IR Imaging?

[Gina]

I was wondering if there would be any benefit to having an IR wavelength response for DSO imaging ie. going beyond the normal IR cut-off of an IR/UV filter? I'm thinking of possibly removing the IR/UV filter as well as the colour correction filter on my 1100D. Maybe use an IR pass filter.

Any comments would be much appreciated, thank you

[Dave Smith]

I would also be interested in this, I have an IR pass filter but have only used it on the Moon.

Dave

[Merlin66]

Astrophotography and observations

Piotr (RIKLAUNIM) has done a lot of work with various filters, including IR pass filters.

[Gina]

Lots of great planetary and moon images on there but I couldn't find any DSOs. I have webcams with IR filter removed for planetary imaging and for the moon in sections. But what I really want to know is whether using an IR pass filter on a large high res sensor is going to have any uses.

[Merlin66]

Good question!

I would think there would be IR wavelengths involved in dusty nebula...

Can't honestly help, I only use it for spectroscopy.

[Gina]

Could be Though I gather the main emission gas is Hydrogen which resonates in the deep red rather than infra red. But I'm only quoting what I've read. Maybe there's an opening here to "Push The Frontier" OTOH I'm sure someone must have tried this. Mind you, I expect scientists and experimenters, inventors etc. have thought this in the past when new discoveries have been made.

[Merlin66]

There you go Gina....

To boldly go....

( dusty nebula must reflect in the IR, may be some interesting targets out there)

[riklaunim]

There are few images done with Astrodon NIR false-color RGB set. M42 looks like M42 (NIR set catches some nebulosity emission too - from exotic lines) but also it looks more transparent. I didn't saw any direct comparison to a standard image of a dusty area - but even that is "new thing" and not everyone can or tried catching the dusty stuff.

Astrodon Astronomy Filters - Articles & FAQ

M42 (IR 3 color) - FLC Observatory

The dust makes everything redder so in IR it should be even more obvious + lesser light pollution and lesser Moon problem. There are Astronomik ProPlanet filters, there are also Schott longpass filters (link) + much more expensive Astrodon and IDAS NIR RGB filter sets. That would work best with a mono camera with high IR sensitivity.

Standard DSLR without the internal IR/UV cut would be rather limited in performance. Those more modern have CMOS sensors that like to be red-shifted in QE - those would perform better and maybe even with all pixels (not only red).

[Tim]

I have been wondering this too Gina. I noticed that some very long exposures I took on M57 revealed detail that really stands out in IR pictures of the same target. So I wondered if an IR Pass filter would bring out further results.

One consideration is that the atmosphere pretty much goofs up IR signal though, which is one reason the big observatories dont bother, relying on images from Spitzer instead (NASA Spitzer Space Telescope)

The other thing that gets banded about is that strong IR light eg from stars will give you a bloated star image and spoil the picture.

I am under the impression that many CCD cameras have an IR cut window as standard. My QHY8 doesn't, but it doesnt have the best response to deep red anyway so am not sure it would help much.

What is it you are interested in achieving if possible?

Cheers

Tim

[Gina]

That's interesting. Thanks

Think I've decided then - the UV/IR filter stays out when I get to that stage Saves the tricky job of sticking it back in without getting glue where its not wanted too

Eventually I'll probably get one of these :- First Light Optics - Baader IR-Pass Filter It'll be of use with both DSLR and webcam

Some test exposures will be required to ascertain the focal difference between visible and IR light but I'm planning to add a counter to my electric focuser so that won't be a problem.

[riklaunim]

The other thing that gets banded about is that strong IR light eg from stars will give you a bloated star image and spoil the picture.

Thats when you have VIS and IR and they don't focus at the same point (or fast f-ratio makes some interference)

I am under the impression that many CCD cameras have an IR cut window as standard. My QHY8 doesn't, but it doesnt have the best response to deep red anyway so am not sure it would help much.

Many astro cams? rather not. Some machine vision cameras usually are filtered by default.

[MartinB]

IR adds significantly to a luminence image. Unfortunately if there is glass in the optical path you need to filter it out since even perfect apochromats aren't corrected for IR. One advantage of reflecting designs of telescope is that you don't need to block IR when capturing luminence data, it will be focused at the same point as the visual spectrum. When using an SCT or newt I use a plain luminence filter but use an IR block with a refractor.

I guess you could use an IR pass filter similar to those used for planetary imaging and create a false colour image or use a non IR blocking red filter and use it to enhance the red channel. Could be interesting.

[Merlin66]

"To boldly go........

[Gina]

I shall be "boldly going"... Nothing ventured, nothing gained!

[iwatkins]

Indeed. And do report back Gina. I would be interested in how you get on.

Cheers

Ian

[Beardy Bob]

I've read about turning webcams into IR cameras by removing the small glass IR filter in front of the sensor and replacing it with a section of 35mm film that has been exposed with the lens cap on (i.e. completely black). This blocks out all the visual spectrum and allows just the IR through.

[Gina]

Well, I didn't know that Umm... unexposed film is clear - black is produced by exposure to light (unless you're talking about colour reversal film - for slides).

Yes, I shall certainly report back Just need to get rid of these pesky clouds!! I have a big backlog of AP and testing piling up! We have filters available for all sorts of things... now we need a cloud filter

[laser_jock99]

The photos in this album:

FUJIFILM IS PRO pictures by laser_jock99 - Photobucket

were taken with a Fuji IS Pro infra red DSLR (which is basicaly just a Fuji S5 Pro with the IR blocking filter not fitted at the factory). They were marketed by Fuji as forensic/scientific cameras with possible astro applications (a bit like the rare Canon D20a).

In theory you could use these cameras to explore the longer wavelengths- I took this photo of the Gamma Cygni region through a deep red IR680 filter (something like 300 seconds @ ISO 3200 I think!!)

There are problems such as bloated stars, problems finding focus and high response to the UV end too. But it's well worth experimenting with these cameras.

[Gina]

Very interesting - thank you

What is it you are interested in achieving if possible?

Cheers

Tim

Nothing in particular, I was just wondering whether to enable my DSLR to be IR sensitive.

[Beardy Bob]

Yeah, that's what I meant, negative exposed to light so it's black.

[Beardy Bob]

How to Make a Webcam Into an Infrared Camera: 7 steps (with pictures)