February 2013 - Utah-Astronomy - mailman.xmission.com

Re: [Utah-astronomy] Surprising skies
by Jay Eads 07 Feb '13

07 Feb '13

Joe, Tuesday and Wednesday were just wonderful nights. No humidity, temps in the low 30's. On Tuesday, Mat, Jorge, Daniel and I were at the Pit. We started observing around 7:00pm and we concluded at 11:30pm. On Wednesday I went solo and was set up at 5:30pm, observing at 6:00pm and packed up at 11:00 and home before 12:00. I unloaded today after work. That is what I LOVE about this time of the year. If one dresses for the cold one can start earlier and get in a good four or five hours even on a work night. A week from tomorrow (IF long term forecasts can be believed) looks wonderful with a thin waxing crescent sinking around 8:15pm and I am going to head out to Vernon that night.

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Re: [Utah-astronomy] Math problem: vectors for planet axial tilt
by Joe Bauman 07 Feb '13

07 Feb '13

SIMPLE?? ------------------------------ On Thu, Feb 7, 2013 4:21 PM MST Dion Davidson wrote: >Brent >Thanks. You are right. I found this simple equation >xyz = [cos(dec)*cos(ra), cos(dec)*sin(ra), sin(dec)] >which works when ra and dec are given in radians > >I have to do a little translation since the z-axis in my coordinate system is perpendicular to the ecliptic, where in the equatorial system the z-axis is aligned with the earth's axis of rotation. Should be easy enough, if I can just remember vector math (add? subtract? cross product? dot product?) >Thanks again >Dion > > > >________________________________ > From: Brent Watson <brentjwatson(a)yahoo.com> >To: Utah Astronomy <utah-astronomy(a)mailman.xmission.com> >Sent: Thursday, February 7, 2013 3:10 PM >Subject: Re: [Utah-astronomy] Math problem: vectors for planet axial tilt > >Dion, > >You can use the RA and DEC for pointing your aves. The stars are far enough away that tere is negligible change in direction. What will cause errors is precession, but that happens over such a long time period (tens of thousands of years) that it shouldn't make any difference. I believe you'll be good by just using the RA and DEC. > >Brent > >From: Dion Davidson <diondavidson(a)yahoo.com> >To: "Utah-Astronomy(a)mailman.xmission.com" <Utah-Astronomy(a)mailman.xmission.com> >Sent: Thursday, February 7, 2013 9:14 AM >Subject: [Utah-astronomy] Math problem: vectors for planet axial tilt > >I'm working on a visual simulation of the solar system for presentation to a homeschool group. I'm using GlowScript (very cool - a lot like VPython). The theme of the presentation is "Why don't things line up?" and I want to highlight how axial rotations and orbital planes don't really line up in our solar system. I can see from nasa fact pages the angle of axial tilt for each planet, which I assume is the angle between the rotation axis and the orbital plane of the planet (as opposed to the ecliptic). (ex: http://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html) > >Here's my question: what is the vector that represents these axes in 3D? Right now all my axes point in the same (roughtly celestial north) direction, which is less interesting than real-life, I assume. I see a section titled "North Pole of Rotation" which gives an RA and Dec for each planet. Does that mean if I draw a straight line through the axis of each planet it points to that part of the sky? (I don't really believe that because things move, so it seems those coordinates would be specific to this moment in time.) I'm looking for suggestions if anyone knows a good way to define the axes of our solar system in 3D. (I'm using an XYZ coordinate system centered on the center of the sun.) > >One other question, for those who may be inclined - I'm trying to build my model so that the motions are represented. I'm not building the model to scale so its easier to see, which means I'm not using gravity to model the motions. Do you know a good way to model the motions of the planets (and moons in particular) using only velocity vectors (no acceleration vectors)? There is probably a better way to ask the question I'm asking. I just want to model things moving in a realistic way without having to introduce gravity. > >Thanks! >Dion >_______________________________________________ >Utah-Astronomy mailing list >http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy > >Send messages to the list to >Utah-Astronomy(a)mailman.xmission.com > >The Utah-Astronomy mailing list is not affiliated with any astronomy club. > >To unsubscribe go to: >http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy >Then enter your email address in the space provided and click on "Unsubscribe or edit options". >_______________________________________________ >Utah-Astronomy mailing list >http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy > >Send messages to the list to >Utah-Astronomy(a)mailman.xmission.com > >The Utah-Astronomy mailing list is not affiliated with any astronomy club. > >To unsubscribe go to: >http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy >Then enter your email address in the space provided and click on "Unsubscribe or edit options". >_______________________________________________ >Utah-Astronomy mailing list >http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy > >Send messages to the list to >Utah-Astronomy(a)mailman.xmission.com > >The Utah-Astronomy mailing list is not affiliated with any astronomy club. > >To unsubscribe go to: >http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy >Then enter your email address in the space provided and click on "Unsubscribe or edit options".

