Archive for the ‘Books’ Category


Marking up sky atlases

February 4, 2017

I’m a book lover. Any space I’m in for long will have books on every available surface and piles of extras on the floor. Because of this love of books, for a long time I wouldn’t mark them up. This hands-off reverence extended to my sky atlases. But eventually I realized that sky atlases are tools, not heirloom pieces, and anything that makes them more useful when I’m observing is justified.


Here’s a representative page from my working copy of the Pocket Sky Atlas (I also have a second copy, autographed by John Dobson, that actually is an heirloom piece now). The circles and polygons flag objects from various Astronomical League observing projects. Triangles are double and multiple stars, rectangles are Herschel 400 objects, big circles are for the Binocular Deep Sky objects, and an open letter C designates Caldwell objects. I also drew in the position of Almach, which is just off the edge of this chart, wrote in the number for the multiple star 57 Persei, and wrote down the magnitudes of Algol and some of the useful reference stars, including Almach. Arrows in the margins are left over from my Caldwell tour.

I’ve finished all of those projects except the Herschel 400. You’ll see that some of the little rectangles have a diagonal slash across one corner – that’s how I flag which ones I’ve already observed. I’ve actually seen all of the H400s on this chart, I just got lazy about marking them off in the atlas. But I did write ‘CLEAR’ in the corner of the page so I know not to waste my time looking for unobserved H400s here. Other pages have the numbers of the H400s I still need written in the margins, for quick sorting and bookkeeping at the eyepiece.

These marks are very helpful while I am working on a project, because I have an instant visual reminder of what’s available to see in any given stretch of sky. And once I’m done with a particular project, the marks still point me to a lot of ‘best in class’ objects that I might otherwise overlook or forget.

Oh, I also sketch in the positions of comets from time to time, with the dates of observation.

This method has worked so well for me that I have thought about picking up extra copies of the PSA (for $13!) just so I could mark them up with objects from other observing projects. I’ve done that with a couple of my other atlases. My copy of the Cambridge Double Star Atlas has all of the AL Binocular Double Star targets marked, and I use my Jumbo PSA (which is ridiculously useful) to keep track of targets from the last several years of Sky & Telescope’s Binocular Highlight column, to help me avoid repeats. Of course I have other lists for all of these things, both physical and digital, but it’s nice to have an easy reminder when I am out observing or doing desk research.

Do you mark up your atlases? If so, what system do you use? Let me know in the comments.


Binocular Highlights: what I’m rolling with

July 23, 2016

I just turned in my sixth Binocular Highlight column for Sky & Telescope. While I had everything out for the write-up, I thought people might be interested to know what sources I make use of.

Here’s the stuff I use pretty much every time:

  • S&T’s Pocket Sky Atlas and Jumbo Pocket Sky Atlas. I usually take a full-size clipboard and Interstellarum out with me to observe, so the Jumbo version is no added hassle. Consequently – and perhaps counterintuitively – I tend to use the Jumbo version for nearby excursions, and the classic for desk reference and travel. This is usually my first stop.
  • interstellarum Deep Sky Atlas: Desk Edition. Despite the name, my primary ‘deep’ field atlas. Goes out with me practically every time, unless space is really at a premium. Also sees heavy use indoors for planning sessions and following up on things.
  • Chandler Night Sky planisphere. Hands down, my most-used tool – it goes out with me every session no matter what, and I frequently refer to it indoors as well.
  • Chandler Sky Atlas for Small Telescopes and Binoculars – particularly useful for the Milky-Way-centric chart that shows the galaxy as a flat band with the celestial coordinate grid deformed around it. Useful for thinking about where things are with respect to the disk of the galaxy, for quick looks, and for the object list.
  • SkySafari 5 Pro app on my iPhone. Astounding amount of information. Usually my first source for looking up distances, separations, etc., although I always confirm with some other source.

Sources I turn to often, but not always:

  • Glenn LeDrew’s atlas of the Milky Way in The Backyard Astronomer’s Guide, 3rd Edition. I already had the 2nd edition – it was one of the first books I picked up when I first got into amateur astronomy back in 2007. I got the 3rd edition primarily for the Milky Way atlas, and I was not disappointed. The identification of OB associations is particularly useful.
  • The Cambridge Double Star Atlas. Super helpful for checking on double stars, and a handsome and useful atlas all around. Also, kind of an insane steal at $22 on Amazon.
  • Burnham’s Celestial Handbook. Not my first stop for astrophysical data, but it’s nice to get some historical perspective and Burnham excels at this.
  • O’Meara Deep-Sky Companions series. Useful for astrophysical info, historical persepctive, and visual impressions from one of the world’s foremost observers. Crucially, O’Meara usually describes how objects look at varying magnifications, including naked eye and binocular appearances, so although the books are grounded in telescopic observations they are still quite useful for binocular observers.
  • Uranometria, All Sky Edition. Always nice to have the big gun in reserve, although I find Interstellarum more useful for most practical applications.

