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Below are the 20 most recent journal entries recorded in
suitti's LiveJournal:
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| Wednesday, June 24th, 2009 | | 11:44 pm |
Free Astronomy software for observation planning
I'm giving a talk tomorrow at the Ford Club. It's just a short one. What software is available for free? All the software i use is available for free. But i start with my browser. I'm sure you have one. I use firefox (free) on Linux (free). It's good to know when it's dark. So i go to heavens-above, look up the Sun, and discover that it's 11:30 pm to 3:40 am. Short nights. I often start out my planning by going to Alice's site. I listen to her Astronomy A Go Go podcast. She's got a very, very sexy voice, and i could listen to it for hours. Which is a good thing because her monthly show is an hour long. Anyway, she's a bit behind this month. Still, she has a chart of meteor showers. Right now is the June Bootids meteor shower, fairly bright. June 22 - July 2. Worth a look, right? If i can get out to dark skies. She's got a link to Skymaps, so i download the current PDF. The first page has the map. It's got a calendar of events. The calendar has events like "on the 25th, the Moon will be next to the Beehive Cluster". I can find the Beehive without the Moon. And i'm pretty sure that i don't want to see the Beehive washed out by the Moon. But this may be really handy for beginners. Anyway, i ignore the calendar. I'd be more interested to find out that Venus is next to Mars (in the morning). So it might be a cool way to spot Mars. And Jupiter is next to Neptune. That might be a really easy way to find Neptune. The interesting thing is page two of the SkyMap. It has easy, medium and hard objects lists for the month - starting with Naked Eye. Just stars this month. Binocular objects are generally findable in my ten inch scope from my highly light polluted driveway. Telescope objects, not including galaxies, are also visible. I mostly look for things i haven't seen. There are two good comets pages. Skyhound isn't up to date. The header says June, but the data says May. I move on. This other page is pretty cool. And it looks like a 8th magnitude comet is in Pegasus. I bring that up in kstars, a free planetarium program. Really, "sudo apt-get install kstars" is the easy way to get it for Linux. Stars down to 16th magnitude. Pegasus is visible most of the night. And kstars knows where this C/2006 W3 Christensen is, so i can print a field finder chart. The Tools menu of kstars has a "What's Up Tonight" feature. The evening planet is Saturn. It sets around midnight. The morning planets are everything else. Mercury is pretty tough for me, as i don't have much of an Eastern horizon. But i saw Venus at 4:30 in the morning, and it was so bright i knew it was Venus without my glasses. I switch to Comets, and look up Christensen. It transits at 4:30 am. That's only a bit after astronomical night ends. Maybe 3:40 is a better time to look. The Asteroids list isn't very handy. Ceres is good. It's near Saturn in Leo. But if you look up Pallas, it turns out that it sets before it gets very dark. And Vesta is hopeless.  The kstars tools->Jupiters' Moons gives a chart. Usually i want to know which moon is which at some specific time. So, i set kstar's time, and zoom into Jupiter. Unfortunately, this doesn't work for Saturn. But Stellarium does this just fine. I don't generally use Stellarium, with all it's eye candy, to do planning. But this feature makes me fire it up. Stellarium has the feature that is works on Linux, Windows and Mac. And, did i mention, it has eye candy? Back to kstars. Sometimes, i just set the time, and look at the Zenith. Boom. There's Hercules. M13 and M92 are always worth a look. But the whole line from Polaris to the southern horizon is worth thinking about. Ophiuchus is near there, and that's where Pluto is. So i look for Pluto. It transits at 12:30 am, at 30 degrees up. Not bad! Or, i point kstars East, and see what's rising. When i've totally failed to do any planning, sometimes i let my telescope's computer suggest things. It's got 12 objects per month. And nearby months are OK. Or i just ask it for clusters in some constellation that's high in the sky. Or maybe double stars. But now we're not talking free. Unless you think "Free with a $700 telescope" is free. | | Sunday, April 12th, 2009 | | 12:15 pm |
What's the difference between a comet and a planet?
