Tag Archives: Coma

NASA Space Place – Comet Campaign: Amateurs Wanted

Poster’s Note: One of the many under-appreciated aspects of NASA is the extent to which it publishes quality science content for children and Ph.D.’s alike. NASA Space Place has been providing general audience articles for quite some time that are freely available for download and republishing. Your tax dollars help promote science! The following article was provided for reprinting in January, 2017.

By Marcus Woo

2013february2_spaceplaceIn a cosmic coincidence, three comets will soon be approaching Earth—and astronomers want you to help study them. This global campaign, which will begin at the end of January when the first comet is bright enough, will enlist amateur astronomers to help researchers continuously monitor how the comets change over time and, ultimately, learn what these ancient ice chunks reveal about the origins of the solar system.

Over the last few years, spacecraft like NASA’s Deep Impact/EPOXI or ESA’s Rosetta (of which NASA played a part) discovered that comets are more dynamic than anyone realized. The missions found that dust and gas burst from a comet’s nucleus every few days or weeks—fleeting phenomena that would have gone unnoticed if it weren’t for the constant and nearby observations. But space missions are expensive, so for three upcoming cometary visits, researchers are instead recruiting the combined efforts of telescopes from around the world.

“This is a way that we hope can get the same sorts of observations: by harnessing the power of the masses from various amateurs,” says Matthew Knight, an astronomer at the University of Maryland.

By observing the gas and dust in the coma (the comet’s atmosphere of gas and dust), and tracking outbursts, amateurs will help professional researchers measure the properties of the comet’s nucleus, such as its composition, rotation speed, and how well it holds together.

The observations may also help NASA scout out future destinations. The three targets are so-called Jupiter family comets, with relatively short periods just over five years—and orbits that are accessible to spacecraft. “The better understood a comet is,” Knight says, “the better NASA can plan for a mission and figure out what the environment is going to be like, and what specifications the spacecraft will need to ensure that it will be successful.”

The first comet to arrive is 41P/Tuttle–Giacobini–Kresák, whose prime window runs from the end of January to the end of July. Comet 45P/Honda–Mrkos–Pajdušáková will be most visible between mid-February and mid-March. The third target, comet 46P/Wirtanen won’t arrive until 2018.

Still, the opportunity to observe three relatively bright comets within roughly 18 months is rare. “We’re talking 20 or more years since we’ve had anything remotely resembling this,” Knight says. “Telescope technology and our knowledge of comets are just totally different now than the last time any of these were good for observing.”

For more information about how to participate in the campaign, visit www.psi.edu/41P45P46P.

Want to teach kids about the anatomy of a comet? Go to the NASA Space Place and use Comet on a Stick activity! spaceplace.nasa.gov/comet-stick/

This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

Caption: An orbit diagram of comet 41P/Tuttle-Giacobini-Kresak on February 8, 2017—a day that falls during the comet’s prime visibility window. The planets orbits are white curves and the comet’s orbit is a blue curve. The brighter lines indicate the portion of the orbit that is above the ecliptic plane defined by Earth’s orbital plane and the darker portions are below the ecliptic plane. This image was created with the Orbit Viewer applet, provided by the Osamu Ajiki (AstroArts) and modified by Ron Baalke (Solar System Dynamics group, JPL). ssd.jpl.nasa.gov/sbdb.cgi?orb=1;sstr=41P

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CNYO Observing Log: The Winter Of Lovejoy – Green Lakes, Jamesville Beach, And New Moon Telescopes HQ – January 9 to 14, 2015


Comet Lovejoy imaged on January 10th by the ever-impressive CNY astrophotographer Stephen Shaner. From his CNYO Facebook Group post: Last night was the first in over three months it was clear enough to shoot, but it worked out well because Comet Lovejoy is at its peak. Here’s a quick process of about 40 minutes of exposures between 8-9 PM as it crossed the meridian. FOV is roughly three degrees. Distinct pale green coma in the eyepiece but unable to make out a tail or see it naked eye.

