Baader IR filter

I keep seeing these getting used for webcam imaging? How good are they? This might be a dumb question, but, is it really useful to filter our UV and IR light?

Mauricio
http://www.geocities.com/carimau

Hi Mauricio,

Yes, I think these filters are helpful. In an optical system with refractive elements the UV and IR foci may be quite far off from that of other wavelengths lending a softness to the image and blurring fine detail. This is especially the case with IR because most CCD chips are sensitive at these wavelengths - and also for objects lower in the sky, where the atmosphere acts as a refractive element and spreads the focus of the red and blue further apart.

The drawback is that there is some light loss from this filter so exposures will be lengthened a little. Fortunately the filter is reasonable - you can try it out without a big investment and see if it helps.

Alan

If you have a refractor, yes. For reflectors and SCT's I've yet to see an advantage. Just another optical surface in the way.