I've mentioned that i lurk on Yahoo! Answers (a complete waste of time), and answer questions from time to time. Here's an example where i attempted to not answer the question, while staying on topic, mostly. I should point out that other answers included the IAU's three points of the definition of a planet.  Planets are those things that got a really crappy definition by the IAU a couple years back. One feature of this definition is that they have to be massive enough to collapse into a rough sphere (hydrostatic equilibrium - if it's rotating, it can be fat at the equator). Comets have no official definition. Nor do asteroids. So both could be either. As it turns out, there are objects classified as asteroids that clearly had a tail at one time. Indeed, one of the annual meteor showers has particles that clearly come from an object that we currently call an asteroid. These particles are thought to come from the objects out-gassing, which would have formed a tail. To make the definition matters worse, asteroids are officially cataloged as "minor planets". Two of the minor planets, 1 Ceres, and 134340 Pluto, also have the classification of "Dwarf Planets". Clearly, not all asteroids are Dwarf Planets, but at least some Dwarf Planets are asteroids. So one could argue (and i'm doing that now) that comets are closely related to planets.  However, comets are generally described as objects that do out gassing, sometimes have tails, and so on. They're not generally described as "spherical", and indeed, the ones whose cores have been imaged look something like lumpy potatoes. But planets can and do have tails. Planets with atmospheres have some bits of their atmosphere blown into space by the solar wind, etc. For some of the hot Jupiters found around other stars, this super heated atmosphere is blown out into space as a very visible tail. I don't expect an object with Jupiter+ mass to be called a comet, but i do expect the IAU to completely mess up the definition of comet when they get around to it. It appears that finding a large object causes astronomers in general to become stupid. We got poorly defined minor planets soon after Ceres was discovered and studied for 50 years. We then got poorly defined planets when Eris was discovered. Stupidity like this can only come from large committees. Group intelligence seems to go down as you add more people. So even a group of PhD astronomers, when taken by the thousand, are incredibly stupid. So imagine Congress, where a PhD isn't required. IMO, the IAU should be disbanded, and replaced by a peer review system. Peer review, at the very least, is fairly fast, and has been shown to work. It also has self checking for those cases where it doesn't. | | Sunday, March 22nd, 2009 | | 9:52 pm |
Find Polaris
This is extremely unusual. I was listening to an episode of the 365 Days of Astronomy podcast. I happen to finish listening to the March 16th episode just as i was getting home, at night, and it was clear out. It's so seldom clear out. The episode is entitled Using the Sun to Find the North Star. It talks about how you can go out during the day at solar noon, and where i live in the Northern Hemisphere, your shadow will point North. So if you mark where that is during the day, you'll be able to find the Polaris, the North Star, at night. Up until that moment, i'd been thinking that i know how to find Polaris, and certainly wasn't going to figure out when solar noon is at my western edge of a time zone, and daylight savings, and all that (though now that i think of it, my planetarium program will tell me exactly when that is), wait till that point in time on a clear day (it's nearly never clear), and put a landmark somewhere along my shadow. But as my driveway is my primary observing spot, and as i was there, it couldn't hurt to see what sort of landmark i could use. It was only a few seconds, and i could say, "there are the pointer stars of the bowl of the Big Dipper, so that is Polaris". Could my basketball hoop be used? As it turns out, when the basketball backboard just blocks out the street lamp, the post holding the basketball hoop points straight up at Polaris. I don't need a landmark, i have one. And, as that's where the street lamp is blocked, this patch of grass is where the scope should go, at least when there's no snow. I've been doing it sub-optimally all this time. Hey. It's clear. Time to get out the scope! | | Friday, March 6th, 2009 | | 4:02 pm |
Where can you name a star for free?
