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

Lurking Luser wrote:

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.

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