October 2007 - Utah-Astronomy - mailman.xmission.com

Comet 17P - Finding in washed out skies
by Kurt Fisher 26 Oct '07

26 Oct '07

Finding Comet 17P in urban light-polluted or full Moon washed out skies is easy. Algol, Mirfak and Comet 17P form a hockey stick asterism. Algol and Mirfak are the handle of the hockey stick. Mirfak and Comet 17P form the striking face or "head" of the hockey stick asterism. Details and finder chart at Utah Astro current events wiki http://www.utahastronomy.com/Current_observing_events#Oct_24_to_Nov_2_Comet… - Kurt _______________________________________________ Sent via CSolutions - http://www.csolutions.net

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Meade moving?
by Patrick Wiggins 26 Oct '07

26 Oct '07

I just saw a message on the OAS list the poster said was forwarded from Meade. It said Meade is relocating their manufacturing operations from Irvine, California to "a lower-cost location." Did not say where the new place is. Guesses? pw

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Comet 17P Holmes picture
by Kurt Fisher 25 Oct '07

25 Oct '07

To correct based on Dan's post on 17P orbit elements. I misstated the period as 24 years, having misread the screen the Dan used. The period is 6.88 years. - Kurt _______________________________________________ Sent via CSolutions - http://www.csolutions.net

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Major change in AAVSO charts and calibration stars
by Kurt Fisher 25 Oct '07

25 Oct '07

Reposted from the AAVSO mailing list - Kurt ========================== Date: Wed, 24 Oct 2007 18:17:10 -0400 From: arne <arne(a)aavso.org> Subject: [Aavso-photometry] Chart and comparison-star database changes - Important To: AAVSO-DIS <aavso-discussion(a)mira.aavso.org> Cc: Aavso-Photometry <aavso-photometry(a)mira.aavso.org> Message-ID: <471FC466.6040409(a)aavso.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed As of Wednesday, October 24, 2007, we have updated about 2/3 of the stars in the Variable Star Database (VSD or the comparison-star database) of the Variable Star Plotter (VSP). These stars now have accurate V-band photometry, and in most cases, multiband photometry. This is Phase IIa of the comparison star database project. Phase I was the documentation of every comparison star found on every chart at the AAVSO, as of about 2004. This resulted in a database of around 31,700 stars, where the position and chart-magnitude of each star was recorded. It was a massive effort, lead by Vance Petriew, but involving dozens of volunteers. However, no precision photometry was recorded, even if these were CCD-f charts with a table of BVRI photometry included, or where Sumner sequences could be found using the online chart search engine. These sequences are now included in VSD/VSP. If you pull up a chart for a field like TT Ari, you can now obtain the BVRI information for the majority of the comparison stars. This Phase IIa update was a massive effort in itself, and would not have been possible without the assistance of Grzegorz Pojmanski for ASAS, Jean-Claude Mermilliod for GCPD, Michael Koppelman, and Aaron Price. We've also used the hard work and labor of many surveys, such as Tycho, TASS, SDSS, 2MASS, and Brian Skiff's LONEOS photometric calibration database. For those of you who have never looked for the photometry available for the chart sequence stars, there are two methods through VSP. First, near the bottom of the form is the option "CCD Box Limit". This is the number of sequence stars for which you want photometry displayed on the chart itself. Set that number to a value greater than zero, and you will find a box printed in the lower right of your chart. Second, you can also click the box at the form bottom labelled "Field Photometry" and "Do not plot a chart, just give me a table of photometry." This gives you an html table of the photometry, along with coordinates for every star. Why have only 2/3 of the stars been updated? The main reason is that the remainder are significantly discrepant from their chart labels. A star labelled as 108, for example, might have accurate photometry that indicates a label of 104 is more appropriate. We want to check these stars thoroughly and ensure that the photometry and labels are correct, and that will take a couple of months. In the meantime, we wanted to give you the benefit of the majority of stars where the differences are minor (less than 0.2mag). What is encouraging to me is that 21,826 of our comparison stars *were* accurate, meaning our observers were providing nearly correct estimates. However, it *does* mean that many charts are slightly different than the online version, or even the chart you created with VSP a week ago. For visual observers, you will be hard-pressed to measure the difference. However, for all observers, we request that you be extremely careful in your reports. It is *essential* that you indicate the chart_ID/date that you use. For now, you can continue to use your existing charts, but we urge downloading new versions over the next few months and using these new, more precise, labels and magnitudes. Our intent is to make the AAVSO charts as accurate as possible. There are several charts where the sequences are well-known to be highly wrong; othere with scale errors; still others where accurate photometry would help the CCD observers. We have long debated whether we should continue using charts that we know are wrong, as maintaining the "wrongness" at least means consistent light curves. At the same time, we know that those fields with bad charts are underobserved because people know they can't estimate properly. We are taking the baby step now of minor tweaks to existing sequences. I hope it does not inconvenience too many observers - I know it will take time to get used to even small changes to your favorite fields. Please bear with us, and realize that the end product will be better science for the astronomical community. _______________________________________________ Sent via CSolutions - http://www.csolutions.net

