Creating an Interstellar Dust Nebula Experiment: Tips and Tricks for Success

[angela6884]

TL;DR

I want to make an experiment on how the interstellar dust, that make up reflection nebulae, reflects the light of nearby stars.

My experiment would need different composition of grains which would be ice, iron filings, and silicate shavings to act as the interstellar dust. I would drop these small particles(hopefully they will fall slowly) in a box and shut the lid quickly. Inside the box there will be a lightbulb acting as the nearby star. I will use a spectrometer(there will be a small hole in the box for the device to see through) and measure the wavelengths. Other changes I will measure would be the color of the lightbulb and the grain size. Does this experiment seem like it will work? Any tips to improve it? Thank you.

 

[sophiecentaur]

Summary: I want to make an experiment on how the interstellar dust, that make up reflection nebulae, reflects the light of nearby stars.

I would drop these small particles(hopefully they will fall slowly) in a box and shut the lid quickly.

You could keep the particles aloft with a loudspeaker, playing a tone at high level or even a small fan. The box should be very black so that the only light you observe has come from the particles. A well directed source of light would avoid scatter from the side walls. Some attention to the optics could produce better results - for instance the beam from a projector (not Digital).
You could research Rayleigh and Mix scattering to give you a hint of what you are likely to find. I wonder if the numbers would suggest that a large box could be needed (or a high density of scattering points). Before any spectroscopic measurements, you could just look at the colour of the scattered light. Our eyes are quite sensitive to this (blue sky effect and the bluish light from milky water).

 

[Drakkith]

The box should be very black so that the only light you observe has come from the particles.

I recommend coating the inside of the box with black felt. That's the same stuff many people use to coat the inside of their telescopes to stop stray light from bouncing around inside the tube and mucking your view up.

A well directed source of light would avoid scatter from the side walls. Some attention to the optics could produce better results - for instance the beam from a projector (not Digital).

That or a simple lens to collimate the light source.

 

[sophiecentaur]

That or a simple lens to collimate the light source.

A 'simple' lens arrangement could be harder to the uninitiated than an old halogen projector from the back of a laboratory store. I would guess that the OP is working with very little practical help (that's what we usually tend to find) so as much 'turn key' as possible would be desirable.
The sort of things that you or I would 'just do' can appear arcane to a student.
Black felt is the way to go!

 

[Tom.G]

Black felt is the way to go

I tried black felt a few years ago to get a black target for setting the black level of a scanner, the type used to copy a page of text. I tried several Art and Fabric stores. They all had a selection of colors in paper, felt, and velvet called Black... of course none were identical. In conversation two sales people referred to them as "different Blacks." It turns out that most black material, paper and fabric, is dyed with a mix of Blue and Red dyes to approximate Black.

I have seen advertised, but never tried, the black flocking, the flat black paper and the paint that is sold specifically for lining telescopes. Perhaps @DennisN or @davenn here know of a source for the stuff.

@angela6884, Please keep us posted on your progress/results.

Cheers,
Tom

 

[DennisN]

I have seen advertised, but never tried, the black flocking, the flat black paper and the paint that is sold specifically for lining telescopes. Perhaps @DennisN or @davenn here know of a source for the stuff.

I am not nearly as experienced with telescopes (nor astrophotography) as @davenn, @Andy Resnick and others in this thread, but I have heard of lining telescopes with black felt/black material. Which I actually will personally do soon on my cheap telescope . And now that I think of it, I got a link from a friend some months ago about an extremely black material which may be very suitable for removing light reflections, I will look for it on the net and be back soon...

Edit:
I found it, the material is called Vantablack, and there are videos about it on youtube, here's one:
(Update: Vantablack is not available for private use)
I don't know about availability nor cost, though.

Edit 2: And now I watched the video, and he said Vantablack is a special material that can only be applied by specialists. So, it's not for us hobbyists, I guess . The guy in the video also mentioned there is some special very black paint, but that sounded out of reach for hobbyists too. But I let the video remain here, since it might be interesting to others.

 

[DennisN]

but I have heard of lining telescopes with black felt/black material

I did some internet searching on Vantablack and alternatives and I found an interesting alternative
(found via the page http://feenta.com/vantablack-guide-where-to-buy-alternatives-more/):

Lights. BLACK 2.0 reduces light reflection, so you can use it to block out parts of reflectors, light bulbs, or paint anything that you don’t want to reflect light.

BLACK 2.0 – The world’s mattest, flattest, black art material by Stuart Semple
http://stuartsemple.com/project/black-v1-0-beta-worlds-mattest-flattest-black-art-material/

£12 for 150 ml. That's pretty cheap. Interesting. Maybe worth a try, at least for me .

