Cambridge Double Star Atlas

The Cambridge Double Star Atlas

“a review of the latest Double Star Atlas, and a comparison with the Pocket Sky Atlas”

Some days ago I took delivery of The Cambridge Double Star Atlas by James Mullaney and Wil Tirion. (ISBN: 978-0-521-49343-7) which has just been released by Cambridge University Press.

I was very much surprised since expected delivery from my Dutch online bookstore was quoted at late March. So my wife had a Valentine’s gift sent which saved some cash this month.

I have been busy with doubles the last 5 years using mostly refractors in the 60-80mm range.

Upon opening the book my thoughts were struck to how familiar this Atlas was to other Tirion works I had in my possession since well, since I started out in 1986 as a 9 year old.

Quality again throughout, and surprise, a spiral-binding which is a Godsend in the field.

Score 1 for the CDSA.

The book starts out with an Introduction which states the usual just like the PSA does, which is my workhorse-star Atlas. The atlas comprises of 30 maps laid out in a standard fashion like we know from many other Atlases. The PAS has been divided into Gores which when used to are very much intuitive, but after using old-fashioned charts for nearly 2 decades having a bigger scale atlas with “regular” layout again was like meeting an old friend again..

Score 2 for the CDSA in my book.

Here the Cambridge Double Star Atlas

Here the Pocket Sky Atlas

The CDSA’s introduction gives a rundown of what is needed for satisfying Double Star observing from tips of how to use your equipment, to keeping your hands warm. A short text about optical quality and how to test it, a small note on the need for collimation, but not about how it’s done. Also 2 or so pages are dealing with learning to see, as this is an art as well as a skill. And as such it can be trained, and it must be.

Following this introduction we are introduced to what the authors consider the 133 best doubles in the skies. The list is not a dry drilldown of number and figures but also gives some notes and pointers to help you get acquainted before you even look through the eyepiece.

At the end the authors are introduced and a well-thought out bibliography is mentioned.

Now onto the main course of the book. The 30 maps.

Just to get some insight in how they differ from one another I have made some pictures from pages showing the same part of the sky.

Lyra in the CDSA

Left the PSA, right the CDSA

The things which are most apparent is that many deep-sky objects do show in the CDSA as well as the PSA. However the PSA wins here as it plots over 1500 objects opposed to CDSA’s 900. It’s rather logical as the CDSA has over 2500 Doubles to plot extra with their designation, the areas in Cass. and Cyg. are pretty cluttered but the larger maps as well as finer scale of the CDSA help a lot here. Because of this I feel some more Deep-Sky objects could have been included. It’s striking that many photographic showpieces especially have been omitted from the CDSA, forget about Barnard’s Loop and the Witch-Head for example. Get your PSA instead.

Stars plotted, yes both have a slightly differing limiting magnitude with the CDSA going deeper on paper, when comparing the maps of Lyra I found stars that were present on one were not present on the other, but also the other way around which seems odd. But the PSA was not made by Tirion, Roger Sinott may have chosen from a slightly different dataset and framework.

Back to another difference which makes the PSA a better atlas is the fact that the PSA is not rigidly holding onto a mathematical model of dividing the night sky like the CDSA. Maps are a bit skewed when needed to keep important constellations intact minimizing leafing through the book.

At the end is given a drill-down of all plotted and designated doubles with their pertinent data, a dry list but one which is indispensable when looking for those stars which are decent subjects for your scope. No use to go for a sub-arcseconder with my 70mm Vixen……The list helps there.

So where are we left then?

The CDSA is bigger, easier to read, has plenty of objects for owners of smaller scopes, but also plots wickedly difficult doubles for 10-inch scopes and bigger who have dynamite skies year round and don’t live below sea-level as I do.

For Deep-sky work it’s not as good as the PSA, but the PSA isn’t a deep-sky atlas either.

For its intended goal, double star observing it gets my unreserved recommendation as I hate to write down designations in my PSA. When travelling light the PSA is self-recommending, but the CDSA is no slouch either, it’s loads better material-wise than Uranometria 2000.0 which soaks up water. Both atlases have pretty good dew-resistant (not dew-proof) paper. But Uranometria plots a massive amount of objects. You can’t have it all.

Both atlases will give me loads of pleasure for years to come. I wouldn’t want to miss any of these 2.

Given my subject of study however I know that the PSA will be seeing the night-sky a lot less. And that is not an indictment, just a recommendation for the CDSA.

Regards

Marco Meiling