To get the latest astrophysical data I turn to the web. Particularly helpful sources are the SEDS Messier database, non-Messier NGC/IC/etc page, and Interactive NGC Catalog, the NGC/IC ProjectSIMBAD, the NASA Extragalactic Database, and if all else fails, Google Scholar and ArXiv.

For inspiration I’m quite omnivorous. Gary Seronik hit the Messiers pretty hard for the last few years, so I’m avoiding them for the time being, both to avoid duplication and to force myself to go find new stuff. The Astronomical League’s Deep Sky Binocular observing list (free), the Irish Federation of Astronomical Societies Binocular Certificate Handbook (free), James Mullaney’s Celestial Harvest, Phil Harrington’s Touring the Universe through Binoculars, and my own notes compiled over the past 8.5 years all serve as jumping-off points. Tom Price-Nicholson’s Binocular Stargazing Catalog (free) looks like a useful source as well, although I haven’t had a chance to explore it thoroughly yet. More often than not, I go out to find a particular object or to survey a set of objects (open clusters in Cygnus, for example) and end up discovering new things. So far I’ve been generating many more possible topics to write about than I actually can, so it seems unlikely that I’ll run out of subject matter anytime soon. We’ll see!

If you know of something I should be using that’s not on the list, please let me know – the comment field is open.


Great deals at Sky & Telescope today only!

November 30, 2014

Hey, just a heads up that among all the other Black Friday/Cyber Monday/whatever-we’re-calling-this-season-now discounts out there, the ShopAtSky store at the Sky & Telescope website has some screaming deals. If you use the promo code BLKFRIDAY, you get 30% off storewide and free US shipping. But the promotion ends tonight (Nov. 30), so get on it!

Caldwell Objects cover

Of personal interest to me is that they have new copies of Stephen James O’Meara’s Deep-Sky Companions: The Caldwell Objects. I like all of the Deep-Sky Companions series (see my review of Hidden Treasures here) and I’ve been collecting them one by one, but I didn’t have this one. It’s been out of print or at least hard to find for a while, and used copies have been going for upwards of $60 on Amazon. The book is normally$39.95 at ShopAtSky, currently discounted by 20% to $31.95, then discounted today by an additional 30% if you use the promo code, which brings it down to $22.something. I know some folks aren’t wild about the Caldwell list but there are a lot of great objects in it and if you like O’Meara’s writing, this book is a must-have. There may never be another chance to get new, hardcover copies of this book this cheap, so if you’re remotely interested, do the right thing.

Oh, and if you don’t already have Hidden Treasures, ShopAtSky has it for $19.95 before the 30% promo today, so you can get this book right now for under $15 and with free shipping. That is just astonishing.


An Astronomy Wish List for Beginning Stargazers

November 14, 2014

One of my main goals with this blog has always been to make amateur astronomy accessible to newcomers. So it’s probably past time that I post a list of the top 10 things I think a beginning stargazer needs. I’ve ranked them here roughly by my perception of how important or useful they are, especially for people just starting out. Almost everything on the list is something I’ve either owned or used myself, and the important exceptions are noted.


1. A Planisphere

Yes, you can get a free app for your phone that will show you thousands of celestial objects. If you get one with a good night-vision mode AND turn the brightness way down on your phone, it might not destroy your night vision, but it will still only show you a small slice of the sky at one time. At best, you’ll be outside under the stars and still looking at a dadgummed screen. Here’s a thought: put all the devices away, get out a lawn chair or just lie down on the grass, grab a planisphere, and spend a quiet half hour picking out the constellations. One of the chief advantages of a planisphere over an app is that you can see essentially the whole visible sky displayed at once, so you can figure out how the constellations relate to each other. Planispheres aren’t just for newbies, either – I know a lot of experienced observers, myself included, who keep one handy to do a quick check on what’s up, or will be up, at a given time. There are lots of planispheres on the market but I prefer the simplicity and utility of The Night Sky series by David Chandler, which come in different models for different latitudes. I suspect that most readers of this blog will want the 30-40 degree one (link) or the 40-50 degree one (link); if you’re outside that zone, search for one that matches your home latitude. Cheap alternative: print out the free Evening Sky Map for this month (here), which in addition to a star chart has lists of objects for naked eyes, binoculars, and telescopes.

