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      Volume 9 Issue 4 NcAstronomers.org April 2017      

Wednesday, April 5th 7:00 pm.
Madelyn Helling Library
Community Room

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Total Solar Eclipses

The scheduled speaker this month, Alan Stahler, had to cancel due to a family emergency. In his place, we will have two videos by Alex Filippenko describing solar eclipses. As excitement builds for this summer’s total eclipse in the US, we felt it timely to revisit this topic. The first video is a general introduction to solar eclipses; the second is interesting tales of past eclipses including the most famous eclipse of all. Why was it famous? Find out at the April meeting!

Dave Buchla will be on hand at the end to answer questions about eclipses or photographing eclipses. He has viewed 14 total eclipses and 2 annular eclipses and has several photos published in Astronomy magazine. Come and join the discussion- bring a friend. See Dave’s article below on photography.


President’s Rant

Hello NCA,

STEAM 2017 was a success! I was told by one of the staff that attendance was up over 2016, and we certainly felt the difference at the NCA booth. Our participation was made possible by the hard work of our members: Paul Bacon, Robin Hart, Greg Ouligian, Neal Stallions, Dan St John, Fran Thomas, Bill Thomas, Dave White, and Pam Griffin. Of course, Dave Buchla had already provided most of the displays, reserved tables and chairs, and basically gotten it all arranged. All we had to do was set everything up, staff the booth, and then pack it all away for the next event. Many thanks to all of you. It was a team effort and the effort was apparent. Now, I want to put in a plug for Astronomy Day on April 29th. We will need more people because that show will be all on us. So if you can help, please say so. Dave will feel better if he knows that he has enough help.

Finally, I would draw your attention to the editorial in the May issue of Sky and Telescope. Editor in Chief Peter Tyson reminds us what the scientific method is, and ends with an appropriate quotation from Henry David Thoreau. I hope that you will find the editorial timely and useful.

In the words of Neil deGrasse Tyson:

"Keep looking up."

John


Outreach - David Buchla

We had a very good turnout for our Scotten School Science Night. We had a number of Star wheels put together and exhibits that caught a lot of interest. John Griffin brought his binoculars on the pivot arm, which was a very popular and welcome addition. Dan St, John, myself and Greg Ouligian were also inside helping with star wheels and other exhibits, while Bill Thomas, Paul Bacon, and Byron Ross brought scopes to show a rather “fuzzy” moon through some thin clouds. Unfortunately, viewing was borderline between bad and awful.

Scotten School Since Night          

Scotten School Science Night

Our next event is March 25th with the STEAM Expo at the fairgrounds. Again, we will be making Star Wheels and having exhibits set up. We can definitely use volunteers – for this event, John Griffin is coordinating as I will be out of town that day. Let John know if you can help out.

In April, our big event is only weeks away. We have done a lot of prep work for Astronomy Day, which is April 29th starting at 11 am and going till 3. We plan to have the exhibits in the lobby open when the library opens (at 11 am) and some inside activities begin then such as the book review with Toni Graybill leading a discussion on “The Martian”. If possible, as much of the outside parts should be ready at this time as well. The community room will not open until noon, at which time the planetarium shows will begin. I plan to be at the library at 8:30 to start setup. Needless to say, there is much to do.

Preparation for AD has been going well. John has been punching “clean” holes in our pinhole postcards that show the eclipse path and how to project the partial eclipse. Outreach paid for 1000 of these cards, which we are handing out at various outreach events including AD. (Your dues money at work!). Yolande Wilburn, Branch Librarian, continues to be a big help and will be supporting our efforts with various activities including a book review, art contest for kids, “outer space” food sampling, as well as a display. She is also helping by printing star wheels and Astronomy Day flyers. I hope to have some of the flyers at the next meeting that will include this year a schedule including four 15 minute talks. Our talks are going to be in the new outdoor pavilion and begin at 1 pm with Lonnie Robinson doing a comet making demonstration. Follow-on talks will be given by yours truly on the Great American Eclipse and Alan Stahler on Beginning Astronomy. A surprise guest will be talking about the scale of the solar system.

We have had a lot of help in the past and it is really appreciated, but this year we have even more planned, so we definitely can use you. We could use help with star wheels (in the kids library section), and help at the science demo table. I have heard from a few people that we will be covered as far as outside scopes are concerned. John is coordinating the outside displays and Rick will coordinat setting up the lobby area. Also, if anyone can loan us a folding table, we may be able to use it, We used every one of the library’s tables last year and we are borderline with enough. Finally, take down and put away begins at 3 pm. To contact me for questions or information, click here:

Finally, a few summer outreach programs have been updated. (See calendar). We have Starry, Starry Nights at Empire Mine on July 15 for the Hospital Auxillary benefit. Note the Plumas-Eureka dates are one day earlier (July 26, 27, and 28) to avoid the brighter moon on the 29th. We plan only one day at the fair this year - it will be Saturday August 12. 


