Tag Archives: Coma Berenices

Drafting/Architect Circles – Know Your Field Of View!

From the “Why didn’t I think of that sooner?” Department…

Binoculars are, far and away, the best way to start in observational astronomy (after you have some of the constellations figured out first, of course). The Moon reveals great new detail even at low magnification, the four Galilean Moons of Jupiter are obvious (when they’re not transiting or being “occulted” by Jupiter), all of the Messier objects are find-able (with a little practice and either lots of time or one lucky clear evening in March), and the sky becomes a busy highway of satellites that are otherwise too small to reflect significant light for naked eye viewing. Perhaps less pragmatically but nonetheless significant, the ownership of one simple, easy to produce, easy to use, easy to master piece of paired glassware connects you to the magnification-enhanced world of astronomy begun with Galileo, who used a much poorer quality and lower magnification telescope than those found in Big-Box Stores to forever and disruptively change how Western Civilization (and beyond!) placed itself in the Universe.

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That all sounds profound I guess, but you’ve got a book open and are trying to keep track of a flashlight while keeping your arm still as you bounce your head back-and-forth in this really dense part of sky because you don’t know if you’re looking at M36, M37, or M38 in Auriga and you know you’ll NEVER find that part of the sky again. The, if you’ll pardon the expression, dark art of star-hoping is one that absolutely requires practice. More importantly, it requires having a proper frame of reference. I admit that I spent more than a few months with my trusty Nikon Action 12×50′s without ever actually having a handle on just how big the piece of celestial real estate I was staring at was.

It may seem obvious but is something you (well, I) didn’t think to use to your (well, my) immediate advantage. The magnification in the binos does NOT change! You are constantly looking at the same-sized region. This means that you can easily correlate magnification to real estate and know exactly what the limit of your in-eyepiece star-hopping is.

My solution, and one that is generally applicable to all your binoculars (and low-magnification eyepieces in your scope), was to buy an architect or drafting circle set. Yes, one of the green numbers with all the holes. If you have one book you’ve committed to (in my case, Sky And Telescope’s Pocket Sky Atlas, but I also have a copy of the Cambridge Star Atlas that hasn’t had its spine properly cracked yet), find some obvious star groupings, see how many of them you can get in your field of view, crack your book open to the right page, and overlay until your circle engulfs only what you see.

Simple! This simple tool dramatically improved my star-hopping aptitude. Using the Sky Atlas and a pair of 12×50′s, I can just barely get the stars Mizar/Alcor and Alioth from the handle of the Big Dipper into the field of view – this corresponds to a 1.1250″ circle…

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For the Cambridge Atlas, this same piece of sky encompasses a 0.8125″ circle.

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I can plot the path to dim or densely-packed objects at leisure by finding bright stars or small groupings and “walking” my view along the path of overlaid circles, always knowing what I should and should not be seeing at any time (minus the odd planet, satellite, Milky Way supernova, etc.).

Depending on how much celestial real estate your star atlas covers per page, you can even take it one step farther. I have recently begun carrying around Version B of the awesome TriAtlas, which is a free 107-page star chart with stars down to magnitude 11.6. This means lots of stars, but also a full 8.5″ x 11″ piece of paper for each of 107 pieces of the entire sky. In working through Coma Berenices to find my favorite galaxy (NGC 4565), I found that the effective magnification of the B TriAtlas charts are such that my 40 mm Pentax XL 40 (which, in my 12.5″ f/4.87 Dob, corresponds to a magnification of just under 40x) shows a piece of sky that corresponds to a 17/32″ (or 0.5312″) circle. This now becomes my finder circle for knowing what I should see through this eyepiece (inverted in the Dobsonian, of course). With some object found by a 40x search, I can then step up the magnification with my 26 mm Nagler and 10 mm Ethos.

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As ever, the value of a very low-power eyepiece cannot be overstated! For those wanting to try this at home and don’t want to wait for shipping, drafting circles are available at Staples and Office Max in their “drafting” section. Those in Syracuse can also find them at Commercial Art Supply (where I get ALL of my red acetate).

CNYO Observing Log: Beaver Lake Nature Center, 2 May 2013

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Greetings fellow astrophiles,

May 2nd served as the rain date (due to rapidly-overcasting conditions on April 25th) for our first Beaver Lake Nature Center lecture of the year – The Guiding & Wandering Stars – Key Northern Constellations & Planet Observations. On hand to run scopes and engage in lecture duties were the author with a 12.5″ New Moon Telescope Dobsonian, Larry Slosberg with one Meade SCT and Bob Piekiel with another.

The Constellations have been with us for thousands of years, but there are only a few good, clear nights each month to memorize their positions as they slowly move across the sky! This outdoor lecture by the CNY Observers (www.cnyo.org) will briefly describe the history and importance of the Constellations as mythological, agricultural, and navigational guides, then will describe a simple system to begin to learn their relative positions. At the same time, Jupiter and Saturn are on opposite sides of the Southern sky, making excellent targets for binocular and telescope observing. Free and open to the public.

