The year 2020 will be remembered for many things, most of them unpleasant, but against the odds it has actually been a good year for amateur astronomy in general and HAS in particular. Despite the shadow of the pandemic and for a myriad of reasons, public interest in astronomy surged as did membership in HAS.
by Bill Pellerin, GuideStar editor
Object: Mirzam, sometimes spelled Murzim, β CMa
Class: β Cepheid Star
Constallation: Canis Major (CMa)
Magnitude: 1.98
Period: 6 hours
R.A.: 6 h 22 m 42 s (2000 coordinates)
Dec: -17 deg 57 min 21 sec
Size/Spectral: B1
Distance: 500 ly
Optics needed: Unaided eye or small telescope
When your eye gets anywhere near Sirius, the brightest star in the sky (not counting our sun), you’ll be dazzled by it. Look again, and to the west-southwest, about 5.5 degrees away you’ll find the β star of the constellation, Mirzam. It’s bright, shining at a magnitude of 1.98 and you should be able to find it easily.
This star is a β Cepheid star (the designation, β CMa is simply coincidental with the β Cepheid category). Interestingly, this star is sometimes considered the prototype for the β Cepheid category of variable stars, but, more commonly, and easier to understand, the star β Cephei (β Cep) is considered the prototype. The General Catalog of Variable Stars (GCVS) identifies these type of stars as BCEP variables.
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Since ole Charlie Messier is not around to herald the conjunction of Saturn and Jupiter, I thought I would try to fill in the breach with some observing tips and thoughts.
Note of interest: There are those who believe a similar conjunction between Jupiter and Saturn 2,000 – odd years ago, might have been the source of the “Star of Bethlehem” event heralding the birth of Jesus.
As I have pointed out in just about every monthly Messier Column this year in our Houston Astronomical Society newsletter, GuideStar, Jupiter and Saturn will have a dance on December 21, 2020, that is a once in a lifetime event. Some folks believe these planets will merge and appear as a single very bright "star". This may be true if your vision is sub-par. But for those of us with relatively normal vision, we will observe two extremely close-together “stars” – an eye-catching event most of us will never again witness in our entire lives. One should be able to see it with no optical aids.
Like most of you reading this, I, too am looking forward to putting 2020 in my rearview mirror and hoping that 2021 brings about a much better outlook than we’ve had for the last 9 months or so. We continue to see a profound impact from COVID-19 on millions of people – physically, economically, and mentally – and the devastating losses of life continuing to mount as we see another resurgence in various parts of our country. Here at the Houston Astronomical Society, we have known several members who have come down with COVID-19 but fortunately, I am not aware of anyone who has lost their life in our club.
Its December and as the weather cools and the toddies get hotter, all good astronomers thoughts turn to – NEW EQUIPMENT!! Which brings us to our subject for this month’s AP Corner.
Over the last month, there have been a number of our members seeking input on intended equipment purchases to upgrade their systems, and maybe expanding their options to get into astrophotography. For instance, Jim King asked the HAS list server whether or not he would see enough visual improvement to upgrade to a Celestron Edge HD SCT (on an Alt Az mount), which would also possibly open the door to astrophotography later on.
This type of question has multiple answers, depending on the objective of the person asking the question. As Jeff Lepp responded – “Traditional advice is buy a scope for visual or buy a scope for astrophotography but don’t buy a scope to do both.” He then went on to explain that the state of current technology and cost of astrophotography equipment makes this answer somewhat obsolete. “It all depends on what you want to do” he said.
There are several ways this could go, depending on how important astrophotography is to Jim. So, for the purposes of answering this question, I will start by answering the question as Jim asked, take into account that in astrophotography “there is always an upgrade” then finish with advice to someone who really intends to get into astrophotography. In each case the upgrades are presented in the order from lower to higher cost.
Jim’s primary question is about the quality of the Edge HD optics for visual observing. An SCT on an Alt-AZ is a very good visual telescope. The Alt-Az mount makes for comfortable observing and is easy to automate for GoTo operation. The optics on a standard SCT are designed to be easy to mass produce, with both the primary and secondary mirrors ground to a spherical shape (very forgiving) and the corrector plate designed to eliminate spherical aberration from the mirrors. The result is good images in the center of the FOV, but because the focal plane is curved, modern wide field of view eyepieces will be less focused and other aberrations like coma can be seen at the edges of the image.
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C 891 is an edge-on spiral galaxy located 30 million light years from us, within the local supercluster. It was discovered by William Herschel in 1784. It is one of the brightest and best-known edge-on galaxies, exceeded in impressiveness only by the Sombrero galaxy M104, and NGC 4565. However, when I first viewed it several years ago I found it to be a bit more difficult to see than I expected for such a well-known galaxy. Nonetheless, once it is located it isn’t too hard to see even in a smaller telescope. I first observed it in 2014 in my 10” dob at 48x and I descibed it simply as “thin streak, with a dark lane in the middle.” I re-observed it in my 16” just weeks ago at 131x and logged “much lower surface brightness than anticipated, but easily seen direct vision; long and thin, tapering to the points from the central bulge; very obvious dust lane directly down the center; no bright central nucleus; pretty much uniform in brightness; a few stars superimposed.” NGC 891 can be seen in considerably smaller telescopes than these, though it will be more challenging, and clear dark skies certainly help (both of my quoted observations here were from the HAS dark site). Key details to notice include the long thin overall shape, and the dark dust lane bisecting the long axis of the galaxy.
By: Steve Goldberg
Asterism: a grouping of stars that form a recognizable pattern.
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The object NGC 2169 is an asterism that looks like the number “37”. It is easily located near the bend of Orion’s out stretched arm, above the star Betelgeuse, near star Xi 70 Ori. 2169 is officially classified as an open cluster with other catalog names of Collinder 83 (CR 83) and OCL 481 (Open Cluster). |
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The FOV in the second picture is from a 10” Dob with a 15mm eyepiece. A reflecting telescope gives you an upside down image. |
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Time to RENEW YOUR HAS MEMBERSHIP so you can take your 2021 Dark Site Training January 1st and get the new gate code before it changes on March 6th! HAS memberships run from 1 January to December 31. Fortunately, renewing your membership is fast and easy! |
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Membership dues are a bargain. Dues amounts:
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Two ways to renew:
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We hope that you will continue to support HAS and look forward to seeing you at our next meeting or event at the Columbus dark sky site! — Mike Edstrom |
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What You Need to Know About the Texas Star Party
