A friend on one of the astronomy forums asked me if these would be any good for taking flats:

Any good?  They are utterly superb!!!!!!!!!!!!  AND they are cheap!!!!!!!!!!!!!!!!!!  AND you can get an A3 or even an A2 panel (also CHEAP) if you have a large aperture scope.

I think these guys may find they have an unknown market out there for their drawing light boxes :)

 

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13 Responses to “Amazing light panel for flats”
  1. Jim Matzger says:

    What size panel would work for a c11. Do you lay the panel on the end of the telescope with the telescope pointing up or do you take a photo from a distance?

  2. Greg Parker says:

    You will have to have a quick check of the panels available (the dimensions of the light emitting regions are given) compared to the aperture of your scope. I am using the smallest A4 panel for my Sky 90s, TS80s and 200mm Canon lens. So long as the panel more than fills the FOV of your scope you can put it where you like. I have had the scopes pointing straight downwards and straight upwards – makes no difference.

  3. Jim Matzger says:

    OK, I got one of those. It seems like the light is a little uneven in the middle. It is a little brighter on the upper and lower half with a channel in the middle that seem less bright. I would imagine that you could take a number of flats with the panel in different orientations and them average them. I was reviewing the material on flats and the advice was to use natural or incandescent light as opposed to fluorescent or led light. I don’t know if that is a factor or not.

  4. Jim Matzger says:

    Oops, I took another look and the channel in the middle is a little brighter than the upper and lower halves.

  5. Greg Parker says:

    Mine is completely uniform – in all channels – I use a OSC CCD.

  6. Jim Matzger says:

    Another issue I notice is that you get an interference pattern when you place the panel right on the front objective of the C11. I guess two light sources must be in phase right at that point. I guess a light box will have to be built that will put to eliminate the fringe patterns.

  7. Jim Matzger says:

    I am using a QSI 583wsg and a luminosity filter with the C11.

  8. Jim Matzger says:

    I am also using an f7 reducer, I wonder if that is a factor.

  9. Greg Parker says:

    This is most unlikely to be an interference pattern as the light source is incoherent LEDs.
    You could be seeing Moire fringing which is something quite different.

  10. Greg Parker says:

    The reducer shouldn’t affect anything.

  11. Jim Matzger says:

    What do you do to eliminate moire fringing?

  12. Greg Parker says:

    First look up Moire fringing on Google to make sure that’s what it is. Then once you know what causes Moire fringing work your way through the optical train to see where it can possibly be generated and eliminate it.

  13. Jim Matzger says:

    Greg, thanks for your help. I tested the QSI camera face down on the panel with no telescope, there was no pattern issue. I have a Meade variable T adapter that I use to attach the camera to the telescope. It consists of the T adapter along with an extension. I removed the extension and no longer have a problem with the pattern. I will have to check at night to see if the camera still comes to focus without the extension. So that flat field pattern has been with me since I bought the QSI. Thanks for recommending the panel, it has already hopefully solved a major problem! :-)

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