While the week including May 2nd will be known to some as a particularly bad week for maple tree allergies, the nighttime sky stayed quite clear and the bugs eventually froze around us to produce an excellent session. The attending crowd of about 35 served as test subjects for both our two new brochures (How The Night Sky Moves and Guide For New Observers) and our first official completely outdoors (Powerpoint-free) lecture (which, despite astronomy being such a visual hobby, worked will with just the brochure contents). In anticipation of some nighttime brochure reading, I put together some red light flashlights on the cheap locally. For anyone attempting similar, I found a four-pack of Dorcy AAA 6 LED Flashlights at Dicks Sporting Goods for $10. Some very minor surgery is needed to remove the top caps, but conversion to red light flashlights is straightforward with the help of a four-layer stack of red acetate purchased many moons ago from Commercial Art Supply in Syracuse.

406px-EB1711_Armillary_SphereDespite a little confusion about the start time (7:30 or 8:00), everyone had pulled in by 7:45 p.m., so we began the session with a good 30 minutes of physics. The goal of these Beaver Lake lectures is to not only observe objects, but to explain why the sky moves as it does so those trying to learn new constellations will understand what to expect both over the course of a night and over the course of a year. This began at the ground floor – understanding how the Earth moves around the Sun. With the help of an armillary sphere (which holds the Earth at its 23 degree tilt – see the image at left from wikipedia), the Earth’s movement around the Sun was demonstrated, specifically showing that the rotation axis stays pointed the same way as we revolve – thus resulting in Polaris appearing not to move over the course of the year despite the Earth shifting position by 300 million kilometers (2 astronomical units) every 6 months. Knowing that Polaris is always in the same place in the sky (whether it’s daytime or not) leads smoothly into a discussion of the circumpolar constellations and the benefit of learning these six constellations first (for this discussion and some how-to’s, I refer you to the CNYO brochure: Guide For New Observers).

Running a sunset-to-late-night session with a non-cycling crowd has (at least) two distinct advantages. First, the importance of dark adaption and the need to avoid smart phones (or avoid their use around others) can be stressed early in the evening. While enforcing protocols to maintain dark adaption at any kind of public lecture is usually a losing battle, anyone answering a phone did it in a very non-obvious manner, which was most welcome. Second, the mechanics of my Dobsonian telescope and Larry and Bob’s two motorized SCTs could be presented while still visible to attendees. More importantly, the proper observing technique for all could be demonstrated by showing (a) how to approach an eyepiece (I tell people to put their hands behind their back and simply lean into the eyepiece) and (b) just how easy it is to nudge a scope away from its target. Specifically for the Dob, I’m sure anyone who’s brought their scope to a public session has had at least one person lean on or pull closer an eyepiece. I’m pleased to report that, once the observing started, our collective intro to scope workings made my Dob-running life simple with no unplanned re-adjustments (just adjustments of the unmotorized kind).

As stated in a previous post (2013 March 8 – At The Syracuse Inner Harbor), new observers are best introduced to observing with easy objects that don’t require training. Deep, dim, distant galaxies are not useful starters for someone with no background in eyepiece observing. For my part, a good 70 minutes were spent on Jupiter (low in the Western Sky with all four Galilean moons present), Saturn (low in the Eastern Sky and my first view of it this year), Arcturus in Boötes (its shimmering in the sky both with and without magnification was a point of discussion for several near my scope), M13 (the globular cluster in Hercules, which served as a first “way out” object and an example of using the constellations as a “coarse adjustment” for finding Messier and other objects), and the pair Alcor and Mizar in the handle of the Big Dipper/tail of Ursa Major (to show the separation and additional detail that comes with magnification).

With a much smaller crowd around 9:30 p.m., I did treat a few interested parties to some more difficult observing in my scope – The Leo Triplet – after first briefly explaining the mechanics of averted vision. Of the five people who looked, all could make out M65, all could at least tell that something “was there” where M66 rested, and three people could tell that “something else” was there at NGC 3628‘s position. And I did miss a golden opportunity to observe NGC 4565 (my personal favorite) in Coma Berenices.

We closed up shop at 10 p.m., just as Cygnus and Lyra began to peak out over the horizon and announce the approaching return of our Summer Constellations. I am pleased to report that we will be hosting a Summer Session on Thursday, August 8th (with an August 15th rain date) where we will again do a little bit of mechanics and instruction outdoors, followed by Saturn, Venus, and all that our summer view of the Milky Way can provide.

August 8 – Stargazing with CNY Observers & Observing

CNY Observers (CNYO) hosts an introductory lecture to the Night Sky, focusing on planets and other objects observable during August and September.  Part of the lecture will discuss some simple ways to learn the Constellations, while the rest of the lecture will provide details about meteor showers, observing satellites and the ISS, and the ever-expanding description of our own Solar System.  If time and weather permits, some early evening views of Venus and Saturn will be had from the Beaver Lake parking lot.  Free for members; $2 for nonmembers.