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Math problem: vectors for planet axial tilt
by Dion Davidson 07 Feb '13

07 Feb '13

I'm working on a visual simulation of the solar system for presentation to a homeschool group. I'm using GlowScript (very cool - a lot like VPython). The theme of the presentation is "Why don't things line up?" and I want to highlight how axial rotations and orbital planes don't really line up in our solar system. I can see from nasa fact pages the angle of axial tilt for each planet, which I assume is the angle between the rotation axis and the orbital plane of the planet (as opposed to the ecliptic). (ex: http://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html) Here's my question: what is the vector that represents these axes in 3D? Right now all my axes point in the same (roughtly celestial north) direction, which is less interesting than real-life, I assume. I see a section titled "North Pole of Rotation" which gives an RA and Dec for each planet. Does that mean if I draw a straight line through the axis of each planet it points to that part of the sky? (I don't really believe that because things move, so it seems those coordinates would be specific to this moment in time.) I'm looking for suggestions if anyone knows a good way to define the axes of our solar system in 3D. (I'm using an XYZ coordinate system centered on the center of the sun.) One other question, for those who may be inclined - I'm trying to build my model so that the motions are represented. I'm not building the model to scale so its easier to see, which means I'm not using gravity to model the motions. Do you know a good way to model the motions of the planets (and moons in particular) using only velocity vectors (no acceleration vectors)? There is probably a better way to ask the question I'm asking. I just want to model things moving in a realistic way without having to introduce gravity. Thanks! Dion

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The Great Atlas has arrived
by jcarman6＠q.com 07 Feb '13

07 Feb '13

Ahhhhhh, memories. When I got my first telescope - a C-8 (orange - the best color) back in 1980, I also purchased Ve hrenberg's Handbook of the Constellations. 1950 Coordinates. Much smaller about 8" by 12", w hite stars on black background. On the right side was the constellation and on the left side was a whole page of objects and their ra/decs to find within the constellation. Good for northern and southern hemisphere. Am sure it is not nearly as detailed as your's Chuck, but it certainly served me well. The binding is held together by duct tape (bless that invention), but the pages are in very good shape. The Tirion is to big and cumbersome. BUT, those old fashioned paper charts are well loved and appreciated at private observing sessions The glow from lap tops, ipads/pods and such are NOT appreciated. Tried it once with my Sky program -gahhh, the glow blew the night vision to smitherins. .

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Speaking of paper sky atlases
by Patrick Wiggins 06 Feb '13

06 Feb '13

With the talk today of paper atlases I figured I'd mention that I'd be happy to part with my pristine, rarely used copies of Sky Catalogue 2000.0 Volumes 1 and 2 and Uranometria 2000.0 Volumes 1 and 2 cheap. I'd rather see them go cheap and be used than continue to sit neglected on the shelf. Any interest?

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The Great Atlas has arrived
by Dale Hooper 06 Feb '13

06 Feb '13

I mentioned this to the OAS, but I forgot to post about this on Utah-Astronomy. I think this is a great deal that might not last much longer. In the Nov/Dec issue of Astronomy Technology Today there is an article about "The Great Atlas of the Sky" (also known as the world's largest printed atlas of the sky). As the article states, "the atlas consists of 296 maps printed on the front and back of 148 pages measuring 17 by 24 inches". Each map covers 15 degrees x 10 degrees, 1.38 inches/degree. It includes 2.4 million stars down to mag. 12. All the reviews I've seen are very positive. It includes a leatherette zip up binder that is 14.5 inches x 19 inches. There is an internal front pocket to hold accessories and a clear plastic sleeve to hold an individual page so you can use it in the field. The atlas weighs in at about 14 pounds. I ordered it from the publisher at www.greatskyatlas.com<http://www.greatskyatlas.com/> for $99 (including shipping) and it took two months to arrive from Poland. It just arrived yesterday and it was well worth the wait. It definitely is a *big* atlas. You can also order it from Agena AstroProducts at http://agenaastro.com/catalogsearch/result/?q=Great+Atlas+of+the+Sky for $139 (including shipping). That is probably the way to get it if you want to have any chance of getting it for the Messier Marathon. I think they are trying to close these out because I believe they used to sell for about $260. Clear skies, Dale.

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$100 off PST
by Chuck Hards 06 Feb '13

06 Feb '13

High Point Scientific is currently running the PST for $100 off, through March 31, if anyone is interested. http://www.highpointscientific.com/product/COR-PST/Coronado-PST-Personal-So… I'm SO glad I got mine at $400 a couple of years ago.

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Kitty da Vinci
by Patrick Wiggins 06 Feb '13

06 Feb '13

Most of these painting are not science related but scroll down to the bottom and you'll see one that it. http://www.slcpl.org/events/view/1852/1 Now if he'd just do one of a cat using a telescope... patrick (who thinks they're all cute)

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St. George Star Party.
by Dunn, David 06 Feb '13

06 Feb '13

It doesn't look like there will be any observing at the St. George Star Party this year. I would say that you can cancel your reservations if you want to. My wife, daughter and I will still be going just to get away for a few days. If you are still going, let me know and we can do dinner or something. Thanks, David Dunn

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ISON this eveing
by Patrick Wiggins 06 Feb '13

06 Feb '13

http://users.wirelessbeehive.com/~paw/temp/C_2012_K5.2013FEB05.JPG I've been asked to provide a bit more information on where the comet is located in the image. Basically it's pretty much dead center, just above the very close pair of double stars, looking a bit fuzzy and sprouting a tiny, faint wisp of a tail to the right. As always, two 30 second exposures taken ten minutes apart. FOV is about 18' x 26'. It pops out using the cross-eye viewing method. BTW, I've been keeping an eye on the position of C/2011 L4 (PANSTARRS) but it's still too far south. Same for 2012 DA14. patrick

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