IDAS has just released a new light pollution filter The IDAS LPS-D2: https://digiborg.wordpress.com/2018/02/13/idas-lps-d2-filter/
A well as cutting out the main emission lines in Sodium street lights, it also cuts out the nasty blue peak in the LED variety.
Depending on the spectrum of light pollution in your own area, this new filter could be a useful addition.
Mark
Hmmmm.
Depending on the amount of light they are actually filtering out,
would it not be a better option to goto narrow band filtering, Ha, Hb, Oiii,
I realise that this depends on if you have a mono CCD or Colour.
I know that you now have to do three images. One for each of the R (Ha) G (Oiii) B (Hb)
Well 4 if you include Luminance.
On a side note as well.
Also you used to be able to get a three narrow band filter in both 1 1/4 & 2"
which combined Ha, Hb & Oiii into one filter, that might be a better option as that will only allow through the RGB data your looking for.
You could use that other one just for luminance data.
Mac.
Note to self, I must get my stuff cleaned and up and running again. :cheesy:
But doesn't narrowband exclude RGB wavelengths?
Carole
A useful interactive chart of how the various IDAS filters cut out emissions from streetlights:
http://sciencecenter.net/hutech/idas/lps-test/
Mark
QuoteBut doesn't narrowband exclude RGB wavelengths?
Nope, they are exactly that RGB. ish....
Ha emissions are red, Hb emissions are blue and Oiii emissions are Green.
Yes they restrict the actual light collected to only those wavelengths,
but they filter out all your other sources of light pollution.
(http://www.astropix.com/images2/i_astrop/filters2/curve.jpg)
Mac
Quote from: Mac
QuoteBut doesn't narrowband exclude RGB wavelengths?
Nope, they are exactly that RGB. ish....
Ha emissions are red, Hb emissions are blue and Oiii emissions are Green.
I don't think Hb is often used. The Hubble palette is SII, Ha and OIII.
Mark
The hubble pallet is 6 filters
Sii for luminace,
N for Orange
Ha for brown
Oii for Cyan
He for Blue
Oiii for violet.
So technically you cant just dump the images onto each of the RGB channels to create the image,
you would need to colorise the individual layers to match each specific colour.
Mind you at the end of the day its all a subjective subject when it comes to colour. (Deja Vu I remember a post similar many years ago.)
Mac.