Sunday, December 27, 2009

upcoming eclipses

Thanks to Nurit and Asher for the notice and info.

Get ready for not one, but 2 eclipses!

This Thursday night, Dec 31, we will have a very slight lunar eclipse. The view will be about the same from anywhere on this half of the globe.Only about 7% of the oon will enter the Earth's shadow. The casual observer may not notice anything, but it's more pronounced through binoculars or a telescope.

Lunar eclipse Thursday,Dec 31
starts -  20:53 IST
ends  -  21:52 IST

Look for the full moon high in the eastern sky. The shadow will be most pronounced at mid-eclipse, around 9:25pm on lower right side of the moon.

January 31st will thus be a momentous date!  Not only will it mark the end of 2009, but the lunar eclipse will also fall on a "blue  moon," which in popular usage (there are alternate definitions) is the second full moon in a calendar month (the first was Dec. 2).

Monday, December 21, 2009

Happy winter solstice

Today at 19:47 Israel time, the Sun will appear to stop (thus "Sol stat" from the Latin) on it yearly journey to the south and begin to turn around. This has the effect of making today the shortest day of the year, with the sun only up10 hours and 5 minutes.

Although this is the official 1st day of winter in the norther hemisphere (also known as midwinter day) the days will actually start to get longer starting tomorrow. However, don't put away your winter clothes yet. Due to the large thermal mass of water on the globe (75%) it will continue to get colder through Jan.

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Saturday, December 19, 2009

Choosing Your First Telescope


As a followup to my previous post Buying your 1st Telescope,  here is more from a recent article in  Sky & Telescope


Choosing Your First Telescope

Every year millions of people buy a telescope, but few know what to look for when making their purchase.

by J. Kelly Beatty

With a little guidance, you can pick a high-quality telescope that can last a lifetime. Click on the image to see seven important tips when buying a telescope.
S&T: Craig Michael Utter
Here's a quick guide to help you make sense of the hundreds of telescope models available today. Armed with these few basics, you'll have a good idea what to look for (and what to avoid) when scouring the marketplace for your new scope. If you still have questions or need more details, check out our extended help guide.Many (arguably most) good starter scopes cost $400 or more, but some superb choices are available for under $250. For some specific recommendations, read our review of Lost-Cost Starter Scopes. But read this article first, so you'll understand the terminology in that review.
The telescope you want has two essentials: high-quality optics and a steady, smoothly working mount. And all other things being equal, big scopes show more and are easier to use than small ones, as we'll see below. But don't overlook portability and convenience — the best scope for you is the one you'll actually use.
The most important characteristic of a telescope is its aperture — the diameter of its light-gathering lens or mirror, often called the objective. Look for the telescope's specifications near its focuser, at the front of the tube, or on the box. The aperture's diameter (D) will be expressed either in millimeters or, less commonly, in inches (1 inch equals 25.4 mm). As a rule of thumb, your telescope should have at least 2.8 inches (70 mm) aperture — and preferably more.

Dobsonian telescopes provide lots of aperture at relatively low cost.
S&T: Craig Michael Utter
A larger aperture lets you see fainter objects and finer detail than a smaller one can. But a good small scope can still show you plenty — especially if you live far from city lights. For example, you can spot dozens of galaxies beyond our own Milky Way through a scope with an aperture of 80 mm (3.1 inches) from a dark location. But you'd probably need a 6- or 8-inch telescope like the one shown at right to see those same galaxies from a typical suburban backyard. And regardless of how bright or dark your skies are, the view through a telescope with plenty of aperture is more spectacular than the view of the same object through a smaller scope.Avoid telescopes that are advertised by their magnification — especially implausibly high powers like 600×. For most purposes, a telescope's maximum useful magnification is 50 times its aperture in inches (or twice its aperture in millimeters) . So you'd need a 12-inch scope to get a decent image at 600× And even then, you'd need to wait for a night when the observing conditions are perfect.
Telescope Types
You'll encounter three basic telescope designs.Telescope types
Refractors have a lens at the front of the tube — it's the type you're probably most familiar with. While generally low maintenance, they quickly get expensive as the aperture increases.
Reflectors gather light using a mirror at the rear of the main tube. For a given aperture, these are generally the least expensive type, but you'll need to adjust the optical alignment periodically — especially if you bump it around a lot.
Compound (or catadioptric) telescopes, which use a combination of lenses and mirrors, offer compact tubes and relatively light weight; two popular designs are called Schmidt-Cassegrains and Maksutov-Cassegrains.
The objective's focal length (F or FL) is the key to determining the telescope's magnification ("power"). This is simply the objective's focal length divided by that of the eyepiece, which you'll find on its barrel. For example, if a telescope has a focal length of 500 mm and a 25-mm eyepiece, the magnification is 500/25, or 20x. Most telescopes come supplied with one or two eyepieces; you change the magnification by switching eyepieces with different focal lengths.
Telescope Mounts
 Telescope mounts
Your telescope will need something sturdy to support it. Many telescopes come conveniently packaged with tripods or mounts, though the tubes of smaller scopes often just have a mounting block that allows them to be attached to a standard photo tripod with a single screw. (Caution: A tripod that's good enough for taking your family snapshots may not be steady enough for astronomy.) Mounts designed specifically for telescopes usually forgo the single-screw attachment blocks in favor of larger, more robust rings or plates.
On some mounts the scope swings left and right, up and down, just as it would on a photo tripod; these are known as altitude-azimuth (or simply alt-az) mounts. Many reflectors come on an elegantly simple wooden platform, known as a Dobsonian, that's a variation of the alt-az mount. A more involved mechanism, designed to track the motion of the stars by turning on a single axis, is termed an equatorial mount. These tend to be larger and heavier than alt-az designs; to use an equatorial mount properly you'll also need to align it to Polaris, the North Star.
Some telescopes come with small motors to move them around the sky with the push of a keypad button. In the more advanced models of this type, often called "Go To" telescopes, a small computer is built into the hand control. Once you've entered the current date, time, and your location, the scope can point itself to, and track, thousands of celestial objects. Some "Go To"s let you choose a guided tour of the best celestial showpieces, complete with a digital readout describing what's known about each object.
But Go To scopes aren't for everyone — the setup process may be confusing if you don't know how to find the bright alignment stars in the sky. And lower-priced Go To models come with smaller apertures than similarly priced, entry-level scopes that have no electronics.
Remember …
A telescope can literally open your eyes to a universe of celestial delights. With a little care in selecting the right one, you'll be ready for a lifetime of exploring the night sky!


