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

Re: [Utah-astronomy] Treeless Mars
by stormcrow60＠xmission.com 31 Mar '09

31 Mar '09

Hi Joe, Thanks for the heads up. I thought I followed the Mars surface probes fairly consistently. But apparently I have not been as diligent with the orbital probes that are taking these amazing pictures. I had no idea these photos existed. Science is truly stranger then fiction! Thanks for sharing. Jon

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Re: [Utah-astronomy] Double star HIP not the same
by Jim Gibson 31 Mar '09

31 Mar '09

Kurt, I didn’t have a lot of time last night but I went out with the 100mm ED and took a look a several of the doubles in Monoceros. I discovered I couldn’t see color as well as you. Every thing looked white, pale white, orange or red. I did find Mon 11 and it was a delight. The one little tiny star was real close in (sep 2.8”), but I could split it with the 100mm ok. I found 3 Mon, SAO151037, but I couldn’t split it at 2.0” . Beta Mon was an easy find and a nice double. I checked out a few others in the Monoceros area and all in all it was a fun time. Up at the top of Monoceros I had a Struve 921 that I couldn’t find. I think it is the same as HIP 31119. It was kind of dark around there and I had to hop in from Alzirr in Gemini. While I was up that way I just took a look at m35. The seeing was rather clear. The star field in M35 looked great. Saturn was clear as a bell too. Anyway, for the time I had it was fun. Now that the moon is going to be a factor, I will have time to check out a few more. Jim

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Bryce Canyon schedule set
by Patrick Wiggins 31 Mar '09

31 Mar '09

Bryce Canyon has set their 2009 astronomy program calendar: http://www.nps.gov/brca/planyourvisit/astronomyprograms.htm patrick

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Bill Kelley
by Patrick Wiggins 31 Mar '09

31 Mar '09

I'm going to put something in News about this but thought the former SLASers who hang out here might like to see it too. +++++ Bill Kelley Takes a Spill Many long time SLAS members will remember Bill Kelley. His wife Lois emailed to say that Bill who is now 91 recently fell down and "bruised his ribs, cut his arm and twisted an already very bad back." Those wishing to send Bill get well wishes can email him at flex(a)commspeed.net . +++++ patrick

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Re: [Utah-astronomy] Utah-astronomy] Surface Brightness
by Canopus56 30 Mar '09