Orion Redbeam flashlight

2. A Red Flashlight

Yep, I’m giving this the number two spot. Why? Because you’ll need one right away, and you’ll never stop needing one as long as you’re stargazing. For my first month as an amateur astronomer, all I had were a planisphere and a red flashlight, and I still had a lot of fun out under the stars. As with planispheres, there are lots of models available. I like this one from Orion (link) – it’s small enough to keep on you at all times and just bright enough to be useful (a lot of red-beam flashlights are too bright). Cheap alternative: get a regular flashlight and tape some red cellophane over the end, or even some brown wrapping paper or part of a paper bag. If it’s still too bright, do what I do and tape a coin over the bulb to block more than half of the light.

Nightwatch cover

3. Nightwatch

That’s right, not just any beginning astronomy book, but this particular one (link). Why? I wrote a whole post about that (here), but here’s the short version: no other single book covers so many aspects of amateur astronomy, from the kinds of celestial phenomena to naked-eye, binocular, and telescopic observing – and what kinds of binoculars and telescopes to consider buying. It even has star charts to get you started as an observer. The Backyard Astronomer’s Guide (link)treads similar ground, with more detail on the gear and how-to side at the expense of star charts or guidelines for finding specific objects. Cheap alternative: see if you can find a used copy, especially of one of the older editions (the current edition is the 4th) – some of the specific gear recommendations may be a little dated, but everything else will be just as useful.

4. Binoculars

I put binoculars ahead of a telescope for two reasons. First, if you’re on a tight budget, you can get decent binoculars for a lot less than you can get a decent telescope. Second, like the red flashlight, they’re something you’ll never outgrow. I am a committed binocular observer, but even if you’re not, binoculars can be a huge help at the telescope, mainly for finding your way around the sky before you attempt a star-hop in the ‘scope, but also for appreciated big extended objects like the Pleiades, the Hyades, the full extent of the Andromeda Galaxy, and so on. There are tons and tons of binoculars out there. Here are a couple of models that I own and use a lot, that I think are good values: for a general instrument, the Celestron UpClose 10x50s have decent optics and build quality and cost only $25-$30 (link). I spent one of my most rewarding nights of stargazing using only this instrument, a red flashlight, and a book I’m about to recommend (Gary Seronik’s Binocular Highlights) – here’s that observing report. If you’re really into binos and want to try some big guns, the Celestron SkyMaster 15x70s are a nice first step (link). They’re light enough that most folks can hand-hold them, but they’re easy enough to mount on a tripod if you’d like a steadier view. I use mine a LOT – I’ve seen almost all of the Messier objects with them, and probably close to 100 non-Messier NGCs and other deep-sky objects. Cheap alternative: whatever binoculars you already have lying around, or that you can pick up at a thrift store, or borrow from a friend. It was a view of Jupiter and its moons in the cheap 7x35s I’d had since high school that first got me hooked on stargazing. Any binoculars will be a useful and probably mind-blowing step beyond what your naked-eyes can show. That said, avoid binos with red-tinted “ruby” lenses if you can – they look and sound high-tech, but the tinting is pointless and crappy and only there to cover other optical faults.

Orion Starblast

5. A Decently-Sized, Solidly-Mounted Telescope

I imagine a lot of beginning stargazers must get frustrated when they ask what telescope to buy, and more experienced people keep saying, “Get a planisphere and some binoculars and learn the sky first.” We say that because you can get months or years out of enjoyment out of those things, for an outlay well under $50, whereas most of us would have a hard time recommending a telescope under $100 as a rewarding instrument. But if you’re here for scope recommendations, I have some.

A word about the qualifiers I put in the heading: by “decently-sized” I mean something with an aperture in the neighborhood of 4 inches (100mm) or larger. Yes, people can and do get a lot of enjoyment out of smaller telescopes, and some of us have a possibly unhealthy fascination with tiny telescopes. But if you’re just starting out, you need some early wins, and a 4- to 8-inch scope will make everything bigger and brighter. “Solidly-mounted” is crucial; on many objects rewarding magnification starts at 50-100x, and at those magnifications, every little shake in the scope or mount is going to be magnified 50 to 100 times. A shaky mount can make an otherwise decent telescope essentially unusable. I suspect that frustration with shaky mounts has probably killed more budding observing careers than any other single factor.