The 2015 skies are going to be full of comets. Well, at least six, to be exact, that will be either naked eye- or binocular-visible. That’s still quite a few to those keeping track! The amateur astronomy community has taken heroic efforts to scientifically identify and track new comets in the last, say, 400 years. The rise of, for instance, the Panoramic Survey Telescope & Rapid Response System (or panSTARRS) as a method for finding and tracking both comets and near-earth asteroids (or, lumped together, “objects,” for which you might hear the abbreviation “NEOs”) has greatly increased the number of accounted-for fuzzy objects in our fields of view (and provided us a giant leap in our existential risk assessment infrastructure to boot). Quite simply, we’ve more + better eyes on the skies, meaning we’re bound to continue to find more and more comets and asteroids. You can even subscribe to NASA twitter feeds that announce the passing-by of these hopefully passers-by (see @AsteroidWatch and @NasaNEOCam).

The discovery of NEOs may or may not qualify as a modern John Henry-ism, as amateur astronomers are still discovering objects at a decent pace thanks to improvements in their own optics and imaging equipment. Comet Lovejoy, C/2014 Q2, is one such recent example discovered by famed modern comet hunter Terry Lovejoy (who has five comets to his name already).

Comet Lovejoy And More In CNY

Comet Lovejoy has made the winter sky that much more enjoyable (and below freezing cold that much more bearable) by reaching peak brightness in the vicinity of the prominent winter constellations Taurus and Orion. Visible soon after sunset and before the “really cold” temperatures set in (after 10 p.m. or so), Lovejoy has been an easy target in low-power binoculars and visible without equipment in sufficiently dark skies. Now on its way out of the inner solar system, its bright tail will shrink and its wide coma (that gives it its “fuzziness”) will disappear as the increasingly distant Sun is unable to melt Lovejoy’s surface ice. Those of us who dared the cold, clear CNY skies these past few weeks were treated to excellent views, while the internet has been flooded with remarkable images of what some have described as the most photographed comet in history (a title that will likely be taken from it when a few other comets pass us by during warmer nights this year).


The tiki lounge at Green Lakes State Park, 9 January 2014.

The first observing session around Syracuse this year happened at Green Lakes State Park on January 9th. Bob Piekiel, one of CNY’s best known and most knowledgable amateur astronomers, had his Celestron NexStar 11 in the parking lot behind the main office, which was fortunately kept open for attendees hoping to warm up between views. To Bob’s C11 was added my Zhumell 25×100’s, providing less magnification but a wider field of view to take in more of the comet’s core, tail, and nearby stars.


A very prominent Orion and arrow-ed Comet Lovejoy from the Green Lakes parking lot. Photo by Kim Titus.

The Friday night skies were only partially on our side, offering a few short-lived views of the Orion Nebula and Lovejoy. Jupiter was just bright enough to burn through some of the cloud cover to our East, giving us slightly muddled but otherwise decent views of it and its four largest satellites for about 10 minutes. By our 9 p.m. pack-up and departure, the skies were even worse – which is always a good feeling for observers (knowing they didn’t miss a chance for any additional views by packing up early).

The night of Saturday, January 10th turned into a much better night for observing, offering a good opportunity for some long-exposure images to try to capture Lovejoy just past its luminous prime. The following image was taken from one of the parking lots at Jamesville Beach – the same spot where Larry Slosberg, Dan Williams and I observed the nova in Delphinus. Light pollution aside from the 30 second exposure, the brightest constellations are clearly visible and a fuzzy, bright green star is clearly visible in the full-sized image. Click on the image below for a larger, unlabeled version of the same.


An array of Winter’s finest from Jamesville Beach, 10 January 2014, 8:00 p.m. Click on the image for a full and unlabeled version.

The imaging continued in Marcellus on January 10th, with Bob Piekiel producing a zoomed in view of Lovejoy.


An unmistakable view of Comet Lovejoy. Image by Bob Piekiel.

As with all astronomical phenomena (excluding solar viewing, of course), the best views come from the darkest places. A third Lovejoy session was had up in West Monroe, NY on Wednesday, January 14th with fellow CNYO’er Ryan Goodson at New Moon Telescopes. Putting his 27” Dob to use, the green-tinted Lovejoy was almost bright enough to tan your retina. With dark skies and no observing line, we then attacked some subtler phenomena, including the Orion Nebula in Orion, the Eskimo Nebula in Gemini, and the Hubble Variable Nebula in Monoceros. The images below are our selfie with Lovejoy and the best of Winter, a snapshot near the zenith (with Jupiter prominent), and the Northern sky (click on the images for larger, unlabeled versions).


