April 2009 - Utah-Astronomy - mailman.xmission.com

Fractint
by Gary Vardon 19 Apr '09

19 Apr '09

I downloaded the program Fractint from the internet. It is a free program with a lot of stunning fractals. Get it by Googling fractint. Fractals have astronomical importance because nature is fractal. There may be other free programs on the net. Perhaps, SLASers can share information on these programs. Any thoughts? Any programs that you recommend? Sincerely, Gary Vardon The book DO It Right will help you understand vital ideas leading to your geater success. GO to PublishAmerica. -----Original Message----- From: Canopus56 Sent: Sunday, April 19, 2009 7:50 PM To: Utah Astronomy List Serv Subject: [Utah-astronomy] Misc Notes on Stargate Asterism - Sat SPOC The faintest star in the Stargate asterism is a mag 10 high proper motion star with no good identifier: v10.1 2MASS J12354638-1201152ï¿½ PPM 717043 J2000 RA:ï¿½ 12h35m46.38sï¿½ï¿½ DE:-12ï¿½01'15.2" You can zero in on it using the id of the v6.6 star in the outer triangle: HD109584 SAO157385 I'm not seeing anything cross-references in Simbad that says the mag 10 star is a variable star. - Kurt _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy(a)mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com

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Misc Notes on Stargate Asterism - Sat SPOC
by Canopus56 19 Apr '09

19 Apr '09

The faintest star in the Stargate asterism is a mag 10 high proper motion star with no good identifier: v10.1 2MASS J12354638-1201152 PPM 717043 J2000 RA: 12h35m46.38s DE:-12°01'15.2" You can zero in on it using the id of the v6.6 star in the outer triangle: HD109584 SAO157385 I'm not seeing anything cross-references in Simbad that says the mag 10 star is a variable star. - Kurt

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Dobsonian Setting Circles?
by Troy Davidson 19 Apr '09

19 Apr '09

Hello all, I'm looking at adding some setting circles to my Dobsonian. The azimuth circle will be easy to handle on the base. I have found sites that allow you to print out whatever size you need. But the altitude scale seems to be more of a problem. I can use an inclinometer to tell me the angle of my scope. A simple math problem and I would have my Dec. But, this will only work if the scope is directly pointing north or south. When the scope is pointing to an object that isn't directly north or south, then the math gets a bit harder. I have seen digital setting circles, but those seem to start at $500. Is there a better way to handle setting circles, especially the altitude, on a Dobsonian? Thanks. -- ++++++++++++++++++ Troy Davidson

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Re: [Utah-astronomy] Sky Fog Test with Canon Rebel XT
by Jim Gibson 19 Apr '09