So what should you get? If you know you’re in for the long haul, follow the standard advice and get a 6- or 8-inch Dobsonian. I’m a big fan of the Orion XT6 (6 inches, ~$300) and XT8 (8 inches, ~$370), but Dobs are hard to screw up and you can’t really go wrong with any of them. If you’re less certain, or have less dough to throw around but still want a decent scope, get a smaller Dob or tabletop scope on a Dobsonian mount. Popular choices that don’t suck include the Orion SkyScanner 100 (4 inches, ~$125, observing reports here and here), Orion StarBlast 4.5 (4.5 inches, ~$200), Orion XT4.5 (4.5 inches, ~$260), and the Astronomers Without Borders OneSky (5 inches, ~$200, observing report here [as the Bushnell Ares 5 – same scope, different branding]). Personally, I’d avoid the Celestron FirstScope and Orion FunScope (3 inches, $35-70 depending on model and outlet), for reasons explained in this post. Cheap alternative: already covered – binoculars and a planisphere! Yes, you can probably find some rickety undermounted disaster on eBay or Craigslist for less, but it will almost certainly not be a good choice for a beginner. As a beginner you need something that Just Works, not a project scope. Wait to rescue one of those trash-heap darlings until you know what you’re doing.

Field Map of the Moon

6. A Moon Map

Depending on your tolerance for light pollution and willingness and ability to navigate when there are few visible stars in the sky, most other astronomical objects look less than stellar for at least one week each month, and maybe two, centered on the full moon. Also, the moon is one of the few objects that looks fantastic in almost any telescope. And you’ll enjoy looking at the moon more if you have some idea of what you’re looking at. Plus, moon maps are so cheap ($5-$12 for all of the models listed here) that there’s not much reason to pass on getting one. Sky & Tel have a couple of models available, their basic laminated moon map (regular, reversed) and the much nicer Field Map of the Moon (regular, reversed). As the links indicated, both are available in two versions, one showing the moon as it is in the sky, and the other with the moon reversed from left to right, to match the flipped orientation in most refractors and CATs. Cheap alternative: if not a moon map, how about a moon app? My favorite is Moon Globe by Midnight Martian. The basic app is free, and Moon Globe HD is a worthwhile upgrade for a couple of bucks. You can ignore my griping about apps wiping out your night vision, because the moon is bright enough most nights to wipe out your night vision all by itself. And for your computer, Virtual Moon Atlas is the reference standard (link); it’s been continuously updated for more than 10 years and is a very mature piece of software.

Turn Left at Orion

7. Books That Show You the Way

You can get a really good start with free resources like the Evening Sky Map and Stellarium (free planetarium software, get it here), but a lot of beginning stargazers find it helpful to have a book that not only tells you what to point the telescope at, but also tells you how to get there. Turn Left at Orion (link) is the standard recommendation here and indeed it will show you a lot; I own a copy and it was very helpful in carrying me along until I could fly for myself. A not-so-obvious choice that I also recommend a lot is Gary Seronik’s book Binocular Highlights (link) – almost every one of the 99 objects he shows you how to find in that book are dynamite targets for telescopes of all sizes, and the finder charts are very clear and well thought-out. Although I haven’t used it myself, Peter Birren’s Objects in the Heavens (link) is another popular choice–frequent commenter Doug Rennie calls it “the best observing guide out there”. If you’re a little more seasoned or just want more of a challenge, Sue French’s books Celestial Sampler (link) and Deep Sky Wonders (link) have zillions of things to find, organized by constellations or small areas of the sky, with targets appropriate for scopes of all sizes (Sue does most of her observing with a 4-inch refractor and a 10-inch reflector). Finally, the Deep Sky Companions series by Stephen James O’Meara is nicely organized and presented, with 109 objects per book plus a few bonus objects at the end; the individual titles are The Messier Objects (link), The Caldwell Objects (link), Hidden Treasures (link), The Secret Deep (link), and Southern Gems (link). Cheap alternative: a used copy of one of the above. Heck, used copies of the 2000 edition of Turn Left are currently going for a buck and a half on Amazon – observing guides don’t get much better or cheaper than that.

Pocket Sky Atlas

8. The Pocket Sky Atlas

Wait, if I just recommended books that will drive you to dozens or hundreds of objects in the sky, why do you need an atlas? Because no matter how nice the path that other authors have blazed for you, sooner or later you are going to want to step off it, and go wander in the wilds of the sky on your own. When you take that step, you’ll need an all-sky atlas.

