While visiting my son and family in Las Vegas almost ten years ago, I became a member of the Las Vegas Astronomical Society. Soon afterwards, I began an email correspondence with one of the members, Fred Rayworth. We discussed the possibility of developing a monthly report, primarily designed to promote visual observing, while allowing amateurs the opportunity to share their observations and work.
Many years ago, as far back as the mid-70’s, I envisioned such a report, but this was in the days before the internet, emails, and blogs.
In February 2009, the first report was issued and the Observer’s Challenge was founded. We celebrated our 96th consecutive monthly report with the February 2017 edition. The report has inspired me to go outside even when I would much rather have stayed inside.
It’s always been my opinion that every amateur needs a goal. It might be observing the entire Messier catalog, maybe the Herschels, or any of the other list of objects provided by the Astronomical League. It could even be a serious scientific study, or maybe becoming an active AAVSO member, or perhaps as a participate of the Observer’s Challenge itself!
The list of potential projects is endless. Amateur astronomy does not have to be boring! Roger Ivester
March Challenge Report: Open cluster M67 in Cancer.
Image provided by Mario Motta of Massachusetts using a 6-inch refractor:
The brightest star in open cluster, M67 (NE edge) and the color as noted by observer’s as following:
I think all will agree that participated in the double star “Winter Albireo” color determination, had a great time. The February report had the greatest number of participants of any observer’s challenge since it’s inception.
We all know that color perceptions of stars can be subjective.
It was James Mullaney and Tom English that inspired my interest in star colors, or red stars in particular, over 25 years ago. Whenever I look at an open star cluster, the first thing I look for is yellow, orange or red star(s). Of course this carries over to colorful double and multiple stars also. Roger Ivester
*Color listings of bright star in open cluster M67:
I checked the star out last night with the 4.5 incher and I described the color as “topaz yellow”. Can try it again with the 4 inch refractor. The weather was fine as humidity was low and we had some strong winds during the night. Also we only have few patches of snow left so less light pollution! Only got a month left of darkness so I will try to do some observations tonight as well. Jaakko Saloranta – Observer from Finland
19 March 2003, 10-inch at 115×: Yellow. (Also: “brightest star well within group south of center looks orange.”)
24 March 2003, 10-inch at 115×: Yellowish
February 2008, 105mm at 17×: Yellow-orange
Earlier observations back to 1980 don’t mention a color. Later observations with binoculars don’t mention a color. Sue French
March 2017: 6-inch Achromatic refractor @ 50x: “The star appeared orange” James Dire
February 2017: 6-inch f/6 reflector@ 76x “rust colored”
February 1996: “80 mm f/15 refractor “no color noted”
March 1995: 10-inch “brightest star in cluster on NE tip is yellow @ 71x
April 1994: 10-inch “one bright yellow star on the NE tip of the cluster @ 71x
April 1993: 10-inch “yellow star on NE tip” Roger Ivester – Observer from North Carolina
This cluster is barely visible to the naked eye as a nebulous patch in the same “field of view” with Praesepe under truly dark skies. I was observing from Teide National Park, Canary Islands, Spain at an altitude of 7480 feet. Switching to a pair of 8×30 binoculars the nebulosity stars showing signs of resolution.