Ryan and I pose for 30 sec, our fingers completely missing the location of Lovejoy (red arrow). Click for a larger view.


Some of Winter’s finest from NMT HQ, including a prominent Jupiter just to the west of (and about to be devoured by) the constellation Leo. Click for a larger view.


A view of NMT’s opening to the North, including Cassiopeia at left (the sideways “W”), the Big Dipper in the middle, and Jupiter at the right. Click for a larger view.

A Clothing Thought…

As we can all attest to, the nighttime temperatures this month have oscillated between bitterly cold and painfully cold. The pic of my Element’s thermometer at my midnight departure from West Monroe read -12 F (and the tire inflation warning light stayed on until I hit 81 South), yet with the exception of the tips of my toes, I wasn’t very bothered by the cold.


2015jan22_nmt_layersIt’s one of the cold realities of amateur astronomy – you never realize how cold it can get outside until you’re standing perfectly still at a metal eyepiece. The solution is as old as the sediment-grown hills – layers! The top half of my outfit for the evening is shown below, featuring six (yes, six) layers from turtleneck to final coat. My bottom half featured three layers that decorum permits me from showing here. For those wondering how the blood still flows below the belt, the answer is simple – buy yourself an outer layer two or three sizes larger than you usually wear. In my case, my outer coat’s a bit baggy and my outer pants are a very tightly-meshed pair of construction pants with a 40” waist (from a trip to DeJulio’s Army & Navy Store on Burnet Ave. in Syracuse).

And don’t worry about color coordinating. The nighttime is the right time for the fashion unconscious.

CNYO Feature: Going Big

Thinking of going big? Of course you are, and right you should be. Nothing makes up for aperture under dark skies if it’s deep sky objects you’re after. Some may make an argument that refractors show slightly sharper planetary images, but simple physics says the more light you gather (aka, the bigger the mirror), the brighter the image will be. So, how bright and how big is big enough? Let’s take a look at some practical considerations.

Questions to consider before making a final decision on scope size include: What do I most enjoy viewing? Do I observe more at, or away from, my home? How much weight can I comfortably lift? What eyepieces do I currently use? Can I locate deep sky objects by reading a map, or do I depend on computers to point me where I need to go? And finally, do I mind having lines of people waiting to look through my scope, or would I rather observe alone?

The Basics

If you’re a deep sky aficionado, then a big scope will reveal more detail on the faint fuzzies, period. A scope’s light gathering capability is determined by the size of its primary mirror in the case of reflecting telescopes, or its primary lens in the case of refracting telescopes. And you don’t have to double in size to double in light gathering capability. Remember, the area of a circle is π (pi) multiplied by the square of its radius (πr2). With that in mind, here’s a quick reference table of increased light gathering with a number of mirror sizes, each compared to a 4″ telescope:

Mirror Size
Increase in light gathering over a 4″ mirror
Limiting Magnitude*

*Limiting Magnitude – This estimate is based on good seeing, magnitude 6 skies, a 6mm dilated pupil, and 40x per inch of aperture. 40x per inch of aperture requires a well-figured primary mirror. For more information on limiting magnitude, see www.cruxis.com/scope/limitingmagnitude.htm

So, What Does That Mean At The Eyepiece?

The first step is to understand the above table, yet that alone doesn’t tell the whole story. Low contrast objects require not only dark skies and decent transparency, but also aperture. Think about M51, the Whirlpool Galaxy. Under dark skies and pristine conditions, an 8″ telescope will reveal a hint of the spiral arms with averted vision and high scrutiny. Through a 12″ under the same conditions, the arms are easy with direct vision. Through a 16″, knots in the arms can be made out. Through a 20″, the knots are much brighter and M51 begins to look like a black and white photo. Through a 24″, it’s possible to begin to make out faint coloring in the spiral arms, and the core of the galaxy is so bright, one wonders if it’s going to ruin their night vision!

Nebulae, globular clusters and any of the 109 Messier objects are perfect targets for large telescopes. I have found that a 12″ delivers color on the brightest of nebulae, and the color gets easier to see and more vibrant as the telescope size goes up. On globular clusters, an 8″ will resolve M13 and M3, while a 12″ will resolve most of the rest of the Messiers. With a 16″, all of the Messier globs are easily resolved, as well as many of the NGC’s. With a 20+”, you start loosing count of resolved globs!


