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      Volume 9 Issue 5 NcAstronomers.org May 2017      

Wednesday, May 3rd 7:00 pm.
Madelyn Helling Library
Community Room

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Jupiter & Saturn
Observation and Exploration  
  by Mark Graybill

Jupiter and Saturn will both be excellent observational targets from May through summer of this year. Find out what to see and what it takes to see it for the two showpiece planets of our solar system, including observation of their moons. Also, the exploration of these planets with space probes will be discussed, including the Cassini probe which will end its 14 year mission with a descent into Saturn's atmosphere in September, and the forthcoming Europa Clipper, which will explore the subsurface ocean of Jupiter's moon Europa in the 2020s.

Bring a friend ... bring the kids!


President’s Rant

Hello NC Astronomers,

We had a very successful Astronomy Day on Saturday, April 29th. It was made possible by the efforts of everyone who helped. Master magician Dave Buchla just keeps pulling rabbits out of his hat. If we didn’t have his organizational and exhibit-building skills, most of our outreach events would be pretty thin. Huge thanks to all of you for helping to bring Astronomy Day together. I’ll have a little more to say on Wednesday at the meeting.

Speaking of the meeting, come hear Mark Graybill speak about observing and exploring Jupiter and Saturn. I’m looking forward to his presentation.

That’s it from me. See you at the meeting.

Get out and look up.

John


Outreach - David Buchla

With a total club effort, we had quite an event filled Astronomy Day. There were so many helpers to put it together, help out and clean up that I would be hard pressed to name all involved and I am afraid to try. So, to all of you that helped out, my sincere thanks for a job well done. Outside, we featured several solar scopes, and were fortunate to have a beautiful spring day with clear skies. I understand some prominences were seen in the H-alpha scope and a couple of small sunspots were in the white light scopes. Inside, we had a number of changes this year, including talks in the classroom, comet making (Lonnie made an awesome comet!), space food tasting, and an art contest with some very well done pictures of Saturn by lots of different kids. The librarians helped out with kids making lots of star wheels to take home as a souvenir. There were also a few new exhibits. with one on eclipse safety to educate the public on this summer's long anticipated eclipse. (As an aside, I was on the Black Sea for the last eclipse in this saros, which is 145.) We also gave out our "pinhole" postcard with the eclipse path on it to our guests. Our featured inside exhibit for the day was the Star-lab planetarium, which *surprise* was larger than previous years and we had to make last minute adjustments to the room to make it fit. With a cast of several hard-working volunteers and some shuffling and head-scratching, we made it work! Together, Mark Graybill and I gave 5 planetarium shows. All and all, we had a successful event.

Our next scheduled outreach event is Starry, Starry Nights at Empire Mine on July 15, which is a benefit for the Hospital Auxillary. Later this summer, we have Plumas-Eureka star party for the state park. Note the dates are one day earlier (July 26, 27, and 28) to avoid the brighter moon on the 29th. We plan to share this event with some members from SVAS. Finally, we will have only one day at the fair this year with solar viewing to avoid too much of the hot August sun. It will be August 12; details later.

Finally we've added a member's star party for the last quater moon on June 17th. This avoids conflicts with other scheduled star parties - see calandar for location. If you have outreach questions or comments, you can reach me here:  


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 and your dues help make our efforts a great success.

 At our meeting on May 3rd, Rick Bernard (in my absence) will be collecting 2017 Dues/Donations ($20). So when you come to absorb Mark Graybill's revelations about the Gas Giants in the Solar System, please bring your check, cash or a new member and help us inspire Nevada County's 'budding' scientists.

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!

NOAA's Joint Polar Satellite System (JPSS) to monitor Earth as never before
By Ethan Siegel

Later this year, an ambitious new Earth-monitoring satellite will launch into a polar orbit around our planet. The new satellite—called JPSS-1—is a collaboration between NASA and NOAA. It is part of a mission called the Joint Polar Satellite System, or JPSS.

At a destination altitude of only 824 km, it will complete an orbit around Earth in just 101 minutes, collecting extraordinarily high-resolution imagery of our surface, oceans and atmosphere. It will obtain full-planet coverage every 12 hours using five separate, independent instruments. This approach enables near-continuous monitoring of a huge variety of weather and climate phenomena.

JPSS-1 will improve the prediction of severe weather events and will help advance early warning systems. It will also be indispensable for long-term climate monitoring, as it will track global rainfall, drought conditions and ocean properties. 

The five independent instruments on board are the main assets of this mission:

  • The Cross-track Infrared Sounder (CrIS) will detail the atmosphere’s 3D structure, measuring water vapor and temperature in over 1,000 infrared spectral channels. It will enable accurate weather forecasting up to seven days in advance of any major weather events.
  • The Advanced Technology Microwave Sounder (ATMS) adds 22 microwave channels to CrIS’s measurements, improving temperature and moisture readings.
  • Taking visible and infrared images of Earth’s surface at 750 meter resolution, the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument will enable monitoring of weather patterns, fires, sea temperatures, light pollution, and ocean color observations at unprecedented resolutions.
  • The Ozone Mapping and Profiler Suite (OMPS) will measure how ozone concentration varies with altitude and in time over every location on Earth's surface. This can help us understand how UV light penetrates the various layers of Earth’s atmosphere.
  • The Clouds and the Earth’s Radiant System (CERES) instrument will quantify the effect of clouds on Earth’s energy balance, measuring solar reflectance and Earth’s radiance. It will greatly reduce one of the largest sources of uncertainty in climate modeling.

The information from this satellite will be important for emergency responders, airline pilots, cargo ships, farmers and coastal residents, and many others. Long and short term weather monitoring will be greatly enhanced by JPSS-1 and the rest of the upcoming satellites in the JPSS system.

Want to teach kids about polar and geostationary orbits? Go to the NASA Space Place: https://spaceplace.nasa.gov/geo-orbits/

Caption: Ball and Raytheon technicians integrate the VIIRS Optical and Electrical Modules onto the JPSS-1 spacecraft in 2015. The spacecraft will be ready for launch later this year. Image Credit: Ball Aerospace & Technologies Corp.

 



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