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Sunday, September 25, 2016

Cool Nights and Clear Skies

Some of the clearest nights of the year arrive in late summer and early fall. In much of North America, September and October bring clearer weather than any other month. If that's not enough incentive for you to get out and do lots of stargazing, consider what comes next.

Last evening was one of those crisp nights with sparkling skies that urge me to take out the telescope and/or binoculars and do some observing. November tends to have increased cloud cover, which largely persists until mid to late spring. October is known to be the clearest of the 12 months throughout a wide span from New England through the South and lower Midwest to Texas and the Great Plains.

Image of The Pegasus-Andromeda area spans a huge area of sky Screenshot from Stellarium
The Pegasus-Andromeda area spans a huge area of sky
Screenshot from Stellarium
Much of the country is more that 70 percent cloudy in various months. In September and October, only bits of Maine and the Northwest are so obscured. However, from November through April as much as a quarter to one-third of the country is on the unfavorable side of the 70 percent "isoneph" (line connecting points of equal cloudiness).

A mere absence of clouds is one thing, a beautifully clear and transparent sky is another. In much of North America strong cold fronts in September and October often clean the air to superb transparency. At such times we get deep blue skies by day and some of the best observing nights of the year.

What stellar sights can we behold on these nights? In the early evening, there are fewer bright stars than usual. Arcturus is setting in the west-northwest, and the Big Dipper is getting low in the southwest. The only high and bright stars are those of the Summer Triangle: Vega, Deneb, and Altair.

Capella is peaking up in the northeast. Above it, the forked branch of Perseus is ascending. Much higher is the "W" of Cassiopeia, the queen.

Face east and look high and you will see the 2nd magnitude stars of Andromeda and Pegasus forming a very long, nearly horizontal line. It starts with Gamma Andromedae on the left, fastens to the Great Square of Pegasus, and ends with Epsilon Pegasi way over in the south.
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Saturday, September 24, 2016

Supernova Hunters

Supernovae are stars that explode with the energy of a few thousand atom bombs. Since the morning of February 11, 1989, when Insight Observatory science writer, Dale Alan Bryant and I independently discovered supernova 1989b, I acquired a passion for extragalactic supernova search. Not long after that inspiring morning, I purchased the Supernova Search Charts and Handbook by Gregg D. Thompson and James T. Bryan Jr. to compliment my telescope for this endeavor. This unique atlas contains 236 charts of more than 300 of the brightest galaxies, each specifically prepared to facilitate the discovery of supernovae. The comparison of these charts with the field seen in a telescope enables any extragalactic supernova to be spotted immediately. The charts include 345 galaxies printed on translucent paper for use on a lightbox, each one carrying an explanation of the constellation in which the galaxy lies, special characteristics of the galaxy, observing instructions, expected maximum brightness for the supernovae in each galaxy, and the reference for the sequence.

Image of Pan-Starrs1 Wide-Field Imaging Facility
Pan-Starrs1 Wide-Field Imaging Facility
Of course this tool was ideal in the days before CCD imaging technology was readily available to amateur astronomers. I would observe a handful of the brighter galaxies using this atlas with my 6" Newtonian reflecting telescope and a few years later with my 10" telescope. Although after years of searching and never spotting a supernova again, the nights of observing these galaxies were priceless as I was able to observe their unique characteristics that would make it easier to find one.

It would take many clear nights and hours to pursue such a project back then. However, with the current technology of the Internet and CCD imaging, there is a way to search for extragalactic supernovae from the comfort of your own home and a personal computer. A program created through Zooniverse.org called Supernova Hunters allows you to do so at your leisure. To be a supernova sleuth, you simply sign up on their website to become an observer. The website walks you through the process of analyzing the data of galaxies that could have potential suspects. I recently signed up for an account and started analyzing galaxy data immediately.

With Supernova Hunters you can aim to discover lots of new explosions and pass them on to the wider astronomical community. But finding supernovae isn't easy. You can expect to observe about one supernova per galaxy every few centuries. So to find lots of supernovae, Supernova Hunters need to look at many galaxies at once. Pan-STARRS1 is great for this. Due to the large camera, the telescope has a field-of-view that covers the same area as the full moon. This allows the telescope to scan large areas of the sky each night imaging many galaxies. Supernovae are also extremely bright and can outshine all the other billions of stars that make up their galaxy. This means that observers can discover distant supernovae even if we don't see the galaxy hosting the supernova.

Where does the image data of the galaxies come from? - On the island of Maui in Hawaii, the Pan-STARRS1 telescope is scanning large areas of the sky each night trying to do just that. Using a process called difference imaging they look for anything that has changed by comparing each night's data with high-quality reference images of the same area taken a few years ago. Pan-STARRS, the Panoramic Survey Telescope and Rapid Response System, an innovative design for a wide-field imaging facility were developed at the University of Hawaii's Institute for Astronomy. The combination of relatively small mirrors with very large digital cameras results in an economical observing system that can observe the entire available sky several times each month. How do stars evolve? How fast is the universe expanding? How far away are the galaxies we observe? These are some of the questions that are hoped to be answered by studying supernovae. Supernovae are explosions lasting a few weeks to several months which we hope to discover new sources of light that have appeared since the reference image was taken. But their current software makes much bogus detection of supernovae. These are image artifacts due to the electronics in the camera or image processing that have gone wrong.

Currently, computers aren't very good at telling the difference between the real and bogus detections. You can help improve our understanding of supernovae and improve our detection algorithms by classifying detections as real or bogus. The National Aeronautics and Space Administration currently support the operation of the Pan-STARRS1 telescope with a grant issued through the Near Earth Object (NEO) Observation Program.
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Monday, September 5, 2016

Cosmic-Watch

When I developed an interest in the stars and astronomy at a young age I recall being fascinated with maps and globes that represented the night sky and solar system objects like the moon. Of particular interest were those clear acrylic globes that had the stars on the outer clear globe (representing the celestial sphere) and a representation of the earth as a smaller globe in the center, with other solar system objects hanging from apertures inside the globe. 

Now there is a new app for iOS and Android that successfully creates this Earth-centered view called "Cosmic-Watch" by Celestial Dynamics Ltd. At its core this app is a watch which has a number of different views and perspectives of our universe with our Earth at the center. These items include:

The clock showing the current time at any location you choose along with the positions of the sun, moon, and planets

A "celestial sphere" view that shows the location of the stars and planets on a transparent globe encompassing the Earth






A long distance view of our solar system showing the relationship of the planets and various overlays which show how the position of the sun relates to the current month/season/etc.





Other features of note: 
  • For those "astrologically" inclined there is a view showing where the planets are in relation to the constellations in the Zodiac
  • A time adjustment feature which allows users to speed forward or backward in time, useful to see where the sun, moon or planets may be at some time other than the present

The functionality of the app is straight forward, I had no problem figuring out how to navigate the various options. Point and dragging changed the view as expected. On the Android phone, I tested on (a Sony Xperia Z3 Compact) the graphics were nice and sharp and beautiful to look at. A small complaint would be on such a small phone the graphics can appear to get a bit cluttered for certain views (like the celestial sphere where there was a bit too much going on)...this is a minor quibble and most likely won't be an issue on larger phones or tablets (anyways this app is screaming out for a larger screen so you can enjoy view!). I enjoyed exploring with Cosmic-Watch and I can see this being a very useful app in educational settings where explaining why we see what we do in the sky is immensely easier with visuals like what the Cosmic-Watch provides.

How to get Cosmic-Watch:

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