going to be a good night, lots of smiles and he is burning the candle well after I have slipped into bed, in the morning he is still processing his thousands of images, taken with a Asi 174mm ZW Optical astronomy video camera, picking out the clearest shots and stacking them with programs on his computer, I just have to open photoshop to crop something:) or get my cell phone out when he is setting up, usually before it is completely dark and start snapping, or clicking, well, my phone doesn’t even make a noise..Ha! This is fun:)
So, if you see this weirdness going on, don’t hesitate to walk on over and ask as many questions as you’d like and take a look for yourself through this amazing telescope, I’m really thinking it should have a name, the truck is Hagrid, the trailer Myrtle…I’ll put my imaginative name thinking cap on.
FYI, Mike is not an astrologer, nor can he read tea leaves or coffee grounds;)
Saludos amigos. May your skies be dark clear and steady