19 Apr '09

Thanks Daniel I enjoyed your comments. Good link too. Jim --- On Sun, 4/19/09, daniel turner <outwest112(a)yahoo.com> wrote: From: daniel turner <outwest112(a)yahoo.com> Subject: Re: [Utah-astronomy] Sky Fog Test with Canon Rebel XT To: "Utah Astronomy" <utah-astronomy(a)mailman.xmission.com> Date: Sunday, April 19, 2009, 4:40 PM Jim: Sky fog reading will vary from day to day and even hour to hour. What's happening is the ground lighting is reflected of of particles in the air. Last night's cirrus clouds out at SPOC are a good example. I rated the night as poor to fair because of the weather conditions. To get an idea about what conditions will be like before I go out, I look at the weather sounding map. http://weather.uwyo.edu/upperair/sounding.html First I look at the "Precipitable water [mm] for entire sounding" and when it's less than a half an inch the night will be good. If it's a half to a full inch, I may as well stay home. This will effect even the best of dark sites as well as suburban viewing. Next I look at the sounding data looking for layers of the atmosphere where the relative humidity is above 50%. These layers will map the cirrus clouding like those that occured last night. You would think that 50% would be alright but I think what is happening is that dust and pollen are hygroscopic and are starting the formation of water droplets even at just 50% humidity. April is bad because there is a lot of water on the ground that needs to be dried out and carried away by the atmosphere before we get good transparency. September is the best time of year for the same reason. Clear Skies DT --- On Sun, 4/19/09, Jim Gibson <jimgibson00(a)yahoo.com> wrote: > From: Jim Gibson <jimgibson00(a)yahoo.com> > Subject: [Utah-astronomy] Sky Fog Test with Canon Rebel XT > To: "Utah Astronomy" <utah-astronomy(a)mailman.xmission.com> > Date: Sunday, April 19, 2009, 8:18 AM > > I found this article on measuring sky fog with a camera > quite interesting: http://www.pbase.com/samirkharusi/image/37608572. The > idea is to tell photographers a couple of things. One is to > give photographers an idea how their backyard skies compare > to a more preferred location. Of course they would have to > conduct the same test at the preferred location, and the > other thing it would tell them is how long they can take an > exposure before running into sky fog problems. As Samir > says, as long as the histogram is not attached to the left > side and it is also half way or less then you are sky fog > limited. > > I decided to give it a try for just those reasons. I was > not really sure I could judge the visual magnitude of the > sky in my back yard in Orem very well. I see many of you > can figure the visual magnitude without much trouble, so I > thought I better do something to learn how. In the past I > would look for Polaris and see how many stars I could see in > the little dipper. Usually, all I could see was Polaris, but > those skies are in or near the Salt Lake glow for me. > Anyway, I would figure my skies to be between vMag 2.0 and > 3.0 with average clear sky conditions. > > In following Samir Kharusi directions, only using a tripod, > I pointed my Canon Rebel XT with a Sigma 2.8 24mm-70mm lens > (set at 24mm) straight up and it didn’t take long to get > the disappointing news. I was reeeally hoping to get at > least 180 seconds or better of exposure time, but no dice. > http://www.slas.us/gallery2/main.php?g2_itemId=1790 . > In this image you will see that my histogram is slightly > past half way after 90 seconds. According to Samir’s > chart: > (This is probably not going to come out lined up.) > > Sec----------------1680---1062---660---420---264--168---108---66----42----27-----16.8 > Mins-----------------28---17.7----11----7.0----4.4---2.8----1.8---1.1----0.7---0.45---0.28 > > Mag/sq > arc-sec-------22---21.5----21----20.5---20----19.5---19----18.5---18----17.5---17 > > VLMag---------------8+?---7+?----7+?----6.6----6.1---5.6----5.1---4.6----4.1---3.6----3.1 > > that would put my visual magnitude between 4.6 and 5.1. > Uh…I don’t think so. I went back and re-read Samir’s > article and found this: > VISUAL LIMITING MAGNITUDES: For > convenience we may talk of Visual Limiting Magnitudes. Note, > for convenience only. The VLimMag translation scale shown > above is not absolute. It is observer dependent and very > subjective< > But none the less, The process is a non-subjective record > that I can repeat over time and in various locations and > hopefully I can learn something from it. Maybe by empirical > data I can match it to a visual scale for comparison use > only. (Any comments or insights would be helpful) > > In case you were wondering how I got the histogram image I > used Canon’s Digital Photo Professional. Samir says to use > the back-of-camera histogram; Digital Photo Professional’s > histogram looks just the same. However, it does look a > little different in PhotoShop. > > You may have noticed that the f/stop is set at 5.6 instead > of f/4. I had set the internal f/stop to 4 as suggested by > Samir, but when I switched to bulb then I got the f/5.6. I > am going to try and get out to the pit-n-pole in the next > few days and see what I get out there running exactly the > same test. > > I think I will also try this with the camera attached to > them 100mm ED and see what the difference is. Once I decide > on a procedure then I will have to stick with it for > comparison reasons. > > Results may vary, so each photographer will have to figure > their own sky fog limit. > > I have left out a lot of good stuff, like the minimum > exposure time and comments about signal to noise ratio so > be sure to read the article. My minimum exposure was about > 10 seconds when the sky fog histogram mountain separated > from the left side of the histogram frame :>(. That is > way too short for any kind of good detail. Therefore, I feel > that my sky fog limit is a very narrow band from my backyard > location. > > Any comments or suggestions are welcome. > > > Jim > > > > > _______________________________________________ > Utah-Astronomy mailing list > Utah-Astronomy(a)mailman.xmission.com > http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy > Visit the Photo Gallery: http://www.slas.us/gallery2/main.php > Visit the Wiki: http://www.utahastronomy.com > _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy(a)mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com

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Re: [Utah-astronomy] Sky Fog Test with Canon Rebel XT
by daniel turner 19 Apr '09