This is more from my adventures on Yahoo! Answers. As i've said, a complete waste of time. Here's my answer:  Here's a trick that i've used to good effect. I picked a really, really bright star that happens to be nearly due north. I watched it a bit, and it doesn't move much, all night. Most of the other stars seem to circle it. I named it "Polaris". I didn't go to a web site and buy the star name. I didn't even write it down. It just thought it was a good name for the star. You know, cause it's right there by the pole. When i looked it up in a planetarium program, to my astonishment, they used the very same name for the star! It's official. So, as a follow up, i was looking at Leo. There's this one really, really bright star. And i thought, "Hey, that's the King star of Leo." And lions are the kings of the beasts. And, i'd read Harry Potter. So i called it "Regulus". It's a great name for a great star. And guess what? That's what my planetarium calls it. That's two, and completely free! | | Friday, February 6th, 2009 | | 1:32 pm |
Spotting alien Earths on the cheap
Every now and then, there's a news article where they talk about something that might be interesting for astronomy. There was the meta materials article where they talked about achieving, in the lab, a substance with a negative index of refraction. The work was done in microwaves, which are a good deal longer than visible light. So, although a visible light version would be much, much harder to do, there wasn't anything in physics that suggested it was impossible. And the interesting thing is that such optics might be able to produce images with a resolution limit ten times smaller than the diffraction limit we normally get. Even if it were incredibly expensive, it would make a 3 meter space telescope act like a 30 meter space telescope. But though it's been years since this announcement, i've not heard anything more about it. So here's another idea. Read this article. I'm not going to repeat the article here. The idea is to sort of combine lucky imaging with adaptive optics. Take lots of images, but treat the pixels independently, to improve the wavefront of the distorted light. You're still using today's massive compute power to make the final image work. And, the article says to expect real results in months. I've done estimating before. Take the original reasonable estimate, double it, then change the units up one. So if they say 5 years, then it's doubled to 10, and instead of years, you have decades. But if the estimate is 2 months, double it to 4 months, then change months to years - 4 years. This estimating technique is scary on how accurate it is. And though 4 years sounds like a long time, it's not. This is very exciting. | | Thursday, February 5th, 2009 | | 9:48 pm |
Astronomical Night
 Astronomy has these big numbers. Tens of trillions of miles to the nearest star. Now, i can cope with a million. A million seconds is a couple weeks. But a million fortnights isn't part of my intuitive understanding. So we talk about "astronomical distance". So the adjective "astronomical" seems to mean "inconceivably huge". And i've heard it used without numeric meaning, such as "astronomically stupid". It might have been about GW, but that's water under the bridge. After sundown comes civil twilight, then naval twilight, then astronomical twilight. And when the Sun is 18 degrees below the horizon, it's astronomical night. And you'd expect it to be incomparably dark. And as a metaphor it ought to be something deeply disturbing - like the death of your spouse or your child, or a depressing contemplation of your own mortality. It's alluring. But when you actually go out under clear skies and the Moon hasn't risen, with minimal light pollution in astronomical night, the Milky Way shines brightly, and it's totally gorgeous. And it's not that dark. You don't need a flashlight to find your scope or goof around with the focuser after changing eyepieces. Your eyes have adjusted. | | Friday, January 16th, 2009 | | 11:50 pm |
It's cold out there
