Search found 193 matches

by thesmiths
Mon Mar 01, 2021 3:21 am
Forum: Solar Radio, Magnetometry and Spectroscopy
Topic: Zeeman effect in mercury using the home-made Fabry-Perot (with gifs!)
Replies: 2
Views: 20

Re: Zeeman effect in mercury using the home-made Fabry-Perot (with gifs!)

For those who want to understand the mercury Fabry-Perot lines better, I attach some diagrams taken from an excellent student science poster [Casey Wall, The Zeeman Effect in Mercury (2011). Summer Research. Paper 83]. The work was done with a high-resolution spectrometer using a 20-cm wide echelle ...
by thesmiths
Mon Mar 01, 2021 2:54 am
Forum: Solar Radio, Magnetometry and Spectroscopy
Topic: Zeeman effect in mercury using the home-made Fabry-Perot (with gifs!)
Replies: 2
Views: 20

Zeeman effect in mercury using the home-made Fabry-Perot (with gifs!)

To essentially wrap up our work on the home-made Fabry-Perot project, we improved the optics a bit so that we could observe the Zeeman effect in mercury. Mercury was harder than the previous study of helium because the structure of the splitting is more complicated, with many closely spaced lines. T...
by thesmiths
Tue Feb 23, 2021 6:32 pm
Forum: Solar Radio, Magnetometry and Spectroscopy
Topic: Zeeman effect in helium using a home-made Fabry-Perot etalon
Replies: 2
Views: 71

Re: Zeeman effect in helium using a home-made Fabry-Perot etalon

Here is a video of the helium red line through the #29 filter. It is a slightly different setup that maximises brightness in order to make a video so the lines are not quite as sharp as the setup above. You can see the interference fringes change from single to double as the polarising filter is rot...
by thesmiths
Tue Feb 23, 2021 2:54 am
Forum: Solar Radio, Magnetometry and Spectroscopy
Topic: Zeeman effect in helium using a home-made Fabry-Perot etalon
Replies: 2
Views: 71

Zeeman effect in helium using a home-made Fabry-Perot etalon

We have finished a fairly extensive study of the Zeeman effect in helium using the same Fabry-Perot interferometer and magnet used in our earlier study of Zeeman splitting in neon. The following series of photos shows the thought process behind the current experiment. First we looked at the spectral...
by thesmiths
Tue Feb 23, 2021 12:35 am
Forum: Solar Radio, Magnetometry and Spectroscopy
Topic: Testing a Lunt LS50FHa etalon with a H spectrum tube.
Replies: 14
Views: 390

Re: Testing a Lunt LS50FHa etalon with a H spectrum tube.

Peter: excellent work, as usual. In the very good paper by Cyril Bazin and Serge Koutchmy, "Photometric properties of new solar Ha commercial Fabry-Perot etalons", they state: We consider the use of the commercially available Fabry-Perot etalons (FP) of Sidorin and Lunt type for the imaging of the s...
by thesmiths
Thu Feb 18, 2021 1:34 am
Forum: Solar Radio, Magnetometry and Spectroscopy
Topic: Fabry-Perot etalon testing: Zeeman splitting of neon
Replies: 14
Views: 328

Re: Fabry-Perot etalon testing: Zeeman splitting of neon

To Peter: calibration with the sodium doublet is an excellent proposal. I have ordered helium and mercury tubes and will do measurements with them in due course.
by thesmiths
Mon Feb 15, 2021 11:34 pm
Forum: Solar Radio, Magnetometry and Spectroscopy
Topic: Fabry-Perot etalon testing: Zeeman splitting of neon
Replies: 14
Views: 328

Re: Fabry-Perot etalon testing: Zeeman splitting of neon

Dear Peter: That is very thorough and, from my point of view, a very satisfying analysis. You are quite correct, I made little in effort on this first attempt at collimation so the finesse likely suffered for this reason. There is also the lambda/10 issue of the mirrors, but my understanding is mirr...
by thesmiths
Sun Feb 14, 2021 11:21 pm
Forum: Solar Radio, Magnetometry and Spectroscopy
Topic: Fabry-Perot etalon testing: Zeeman splitting of neon
Replies: 14
Views: 328

Re: Fabry-Perot etalon testing: Zeeman splitting of neon

To Peter, thank you for you calculation. You're right, measuring the mirror spacing is tricky. Using callipers, I measured the outside spacing of the mirror mounts, subtracted the mirror thickness specified by Thorlabs and measured the amount of recess from the back of the mirror mounts. From this, ...
by thesmiths
Sat Feb 13, 2021 2:12 pm
Forum: Solar Radio, Magnetometry and Spectroscopy
Topic: Fabry-Perot etalon testing: Zeeman splitting of neon
Replies: 14
Views: 328