Once again I’m skipping past a lot of other possible contenders to recommend a single book. There are lots of sky atlases out there, which cover a wide range of “depths” in terms of numbers of stars and objects shown. Some, like the Bright Star Atlas (link) and the Sky Atlas for Small Telescopes and Binoculars (link), simply show too few stars and objects to help you get on target with a telescope, although they are both fine binocular atlases. Others, like the Sky Atlas 2000.0 (link) and Uranometria (link), are overkill for a beginner – you’ll know when you need to move up to something like that. The Pocket Sky Atlas (link) hits a happy medium: for most of the hundreds of objects that beginners are likely to go after, it shows enough stars to get on target, but it’s still conveniently sized and intuitively laid out. The PSA has been my guide for the Messier objects, the Caldwells, the Astronomical League’s Deep Sky Binocular, Urban Observing, and Double Star observing programs, and the first 40% of the Herschel 400, and I’m still very far from exhausting the 1500 or so plotted deep-sky objects. (For the record, I also own the Bright Star Atlas, Sky Atlas for Small Telescopes and Binoculars, the Cambridge Double Star Atlas, and Uranometria, and I have used the Sky Atlas 2000.0; I recommend the PSA because it’s my most-used atlas, not my only one.). For a dissenting view and an alternative recommendation, see this post and its comment thread for a discussion of Eric Karkoschka’s Observer’s Sky Atlas (link). Cheap alternative: there are several nice sets of free, printable atlases that cover the entire the sky; these have the advantage that you can print only the pages that you need, and at the level of detail that is best for your equipment. My favorites are the Mag 7 Star Charts (link) and the TriAtlas (link); this last one is actually three atlases of varying sizes and levels of detail.

Seeing in the Dark

9. Books About the Why

Many books will tell you what’s in the sky and how and where to go find it, but only a few capture the “why” of stargazing. A lot of committed observers end up spending a considerable amount of time alone in the cold and the dark – what is it that keeps drawing us back out there? I am certain that there are almost as many sources of inspiration as their are stargazers, and what works for one may not work for the next. But this is my list and I have to recommend something. The two books that crystallize for me the wonder and romance of observing the night sky are Leslie Peltier’s Starlight Nights (link), and Timonthy Ferris’s Seeing in the Dark (link). The former goes in and out of print. Sadly it is out of print right now, and used copies are going for ruinous prices. Happily there is a Kindle edition that is not too steep. Seeing in the Dark is one of my favorite books of all time, and I wrote a whole post about it, which you can find here. Cheap alternative: used copies of Seeing in the Dark start at $0.01 plus shipping, so you’re not risking much by giving it a try.

Universe the definitive visual guide

10. An Almanac of What’s Up There

For cloudy nights and quick reference, it’s handy to have a book that just has tons of data. Say you want to find out how many moons in the solar system are bigger than Mercury*, or the orbital period of Neptune**, or the distance to the Orion Nebula***. Yes, you could just look all of that up on Wikipedia, but sometimes it’s faster and easier to use a book. Plus, everyone needs stocking stuffers, right? Now, there are shedloads of books that cover this ground, and if you have access to a Barnes & Noble or other large brick-and-mortar bookstore you can probably find any of half a dozen likely candidates on the bargain rack. I have a couple of favorites to recommend. First, the pocket-sized Smithsonian Handbook: Stars and Planets by Ian Ridpath (link) has a special place in my heart, because it was the first astronomy book I bought back in 2007 when I was first getting into the hobby. Although I couldn’t have known it at the time, I got lucky: the book has a simply amazing amount of information in a very compact package, and I’ve keep it close by ever since and referred to it often. If you want a big fat book to curl up with on a rainy evening, Universe: The Definitive Visual Guide is hard to beat (link). If there’s an important topic in astronomy that’s not covered, I don’t know what it might be. I wrote a whole post about this book, too – go check it out. Cheap alternative: A used copy of one of the above. Universe seems to be out of print now, but you can get new copies for under $20 and used copies for about a buck and a half, plus shipping.


Well, those are my top recommendations. If there’s something awesome that I missed, let me know down in the comments. And in the words of Cloudy Nights user gnowellsct, “May peace be upon your high end consumerism”.

– – – – – – – – – – – – – –

* Two: Ganymede (the largest moon of Jupiter, and the largest moon in the solar system) and Titan (the largest moon of Saturn).

** 164.9 Earth years.

*** Approximately 1344 light years.


Timothy Ferris on galaxies, the universe, and time

November 12, 2014
Abell 2744 from Hubble

Abell 2744, Pandora’s Galaxy Cluster, from the Hubble Frontier Fields. Click through and get lost for a while.

This passage has been lodged in my head since I first read it years ago, and it is still the best short explanation I’ve read for the scale of galaxies and the universe. From Seeing in the Dark, pages 253-254:

Were the Sun a grain of sand, Earth’s orbit would be an inch in radius, the solar system the size of a beach ball, and the nearest star another grain of sand four miles away. Yet even on that absurdly compressed scaled, the Milky Way galaxy would be a hundred thousand miles wide. Galaxies are so big that once you get up to their scale, the universe starts to take on an almost country-cottage intimacy. The larger galaxies in clusters like the Local Group, to which Andromeda and the Milky Way belong, typically lie only a couple of dozen galactic diameters apart from one another – comparable to dinner plates at the ends of a twenty-foot-long dining table. Add in the galaxies’ halos of stars, globular clusters, associated hydrogen clouds, and dark outer disks, and they almost impinge on each other. On the same scale, the Virgo supercluster, of which the Local Group is an outlying member, comprises ten thousand plates scattered across an area not much larger than a football stadium, and the entire observable universe has a radius of only about twenty miles. From a galaxy’s point of view, the universe isn’t all that large.


