Home
Products
Materials Services
Contact us Location
Galvoptics Ltd, Harvey Road, Burnt Mills Industrial Estate, Basildon,
Essex, SS13 1ES.
Telephone +44 (0)
1268 728077
Fax +44 (0) 1268
590445
|
Nebula Filters |
|
|
Filter Sets |
NEBULA FILTERS FOR LIGHT POLLUTED
SKIES
Night Image 1, 2, and 3 filters help observers
to see fainter and more difficult targets. Light pollution falls into three
types, NATURAL, LOCAL, and REGIONAL.
Natural light pollution called ‘airglow’ is
caused by charged particles from the SUN bombarding oxygen in the Earths upper
atmosphere. Its strongest wavelengths are between 560 to 630
nanometers. Whilst not discernibly visible to the
naked eye, it may still decrease contrast in the eye piece to ‘hide’ dim
targets.
Local light is nearby glare that infringes on
observing sites from street light etc. A filter cannot stop this. All you can
do is shade your observing position.
Regional light pollution is the real problem.
Populated areas, roads and motorways pour light into the sky. These and other
sources combine to create the orange gray haze we see
above our cities and towns. The right filter can help to reduce this by
suppressing the ‘bad’ wavelengths, but allowing the ‘good’ wavelengths from
celestial objects to pass through.
The NIGHT IMAGE range of filters, are designed
to dim and blockout the areas of the spectrum which
are a problem. In doing this, the net visual effect is, ‘increased contrast’
between the object and the filter darkened background.
In short, it can enhance the visibility of the
object.
The problem wavelengths are:
High pressure sodium vapour lights between 550
and 630 nanometers.
Mercury vapour lights
between 405 and 436 nanometers
Low pressure sodium lights emit mainly a narrow
region approx 590 nanometers
THE THREE NIGHT IMAGE FILTERS WE SUPPLY HAVE
MULTI-LAYERED INTERFERENCE COATINGS.
NIGHT IMAGE 1
A broad band filter for observation of the night sky
@ £48.47
each P&P £2.00
NIGHT IMAGE 2
A narrow band filter for
those interested in spotting fine detail in emission and planetary nebulae.
@ £51.70 each
P&P £2.00
NIGHT IMAGE 3
A broad band filter
for night observation and photography using red-sensitive film, such as ILFORD
SSX 200 or KODAK Tech Pan 2415, both black and white films. If you use colour films, these filters will
produce cyan tinted stars.
@ £ 40.80 each
P&P £2.00
SET ALL THREE
FILTERS
£125.26 per set
P&P £6.00
PLEASE NOTE
ALL OUR PRICES INCLUDE VAT @ 17.5 %
WE RESERVE THE RIGHT TO CHANGE PRICES WITHOUT
NOTICE
PAYMENT IN £ STERLING ONLY
CHEQUES SHOULD ACCOMPANY ORDERS
P&P PRICES MAY DIFFER BY REGION
PLEASE CALL FOR QUOTATION IF OUTSIDE THE UK
Home | Products | Materials
| Services
| Contact us
Phone
+44 (0) 1268 728077
Fax
+44 (0) 1268 590445
This
document maintained by sales@galvoptics.fsnet.co.uk
Material
copyright Ó2003 Tim Wale