 

[DennisN]

I have seen advertised, but never tried, the black flocking, the flat black paper and the paint that is sold specifically for lining telescopes.

And here are also some links for black flocking (used in telescopes):

http://www.firstlightoptics.com/misc/black-velour-telescope-flocking-material.html
£7.50 for (45 cm x 1 meter).

And a guide for flocking a Newtonian Telescope.

 

[davenn]

And here are also some links for black flocking (used in telescopes):

well we learn something new every day !
Flocking a telescope tube is a term I had never heard before
Yes, I know about keeping the inside of the tube black ... just not flocking in this contextDave

 

[sophiecentaur]

I have seen advertised, but never tried, the black flocking, the flat black paper and the paint that is sold specifically for lining telescopes. Perhaps @DennisN or @davenn here know of a source for the stuff.

A very successful technique was used in Analogue TV studios to produce a good black level with which to set up all the (vacuum tube based) cameras in a brightly lit studio. They were all lined up and faced the line-up card from different directions in order to get identical pictures from every camera. In the centre of the card was a rectangular hole with a black felt-lined box behind it. The black was very good (good enough for fussy studio Engineers) and would be one way to avoid any back lighting of the beam of light that's being examined for scatter. Size of box and area of hole would depend on what was required and also the optics of the detector.
The detector would also need to have some 'astronomical telescope' treatment, in the form of a tube with black felt lining.
The success of this project will depend (as ever) on Signal to Noise ratio and it seems to be that the level of scattered light would be pretty low for air-borne scatterers. I mentioned water suspension earlier on in the thread and perhaps that could be a way to go.

 

[angela6884]

A 'simple' lens arrangement could be harder to the uninitiated than an old halogen projector from the back of a laboratory store. I would guess that the OP is working with very little practical help (that's what we usually tend to find) so as much 'turn key' as possible would be desirable.
The sort of things that you or I would 'just do' can appear arcane to a student.
Black felt is the way to go!

I went with the black felt and now I am wondering whether LED lights are coherent sources of light? I can't seem to find a cheap projector that produces three separate lights. Have any in mind? If not it's fine. I have a $20 amazon card so I might buy this.

I tried black felt a few years ago to get a black target for setting the black level of a scanner, the type used to copy a page of text. I tried several Art and Fabric stores. They all had a selection of colors in paper, felt, and velvet called Black... of course none were identical. In conversation two sales people referred to them as "different Blacks." It turns out that most black material, paper and fabric, is dyed with a mix of Blue and Red dyes to approximate Black.

I have seen advertised, but never tried, the black flocking, the flat black paper and the paint that is sold specifically for lining telescopes. Perhaps @DennisN or @davenn here know of a source for the stuff.

@angela6884, Please keep us posted on your progress/results.

Cheers,
Tom

Alright I went with the black felt. Hopefully it was close to the ventablack material! Thanks for the noting a limitation for this experiment. :D

You could keep the particles aloft with a loudspeaker, playing a tone at high level or even a small fan. The box should be very black so that the only light you observe has come from the particles. A well directed source of light would avoid scatter from the side walls. Some attention to the optics could produce better results - for instance the beam from a projector (not Digital).
You could research Rayleigh and Mix scattering to give you a hint of what you are likely to find. I wonder if the numbers would suggest that a large box could be needed (or a high density of scattering points). Before any spectroscopic measurements, you could just look at the colour of the scattered light. Our eyes are quite sensitive to this (blue sky effect and the bluish light from milky water).

I went with black felt and I made a huge box for it. Once I start the experiment, I'll check what type of light is scattered. Thanks for the help!

 

[angela6884]

I recommend coating the inside of the box with black felt. That's the same stuff many people use to coat the inside of their telescopes to stop stray light from bouncing around inside the tube and mucking your view up.
That or a simple lens to collimate the light source.

I don't know anything about collimation unfortunately. But I'll use the black felt! Thanks!

 

[davenn]

and now I am wondering whether LED lights are coherent sources of light?

No they are not unless they are laser diodes

 

[sophiecentaur]

Look up collimation.

I am wondering whether LED lights are coherent sources of light? I can't seem to find a cheap projector that produces three separate lights. Have any in mind? If not it's fine. I have a $20 amazon card

Not coherent - just fairly near monochromatic.
The 'junk market' can be a great source of useful high tech toys - that Amazon toy looks like it could do your job and you wouldn't need a spectrometer - looking up the wavelengths of typical coloured Leds would give accurate enough information and you could use a digital camera to assess the different amounts of scattering by comparing the ratios of RGB values for light reflected by a good white target and the RGB values in the scattered light. (or just use a 'white LED source)