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INTERSTELLARUM DEEP-SKY ATLAS (FIELD EDITION) REVIEW
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INTERSTELLARUM DEEP-SKY ATLAS (FIELD EDITION) REVIEW
interstellarum Deep Sky Atlas (Field Edition)
Ronald Stoyan and Stephan Schurig, authors
Published by Oculum-Verlag; English-language editions produced and distributed by Cambridge University Press
The author is an Oregon-based deep-sky observer with three decades' experience at the eyepiece and a semi-Luddite approach to observing—wires make him very, very nervous. He has no connections to the authors or publisher of the work under review.
Unlike many CloudyNights members, it seems, I’m not normally one to embrace new technology—I own five telescopes, ranging from a 12.5" Dobsonian to a 70mm achromat—but my use of electricity in the field is usually limited to anti-dew devices. More recently, I’ve started using an iPad in the field, but even that is in a low-tech manner; I generally use only the Tri-Atlas app for astronomy, which is basically a paper atlas on-screen. (I have Stellarium and Sky Safari, but haven’t really used them yet at the eyepiece.)
Since 1988, my main atlas in the field has been Tirion’s deluxe Sky Atlas 2000.0. With the first edition, I completed the Messier catalogue and stepped out into the NGC (mostly planetary nebulae and globular clusters) from my horribly light-polluted Cincinnati suburb. Sky Atlas 2000.0 is of a decent size and scale, is easy to take and keep scope-side, had the right amount of detail for the scope I had at the time (an 8-inch SCT), and still worked well when I went up an aperture level. With the second edition, I completed the AL’s globular cluster program and began pushing the envelope of what I could find with my 12.5” Dobsonian from a Bortle green zone, moving into Hickson groups and Arp galaxies. I’ve used a copy at my scope for almost 30 years.
I also own both editions of Uranometria 2000.0; the first edition occasionally ventures out into the field with me, and has an ideal depth in terms of deep-sky objects. The second edition of U2000.0stays at home, as it seems almost sacrilegious to take it out into 90% humidity night after night. It’s a beautiful piece of work. It has one major drawback for me, though—it has thousands of non-NGC galaxies (many of which are within range of my scope), but almost nothing to distinguish them from brighter galaxies. On its own, this wouldn’t be a huge flaw, but in the field, with only a very dim red light to read by, it would be a hassle to weed through the tiny labels and symbols if I decided to take a side trip from a previously-selected object. Ideally, the brighter objects (mainly the galaxies) inU2000.0 would’ve had some way of indicating which objects are more obvious in the eyepiece and which were barely detectable.
Enter Ronald Stoyan and Stephan Schurig’s interstellarum Deep-Sky Atlas [hereafter iDSA]. Originally only a German-language edition published by Oculum, the iDSA was picked up by Cambridge University Press and translated into English. Available as a paper Desk edition or a waterproof Field edition, the English version of the iDSA was released by Cambridge in late 2014. Designed specifically as an observer’s atlas, the iDSA covers the middle ground between Sky Atlas 2000.0 and U2000.0, adding a host of observer-friendly features, solving a few issues other atlases have, and staking a claim as possibly the last great print atlas.
The iDSA consists of 114 double-page charts, organized by declination. The charts measure 10.2” x 11.0” (26 x 28 cm) per page, covering the sky at a scale of 1.5 cm per square degree. Each of the double-page charts covers two hours of right ascension and 15 degrees of declination. The center-point of each chart is indicated on the charts’ edges, and each strip of declination is identified on the edges of the pages for easy indexing in the field. There are six index charts (one for each celestial pole and four seasonal indexes) toward the beginning of the atlas. In addition, crowded fields of sky are shown on 29 detailed charts of varying scale; these are indicated on the main charts themselves (although the detail charts don't indicate on which "main" chart they can be found—this would have been useful). These detail charts are arranged at the end of the atlas, after the main charts; a grey strip running along the length of the detail-chart pages allows for them to be flipped to fairly easily under red light.
At the back of the atlas is a 15-page index of all deep-sky objects contained within the atlas itself. These are organized by object class. This is fine if you know the class of an object, but might be problematic if you don’t know anything about an object beyond a catalogue number. (Adding a general index would, of course, add another fifteen pages to the index, which would probably be impractical.)