The Andromeda Galaxy in ultraviolet light, from NASA’s Galaxy Evolution Explorer. You want to click through for the full image – trust me.

The trouble is that it’s difficult – probably impossible – for a human to make the mental leap to galactic scale. The very concept of space is inadequate for dealing with galaxies; one must invoke time as well. The Andromeda galaxy is steeply inclined to our line of sight, only fifteen degrees from edge-on. Since the visible part of its disk is roughly one hundred thousand light years in diameter, the starlight reaching our eyes from its more distant side is about one hundred thousand years older than the light we simultaneously see coming from the near side. When the starlight from the far side of Andromeda started its journey, Homo habilis, the first true humans, did not yet exist. By the time the near-side light started out, they did. So within that single field of view lies a swath of time that brackets our ancestors’ origins – and that, like the incomplete dates in a biographical sketch of a living person (1944-?), inevitably raises the question of our destiny as a species. When the light leaving Andromeda tonight reaches Earth, 2.25 million years from now, who will be here to observe it? We think of Einstein’s spacetime as an abstraction, but to observe a galaxy is to sense its physical reality.

Andromeda galaxy by Isaac Robers 1899

Andromeda as photographed by Isaac Roberts in 1899 (borrowed from Wikipedia)

…As objects of study, galaxies are bottomless. If we spent eons observing the Andromeda galaxy with ever better equipment, we would, presumably, learn a great deal – indeed, one hopes that this will happen – but there would always be more to learn, if only because so many things keep changing there. To pick a literally glaring example, it is estimated that more than fifty thousand stars have exploded in Andromeda in the past two million years: The light from all those supernovae is already hurtling through space toward our telescopes, part of Andromeda’s past and our future. A galaxy is not so much a thing as it is a grand, glorious exemplification of the scope of cosmic space and time.


Ken Fulton on refractors

October 24, 2013

If I’m succumbing to refractoritis, I’ve at least had some help getting there. David DeLano and Terry Nakazono have let me look through their big beautiful lens-based scopes. Darrell Spencer posted about the crisp views through his huge refractors on CN. And Doug Rennie sent me this back in August. It’s an excerpt from Ken Fulton’s under-appreciated book, The Light-Hearted Astronomer.

Read it at your peril.

Ken Fulton - Light Hearted Astronomer - excerpt on refractors


Gear reports: Explore Scientific eyepieces, Orion Apex 127 Mak, Celestron Travel Scope 70

July 16, 2012

Apex 127 (left) and Travel Scope 70 (right) under dark skies on Mount Baldy. The Apex is on a SkyWatcher AZ4 mount, and the TS70 is on a Manfrotto CXPRO4 with a Universal Astronomics DwarfStar alt-az head. Photo by Terry Nakazono.

As promised in the last post, here are my thoughts on the scopes and charts I used up on Mount Baldy Saturday night. I haven’t had half of this stuff long enough for these to be considered true reviews, so I’m calling them “gear reports”.

Explore Scientific eyepieces–For  a long time my workhorse eyepieces have been 32mm and 12mm Plossls and the 6mm Expanse. The 24mm ES68 gives the same true field as the 32mm Plossl but with higher magnification and a larger apparent field–68 degrees versus 52. The 14mm and 8.8mm ES82s give me a nice pair of mid-to-high power options, without taking business away from the 6mm Expanse.

How important is all that apparent field of view? I’ve also had the opportunity recently to look through a few TeleVue Ethos 100-degree eyepieces, and here are my impressions.