Who can resist a peak at Saturn or Jupiter? Well, once again, aperture rules.

As a rule, as the primary mirror increases in size, the ability to discern detail increases. To fully recognize the potential of the large scope, a finely figured primary mirror is necessary. A great amount of discussion has occurred regarding smaller refractors and their reputation to outperform larger Newtonians. This mustn’t always be the case, however, and it would be a serious error to believe the superior view through a refractor is constant, impervious to variables in design, optics and weather. Those in the pro-refractor camp often claim their allegiance is due to the inherent design inferiority of a Newtonian. Nothing could be further from the truth.

A large mirror, such as is found in some Newtonians, must not only be properly supported from underneath, but also on its edge as it is being tilted within the telescope. Many a Newtonian builder neglects to provide the appropriate support. A consequence of an improperly designed mirror cell or edge support system will be any of several detail and contrast robbing aberrations, most notably different orders of spherical aberration and astigmatism.

An important aspect of large aperture Dobsonians (Dobs) is that the larger primary mirror requires far more time to cool down than a smaller refractor. Most of the older large Newtonians out there compound this because it was once thought that the mirror had to be relatively thick, otherwise aberrations would be introduced by the mirror cell (we now have finite computer analysis programs that will plot a perfect mirror cell of any size – most specifically David Lewis’ PLOP program). Thanks to the research of Bryan Greer (research article published in the May and June issue of Sky and Telescope) and others, we now have a better understanding of the ways larger optics shed heat. One of the more straightforward discoveries of this research was that the reason larger mirrors take so long to cool is mostly due to their thickness and not overall diameter. So if we choose the thinner mirror for faster cool down, we again shift our attention to the mirror cell. A thin mirror that is not supported properly from underneath will cause a slight deformation in the surface figure, which in turn causes light rays reflecting off the mirror’s surface to not come into focus at a single point. A star test would then readily reveal different orders of spherical aberration, degrading the view at the eyepiece. Now consider the mirror’s edge support. A sling is historically used to support the edge of large primary mirrors, often made out of Kevlar or metal banding. Through the work of Nils Olif Carlin (www.cruxis.com), we now understand that as much care should be given to choosing the proper edge support as goes into the design of the rest of the mirror cell. If this part of the mirror cell is neglected, you once again will experience different optical aberrations at the eyepiece as the telescope is moved from horizon to zenith.

Another point to consider is that bad atmospheric seeing can cause one to believe that a large telescope is performing poorly on the planets. It is true that a larger mirror will seemingly amplify poor seeing conditions, but patience at the eyepiece (waiting for the seeing to settle momentarily and for the planetary image to “pop”) will once again prove the larger mirror to outperform the smaller one.

So, let us review: A big telescope with a thin mirror, excellent mirror cell and edge support, built with an active cooling system (fans to provide air motion within the mirror box) and a night of good seeing – Viola! It’s a recipe for a night of planetary viewing that will leave you and other observers arguing about the spokes in Saturn’s rings!


I often hear of an amateur astronomer selling his scope because it’s just too much of a hassle to get out and observe with. The size and weight limit varies from astronomer to astronomer, so observers must carefully consider for themselves what may be too heavy or too much hassle to result in pleasurable observing.

An 8″ is usually considered the “biggest of the small”, while a 12″ is often referred to as the “smallest of the big.” I agree with this sentiment. An 8″ – 12″ tube-style Dobsonian is a one-person job and both easily fit in a mid-sized sedan, but the 12″ may push the weight limits of some. The 8″ scopes on the market today are around 65 lbs fully assembled, while the 12″ telescopes weigh in around 100 lbs. If you plan to use an equatorial mount, make sure to factor in an additional 30 lbs or so above the overall weight (and prepare to spend an extra 20 minutes or so setting up). Forget about 14″ – 20″ tube-style telescopes – portability is key and unless you have a small observatory, an equatorial mount is probably not feasible due to the sheer size and weight it encompasses.

