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UltravioletPhotography

Multispectral Kalanchoe


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A little experiment using my astro-camera and UV, green and IR filters.

UV is the blue channel, Green is the green channel and IR (850nm) is the red channel :

 

post-136-0-28522100-1483997411.jpg

 

Nothing spectacular but I found the picture pretty nice. I have a registration problem tho.

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Very interesting combination, Martin! And tell me more, please. When we post photos, it is sometimes nice to include a bit of the information about the gear we made them with. What camera? What lens? Which filters? I'm especially interested in your green filter.

 

And do you know what this flower is? This is one I'm not sure about.

 

Tell me if I'm correct: you made 3 different fotos with 3 different filters and then channel stacked them? If so, then sometimes you can get the layers to match up using some of the layer adjustment tools. And I think Photoshop has a "stacking" tool which attempts to automatically match edges and so forth. Of course from long experience I know that our little flowers have a way of moving between shots making match-ups sometimes quite a challenge.

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Okay, I'll get it right next time I post a photo :)

 

The plant is kalanchoe blossfeldiana.

 

Camera : Zwo ASI120mm-s

 

Filters :

 

- Baader U

- Zwo 850nm IR filter

- Standart Meade green filter for astrophotography

 

You got it right Andrea, I made a photo of the plant with each filters and channel stacked them.

My camera is monochrome so I can't get false color using a single filter. By combining photos taken with different filters I am able to get a color picture.

 

IR

post-136-0-36366700-1484168223.jpg

 

Green

post-136-0-13433300-1484168225.jpg

 

UV

post-136-0-20161100-1484168224.jpg

 

 

The UV picture is pretty bad. The CCTV lens is very opaque to UV, I had to push the gain to the max. We can even see the reflection of the lens on the filter.

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Thanks! It is always good to learn about interesting gear like the Zwo.

 

The stack you made has a long tradition (although not in UV). There was a lot of old visible color photography made by stacking monochrome red, blue and green frames. Here is a link to the work of Prokhudin-Gorskii who used this technique.

http://www.loc.gov/p...background.html

He showed his work by stacking R, G and B slides in a "magic lantern". You can see the lantern in this link. We might have it easier these days using Photoshop!!

http://www.loc.gov/p...rok/method.html

 

The reflection in the UV frame might be mitigated by using a lens hood to prevent rays from entering the lens at an angle. Shiny filters like the BaaderU can sometimes be prone to this. But I've seen it on occasion with other filters also. If you don't have one, just try rolling up some thin cardboard or foamboard.

 

I was wondering if the green-pass filter might leak some IR? That green frame looks very bright! However, I don't really know this particular flower, K. blossfeldiana. So if it is not a pink or magenta colour then the brightness might be correct?

 

Aren't there CCTV cams which can record UV? Might be worth pursuing??

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Impressive how Prokhudin-Gorskii made those image with the technology available!

 

The green leaks IR but very poorly. In comparison my Blue Meade filter leaks a lot more and I can't do anything with it.

The flowers are originaly red with a pink tone like this one : http://image.noelsha...016572-1086.jpg

 

Concerning the CCTV lens there is a discussion about them on the forum. Those which works in UV are specialy made for that job and cost a lot. Almost every other CCTV camera is coated which reduces their UV transmission :(

I think the ASI 290 or 178 would be the best for recording UV light. Their sensitivity is very high (back illuminated pixels) and the noise is very low at high gain.

https://astronomy-im...b-3-0/asi290mm/

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oh man I'm losing track of my own forum!!! :lol: :lol: :lol: Sorry 'bout that. We started out so small and now we have so many posts! And we do indeed have some discussions of CCTV gear.

 

Relative to the price of a converted DSLR or mirrorless camera, the price of the ASI 290 seems reasonable. I've never had a CCTV camera or a telescope. But I would LOVE to be able to photograph Jupiter or Venus. Maybe someday I'll try to put something together for that.

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