Home made diffraction grating
Lurking Luser
diffraction gratings with a home printer. But it has some limitations. First
the resolution is maxed at 720 dpi and second the pattern is round wasting a
large amount of the transparency.
I have access to a HP 2200 laser jet printer that has a dpi of 1200. I
assume that is horizontal and not necessarily vertical but that should not
matter since you can make lines up and down just as easily as back and
forth, or for that matter set the printer to landscape. The idea appeals to
me because it is cheap, 50 cents for an 8 by 10 inch sheet of grating, and I
don't have to wait or pay for shipping. (Kind of along the lines of the
person who posted about frugal astronomy.)
So I have several question for the group.
1. Is the idea feasible?
2. Is 1200 dpi achievable or even desirable?
3. Would I be better off use 600 etching per inch in both quality and
defraction of starlight?
4. Are you better of putting the grating at the eyepiece or the objective?
5. Is there a simple way or producing this pattern in PhotoShop?
Thanks in advance and clear skies,
James King
LarryG
wrote:
1. I've made transparency gratings in the past, with mixed results.
Using a parallel-linear pattern on a 300 DPI printer, the finest
resolution was 150 lines per inch.
When placed over the objective, this caused a small spectrum angle which
was just right for a low power telescope ( < 100x). The downside is that
the lines were very coarsely drawn, smearing out the spectra instead of
allowing a desirable resolution.
Two limiting physical constraints seem to be involved:
a. the ability of the Laser Printer to deliver smooth lines
(of whatever shape) at high resolutions.
b. the optical quality of the transparency film (also quite rough).
You might be able to do better if you use an optical cement to
glue the rough side of the transparency to some relatively
smooth plate glass. The cement should fill in the hollows
of the film, thus reducing the optical smearing introduced.
A very slightly curved set of lines may provide the widening
of the spectra to where you can make out emission and absorbtion
lines.
2. 1200 DPI is probably NOT desirable, unless you have a really
wide-field scope. Beside the finest grating you can print will be 1/2 of
the max resolution. You need gaps between every line pair to transmit
light!
3. Whatever resolution you use, the limiting factors will be your
telescopes magnification and how smooth the grating lines are.
4. I like the objective grating because you can then change eyepieces
to match the magnification and field size with the diffraction angle.
5. Instead of Photoshop, I used a CAD program. A more precise way might be
to send graphics commands to the printer, but that would
require a suitable knowledge of programming.
Cheers,
larry g.
--
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/
Matthew Ota
would be better for making a diffraction grating.
Vector-based graphics are much more scalable than raster graphics
Matthew Ota
Jon Isaacs
>IMHO, a vector-based program such as Adobe Illustrator or Corel Draw
>would be better for making a diffraction grating.
>Vector-based graphics are much more scalable than raster graphics
>
>Matthew Ota
I think a CAD program is probably best, they are designed to print exactly to
the page and setting the line spacing is super easy. If everything is set
correctly, aliasing should not be a problem.
But the limitations of the printer are significant, dots are not squares so the
lines may have quite rough edges. 1200 DPI does not necessarily set the dot
size at 1/1200th of an inch, especially with inkjet printers. It just means
that there are 1200 dots of some size, probably greater than 1/1200th....
jon
Matthew Ota
Jon Isaacs wrote:
>>IMHO, a vector-based program such as Adobe Illustrator or Corel Draw
>>would be better for making a diffraction grating.
>>Vector-based graphics are much more scalable than raster graphics
>>
>>Matthew Ota
>>
>
> I think a CAD program is probably best, they are designed to print exactly to
> the page and setting the line spacing is super easy. If everything is set
> correctly, aliasing should not be a problem.
Well, CAD programs are vector based....
>
> But the limitations of the printer are significant, dots are not squares so the
> lines may have quite rough edges. 1200 DPI does not necessarily set the dot
> size at 1/1200th of an inch, especially with inkjet printers. It just means
> that there are 1200 dots of some size, probably greater than 1/1200th....
Well, then you take it to Kinkos or another print shop that as the
technology.
Matthew Ota
>
> jon
>
Bob May
getting the printer to do equally sized lines and this is difficult to do
with a printer being driven by a windows type program. The only real way to
control this is to use the printer language directly to draw the lines.
Next is that the dots (sort of round but not entirely so) drawn by the
printer will not make a good line so you are reduced to drawing lines of
several dots wide in order to keep the percent error of width of the line to
a reasonable figure.
