infrared filter

Thanks Anto.

Your description of blocking versus pass filter has me confused:

I think for planetary and solar/lunar imaging, we wish an IR-blocking filter and not an IR-pass filter.

I would have thought that the desired item (as I read it) for enhanced planetary viewing/imaging would have been a pass filter?

What are the charachteristics required of an IR filter to be used for planetry ( and maby lunar) imaging?

I think for planetary and solar/lunar imaging, we wish an IR-blocking filter and not an IR-pass filter.

Most people have the Baader IR-blocker which is very cheap (in price).

I just checked the eBay listing and it is indeed a blocker ... I was thrown off by your comment about an "IR" filter which I took to mean an "IR-pass" filter. My apologies.

The price (22 pounds) seems a little high. I have seen the Baader version on UK Astro-Buy-Sell for much less!

Anyway, these (blocking) filters restrict the signal to the visible portion of the spectrum and exclude UV (just past the low end of the visible spectrum) and IR (just past the high end of the visible spectrum). Occasionally you see photos where bright stars have a "rich" rose- or purple-coloured ring around them and this is due to IR and which we seek to avoid by the use of such a filter.

thanks Anthony. ive been reading up on imaging mars though and everyone says to use an IR blocking filter to increase contrast and thus bring out more detail. thats why ive been looking at IR blocking filters. your advice is to steer clear yes?

If you have a problem with seeing, it is best to use an IR-pass filter (my Baader IR-Pass is for 685nm and up whereas my Baader Red Longpass is for 640nm and up). However, you will lose a bit in resolution since the greater details come with the shorter wavelengths (such as an IR-blocker or better yet with a green or ideally a blue filter).

If your seeing is good, I would suggest you stick with IR-blocking filter(s).

Thanks Anto.

Your description of blocking versus pass filter has me confused:

I think for planetary and solar/lunar imaging, we wish an IR-blocking filter and not an IR-pass filter.

I would have thought that the desired item (as I read it) for enhanced planetary viewing/imaging would have been a pass filter?

Here we have our personal biases (observing vs imaging) ....

Anyway, when using a shorter wavelength filter (ex. blue), we have the ability to capture (or observe) greater detail IF the seeing is good. If the seeing is poor, a means to combat it is to use a higher wavelength filter such as a Red Longpass (640 nm) or IR-Pass (685 nm) since these filters are not influenced as much by poor seeing.

Of course, there is the issue of our target. If it is the moon and which is monochrome, all of the above is fine but if our target is (colourful) Mars, we have a little problem during imaging since a blue filter will only yield a monochrome image. A partial way out of this mess would be to use an IR-blocking filter and a colour webcam. For just observing, we can use the appropriate filter and enjoy the monochrome view with the associated detail due to the filter in use.

I hope I did not confuse matters any further. :oops:

I understand it now Anto, handy to know these things!