http://cseligman.com/ Recent announcements for cseligman.com> en-us Fri, 31 Dec 2010 04:00:00 PST Fri, 02 Sep 2011 07:45:02 PST http://www.about.me/courtneyseligman#110902 Tue, 31 Jan 2012 15:55:02 PST We have to get started on the practice sheet for the Mercury Project tonight, and there is a lot to go over aside from having students do what they can and show me what they've done, to make sure they are doing it correctly; so we will not be going on the roof even if it is clear. I will have a couple of dozen rolls of the 12-foot long graph paper needed for part 1 of the Mercury Project with me, so students who feel they are ready to start on that before they leave will have a chance to buy a roll. The practice sheets are free, but the 12-foot rolls are $7; so if you think you might be ready to start on a roll within the next week or so you should bring $7 (exact "change") with you, as I don't provide them "on loan". http://cseligman.com/announce.htm#120131a Mon, 30 Jan 2012 08:55:02 PST The previously posted template for the Moon Project doesn't seem to provide quite enough room to comfortably include both the required information and a large enough drawing of the moon, so I have posted a revised template that provides a little more room. You do not have to use this (or the previously posted) template for the project (and if you want to do larger more detailed drawings will not be able to), but if you want to try it out, it is posted at http://cseligman.com/laboratory/Moon.pdf. This note and some comments about turning in your Moon Project will be moved to the Moon Project page within the next couple of weeks; but since the project doesn't have to be turned in until May, that should provide plenty of "advance notice" of what you need to do. http://cseligman.com/announce.htm#120130 Tue, 31 Jan 2012 08:55:02 PST This is an incomplete list and will be updated within a couple of days, but some items are critical, so I'm posting it as-is for now: (1) Textbook Reading Assignments -- the first few pages of chapters 1, 3 and 8, and all of chapter 15 (do not "study" the material; just read it enough to get a basic understanding of what is there and to remember that you've seen it somewhere). (2) Lab Class Information Page Reading Assignments (aside from those already posted below) -- Print out the first Mercury Project Data Page prior to the next class meeting (either the Web-based or PDF versions are OK for now, but the PDF version is better in the long run; TUESDAY STUDENTS SHOULD NOTE THAT THE "NEXT" MEETING IS JANUARY 31) and read (but do not "study") the first half of Part 1 of the Mercury Project (I'll be going over that in detail at the "next" meeting). (3) Online Text Reading Assignments -- the first half of The Motion of the Moon, the pages on Star Names, the Celestial Sphere, and Astronomical Coordinates, and Rotation Period and Day Length (as with all the other reading assignments, just read through it for basic understanding; do not "study" it). There may be additional reading assignments posted that I have temporarily forgotten, so check for any changes later in the week. http://cseligman.com/announce.htm#120131 Wed, 25 Jan 2012 08:55:02 PST The least expensive working sextant made is the Davis Mark 3. At the moment, the cheapest offer appears to be an eBay Buy It Now offer for $31.68, including free shipping (item number 190599212789), but it is available from a number of sources for less than $50. http://cseligman.com/announce.htm#120125a Sat, 14 Jan 2012 21:45:02 PST The initial lab class assignments and notes have now been posted at Recent Announcements (http://cseligman.com/announce.htm). Everyone should read them ASAP. Some 2012 updates still need to be made (as noted in an earlier post), but may not be completed until sometime next week, due to the backlog of paperwork and emails I'm still struggling with. http://cseligman.com/announce.htm#120114 Wed, 04 Jan 2012 23:51:02 PST I need to make a few minor changes to the website notes for my Astronomy Lab class (for instance, the graph paper I provide for part 1 of the Mercury Project has gone up in price, and I now have to charge $7 per roll, instead of $6). As a result, although interested students can start reading about the class right away, they should not assume that anything is set in stone until I say so. http://cseligman.com/announce.htm#120104d Tue, 29 Nov 2011 23:19:02 PST Posted a map of Ursa Minor that shows the precession of the Pole over the last 4800 years (click the RSS link to see the page in question). http://cseligman.com/text/atlas/ursaminor.htm Fri, 25 Mar 2011 01:30:00 PST Concerning the announcement of the discovery of a brown dwarf of about 6 Jupiter masses, about 75 light years from the Earth: Artist's conception illustrations showing the 100 Celsius (about the temperature of boiling water) surface temperature "brown dwarf" are misleading, in that such an object would give off no visible radiation (it and its brighter companion are only observable with infrared telescopes). Since the quotes from the research paper concentrated on the cooler brown dwarf, and did not mention the temperature of the hotter one, it is conceivable that the brighter one is giving off small amounts of visible light, in which case the cooler one might be visible (from within the binary system) by light reflected off it, in the same way that planets are. In fact, the bluish color of the cool brown dwarf suggests that its atmospheric dynamics are very similar to those of the Jovian planets; and at only 6 Jupiter masses, it might be more appropriate to call it a hot Jupiter, than a brown dwarf. Exactly where the line should be drawn between large planets and small stars (that is, brown dwarfs) is a matter of very poor guesswork; but odds are that it is closer to 20 to 50 Jupiter masses, than to 6. So this may not really be the coolest brown dwarf ever observed, but simply the first super-Jupiter observed in any detail. Either way, it is an interesting discovery; but as pointed out at the start of this note, the illustrations popping up all over the Internet showing the star brightly glowing are completely wrong (as can be easily seen by looking at DSS or SDSS images of the region, which show absolutely nothing at the specified location). <br><br> http://cseligman.com/announce.htm#110325 Sat, 19 Mar 2011 02:20:00 PST Posted a discussion of the so-called "super" full moon of March 19, 2011 at http://cseligman.com/text/moons/earthmoonpix.htm (just like any full moon, it should be a very pretty sight; but otherwise, there's nothing "super" about it, at all) <br><br> http://cseligman.com/text/moons/earthmoonpix.htm#xx