30 Mar '09

Jim asked: > I Need help from some of you math wiz-bangs. I looked up on a chart of surface brightness that > M1 has a surface brightness of 35 * 10 to the minus 6; or .000035. The answer is 20.6 mpsas. The following url links to my javascript calculator that includes an option "Convert extended object size (arcmins) and apparent brightness (V) to MPSAS". The back matter to the computation is in the bibliography: Formula: objB_mpas = objMagnitude + (2.5 * (Log10((PI() / 4) * objMajorAxis_arcsec * objMinorAxis_arcsec))) Sources: Clark, R.N., 1990. Appendix E in Visual Astronomy of the Deep Sky, Cambridge University Press and Sky Publishing.http://www.clarkvision.com/visastro/appendix-e.html Covington, M. (1998, 2d). Appendix A, Astrophotography for Amateurs. pp. 259-261 http://www.covingtoninnovations.com/ Clark's Appendix E contains pre-computed surface brightnesses in mpsas for about 620 commonly observed DSOs. Also note the related contrast index method for determining the contrast index between a given object and the current sky brightness. In general, I find the mpsas method of computing an object's surface brightness to be a good predictor for compact PNs and galaxies. It is a poor predictor for dispersed open clusters like M41. The difference between the predicted result and your first try is in the conversion of an elliptical object into magnitudes per square arcsec. That's the PI() / 4) * objMajorAxis_arcsec * objMinorAxis_arcsec part of the above equation. Note the obejct dimensions used in the formula are in arcsecs while the size of most DSO is given in arc minutes. Other variations between surface brightness estimates by Berry in the Handbook and Clark's Appendix E can be attributed to their differing estimates of the size of an object. Clear Skies - Kurt P.S. - Here's my vba code. The javascript code for the same can be found in the web page calculator above. Public Function PhotogObjectArea2MPAS(ByVal objMagnitude_tmp, ByVal objType_tmp As String, ByVal objMajorAxis_arcmin_tmp, ByVal objMinorAxis_arcmin_tmp, ByVal B_mpas_tmp As Double) As String ' Accepts Magnitude and dimensions and background B_mpas. ' Returns object brightness in MPAS and contrast index. ' Valid object types are " Extended | Stellar | Stellar-CI " ' Where object type is stellar, objMajorAxis_arcmin_tmp and objMinorAxis_arcmin_tmp are ignored. ' Source: Covington, M. Astrophotography for Amateurs, Appendix A ' Clark's Visual Astronomy of the Night Sky, Appendix E ' http://clarkvision.com/visastro/appendix-e.html ' Departs from Covington extended object model for stellar sources. ' For a stellar source, the V-mag is the MPSAS without adjustment for area. ' Tests and usage ' Test against objects in Clark's Appendix E catalogue ' Clark assumes dark sky background of 24.25 MPAS ' NGC7814 ' ? PhotogObjectArea2MPAS(12, 1, 5, 24.25) ' 22.3759059661737 0.749637613530523 ' Checks against Clark's results ' NGC40 ' ? PhotogObjectArea2MPAS(10.5, 1, 0.7, 24.25) ' 18.7412260553693 2.20350957785228 ' Checks against Clark's results ' NGC45 ' ? PhotogObjectArea2MPAS(7.8, 25, 40, 24.25) ' 23.9284809553336 0.128607617866541 ' Checks against Clark's results ' Define variables Dim objMagnitude, objMajorAxis_arcmin, objMinorAxis_arcmin, B_mpas As Double Dim objMajorAxis_arcsec, objMinorAxis_arcsec Dim objB_mpas, ContrastIndex As Double Dim strOut As String Dim objType As String ' Object type - Extended or Stellar Dim ContrastIndexStrOut ' Temporary working variable for output Dim strSpacer ' Temporary working variable for output ' Get input objMagnitude = objMagnitude_tmp objType = Trim(objType_tmp) objMajorAxis_arcmin = objMajorAxis_arcmin_tmp objMinorAxis_arcmin = objMinorAxis_arcmin_tmp B_mpas = B_mpas_tmp ' Convert object dimensions to arcsecs objMajorAxis_arcsec = 60# * objMajorAxis_arcmin objMinorAxis_arcsec = 60# * objMinorAxis_arcmin ' A) Convert objective size and v-mag to B_mpsas ' Departs from Covington extended object model for stellar sources. ' For a stellar source, the V-mag is the MPSAS without adjustment for area. Select Case objType Case "Extended" ' Compute results objB_mpas = objMagnitude + (2.5 * (Log10((PI() / 4) * objMajorAxis_arcsec * objMinorAxis_arcsec))) ' Contrast index formula is from http://clarkvision.com/visastro/appendix-e.html ContrastIndex = -0.4 * (objB_mpas - B_mpas) ContrastIndexStrOut = CStr(ContrastIndex) strSpacer = " " Case "Stellar" objB_mpas = objMagnitude ContrastIndex = -0.4 * (objB_mpas - B_mpas) ContrastIndexStrOut = CStr(ContrastIndex) strSpacer = " " Case "Stellar-CI" objB_mpas = objMagnitude ContrastIndex = -0.4 * (objB_mpas - B_mpas) ContrastIndexStrOut = CStr(ContrastIndex) strSpacer = " " Case "Not applicable" ' Should not be submitted to function, gracefully return zero objB_mpas = "" ContrastIndexStrOut = "" strSpacer = "" Case "Incomplete" ' Should not be submitted to function, gracefully return zero objB_mpas = "" ContrastIndexStrOut = "" strSpacer = "" Case Else ' Handle general error with graceful return of zero objB_mpas = "" ContrastIndexStrOut = "" strSpacer = "" End Select PhotogObjectArea2MPAS = Trim(CStr(objB_mpas)) & strSpacer & Trim(ContrastIndexStrOut) End Function

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Re: [Utah-astronomy] Double star HIP not the same
by Canopus56 30 Mar '09

