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Terrierist

ZWO ASI 178MC - IR Cut protector

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Hello all.

Please would someone be kind enough to explain the IR Cut filter/protector on the above camera in simple terms?

Would it reduce nebulosity or allow it to pass?

Thanks for any help.

 

Kev

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If you look at the spectral response of the camera, you'll see that it has a high red responsivity for wavelengths larger than 700 nm, which is deep red and ir. Even the other the other channels (notably green) have an increase in responsivity in the ir range. Since IR will register in all channels, it will show as gray in the final colour image. This is usually not what you'd want. The IR cut filter removes this effect as it cuts off light with a wavelength larger than 700 nm.

QE-ASI178.jpg

Btw, you get the same effect if you shine a tv remote control LED on a smartphone camera. These cameras don't always block ir, and the light shows as white light.

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I agree....

But shining a TV IR remote is like shining a searchlight at the telescope - much much more powerful than IR recorded in astronomical objects.......

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Another reason to cut out IR and UV is that refractors (and probably the correctors for reflectors) are optimized for visible light and IR and UV will be out of focus and blurr the image.

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Goran,

Only if you don’t refocus to the target wavelength.....

We in spectroscopy, regularly image at all wavelengths from UV to the NIR.

 

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Thanks for the replies, really appreciated, Wim, that was a great description for a newcomer to understand, thank you.

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