Second attempt at solar spectroscopy -- now with video! (and Ca, Mg and Na spectra)

[thesmiths]

There's not too many postings in the spectroscopy category, so my "first attempt at solar spectroscopy" posting should be easy to find. In that one, I used a Paton Hawksley spectroscope which I bought to look at chemicals in flames. Those experiments (both chemical and solar) were so intriguing, I then bought a real spectrometer on eBay (for 50 pounds plus 15 pounds postage). This one was made by Phillip Harris Ltd, I think in the 1960's for university chemistry courses.



I also bought a 600 lines/mm grating from Paton Hawksley. I assume this is essentially the same grating that is in their spectroscope.



With the spectrometer I found when burning sodium chloride, it was now possible to distinguish the sodium doublet lines quite clearly. With the spectroscope, the sodium lines looked like a single very bright line.

I then turned my attention to solar light. I used a cosmetics mirror to reflect the sunlight onto the slit (since the spectrometer is fairly bulky and quite heavy). The first challenge to get very fine resolution is having a good slit. Unfortunately, the adjustable slit on this model had developed some rust so the lines were quite non-uniform. I used some sandpaper and some other tricks and this did improve things somewhat, enough for visual observation at least. I was immediately staggered by the sheer number of lines that were visible. While with the spectroscope I could make make out around 100 lines in total, with spectrometer there were thousands visible. It was like being in a forrest, and that made it very difficult to figure out at first which tree (spectral line) was which.

As with any telescope, taking an image is much harder than visual observation. I removed the eyepiece focuser part and put my DMK41 with a 1.25 inch nose piece on the telescope (prime focus). The fit was close enough to keep out stray light and I could focus manually by sliding the camera back and forth. By the way, the whole spectrometer was inside the cardboard box in which it was sent to me by the eBayer (with holes cut out for the collimator and the telescope). I took some videos using the DMK41 and then actually used Registax6 and Photoshop (old habits, I guess). After processing, this gave a fairly good representation of what the eye can see:



I think the two very dark vertical lines near the middle are the sodium doublet, but I'm not 100% sure. As I said, it's very easy to get lost in the forrest. Red is to the right and blue to the left. The horizontal bands are from the uneveness in the slit. I tried to make the slit very narrow and there is a trade off with the horizontal banding problem and the vertial line sharpness. The uneveness in brightness is because of the uneveness of the illumination (cosmetics mirror, after all). This is actually a fairly narrow portion of the whole spectrum, from green to orange, I think. But you can clearly see the vast number of solar lines.

[Merlin66]

Well done!
Yes, the 600l/mm will easily resolve the Na pair (and show the Fe line between!)
There are many solar spectrum atlases available to assist in the identification of lines...
http://bass2000.obspm.fr/solar_spect.php

[swisswalter]

Hi Douglas

fine gear and report. That is a good start

[Merlin66]

I should have said I have a very similar "educational" table top spectroscope.
If you can pull the slit jaws off the housing, they can be polished using a glass plate and jewellers rouge...there should be a very slight "face" left on the bevel to give a clean and tight closure....
Align the collimator and imaging telescope to bring the slit image central (you can also re-set the angular scales...) and vertical.
When the grating is set in it's holder make sure the grating grooves are sitting vertically and the height of the table brings the optical axis of the telescopes to the centre of the grating area..( There should be no tilt in the absorption line) When you rotate the table there should be no up and down movement of the spectrum ( adjust the three spring loaded screws to bring it level)
If you get these adjustments correct, you'll get maximum resolution from the instrument.
Hope this helps.

[marktownley]

Cool stuff!

[colinbm]

Beautiful work Douglas. Keep it up.
Col

[Montana]

WOW well done

Alexandra

[thesmiths]

Thanks for all the positive comments. Actually, the coolest part is being able to scan the solar spectrum in real time. I prepared a video from the DMK avi (500MB!) that shows this (in B&W, colour is a lot nicer but even harder to capture). I reduced the video in size and posted to YouTube. I'll try to embed the video here. Again, blue is to the left and red is to the right. Lots of dust visible! The jpg shown above is from the beginning of the video. One of the lines to the right is definitely hydrogen alpha!