Solar Eclipse Photography

David Buchla

With the upcoming solar eclipse August 21st on US the US mainland for the first time since February 26, 1979, I was asked to share some of my thoughts particularly with regard to photographing the eclipse. So right off the bat, if this is your first eclipse, I would definitely suggest a minimum of photography and a maximum of soaking in this amazing sight. Don’t watch the entire eclipse through a viewfinder! I took a couple of photos on my first one only during the middle of the eclipse and I am glad I didn’t spend the entire time photographing it.

Eclipse sequence

Even before totality, there are interesting natural phenomena to watch for. Here is a short list of things to look for:

  1. Make pinhole images and look at shadows. You might want to make a pinhole image (see Figure 1). As totality nears, shadows will be sharper, especially in one direction as opposed to the other (due to the crescent nature of the source). As the partial phase gets further along, you may see things like the hairs on your arm cast a shadow.
  2. Notice the color of light in the sky and the temperature dropping.  A 10o drop is not uncommon.  In the arctic eclipse in March of 2015, the temperature dropped from -10 oF to -20 oF at totality. Brrrr!
  3. About 15 minutes before totality look west and observe the darker western horizon as the shadow approaches (like an oncoming thunderstorm).
  4. A minute or so before totality, you may see shadow bands on a light-colored surface. They are elusive; I’ve only seen them twice in 14 total eclipses but stuff happens fast and I tend to forget to look. If you see them, yell out “shadow bands” so others can see them.
  5. Just before totality, watch for the diamond ring! It is one of the most spectacular events during the eclipse. The diamond ring is fleeting – it only lasts for a couple of seconds but is a true WOW factor. There is a second one marking the end of the eclipse.
  6. Right as totality begins, look for the reddish color on the edge of the sun to see the chromosphere. There will probably be a prominence or two. In the 2001 eclipse in Zimbabwe, we saw a detached prominence – something we will never forget. The prominences will seem to change as the eclipse progresses because of the moon’s covering some while revealing others.
  7. Observe extent of the corona. A small binocular is ideal to see the structure and gossamer appearance. Some people like to have an eye patch covering one eye before totality, and then remove it during totality to have a dark-adapted eye to view the extent of the corona. I have never done this, but you might want to consider it.
  8. Look around briefly to see the sky color during totality and if any planets or bright stars are visible. It’s hard to tear your eyes away from the main event, but worth taking in the whole sky at least once.

         

Figure 1

Photography

Photography is a wonderful tool to build a memory of the event, but is no replacement for the real thing. Having said that (again), here are some suggestions from my experience. Others may have different ideas, so be open to those ideas too.

One important photograph you can take is to record the general scene during totality with any camera – it can be as simple as a point and shoot and gives you a personal memory. Take a few shots of your surroundings with the eclipsed sun in the background. NO FLASH! Use black tape over any possible flash to avoid huge annoyance to avoid having a lot of “former friends”.  Having said that, a scene like the one in Figure 2 makes a nice memory. I shot this on shipboard during totality in 2010. Just a quick “click” and back to visual.

Figure 2

If you want to get more serious about photography, I will pass on tips I have used, keeping in mind that there are many eclipse photographers that have done better work than I!

Here are some of my hints:

1.   Use only manual focus and settings. You are likely to be frustrated if you let the camera try to focus as it may not be able to do so!

2.   Shoot in RAW for later processing and shoot a variety of settings. I like to start with the exposure for the diamond ring (fairly short) and then take longer time exposures.

3.   Tripod – avoid extending more than necessary – especially the center column. Add weight to stabilize the tripod.

4.   Use a cable release or programmed settings (see Eclipse Orchestrator website).

5.   Maximum recommended exposure in seconds = 340/focal length in mm. For longer than this, it is best to use a clock drive. For my 440 mm focal length, 1 s exposure is about the maximum without a drive.

6.   Use Live View and Silent mode if available to minimize shutter slap.

7.   A tracking mount is useful (but not required) to avoid field rotation if you plan to do HDR (stacking). There are people that do amazing work with stacks of 20 or more. I only use 3 or 4 in a stack, but I might try to go for more in this one. Figure 3 shows a stack of three taken in the

Russian eclipse in 2008. I did not have tracking and this was taken with my 100-400 zoom lens with a 1.4 X multiplier (like a Barlow).

Figure 3

Incidentally, if you have the luxury of choosing focal length and zoom or not zoom, I prefer a fixed focal length of about 400 -500 mm on my full frame camera (higher will restrict field of view, but it depends to some extent on your camera). My zoom lens, which is the one used in Figure 3, gave me trouble by changing a tiny bit between exposures and made stacking much more difficult as the image size changed a little between photos. The reason I have carted the zoom lens along on eclipse trips is that it is lighter than my big fixed lens, and you know what airlines charge for excess weight!

