Last night being moderately warm with clear skies and good transparency, I pulled out a small 4 1/4" computer controlled short tube reflector for an evening of urban astronomy. Urban astronomy involves double stars and bright open clusters and not faint galaxies lost in the urban light pollution glare. Tonight, I was getting used to a new scope and decided to do a showcase open cluster tour in the anti-spinward unfolding Orion-Cygnus Arm that runs north-south along the east side of Orion from Orion to Canis Major and Puppis. (Although boring for most of the advanced amateurs on this list, the target detection confirmations at 127mm apeture from a light polluted location may be of use.) My other major goal of the night was to try practicing urban dark adapted observing techniques, i.e. - consistent use of an eye-patch and an Orion dark cloth hood. (My specific site in the aves is outside my back door and is riddled with intrusive neighbor "afraid of the dark" house lamps. ZLM was 18.1 mpsas per the Sky Quality Meter (4.1 mag). Transparency was much improved from a session on the previously night of 2-19 to 2-20. First, I tried unsuccessfully a second time to detect Comet 144P Kushida. Although on target, I concluded that 125mm of apeture was not enough to detect this comet from light polluted skies. Next, I skirted up to NGC 1647 - an open cluster on the east leg of Tau's horn for a quite telescopic limiting magnitude test. On of the first "projects" that I did on returning to astronomy in the early 2000's was a high-precision map of NGC1647 for TLM test purposes. NGC1647 Map http://members.csolutions.net/fisherka/astronote/observed/NGC1647/NGC1647_Pr... In this light polluted urban environment at v4.1, the 127mm reflector reached down to mag 10.4 The open cluster tour began high in the western sky with showcase open cluster M35 (NGC2168, 5.1v, 30' dia., dist. 0.816 kpc). A two-dimensional map from a north galactic pole view looking down on Sol and showing the clusters described in this post can be found at: http://members.csolutions.net/fisherka/astronote/observed/Reports/20090221Op... Cluster M35 cluster had good resolution at this apeture and light pollution. (I didnot make a note on the visibility of nearby open cluster NGC2158. NGC2158 is about 15 arcmins from M35. At a distance of 5 kpc, NGC2158 (8.6v, dia. 5') is the most distant open cluster visible in amateur class telescopes and is located in the Outer Arm. I will try for a detection tonight, weather permitting.) Next was M50 (NGC2323, 5.9v, 10' dia., dist. 0.929 kpc) in Puppis. This cluster had good resolution at this apeture and light pollution. Also in Puppis is the open cluster pair M46 and M47 (M46, NGC2422, 4.4v, dia. 20', dist. 1.375 kpc; M47, NGC2437, 6.1v, dia. 25', dist. 0.49 kpc). Their alignment is optical only, as indicated by their relative distances. As can be seen in the SEDS images, the further M46 is the more interesting, but fainter detailed target. http://www.seds.org/messier/m/m046.html http://www.seds.org/messier/m/m047.html Clark's classic _Visual Astronomy of the Night Sky_ includes a detail telescopic limiting magnitude map for M46. But a TLM map for M46 can also be quickly pulled up online from the Webda cluster database: http://www.univie.ac.at/webda/cgi-bin/ocl_page.cgi?dirname=ngc2422 http://www.univie.ac.at/webda/cgi-bin/chart_frame.cgi?ngc2422 (Use the Chart Form to set the limiting magnitude to 9 or 10.) Next, I wrapped up with two classic wide-field open clusters M44 (NGC2632, 3.1v, dia. 80', dist. 0.19 kpc, age: 562 million years) in Cancer and M48 in Hydra (NGC2548, 5.8v, dia. 40', dist. 0.77 kpc, age 794 million years). This clusters are located sidereal eastward of the prior targets and are "off" the main galactic disk. The galactic latitude of both is higher as compared to the earlier targets (M44 +15.4 b; M48 +32.5 b). M44 is close-in to Sol but is running high above the galactic plane. This accounts for its relatively old age and the prevalence of yellow stars in this cluster. Most clusters do not survive one galactic rotation (~220 million years), because they form in the galatic plane and are torn apart by gravity interactions and gravity density waves. The galactic year, the time it takes the Sun to complete one revolution around the Milky Way's core, is approx. 