With a 4.5 inch Orion SkyQuest XT this is truly a fine cluster even under average observing conditions. I called M67 “A fine cluster of about 50 stars and many swirling chains of stars”. At low power there is a faint glow visible in the background slightly concentrated towards the middle. The core region of the cluster is roughly 12′ in size. With low power several chains of stars can be seen running NW and SE increasing the cluster’s visual size to nearly 30′ with a bit of imagination. Foreground 8th magnitude star NE from the cluster appears a “topaz yellow”. The brightest actual member of M67 is probably magnitude 9.8 TYC 814-1515-1
Two small patches of nebulosity can be discerned within the cluster. SW one resolved in to 4-5 stars between magnitudes 11-13 with high magnifications. NW one is slightly larger and with high magnification displays a fan-shaped grouping of ~8 stars. NW section also shows a circular region without stars but this feature is best seen with a larger aperture reminding me of NGC 7789. I could not identify the nearby cluster candidates Chupina 1 or Chupina 2 with the 4.5 inch telescope. Also I failed to see a specific form in M67 although I commonly see this cluster as an octopus. Jaakko Saloranta
Jaakko Saloranta pencil sketch with inverted colors:
Through my 105 mm refractor at 17x, Alpha Cancri and M67 share the field of view. This stunning group of many barely resolved and densely packed stars is irregular in both concentration and outline. A considerably brighter, yellow-orange star adorns its northeastern edge. At 47x a heavily populated tree of stars dominates the group, its shining trunk and star-leafed branches overspread 11′. At 87x, I count 80 stars in this amazing cluster, which spans about 22′. Sue French Deep-Sky Wonders – Observer from New York
I attempted M67 with 15×70 binoculars from my front yard (LP Bortle
Scale 8). I was able to locate the open cluster, but I was unable to
identify any structure other than a slightly brighter patch with
averted vision. The brightest star of the cluster at the NE tip
resolved amidst the rest of the patch; however, it was not bright
enough to for me to determine a color. Chris Elledge – Observer from Massachusetts
My 70th birthday was March 23. It was low-key – just dinner out with my wife. We’ll be getting together with immediate family for a more formal celebration on Thursday night. After returning home, I decided to spend a few hours at the ATMoB clubhouse. Because an extended period of cloudy weather was predicted for the upcoming week, I had decided to work on the Double Star Marathon using my 4.5-inch Orion reflector. Steve Clougherty was there with his 18-inch Dob and he was busy with Rich Nugent working on the March and April LVAS Observer’s Challenges!
I spent just enough time to work on the double stars setting in the west (Andromeda, Triangulum, Aries, Eridanus, and Lepus), plus a batch in Orion, then I put things away and observed with Rich and Steve.
While I had been working on the Double Star Marathon, Steve had been busy observing interacting galaxies, NGC 3395-96 in Leo Minor. The pair was faintly visible under magnitude 5 and rapidly hazing up skies.
He then turned to M67. Rich has already sent you a report on what he saw that night. I took a peek and, like Rich, had difficulty noting any obvious coloring of the main stars. I did notice that the cluster seemed to be comprised of two distinct populations – a dozen or so relatively bright members accompanied by several dozen fainter ones.
My first encounter with M67 was on the night of January 11, 1978, when I viewed it with a 3-inch f/10 reflector at 30X. I wrote in my log book, “Faint, ghostly, beautiful; Reminds me of M11. Contains three visible stars attended by a soft glow. Glow bursts into speckles of light with averted vision. General funnel shape.” More recently, I re-observed M67 with the same scope and a higher magnification of 60X. The cluster was better resolved; with a half dozen faint stars surrounded by another dozen or so averted vision stars. Glenn Chaple – Observer from Massachusetts
M67 is an open star cluster in the constellation Cancer located 105 arc minutes west of the star Acubens (Alpha Cancri). The cluster is also cataloged as NGC2682. The cluster was first recorded by the German astronomer Johann Gottfried Koehler in 1779 and then by Charles Messier in 1780. The cluster is magnitude 6.1.
M67 has nearly 100 stars between 10th and 14th magnitude spread over a diameter of about 30 arcminutes. The cluster is 2960 light years away and approximately 25 light years across. It is one the closest open clusters and thus one of the most studied. The cluster is several billion (3.2-5) years old. Unlike most star clusters that reside in the plane of the Milky Way, M67 lies 1500 light years away from the plane.
Stellar interactions have flung most of the lighter stars to the outer regions of the cluster, leaving the more massive stars in the center. In possible 5 billion more years, the cluster will no longer exists as its stars will have spread out too far from one another to be gravitationally bound.
My image of M67 was taken with 190 mm f/5.3 Maksutov-Newtonian telescope with an SBIG ST-2000XCM CCD camera. The exposure was 20 minutes. North is up and east is to the left. The faintest star in the image is 15th magnitude. The exposure captures how the cluster looks in my 14 inch Dob Newtonian.
