Bi-Polar:

Of the 62 images in our catalog 34 of these are polar nebulae. The nebulae categorized in this group have distinctive mass ejections in two prominent opposite directions. The polar nebula are then put into two categories dependent on the number lobes viewed. Nebulae with more than two lobes are considered multi-lobed, while nebulae with two lobes are further sub-categorized. These bi-lobed nebulae are further categorized depending on the mass ejection angle and by the shape of the lobe.

A feature viewed only in the polar category is the presence of extinction features which resemble a disk or perhaps a torus inclined to the line of sight. Light passing near the edges of these features is generally redder than that of the local surroundings as - expected if extinction features.

MulitLobed:

A proto planetary nebula is classified as multi-lobed if it has features in a common direction, such as CRL618.

MultiPolar:

Six of the archived images fall into the multi-polar category, defined by more than two prominent directions of elliptical out-gassings. While some nebula in this category are point symmetric it is not true of all nebula in this category.

Atypical:

The round category, containing 13 of the 62 images, can be broken down into three sub-groups. These groups are characterized by ring, symmetric, and amorphous visible structure. The ring sub-group contains nebulae that have distinct circular structure(s) emanating about a central point. Nebulae in the symmetric sub-group have opaque out-gassings emanating out from the location of the central star. Amorphous type nebulae have no distinct symmetry or preferred direction, and are irregular inside the prominent round structure.

Uncategorizable:

These are objects which cannot be put into any category because they exhibit unique or obsure features.