Tuesday, December 15, 2009

It was a great Meteor Shower

Well guys, the Geminids put on a great show!

I went down with 4 of my kids the Mahktesh Hakatan to camp out. We where met by Gadi and some of his kids and a guest, plus one of the new members to our list Yanki.

It was a great night. Unlike the forecast it was not too cold. Thanks to the Mahktesh, there was no wind, and the cold front did not roll in as expected, so it stayed clear all night.

I am too tired for a full report now, but we saw hundreds of meteors. After we cooked our hot dogs and set up our tents me and the kids layed down outside and counted at least 100 in the course of about an hour. By about 1am I nodded of inside my sleeping tent, but I think Gadi and the other guys where up most of the night. Hopefully they will add their reports soon.

You can see our campsite and group photo here:

The Geminids have been getting stronger for years now. According to Nasa it is expected to continue to improve. So be ready for next year.

For more reports and photos see Space Weather

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Sunday, December 13, 2009

Reminder Geminid Meteor shower tonight

Hi ya'll,

Mak sure to be on the lookout for meteors tonight.

APOD: 2009 December 12 - Geminid Meteor over Monument Valley

See Explanation.  Clicking on the picture will download  the highest resolution version available.

 I plan to camp out with the kids  in in Makhtesh hakatan tonight. Hopefully we'll find some clear skies down there.
If you want to join us, drop me a line.

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Sunday, December 6, 2009

Buying your 1st Telescope

Question: What sort of telescope would you recommend for a beginning astronomer (me) who has a child who is very interested in space?  (She is only 6, so of course interests might fade, but I would like to encourage it while I can).  I would like something decent enough that we can find and see interesting things, but hopefully not too expensive...
Also, would it be recommend to buy one here in Israel, or have it shipped from the states?  (Or even "manually imported" if I can find someone to schlep it...).  Is there a local second-hand telescope market here?


I often get asked that question. I need to work on a more complete  FAQ but here is a quick draft.

First of all, the best type of beginner scope is a pair of binoculars. Any old pair you have laying around the house will give you a better view than your eyes. If you don't already have a pair, you should invest in a quality pair 7x35 or  10x50 pair. (More on what those numbers mean in a future post) [or see the link below] Something like this model  should cost between $50-$100.  

When you are ready for a telescope I highly recommend a 4 and 1/2  inch Dobsonian model. Something like this: Orion SkyQuest XT4.5 Classic Dobsonian Telescope
Orion sells a great Skyquest model for a little more than $200. You'll note that this is a reflector type telescope, not the classic refraction you usually think of. More on the differences in a later post, but you get a lot more for your money with a Dobsonian reflector than any other model.

The 4.5 inch is big enough to get some very nice view of planets and clusters, but it is not too big that it  is a pain to schlep around. It also also very easy for kids (and adults) to work and aim (which is not trivial).

You can bring these  back pretty easily on a plane from the US. I know lots of people who have done it. It is delivered in 2 pieces. The unassembled base, which comes in a nice flat box you can check, and the tube, which you can carry on, and fits nicely in the overhead bin.