Re: Fabry-Perot etalon testing: Zeeman splitting of neon

To Peter: I tried to build a home-made integrating fluxmeter to measure the field. This involves wrapping some thin copper wire to make a small coil (around 10 turns) then looking at how much charge collects on an integrating op-amp when you move the coil from the peak magnetic field to a zero field...
by thesmiths
Fri Feb 12, 2021 10:57 pm
Forum: Solar Radio, Magnetometry and Spectroscopy
Topic: Fabry-Perot etalon testing: Zeeman splitting of neon
Replies: 14
Views: 328

Re: Fabry-Perot etalon testing: Zeeman splitting of neon

The effect of rotating the polarising filter is more apparent in the video of the experiment:
by thesmiths
Fri Feb 12, 2021 10:52 pm
Forum: Solar Radio, Magnetometry and Spectroscopy
Topic: Fabry-Perot etalon testing: Zeeman splitting of neon
Replies: 14
Views: 328

Fabry-Perot etalon testing: Zeeman splitting of neon

Continuing the exploration of our home-made Fabry-Perot etalon, we use it as an interferometer to observe Zeeman splitting. This phenomenon is the very small effect which splits spectral lines when in a magnetic field. It can, for example, be seen in spectral lines near sunspots, and the magnitude o...
by thesmiths
Wed Feb 10, 2021 7:56 pm
Forum: Solar Radio, Magnetometry and Spectroscopy
Topic: A hydrogen spectrum tube-- for fun and etalon testing
Replies: 20
Views: 387

Re: A hydrogen spectrum tube-- for fun and etalon testing

To Terry: I'm not quite sure what the first item is; it is not well described in the listing. The second item is a quite standard spectrometer. It will be rather big and heavy. I actually bought a similar one many years ago used on eBay to learn about spectroscopy but it was only useful at the begin...
by thesmiths
Wed Feb 10, 2021 1:27 pm
Forum: Solar Radio, Magnetometry and Spectroscopy
Topic: Home-made Fabry-Perot etalon project
Replies: 5
Views: 109

Re: Home-made Fabry-Perot etalon project

We also put some video data on YouTube so you can see the "scanning" of the etalon, done by hand by lightly squeezing the mirror mounts.



by thesmiths
Wed Feb 10, 2021 12:51 am
Forum: Solar Radio, Magnetometry and Spectroscopy
Topic: Home-made Fabry-Perot etalon project
Replies: 5
Views: 109

Home-made Fabry-Perot etalon project

In my previous post on hydrogen, sodium and neon light sources, I mentioned we would use these to test existing etalons, but the plan was also to experiment with our own home-made ones. Here is a progress report on our initial experiments. I reference first of all a nice article by Thomas Moses [Am....
by thesmiths
Sun Feb 07, 2021 2:35 pm
Forum: Solar Radio, Magnetometry and Spectroscopy
Topic: A hydrogen spectrum tube-- for fun and etalon testing
Replies: 20
Views: 387

Re: A hydrogen spectrum tube-- for fun and etalon testing

As another improvement to the hydrogen spectral tube to make it more etalon friendly, I attached some Rubylith plastic film on the inside of the foamboard underneath the diffusion screen. Rubylith, which is often used in darkrooms, etc, has about the same transmission as a 25A red photographic filte...
by thesmiths
Sun Feb 07, 2021 3:21 am
Forum: Solar Radio, Magnetometry and Spectroscopy
Topic: A hydrogen spectrum tube-- for fun and etalon testing
Replies: 20
Views: 387

Re: A hydrogen spectrum tube-- for fun and etalon testing

Finally, some photos of a PST etalon in front of the hydrogen tube. First, with no filter in front of the tube (only a diffusion screen, obtained from an old 35mm slide copier): 4199.jpg In this case, both the hydrogen alpha and beta light is sent into the etalon. The etalon surfaces are obviously o...
by thesmiths
Sat Feb 06, 2021 5:48 pm
Forum: Solar Radio, Magnetometry and Spectroscopy
Topic: A hydrogen spectrum tube-- for fun and etalon testing
Replies: 20
Views: 387

