Light Panel

3 years 10 months ago #104847 by Bruno
Light Panel was created by Bruno
www.amazon.co.uk/gp/product/B00J3NRAV2/r..._81692021_em_1p_0_ti

This would be useful for anyone needing a light panel for making good FLATS.
It comes in A4 and A3 formats.

John

John
IAS

We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills
The following user(s) said Thank You: michael_murphy, KevinSmith

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3 years 10 months ago #104848 by albertw
Replied by albertw on topic Light Panel
I see that LED lighting panels are becoming more popular now. Has anyone got a good look at one up close to see how evenly illuminated they are?

Albert White MSc FRAS
Chairperson, International Dark Sky Association - Irish Section
www.darksky.ie/

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3 years 10 months ago #104853 by Bruno
Replied by Bruno on topic Light Panel
Hi Albert,
Here is the "proper" panel and you can get all the technical info on this page. But they are a lot more expensive.

www.gerdneumann.net/english/astrofotogra...panels-overview.html

John

John
IAS

We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills

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3 years 9 months ago #104856 by Skygazer2013
Replied by Skygazer2013 on topic Light Panel
Hey Folks,

I tried making a home made flat light box instead of buying the Gerd Neuman panel. I figured I could save a heap of money. However, I wound up spending a considerable sum before giving up. The light was just not uniform enough, too many photo sessions were ruined by the bad flats. I even experimented with a white screen on a laptop, but this was not ideal either.

This was frustrating after spending the money on an observatory, It's so rare to get good imaging opportunities that i just decided I couldn't afford NOT to have the right tools. Anyway, I bought Gerd Neuman panel and have never regretted it since. It was cheap in comparison to the investment in equipment and time i have made over the last 3 years. I wish I had known about the item on amazon though...it's cheap enough to be worth a shot.



Clear skies...Dave

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3 years 9 months ago - 3 years 9 months ago #104858 by CarlightExpress
Replied by CarlightExpress on topic Light Panel
I also have a Gerd Neumann panel, works a charm, Uniform light etc, I can't beleive I used to use a well lit wall :D

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3 years 9 months ago #104860 by JohnONeill
Replied by JohnONeill on topic Light Panel
Hi,

If you are interested in scientific work with CCD Photometry, you need to be sure the Panel emits uniformly (across the filter passband), let alone missing the filter passband (such as the near infra-red Ic in some cases) completely.

John

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3 years 9 months ago #104869 by albertw
Replied by albertw on topic Light Panel

Skygazer2013 wrote: I wish I had known about the item on amazon though...it's cheap enough to be worth a shot.


I wonder how uniform it is though. I can detect bright and dark spots on most computer screens.

It's probably good enough for most purposes, but as John points out when you start doing more sensitive work, then 'good enough' often isn't! I'd a flat field box with some LED's down one end and diffusers along the path. It was fine for astrometry and even taking pretty pictures (yay for photoshop!), but when I started to actually measure the flats I was getting differences with only slightly different positions of the box, so it's probably won't cut it for accurate CCD Photometry. Damn CCD Photometry is turning into an expensive experiment!

Albert White MSc FRAS
Chairperson, International Dark Sky Association - Irish Section
www.darksky.ie/

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3 years 9 months ago #104885 by eansbro
Replied by eansbro on topic Light Panel
I built a light box about 10 years ago and it worked well. I did write up a description report at the time.(see below) This was used on a large telescope. This description may provide some insight into using the right LEDs to correlate with the right wavelengths.

The light box needs to be light in weight and ease of use, uniformity of illumination and ultimately acceptable flat field correction.

The light box is constructed of 1/4" foam core. Each sidepiece is exactly 41.25” x 41.25" (4 pieces). The top is 40.75" x 40.75". The assembly is held together by a combination of glue and thin aluminium. The completed box is attached to the white plastic plate by glue. There are two diffusers each square is 40.00” x 40.00” positioned 2” apart within the square box. Each diffuser is bonded to a circular opening 38.5” each with the separation of 2”. The whole structure is tenaciously bonded with glue. All the edges are sealed with thin aluminium.
The whole structure is solid and incredibly light for man handling.
The illumination source and box proportions are key to a successful design with uniform illumination.

The ideal geometrical arrangement is when the most uniform illumination occurs when the distance from the inside top of the box to the LED's is equal to the separation of the LED's. The concept is that the top of the box acts as a first diffuser and by locating the illumination sources near the corners of the box, the resultant light combines to a uniform level at the plastic diffuser. The diffused light from the first diffuser projects to the next diffuser. The next diffuser smoothes out any remaining gradients. Flat field should be better than 0.5% with this design.
The design uses 8 LEDs. They are ultrabright white LED 5mm, 11000mcd. Nichia in Japan manufactures the bright white LEDs. They combine a high quality phosphor with their recently commercialized indium-gallium-nitride (InGaN) blue LED. They found that when blue light from the InGaN die passes through a thin phosphor coating, a portion of the blue light is down-converted to yellow light. This yellow light mixes with the remaining blue light to create a bright white light.
The emission spectrum of this bright white LED shows the blue emission from the InGaN die at ~460nm and the yellow (shifted light from the phosphor) peaking near 560nm. There is little blue intensity below 450nm, where as astronomical blue filters on CCD cameras extend down to about 370nm. The yellow shifted light extends to about 750nm, which covers most red astronomical filters.
Eight micro drives modules were built to power the Nichia LEDs. The driver was designed to provide maximum illumination to the LED while mimicking the light drop off of an incandescent bulb, which dims as the batteries are used up. Unlike an incandescent bulb, the driver’s current consumption drops at very low voltages, allowing usable light to be produced much longer. The optional universal power supply 3-12 Volt/800mA provides better sustainability.

A second key item were the LED holders. These holders support the LED and act as a baffle to prevent the light from directly illuminating the diffuser.
The LED's and holders are mounted near the centre of a 1" x 1" square of foam core, glued to the inside corners of the box with adhesive and located approximately above the plastic diffuser. They are located around 10.00” above the plastic. Spacing is not critical except to maintain the dimensional ratio mentioned above. Leads are through the side of the foam core and the wiring is outside of the box.

Eamonn

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