Practical Amateur Spectroscopy like many books is not perfect - sure there are some typos and errors but I have a errata available. Notwithstanding the poor press it is a very good introduction to spectroscopy and compliments well my new "Astronomical Spectroscopy for Amateurs" - recommended.
OK I ran one of the images (052) through IRIS cropped and saved as a .fit file - imported into Vspec and selected what I thought were "real" features; the G band at 4308A and the Na doublet (not resolved) at 5895A to give a first calibration - this was then compared with a G2V spectrum....
The attached result shows the change in intensity across the spectrum due to the Bayer Matrix (Blue curve) and some absorption lines - the purple curve is a G2V comparison.
Yes, there is some detail there, but go back and compare this with the Baader grating/ needle results.....
Certainly an interesting start! (I'm glad I marinated those daks!)
Thanks so much for your advice, Rob. I tried the spectroscope out on the Sun Friday morning by using it to look firstly at a piece of white paper taped to a wall facing the Sun: no luck, just a continuous spectrum. The I turned the spectroscope to the reflection of the Sun in a glass door and the bright (almost too bright, but tolerable) reflection was replete with dark lines! I compared them as best as I could with the Wikipedia "map" of lines and thought I could identify the major ones. I was stunned at how prominent the lines were, like the gaps between tracks on an old LP (now you know how old I am), only more frequent and more irregularly spaced. I cannot think that these dark lines, running parallel to the arcs of the background spectrum, can be anything but dark absorption bands. Is that right?
The needle spectroscope will be much, much easier for the students to make and use, so I'll get to that this weekend. The image looks like it might be of poorer quality to the DVD spectroscope, but I need a method that is simple and easy for teenage students. Thanks so much for the tip.
Cheers,
Geoff Mc
p.s. Also tried the spectroscope on sodium lamps on the way home last night: brilliant! Interesting, amid all the bright transmission lines was one, lone absorption line. Any ideas?
Nyeh, bodgeyed up a 'sewing-needle spectrometer' this afternoon and gave it a go, using a Star Analyser grating & Canon 400D. Not really successful - a few faint absorption lines showing though.
Too much cloud & the Sun's low in the trees now. Might have another go with it tomorrow, with a CD.
Actually that's not too bad a result!
What lens were you using?
You'll get a bit more dispersion with a longer focal length telelens - 135mm or even a 200mm.
Have you tried to obtain a profile in Vspec yet?
Actually that's not too bad a result!
What lens were you using?
You'll get a bit more dispersion with a longer focal length telelens - 135mm or even a 200mm.
Have you tried to obtain a profile in Vspec yet?
Thanks Ken. I was using an 18-55mm lens at 55mm. This was a rough job, LOL - I was holding the cardboard sheet at arm's length while looking through the viewfinder of the camera. In my other lens (55-200) I couldn't get focus at 55mm, let alone 200mm!
Might have to actually set this up, rather than have things waving in the wind.
Anyway, I did graph it and it doesn't come up all that well. Some of the main Fraunhofer lines are there, but not others. Montage attached.
Hmmm
Not sure about that calibration...
BTW why the pink region in the blue?
The standard Canon UV-IR filter "dies" around 380nm and 720nm
Good question Ken, no idea why the pink - and agree about the calibration.
Anyway, for the purposes of the exercise I had a shot with a CD today. It did throw a spectrum of sorts - to photograph it I had to use a little auto point-&-shoot camera to get close enough. Autofocus snapped on the CD so I had to get focus on the needle then pan the camera across & shoot. Not ideal & focus could have been better but nonetheless did get something - see attached.
So feasible to get Fraunhofer lines in a solar spectrum with just a needle, a bit of cardboard, a CD and an ordinary p&s camera.
Also had another go with Star Analyser & 400D - more lines showing. Each spectrum has the full frame above, to give an idea of what the set-up was (rough!!!).
Still poor resolution with the CD - would be interesting to see your SA100 results with a 100mm+ lens...
I think the line in the green is the G band and the line in the red the atmospheric Telluric...this would then give you (?) the Na lines in the orange.....
Still poor resolution with the CD - would be interesting to see your SA100 results with a 100mm+ lens...
I think the line in the green is the G band and the line in the red the atmospheric Telluric...this would then give you (?) the Na lines in the orange.....
I have to stress that what is seen with the naked eye on a CD(the DVD was even better) spectroscope,is extremely clear, sharply defined dark lines :
1 in violet
2 in blue
6 in green
3 in yellow
2 in red
These are the obvious..............but there a numerous fainter ones.
As per Rob_K's post(link on post number 20), the image of the last solar spectrum of three with the lines labelled, is EXACTLY what I see visually with a CD spectrum.............so what gives here guys.......there is no ''hashy'', rough as guts ''dirty'' looking spectra........just a smooth one with many, many lines????
This is all with a reflective(not transmissive) grating at an an odd angle with a very dodgy slit, and viewing hole.......no lenses or cameras, needles
The camera attempt to take an image was a complete joke as I didn't have access to a top of the line Canon DSLR, and it's a surprise that I captured anything at all.The images I posted were not only out of focus, but also distorted due to the angle required to see the spectra within the camera(thus the ''uneven'' focus also)
Yes, definately Merlin.
