Observing Guides

CSOG's main content is the observing guides. The guides are intended to be used on a tablet - dimmed and with a red transparent filter attached - at the eyepiece of the telescope.

Using the guides, observers will know before, during and after an observation what it they are looking for, what it is they are observing and what other objects are visible in the vicinity. The guides take out all the guesswork.

Object Categories

A guide's title is the object category with the constellation's name, the object category's abbreviation and, where applicable, the number of the guide for the object category in the constellation. For example, the second open cluster guide for the constellation of Cygnus is named "Open Clusters - Cygnus OC-2".

The object categories in CSOG are:

Object Information

Objects are named by their historical designations. Meaning the first catalog to list an object is the primary name. NGC superses PGC, Minkowski supersedes Sharpless, etc. Synonyms are included where applicable.

Below the object's name and its synonyms is the celestial coordinate in epoch J2000.0. To the right is relevant data such as magnitude and size, position angle for galaxies, etc.

Instead of using abbreviated Dreyer's descriptions for objects, the description is always in complete words. Therefor you will not find a description such as "pL vF E gbM vbN" but will instead read "Pretty large, very faint, elongated and gradually brighter in the middle with a very bright nucleus".

Field description

Along with the description of the object, a field description is included in a smaller font. Noteworthy objects within 30 minutes of arc (one degree centered on the object) and relatively bright stars are named, with bearing and distance from the object in the guide: stars up to mag. 10, double stars up to mag. 10 with a separation of 0.7 seconds of arc or greater, carbon stars up to mag. 11 and all other objects in CSOG.

Images

There is a DSS image for every object. Unless noted, images are 30 by 30 minutes of arc in size (30' × 30', half a degree). Quite a few objects have larger images, with the object size depicted in the top left corner. A few very large objects have even larger DSS mosaics.

CSOG images are uncompressed. This is intentional as thereby the option to zoom in on images is retained. It is the reason the observing guides' files are quite large in size.

There are 4 image orientation options:

• Unmirrored: North up, west to the right
• Mirrored horizontally - M_H : North up, west to the left
• Mirrored vertically - M_V : North down, west to the right
• Mirrored horizontally & vertically (= rotated 180°) - M_HV : North down, west to the left

Click here to read more about CSOG image orientations.

There are no esthetically pleasing color images in CSOG. This is intentional. The guides are written to make the most of an observing session and are intended to primarily be used at night, behind the eyepiece of a telescope. The DSS images provide a fixed reference, a "standard candle" for visual astronomy.

Object sorting

Objects are sorted by constellation and by object category. There are no more than 3 objects per page and, as a rule of thumb, no more than 30 objects per observing guide.

Objects are generally sorted by right ascension (R.A.). That means starting in the west and working towards the east, but not purely in R.A. When the next object is nearest in right ascension, it may not be the closest as its declination may differ significantly from the preceding object, when another object may be much closer in declination but only slightly farther in right ascension. Therefor, CSOG objects are sorted so that the distance between objects is minimized. Also, objects in large constellations are divided into "blocks of declination". This allows for objects to be sorted logically in smaller parts of a constellation, thereby minimizing large jumps in declination. This makes CSOG a very effective tool for constellation sweeping.

"By Object" Editions

Observing guides for single objects, with a large image, minimum 15’ (a quarter of a degree), that fills most of the page. The second page in these guides contain a 75' or larger image that depicts more of the surroundings. Where available an SDSS image is included in the Arp, Hickson, Holmberg Groups, KTG and KTS editions.

Use of...

CSOG guides are best used on a tablet. Please read iPad Astronomy.

Basic knowledge

To use the observing guides effectively, basic knowledge of the sky is required. It helps to be familiar with the celestial coordinate system (right ascension and declination) and units of measure (degrees°, minutes' and seconds"). Basically, you need to be able to read a starchart.

Understanding cardinal directions in the eyepiece of your telescope (north, south, east, west) will aid in locating objects, finding object details and to locate objects mentioned in the field descriptions. Knowing the actual field of view of your telescope-eyepiece combination will help to compare an object's image to the view in your eyepiece and vice versa.

No starcharts

There are no CSOG specific starcharts. That does not mean CSOG is goto-telescope only. Starcharts are not included because the chart you already own will be all you need.

For all of the objects the celestial coordinates are included. This allows you to easily plot an object's exact location on your starchart, even when the object is not depicted on the chart. After you make the starhop and have the telescope pointed to the area where the object is, the DSS image takes over to locate the exact position of the object.