Re: [ATM] infra-red

["ATM_jcbj" <atm_jcbj@bellsouth.net>]

(ATM Superheros?  Haha.. cute.)

I can vouch for the Baader IR/UV-Cut filter.
It works amazingly well!
It has a high roll-off curve just below the IR wavelengths that you want
to keep.
It cleared up a lot of fuzzy issues with my Logitech QC3k after I
removed the CCD IR filter (I scratched it actually while building a case
for it and had to remove it)

Here's a site (granted, it hasn't been updated in a while), that has
spectrometer comparisons of a few various popular IR filters.
It's a good read in general for information related to this thread.

http://www.leadbeaterhome.fsnet.co.uk/IRB_filter_spectra.htm

As I have read there and have heard from others, the stock CCD filters
in most digital cameras (and especially webcams) are targeted towards
general daylight use with no thought for the astronomy world (there is a
Canon model now, I believe, that was made with astronomy in mind and has
a sharp cut-off IR filter, but it is pricey!).  Most of 'em's IR filters
are low grade and sloppy, by our standards, at least.  The Baader was
designed (and excellently designed, IMO) as a replacement for the sloppy
stock IR filters.

FWIW,
James.

QCUIAG on YahooGroups has more info on this in their archives, as this
is a common issue among the modified long-exposure webcam users there.

There are also a few dedicated spectrometry groups on Yahoo as well,
which should have even more detailed info.

There is a thread on CloudyNights also, by a friend of mine, which has
explored this topic as well with a fairly detailed scientific approach
(granted, I don't have a link for that one and it'll require some
searching to find)

> -----Original Message-----
> Hi Dominic-Luc,
> 
> these links could be of interest regarding alternatives to standard
camera
> filters:
> 
> http://www.astrosurf.com/buil/baader/eval_us.htm
> http://www.baader-
>
planetarium.de/zubehoer/okularseitiges_zubeh/info_farbfilter/infoseite-
> uvir.htm
> 
> Nils Olof
> 
> > As was explained to me, that filter also reduces red in order
> > to give more neutral color with respect to blue. The last time
> > I found absorbance scan of such a filter, it was not a sharp
> > cutoff/bandpass filter. Absorbance smoothly climbed up from
> > around 600 nm to a peak around 900 nm.

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