So, i was going to go somewhere darker. But it was -4 degrees F, maybe 5 MPH wind. I moved the car to a spot in the driveway where i could load the scope, realized that it was crazy to expect to be able to stay out for more than a few minutes at a time. So i set up the 10" on the sidewalk in front of the house. I turned on the primary mirror fan, and went back inside for a bit. I kept my scope's computer inside for this. I've been having some problems with it. And it clearly doesn't like the cold very much. I have a fresh battery. The issue is that the display gets sluggish in the cold. But i've also been having problems getting an alignment. When i thought the mirror might have reached ambient, i went back out. I plugged in the computer, and tried several alignments. Rigel and Castor, making sure Castor is a double star, and double checking Rigel. No go. Sirius and Capella. Betelgeuse and Capella. The computer gives feedback on how good the alignment is, and this one worked! However, a check with M42 showed that it was some 3 degrees off, entirely in altitude. So maybe there's a problem with the altitude encoder. I went back inside to warm up for a bit. And ten minutes later i went out again. The computer was on, but the display was blank. Nothing to be done about it. I unplugged the computer, and brought it inside. I checked out my new Q70 on M45 - the Pleiades. In contrast with Tuesday, the entire Pleides fits in the field of view. Well, on Tuesday, i was concentrating on outreach, so didn't really examine it in detail. However, none of the stars are the pinpoints i've come to expect from my scope. My guess is that my collimation is messed up. I was able to get much better views with a borrowed 38 mm Q70 on Thanksgiving Eve in my scope. It's even possible that the primary mirror is flopping around. That might explain my alignment issues. Fortunately, these things can be checked in the comfort of a warm house. | | Thursday, January 15th, 2009 | | 2:09 pm |
These three things
Tuesday night, three big things happened in astronomy that were very important. Important to me, anyway. First, when i got home from work, there was a package waiting for me. It was my new 2" Q70 eyepiece on sale at Orion. I'd done my homework. My scope has an aperture of 254 mm. My eye's pupil dilates to 6 mm (measured with hex wrenches against Sirius). So the optimal wide field magnification is 254 / 6 = 42x. The focal length of the scope is 1200 mm, so the optimal wide field eyepiece focal length is 1200 / 42 = 28 mm. This is similar to my 25 mm eyepiece, so i could just stick with it. So, i'm done, right? I don't have to buy anything. However, i want a wider field of view. If i have to toss a little light away, that's not a big deal. The Q70 has a 70 degree apparent field of view (AFOV). My 25 mm has a 52 degree AFOV. So that's a 34% bigger field of view (FOV). Then it's 38 mm instead of 25 mm, so that's 52% lower magnification. Combine these: 1.34 * 1.52 = 2 times the FOV. The magnification is 31.6x, and the exit pupil is 8 mm. Well, when i do outreach, some of the kids are bound to have an 8 mm dilated pupil. So while i may only detect 55% of the light, some of these kids will get it all. The second interesting thing was that, in a break with tradition, it was a clear night. Normally, if you get some new toy in the mail, then the skies are opaque or worse. But the skies were crystal clear. Third the Ford club had an outreach program. Kids between about 3rd grade and 6th grade (i'm just guessing) got treated to a quick introduction to astronomy, and we showed them a few objects in our telescopes. The flood lights in the parking lot were pretty rude, and i wasn't able to get a good alignment on my scope's computer. I had trouble finding Rigel in my finder scope, due to the glare. But i showed the kids M42 - the Great Orion Nebula. And i showed them M45, the Pleiades star cluster in the new Q70. No, the Q70 does not have enough FOV to show the entire cluster. And, i didn't get a chance to do an A/B comparison with my 25 mm eyepiece. Another night. It was very cold, and i've no idea if my electric socks were working or not. I'd let my feet get wet, which is always a bad thing to do. Just 12 degrees F, but no wind. All in all, a great event, and lots of fun. | | Tuesday, January 13th, 2009 | | 4:05 pm |
What's your attitude towards the idea of an identical Universe?
All atoms of a type are identical. So if the arrangement of atoms that is me is duplicated somewhere else, then there is another me. However, i do not magically communicate with my other, so we are two, not one. If the Universe is in fact infinite (as suggested by String Theory), then the arrangements of atoms or even subatomic particles is finite for any region. There must, in fact, be an infinite number of identical copies of me, typing these words, with you reading them. The nearest of these has been computed to be about 10^(10^29000) light years, in any direction from here, with lots of near copies on the way there. I wish them luck. That's pretty selfish, really. Since they're identical, they're wishing me luck. | | Wednesday, January 7th, 2009 | | 12:21 pm |
Why send people into space?