Much better if you plan on making accurate gratings is to make a grating
engine. This is basically a step and repeat machine that draws lines across
a material with a lot better accuracy. Drawing etched lines across a glass
plate and then filling the etched part with India ink will do a lot better
than any piece of acetate or mylar with dots of a printer on it will ever
do. You will also be able to do a lot of Ronchi gratings for your friends
and sell them to the community as well.
Another method is to make up a large image of the lines and photograph them
but that runs into problems with very large images as negatives get
relatively expensive as the size goes up although the printed circuit board
industry has some fairly low cost film available with the laser printers
that will allow for the smooth lines needed for the job.
--
Bob May
Losing weight is easy! If you ever want to lose weight, eat and drink less.
Works every time it is tried!
Jon Isaacs
>Well, CAD programs are vector based....
True but they are different in that they are designed to objects input as very
accurate dimensions. So one can easily draw 3000 lines across a page that are
1/600th of an inch wide and spaced at 300 lines per inch.
>Well, then you take it to Kinkos or another print shop that as the
>technology.
>
>Matthew Ota
Still using dots....
Jon
Alan French
"Lurking Luser" <lurkin...@teleport.com> wrote in message
news:2AbXc.559$W_5...@newsread1.news.pas.earthlink.net...
> Centro de Observação Astronómica no Algarve has a little program to make
> diffraction gratings with a home printer. But it has some limitations.
First
> the resolution is maxed at 720 dpi and second the pattern is round wasting
a
> large amount of the transparency.
James,
I believe that the Amateur Scientist column in Scientific American had at
least one article on actually ruling a diffraction grating. (Just in case
anyone is really ambitious.)
Clear skies, Alan
Geoff
If the purpose is to make a ronchi grating you could try the DYI nylon
monofilament version
James Horn
magazine's "Amateur Scientist" column gave the details of a homemade
diffraction ruling engine. A fascinating read...
Clear nights!
Jim
Howie Glatter
> I believe that the Amateur Scientist column in Scientific American had at
> least one article on actually ruling a diffraction grating. (Just in case
> anyone is really ambitious.)
I thought you were a nice guy, Alan, and here you are leading the
unsuspecting down a primrose pathway. Here's what Uncle Al Ingalls
said in the June 1952 Scientific American:
" . . The specifications are fantastic, but even more fantastic is the
ruling engine that has been contrived to do the job. This machine,
less complex in structure than a typewriter, is the most precise
mechanism ever made. It is so transcendently difficult to build and
operate that it has challenged man's mechanical genius and humbled his
pride for more than a century . . Why has this simple machine
frustrated so many able men? The dream of building a ruling engine has
haunted hundreds and ruined many. Recently a friend . . talked of long
deferred plans to quit his vocation and build an engine. "Over my dead
body!" exclaimed his wife, to whom he had once unwisely revealed that
a man might spend 10 nonproductive years curing a chronic case of
ruling engine fever the hard way . . When an Australian nurseryman
named H.J. Grayson
died after years of this acute malady . . his widow bitterly burned
all his ruling engine papers.
The central difficulty that has defeated so many efforts is the
inherent deformability of any material of which a machine may be built
. . On the scale of ultra-ultra precision with which we must deal in
a ruling engine we may regard the machine as being made of rubber. In
effect it has just about the same problem as an intoxicated man called
upon to pass a test of sobriety: it must place the tip of its finger
(the diamond) on the tip of its nose (the groove position) within a
millionth of an inch, and it must do this with a rubber arm and body!"
I'm going to have to speak to Susan about your postings. Maybe she
can influence you to desist from these subversive suggestions.
Your friend, Howie
Alan French
news:278e5035.04082...@posting.google.com...
Howie,
You mean you're not heading into your shop and starting work on a ruling
engine? <G> I am continually amazed at what some ambitious folks manage to
do, and the Amateur Scientist column certainly had some interesting
examples. I suspect, however, that more than a bit of insanity would be
required to try ruling your own diffraction grating. I think a seismograph
would be a more reasonable, and interesting project.
Clear skies, Alan
Hellas Ospidakos
dice it. Their very nature makes that self-evident and anyone attempting
one would find that out straightaway. That was what Ingalls was saying.
