Comet Filter

Post by **Airconvent** » Mon May 24, 2004 2:53 am

I came across this product called a Lumicon Comet Filter and was wondering what kind of filter it is. If I am correct, the comet mostly gives out light in the visible spectrum, so the most this "comet" filter should be is a broadband filter to remove effects of street lights in a light polluted area.
Any comments on this?

rich

Post by **weixing** » Mon May 24, 2004 5:49 pm

Hi,

bandpass filter for comets (25nm) isolates just the 501nm OIII and the 514nm Cyanogen lines

Look to me that it is very close to OIII filter. May be a UHC or OIII filter can also produce a similar result.

Have a nice day.

Post by **Airconvent** » Tue May 25, 2004 1:24 am

weixing wrote:Hi,
bandpass filter for comets (25nm) isolates just the 501nm OIII and the 514nm Cyanogen lines
Look to me that it is very close to OIII filter. May be a UHC or OIII filter can also produce a similar result.

Have a nice day.

Hi Wei Xing
I don't think so. Emission nebula are such due to the intense radiation from newly born hot stars causing the hot gases from which the star was made to glow. Examples include M8 and M42. The main gases exited to glowing state are normally OIII and Hydrogen-Alpha which is why OIII and HA filters work very well for such nebula.
As far as I understand, comets are dirty ice ball of dirt and dust. When the sun heats its surface up, the top layer of ice boils away resulting in a tail.
These should normally be visible in the normal light spectrum. That is why I suspect the so called comet filters are simply glorified broad band filter designed to reduce "glare" from city lights to improve on the contrast of the comet...

rich

Post by **weixing** » Tue May 25, 2004 1:53 am

Hi,
Ha Ha... I know that comet and star are very different

But that is what they said that the Comet Filter will do... isolates just the 501nm OIII and the 514nm Cyabogen lines in Lumicon website. May be they discover that most comet also give out quite a lots of light in these wavelength...???

Anyway, I think the Comet filter is somewhere between a UHC filter and a OIII filter.

Have a nice day.