[video width=425 height=344 type=youtube]mZpctb9rW58[/video]

[Merlin66]

Well done!
Shows what extensive detail there is to be seen in the solar spectrum.
If you go further into the blue/ UV you may pick up the Ca lines (H&K) - the three lines seen at the beginning are the Mg triplet.
I think your grating/ slit alignment is a bit out (tilted lines...)
The next stage is to do a wavelength calibration!
Onwards and upwards.

[thesmiths]

To Merlin: I've amended the video to show more of the whole spectrum. The first half is primarily the yellow to red part of the spectrum while the second half is mainly green to violet. At the very end, the two calcium lines are clearly visible. Yes, I think the magnesium triplet lines are fairly easy to make out.

In fact, everything is fairly out of alignment since the light itself was not being bounced (from the mirror) parallel to the collimator tube axis. I did tweak the grating stage to try to compensate -- but then the sun moved!

[Merlin66]

It's a bugga when the sun moves ;-)
Onwards and upwards.

[thesmiths]

The video above spans from the calcium K H lines on the left (violet) to what I think is the oxygen A line on the right (infra-red).



The image below is from the beginning of the second half of the video which focuses on the green/blue part of the spectrum. On the right is what I think is the magnesium triplet. The dark line in the middle is, I think, the hydrogen F line (hydrogen beta at 486.1 nm).



Finally, the image below is from the very end of the video. The two very dark (and surpringly broad) lines to the left of center are the calcium K and H lines.





Attached files

[swisswalter]

Hi Douglas

fine results in that second attempt

[Montana]

These are fabulous pictures!



It would be nice in colour, you could photoshop a colour gradient in

Alexandra

[Merlin66]

When you calibrate for wavelength, programs like Vspec will automatically provide a colourised version....

[solarchat]

I think that this is just awesome Doug.. I hope I got your name right.

I really wanted one of those Shellyac spectroscopes to add to my outreach program a couple years ago but the guy wouldnt come down off of $2500 for one and I just couldn't justify it using nonprofit funds.
I bought one of his hand held spectrascopes for $120 and have used it at over 200 schools since then. I pass it around to the students and they look through it and see how it matches the spokes on my solar van rims.
know I could make one but the Shellyac version just mounts like a telescope and works so safely.

[Pedro]

Great stuff Doug, I'm impressed

best regards

[colinbm]

Hi Stephen,
I don't know what you mean by Shellyac Spectroscope ?
Col

[Montana]

Congratulations on pic of the day!

Alexandra

[Merlin66]

Shelyak Instruments are the french suppliers of commercial spectroscopes. They sell four models - lhires lite, a simple grating type for schools, the lhiresIII - high resolution, LISA - low resolution and a research grade eShel type.
http://www.shelyak.com/?lang=2

The other commercial suppliers are Baader (DADOS), Elliott (CCDSpec)and Paton Hawksley (Star Analyser)and Rainbow Optics (RO200) for transmission gratings.

[solarchat]

what he said...

http://www.shelyak.com/rubrique.php?id_rubrique=6


I looked through it and it was incredible. I would very much like to expand our program to include spectroscopy but I dont make my own stuff due to safety concerns. This product is just too expensive for the outreach to buy right now although I am very much considering buying it with personal funds and donating it, like I did with all the original equipment.

[swisswalter]

Hi Douglas

congratulations on the pic of the day

[thesmiths]

Wow, picture of the day. I am indeed honoured. I once came 2nd in image of the month on ukastroimaging. But this is way better. :thanx: . Next time I try this I'll do a complete mosaic of violet to infrared, calibrate the wavelengths and add the false colour. I've got the software, just need the sunlight and some free time. Thanks also to my son Andrew for assisting me on this project.

[MapleRidge]

Awesome work there Doug :

Well done!

Brian

[Merlin66]

Doug,
I should have mentioned Tom Field's RSpec as a great, and easy spectral processing package.
Well worth checking out. There's a 30 day "try before you buy"...
http://www.rspec-astro.com/