Macro spectrum

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Lou Jost
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Macro spectrum

Post by Lou Jost »

Here is a macro photograph of the slit of a cheap little diffraction grating spectrometer, mounted on a 28-70mm tube lens as if it were an infinity-corrected microscope objective. The slit looks to be about 2mm long and a fraction of a millimeter wide. The light is natural light from the sun, and the camera is a full-spectrum-modified Sony A7R.
Full outdoor spectrum A7Rsmallest.jpg
The dark lines are Fraunhofer lines caused by single atoms and larger molecules in the sun's outer layers and in Earth's atmosphere; these have quantized energy levels and when light matches the energy difference between two levels, it is absorbed. Each line you see here belongs to a particular element.

So I guess you could say this is a macro photo of the sun...

iconoclastica
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Re: Macro spectrum

Post by iconoclastica »

Fascinating, this is!
Lou Jost wrote:
Sun Mar 12, 2023 2:01 pm
a cheap little diffraction grating spectrometer
What exactly is that?
--- felix filicis ---

MarkSturtevant
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Re: Macro spectrum

Post by MarkSturtevant »

That is pretty interesting. I bet the absorption lines reveal the presence of hydrogen.
Mark Sturtevant
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Lou Jost
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Re: Macro spectrum

Post by Lou Jost »

MarkSturtevant wrote:
Mon Mar 13, 2023 1:48 pm
That is pretty interesting. I bet the absorption lines reveal the presence of hydrogen.
Actually this photo shows lines from many of the known elements in the sun, including hydrogen, magnesium, sodium, calcium, and iron, plus some absorption lines from our atmosphere due to oxygen and water. Here are the main lines:
https://en.wikipedia.org/wiki/Fraunhofe ... diance.svg

and here I have overlaid that graph onto my spectrum photo:
https://www.cloudynights.com/topic/8660 ... p=12555752
Last edited by Lou Jost on Mon Mar 13, 2023 2:11 pm, edited 1 time in total.

Lou Jost
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Re: Macro spectrum

Post by Lou Jost »

iconoclastica wrote:
Mon Mar 13, 2023 12:11 pm
Fascinating, this is!
Lou Jost wrote:
Sun Mar 12, 2023 2:01 pm
a cheap little diffraction grating spectrometer
What exactly is that?
Here is something similar from eBay:
https://www.ebay.com/itm/320404890537?h ... R8Cut8vbYQ

rjlittlefield
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Re: Macro spectrum

Post by rjlittlefield »

Lou Jost wrote:
Mon Mar 13, 2023 2:03 pm
and here I have overlaid that graph onto my spectrum photo:
https://www.cloudynights.com/topic/8660 ... p=12555752
Lovely! And a very interesting discussion -- I read all 8 pages and I see it is continuing.

--Rik

Lou Jost
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Re: Macro spectrum

Post by Lou Jost »

rjlittlefield wrote:
Mon Mar 13, 2023 5:13 pm
Lou Jost wrote:
Mon Mar 13, 2023 2:03 pm
and here I have overlaid that graph onto my spectrum photo:
https://www.cloudynights.com/topic/8660 ... p=12555752
Lovely! And a very interesting discussion -- I read all 8 pages and I see it is continuing.

--Rik
The difference in what we might call "good faith engagement" between this forum and CloudyNights is amazing. Every thread I start there ignites a completely unneccesary firestorm. But after the storm passes, there are very knowledgeable and helpful people.

This is a related post I started on CloudyNights:
https://www.cloudynights.com/topic/8660 ... lor-again/
I think this spectroscopic analysis of the outputs of different camera sensors is relevant to us here.
https://www.cloudynights.com/topic/8660 ... p=12556834
Last edited by Lou Jost on Tue Mar 14, 2023 6:42 am, edited 1 time in total.

rjlittlefield
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Re: Macro spectrum

Post by rjlittlefield »

Lou Jost wrote:
Mon Mar 13, 2023 5:24 pm
This is a related post I started on CloudyNights:
https://www.cloudynights.com/topic/8660 ... lor-again/
I think this spectroscopic analysis of the outputs of different camera sensors is relevant to us here.
https://www.cloudynights.com/topic/8660 ... p=12556834
I think that's the same 8 pages that I thought was interesting and read all of.

Yes, very interesting analysis of the different camera sensors.

I noted also the post by Mark at https://www.cloudynights.com/topic/8660 ... ry12544406 , on the difference between Canon & Nikon (specific models) in the blue/green transition.

--Rik

Lou Jost
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Re: Macro spectrum

Post by Lou Jost »

rjlittlefield wrote:
Mon Mar 13, 2023 5:54 pm
Lou Jost wrote:
Mon Mar 13, 2023 5:24 pm
This is a related post I started on CloudyNights:
https://www.cloudynights.com/topic/8660 ... lor-again/
I think this spectroscopic analysis of the outputs of different camera sensors is relevant to us here.
https://www.cloudynights.com/topic/8660 ... p=12556834
I think that's the same 8 pages that I thought was interesting and read all of.

Yes, very interesting analysis of the different camera sensors.

I noted also the post by Mark at https://www.cloudynights.com/topic/8660 ... ry12544406 , on the difference between Canon & Nikon (specific models) in the blue/green transition.