19 Apr '09

Jim: Sky fog reading will vary from day to day and even hour to hour. What's happening is the ground lighting is reflected of of particles in the air. Last night's cirrus clouds out at SPOC are a good example. I rated the night as poor to fair because of the weather conditions. To get an idea about what conditions will be like before I go out, I look at the weather sounding map. http://weather.uwyo.edu/upperair/sounding.html First I look at the "Precipitable water [mm] for entire sounding" and when it's less than a half an inch the night will be good. If it's a half to a full inch, I may as well stay home. This will effect even the best of dark sites as well as suburban viewing. Next I look at the sounding data looking for layers of the atmosphere where the relative humidity is above 50%. These layers will map the cirrus clouding like those that occured last night. You would think that 50% would be alright but I think what is happening is that dust and pollen are hygroscopic and are starting the formation of water droplets even at just 50% humidity. April is bad because there is a lot of water on the ground that needs to be dried out and carried away by the atmosphere before we get good transparency. September is the best time of year for the same reason. Clear Skies DT --- On Sun, 4/19/09, Jim Gibson <jimgibson00(a)yahoo.com> wrote: > From: Jim Gibson <jimgibson00(a)yahoo.com> > Subject: [Utah-astronomy] Sky Fog Test with Canon Rebel XT > To: "Utah Astronomy" <utah-astronomy(a)mailman.xmission.com> > Date: Sunday, April 19, 2009, 8:18 AM > > I found this article on measuring sky fog with a camera > quite interesting: http://www.pbase.com/samirkharusi/image/37608572. The > idea is to tell photographers a couple of things. One is to > give photographers an idea how their backyard skies compare > to a more preferred location. Of course they would have to > conduct the same test at the preferred location, and the > other thing it would tell them is how long they can take an > exposure before running into sky fog problems. As Samir > says, as long as the histogram is not attached to the left > side and it is also half way or less then you are sky fog > limited. > > I decided to give it a try for just those reasons. I was > not really sure I could judge the visual magnitude of the > sky in my back yard in Orem very well. I see many of you > can figure the visual magnitude without much trouble, so I > thought I better do something to learn how. In the past I > would look for Polaris and see how many stars I could see in > the little dipper. Usually, all I could see was Polaris, but > those skies are in or near the Salt Lake glow for me. > Anyway, I would figure my skies to be between vMag 2.0 and > 3.0 with average clear sky conditions. > > In following Samir Kharusi directions, only using a tripod, > I pointed my Canon Rebel XT with a Sigma 2.8 24mm-70mm lens > (set at 24mm) straight up and it didn’t take long to get > the disappointing news. I was reeeally hoping to get at > least 180 seconds or better of exposure time, but no dice. > http://www.slas.us/gallery2/main.php?g2_itemId=1790 . > In this image you will see that my histogram is slightly > past half way after 90 seconds. According to Samir’s > chart: > (This is probably not going to come out lined up.) > > Sec----------------1680---1062---660---420---264--168---108---66----42----27-----16.8 > Mins-----------------28---17.7----11----7.0----4.4---2.8----1.8---1.1----0.7---0.45---0.28 > > Mag/sq > arc-sec-------22---21.5----21----20.5---20----19.5---19----18.5---18----17.5---17 > > VLMag---------------8+?---7+?----7+?----6.6----6.1---5.6----5.1---4.6----4.1---3.6----3.1 > > that would put my visual magnitude between 4.6 and 5.1. > Uh…I don’t think so. I went back and re-read Samir’s > article and found this: > VISUAL LIMITING MAGNITUDES: For > convenience we may talk of Visual Limiting Magnitudes. Note, > for convenience only. The VLimMag translation scale shown > above is not absolute. It is observer dependent and very > subjective< > But none the less, The process is a non-subjective record > that I can repeat over time and in various locations and > hopefully I can learn something from it. Maybe by empirical > data I can match it to a visual scale for comparison use > only. (Any comments or insights would be helpful) > > In case you were wondering how I got the histogram image I > used Canon’s Digital Photo Professional. Samir says to use > the back-of-camera histogram; Digital Photo Professional’s > histogram looks just the same. However, it does look a > little different in PhotoShop. > > You may have noticed that the f/stop is set at 5.6 instead > of f/4. I had set the internal f/stop to 4 as suggested by > Samir, but when I switched to bulb then I got the f/5.6. I > am going to try and get out to the pit-n-pole in the next > few days and see what I get out there running exactly the > same test. > > I think I will also try this with the camera attached to > them 100mm ED and see what the difference is. Once I decide > on a procedure then I will have to stick with it for > comparison reasons. > > Results may vary, so each photographer will have to figure > their own sky fog limit. > > I have left out a lot of good stuff, like the minimum > exposure time and comments about signal to noise ratio so > be sure to read the article. My minimum exposure was about > 10 seconds when the sky fog histogram mountain separated > from the left side of the histogram frame :>(. That is > way too short for any kind of good detail. Therefore, I feel > that my sky fog limit is a very narrow band from my backyard > location. > > Any comments or suggestions are welcome. > > > Jim > > > > > _______________________________________________ > Utah-Astronomy mailing list > Utah-Astronomy(a)mailman.xmission.com > http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy > Visit the Photo Gallery: http://www.slas.us/gallery2/main.php > Visit the Wiki: http://www.utahastronomy.com >

