IR cut filter?

[MylesGibson]

I currently use a 290MC for planetary imaging/guiding. Someone mentioned when imaging planets, to have an IR filter. 

Do I want something like THIS to block IR and UV light, or perhaps THIS which is an IR pass filter?

What difference does an IR filter make?

[PeterCPC]

If you want true colour then you want an IR Cut filter.

Peter

[MylesGibson]

2 hours ago, PeterCPC said:

If you want true colour then you want an IR Cut filter.

Peter

Thanks. So does the IR cut filter make a difference to the images then? What difference does each make to the image? Lots of conflicting info around!

[PeterCPC]

I can only speak as I find and it sharpens the image for me and generally makes it clearer. I use a Baader Neodymium IR cut. I originally tried a ZWO IR cut thinking that it would be best for a ZWO camera but it was not as good as the Baader.

Peter

 

[astroman001]

Use an IR/UV cut. The ZWO cameras are sensitive well into the IR and this is brought to a different focus compared to the visible spectrum. You will get a sharper image with the IR cut filter.

However for the sharpest image use a IR pass even with the colour camera. It only lets the IR through. IR is less affected by the seeing conditions so results in a sharper but B&W image. (well its sort of purple until desaturated)

Best regards

Peter

[Tommohawk]

Here is my take on it.

First you need to get your head round the transmission curves for this camera, show  by this chart:

Note that the RGB matrix bleeds IR on all channels - lots of it. If you use an IR pass filter then obviously only IR will reach your camera. The ASI290MC is sensitive to IR (825nm) on all pixels so you will get a lovely IR image. IR is less affected by atmospheric turbulence so you can get good resolution, but obviously only mono. 

If you now remove the IR pass filter the RGB filters can now capture colour - excellent. BUT all the RGB pixels will also capture IR which will spoil your RGB image. So you  use an IR cut filter to  ensure your RGB is not contaminated by IR.

IR images are sometimes used as a luminance layer to give extra resolution to the image, but probably give little improvement when the target is at higher elevations - as Mars is now - because at that altitude there is not so much atmospheric turbulence - provided seeing is OK.

Other interpretations are available!

 

Edited October 1, 2020 by Tommohawk
Sp