            During totality, there is no time to change ISO, or other settings except for exposure time, so you need to choose settings beforehand. Assuming you are on a tripod, I like to set up for the diamond ring at the start of totality. Figure 4 shows a diamond ring I shot in Tahiti in 2010. This was taken at 1/600 s with an equivalent 420 mm telephoto at ISO 500 using a Canon 5D (on shipboard).  An ISO of 400-500 is my preferred value because it is fast enough to pick up outer corona and does not contribute to noticeable noise. Notice the prominences and the chromosphere in this shot. After shooting the short exposures, start lengthening the time exposure to get the outer corona. See the table for details.

Figure 4

Table 1 will give you an idea of different exposures to use, depending on the f-ratio of your lens. The equation I used to develop the table is from Fred Espanek and is t = f2/(I X 2Q),

where t = shutter speed in seconds, f = f ratio, I = ISO, and Q is a brightness exponent. For a typical ISO setting of 400, exposure times are calculated on the spreadsheet:

Finally, here are a few examples I like of eclipse photography. I hope this gives you some ideas to help with your own eclipse memories. Happy shooting!

Figure 5


Secretary/Treasurer - Dan St. John

Our members database has been updated with those who have donated in the current year.  In June our meeting is a potluck, but for 'Members Only'!  In addition to the food and fellowship we will have a presentation on 'NASA SOFIA SETI, Airborne Astronomy Ambassadors' by Jeff Baldwin and Larry Grimes.

If you have not yet updated your membership for 2017, NOW is the time to donate and assist us with our mission:

'Bringing Astronomy to the Public'

Your membership dues help make these efforts a great success. Don't miss Astronomy Day at the Library, April 29th.  Dave has a great program planned and we need your help.  

At our meeting on April 5th, I will again be collecting 2017 Dues/Donations ($20). So when you come to reflect on the Amazing CASSINI Discoveries of the last decade, please bring your check (or CASH) and help us cover our expenses for Room Rent, Speaker Honorarium, Outreach Supplies and Miscellaneous Administrative Costs.

BIG Thank You

to all our members who join and make our programs possible!

If you can't make our meeting, send your check to:                                           NC Astronomers, %Dan StJohn,                    
12296 Valley View Rd, Nevada City, CA 95959


 


This article is provided by NASA Space Place.
Visit spaceplace.nasa.gov to explore space and Earth science!

What It’s Like on a TRAPPIST-1 Planet
by Marcus Woo

With seven Earth-sized planets that could harbor liquid water on their rocky, solid surfaces, the TRAPPIST-1 planetary system might feel familiar. Yet the system, recently studied by NASA’s Spitzer Space Telescope, is unmistakably alien: compact enough to fit inside Mercury's orbit, and surrounds an ultra-cool dwarf star—not much bigger than Jupiter and much cooler than the sun.

If you stood on one of these worlds, the sky overhead would look quite different from our own. Depending on which planet you're on, the star would appear several times bigger than the sun. You would feel its warmth, but because it shines stronger in the infrared, it would appear disproportionately dim.

"It would be a sort of an orangish-salmon color—basically close to the color of a low-wattage light bulb," says Robert Hurt, a visualization scientist for Caltech/IPAC, a NASA partner. Due to the lack of blue light from the star, the sky would be bathed in a pastel, orange hue.

But that's only if you're on the light side of the planet. Because the worlds are so close to their star, they're tidally locked so that the same side faces the star at all times, like how the Man on the Moon always watches Earth. If you're on the planet's dark side, you'd be enveloped in perpetual darkness—maybe a good thing if you're an avid stargazer.

If you're on some of the farther planets, though, the dark side might be too cold to survive. But on some of the inner planets, the dark side may be the only comfortable place, as the light side might be inhospitably hot.

On any of the middle planets, the light side would offer a dramatic view of the inner planets as crescents, appearing even bigger than the moon on closest approach. The planets only take a few days to orbit TRAPPIST-1, so from most planets, you can enjoy eclipses multiple times a week (they'd be more like transits, though, since they wouldn't cover the whole star).

Looking away from the star on the dark side, you would see the outer-most planets in their full illuminated glory. They would be so close—only a few times the Earth-moon distance—that you could see continents, clouds, and other surface features.

The constellations in the background would appear as if someone had bumped into them, jostling the stars—a perspective skewed by the 40-light-years between TRAPPIST-1 and Earth. Orion's belt is no longer aligned. One of his shoulders is lowered.

And, with the help of binoculars, you might even spot the sun as an inconspicuous yellow star: far, faint, but familiar.  

Want to teach kids about exoplanets? Go to the NASA Space Place and see our video called, “Searching for other planets like ours”: https://spaceplace.nasa.gov/exoplanet-snap/

This artist's concept allows us to imagine what it would be like to stand on the surface of the exoplanet TRAPPIST-1f, located in the TRAPPIST-1 system in the constellation Aquarius.  Credit: NASA/JPL-Caltech/T. Pyle (IPAC)



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