You can of course buy it in Israel, but since there is about one store in the country, it costs about twice as much. The Cosmos store is in Ramat Gan. The number is 03-6724303.

If you really have a small budget and are willing to invest in a scope you will probably outgrow quickly, there is a new quality scope the Celestron FirstScope. It is only 3 inches but a quality piece.

For more see also at Sky and Telescope
And some more links at Astronomy Magazine:
    Unlike the advice given in the video above, I do not  recommend a "GoTo" scope for beginners. A good Goto costs way too much and a cheap one will only frustrate you and take much of the fun and education out of the hobby.

    For the 2nd hand market, you can check out the Hebrew Nana astro forum.


    Thursday, December 3, 2009

    Busy month for planets

    December will be action packed with planets this year.

    At the beginning of the evening now, Jupiter is still the star of the show, but each night it is getting lower and lower into the haze in the southwest setting by 10pm.

    Have you all spied Mercury? If not this is a great month to catch this elusive planet. It is now visible in the southwest, right after sunset at magnitude -0.5. It will be at its max brightness of -.06 by next Friday. A week later on the 18th it will make a pretty pairing with the new moon just in time for Rosh Chodesh. A week later it will begin its quick plunge back toward the sun disappearing by years end.

    Mars is already magnitude 0 and still brightening and getting larger. By 10pm it is already up and getting higher each night. In a small scope you should be able to see the norther ice cap!

    You have to be up pretty late to catch Saturn as it only rises around 1:30am. But by by the end of the month it will be up by 11:30. It is recovering from the ring crossing earlier this year and they are now getting wider again.

    Venus, is still visible in the dawn sky, but is getting closer and closer to the sun till it disapears by month end. It will reappear in the evening sky, after a hiatus of about a year, by the end of January just in time to switch off with Jupiter as the evening star.

    Have any of you ever bagged Neptune? I don't think I have even ever tried, but if you have a decent scope this month is the month to try. It is actually very close to Jupiter, and they will be onlu .6 degrees apart (about the size of the (Moon) for a few days around the 21st.

    Oh and by the way, this month we also get a Blue Moon. This is when we have 2 full moons in one calendar month. The first one was last night, and the 2nd one will be on the last day of the month (and year) It of course has no astronomical significants, but you get to use the "once in a blue moon" adage.

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    Sunday, November 8, 2009

    ISS tonight, Eclipse conf at Open U, Leonids

    Tonight will be a very nice bright pass of the International Space Station over Israel.

    Starting at 5:35pm local time the ISS will rise in the west and head northeast. It will be visible until 5:41 when it enters the Earth's shadow about 15 degrees above the northeast horizon. It will be magnitude -2.7, just a bit brighter than Jupiter.

    For details see:

    The Open University in Raanana will be having an evening  conference on eclipses through history on Nov 19th starting at 5pm. See the details at

    And remeber, the Leonids will be returning on next Tue night the 17th. As I mentioned there is a forecast for a storm outburst around 11:45pm. We are not ideally located according as the radiant is still low at that hour, but these forecasts are not yet that precise. To cover your bets, you should go to as dark a spot as you can, and stay up all night!

    Keep looking up.

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    Monday, September 14, 2009

    In memory of Assaf Ramon, z'l and his father, Ilan Ramon, z'l

    The Astronomer pointed out to me that I had confused the Space Shuttle with the International Space Station, both of which are bright, man-made objects in the sky, orbiting the earth, and both of which cause my family to scoot off outside, typically at dinner time, to ooh and aah instead of sitting nicely and eating their vegetables. But they are, the Astronomer explained with great patience, two entirely different things, and I ought to understand the difference.

    But with the death of Assaf Ramon yesterday during an in-flight training exercise weighing heavily on our hearts, I thought instead of learning the difference between the SS (Space Shuttle) and the ISS (International Space Station) I would remind myself why Ilan Ramon, Assaf's father, was such an Israeli hero (our youngest son is named for him) and why sometimes a mother ought not to worry so much about missed dinners when there are Space Shuttles to be seen.

    As everyone knows, Ilan Ramon was the first (and only) Israeli astronaut, and a member of the SS (not ISS) Columbia's crew on its 28th (and last) mission. (An astronaut, by the way, is someone who travels in space, and space is defined (in the United States) as 50 miles above sea level.) He was in charge of scientific experiments being done on the mission. (This particular mission did not involve servicing any satellites, unlike previous Columbia missions.) We in our little Israeli town adored him because he asked for kosher food, made kiddush, and carried with him a miniature Torah scroll that had survived Bergen-Belsen.

    The Astronomer recalls getting up early, and a bit reluctantly, on the last morning (about 5 or 6AM Israeli time) of Ilan Ramon's flight, dragging the kids out of bed to wave at the Columbia as it passed over our heads.

