TheSkySearchers

Where would I find the RASC celestial object classification (type) abbreviations list? I've looked everywhere and can't find just a list of what the abbreviations mean. Some of them are obvious, it is the sub-classification abbreviations I'm interested in. For example G-SAab, what does it mean?

Thanks,

Hope this helps, although I am far from what you'd call an expert

The Observers Handbook will give an explanation of types in each section. For example Galaxies on pg 330, Messier objects on pg 312 etc although you may have to dig around online for the finer designations. For your Galaxy, look up info on the Hubble sequence and de Vaucouleurs system which is an extension of it.

You can also look at the following for info on celestial object designation but note the pages state that : Celestial nomenclature has long been a controversial topic. and A look at the current literature reveals that unclear, ambiguous or confusing designations of astronomical sources of radiation are too often encountered. So it sounds like it is/was a bit of the wild west when naming things.

https://www.iau.org/public/themes/naming/

https://cdsweb.u-strasbg.fr/Dic/iau-spec.html

Classification of objects, particularly galaxies can be quite confusing. The example you gave, "G-SAab" would indicate a galaxy, with a de Vaucouleurs classification of SAab. The de Vaucouleurs classification system for galaxies is the generally accepted method for galaxy classification as an expansion on the original Hubble scale. Now, SA indicates an unbarred spiral galaxy. The lower case ab would indicate an intermediate morphology, with a pronounced central bulge and tightly wound spiral arms that are partially resolved. Messier 81 is a good example of this type. There are all kinds of sub-classifications within this system, and it can get quite confusing. In all honesty, while I find it interesting, it is not something I devel into to any great extent.

As for other objects within the RASC (I am familiar with their handbook, but never looked at one), I would have thought they would have included some sort of reference to object classification. For various types of objects there are classification systems, such as the de Vaucouleurs for galaxies. I would have to see some of the ones you are wondering about to get a better sense of what they are using in their materials. Sorry I couldn't be of significant assistance.

A picture would probably help. Here is an image of the list for the Messier marathon. I'm referencing the column named Type. I understand every other type but the Galaxy designations. So that's what generated my question.

Thanks.