Amateur Infrared Astronomy?

[Andonyx]

So I'm always looking for ways to observe and image the heavens, even when the clouds are not cooperating. I saw a few neat tutorials on how to re-purpose an old satellite TV dish into an amateur radio telescope. That sounds like a very cool idea, but a tad advanced for me at the moment. It did make me think, however about other ways to view, and I wondered about IR viewing.

I know this would probably only be useful on the big planets. I'm working with a C90, so anything after Saturn is pretty much out anyway. But I really enjoy solar observing / imaging, and I wondered if an IR imager would show variations on the sun's surface?

Everything I've read seems to indicate that IR viewing from the ground is kind of a lost cause. As I understand it, such a small percentage of light that makes it through the atmosphere is in the IR spectrum, that it's almost impossible to get any good images. 

I also figured that with my modest Glass solar filter, most of the remaining IR is removed as well.

Since I sometimes take photos with just a cell phone cam held up to eyepiece, I wondered if I could take some shots of the sun and moon using a cheap IR camera?

Is this a completely ill-conceived notion? Has anyone tried it? 

Your help and advice is appreciated in advance.

[riklaunim]

You are mixing various infrared wavelengths together.

For amateurs using CCD or CMOS sensors a small range of IR is accessible: 650-1100 nm. It's used for lunar imaging as well as on some planets (Jupiter, less often Saturn). On Venus there is 1010nm band at which night side emission is photographed and IR in general that can reveal some cloud details. On Sun it doesn't change anything in "white light" imaging.

From 1000 to around 2000 nm there is more scientific range of IR where professional use special infrared cameras (not cheap) to catch for example absorption bands on some planets, including Neptune or Uranus. It's not heat yet. You would have to pay at least around 10 000 EUR for an average InGaAs camera or alike to use this spectrum. Dedicated telescopes often use gold on mirrors to reflect more at those wavelengths.

At much longer wavelengths heat emission can be photographed. For astronomy water vapour in the atmosphere is the problem as it absorbs in that wavelength range (that's why they use Spitzer in space or Sofia on a plane). And you would need some good optics to handle those wavelengths.

[Andonyx]

Okay, that answers a few questions. So, of course I have more...

1. I found a consumer grade IR cam that uses a GaAs sensor and specifically states that it images "long wave" IR spectrum. The resolution is very low. That won't get me past the water vapor problem, but it's something.

2. So, in "visible light" solar viewing, this would be useless? Because nothing makes it through my solar filter, or because it's just not the right band for solar details? I'm guessing an H-A setup would also not work because that's so narrow already.

Thanks for the info!

[PeterW]

Solar, there are only a few bands worthy looking at, hydrogen, calcium and helium. Do you have more details of the camera sensor you have? You can get focal plane array sensors for 7-14micron wavelength, there is a cheap $200 one for phones from Seek Thermal just come out. The issue is that the resolution you would have would be poor as your scope is now much smaller in terms of aperture with spare spect to the wavelength you are using. Also all reflective optics are needed unless you have germanium or chalcogenide lenses....

Water vapour absorbs in specific bands, not all over the place.http://www1.lsbu.ac.uk/water/water_vibrational_spectrum.html But it does continue to get worse as you go into the IR.

connct it up and have a look, I know you can see the moon with 7-14um imagers... You see it in people's online thermal camera videos.

Cheers

PeterW

[ronin]

Need to search on atmospheric windows, then match the wavelength sensativity of the sensor to one or more of the windows, then I guess get a bandpass filter for that wavelength and window.

Use a suitable reflector to image with if you give it a go.

[riklaunim]

1. I found a consumer grade IR cam that uses a GaAs sensor and specifically states that it images "long wave" IR spectrum. The resolution is very low. That won't get me past the water vapor problem, but it's something.

InGaAs cameras are sensitive up to 1600-1800 nm on average. Those aren't that much blocked by water vapour. Scientific imaging is done within 1000-1800 but with narrowband filters and very large telescopes. With luck your camera could do some imaging on planets. Depends what it is and what it can do.