Truss-style telescope weights vary significantly from vendor to vendor. One telescope I can be sure of knowing the weights of is one that I build, a New Moon Telescope. A fully assembled 16″ NMT is just under 100 lbs, the heaviest component you would lift weighing in at 60 lbs, and the collapsed scope readily fits in the same mid-sized sedan that would cart a smaller tube-style scope around. A 20″ is 134 lbs, the heaviest component weighing slightly over 80 lbs, and this is the size at which to start relying on detachable wheelbarrow handles to maneuver it. A 24″ would weigh roughly 165 lbs and a 27″ almost 200 lbs. When going this big, remember to reflect on what type of SUV, truck, or trailer you might like to own, because car-hauling is doubtful. Any of the scopes through a 20″ can be stored in a bedroom or living area (and the 8″ and 12″ even in a closet), fully assembled, should you choose to showcase them as pieces of furniture. From the 20″ and up, consider utilizing a storage shed, garage, or an observatory (should you be so fortunate!). Keep in mind, telescopes 20″ and larger necessitate a large car in which to travel, or ideally a truck, trailer or SUV, so if you’re an apartment dweller with no access to a storage unit, you’ll want to stick on the small side. Likewise, if you have your own observatory in your backyard, the sky is the limit on the size of scope you could choose, as portability will not be a factor.

Eyepiece Preference

One factor that may be overlooked when considering the purchase of a new telescope is the choice of eyepieces. The longer the overall focal length of the scope, the smaller the field of view (and so the higher the magnification), so the limited field of view of Plossl eyepieces quickly become frustrating when you start using telescopes in the 20″ range. Another factor about your eyepiece collection is the capability of the eyepiece for correcting coma. Coma is an aberration you get with any Newtonian, in which the stars in the eyepiece start looking like tadpoles as they near the edge of the field of view. Everyone seems to have a different tolerance level of coma, but there are ways to correct for it. The easiest – buy all high-end eyepieces. TeleVue, Pentax, Explore Scientific, and a few others are building eyepieces that contain coma-correcting elements (and of course FAR wider fields of view than the typical Plossl) and these usually perform well down to a focal ratio of F4.5. Faster than F4.5, you may need to invest in a specific coma-correcting eyepiece such as TeleVue’s Paracorr (I cannot recommend these enough). All of this being said, you could observe happily for the rest of your life with three high end eyepieces and a barlow lens with as large a telescope as you wish to endeavor (my opinion only of course!).

Further Considerations

Familiarity with the skies will also likely determine the size of the scope to purchase (or build, of course). The obvious determining factor here is cost. If you are brand new to astronomy and can’t tell the difference between Cygnus and Sagittarius, you should probably wait to invest in a $15,000.00 set-up, even if you can afford it now. A modest familiarity of the sky is needed when using any telescope, and wisdom has shown that beginners typically have an easier time with a simple pair of binoculars or a small telescope. In fact, many of the 8″ tube-style telescopes on the market right now are under $400, and perfect for a beginner. Purchasing a telescope like this will give you the time under the stars you need to learn the constellations and familiarize yourself with pointing, moving and using a telescope. If you are a more advanced amateur, however, bigger scopes and better optics start to make more sense. You have probably amassed a few decent eyepieces and know your way around the sky well enough to invest in a larger scope that will open the skies to you exponentially. Even if you aren’t a star hopping pro yet, there are digital encoders available and GOTO capabilities that can be added to even the largest of telescopes. Think of it this way: with a good NGC and IC map (or encoders), you could go to a dark site every night for the next 20 years and upon each visit discover a new deep sky object! And with some of the more obscure objects, you may be one of only a handful of people that have EVER seen said object through a telescope! And remember – the bigger the mirror, the brighter and more picturesque the object is going to look. And of course there’s always that chance of discovering a comet…

Finally, big scopes draw crowds, and crowds are the future of amateur astronomy. If you can point at a few nebulae, open clusters, or galaxies and give a 60 second presentation on what you are looking at, you will quite possibly change the lives and perspectives of countless people. So that’s my final “big scope” pitch: Big scopes change lives!

2013june25_ryangoodson_bioRyan Goodson is the owner of New Moon Telescopes (www.newmoontelescopes.com), manufacturer of custom Dobsonian telescopes. He is a member of several CNY astronomy clubs, hosts observing sessions from his dark skies in West Monroe, NY, and lectures regionally on telescope building. He can be reached at ryan@newmoontelescopes.com.