The atlas is housed in a black polypropylene cover with silver lettering; it’s a classy-looking package, and comes housed in a cardboard slipcase. The slipcase isn’t waterproof, but is sturdy enough to transport the iDSA. Pages are spiral-bound with a coated wire. I’d be concerned about preventing rust here, as it might bleed onto the pages should the wire get damaged and wet (one CloudyNights user has reported that the wire binding broke in his copy of the atlas). A polypropylene card containing the atlas legend is included in a clear plastic pocket in the inside cover of the atlas; my atlas came with the side of the pocket torn by shifting of the card during transit. The legend card is a nice feature, but sits loosely in the pocket—be careful that it doesn’t fall out unnoticed while using the atlas.
One of the notable features of the iDSA Field Edition is that it’s not printed on standard paper; it’s printed on a matte-finished plastic paper-like material (Polyart) that is ostensibly completely waterproof (the atlas’ webpage mentions that the iDSA is perfectly unharmed by dunking in an aquarium; given one CNer’s experience [see below], I’m not likely to test this). The iDSA website refers to this material as a plastic “foil.” It has a kimdura-like finish and feel.
The “foil” material can indent slightly with a fingernail but is fairly tear-resistant (I didn’t try too hard to rip it, but exerted enough pressure to tear regular paper easily). My copy had a few pages with small wrinkles in them from (I suspect) being run through the printing press. These wrinkles had a minimal impact on the atlas’ usability and only a very minor impact on it aesthetically, although they really shouldn’t be there at all. The matte finish of the material makes it a bit of an issue to get the pages all jogged up evenly so that the atlas can fit into the slipcase. I also found the pages to be slightly tricky to grip and turn with cold fingers.
My copy of the iDSA has a printing issue: some of the star symbols (and a few of the constellation lines) got an extra-heavy ink load, and soaked through the page slightly.
Images from charts 67 and 68. On the left, Chart 67 shows extra-heavy ink coverage on the stars Nu Scorpii, Beta Scorpii, and Sherbourne 213; this can be seen in the image as high reflectivity of the star symbols under a light held at the correct angle. (The star symbols appear black and normal when viewed directly.) On the right, Chart 68 shows where the ink bled through the page from Chart 67; ghost images of Nu Scorpii, Beta Scorpii, and Sherbourne 213 can be seen.
This is a problem, but not one for which I was willing to return the atlas overseas (it was shipped from England). However, had it been more widespread or distracting, I would certainly have returned it.
The charts run straight to the edges of the pages; there are no gutters here. The makers of the atlas did this to maximize the amount of overlap among the charts. To me, however, it makes the atlas look slightly unfinished, with printing running straight up to the holes through which the spiral binding runs and to the edges of the pages, with labels and symbols cut off abruptly. I’d have preferred a border or gutter around each page, simply for aesthetic reasons.
So what’s actually in the iDSA? Well, it’s a substantial step up, deep-sky content-wise, from Sky Atlas 2000.0. The iDSA plots and labels the following deep-sky objects:
(Object-class breakdowns were unavailable for Sky Atlas 2000.0.)
Stars are shown to magnitude 9.5. In theory, this should be deep enough, but in practice it isn’t enough for detailed star-hopping. It’s a difficult trade-off: increasing the magnitude depth would’ve made the atlas even more useful, but it also would’ve made the charts more cluttered with stars. (By comparison, U2000.0 goes to magnitude 9.75 and adds over a third more stars… and even it isn’t quite enough for detailed star-hopping.)
A number of less-known deep-sky object catalogues are represented. The iDSA especially shines on open clusters, including the complete Basel, Bochum, King, Stock, Tombaugh, and Trumpler catalogues, as well as a number of even more-obscure targets. Among globular clusters, all of the Terzan and Palomar globulars are included, along with Whiting 1, the Koposov clusters, an obscure cluster in Pegasus (Balbinot 1), and the recently-discovered globular cluster in Crater (which may eventually turn out to be something other than a globular). Clusters of both types are labeled in yellow, using the same symbols as in Tirion. Asterisms are a nice addition to the atlas, and one that no other major atlas plots in such quantity; they’re marked here with a dotted circle, which at first glance is a bit difficult to differentiate from the open-cluster and galaxy-cluster (q.v.) symbols.
Diffuse nebulae are plotted with their visible extents marked, rather than what is extrapolated from photographs. This is apparent in comparing the outlines of Simeis 147 (in Taurus) from the iDSAand the Jumbo Pocket Sky Atlas:
Simeis 147 as rendered in the iDSA (left) and the Jumbo Pocket Sky Atlas (right). Note that the print quality of both atlases is much higher than indicated by these low-quality scans.