  • Ethos: I could not quite see all of the field of view at once. I had to actually move my head around to see the field stop. It was nice–when I first looked in the eyepiece, at what was in the middle of the field, I could not immediately see the field stop in any direction. It actually was like looking through a window into space. I can see why people shell out big bucks for this experience (think $600 and up for the TeleVue Ethos models and $400 and up for the other brands).
  • ES82: I can see all of the field and the field stop at once, but it is so far out to the edge of my field of view that I am not really aware of it. Very comfortable, too, in terms of eye placement and eye relief.
  • ES68 and Orion Expanse (66-degree apparent field): ditto. For me, the jump from 52 degrees to 66 or 68 degrees is much more noticeable than the jump from the sixties up to 82–or back. I never went from one of the 82s to one of the sixties and thought, “oh, hey, where did my extra field go?”, which definitely does happen when I go directly from a widefield to a Plossl. My only explanation is that, at least for me, 66-68 degrees is over a threshold where additional apparent field makes little difference, until the I-can’t-see-it-all-at-once threshold I get with the Ethos.
  • Plossls (52-degree apparent field): I like Plossls. They’re good, solid workhorse eyepieces, that can handle a wide range of focal ratios and tend to be sharp and have good light throughput. They were my go-to eyepieces for years. But, like many, many stargazers before me, I am spoiled now. The fact is, after using 66-82 degree eyepieces (I’ve had a pair of 68-degree Orion Stratuses for a couple of years, and just not used them much), going back to the Plossls is like being struck with tunnel vision: I am acutely aware that a lot of my visual real estate is occupied by non-sky inside-of-eyepiece black nothingness. That said, the effect really only jumps out at me when I swap a widefield for a Plossl back to back in the same scope. Saturday night I would be observing with widefields in the Apex and then wander over to the TS70 with the 32mm Plossl and not notice the sudden decrease in field. So I’m not getting rid of my Plossls anytime soon. For one thing, they all weigh much less than their widefield counterparts, and so play better in small scopes and travel kits.

By the way, if you’re in the market for budget Plossls and Expanse clones, check out the Black Knight Super Plossls and Enhanced Super-Wides at OWL Astronomy.

Apex 127–Under dark skies, a potent deep-sky instrument. Its maximum true field of just a bit over a degree will frame almost all deep sky objects, except for the very closest open clusters (like the Pleiades and Hyades). Everything I tried for, I found–my problems with the two open clusters were not that I could not see them, but that I could tell exactly what parts of the rich Milky Way starfields were supposed to be the clusters–more on this farther down. It’s also a planet-killer and excellent double-star scope. One night this spring I was trying to split a particularly tough double with this scope. It refused to budge at 257x, so I Barlowed my 6mm expanse to give 514x, and finally saw that stripe of black sky between the two stars. That’s about 100x per inch of aperture, or twice the rule-of-thumb “maximum effective magnification” of 50x per inch. Which means it’s a damn fine scope.

Travel Scope 70–Four things about this scope, three good, and one not so good. The good stuff first.

  • It costs next to nothing. As I’ve pointed out in other posts, you can’t buy a 9×50 right-angle correct-image finder for what they’re charging for this scope.
  • It’s small and light. I think it would ride on the same tripod as my SV50 and the scope itself takes up hardly any more room, but 70mm gathers roughly twice as much light as 50mm (5*5=25, 7*7=49). It has the same focal length as the venerable Short Tube 80 but weighs about half as much. You could think of it as a Short Tube 70, but its focal ratio of 5.7 is a hair more forgiving. That combined with the slightly smaller aperture should knock down the chromatic aberration a bit, compared to the ST80, and indeed I’ve found the CA unnoticeable in casual use, even on the moon and  planets (that is, I’m sure it’s there if one goes hunting, but it’s never risen to the level of attracting my attention at the eyepiece).
  • The optics are wonderfully clear. The low-power views are really bright and contrasty. I noticed this the first night I had the scope. I was cruising the summer Milky Way from my driveway, trying the 12.5x view with the 32mm Plossl for the first time. Now, Lyra was dead overhead, and atmospheric problems are almost always minimized at the zenith, but still, the view was bright, and I found the Ring Nebula, M57, right away. I thought “No way, there’s just no way the Ring is that easy at 12.5x. Must be an out-of-focus star.” So I started working my way up in magnification, and sure enough, it was the Ring after all. I noticed the same thing again Saturday night. I couldn’t see much detail on most of the Messier objects at that magnification, but they just jumped out of the background starfields, even the smaller ones. If you like low-power scanning, this scope is a blast under dark skies and still a fun ride even under so-so skies.

Now, the not-so-hot:

  • It’s hard to push the magnification, and I don’t like the result when I do. A 12mm eyepiece gives 128x in the Apex 127, 108x in the 90mm Mak, and 100x in the XT10, but only 33x in this  scope. A 6mm eyepiece gets you to 67x, but it ain’t worf it. The scope starts to pant around 40x and anything north of 60x is just bad. I noticed this the first night out, looking at Saturn and the moon, and it was still true this weekend. I don’t know if its astigmatism or poor collimation or what, but trying to achieve focus on planets is maddening. Jupiter goes from a vertical fan of red light on one side of focus to a horizontal fan of blue light on the other, and only sort of flirts with being a clean disk in between those extremes, at an infinitesimally tiny point that the rack-and-pinion focuser tends to shoot right past. It’s actually really puzzling to me that a scope that gives such clear, contrasty images at low power goes to crap so fast as the magnification goes up. (In case you’re wondering, we used exclusively low-power eyepieces with this scope for the Venus transit.)

