IR Filter

[TheThing]

I picked up an IR filter from Astroboot on scopes 'n' skies as a kind of impulse buy.

Am I right in thinking this will make absolutly no diffference with visual observing, but is better used with a webcam?

What does an IR filter really do and how does it affect the final image?

[brantuk]

It should let more longer wavelength reds through typically emitted by nebulae (as I understand it).

[steppenwolf]

Filters don't actually increase the amount of a particular wavelength of light that reaches your eye or your camera's sensor - what they do is to filter out wavelengths of light that you don't want leaving just the ones you do want to pass through. Many objects emit infra red (IR) light but our eyes cannot detect this wavelength so we don't see it BUT camera sensors are sensitive to this wavelength so IR light is detected by them and can result in many objects having a 'bloated' appearance when photographed hence it can be useful to filter this light out so that it doesn't pass to the sensor.

[BlueAstra]

Depends what type of filter. Broadband 'IR Filters' are generally used in front of CCD chips in webcams and astro cameras to reject long wavelength IR light. The CCD chip is sensitive to light in the IR which can cause blurring of the visual image. Some webcams and cameras come without an IR filter, so you can buy an external one to compensate.

DSLR cameras sometimes have their internal IR filter DIY replaced since it cuts a little too much IR out in the important Ha wavelengths. You can also get specific filters which allow only certain wavelengths through, such as Ha, Hb, O3.

[TheThing]

Not sure which type of IR filter it is as it didn't come with any details! Will it have much effect with a Meade LPi at all?

[jgs001]

Given the price on Ab for this... I'd think it was an IR block filter... as to how much use, it'll depend on whether the LPi has a built in IR block or not. The SPC900 for example has the IR block built into the lens itself, so when you remove the lens and fit the nose piece, you leave the cam without an IR block.

[Glider]

If the LPi has a built in blocker another one won't hurt, it will function as a handy window to keep the dust out. If the LPI hasn't got a blocker built in then it will help you with bloating, etc, and as a handy dust window. I certainly notice the difference with and without on my SPC900, it's much better with.

All bets are off if it is an IR pass filter though!

[Psychobilly]

if its clear(ish) can see through it .. its IR block

If its deep ruby red or black then its IR pass...

IR block helps reduce star bloat with modded webcams etc...

Peter...

Snap lol

[TheThing]

Thanks Peter. It is pretty clear so that must equate to IR block.

I'll give it a whirl with the webcam then and see what happens. As Glider says, it can't hurt!

Thanks for all the help and advice - much appreciated!