Amongst the nebulae regions are those areas that are predominantly Emission nebulae. The atoms in the clouds of high temperature gas are energized by ultraviolet light from a nearby star and emit radiation as they fall back to lower energy states (in much the same way as a neon light). Other types of nebulae also emit specific wavelengths of energy based on the elements and mechanisms present in their structure. Narrow band images use special filters that pass specific wavelengths of light. These wavelengths are chosen to match the energy emitted by elements present in the nebulae. The list below gives some of the predominant elements and their emitting wavelengths.
Element |
Wavelength |
Colour in visible spectrum |
Double ionised Sulphur |
673.4 |
Red |
Double Ionised Nitrogen |
658.4 |
Red |
Hydrogen alpha |
656.4 |
Red |
Helium |
587.6 |
Green |
Triple ionised Oxygen |
495.9 and 500.7 |
Blue / Green |
Hydrogen beta |
486.1 |
Blue |
Double ionised Helium |
468.6 |
Blue |
The most predominant of these elements is Hydrogen
making the wavelengths of H Alpha and H Beta very important. The triple
ionised Oxygen (OIII) and double ionised Sulphur (SII) are also important.
The seperate images taken through the different filters can then be
combined into colour images. Because narrow band filters isolate specific
wavelengths it is possible to use them under light polluted and Moonlight
skies where conventional imaging would be difficult or impossible.
The Messier Objects.
Charles Messier was an astronomer who lived between 1730 and 1817. He
was primarily interested in hunting for comets but catalogued many non-stellar
objects so that they would not be confused with the comets he was looking
for. With additions by other astronomers, there are 110 Messier objects,
many of which are very well known. The Orion Nebula for example is a
very well known Messier object and is catalogued as M42. Another famous
object is M16, the Eagle Nebula made famous by the Hubble Space Telescope
images “ The Pillars Of Creation”.
There is one anomaly within the catalogue, and this is M102. It is thought
that it may be a double entry for the galaxy M101, or an observation
of the galaxy NGC 5866.
Best images.
This page contains those images that I believe represent
my best efforts to date. If you disagree, or think others should be
there instead, let me know.
Other Images.
This page contains images of phenomena, objects and
events that do not fall neatly into one of the main heading catagories.
You will find pictures of aurora, sunsets and such like here.
NGC / IC
The New General Catalogue and the Index Catalogues attempt to form a
complete list of all star clusters and nebulae known at the time of
their publication. The NGC was published by J.L.E Dreyer in 1888, followed
by the supplemental IC in 1895 and 1908. Almost all bright large non-stellar
objects that are nearby have entries in one of these three catalogues.
The number of the object is preceded by the catalogue abbreviations.
There are, however, numerous double entries, positional information
that points to empty areas of the sky and numbers that point to stars,
double stars and multiple stars. Many galaxies are also know by their
NGC or IC numbers. This is due to the information that Dreyer was working
with at the time he compiled the catalogues. He used information from
many diverse sources but the errors are not his own as he was meticulous
in his work.
Welcome
to my astrophotography site.
I have been interested in Astronomy for many years but did not get my first telescope until 2000. My interest soon turn to astrophotography, inspired by the many excellent images from across the world in magazines, and on the web. I do most of my imaging from my garden in Wiltshire, UK with the occasional trip to darker sites. I am fortunate enough to live on the edge of Salisbury Plain so do not suffer from as much light pollution as many areas in the UK. However, I still have to cope with some pollution to the south and east where I look out over the towns and villages.
I begin taking images with 35mm black and white film that I processed in my own dark room. I then progressed to CCD imaging, where I have made the most significant progress as my experience has increased.
This site contains most of my images, from the earliest, to my latest. Needless to say the quality has improved. It is hoped that by showing the good alongside the bad, others will be encouraged to keep at it.
Finally I would like to thank all those other astrophotographers out there who have shared their experience so that others like myself can progress.
Some images on this site were created with the help of the ESA/ESO/NASA Photoshop FITS Liberator.
All images on this site are the property
of David Osborne unless otherwise stated.Please let me know if you wish
to use any of these images.
 |
|
|
|
 |
|
||
 |
 |
 |
|
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
|
||
 |
|
||