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17p Holmes orbital elements
by daniel turner 25 Oct '07

25 Oct '07

a: semi major axis is 3.6 AU q: solar distance at perihelion 2.05 AU Q: solar distance at aphelion 5.18 AU p: orbital period 6.88 years t: last perihelion date 2007-may-4 so it's on it's way back out. i: orbital inclination 19.1 degrees http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=17p&orb=1 __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

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Re: [Utah-astronomy] Comet 17P Holmes picture
by Kurt Fisher 25 Oct '07

25 Oct '07

Running the comet's apparent size of 2 or 3 arcminutes at a distance of 2.44 astronomical units through the half-angle formula, I get a cloud diameter between 70,000 and 110,000 kilometers. - Kurt _______________________________________________ Sent via CSolutions - http://www.csolutions.net

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Re: [Utah-astronomy] Comet 17P Holmes picture
by Kurt Fisher 25 Oct '07

25 Oct '07

Scott Catron wrote: > You're right Joe, look - where's the tail?! IT'S COMING STRAIGHT AT US!! For lurkers, the lack of an apparent tail is probably related to its distance from the Sun (near Mars's orbit) and its orbital geometry relative to the Sun and the Earth. http://gallery.utahastronomy.com/v/kurt/solarsystem/Comet+17P+Holmes/comet1… This comet orbits entirely within the orbit of Jupiter and has about a 24 year period. Right now it is near opposition with respect to Earth but is above the plane of the solar system. But the comet is not exactly spherical. Quantized processing of an image shows it to be slightly elliptical. http://gallery.utahastronomy.com/v/kurt/solarsystem/Comet+17P+Holmes/009.jp… This could be a spheriod shell that is slightly oval from its orbital motion and the direction of the Sun. Or you could be looking down the "tube" of the comet with the obscured tail behind it. >From an album with my image last night and collected explanatory materials - http://gallery.utahastronomy.com/v/kurt/solarsystem/Comet+17P+Holmes/ - Kurt _______________________________________________ Sent via CSolutions - http://www.csolutions.net

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Comet 17P Holmes picture
by Kurt Fisher 25 Oct '07

25 Oct '07

David Dunn wrote, > Nice picture. I am just curious, what it the black spot in the > middle of the comet? I really enjoy the pictures that you and > others on this list share with us. Thanks. Dave It's part of my imaging learning curve. That is what a Meade DSI Pro 1 and Meade Envisage capture software does when it overexposures a pixel. The software reassigns the pixel to a value of -32757. I have created a Utah Astro Gallery how to album on this error. There is probably a way to fix this using pixel math operations in AIP4WIN or Autostar, but for now I just did the correction using a paint program. http://gallery.utahastronomy.com/v/kurt/Meade+DSI+Studies/Overexposure+erro… After the correction - here's the final money shot - http://gallery.utahastronomy.com/v/kurt/solarsystem/Comet+17P+Holmes/005.jp… I have created an album for this comet collecting the image from last night and other explanatory materials on its orbit - http://gallery.utahastronomy.com/v/kurt/solarsystem/Comet+17P+Holmes/ - Kurt _______________________________________________ Sent via CSolutions - http://www.csolutions.net

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Comet 17P Holmes picture
by Patrick Wiggins 25 Oct '07

25 Oct '07

I just got this 5" exposure with the C-14 @ f/11. Field is 9' x 13'. http://users.wirelessbeehive.com/~paw/temp/COMET17PHOLMES01.JPG patrick

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Comet 17P Holmes picture
by Kurt Fisher 25 Oct '07

25 Oct '07

Here's my picture of Comet 17P Holmes taken a few hours ago - http://gallery.utahastronomy.com/v/kurt/solarsystem/20071023_17P.PNG.html Image details are on the gallery page. - Kurt _______________________________________________ Sent via CSolutions - http://www.csolutions.net

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