The last estimate i've heard is that robotic missions are about a factor of 10 more economical that those with people. You've got to have more reliable transport, food, air, etc., for people. But this analysis makes some assumptions, which are mostly forgotten in this sound byte world we've built. The assumptions are that the goal is scientific results, and that only monetary costs are important, and probably others. The Mars rovers have been doing a great job at geology for the past five years. Totally off the wall fabulous. But in a typical day, they move several feet, take a few pictures, and maybe move the arm to some object and take a few measurements. Great science, but a human could do that sort of work every few minutes for hours every day she's there. And at the end of her many months mission, she'd have advanced the geology of Mars science by a century of what the rover could do. Sure it would cost more. Sure, the same money spent on robotic missions would get more science. But the robots would take a century, even assuming lots of simultaneous missions. Jack Schmitt (Apollo 17 geologist) was off the wall amazing. It's really too bad that the next couple flights were canceled, and they waited so long to put a geologist on the Moon. There's only so much geology training you can do with astronauts. And that's why NASA is training geologists, biologists, etc., as astronauts. They've already got their decade+ of PhD grade research in some specialty under their belt. This is depth you don't get in sound bytes. The assumption that the only reason for going into space is science is also suspect. There's also the adventure and exploration. You can't think clearly about a Mars colony if you haven't put people there. The Earth is the cradle of civilization. But you can't stay in the cradle forever. | | Tuesday, January 6th, 2009 | | 5:50 pm |
Dwarf planets
So "Dwarf Planets" are planets, too, right? How to remember them? My very energetic mother, Cloe, just served us nine pizzas, had mine entirely! This adds dwarf planets Ceres (between Mars and Jupiter), Haumea, Makemake, and Eris. | | Sunday, January 4th, 2009 | | 4:46 pm |
Observing plans ignored
Last night it was crystal clear, but cold. I tried out my new electric socks. They worked great. 25 degrees F. But i'd made an observing plan based on my driveway, then peeked out the back only to see Orion big as life. I checked to see if i could do my 2 star alignment (there's no horizon and limited visibility - it's darker, that's why i use it. I could. So i set up in back, turned on the fan to cool the mirror, and, in the mean time, looked at Orion. None of the stuff from my plan was visible, so i asked my scope's computer for clusters in Orion. I went down the list. Then i looked at clusters in Auriga, which was straight overhead. After a couple successes, i stopped being able to find them. Then, i failed to find M38. That's absurd. So i checked my alignment, and somehow, i was off by some 5 degrees. No wonder. I decided to bring the scope to the driveway to get back to the plan. I did my 2 star alignment. It more or less failed. I tried again, and got excellent alignment. First object is a cluster near the North Pole - NGC 188. I'm interested in it because, as something near the North Pole, i might be able to get an image of it with my camera with my non-tracking Dob. The idea is, it won't move that much. But by the time i got anywhere near it, there wasn't anything in the eyepiece. I looked up to see that a cloud was there instead. I looked around, and two of the stars of the Big Dipper were visible - nothing else. And in just seconds, even that was gone. I got back in, and updated my log. It turns out that i'd only seen things i'd seen before, contrary to the plan. Next time: stick to the plan. | | Wednesday, December 31st, 2008 | | 8:46 pm |
Jupiter
 Back in 2004, i shot this image with a non-tracking dob and a 2 megapixel point and shoot digital camera held up to the eyepiece by hand. I shot 54 images to get one "best" image. Most are totally awful. The only post processing is cropping. You can see the planet and one of the moons. The moon is Io. Some of the other shots show (but not very well) Europa and Io on one side, and Ganymede on the other side. Callisto is behind the planet. | | Thursday, December 18th, 2008 | | 2:54 pm |
Why is the Fomalhaut B planet image so significant?
