Images

For every object there is a DSS image. The majority of the images are 30 by 30 arcminutes in size (30'×30', half a degree). Larger objects have larger images, either 45, 60 or 75 arcminutes in size. A few very large objects have even larger DSS mosaics.
CSOG images are uncompressed. This is intentional as the option to zoom in on images is thereby retained. It is the reason the observing guides are quite large in size.

There are four options for image orientation to best suit your planning or observing needs:

• True - unmirrored: North up, east to the left
• Mirrored horizontally - M_H : North up, west to the left
• Mirrored vertically - M_V : South up, east to the left
• Mirrored horizontally & vertically - M_HV : South up, west to the left

If you are in doubt whether or not your telescope mirrors, observe a fixed object in daytime and compare the naked eye view to that in your eyepiece.

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.

Object Sorting

Objects are generally sorted by right ascension, or 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 to assure the distance between objects is minimized. Also, large constellations are divided into "blocks of declination". This allow for objects to be sorted logically in small part of a constellation, thereby minimizing large jumps in declination. This also makes CSOG a very effective tool when it comes to "constellation sweeping".

Constellations & Hemispheres

CSOG covers all of the 88 constellations. Along with the complete work covering all of the sky there are northern and southern hemisphere editions. Of course, there is considerable overlap between the two hemispheres.

The constellation of Serpens is divided into separate guides for Serpens Caput and Serpens Cauda. No constellations are divided into separate northern or southern hemisphere parts.

Constellation Editions

CSOG Constellation editions are available in three telescope aperture classes:

• 5-6" telescopes
• 8-10" telescopes
• 12" and larger telescopes - this is the "complete" edition

The above aperture division is a rule of thumb. Each version contains objects that allow you to get the most out of your equipment. That may require very good conditions: Dark skies and great transparency. That being said, (sub)urban observers using a 8" telescope will enjoy observing the objects in the 5-6" version as it contains brighter objects than the 8-10" edition does. Then again, if you have access to a truly dark sky site, you may want to hunt down all the faint fuzzies in the 12" guides.

Read more about the objects per telescope aperture on the Objects page.

Specials

There a quite a few object catalogues and object lists that stargazers like to observe by. CSOG contains the following, separately available:

• Messier, sequentially, by constellation or sorted for a Messier marathon
• Lacaille, sequentially or by constellation
• Dunlop, by constellation
• Herschel 400, by constellation
• Herschel II, by constellation
• Caldwell, sequentially or by constellation
• Bennett, sequentially or by constellation
• Palomar Globular Clusters, sequentially or by constellation
• Terzan Globular Clusters, sequentially or by constellation
• Hickson Compact Galaxy Groups
• Carbon Stars, by constellation, All Sky or by hemisphere and by telescope aperture: 5-6", 8-10" or 12"
• Globular Clusters, by constellation, All Sky or northern hemisphere and by telescope aperture: 5-6", 8-10" or 12"
• Planetary Nebulae, by constellation, All Sky or by hemisphere and by telescope aperture: 5-6", 8-10" or 12"

More about the objects in the list and catalogues on the Objects page.

Use of...

CSOG guides can be printed or used on a tablet, e-reader or laptop computer. When printed they can easily be stored in binders using sheet protectors. This protects them from dew or the accidental coffee spill. Please do keep in mind that printing the guides requires a significant amount of paper and printer ink. Alternatively, the guides can be viewed on a tablet computer such as an iPad or Galaxy Tab, on a computer screen or on an e-reader. Use of a screen without additional measures will of course have an effect on your night vision. Therefor, tablets or computer screens must be dimmed as much as possible. In addition, a red screen cover, as dark as you can get it, should be used. Plenty are available on the web.
It is up to you to decide which application you prefer to use to read the guides on a tablet. For iPad users the app Filebrowser is recommended, as it allows for easy transfer of content and provides a full screen viewing option. That being said, amateur astronomy is in need of a dedicated "astroreader" app for both iOS and Android, with an in-app dimming option and customizable background color. Developers, are you reading along..?

Basic Knowledge

To use the CSOG observing guides effectively some basic knowledge of the sky is an advantage. It helps to be familiar with the celestial coordinate system (right ascension and declination) and units of measure (degrees°, minutes' and seconds"). Knowing directions in the eyepiece of your telescope (north, south, east, west) will aid in locating objects, finding object details and will help to locate objects in the vicinity such as the many double stars mentioned in the CSOG field descriptions. Knowing the actual field of view of your telescope-eyepiece combination will help to compare an object's DSS image to what you are actually observing 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 starchart you already own will be all you need.
For all of the objects in the observing guides 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 mentioned on the chart. After you make the starhop and have the telescope pointed to the area where the object is, the DSS image will aid in locating the exact position.
If you insist on having a CSOG-specific finder chart to aid in locating an object, AstroPlanner is any easy way to create them. Planfiles containing all of the objects in the guides and tours are part of the CSOG concept and AstroPlanner allows for quick and easy creation of customized charts.

The Potential for Discovery...

Ever observed an object and noticed a faint smudge right next to it? I did. Did you heart skip a beat? Mine did. Ever worked out observations including a mystery object days, or even months after the observation was made... only to discover there is no object at that location? Been there, done that. And it happened only twice. In fact, it has been a major contributing factor to the creation of CSOG.

Using CSOG there will be no more second guessing whether or not there is an object in the vicinity. DSS images don't lie. If you ever stumble upon a faint fuzzy that really shouldn't be there, chances are that it's a mover. A mover that just might get your name attached to it.

The Size of CSOG

As you will read on the Objects page, CSOG is a rather large publication. If you were to print the complete 12" All Sky edition, assuming three objects per page, printed double sided the total number of pages would be approximately 2300.
If all of the CSOG guides in every edition, including mirrored ones and hemisphere editions were to be printed once, this would result in well over 39000 pages. Excluding title pages and indices.
That is why CSOG is a digital publication.