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Cambridge Double Star Atlas

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#26 Svezda


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Posted 24 May 2013 - 05:30 PM

I love the CDSA so much that it has become my default atlas unless really faint deep-sky objects are my goal. The layout, size, typography, color choices, etc are just right for me and I suspect for many others.

My only criticisms, and they are not trivial for double star observers, are these:

1) there are numerous strange cases where doubles, even not particularly faint ones, are marked on the atlas as double (with a line) but have NO designation on the chart and NO description in the appendices. These appear as simply mistakes, but I'm not sure as they seem so obvious. I wonder if there is a reason such as they are considered too difficult for most telescopes...but if so, why would they be marked. I don't have my atlas in front of me to give examples and there aren't many that I can rememeber...

2) There are some examples of stars in the atlas simply marked with the name of the discoverer: Just 'Franks'!! This is simply weird. Can you imagine a catalog, say by me, simply named 'Jason's Double Star Catalog' with a list of stars I found with no designation at all. Weird. I've never heard of this discoverer and never heard of a catalog with no sequential numbers.

3) There are no position angles given! I know that these change, some within a few years, but most don't change in many years. I'd think that almost all could have been provided with PA with maybe a symbol next to the PA or a specific year given for the measurement if the PA changes rapidly. This is a real oversight or simply a mistake in judgement not to include this data.

4) The failure to include a cross reference of the doubles by constellation means that it is /quite/ tedious to find a double in the appendices that you note on a chart. Many times I see a double on a chart and want to know if it's worth my time to locate it to see if the separation is reasonable, but it takes quite a while to find in the appendix.

I've made this problem much easier on myself by spending a lot of time carefully putting labeled tabs (with permanent fine-tip marker) on each atlas page and tabs for each appendix page giving the approx. range of RA that the page covers...for example, in the appendix there might be a tab that shows 03h30m - 04h20m (but I put wrote second part of the range below the first to make the tabs more compact).

The tabs are rather robust plastic and are securely attached to the pages, so I haven't had any issues with them coming off or tearing. I like that I can grab onto a tab and get to the chart or appendix page I want quickly.

I also took care to label the tabs so that although the writing faces me when I look at the book closed, when I take a tab and pull the page open, the page is displayed...I mean that the tab is placed on the previous page. Otherwise I'd pull a tab but the previous page would be displayed when I opened up the atlas with a tab (if that is understandable).



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Posted 26 May 2013 - 07:26 PM

Dear Sveda,

The CDSA is also my favorite Atlas. Regarding your criticisms, I would like to share some thoughts:

1. I guess a star atlas is a bit like looking at road map on Google Maps: the more you zoom in, the more street names you see. In developing the parameters for scale, limiting magnitude, and final publication size, the doubles shown without names may have been unworthy of the extra ink. In looking closely at the Atlas, you will see that there probably as many Unmarked non-double stars as marked stars.

2. W.S. Franks was a British Astronomer (1851-1935) and a member of the Royal Astronomy Society (RAS). In the front of the Atlas, pages 3-4-5, there is a list of 88 designations used in the Atlas, so Franks is not the only astronomer I had to look up! Franks gained notoriety by visually classifying stars' colors before spectrospy was developed. In 1878 he published Catalogue of the Colors of 3890 Stars. In his later life, he focused on measuring the separations of double stars. Having a celestrial object named after you is rather like winning the Heinsman Trophy: the astronomy brotherhood is pretty generous about that. These is a nice vignette of him written by Sir Patrick Moore in the Digital Library for Physics & Astronomy at SAO/NASA here:


3. Position Angles: These were not included in the CDSA but are included in Sissy Haas' catalogue. Having both books available makes it easy to overcome these nuisances.

4. Sorting the Appendix by Ra/Dec then constellation was a huge mistake in my opinion. As I noted above, it is my only critism of the Atlas.

By the way, nice work on putting tabs on your pages :cool:

Bill Pickard

#28 Sarkikos



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Posted 28 May 2013 - 11:04 AM


It looks like you're having fun, so more power to you! I have a pair of 25x100 binos, also. It is fun to take them out with an atlas and observe doubles or Messier objects. It's getting so I don't need an atlas to find most of the M objects. I only need my memory. But I'm way behind on the doubles! Well, they'll give me something to do when I retire.

I've seen how other observers mark up their atlases like you do with circles, distances and other notes. For me, though, all I need is to look at the atlas, point with the binos, and I pretty much figure out on-the-fly the scale involved and the direction and offset from bright stars to the objects I want to find.

Personally, for me, all that preparatory work in an atlas - charting and measuring and planning star hops - would detract from the hunt, not increase the pleasure involved and not appreciably decrease the time necessary to locate an object. Though there have been some exceptions for particularly difficult objects. But to each their own.

The point is moot, however, since I've discovered Sky Safari Pro for my Android tablet. The star atlas is virtually infinitely scalable. No flipping between charts. There are supplied observing lists, including one for double stars. You can download other lists or generate your own. And you can select a list and have all the objects in that list appear circled on the atlas. This makes it very easy to go from one object to the next in a list of double stars. Also, you can select an object - such as a double star - and see information on it at the top of the atlas screen, or more extensive information on a separate screen.

Since I started using Sky Safari Pro, I hardly ever use any printed atlases.


#29 Sarkikos



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Posted 28 May 2013 - 11:10 AM


Sorting the Appendix by Ra/Dec then constellation was a huge mistake in my opinion. As I noted above, it is my only critism of the Atlas.

I agree. I'm an old star geezer. No goto or DSCs here. Mostly use alt-az mounts, so no GEM with manual setting circles, either. When I'm outside under the stars, I live in the constellations. Ra's and Dec's hardly ever enter my mind. Don't need them, don't use them.


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