Affiliation
American Association of Variable Star Observers (AAVSO)
Fri, 10/04/2019 - 21:39
I have read that one can make a wavelength calibration source from a flourescent lamp starter, but I don't know how to do it. I tried connecting one directly to 120V AC house current--it glowed momentarily and then popped (burned out). Does anyone have plans for building such a thing?
You need to include a series resistor to limit the current. It was the Swiss amateur Richard Walker (The author of the "Spectral Atlas for Amateur Astronomers" ) who discovered some of these starters could be used as calibration lamps. He has a writeup on it here.
https://www.ursusmajor.ch/downloads/sques-relco-sc480-calibration-lines-5.0.pdf
(Note different starters have different gasses. The ones used in Shelyak's instruments are RELCO 480. which contain mainly Ne and Ar. They use a special constant current power supply derived from 12v which prolongs the life compared with a simple mains connection.
Cheers
Robin
The product does not seem available anymore.
I am looking for a calibration lamp that is larger than neon alone.
Best regards,
They are still avaialble here in europe eg
https://www.eibmarkt.com/gb/products/Relco-Starter-for-fluorescent-lamp-4-80W-SC480.html
though US suppliers probably don't stock them as they are 240v rated. Not sure if there are any 120v equivalents. You can also buy them as spares for their spectrographs from Shelyak instruments
https://www.shelyak.com/produit/se0148-argon-neon-spare-bulbs/?lang=en
Cheers
Robin
Hi Nathan,
I am part of a group that has been 3D printiong a spectrograph and have had some luck with DIY cal lamps. If you would contact me privately I will send along what we have found.
Jerry
You need a line-rich spectra for calibration. There are 2 inexpensive options:
I use a germicidal lamp (low pressure Hg) which has great lines from 250 - 1013nm. (see UVTools 4W M12 version or alternate sources for $20-30, and you can remove the cover and get the full coverage of lines.It is made for fluorescence and the cover over the bulb eliminates the visible light) Unit is self contained, uses 4 AA batteries and just turn on and use.
Neon Glow Lamps are rich between 500 - 800 and then a great line at 1176nm. It can be bought off of Amazon (CEC Industries C2A Neon Indicator Bulbs, 105 to 125 V, 0.25 W, Wire Terminal Base, T-2 shape (Box of 10)) for $6 for 10. All you need is a 40-50kohm resistor in line and connect to 110V (double resistor for 220V). Produces a bright light with great lines. So very simple solder one wire of 110V wire to a 50Kohm resistor, solder resistor wire to lamp, solder other lead of lamp to 110V wire.
110V--- 50Kohm -- Ne bulb -- other 110V lead
CAUTION/DANGER -- BE CAREFUL OF EXPOSED 110V WIRES! DEADLY!!! (Just need to say this!!!)
Combined, you get lots of lines. I usually use about 13 lines that are greatly resolved from 250 to 1176nm.
Hope this helps
If working at low resolution even the Balmer lines in a hot star can be an affective means of calibrating spectra but beyond that the Ne/Ar Relco starters are probably the most common solution and have the advantage of compactness so they can be built in. They are used in commerical instruments such as Shelyak LISA,ALPY and LHIRES and Starlight Xpress for example. I have even run them off something as simple as the battery powered flash circuit from a disposable camera but for long term reliability and safety you really need to run them off a high voltage constant current controlled supply though .
Many neon lamps also have some traces of Argon though and if you expose long enough you can see these and weak Ne lines too which give coverage in regions where strong Neon lines are lacking. There are some examples of other lines identified from a Neon lamp (as orginally fitted to my LHIRES, though that now has a Relco Ne Ar lamp) here on my website
http://www.threehillsobservatory.co.uk/astro/spectroscopy_12.htm
Cheers
Robin
Telescopes.net has them in stock. I just ordered 3 yesterday (17 Nov) and the lamps were shipped within a couple hours. Cost + shipping was $53.
I had purchased a set of 3 earlier from Shelyak. The wires on the lamps break easily which is why I was looking for more. If you're going to attach a lamp inside a sealed module that's one thing. However, if you plan to hang it in front of your scope or, in my case, place a couple along a bar attached to my flat panel, I suggest the following: 1) put heat shrink wrap along a wire that you'll connect to the lamp; 2) use a crimp connector to join the lamp wire to the power wire; 3) slide the shrink wrap all the up to the base of the lamp, then heat. This should take some stress of the lamp wires.
You'll need 25k ohms of resistance in series with the lamp which can be achieved with two 47k ohm resistors in parallel. The first time I did this I used 1/2 watt resistors and they ran hot. One watt resistors are better.
Finally you'll need something that converts 120v to 240v which you can find on Amazon for about $45.
You can get one of several noble gas samples on Ebay and power it with a kids Tesla Coil kit. About $10 for the tube and another $10 USD for the kids Tesla Coil, which you have to solder together. By bringing the tube proximal to the coil, it will light up and glow it's characteristic color. I actually put the pointy end of the tube inside the Tesla's coil tube. It seats in about 1/4 inch. I intend to use a diffuser with it. I'd post a photo, if I knew how.