Re: A hydrogen spectrum tube-- for fun and etalon testing

To Stu: yes, I have used RSpec. Do you find this is the best program to use for spectroscopy tasks? Here, for example, is a high resolution image of the sodium doublet. This was actually not done with the sodium lamp but rather the old fashioned way, burning salt with a butane kitchen torch (apparen...
by thesmiths
Sat Feb 06, 2021 4:34 pm
Forum: Solar Radio, Magnetometry and Spectroscopy
Topic: A hydrogen spectrum tube-- for fun and etalon testing
Replies: 20
Views: 387

Re: A hydrogen spectrum tube-- for fun and etalon testing

I had always seen the potential utility for having a hydrogen source but was deterred by the high cost (around $200 for the tube plus the power supply). But the cost of the tube alone is only around $20 and a neon power supply is less than $15. This makes the cost/benefit more sensible. By the way, ...
by thesmiths
Sat Feb 06, 2021 3:43 am
Forum: Solar Radio, Magnetometry and Spectroscopy
Topic: A hydrogen spectrum tube-- for fun and etalon testing
Replies: 20
Views: 387

Re: A hydrogen spectrum tube-- for fun and etalon testing

To James: yes, low pressure sodium (LPS) is by far the most astronomy friendly light source. As you can see from the spectrum, almost all the light is concentrated in the sodium doublet. They used to be quite common in Europe (I don't think they were used too much in the US). First they were replace...
by thesmiths
Fri Feb 05, 2021 9:28 pm
Forum: Solar Radio, Magnetometry and Spectroscopy
Topic: A hydrogen spectrum tube-- for fun and etalon testing
Replies: 20
Views: 387

A hydrogen spectrum tube-- for fun and etalon testing

I've recently gotten hold of a few common spectral sources to do spectroscopy experiments -- a low pressure sodium lamp, a neon tube and most recently a hydrogen tube. These are nice tools for spectrometer calibration and testing and they are fun to play with as well. The light they produce is quite...
by thesmiths
Tue Dec 29, 2020 1:54 am
Forum: Solar Scope Modifications
Topic: Evaluating the PST etalon with a neon bulb
Replies: 15
Views: 483

Re: Evaluating the PST etalon with a neon bulb

I attach an image of the neon spectra which shows the six visually bright spectral lines near the strong yellow line at 5853 angstroms. These are the lines that form the repeating concentric rings of the Fabry-Perot interference pattern in the image at the top. 3823.jpg The spectrum was taken on the...
by thesmiths
Mon Dec 28, 2020 3:24 am
Forum: Solar Scope Modifications
Topic: Evaluating the PST etalon with a neon bulb
Replies: 15
Views: 483

Evaluating the PST etalon with a neon bulb

I stumbled upon this effect while working on something other than astronomy (Zeeman effect, in case you ask). I took the PST hydrogen alpha etalon I had around from a mod a few years ago and put if in front of one of those small neon bulbs. If you position the etalon with the camera side facing the ...
by thesmiths
Mon Jul 03, 2017 6:37 pm
Forum: Great American Solar Eclipse August 21 2017
Topic: Telephoto lens or short refractor?
Replies: 4
Views: 2760

Re: Telephoto lens or short refractor?

Mark, in another post you wrote: "I'm probably going to use a DSLR and a 70/420mm refractor for my travelling setup." Did you change your mind? I actually thought around 420mm on a crop DSLR camera was a perfect compromise. I think that's was Alexandra is planning on using. The Tecnosky 65Q 420mm qu...
by thesmiths
Sun Jul 02, 2017 1:37 am
Forum: Great American Solar Eclipse August 21 2017
Topic: Telephoto lens or short refractor?
Replies: 4
Views: 2760

Telephoto lens or short refractor?

Now that it's getting close, I am considering my options. Flying from Europe suggests travelling light. I did a dry run today with a Canon EF 300mm F4 IS camera lens vs an APM 480mm F6 telescope. The camera was a Canon EOS 100D. In terms of solar image size, I can see that the wider field of view of...
by thesmiths
Sun Jul 02, 2017 12:37 am
Forum: Great American Solar Eclipse August 21 2017
Topic: Using eclipse images to capture gravitational lens effect?
Replies: 3
Views: 2198

Re: Using eclipse images to capture gravitational lens effect?

In the famous observation of 1919, there were actually two expeditions: one to Sobral in nothern Brazil and a second to the island of Principe, about 120 miles from the African coast. In Sobral, the eclipse took place around noon UTC, so about 8am local time. This meant they only needed to wait a fe...