The Sharpless catalogue of Hydrogen Alpha (Ha) regions is a goldmine of objects for the narrowband astrophotographer. The targets range from bright familiar targets to very dim obscure nebula that are extremely hard to get into decent images.

Recently I found a fantastic resource to help with planning Sharpless Catalogue imaging sessions......

The Sharpless Observing Atlas is a very large PDF file - the link to download it is at the end of that page. The document contains hundreds of pages. Each Sharpless catalogue object is dealt with. There are observing notes, maps to locate the object and an image and description of each object.

Simply flipping through the pages is a delight. You will quickly find inspiration of what object to tackle on a different night. The Sharpless catalogue is roughly order with respect to the sky - the objects are ordered by RA, so you can easily find the range of objects suitable for narrowband astrophotography at any particular time of year.

Unofficially we tend to put the Sharpless catalogue items into two groups. Some of the Sharpless objects are just repeats of items found in other catalogues. For example, Sh2-199 and Sh2-190 are more commonly known as IC4040 and IC1805, the Heart and Soul nebula.

However, many of the Sharpless catalogue entries, e.g. sh2-129 are not featured in any other common catalogues. In some ways these are the true Sharpless objects and are usually the ones which are a real challenge to image. As they are not in other catalogues, they are usually the dimmer objects, and much more challenging to image.

The Sharpless catalogues have an large range of sizes. Some, such as Sh 109 simply indicate the general Ha regions around Cygnus and are over 1000 arc minutes across. At the other end of the scale, some are only a couple of arc minutes across. First, this means that whatever your kit, and however big your telescope and imaging sensor CCD camera, you will find something that fits nicely.

It also means that if you wish to compile images of many of the Sharpless Catalogue objects, you are going to need a wide range of equipment. The smallest targets will need large telescopes over 1000mm focal length, whereas the bigger targets will require very short camera lens and such like.

Try and see how many you can catch over a lifetime!