This is more from my Yahoo Answers (waste of time) files. The question: On November 13, 2008, NASA announced that the Hubble Space Telescope has taken a snapshot of a planet circling the star Fomalhaut. Obviously, this is the first planet other than our own that we know of orbits a base star. Other than this, why was this such a significant discovery? My answer:  The answer is related to the fact that the HST took the images in 2004 and 2006, and only just recently announced. Why wait? The researchers waited because they wanted more time to study the images. It'd be really nice to have gotten a third shot in 2008, but the ACS camera on the HST which was used for the first two shots is broken. It was expected to be repaired a couple months ago, but then the servicing mission was delayed. So, what's to study? It's not just a planet, it's a planet in a debris ring around the young star. So you have to sort of subtract the brightness of the ring to find the brightness of the planet. And the planet is brighter than expected. Perhaps it has rings like Saturn reflecting lots of light from the star. But more than that, one would like to see evidence of other planets forming. So there's lots to do. What about the timing of the news release? Another image of planets in the same issue of Science? It doesn't look like a coincidence. The researchers waited as long as they could. IMO, they should have announced it soon after they'd figured out that it was a real effect in 2006. Then in 2009, when they snap their third shot, they could confirm it. Perhaps they've gotten time on the Keck or the VLT and gotten more recent data... But imaging an extrasolar planet is a big deal. Being the first to do it in visible light is more bragging rights than a big deal, however. And this isn't the first planet that has been imaged. So, they went for a sound byte rather than explain that they're doing really cool planet formation science. One of the troubles with sound byte science is that it's more of the same memorization of stupid facts that turns kids off to science in school. The cool stuff about science is getting your hands dirty doing experiments. Making mistakes. Getting results. I had much more fun measuring the speed of light - with a 3% error - than i'd ever have just memorizing the speed of light. If you want to accelerate the advancement of science, then push yourself to make mistakes faster. It's true for education as well. | | Wednesday, December 17th, 2008 | | 5:54 pm |
| | Thursday, November 27th, 2008 | | 6:37 pm |
Low power 2" eyepieces
 By the way. If i've said something stupid here, please let me know. I'm still pretty new at this.
John C. and i were out at Island Lake last night. I arrived around 9 pm or so, and left around 2 am, i think. I don't carry a watch. It was cloudy when i arrived, though the sky clock said that it was already clear. John had access to a cloud weather map, and it showed we were on the edge. It wasn't obvious that it was going to clear. It mostly cleared about a half hour after i arrived. John said he was just about to leave when i arrived! You could see the line of clouds once it cleared. It never completely cleared. There was always something to the North. It was cold, but i've no idea how cold it was. We had no trouble with dew or frost on the scopes, but my car had frost all over it at the end. It's a good thing we didn't have troubles: i forgot my dew heater batteries. My electric socks clearly aren't working at all. At least they're wool socks. The cold gave me a kind of impatience with everything. In fact, the alignment on my scope's computer drifted off by some 5 degrees, and i didn't bother to re-align. My best guess is that it melted into the snow, which changed it's orientation. It's hard to believe that come March, a night like this will seem warm. As a point of fact, i don't believe it.
So i got to goof around with a bunch of John's 2" eyepieces, and also the 36 mm 2" eyepiece that Jon Blum loaned me. And just before leaving, we did the allen wrench test.
When the sky cleared enough to see the Little Dipper, at first, i could see all but one of the stars. But by blocking the reflection of whatever city it is to the North's light dome with my arm, all the Little Dipper stars became apparent, without averted vision. The Moon was not up - and it would have been near New anyway. They say that if you block the glare from Jupiter with a building or something, you can see Ganymede. I've never tried it, but i'm starting to believe it.
All the eyepieces were great. Well, i continue to not be very fond of zoom eyepieces. But since John C. finds objects via the thrill of the hunt, rather than with a computer like i do, i can see the attraction. You often want to fine tune the magnification to the object you're looking for. With the computer, i usually get to the field, or close to it, and then look using the optimal eyepiece (optimal for what i have, with is a 25 mm a 10 mm and the 10 mm with a 2x barlow). Which is to say, 48x, 120x, and 240x.
Once it cleared, i pointed my scope at the double cluster in Perseus. It fits in my 25 mm 1.25" eyepiece, touching the edges. But it fits easily in these 30+ mm 2" eyepieces. We also looked at M42 and the surrounding area. When i'd exhausted my experiments, i abandoned my scope, and we looked for stuff in John's Lightbridge. I didn't take notes, but we saw the Eskimo nebula, m33, m31, m32, m110, a couple other NGC galaxies and probably a few other things. I don't usually ever abandon my scope. But i was cold.
I want a low power eyepiece for wide fields. But i'm starting to see why someone would want wider field of view at higher power in the hunt.