--Rik

I see now, I thought you were looking at the other post I had started about this:
https://www.cloudynights.com/topic/8676 ... t-overlap/

Beatsy
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Re: Macro spectrum

Post by Beatsy »

Thanks for starting this thread Lou and the link to the CloudyNights forum. I read through all of that as well. Very interesting, once you get past the well-actually's. Your patience with them is commendable, to say the least.

I had another "aha" moment looking through the BX61 with the spectrometer. The BX came with all 6 filter-turret positions populated to support various forms of fluorescence microscopy. One position looked like normal brightfield when I first used the scope (I hadn't yet taken the filter turret out to look) but I got the impression it was more like watching TV than seeing clear, white-light illumination. I later found there were excitation/emission filters in that position, but accepted it as it was because it worked well enough (removing the filter cube made a difference, but didn't improve much other than remove the subjective "TV-look" and increase brightness). Blow me down, when I viewed this position through the spectroscope, it showed 3 distinct bands at R, G and B - much like my monitor does - albeit in much narrower bands with far "crisper" boundaries. No wonder it looked like TV! :D

While the spectral info is interesting and useful, I'd also like to get some information on relative intensity (actually transmittance) at the various wavelengths. To that end, conversion to monochrome works - but it's impossible to judge percentage differences from a grayscale image of the whole spectrum. Ideally, I'd like to select a line of pixels across the spectrum and turn that into a simple line graph with intensity on the y-axis, wavelength on the x. I thought Id be able to find some piece of software to do that but came up blank - so far. Any ideas? I only need to judge relative intensities between spectra shot on the same setup (varying illumination and the medium it passes through), so it doesn't need to be properly quantitative.

Cheers

Edit: Think I found a solution. The "intensity profile" feature in ImageJ looks like it will do the job. A bit more learning-curve in my near future though. https://imagej.nih.gov/nih-image/more-d ... ofile.html

Edit again: Hope you don't mind Lou, I pinched your spectrum pic to test this with. Raw data here, but done in minutes right after downloading ImageJ - and without reading any instructions either. Tthe tutorial I linked seems to be for an older version - so I just started "clicking around". Obviously I need proper units and axes suitably scaled/numbered etc, but this is enough to tell me ImageJ will do the job.
louspectrum.jpg

Lou Jost
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Re: Macro spectrum

Post by Lou Jost »

Very nice Beatsy. I calibrated (approximately) the x-axis of that graph in my CloudyNights post 156, but that was done simply by stretching a linear scale irregularly to fit the Fraunhofer lines. Not really exact.

Pau
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Re: Macro spectrum

Post by Pau »

Very interesting thread!

Aside the main subject, some marginal aspects are also of my interest, for example

- Your modified A7R shows the ultraviolet like reddish purple while my left eye (which became able to see into the UV after cataract surgery with an eye lens not filtering enough UV) sees it intense violet, clearly Sony and Pau have different sensors and processors :lol:

- At the link to cloudynights, member sharkmelley shows an interesting comparison between Canon and Sony/Nikon sensor in the blue-green rendering that seems to explain my impressions seeing landscape pictures
https://www.cloudynights.com/topic/8660 ... ry12556657
https://www.cloudynights.com/index.php? ... id=2267027
Pau

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Re: Macro spectrum

Post by Pau »

Beatsy wrote:
Thu Mar 16, 2023 1:06 am
I had another "aha" moment looking through the BX61 with the spectrometer. The BX came with all 6 filter-turret positions populated to support various forms of fluorescence microscopy. One position looked like normal brightfield when I first used the scope (I hadn't yet taken the filter turret out to look) but I got the impression it was more like watching TV than seeing clear, white-light illumination. I later found there were excitation/emission filters in that position, but accepted it as it was because it worked well enough (removing the filter cube made a difference, but didn't improve much other than remove the subjective "TV-look" and increase brightness). Blow me down, when I viewed this position through the spectroscope, it showed 3 distinct bands at R, G and B - much like my monitor does - albeit in much narrower bands with far "crisper" boundaries. No wonder it looked like TV! :D
This must be a triple-band fluorescence cube (pretty expensive!) like https://www.chroma.com/products/sets/89 ... citer-fish
Pau

Beatsy
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Re: Macro spectrum

Post by Beatsy »

It might be equivalent to the filter you linked Pau, but I still don't know much about it. The spectrometer told me a lot more than the serial numbers did :D

It's the "number 4" filter cube in this post. viewtopic.php?f=8&t=45518&p=285856

Looking at retail (and second hand) prices for these cubes, there's a few grand "worth" in there. I found good uses for three of them, though little to do with fluorescence. It's mainly just illumination filtering - to and from the specimen.

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Re: Macro spectrum

Post by rjlittlefield »

Lou Jost wrote:
Mon Mar 13, 2023 2:05 pm
Here is something similar from eBay:
https://www.ebay.com/itm/320404890537
I ended up buying one of these: https://www.ebay.com/itm/220692058016 . In quick tests it seems to work great.

Contrary to what it looks like in the eBay photo, most of the housing is cylindrical and not tapered.

It looks simple enough to mount, but of course the exit pupil is just that small hole at the end of the short conical section, and the angle of view seems pretty wide. In quick tests, it worked best just held in front of my cell phone.

Hoping to save some time I'll ask: how did you couple this thing to your big camera?

--Rik

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