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Old 04-02-2010, 04:29 PM
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Infrared Astrophotograhy

Im thinking of have a shot at a night time terrestial IR photo composed with the sky in the same shot. The 87 filter I have, as shown in the attachment, shows it neatly cuts Ha out, so I can only hope for some exposure from stars fields and galaxys, being broad band scources. Has anyone tried an astro pic with a IR filter?, Is there enough IR light from stars thru the atmosphere to register an image?. This filter is very dense, and results in greyscale only with a modded DSLR. Im also assuming IR radiation from plants and trees in total darkness would produce an image , I havent seen examples taken at night with it.
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Old 04-02-2010, 05:41 PM
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I did some testsa couple of years ago using an IR filter.
Suprising how much data i got in 90 seconds of exposure, as apposed to 5 minutes using normal vision spectrum.

The camera was a QHY-8, but a modded Canon 20D etc, was just as good. In fact, with the UVIR filter removed, and using a small exposure time, i actually got the glow of heat from a soldering iron running at 400 DegC. It was cool to see the iron glowing in white light.

Anyway, heres the images, and it really is cool to see things that just dont come up on a normal image.

Theo.
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Old 04-02-2010, 05:55 PM
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OK, thats encauraging Theo, but I see some colour and neb there, which implies it passed Ha at 650nm odd, and well.........RGB, how is that possible with an IR filter, do you remember what the bandpass was?, or is it a blend?.

EDIT, ok, so the 1st image is without the filter?
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Old 04-02-2010, 05:56 PM
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What I'd really like to know is how they did this HH/Flame APOD in IR / tricolor that was posted not so long ago? That was a corker.
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Old 04-02-2010, 06:01 PM
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This?, link?
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Old 04-02-2010, 06:03 PM
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here it is.
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Old 04-02-2010, 06:12 PM
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Holy cow, thanks Marc, thats awesome. I cant workout if that was from a space cam, but anyway, it seems some other filters were used above IR to be able to create a false colour image, tricky. They mention ionised Ha too, so that must be in the pic band width.
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Old 04-02-2010, 06:14 PM
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It was a 970 from memory, so much higher than H.A, and you may find that the Neb glow is IR.

Theo.
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Old 04-02-2010, 06:21 PM
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Ah ha, so there is neb glow other than Ha, interesting. Well, IR radiates from heat, so that makes sense, thats about all I know.
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Old 04-02-2010, 06:22 PM
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Quote:
Originally Posted by Gama View Post
It was a 970 from memory, so much higher than H.A, and you may find that the Neb glow is IR.

Theo.
Our QHYs wouldn't pick anything around 970nm would they?
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Old 04-02-2010, 06:26 PM
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No filter DSLRs do
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Old 04-02-2010, 06:29 PM
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Quote:
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No filter DSLRs do
Peltier cooled otherwise you'll be shoveling noise like a concrete mixer
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Old 04-02-2010, 06:35 PM
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Well, thats true, but I was thinking terestial IR with some stars in the background with stock DSLR lens, 5 mins max (with no wind).
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Old 04-02-2010, 10:37 PM
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I take lots of images through a "I" photometry filter.
The passband is in this graph.
http://www.astrovid.com/other_images...ilterchart.jpg
Using my ST10XME the exposures need to be about 50% longer than R to get equivalent levels in the image but they are much brighter than B or G exposures.
As for terrestrial imaging. I remember using IR film and it worked best with bright sunlight. Green things like trees reflected lots of IR but needed bright sunlight to do this. Images were very washed out if it was overcast.
I don't think that you would get much at night.
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Old 05-02-2010, 12:47 AM
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Quote:
Originally Posted by multiweb View Post
Our QHYs wouldn't pick anything around 970nm would they?

Not at Max sensitivity, but they are sensitive to IR.

Both images are from the QHY-8, but i always use a "Clear" filter, and not a UVIR filter.



Theo.
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Old 05-02-2010, 08:28 AM
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Quote:
Originally Posted by Terry B View Post
I take lots of images through a "I" photometry filter.
The passband is in this graph.
http://www.astrovid.com/other_images...ilterchart.jpg
Using my ST10XME the exposures need to be about 50% longer than R to get equivalent levels in the image but they are much brighter than B or G exposures.
As for terrestrial imaging. I remember using IR film and it worked best with bright sunlight. Green things like trees reflected lots of IR but needed bright sunlight to do this. Images were very washed out if it was overcast.
I don't think that you would get much at night.
Thanks Terry. Pity about terrestial, but what you say makes sense. The I filter is above Ha, so I might give this filter a shot with the ST10, It would allow a different colour pallet with other NB filters.
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