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Sky Fog Test with Canon Rebel XT
by Jim Gibson 19 Apr '09

19 Apr '09

I found this article on measuring sky fog with a camera quite interesting: http://www.pbase.com/samirkharusi/image/37608572. The idea is to tell photographers a couple of things. One is to give photographers an idea how their backyard skies compare to a more preferred location. Of course they would have to conduct the same test at the preferred location, and the other thing it would tell them is how long they can take an exposure before running into sky fog problems. As Samir says, as long as the histogram is not attached to the left side and it is also half way or less then you are sky fog limited. I decided to give it a try for just those reasons. I was not really sure I could judge the visual magnitude of the sky in my back yard in Orem very well. I see many of you can figure the visual magnitude without much trouble, so I thought I better do something to learn how. In the past I would look for Polaris and see how many stars I could see in the little dipper. Usually, all I could see was Polaris, but those skies are in or near the Salt Lake glow for me. Anyway, I would figure my skies to be between vMag 2.0 and 3.0 with average clear sky conditions. In following Samir Kharusi directions, only using a tripod, I pointed my Canon Rebel XT with a Sigma 2.8 24mm-70mm lens (set at 24mm) straight up and it didn’t take long to get the disappointing news. I was reeeally hoping to get at least 180 seconds or better of exposure time, but no dice. http://www.slas.us/gallery2/main.php?g2_itemId=1790 . In this image you will see that my histogram is slightly past half way after 90 seconds. According to Samir’s chart: (This is probably not going to come out lined up.) Sec----------------1680---1062---660---420---264--168---108---66----42----27-----16.8 Mins-----------------28---17.7----11----7.0----4.4---2.8----1.8---1.1----0.7---0.45---0.28 Mag/sq arc-sec-------22---21.5----21----20.5---20----19.5---19----18.5---18----17.5---17 VLMag---------------8+?---7+?----7+?----6.6----6.1---5.6----5.1---4.6----4.1---3.6----3.1 that would put my visual magnitude between 4.6 and 5.1. Uh…I don’t think so. I went back and re-read Samir’s article and found this: > VISUAL LIMITING MAGNITUDES: For convenience we may talk of Visual Limiting Magnitudes. Note, for convenience only. The VLimMag translation scale shown above is not absolute. It is observer dependent and very subjective< But none the less, The process is a non-subjective record that I can repeat over time and in various locations and hopefully I can learn something from it. Maybe by empirical data I can match it to a visual scale for comparison use only. (Any comments or insights would be helpful) In case you were wondering how I got the histogram image I used Canon’s Digital Photo Professional. Samir says to use the back-of-camera histogram; Digital Photo Professional’s histogram looks just the same. However, it does look a little different in PhotoShop. You may have noticed that the f/stop is set at 5.6 instead of f/4. I had set the internal f/stop to 4 as suggested by Samir, but when I switched to bulb then I got the f/5.6. I am going to try and get out to the pit-n-pole in the next few days and see what I get out there running exactly the same test. I think I will also try this with the camera attached to them 100mm ED and see what the difference is. Once I decide on a procedure then I will have to stick with it for comparison reasons. Results may vary, so each photographer will have to figure their own sky fog limit. I have left out a lot of good stuff, like the minimum exposure time and comments about signal to noise ratio so be sure to read the article. My minimum exposure was about 10 seconds when the sky fog histogram mountain separated from the left side of the histogram frame :>(. That is way too short for any kind of good detail. Therefore, I feel that my sky fog limit is a very narrow band from my backyard location. Any comments or suggestions are welcome. Jim

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no sunspots
by Gary Vardon 18 Apr '09