I intend to make a holder that adjusts the distance of the tube to the coil in order to control intensity as adjusting the power of a very voltage circuit can be a little tricky to avoid arching etc. When the tube is fully outside of the coil tub by about half an inch, it is extinguished. Of course one should power it off to turn it off. These coils create a lot of EM noise so do keep them away from any digital circuitry or motors by a meter minimum or you may find your apparatus doing really strange stuff.
Creating a home-made calibration lamp can be a cost-effective solution for enthusiasts or small-scale labs. By utilizing readily available materials and following precise instructions, it's possible to achieve accurate results without breaking the bank. However, ensure proper safety measures are in place, and consider consulting experts for guidance on design and calibration procedures.
Is this comment AI generated? It reads like the sort of uninformative nonsense that it might produce. Having said that there are certainly some pretty dodgy suggestions in terms of safety in a typical outdoor environment in this thread.
A Neon or RELCO starter can even be run off the flash circuit out of a disposable camera, which might give you a jolt but shouldn't kill you
As well as the RELCO starters, some conventional neon indicator lamps also have a useful amount of Ar in them as well to better cover the blue end of the spectrum eg see Appendix 3 of Christian Buil's SpecInti manual
http://www.astrosurf.com/solex/specinti_annexe3_en.html
I use Sylvania FS-14 fluoro starters. They have the same lines as the Relco in Walker's spectral atlas, although the strengths are different. So, Argon and Hydrogen. It's nice to have a calibration line exactly on H alpha and H beta.
For power supply, I highly recommend the little inverters designed for electroluminescent decorative wire, which requires relatively high voltage limited current to illuminate so these supplies are perfect to drive the discharge tubes we use for calibration lamps. They are available either as battery powered (from Adafruit, or aliexpress), or 5v or 12v, just a couple of dollars, no need to hunt for or bodge around with an old disposible camera, if you can find one.
https://www.aliexpress.com/item/4000117490748.html?spm=a2g0o.order_list.order_list_main.16.6f5d18029TfHm9
I use a 12v one on my spectro rig. I previously had 240v and series resistors but really got tired of worrying whether a wet dewy night was going to make for a lethal short circuit. Using the 12v on my system, via a relay driven by an arduino, means the telescope has no 240V systems on board any more and is perfectly safe.
Hi,
I'm interested in trying your setup. Some questions:
1. I'm assuming there is someway to access the bulb inside the starter. Can you buy the bulb separately or do you have to take the starter apart.
2. The inverters in the AliExpress page all seem to output 80-130v, so it does seem that you still have some "high" voltage on your scope, or am I missing something.
I've tried using the RELCO starter lamps and have been disappointed. They are simply not that bright. Cheap Ne bulbs work great but, of course, their blue-end coverage is lacking.
Thanks,
Bob
yes, you always have to take the starter apart. the casing is opaque.
yes, the EL inverter voltage is circa 100V but it is much safer than using mains power. When using mains power, the live wire is 240v (or 220v or 110v, depending on your local mains power type) AC, referenced to ground. that is, the voltage on the live wire goes from zero to 240v and back to zero, every cycle (50Hz or 60Hz). if you are grounded, and you touch or are shorted to the live wire, you get the 240v shock, which is enough to make the 20-100mA current which can lead to fibrillation of the heart. With the little EL inverters, the voltage is only between the output terminals, and the maximum current output is only a few milliamps. also I read (but should get my oscilliscope and check) that they operate between 400 and 2000Hz. the voltages are reference to the output wires, not to ground, so touching one wire will not make a circuit between the voltage and ground through you.
What i was worried about was that I had previously the potential for 240V going to the thin little, easily broken wires on the bulb, which could get broken and end up touching the metal of the spectrograph -> telescope and potentially going to ground through me when I touch it.
yes the bulbs are faint. the higher frequency of the EL inverters does seem to improve the brightness a bit, and even without a resistor it doesn't cause the internal bimetallic strip to activate (this is why a series resistor is needed when operating at 240v, as the way these starters work is to provide a time-delayed switch, allowing current to flow through the cathode heaters of the fluorescent tube for a few seconds until they heat up.
to try to increase the amount of light going to where I want, i fixed aluminium tape to the bulb (keeping clear of the terminals on most of it, leaving a slit on the side which faces the input hole of my JTW L200 spectrograph (which originally had a neon bulb). the input hole is about 3mm diameter, facing a little flip mirror which swings in front of the reflective slit plate. I have installed a servo to control the flip mirror. the servo is also controlled by the same arduino, which is very easy to drive using the induino library of kstars/ikos, just requires editing an example file to specify the output IO pins and whether they are digital on/off or analogue (for servo control).
Even with aluminium tape, these bulbs are quite faint. even to get a decent exposure requires about 10-30seconds in my equipment depending on binning settings. For a faster spectrograph such as an alpy, this might be less. Apparently there used to be some decorative large bulbs with argon/neon mixture. I believe the marketing name was "Fily" or something like that. They had decorative shaped cathodes and glowed various purple or red colours. I think there was a write up about them on Christian Buil's website. I don't know why they are no longer on the market. Most likely just too much of a niche, but could be other restrictions (maybe they had a beta-emitter to improve arc strike? maybe energy efficiency.