This is particularly helpful, as it provides a better representation of what may reasonably be seen in the eyepiece. Additionally, nebulae are labeled on the chart with a small box indicating which type of filter may be of greatest use on each nebula. I compared those filter recommendations in the iDSA with those of CN’s David Knisely, a respected filter guru; of 55 nebulae, the iDSA disagreed with Knisely only nine times, with only two of these disagreements being instances where Knisely referred to the iDSA’s recommended filter as being “not recommended.”  (In five instances, the iDSAlisted a given nebula as a reflection nebula and offered no filter recommendation, whereas Knisely did recommend a filter, due to the nebulae being a combination of emission and reflection types.) Diffuse nebulae are colored red here, rather than green, as is often the case; reflection nebulae are marked in blue. (It’s nice to see an atlas that indicates the distinction on the page.) Dark nebulae—including the entire Barnard catalogue—are plotted here also, in dotted outlines filled with black or grey [see below].
Planetary nebulae are plotted in green, including the entire Abell catalogue. It’s nice to see an atlas that uses labels other than the outdated PK or the current PN designations, as these are less commonly used by amateurs. One of my gripes with Uranometria was that the PK numbers were used on the charts in the 1st Edition, so that finding a planetary by an alternate name required using the Deep Sky Field Guide—then, when they issued the 2nd Edition of Uranometria, they used the PN numbers, relegating the PK numbers to the “Alternate Names” column in DSFG and ignoring the other catalogue names entirely; if you wanted to find Jones-Emberson 1 and didn’t know the PK number, you had to use the 1st and 2nd Edition DSFG to find JE-1 in the 2nd Edition Uranometria. TheiDSA wisely circumvents this.
Galaxies, like reflection nebulae, are drawn in blue. The entirety of the Arp and Holmberg catalogues, as well as those objects that are members of the Local Group, are plotted in the iDSA. Also included are all Hickson groups and a few of the Shakhbazian and Klemola groups, as well as all Abell galaxy clusters with members brighter than 13th magnitude. (Oddly, NGC 3290 is charted separately from Arp 53, when in fact the two are one and the same.)
Double and variable stars are plotted with standard symbols. Tick marks indicate separation distances, magnitude differences, and position angles in double or multiple stars. Many doubles are marked with their Struve/Otto Struve numbers, unlike in the Tirion atlases. All of the doubles in the Astronomical League’s Double Star observing program are included in the iDSA (although N Hydrae isn't identified as such; it's labeled as 17 [Crateris] and Hill 96 instead), although this is likely a coincidence. Variable stars are marked with circles and dot sizes indicating their maxima and minima. Carbon stars are not labeled or given a symbol as such; this is an unfortunate omission. 52 of the 100 stars on the Astronomical League’s Carbon Star Observing Program are nonetheless included among the variables plotted in the iDSA. It should be noted that while the Pocket Sky Atlas specifically labels carbon stars, it only does so with 55 of them—not much more than the iDSA, although the latter doesn't assign them a special symbol.
Stars with exoplanets—those discovered before April 2013—are labeled with an oval drawn around the star symbol. Indicating stars with exoplanets is curious for an atlas with a visual emphasis, as exoplanets aren’t exactly a visual target for amateurs. While it’s certainly of astrophysical interest—and the iDSA is the first atlas I know of to indicate exoplanet-bearing stars—I’d have preferred to have carbon stars marked instead, as it would be of greater observing interest.
The use of nicknames for deep-sky objects is a bit problematic. Sure, there are the common ones (Lagoon, Trifid, Swan, Dumbbell, etc.), but there are also a number of less-accepted or unfamiliar ones that add clutter to the charts (Patrick Starfish, the Condom Nebula)—perhaps these are used more in Europe, where the iDSA was first created and marketed. (In one instance, the nickname “The X-Rated Galaxy” is ascribed to the wrong object—NGC 5557, instead of the NGC 5544/45 pairing that usually gets the nickname. Do yourself a favor and DON’T do a Google Search for "X-Rated Galaxy.") I understand that nicknames can’t achieve common status without being used repeatedly, but some of these probably shouldn’t be used in an atlas that will outlive the references. There’s also at least one typo among the nicknames, as NGC 4627—The Cub or The Pup—is referred to as “The Club.”