18 Apr '09

I used my Sunspotter today and saw no spots. I have not seen any sun spots since 7/31/08. Sincerely, Gary Vardon The book DO It Right will help you understand vital ideas leading to your geater success. GO to PublishAmerica. -----Original Message----- From: Joe Bauman Sent: Friday, April 17, 2009 10:53 AM To: Utah Astronomy Subject: Re: [Utah-astronomy] Joe's UFO Hi Steve, We can figure the direction by looking at the star I indicated as it was at about 3 a.m. Here's what I wrote in my journal about the lens: " The telephoto I borrowed from the paper was far too heavy for the telescope and I couldn't use it. Instead I used a small tele I have, which has f-stop openings to f/2." I still have the telephoto. It's a Nikon lens. Around the front it says, "Nikkor 28 mm 1:2 339925." I'm sure it was focused at infinity. -- hope that helps. Thanks for your interest! -- Joe --- On Fri, 4/17/09, Stephen Peterson <summitek(a)mindspring.com> wrote: From: Stephen Peterson <summitek(a)mindspring.com> Subject: [Utah-astronomy] Joe's UFO To: utah-astronomy(a)mailman.xmission.com Date: Friday, April 17, 2009, 8:14 AM Joe, Image might be fun to analyze by doing some calculations. Do you recall lens focal length and aperture? You were probably focused at infinity. Aperture used for image (full open or 1 stop down)? I presume the "overall view" is a more or less full frame print from 35 mm format, any cropping when you did the digital copy? You say the camera was probably pointing SSE toward Moab. Any other info would be helpful. Steve _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy(a)mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy(a)mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://www.slas.us/gallery2/main.php Visit the Wiki: http://www.utahastronomy.com

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USNO database
by Jim Gibson 18 Apr '09

18 Apr '09

Patrick, Just a heads up on tonight at SPOC (Sat). I hope you will be there because I will bringing an external hard drive if you wouldn’t mind having the USNO database put on it. I will leave it with you and pick it up maybe at the SLAS meeting or when ever it’s ready. Thanks Jim

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Wheeler Farm Star Party, Friday 17 Apr
by Robert Taylor 18 Apr '09

18 Apr '09

Lured to Wheeler by the sudden appearance of a blue sky I trekked over to Wheeler Farm to find a small contingent of SLASers already there. A local High School class with teachers and home made telescopes in tow also showed up with the hope they would get try their new creations on the night sky. The blue sky didn't last long and by near dark we were surrounded by expanding clouds, after a short tease the last large sucker hole filled in. We had a small number of other people the came over hoping to see something but most were disappointed and went away with yellow schedules in hands and a promise that Saturday would be better and directions to SPOC. Most of us stayed around for while hoping to get a chance to se a few things before packing it in. Unfortunately it was not meant to be. Or was it? After the bulk of the SLASers went of for waffles and coffee the sky started to break and low and behold the Big Dipper and Saturn were clearly visible soon other stars and constellation began to pop out and the clouds were in full retreat. A handful of us: Craig and Ann Blanchard, Jim Gibson, Dan Turner and myself were all that was left, with only one 80mm refractor left assembled. The Clearing was enough to bring some people out and before we long we had a handful of visitors meandering around wanting to see something. All were delighted by the views of Saturn in the small refractor and a double star and after a lot of chatting and talking up the club and SPOC left with yellow schedules and directions to SPOC and promises of bigger and better viewing, nicer weather and more telescopes. Overall the wheeler site is pretty good for the middle of the valley, last night there was considerable moisture in the air, transparency was poor as a result but he it was steady and Saturn looked good. Once the trees around the site fill in the site should improve, there are no real bright lights shinning into the site but there are numerous businesses and dwellings in the area each with there poorly designed lighting. Full trees will help to cut this down and provide a darker site. No guards or steady winds to worry about, the grass fields made a good place to set up and parking was plentiful. As cars came in their head lights would light up the area, that will be a little bit of a problem but otherwise I think this will be a good site for in-valley star parties. Robert Taylor

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Re: [Utah-astronomy] member loaner scope vs school subsidy
by Jim Gibson 18 Apr '09

18 Apr '09

Roger, Your wrote: > I use a model of our solar system with the sun being a basketball and then I download a google satelite image of the neighborhood where the school is located and superimpose where the planets would be on the map.< That has to be an excellent teaching aid. Kids have a good mental image of their local geography and your demonstration has to take the abstractness out of trying to fathom the solar system. Good job. Jim

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