Filter Basics

Hi all

I am just getting back into astronomy after yrs away from it. Can anybody
recommend a link or publication that will tell teach me the basics of using
filters for observing and for use with basic astrophotgraphy.

Thanks

Chris

C6 NGT
SPC900NC

Chris wrote:
Hi all

I am just getting back into astronomy after yrs away from it. Can anybody
recommend a link or publication that will tell teach me the basics of using
filters for observing and for use with basic astrophotgraphy.

You actually want different filters depending on whether you intend to
observe visually or photographically (and even for film vs CCD). Also
know what sort of light pollution you are up against - some of the US
broadband ones are for mercury streetlamps which are rare in the UK.

In the UK for basic visual use I think the Orion Optics UK Sodium light
filter is as good as any in a UK mixed HPS/LPS light environment and it
is better than the more expensive US branded filters.

http://www.orionoptics.co.uk/ACCESSO...lterspage.html

I think the Nonad photographic filter I offer is pretty good provided
that most of your street lights are yellow low pressure sodium (but then
I could be biassed). It selectively eliminates the sodium D-lines and
very little else so colour balance is largely unaffected.

The Baader Neodymium is a similar filter available in eyepiece sizes. It
isn't a good choice visually. The eye needs a more brutal filter.

A rough idea of what it can do photographically is online at:
http://www.nezumi.demon.co.uk/nonad/nonad.htm
(shameless plug)

Try observing for a bit without filters to learn what you scope can do.
Often choosing the right magnification can be better visually or waiting
for the very clear nights that follow recent cold fronts passing over.
The rain washes most of the muck and rubbish out of the atmosphere.

Somewhere or other there is David Knisely's filter FAQ but it only
covers US brands. I couldn't spot it on Google just now but try
http://www.cloudynights.com/item.php?item_id=1520

I have on a few occassions seen the milky way clearly from Greater
Manchester under the very clearest conditions.

Regards,
Martin Brown