It's all fun to see how much can be obtained from a crappy CD, but it's not a serious grating if I decide to point it at the stars.
As per Rob_K's post(link on post number 20), the image of the last solar spectrum of three with the lines labelled, is EXACTLY what I see visually with a CD spectrum.............so what gives here guys.......there is no ''hashy'', rough as guts ''dirty'' looking spectra........just a smooth one with many, many lines????
This is all with a reflective(not transmissive) grating at an an odd angle with a very dodgy slit, and viewing hole.......no lenses or cameras, needles
Yep Rob, sorry, I wasn't casting nasturtiums on or ignoring your method - I intend to go there when the Sun comes back!
The reason for going the needle first was that it acts like a slit and is highly reflective, like a mirror. Mind you, the needle I chose was ROUGH!!! It would work a lot better with a smoother needle. I'd still be a little worried that a surface like the side of a white shed might or could introduce absorption lines of its own, depending on the surface composition. And that might vary from white-shed to white-shed. But those could easily be weeded out. I was super-impressed with what you put up!
Hey no problem or offense taken Rob_K..........none at all.
It's interesting when you mention different types of white sheds/walls and their possible influence on the spectral lines........never thought of that.
White paint has : Titanium dioxide, calcium, silica, zinc oxides, talc,binders etc.(all depending on what type of paint is used and the condition or oxidisation level).
So, spectroscopes are designed to reveal these elements and any others that make the so called ''white light''.
A reflective needle will be far truer towards ''solar light'' than a white painted wall no doubt
I will repeat this little exercise with a shiny needle and try to photograph the results using a CD based spectroscope.
The amateur spectroscopes we're talking about are not sensitive enough to do the sort of analytical stuff being discussed.
Most surfaces will re-radiate the solar energy into the IR; you could take a spectrum and then compare it with a standard G2V to see any differences...this method is successfully used to show the methane absorption bands in the gas giant planets.
I am a complete new-comer to this business, so appreciate everyone's expertise. Thanks.
Regarding the problem of reflections off walls, initially I used a reflection off a window to reduce the intensity. Yesterday I used a (new, glass) petri dish as a small reflector held in front of the slit of a DVD spectroscope (the design mounted inside a cardboard tube). The response was promising: easier than standing in the glare of a reflected solar image in a window. My goal is to mount the petri dish at 45 degrees to the slit, so that whatever the orientation of the Sun in the sky I am looking perpendicular to the line of sight. I have also started mounting the device on a tripod with slow motion controls for easier use.
It has also been suggested to me that many of the absorption lines are due to substances in Earth's atmosphere, and that these would need to be identified to distinguish them from those in the solar atmosphere.
The atmospheric or Telluric absorption lines caused by H20 and O2 are well mapped. Yes, these do have to be corrected for in the final analysis.
Spectral processing software like Vspec or RSpec have a very comprehensive library of these Telluric lines. (BTW they come in handy at times for calibration purposes)
OK, had a go with Rob's design this morning, modified to use a needle rather than aiming at a wall or other white surface. Didn't have a ready-made tube, and not willing to wait for the Glad Wrap to be used up I rolled up thin card with a sheet of black paper. Added a black paper 'shield' to cut down extraneous light entering the tube.
With the shield on, you simply tilt the "spectroscope" (ha!!) down at about 45-deg to the incident sun rays, look through the peephole and rotate the tube slightly until the Sun reflects 'squarely' off the needle. Awesome, very clear spectrum with so many fine strong absorption lines showing!! The needle used was finer & smoother than the one I used previously.
Photography is problematic & I won't even bother trying - this is just a simple, cheap way of introducing yourself (& students?) to the solar spectrum (and other bright light sources - good job on various lights around the house last night).
Excellent idea, Rob_K: I copied your replacing the slit with a needle and the spectroscope is far easier to use on the Sun. Very fine absorption lines. It is less effective than the slit design on lights, however (at least mine is). This means I now have a design I can get students to make and use as an introduction to solar spectroscopy.
Credit to you guys, of course. May I use your names? It is for a teaching unit I am developing for uni, all not for profit; just sharing ideas on how to teach Year 11-12 students about the Sun from an observational approach. I like to give credit where credit's due.
It is less effective than the slit design on lights, however (at least mine is).
Same here Geoff, because the lights are so much less intense than the Sun. But still shows the emissions OK.
Quote:
Originally Posted by Geoff Mc
Credit to you guys, of course. May I use your names? It is for a teaching unit I am developing for uni, all not for profit; just sharing ideas on how to teach Year 11-12 students about the Sun from an observational approach. I like to give credit where credit's due.
Geoff Mc
No credit due here Geoff, all down to Robz I reckon. And when it all boils down, all these 'designs' (and probably anything else you could possibly think of!) have been played with for aeons!!
Weakened and tried to get a photograph of the spectrum but it nearly drove me mad! Did get the attached but it just doesn't do the visual view justice, there are so many more fine lines that didn't come out.
.............so what gives here guys.......there is no ''hashy'', rough as guts ''dirty'' looking spectra........just a smooth one with many, many lines????
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