    Because we don't use the radio or TV on the Jewish sabbath, it wasn't until after sunset that night, February 1, 2003, that we heard the news.

    It's a little more than 6 years later. Our youngest son Benjamin Ilan is about to celebrate his 6th birthday, our oldest son Joshua has just finished his basic training for the Israeli Air Force. And Assaf Ramon, Ilan's oldest son, is being buried this afternoon next to his father, Ilan. May Assaf and Ilan Ramon rest in peace, may their family be comforted.

    Wednesday, September 9, 2009

    The Space Shuttle and ISS flying in formation

    Did any of you catch the 2 of them tonight?

    Sorry I could not give you any advance warning, as I did not know when the space station and shuttle where going to separate. But as it happened, the shuttle pulled away from the ISS in preparation for its landing tomorrow. Thus the 2 crafts still follow almost exactly the same orbit, but a few hundred kilometers apart.

    At about 7:30 this evening they both passed our skies at a low angle. The shuttle came by 1st at a magnitude of 0.7. The sky was still blue and we had a lot of blowing clouds here, but the kids and I did find it as it came out of the clouds heading northwest. Then about a minute later the much larger shuttle, and therefore brighter at magnitude -1.2, came zooming after it. I was very excited to have caught it (and the kids thought it neat too!). Actually this was the last visible pass of the ISS for the next 2 weeks.


    Space Suttle Passes

                  About once every week or two, my husband, the Astronomer, grabs the kids up from the dinner table, napkins and crumbs flying, and exclaims "The shuttle!  The space shuttle's passing over!" Then they all charge out the door, leaving me alone at the table with a bunch of unfinished vegetables and congealing chicken.  The things we must endure . . .
                  Once I joined them.  Sure enough, right at its appointed time, a bright flying object—apparently the space shuttle (I'll take his word for it)--passed by at a steady clip across the night sky.  We all stared up for a minute or so and then trooped back in and finished dinner.
                  So what's the big deal with the space shuttle?  Why do we charge out to stare at it and not, say, an airplane? (Kids: Don't get any ideas.)
                  AstroTom says it's a big deal because men (let's assume he means people) built the shuttle and put it up there, and there are people in it.  I told him that this makes the space shuttle about as interesting as an airplane, which people also put up there, and considerably less interesting than a meteor, which people most certainly did not put up there.  Then he said that the space shuttle goes around the earth every 90 minutes, and is, in fact, in orbit
                  It turns out that being in orbit is actually interesting.  Being in orbit puts the space shuttle in a different category than airplanes, which fly but are not in orbit.  Something that's in orbit has been shot up there, sort of like a rocket to the moon, with a force great enough to "break the bonds of earth's gravity" as science writers are wont to say.  I can more easily relate to the force required to open the bag inside a box of cereal.  You have to pull the two sides apart but it has to be a controlled pull or your hands will fly apart and you'll end up with a jagged rip and cornflakes all over the room.  The shuttle had to be shot into the air with enough power to get it up in the air and keep it from falling right back down, but not so much that it would shoot up too high and wind up somewhere beyond Saturn.
                  How do they keep the shuttle up there in its neat circle, once it's off the earth?  Well, the Astronomer explained, using the drawings Newton made of a cannon on a mountain, the shuttle is actually falling all the time.  (Isn't that disconcerting?)  But, fortunately, the shuttle, like that ball fired by the cannon, is shot away hard and fast at an angle, not straight up, so that it neither shoots off into space nor ever falls back to the earth.  This last part works only because the earth is round.  If the earth were flat, the shuttle would eventually land, far far away.  But the earth isn't flat, so every time the shuttle goes far enough to land on the earth's surface, the surface curves out of its reach, and it keeps going.  Here's the neat part: This was all planned.  The initial thrust is just fast enough, and the angle is perfectly calibrated, so that the roundness of the earth balances out, or effectively cancels out, the pull of earth's gravity. 
                  But we tidy housewives know that stuff men put into space falls back to earth all the time.  (I heard it on an episode of "West Wing.")  How does that happen?  Does the shuttle run out of steam, eventually caving into the never-tiring power of gravity?  It turns out that friction is the culprit.  Space, even at 225 miles (360 km) high (which I'm told is relatively low), is not a perfect vacuum; the little bit of air causes enough friction to modestly slow down the speed of the space shuttle so that, over time, it would indeed surrender to gravity and fall on our heads if it were not periodically re-thrusted, given an extra boost to keep it going a while longer.
                  I still am not sure what those people are doing in the space shuttle, how long they're going to be there, and how much it's costing us tax payers to keep them there.  I also just heard that the "space shuttle" is not the same thing as the "international space station," which I kind of knew but never really thought about.  I'll ask the Astronomer the next time we all go rushing away from the dinner table.  

    The Astronomer's Wife