220 million years or 8.34 log10(years). Half of all open clusters disperse in just under one galactic year (8.13 log10(years) or 218 million years). The third quartile of open clusters disperses in just under two galactic years (8.6 log10(years) or about 430 million years). Popular old clusters and moving groups that have survived more than two galactic years and into the fourth quartile include M044 (Beehive Cluster, age ~log 8.7 Myrs) and M048 (age ~log 8.9 Myrs). On finishing the open cluster tour, it was 12:30-1am, so it turned my attention to the solar system. Comet Lulin was quickly located between and south of gam and eta Vir. It could easily be seen at 40x, but no tail detail was visible from this light polluted location. Tonight, 2009-2-22 6UT (2009-2-22 12:01am), Comet Lulin will at the edge of a 1 deg telescopic TFOV of magnitude 6.3 star SAO119100 and an SLC horizon altitude of about 37 degrees. In a binocular view, pan 2 degs east and 1 degs south of bet Vir (Zavijah). Lulin is streaking towards its rendevous with Saturn on 2-23, 2-24. At 1:00am, Saturn is nearly transiting and gave good, crisp and steady views with good seeing. This may be the time for some of the best Saturn views this year with its unique edge on rings. Although the early morning hour is inconvienent, I recommend setting the alarm clock for a quick 1 or 2am setup. Finally, I tried to hunt down Ceres, which is featured page 60 of the March 2009 Sky and Telescope. (Initially I had a hard time confirming a detection. My asteriod element file in my planetarium program was outdated.) Ceres (6.0v) was seen with 8x35 binos and the 4 1/4 reflector. For binocular detection, Ceres currently (2/21) is about 4 degs northwest (PA 328) of del Leo (Zosma). The parallelogram asterism is formed by: 72 Leo East 4.6v 67 Leo North 5.7v Ceres South 7.0v 54 Leo West 4.5v Ceres should not be confused in the bino view with nearby 64 Leo (6.5v). The Flamsted referenced stars are found on most charts. Ceres is at the "bottom" or most southern vertex of the diamond shape. Also helpful for locating Ceres in binoculars is 54 Leo. 54 Leo anchors the "bottom" or south of a small, prominent triangular asterism consisting of: 54 Leo South anchor 4.5v 50 Leo Northeast corner 6.4v 48 Leo Northwest corner 6.2v Weather picture for tonight as of 3pm MST is uncertain. Fronts appear to still be approaching, but trapped on the west coast. The 3pm MST SLC sky has light leading edge altocirrus clouds. This has been the situation for the last two nights. Clear Skies - Kurt
Kurt, Great report. Thanks. I like to hear more of that stuff. Jim --- On Sat, 2/21/09, Canopus56 <canopus56@yahoo.com> wrote: From: Canopus56 <canopus56@yahoo.com> Subject: [Utah-astronomy] Urban Obs Rep 2-20 10pm 2-21 2am MST To: "Utah Astronomy List Serv" <utah-astronomy@mailman.xmission.com> Date: Saturday, February 21, 2009, 3:02 PM Last night being moderately warm with clear skies and good transparency, I pulled out a small 4 1/4" computer controlled short tube reflector for an evening of urban astronomy. Urban astronomy involves double stars and bright open clusters and not faint galaxies lost in the urban light pollution glare. Tonight, I was getting used to a new scope and decided to do a showcase open cluster tour in the anti-spinward unfolding Orion-Cygnus Arm that runs north-south along the east side of Orion from Orion to Canis Major and Puppis. (Although boring for most of the advanced amateurs on this list, the target detection confirmations at 127mm apeture from a light polluted location may be of use.) My other major goal of the night was to try practicing urban dark adapted observing techniques, i.e. - consistent use of an eye-patch and an Orion dark cloth hood. (My specific site in the aves is outside my back door and is riddled with intrusive neighbor "afraid of the dark" house lamps. ZLM was 18.1 mpsas per the Sky Quality Meter (4.1 mag). Transparency was much improved from a session on the previously night of 2-19 to 2-20. First, I tried unsuccessfully a second time to detect Comet 144P Kushida. Although on target, I concluded that 125mm of apeture was not enough to detect this comet from light polluted skies. Next, I skirted up to NGC 1647 - an open cluster on the east leg of Tau's horn for a quite telescopic limiting magnitude test. On of the first "projects" that I did on returning to astronomy in the early 2000's was a high-precision map of NGC1647 for TLM test purposes. NGC1647 Map http://members.csolutions.net/fisherka/astronote/observed/NGC1647/NGC1647_Pr... In this light polluted urban environment at v4.1, the 127mm reflector reached down to mag 10.4 The open cluster tour began high in the western sky with showcase open cluster M35 (NGC2168, 5.1v, 30' dia., dist. 0.816 kpc). A two-dimensional map from a north galactic pole view looking down on Sol and showing the clusters described in this post can be found at: http://members.csolutions.net/fisherka/astronote/observed/Reports/20090221Op... Cluster M35 cluster had good resolution at this apeture and light pollution. (I didnot make a note on the visibility of nearby open cluster NGC2158. NGC2158 is about 15 arcmins from M35. At a distance of 5 kpc, NGC2158 (8.6v, dia. 5') is the most distant open cluster visible in