Unlike the Tirion atlases, the iDSA draws lines to outline the figures of the constellations. This might also be problematic for some users, who adhere to certain constellation outlines; a glance through the index charts, though, shows that the iDSA uses constellation figures that are pretty recognizable, if not entirely universal. A few constellations—eg. Puppis, Pisces Austrinus—are a bit unusual at first glance, but there’s nothing here that’s totally unreasonable as a constellation figure.
One element that’s missing from the iDSA that’s present in Sky Atlas 2000.0 is Milky Way isophotes, marking the extent and density of the Milky Way as seen in the sky. This isn’t a major drawback, although I’m sure a number of users will wish they were present in the iDSA. As the iDSA uses red, green, yellow, blue, and black/grey for deep-sky objects, it’s hard to envision how the isophotes could have been represented anyway, without making the charts confusing or hard to read. (I somehow don’t think purple or orange isophotes would have cut it.)
The main innovation of the iDSA is the manner in which it denotes an object’s visibility. Using an extensive list of observations—the basis for the Eye & Telescope software, on which the iDSA itself is based—the authors have sorted all of the deep-sky objects in the iDSA into four visibility classes: objects visible in 4-, 8-, and 12-inch telescopes, and a selection of targets for telescopes larger than 12 inches. Visibility is indicated by the font size and weight of the object’s label, the line weight of the object’s symbol, and the density of the color used in the symbol. (The legend card inside the front cover can be used as a reference, if needed.) This system is intuitive enough that it quickly becomes second nature, although the symbols for asterisms, star clouds, groups/clusters of galaxies, and open clusters in the 12”+ class can be rather easily confused at first (and sometimes second) glance. Objects' visibility was determined by the authors using skies of 6.5 NELM and/or SQM 21.3 mag/arcsec^2 as a benchmark.
Some reviews of the iDSA have criticized these visibility classes as being a gimmick, or as something useful only to beginners. Both criticisms are unwarranted, implying as they do that needing such information in the field is a sign of inexperience, poor research, or a lack of observing skill. Yes, the visibility classes would be helpful for beginning observers (although they're less likely to shell out $200 for their first star atlas). In many instances, though, a spontaneous observing session is either a necessity or a pleasant change from routine for a seasoned observer, and knowing which objects might be suitable targets for a given scope simply by looking at the chart can make such spontaneity productive, efficient, and enjoyable. And for those who work from an observing list, it can be helpful to see at a glance what potential targets might lie within a few degrees of a recently-found object.
In assigning objects to their visibility classes, the authors have opened themselves up to a great deal of nitpicking and second-guessing, but their methodology seems to have paid off, judging from the initial reviews and comments from users. Not everyone is going to agree on the visibility of every object, given the variables involved. Stoyan and Schurig should nonetheless be commended for bringing a new level of usefulness to the millennia-old science of uranography.
In the field
With all this buildup, how does the iDSA actually work in the field?
Initial concerns about the use of red light with the iDSA's color coding are pretty much for naught. All of the object symbols are readable in red light; emission nebulae (printed red in the atlas) and open and globular clusters (yellow) turn varying shades of light orange, while galaxies, reflection nebulae, and planetary nebulae (blue, blue, and green, respectively) are varying shades of blue when lit by red light. If you depend on the color coding to determine object types in the field, you might be somewhat less happy with the colors printed here, but between the colors and the symbols, there shouldn't be any confusion. The iDSA loses none of its usability when read by red .
The atlas definitely works better laying flat than being held at the eyepiece. The spine of the atlas is creased so that it can be folded back on itself, but I found it a bit awkward to comfortably hold that way. It's not impossible, but certainly not as easy as with, say, Erich Karkoschka's Observer's Sky Atlas, Peter Birren's Objects in the Heavens, or the ubiquitous Pocket Sky Atlas (even the new Jumbo version), all of which are smaller, lighter books. CloudyNights user Carol L recommends putting the iDSA on a music stand, which is an excellent idea.
Some commenters have indicated that they found the fonts used for right ascension and declination (if not those used for object labels themselves) to be too small for easy reading in the field. While this wasn't my experience, I can certainly see how it would be for many observers. Very small type is appropriate for the faintest objects in the atlas, but less so for important general information. Future editions of the iDSA might do well to take this into account.
