From: "Alan Friedman" <alan@greatarrow.com>

Date: October 1, 2006 10:04:13 PM MDT

To: <Astro_IIDC@yahoogroups.com>

Subject: Re: [Astro_IIDC] IR filtering for luminance

Reply-To: <alan@greatarrow.com>

Hi Ray 

---------- Original Message ----------------------------------

From: Ray Byrne <ray@in4media.co.uk>

I understand this from the use of the Baader Solar Continuum filter  

for the Sun i.e. a narrow window of the spectrum that can punch  

through the daytime seeing in the case of Solar imaging. Am I correct  

here?

A green filter on the Moon is probably going to give better results  

on the mono camera as the camera is most sensitive in this part of  

the spectrum (we suffer the same weather systems I think) according  

to no.1 - I think I'm correct here

From my location, the IR and R filters are used a lot. I have used a green filter to 

advantage on the moon only once in two years! Good seeing for me is 6/10 - it is 

better than this only on very rare occasions. Most of my Jupiter images in good 

seeing use a luminance image that is created from red and green. Usually the red 

is a little sharper than green and both are noticeably higher in resolution than the 

IR. (for Jupiter and Mars you will need to create luminance images from more than 

one filter or you will not capture the complete aspect of the planet because some 

features are only seen at certain wavelengths - ie cloud activity on mars is 

captured in green and blue but not in red). 

The beautiful thing about webcam imaging with a filterwheel (I use a manual one) 

is the ability to see the results quickly in real time as you switch between filters. It 

will take some experimentation and practice to see what works best with your 

equipment and location.

When you mention RGB imaging are we talking about cameras that aren't  

mono i.e. "one-shot colour cameras?

If so do the Red, Green and Blue filters need to have a block for IR?  

The filters I'm intending to purchase are quite expensive and are  

blocked for IR but I'm sure this is with DSO imaging in mind by the  

supplier.

No, I am talking about (L)RGB imaging with a monochrome camera here. My 

filterwheel is set up with a set of SBIG RGB filters with IR blocking and a Baader IR 

pass filter.

best -

Alan