This one is literally a light box. I sat down to make a box today, and then thought of all the cardboard boxes I have stored away..... so one of the observatory building purchases finds a new use....
I went looking for LED's and resistors etc to make a white LED array - but found these LED modules at Jaycar - $19.95 for 10x3 LED's, prewired ready for 12V DC - draws about 150mA. (Jaycar cat no ZD0492)
These are double-sided-taped to a white board in the bottom of the box, and the top of the box is cut out for a piece of 3mm opal acrylic. Produces a very nice even light, and very light on the arms to hold up to the objective too. I wired an RCA plug to match my DIY dew heater arrangement.
This was made as a prototype, but I may just cover it in contact to fight dew and see how long it lasts!
how does this one work Lee? is it like a rear projection screen - onto an opal surface?
Exactly - there are 30 LEDs at the bottom, their light is diffuse by the time their beams get to the opal, which diffuses it more. Just hold in front of the objective....
Quote:
Originally Posted by Terry B
Not trying to be critical but I thought you would get a more even light if the inside of the box was white. This would reflect things around more.
I thought of lining the insides with the same white card from the bottom, but since I was prototyping thought I'd see how it went without - seems fine.
Nice job with the light box, the results look very promising – well done! I used single high intensity LED’s (x6) and mounted the LEDs in the “mouth” of my light box so they reflected back down the bucket I used, to then reflect back towards the OTA aperture where they were further diffused by a sheet of opaque Perspex.
I usually plan to shoot 10 Flats and then do a Median Combine and it makes a significant difference to the appearance of the combined Flat. The graininess almost disappears and the final median Flat looks so much smoother. I think the recommended exposure is that required to fill the well depth of the sensor to around 30%?
What appears promising with Lee’s design is that it is simple and appears quite effective from the results posted so far. I don’t have the smarts to perform any mathematical modelling or light ray tracing, so I just followed the advice on several websites which had the light bouncing off the inner walls and the bottom of the bucket to “flatten” it, before finally striking the main diffuser.
Lee’s design seems to achieve this via direct illumination of the diffuser by a bank of LED’s, which certainly simplifies the design and build process in my book.
will that bucket fit on my head? i have the urge to wear a lit bucket...
Quote:
Originally Posted by Dennis
Hi Lee
Nice job with the light box, the results look very promising – well done! I used single high intensity LED’s (x6) and mounted the LEDs in the “mouth” of my light box so they reflected back down the bucket I used, to then reflect back towards the OTA aperture where they were further diffused by a sheet of opaque Perspex.
I usually plan to shoot 10 Flats and then do a Median Combine and it makes a significant difference to the appearance of the combined Flat. The graininess almost disappears and the final median Flat looks so much smoother. I think the recommended exposure is that required to fill the well depth of the sensor to around 30%?
Now we are talking, see what you started Huff. That ugly duckling of yours has spawned all this DIY, well done.
I too have one, and will shoot a picture of it. Unfortunately it is redundant, as the scope I built it specifically for (TSA102) is no longer with me, and the replacement is an 8" newt, so it don't fit.
The light bucket is where I am headed, good idea Dennis. I normally aim for an ADU of about 20,000, is this about right?
for the SBIG depending on what colour I want depends on how long I make the exposure. The colour doesn't seem to matter with the DSLR as it is converted to 16bit grey scale in IP for flat fielding anyway.
I measured the output across the face of the lightbox and there is less than 0.2 lux difference between the center and any other spot around the screen.
Hi Guys, well I'm probably going to ask the dumbest question of all time and should probably know the answer, but, do you use the light box in the day or at night, never used one, or seen one for that matter other than on IIS.
![[1ponders]'s Avatar](../vbiis/customavatars/avatar45_9.gif){kind=avatar}
