Trifid in near infrared

[Stevec35]

This is something different and slightly experimental so don't judge too harshly. A few years I bought some Astrodon infrared filters and this is one of the few times I've used them. Basically these filters have the following characteristics:

Luminance - only passes greater than 700nm
Red - a band centered on 850nm
Green - a band centered on 830nm
Blue - a band entered on 750nm

You will notice that the bright stars look pretty messy. According to Don Goldman that's because the anti-reflection coatings on the CCD cover slip are only optimized for visible light and not infrared.

Anyway here's the image:

http://members.pcug.org.au/~stevec/M20_STXL6303_RC14.htm

Steve

[Merlin66]

Very interesting.
Imaging in "unusual" wavelengths should be encouraged, the information obtained in the UV or NIR is completely different from the "usual" LRGB.

I'm not sure about Don's comments......
In spectroscopy we use a wide range of CCD cameras, SBIG, ATIK, QHY etc and our spectral images cover from 3600A way out to beyond 8000A I've never hear of any issues/ concerns with the CCD chip cover plate coatings.
(Do do have problems with newton ring type resonance bands with some wavelengths/ camera chips)

[Stevec35]

Yes I find IR imaging interesting. I've just finished a very interesting book on the history of infrared astronomy. As far as the bright star artefacts are concerned I'm just relating what Don told me. I've only ever noticed this effect with the IR filters. Apparently Don doesn't sell these filters anymore except for the NIR luminance.

[Merlin66]

Steve,
Which telescope and camera combo do you use?

[Stevec35]

It's mentioned in the image caption. STXL6303 camera with 14.5" RCOS Ritchey Chretien telescope.

[Merlin66]

Ahhh
I only clicked on the thumbnail image.......

[cometcatcher]

That's very cool.

I should try this with my OSC DSLR and 720nm filter.

[atalas]

Yep! many more stars revealed through the dust....very cool :thumbsup:

[Atmos]

Really interesting Steve.
The IR filters have made an interesting colour but it is nice and contrasty :)

[marc4darkskies]

Well THAT'S and interesting take! Look at all those "extra" stars! Fascinating! Well done Steve!

Have you played around with the palette so see what other colour outcomes you could get?

[RobF]

Interesting image Steve.

[Stevec35]

Thanks Rob



Thanks Martin. No I haven't but that might be an interesting exercise



Thanks Colin



Thanks Louie - sounds like an infrared pun



Thanks. The effect varies depending on what you're imaging. The Lagoon is worth a shot but most star clusters don't look all that different than visible.

[topheart]

Hi Steve,
Well that is different ....It has a ghostly sort of feel.

Cheers,
Tim

[Placidus]

Had to go away and find a good RGB Trifid to compare with, before we could see what you'd achieved here. It's not the distant background, and it's not the very blackest nebulosity. It's the middling-dark bits of the nebula, where there are now far more stars.

Love to have some glimmering as to what the three different infrared bands tell us. The only pattern I can see is that the bit closest to the very bright stars in the centre of the Trifid is "bluest", and hence highest temperature, of the three infrared wavelengths.

Conversely, the reflection nebula doesn't seem especially strong in infrared, which perhaps makes some sense if the blue part of the starlight is scattered back off the reflection nebula, but the infrared part of the starlight goes straight through and is never seen again.

Great work, and thanks for giving us something to puzzle about.
Best,
Mike

[Peter Ward]

Nice one Steve :thumbsup:




You'll simply have a monochrome image biased toward the I/R...it won't look the same as Steve's fine rendition.

[Ryderscope]

Good one Steve. It certainly provides other avenues to explore.

[cometcatcher]

That's correct. I was thinking of adding something for a bi-colour image with 720nm ir as one of the channels. It still won't be as nice as Steve's. DSLR's lose a lot of sensitivity down there.

[Stevec35]

People might be interested in this reply I got from Don Goldman about the availability of IR filters.

Steve

"Hi, Steve,

You can post this on the ccdastro group if you like.

We discontinued the NIR set due to lack of interest, but, as you say, still get requests for a NIR Luminance, essentially a NIR long-pass filter, so we do stock this filter in all sizes.

Another part of the reason for discontinuing the NIR RGB is that you can do the same thing with 3 of our photometric sloan filters; i' for blue, z_s for green and Y for red. Please see the spectral profiles at:
http://astrodon.com/store/p12/Astrodon_Photometrics_Sloan_Filters .html
http://astrodon.com/uploads/3/4/9/0/34905502/s509074309854108831_p12_i5_w345.jpe g

Yes, typical A/R coatings are centered and optimized for green and often there is little A/R out in the NIR. As a result, you can indeed get reflections from the coverslip or chamber window in the NIR. Also, since NIR penetrates the CCD sensor deeper, especially for backthinned CCDs, you can get some weird banding."

[Stevec35]

Thanks Rodney - it certainly does. Of course not every object looks so interesting. Bright star clusters for example.



Thanks Peter. Not the first time I've done this of course. You might remember the saga of the IR globular of which I was declared the co-discoverer from a few years back.



Thanks Mike - nice analysis



Thanks Tim

[RickS]

Very funky, Steve :thumbsup:

[Stevec35]

Thanks Rick. Expect some more like this. Got to justify buying those IR filters.