So in the end the TS70 is kind of a one-trick pony. It is awesome for scanning around at low power and surfing the Milky Way. That’s the one thing it can do that neither of my Maks can. But unless you get a much better sample than I did, forget about doing any serious work at even moderate magnifications. The 90mm Mak is a much more versatile tool–it can do almost everything except widefield scanning. So at least the two small scopes complement each other.

UPDATE: the TS70 performs MUCH better after having been disassembled and reassembled (details in this post). It’s not hard, all it takes is a screwdriver. Blackening the lens edges with a Sharpie improves the scope’s already decent contrast, and shaking the lens cell a little while the objective lenses are loose will improve the collimation. After doing only that, I can now take this scope up to at least 133x without the image falling apart. It’s like a whole new scope. That said, there are still better choices out there – see my astronomy wish-list for beginning stargazers for some suggestions.

Actually the awesome low-power views of the TS70 have inspired me. A small ED refractor like the Astro-Tech AT72ED ought to give equally good low-power views and be able to take magnification well, and could potentially put both the TS70 and the 90mm Mak out of business. I don’t know if it actually will, but I aim to find out. So I think one of those will be my next big astro purchase–once I save up for it.

In the meantime, since the TS70 performs like a superfinder anyway, I’m going to keep scheming on how to turn it into one. I’d love to have it mounted side-by-side with the Apex 127, so I’d have a rich-field scope and a planet-killer on the same mount.

Pocket Sky Atlas–Since I started out in astronomy, the PSA has been essentially the only atlas I’ve used. It has stars down to magnitude 7.6 and about 1600 deep-sky objects. That includes all the Messiers, all the Caldwells, and all the Herschel 400s, plus another thousand or so, so it’s covered my needs and then some. The only time I’ve printed up my own finder charts has been for hunting quasars. I haven’t felt the need to move up to a “deeper” atlas until very recently.

I started thinking about a deeper atlas after observing with Terry Nakazono last month. His most-used atlas is the Observer’s Sky Atlas, which covers the whole sky to mag 6 but also has enlarged charts to mag 9 for finding 250 deep sky objects, including all the Messiers. He also prints out detailed finder charts from the Tri-Atlas (a huge free atlas in three versions: mag 9, 11, and 13). He was surprised that I’ve gotten along as well as I have with just the PSA.

Part of the difference in preference probably has to do with the instruments that we use and how we get on target. Terry’s most-used scope is the SkyScanner 100, which has a red-dot finder. So he gets in the neighborhood–or closer, sometimes you can really bullseye things with an RDF–with the dot finder and then star-hops to his targets at the eyepiece. In contrast, I use a 9×50 RACI finder on whatever scope I am observing with (I only have one, and just move it around among scopes), and do almost all of my star-hopping with the finder alone. The 50mm finder does not go nearly as deep as the 100mm reflector–it simply shows fewer stars–so I often use the geometrical method of centering the finder on an unseen target (this is detailed by Harvard Pennington in The Year-Round Messier Marathon Field Guide and by Stephen Saber in his post on “sharpshooting” deep-sky objects–search for it here). I hadn’t given this much thought before Terry brought it up, but my less-deep atlas suits my finder-driven navigation, whereas eyepiece starhopping really requires that you be able to see as many charted stars as possible to keep from getting lost. So we have each gravitated toward the atlas that best suits our observing style–or rather, I started with PSA and never had a reason to gravitate away.

Until now, that is. The problem is not that the PSA doesn’t show enough deep-sky objects. I’ve only seen about a fifth of its 1600 plotted DSOs. The problem, as Terry pointed out, is that it just doesn’t show enough stars, at least for some problems. In trying to track down some of those small open clusters in Cygnus and Cassiopeia, I found that the plotted symbol in the PSA covered a good-sized field that was striped and mottled with star chains and asterisms of the summer Milky Way. The geometrical relationships shown in the PSA just weren’t enough. I couldn’t go to “the” cluster of stars that made an equilateral triangle (or whatever) with the nearest guide stars, because there half a dozen plausible candidates (actually, this might be a not-enough-DSOs plotted problem as well as a not-enough-stars problem). I need to see some of the fainter stars in between plotted on the chart, to break up those rich starfields into manageable–and interpretable–chunks.

So, to make a long story short, I ordered the first volume of Uranometria 2000.0, a mag 9 atlas, and I’ll get the other two volumes as funds allow. Stay tuned.