30 Mar '09

Jim wrote: > Kurt, In looking through your double star list I found SAO95659 11 Mon to have a HIP number as > HIP 30867 instead of HIP 30564. Someone is lying to us. Anyway I see it looks like a nice triplet. Jim Thanks for catching the error. Here's the corrected entry. ================== Corrected Entry ID SAO133316 Constellation Mon Name - HD45725, HIP30867 AltNames bet Mon; 11 Mon; HIP30867; HIP30867; Herschel's Wonder Star CommentsSec 4.7v,5.2v,7.3sep,132pa,2000,Mullaney:blue-blue-blue,0.148kpc,B2 RA 062849 Dec -070158 CommentsMisc - Observation note At 40x appears as single star. At 100x, appears as an easy, split, two nearly equal white stars with a tiny, but distinct gap. A nice warmup for a start of this run with no color contrast. =================== Deleted Bad Entry ID SAO95659 Constellation Mon Name - HD45725, HIP30564 AltNames bet Mon; 11 Mon; Herschel's Wonder Star CommentsSec 4.7v,5.2v,7.3sep,132pa,2000,Mullaney:blue-blue-blue,0.148kpc,B2 RA 062849 Dec -070158 CommentsMisc - Observation note At 40x appears as single star. At 100x, appears as an easy, split, two nearly equal white stars with a tiny, but distinct gap. A nice warmup for a start of this run with no color contrast. ===================

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Re: [Utah-astronomy] M45 and the moon
by JayLEads 30 Mar '09

30 Mar '09

Jim, Was just out in the backyard with the binoculars as I didn't want to set up since I have to be in downtown by 7a.m. but the waxing crescent is heading for M45 right now! Hope you can capture it! Jay

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Double star HIP not the same
by Jim Gibson 30 Mar '09

30 Mar '09

Kurt, In looking through your double star list I found SAO95659 11 Mon to have a HIP number as HIP 30867 instead of HIP 30564. Someone is lying to us. Anyway I see it looks like a nice triplet. Jim

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Saturn shadow transit
by Dunn, David 30 Mar '09

30 Mar '09

Was anyone able to see or get pictures of the shadow transit last Saturday morning? Dale Hooper and I looked for it for several hours. The seeing wouldn't permit very high power so it was really difficult to tell what we were seeing. We did have a lot of good observing time for the Messier objects. The clouds went away and sundown and we had only occasional clouds until about 3am. When it didn't clear back off, we packed up and went home. That campground is really good for being only an hour or so away. The nearest street or farm lights appear to be a mile or more away. They really didn't bother us. All in all it was a nice night of observing. Dave

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Re: [Utah-astronomy] Surface Brightness
by Jim Gibson 30 Mar '09

30 Mar '09

Daniel, Thanks for taking a look at it for me. I got the 35 * 10 to the minus 6 value from a chart in “Then Handbook of Astronomical Image Processing” by Berry & Burnell. It was listed under Diffused Nebulae on pg 80. I trust those guys to know what they are talking about. The formula (S = m + 2.5 * log10A) from wikipedia is for the apparent magnitude of an astronomical object where they say Surface brightness’s are usually quoted in magnitudes per square arc seconds. I am probably mixing terms somewhere. I will look around some more. Thanks again Jim --- On Mon, 3/30/09, daniel turner <outwest112(a)yahoo.com> wrote: From: daniel turner <outwest112(a)yahoo.com> Subject: Re: [Utah-astronomy] Surface Brightness To: "Utah Astronomy" <utah-astronomy(a)mailman.xmission.com> Date: Monday, March 30, 2009, 1:32 PM Jim: Your log10 math is correct. But the formula may be in different units than the 10 to -6 value your picked up from another source. DT --- On Mon, 3/30/09, Jim Gibson <jimgibson00(a)yahoo.com> wrote: > From: Jim Gibson <jimgibson00(a)yahoo.com> > Subject: [Utah-astronomy] Surface Brightness > To: "Utah Astronomy" <utah-astronomy(a)mailman.xmission.com> > Date: Monday, March 30, 2009, 8:31 AM > I Need help from some of you math > wiz-bangs. I looked up on a chart of surface brightness that > M1 has a surface brightness of 35 * 10 to the minus 6; or > .000035. I found a formula for surface brightness (http://en.wikipedia.org/wiki/Surface_brightness) that > states S = m + 2.5 * log10A where m is point-magnitude and A > is the area in square arcseconds. I went on my planetarium > software and measured M1 to be approximately 440” X 260” > arcseconds or 114,400 square arcseconds. > > To further complicate maters I used an Excel spread sheet > to do the math for me so I could use it for different > objects. Excel is telling me that Log10(114,400) = 5.058, > and plugging back into the formula 2.5 * 5.058 = 12.6 and > + 8.4 = 21. 21 is a loooong ways from .000035. I figure > the problem has to be in the Log10 area of my math. Or, they > are saying to different things from which I am confused. > > > > _______________________________________________ > 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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