amateur class telescopes and is located in the Outer Arm. I will try for a detection tonight, weather permitting.) Next was M50 (NGC2323, 5.9v, 10' dia., dist. 0.929 kpc) in Puppis. This cluster had good resolution at this apeture and light pollution. Also in Puppis is the open cluster pair M46 and M47 (M46, NGC2422, 4.4v, dia. 20', dist. 1.375 kpc; M47, NGC2437, 6.1v, dia. 25', dist. 0.49 kpc). Their alignment is optical only, as indicated by their relative distances. As can be seen in the SEDS images, the further M46 is the more interesting, but fainter detailed target. http://www.seds.org/messier/m/m046.html http://www.seds.org/messier/m/m047.html Clark's classic _Visual Astronomy of the Night Sky_ includes a detail telescopic limiting magnitude map for M46. But a TLM map for M46 can also be quickly pulled up online from the Webda cluster database: http://www.univie.ac.at/webda/cgi-bin/ocl_page.cgi?dirname=ngc2422 http://www.univie.ac.at/webda/cgi-bin/chart_frame.cgi?ngc2422 (Use the Chart Form to set the limiting magnitude to 9 or 10.) Next, I wrapped up with two classic wide-field open clusters M44 (NGC2632, 3.1v, dia. 80', dist. 0.19 kpc, age: 562 million years) in Cancer and M48 in Hydra (NGC2548, 5.8v, dia. 40', dist. 0.77 kpc, age 794 million years). This clusters are located sidereal eastward of the prior targets and are "off" the main galactic disk. The galactic latitude of both is higher as compared to the earlier targets (M44 +15.4 b; M48 +32.5 b). M44 is close-in to Sol but is running high above the galactic plane. This accounts for its relatively old age and the prevalence of yellow stars in this cluster. Most clusters do not survive one galactic rotation (~220 million years), because they form in the galatic plane and are torn apart by gravity interactions and gravity density waves. The galactic year, the time it takes the Sun to complete one revolution around the Milky Way's core, is approx. 220 million years or 8.34 log10(years). Half of all open clusters disperse in just under one galactic year (8.13 log10(years) or 218 million years). The third quartile of open clusters disperses in just under two galactic years (8.6 log10(years) or about 430 million years). Popular old clusters and moving groups that have survived more than two galactic years and into the fourth quartile include M044 (Beehive Cluster, age ~log 8.7 Myrs) and M048 (age ~log 8.9 Myrs). On finishing the open cluster tour, it was 12:30-1am, so it turned my attention to the solar system. Comet Lulin was quickly located between and south of gam and eta Vir. It could easily be seen at 40x, but no tail detail was visible from this light polluted location. Tonight, 2009-2-22 6UT (2009-2-22 12:01am), Comet Lulin will at the edge of a 1 deg telescopic TFOV of magnitude 6.3 star SAO119100 and an SLC horizon altitude of about 37 degrees. In a binocular view, pan 2 degs east and 1 degs south of bet Vir (Zavijah). Lulin is streaking towards its rendevous with Saturn on 2-23, 2-24. At 1:00am, Saturn is nearly transiting and gave good, crisp and steady views with good seeing. This may be the time for some of the best Saturn views this year with its unique edge on rings. Although the early morning hour is inconvienent, I recommend setting the alarm clock for a quick 1 or 2am setup. Finally, I tried to hunt down Ceres, which is featured page 60 of the March 2009 Sky and Telescope. (Initially I had a hard time confirming a detection. My asteriod element file in my planetarium program was outdated.) Ceres (6.0v) was seen with 8x35 binos and the 4 1/4 reflector. For binocular detection, Ceres currently (2/21) is about 4 degs northwest (PA 328) of del Leo (Zosma). The parallelogram asterism is formed by: 72 Leo East 4.6v 67 Leo North 5.7v Ceres South 7.0v 54 Leo West 4.5v Ceres should not be confused in the bino view with nearby 64 Leo (6.5v). The Flamsted referenced stars are found on most charts. Ceres is at the "bottom" or most southern vertex of the diamond shape. Also helpful for locating Ceres in binoculars is 54 Leo. 54 Leo anchors the "bottom" or south of a small, prominent triangular asterism consisting of: 54 Leo South anchor 4.5v 50 Leo Northeast corner 6.4v 48 Leo Northwest corner 6.2v Weather picture for tonight as of 3pm MST is uncertain. Fronts appear to still be approaching, but trapped on the west coast. The 3pm MST SLC sky has light leading edge altocirrus clouds. This has been the situation for the last two nights. Clear Skies - Kurt _______________________________________________ Utah-Astronomy mailing list Utah-Astronomy@mailman.xmission.com http://mailman.xmission.com/cgi-bin/mailman/listinfo/utah-astronomy Visit the Photo Gallery: http://gallery.utahastronomy.com Visit the Wiki: http://www.utahastronomy.com
participants (2)
-
Canopus56 -
Jim Gibson