Anyway, as i said, all the eyepieces were great. However, all the 2" eyepieces have a wide enough apparent field of view that there is significant coma in the outer half to a third of the view. Basically, i could focus for the center or for the edges. This isn't a problem for my 1.25" 25 mm eyepiece. The field isn't wide enough. Really it's only the size of the center bit in 2" eyepieces. John C. has a Paracorr, and that sharpened up the whole field for all eyepieces. This was a new idea for me. I thought that as the Paracorr is designed for focal ratios under 5, i expected i might get away with it on my F4.7 scope. Apparently what they mean is anything under F5. So, i don't just need a wide field 2" eyepiece, i need a Paracorr too. That increases the cost. But i won't need the Paracorr right away - a low power eyepiece will clearly be valuable on it's own. And, there's another issue. Some of the big objects, like the Veil, i'll want an oxygen 3 filter. My 1.25" oxygen 3 filter isn't going to do it - i need a 2" oxygen 3 filter.
Another note on the Paracorr. You need to have a TeleVue eyepiece to figure out how to adjust the Paracorr for non TeleVue eyepieces. This gives TeleVue eyepieces a slight edge. After all, you only need to do this once, as the adjustment never changes for an eyepiece/telescope combination. And you can always borrow one just long enough to do the test.
My 10" scope, which looks like a cannon next to even an 8" scope, looks positively cute next to John C.'s 16" Lightbridge. The 16" has 2.5 times the area of a 10", so it pulls in an extra magnitude. Curiously, while Orion claims 15th magnitude for my 10", Meade claims less for the 16". I've seen Pluto, magnitude 13.7 in my 10". In darker skies, it seems reasonable that i'd do better, if only because my eyes might be better dark adapted. So my guess is that the 16" Lightbridge can reach 16th magnitude in very dark skies.
Before we left, i got out the allen wrench set, and set it on the frost covered trunk of my car. Everything wanted desperately to slide off into the snow in the parking lot. I sorted them by size. It was extremely difficult to read the numbers on the wrenches. I had contact lenses that make me far sighted - so i was using Dollar Store reading glasses, with a red light. At 50 years of age, my pupils might be expected to dilate to 5mm. Using Sirius as the star, the largest wrench that didn't fully block the star was the 5.5 mm wrench. The 6 mm fully blocked it. I attempted to rotate the 5.5 mm wrench to see if it might block it during the rotation. My idea was to do some math and figure out how fat it was at some estimated angle. But rotation didn't change it any. So, 6 mm pupil size. From time to time, i'm at a darker sky site than this. It will be interesting to revisit the test. It might be the same.
Why is this important? Maximum brightness happens when the exit pupil of the scope/eyepiece is the same as your pupil's size. For a 254 mm aperture scope, and the expected 5 mm pupil, the magnification is 254 / 5 = 50.8x, and for a 1200 mm focal length scope, this corresponds to a 1200 / 50.8 = 23.6 mm. That would suggest that the 25 mm eyepiece i have is already too large, though near optimum brightness. But with a 6 mm pupil, the math changes. 254 / 6 = 42x, and 1200 / 42 = 28 mm for an eyepiece.
The eyepieces that i evaluated were all more than 28 mm. So they were probably all slightly less bright than optimal. If so, i couldn't tell. Math is good, but if i can't tell the difference, there is no difference. Please don't confuse me with the facts. Longer focal length eyepieces, even if suboptimal in brightness, still have larger field of view. And, who knows, i might have a younger guest at the eyepiece for whom it would be brighter. I may have mentioned that i like to do outreach. The things i wanted to test for were if there was center darkening, like i'm looking at the shadow of my secondary, and some sort of effect where i'm looking at the inside edges of my scope. I detected nothing of this in any of the 2" eyepieces using my scope.