Scientific American had a kind of elitist attitude when it came to its monthly
projects, or nonprojects as the case sometimes was. Parts availability often
fell short of suggested reality, and of course everyone had a 12" lathe and
2 ton marble slab in their basements just wating to be used! There was often
something stoggy and Limbauesque about much of this, as if these projects
were being handed down by an Angel for mortals to wrestle with and be
brought into submission by. The next month would bring an even more impossible
puzzle. Thank God the text of the magazine did not follow a
similar line of thought ....... or lack of thought.
The thought of making one's own grating today really is a bit bizzare, or a
throwback idea, not to mention the inherent problematics. Buy the $3.00
gratings the guy suggests above and save your sanity... and your finger
nails.
And once you have built the ruling machine what in hell will you do with
it then? Peel mangos?
Paul.
Chris1011
would be a more reasonable, and interesting project.>>
Having worked at Bausch & Lomb in the early '60s, where they had many ruling
engines working 24/7, I can tell you that they were all pretty good
seismographs.
Roland Christen
Yuri
> diffraction gratings with a home printer. But it has some limitations. First
> the resolution is maxed at 720 dpi and second the pattern is round wasting a
> large amount of the transparency.
>
>
> 1. Is the idea feasible?
> 2. Is 1200 dpi achievable or even desirable?
> 3. Would I be better off use 600 etching per inch in both quality and
> defraction of starlight?
> 4. Are you better of putting the grating at the eyepiece or the objective?
> 5. Is there a simple way or producing this pattern in PhotoShop?
>
> Thanks in advance and clear skies,
> James King
A good diffraction grating could be done by using spider's web:
Here are a few tips:
1. find a good old spider who does not mind to share
2. do not use strands that made for catching flys, but that used by
spider for walking on
3. do not try to put the strands parallel - it is almost imposible by
counting the diamer of it ~2.5mk, but put one after other and remove
each second later!
Of coarse it is hell of work and if it is too difficult, the rest of
the web could be used for cross-hair for eyepiece.
(-:
Regards, Yuri
Steve Taylor
>
> Howie,
>
> You mean you're not heading into your shop and starting work on a ruling
> engine? <G> I am continually amazed at what some ambitious folks manage to
> do, and the Amateur Scientist column certainly had some interesting
> examples. I suspect, however, that more than a bit of insanity would be
> required to try ruling your own diffraction grating. I think a seismograph
> would be a more reasonable, and interesting project.
Brian Manning, the man who built the "DIY" ruling engine still
has a website where it is discussed.
http://www.britastro.org/iandi/manning2.htm
and as its says there :
This article was originally published in the 'Amateur Scientist' column
of Scientific American, 232(4), April 1975, and here appears in a
modified form. Brian was an engineering draughtsman when the basic work
was completed, and a laboratory technician with the Department of
Engineering, University of Birmingham (UK), when the article was
originally published. He had the distinction of being the first amateur
to make diffraction gratings of unsurpassed optical quality with an
instrument of ultimate mechanical precision - a ruling engine. This
project occupied him for two decades. He subsequently devised a
refinement to his ruling engine (see Addendum, above) by utilising the
piezoelectric effect on a crystal to minimise the 'rubbery' consistency
of metal at the molecular level that his ruling engine probed. After his
retirement he received an honorary PhD from his university and was
awarded the Horace Dall Medal of the British Astronomical Association.
Steve
Maurice Gavin
<st...@astronomycentre.org.uk> wrote:
>
>Brian Manning, the man who built the "DIY" ruling engine still
>has a website where it is discussed.
>
>http://www.britastro.org/iandi/manning2.htm
>
>Steve
Brian's a mate/buddy and I prepared including the text referred to, as
then BAA I&I webmaster, to resurrect the original SciAm article<g>.
BTW - think I read all the messages but nobody said what they would
[politely!] do with said [printed] grating! A practical and easier
intermediate route eg stellar spectrum via diffraction, simple devises
like a tennis/badminton racket or a fine kitchen sieve work at
http://www.astroman.fsnet.co.uk/begin.htm
Maurice Gavin @ Worcester Park Ob - UK
www.astroman.fsnet.co.uk = home of practical amateur spectroscopy
Alan French
news:20040828104747...@mb-m04.aol.com...
Roland,
I would think so. Did they make everyone where soft-soled shoes and tread
lightly in the halls and stairs?
Clear skies, Alan
Chris1011
lightly in the halls and stairs?>>
The ruling engines were 100 ft below street level down on bedrock.
Roland Christen