I viewed the cluster this month with a 6-inch f/6.5 acromatic refractor with a 20mm Nagler eyepiece (50x). The brightest star, shown with the red arrow on my second image, is magnitude 7.8. This star appeared orange to me, but my image does not show that color. That was probably due to my image processing. I captured this image in 2010 and no longer have the original file to check my color processing accuracy.
Three stars stood out at the center of the cluster forming an “L”. I have drawn the L in yellow on the second image. The brightest of the three is magnitude 9.6, while the other two are 10.2. With the 6-inch refractor, I could not visually resolve the half-dozen stars inside of the triangle formed by those three stars. However, the area inside the triangle did not appear as dark as the space between other stars. So my eyes were capturing some of the photons from those unresolved stars. James Dire – Observer from Hawaii
Thursday, March 23, 2017: I was observing with Steve Clougherty at the clubhouse. We were using his 18-inch reflector. The sky was fair (a Bortle Scale 6 or perhaps a little better) but conditions were worsening. By 11 p.m. clouds were overtaking the sky and we ended our observations for the evening.
We decided to take a look at M67. It’s a lovely little cluster but, truth be told, I’ve never found it particularly interesting and have seldom observed it. Thanks for including it in the challenge list because I’ve learned quite a bit about it over the last month! By the way, there’s a nice limiting magnitude chart of M67’s stars on page 69 of this year’s RASC Handbook. I was particularly interested in seeing if it was possible to see the color of some of the cluster’s K-type giant stars. The only color I could see through Steve’s scope was a slight yellow-orange color in HIP 43491 (Spectral type K3) at magnitude ~9.8.
I didn’t pay attention to the nearby, brighter (mag. ~7.9) K0 foreground star (HIP43519/SAO98178) but I will check for color when the skies eventually clear.
Steve and I discussed the value of having an adequate star chart and a capable finder scope when star-hopping to deep sky objects. (We had been searching for April’s challenge: NGC3395/6) I’ll bet when hunting for challenging objects the real challenge isn’t seeing the object as much as it is finding the object! You have to be looking in the right place, right? My favorite print star atlas to have near the telescope is Interstellarum Deep Sky Atlas. This fine atlas shows stars to magnitude 9.5 which is perfect for the 80mm, RACI finders I use on my telescopes. (I use Project Pluto’s Guide v9.0 on my laptop when I need to go deeper.) As experienced star-hoppers well-know, we live and die by our finder system. I use a green laser pointer to roughly aim the scope then acquire the proper star field using the finder. If I can see the desired object in the finder…Bingo! I win. The next best thing to seeing the object itself is seeing the surrounding field stars visible in the atlas. Line the scope with those stars and…Bingo! I win. While I enjoy the chase, I don’t want it to take all night because I really enjoy the view!
As we all have seen, the finder scope that comes with many commercial telescopes is simply inadequate. I try to respectfully implore newbies with such telescopes to upgrade to a “pointer” (Telrad or green laser) and to buy a quality finder scope. It’s all about aperture, right? I decided to run a little test with M67.
Saturday, March 25.
The sky cleared during the early evening. Temperatures were dropping and surfaces were beginning to freeze over. Framingham enjoys (ahem!) Bortle Scale 7 skies most of the time. I could see Acubens (a cancri; magnitude 4.2) but not much fainter. I could just barely see M44 with my naked eyes but averted vision was necessary. I made a series of observations of M67 (60 degrees in altitude) using 10×21, 8.5×44, 10×50, and 20×80 binoculars. Here are my notes:
10×21: M67 was barely visible; easily missed! HIP43519/SAO98178 was not visible.
8.5×44: A whisper of light; averted vision necessary. HIP43519/SAO98178 was not visible.
10×50: Visible; faint, diffuse; averted vision was helpful. HIP43519/SAO98178 was visible but difficult
20×80: Easy; Obvious! HIP43519/SAO98178 was easily visible.
Richard Nugent – Observer from Massachusetts
M67: ! A beautiful but often-overlooked cluster in the shadow of the Beehive. “Vivid rich type of it exhaulted class.” “Resembles a nebula in small instruments.” “Whorls of stars remind one of a whirlpool.” “Star hues are predominantly rust, orange gold & yellow.” James Mullaney Celestial Harvest (Dover) Observer from Delaware