It sounds as if one could easily fall into eyepiece fever, just like aperture fever. I know more than one person who has a large scope that goes unused since it takes two or three people to set it up. But i've seen 18" and now 28" truss dobs set up by single individuals. And there's a report of a guy who says he can get a 16" Lightbridge into his Prius. The Prius is a hatchback, but it's not a big vehicle. So, maybe there's room for aperture fever after all. I'm still addicted to my under 3 minute setup time - including 2 star alignment. Once you get out of the nice warm car, the timer is ticking before you have to go home. But even if i succumb to aperture fever one day, my 10" will still be my grab and go scope.
My conclusion so far is that, despite not having tried one, the 31 mm type 5 Nagler that costs $640 may not be significantly better than a $100 32 mm Q70. A Q70 could become part of my collection much sooner than a type 5 could. I'm still curious how good such a beast works. | | Tuesday, October 21st, 2008 | | 2:24 pm |
Drake Equation
 Frank Drake came out with the Drake Equation in 1960. There are several formulations of it, but very similar. And though we know quite a bit more about the elements of the problem now, such as the fraction of stars with planets, not much has changed about how to go about doing the math. Until now. The new idea is to actually simulate many times over, the number of civilizations that may have appeared in a galaxy like ours using reasonable, modern estimates for the values in the Drake equation. With these statistics you can calculate an average value and a standard deviation for the number of advanced civilizations in our galaxy. It allows you to compare the results of different models of civilization creation. Horgan has clearly had some fun comparing three models: panspermia (if life forms on one planet, it can spread to others in a system) predicts 37,964.97 advanced civilizations in our galaxy with a standard deviation of 20. The rare life hypothesis (Earth-like planets are rare but life progresses pretty well on them when they occur) predicts 361.2 advanced civilizations with an standard deviation of 2. The tortoise and hare hypothesis (Earth-like plants are common but the steps towards civilization are hard) predicts 31,573.52 with an standard deviation of 20. Obviously, the more there are, the better the chances that one will be near us, making it easier to talk to. Let's assume the galaxy is flat. Well, it's 3,000 light years thick here. Let's say that civilizations are evenly distributed by area. The galaxy is 100,000 light years across. So the area is 50,000^2*pi square light years. Divide this by the number of civilizations to get a rough idea how far they might be from each other. If there are only 361, then the nearest one could be 4,664 light years from us, and we'll have to scan an area of 21,756,181 square light years. If there are 37,964.97 civilizations, then we have to search 206,874 square light years - to a radius of 454 light years. Given that we are finding planets around stars that far out, this is a problem that's starting to look feasible. We still have to scan the height of the galaxy, about 1500 light years North and South. | | 11:34 am |
The Sun
Just a quick link. Lots of big, pretty pictures of the Sun, with annotations. I disagree with the "200 days without a Sun Spot" quote. Even August without a Sun Spot is debatable. No doubt that this Solar minimum is, well, minimal. | | 10:33 am |
Good seeing
When i go out with my 10 inch (254 mm) telescope, the less turbulent and more transparent the atmosphere, the better. I often look nearly straight up with the scope, despite the fact that tracking an object directly overhead can be a nuisance in a Dob style scope. I do this because there is less atmosphere straight up. That means better seeing, it means less light pollution. It's just better. But there are observatories that don't do this. These astronomical observatories are worried about "light pollution" so much that they are placed underground. The Super-Kamiokande in Japan is located a kilometer (0.6 miles) below ground level in a zinc mine. It uses 50,000 tons of pure water in a cylindrical stainless steel tank as a detector. Photocathodes actually collect the signals. They're looking for neutrinos. The system is sensitive to lots of stuff, so it's underground to eliminate everything but neutrinos. Does it only look straight up through a kilometer of rock? No. It's omnidirectional. Neutrinos are easily capable of passing through the Earth and get detected. If a neutrino can ignore the Earth, how is it possible to detect them? Well, most of them are missed even when they pass through the detector. OK, so this observatory has a 1 pixel camera. And it looks in every direction at once. Can you tell which way a signal is coming from? Well, you might. If you have three such observatories, and the signals are timed, you may be able to figure out where a signal is coming from from the difference in time that each detector saw the signal. For that, you need an event, like a supernova that changes the number of neutrinos detected. | | Thursday, October 16th, 2008 | | 2:43 pm |
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