IR and UV blocking filter

[Space Cowboy]

Is it essential I get a IR and UV blocking filter for my webcam? I've just ordered a nose piece for my logitech quickcam 4000 pro. I was hoping to keeps things cheap and cheerful but i see a UV filter is another £20. Will my images be cheap and nasty without?

[brianb]

Essential, no. But the IR/UV blocking filter will sharpen the image by reducing the atmospheric prismatic effects (UV is spread more than visible blue, and IR less than visible red, so the effect on the camera is more than it is visually). The filter will also help keep dust of the camera sensor. IMHO, very much worth the extra expense.

[riklaunim]

Depends on telescope, camera, and seeing. For refractors it is needed (even most APO arent corrected to IR). For color cams it may be needed so the UV/IR won't add false color (Mars in IR for example). For mirror telescopes (newtonian, RC...) and/or monochrome cameras it may not be needed that much as IR will stack rather nicely with VIS (or RGB views). A lot of glass (maksutov for example) halves IR/UV luminosity so also it may solve the problem

[brianb]

A lot of glass (maksutov for example) halves IR/UV luminosity

Optical glasses actually transmit better in the near infra red (the bit that CCD cameras can detect) than they do in the visible part of the spectrum. Mak corrector plates are crown glass which transmits UV as well as the atmosphere.... Most 'fracs (including ED doublets) will work better with "minus violet" and IR blocking filters (stacked) than with a plain UV/IR blocker.

[callump]

I don't think a UV filter is essential, but does no harm. CCD's etc are not very UV sensitive.

With a refractor, or any refracting optics (barlow), you need an IR filter as IR focuses at a different point, and will cause the image to be soft. 'Raw' CCD's are quite sensitive in IR.

/callump

[russ]

If nothing else it will stop dust getting on the chip and even in a reflector will help sharpen the image of targets that have a low elevation (mainly Jupiter for the last 4 years). Worth getting for £20 or place a Wanted ad and see if one gets offered cheaper.

Russ

[Space Cowboy]

Thanks guys for your brilliant info!