Well this week has been spent with more preparation work for the upcoming solar eclipse and what equipment we plan to take on our flight to Casper, WY. Scanning the latest batch of email threads from the OC Astronomers Yahoo Group has provided some good suggestions and recommendations from some of the veteran eclipse viewers and astroimagers. One thing that I had not really considered, but now on retrospection, seems like it could be very important, and that is
the need to plan for your camera being out in direct exposure to the sun for many hours before and after the eclipse.
Yes, that could be very important. You wouldn't want all your preparation to come to naught with your camera, after several hours in the sun waiting for totality, to finally getting overheated due to direct exposure of the sun and have it stop working just in time to miss the main event! OCA Dave Kodama and others recommended just installing a little plastic or similar radiation shield so that direct sunlight does not fall on the camera. Yes, that is exactly what I will now plan to install on my camera and telephoto lens.
Astronomer Assistant Willow was looking over my shoulder when I read all about this radiation shield business and she spoke right up and recommended what I could use to make the shield.
|Astronomer Assistant Willow suggests the cardboard separator, from her Fancy Feast 24-can pack, for solar radiation shade|
She said the little 7 x 10 inch cardboard separator that come in her Fancy Feast 24-can packages of grilled salmon would be an ideal starting point. Normally, I would have relied on my previous systems engineering training and looked at shield requirements and such, but, this time I just jumped in and accepted her recommendation. You can get your own separator at Pet Smart, one per 24-can package. The finished solar radiation shield is shown below.
|Solar radiation shield should keep camera temperature at ambient air temperature|
There is no interference with any of the focal length or focus adjustments and a little notch cut in the top of the radiation shield is there so that the sun can still be seen using the Sol-Searcher. In the photo below you can see the Sol-Searcher, now mounted directly to the camera hot shoe and no more masking tape as used last week is needed. Remember the Sol-Searcher, as described in a previous post, has pin how through which the solar disk is projected onto a translucent screen on which the image can be easily seen without having to look directly at the sun with your own eyeballs.
|Mount Sol-Searcher on camera hot shoe (no masking tape required)|
Here is the hot shoe accessory used to mount the Sol-Searcher to the camera. The camera hot shoe is normally used to mount photographic accessories like external flash lamps, but for me it works just great for the Sol-Searcher. The bottom knurled nut is used to securely keep this accessory securely fastened to the camera hot shoe and the Sol-Searcher is conveniently installed on top of the bottom nut held in place with the top knurled nut. The bolt is standard 1/4 inch - 20 thread. The bottom base is n reality very small, about 3/4 inch square and its exactly into the camera hot shoe.
|Hot shoe adapter allows mounting of astronomical accessories on camera (no masking tape required)|
Another concern raised in the OCA Yahoo Group email thread was the availability of normal creature comforts during the eclipse. The prime areas along the total eclipse path are expected to be flooded with observers and some locations are predicted to be overwhelmed with possible long lines at restaurants, grocery stores, gas stations and even potential saturation of cell phone coverage. We don't know how likely or how deep these shortages might be in actuality but we should take some preparations. We will be taking our hand held ham radios just for fun and just in case.
Since we are flying to Casper and won't have many of items we normally take with us to star parties and such, we decided to bring at least one chair with us on the flight. We found this lounge chair that we can fold up and put in our luggage so that we have at least one place to rest during the eclipse period, which begins several hours before totality and goes several hours after also. Our current patio lounge chairs are just a bit big and heavy. We assume that we can at least find enough space on the ground to set up this chair next to our tripod and cooler full of lunch and drinks.
|Portable chase lounge fits in airline luggage|
Speaking of drinks, I've made a fantastic discovery for making sugary sweet drinks with sugar free sweetener, which cuts out a lot of calories. We usually have coffee in the morning but our coffee is really just an excuse to fill up the cup with sweet flavored syrups with a dab of cream. After coffee, my favorite lemon drop martini recipe called for two shots of simple syrup, which is mostly sugar with a little water, having 80 calories per shot. With this new sugar free sweetener from Torani, each martini can be just as sweet, but with 160 fewer calories. The vegetables and dip are just a slight consolation to the good health recommendations. This low calorie treat is great for pre eclipse planning or post eclipse celebration in case of success or consolation in case of clouds or tripod tipping over.