The visibility classes seemed to be fairly consistent with my own experience under similar skies to those of the authors, at least in the 8" and 12" classes. I did find the visible extents of some of the nebulae to be a bit ambitious as drawn in the atlas, but this certainly requires more testing than I was able to give it. I've had the atlas for nearly a year as of this writing, but have only had a couple of chances to use it in the field (2015 was a miserable year for observing!). In working through some crowded galaxy fields (e.g. Abell 347 in Andromeda), though, I found the iDSA's symbology to be pretty much on the money with what I observed under average conditions.
In some crowded fields, it can be difficult to discern which label goes with which symbol, as in the case of the NGC 2462 group in Lynx:
The field of NGC 2462 as seen in the iDSA (Chart 17). Note that the print quality of the atlas is much higher than indicated by this low-quality scan.
The trade-off here is between keeping the labels directly next to their object symbol or working around the star symbols in the area. Indicator lines could have connected labels with their corresponding symbols, but these, too, could contribute to crowding and clutter. I'm not sure there's a compromise that will appease a majority of users.
One criticism of Uranometria 2000.0 is that, while it has an exceptional amount of depth with regard to deep-sky objects, it lacks sufficient stars for star-hopping. The same is true with the iDSA: it's certainly fine for using patterns and geometric figures to close in on a target, but there simply aren't enough stars for star-hopping from an eyepiece. This is a logistical trade-off; having enough stars in the atlas for such detailed hopping would make the atlas, at this scale, so dense with stars as to be unreadable. For deep, very detailed star-hopping, either a planetarium program or something like the TriAtlas app (with stars to 13th magnitude) will be needed to supplement the iDSA. Those who are comfortable star-hopping with less-detailed charts, however, will find the iDSA perfectly adequate for the job. In many instances, I found that the iDSA was plenty "deep" enough for hopping through moderately-crowded fields.
The most serious criticism of iDSA (the Field Edition) has been leveled by a fellow CloudyNights user whose atlas had pages stick together after getting wet with dew and being left to dry for several weeks; ink had peeled off one page of his atlas and transferred to the facing page.  In searching on the Internet, I haven't yet found any other cases like this one being reported, so perhaps this was an isolated occurrence with an early printing of the atlas. (A couple of other users have reported sticking pages, but the problem has gone away once the pages have dried, and they had no issues with peeling ink.) This is the worst possible flaw a waterproof atlas could have, so it's worth taking seriously. I'm not inclined to leave anything to chance, given that the iDSA Field Edition is a $200 book, so mine stays in a clear turkey bag when out in the field to keep the dew and frost off of it. It's also recommended that pages be wiped off after use and that the atlas be dried out at home after a session before being put away—all good advice, although I'm sure many will find that such caution somewhat defeats the purpose of having a waterproof atlas. Again, though, only one instance of this problem has been reported so far.
So, all things considered, would I recommend the interstellarum Deep Sky Atlas? The answer would be a mostly-resounding "yes." As the user of a 12.5" scope, I find that the atlas provides an appropriate depth of coverage in terms of what I might expect to see, and, backed up with the TriAtlas and/or Sky Safari, I could identify any objects in a given field that are not labeled in the iDSA. The atlas is extremely user-friendly aside from its size, which largely precludes being hand-held at the eyepiece, but is more convenient than strictly using a tablet in the field; the small size of some of the type is a minor inconvenience at worst. The only hesitation that I have regarding the iDSA is the sticking pages/peeling ink issue, which may well prove to be a single-occurrence "outlier" among the body of iDSA users; as the atlas becomes more popular, this may turn out to be an isolated unfortunate instance, and it may in any case be preventable with the kind of care one takes with one's optics after a night's observing.
Stoyan and Schurig have produced an atlas that, while not perfect, may be the most user-friendly field atlas available to amateur astronomers with moderate-sized telescopes—an atlas that might stand as the apotheosis of the printed atlas in a day and age dominated by astronomy apps and planetarium programs.
--Andy Edelen, A.K.A. KidOrion
 David Knisely's filter recommendations for various nebulae can be found at http://www.cloudynights.com/page/articles/cat/user-reviews/accessories/astronomical-filters/filter-performance-comparisons-r1471
 It should be noted that the author has issues with colorblindness in the red end of the spectrum, so others may see these colors somewhat more or less strongly.
 The account of this can be found at http://www.cloudynights.com/topic/488677-interstellarum-oculum-deep-sky-atlas-it-is-here/?p=6462792
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