|While you are waiting for totality enjoy Torani sugar free simple syrup substitute in your lemon drop martini|
Finally, now with the thought of our brains a little bit under the influence, we should get to a little astrophysics as we get ready for the eclipse. I have been trying to understand for some time now how clouds of gas in star forming regions are able to get rid of sufficient energy that gravitation can overcome the remaining thermal motion and collapse to form stars. We know that as atoms cool down and radiate photons as they approach the ground energy state, but the final atomic transition is in energy equivalent range of 1000's Kelvin, which is much higher than the measured temperature of gas clouds that eventually collapse, which is down in the 10-20 K range. So what other physical processes are available to enable the gas to cool down even further.
Bremsstrahlung processes can be responsible for further cooling. Anytime a charge is accelerated, it will radiate and this process is observed in the collision of atoms, where the electrons and protons experience differential acceleration, which gives rise to a net acceleration and radiation.
This is all fine and good but the question remaining for me is what is the frequency of the photon given off when a charge is accelerated? We know that all black bodies radiate energy and photons according to the body's temperature. The Earth is around 300 K and its radiation peaks in the infrared and clouds of gas in space at 10-20 K radiate in the far infrared. We can see this by looking at Wien's Law which says that the wavelength at which the radiation peaks is inversely proportional to its temperature. So radiation from clouds of gas would peak at wavelengths about 15 times longer than objects at 300 K on the Earth.
Ok, so given that Bremsstrahlung processes could be responsible, the question remains, how many photons and of what energy are they given off during this process? We know from classical electrodynamics the amount of energy that is given off for a certain trajectory around a charged particle, as shown below, but classical physics doesn't deal with photons. Is it just one photon of the right energy or is it multiple numbers of photons of energy such that the sum equals the exact amount and do the photons emerge at the start of the acceleration or at the end or sort of continuously all the way through the acceleration trajectory. The 2nd graph in the image below taken from the referenced paper shows the answer: The energy spectrum is flat, meaning that almost a continuous range of photons are emitted just in the right amount so the total energy emitted equals the right amount. That is pretty neat stuff even though I can't quite get the calculation that produced that flat spectrum and I can't quite reconcile it with my notion of all of these photons being emitted in just the right way with the right frequency and energy so that the sum works out just right. The mystery for me goes on even though there is probably a paper and explanation out there just waiting to be read.
|How many photons are associated with Bremsstrahlung radiation (Source: www.astro.utu.fi/~cflynn/astroll/l3)|
Ok, that about wears me out. Maybe it's time for another martini after all of the quantum mechanics stuff. But there is also still the astrophysics mystery of whether the density of gas molecules in the collapsing clouds is such that atoms can randomly collide often enough to emit all of these Bremsstrahlung photons to cool off the gas fast enough to match the predicted time taken for a gas cloud to collapse and form a star. Also I would have guessed that the gas cloud would have been composed of neutral gas atoms at that time and not the ionized particles necessary for the first form of Bremsstrahlung radiation. I don't know. Maybe the free internet edX course, Astrophysics: The Violent Universe, mentioned in the last post, will be providing the answers and how to calculate it. The mystery (for me, not for the real experts) continues.
Until next time
Resident Astronomer George
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Great idea for mounting the Sol-Searcher. My Sol-Searcher will not accommodate a 1/4" screw. Did you have to enlarge the mounting hole of the Sol-Searcher? Do you recommend using the front or the rear screw hole of the Sol-Searcher? Thanks.ReplyDelete
Yes, I just enlarged the mounting hole and didn't think of which hole to use. On retrospection, the use of the back hole would have resulted in not having the Sol-Searcher hang over the back of the camera and would have instead been more flush with it. You still have to worry about the initial alignment with the optical axis.Delete
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