EL Panel light plate

[coldlegs (Stephen)]

Decided it was time to get serious about astrophotography and make a light box. Almost bought one of those for sale on this website but decided I liked playing with EL panels more more than woodwork and boxes. So bought an A3 sized El panel for $112 on ebay that should just fit across my 10”sct and went looking for some opal perspex to diffuse it. You really have to go looking for a sign writing business if you want to get some. Got some for $20 A3 size panel. Found an old long thick piece of plastic in the shed and with a lot of heat from a heat gun, got it to bend into the shape of the circumference of my scope. Attached it to the opal perspex with counter sunk screws and right angle PCB brackets then used silastic to stick the EL panel on. Stuck some foam that came with the panel on the back of the panel with silastic and mounted the power supply on as well. Tried it out last night and it seems to worked well but I need to check for potential gradients across it and I'm not sure I have any freeware that will measure the histogram of a complete image. My understanding is that you take a flat field image then rotate the camera 90 degrees and take a second image. The first image is calibrated against a master dark and the second image becomes the flat field so the resulting image should be uniform if there is no gradient.

One point to note. When buying a large EL panel watch out for ones made up from two separate internal El sheets as these have a line down the middle and it will screw up the uniformity of the light.

Cheers
Stephen

[bmitchell82 (Brendan)]

whats the camera you are using again stephen?

[coldlegs (Stephen)]

I hope to get serious in the new year with my QHY9 mono. Can't recall if the software that came with it can do the histogram thing I mentioned but I'll check it out shortly.
Cheers
Stephen

Originally Posted by bmitchell82

whats the camera you are using again stephen?

[bmitchell82 (Brendan)]

its just interesting because i know a few people who have tried to use the EL panels and they are too bright for the qhy9. you want to be aiming for a minimum of about 2-3 seconds to reach your 25-35k ADU it just makes for better flats. I guess 2 slices of Perspex would make that happen

[coldlegs (Stephen)]

I got an extra piece just in case. Let you know how it goes.
Cheers
Stephen

Originally Posted by bmitchell82

its just interesting because i know a few people who have tried to use the EL panels and they are too bright for the qhy9. you want to be aiming for a minimum of about 2-3 seconds to reach your 25-35k ADU it just makes for better flats. I guess 2 slices of Perspex would make that happen

[Marke (Mark)]

I remember reading you can run them at 9v and the brightness is closer to what you need . I have ordered one of these myself to try out and can always use more opaque perspex to to reduce the brightness.

Mark

[bmitchell82 (Brendan)]

you just have to be careful of running something outside its specified voltage, you run the risk of stuffing the electronics, and they are all different so just be warey ide rather buy a extra piece of perspex for a few bob than another 120 dollar EL panel

[John K]

Interesting concept.

Forgive my ignorance, so why would a simple dimmer switch not work in this set up to adjust the brightness up and down?

[coldlegs (Stephen)]

Originally Posted by John K

Interesting concept.

Forgive my ignorance, so why would a simple dimmer switch not work in this set up to adjust the brightness up and down?

John
Ended up making a 12V DC variable output regulator to control the panel switch-mode power supply as I wasn't sure about a switch-mode dimmer trying to control a switch-mode power supply. The DC regulator works very well.
Cheers
Stephen

[cfranks (Charles)]

Stephen,

When taking Flats, you don't rotate the camera wrt the optics. That defeats the purpose of Flats. I take > 50 Flats (per filter) and calibrate/stack them to get the Master Flat. I use a similar setup to yours over the end of my ~ 12" tube but I rotate the EL panel a couple of times during the series to reduce any unevenness in the light.

Charles

[coldlegs (Stephen)]

Originally Posted by cfranks

Stephen,

When taking Flats, you don't rotate the camera wrt the optics. That defeats the purpose of Flats. I take > 50 Flats (per filter) and calibrate/stack them to get the Master Flat. I use a similar setup to yours over the end of my ~ 12" tube but I rotate the EL panel a couple of times during the series to reduce any unevenness in the light.

Charles

Charles
You rotate the camera to test the evenness of the flat field itself not to take flats for correcting images.
Just out of curiosity what size EL panel are you using to cover a 12" scope?
Cheers
Stephen

[mswhin63 (Malcolm)]

Hi Steven, I have an EL panel flat frame light, but i am getting some interference bars. My set-up is currently down at the moment but wondering if you are getting these bars as well?

I am going to re-design the power supply to see if I can get rid of it.

[coldlegs (Stephen)]

Originally Posted by mswhin63

Hi Steven, I have an EL panel flat frame light, but i am getting some interference bars. My set-up is currently down at the moment but wondering if you are getting these bars as well?

I am going to re-design the power supply to see if I can get rid of it.

Hi Malcom
I'm not getting any bars. That sounds like some kind of download interference. the panel should be a flat white unless it's made of two pieces which will give you a line down the middle.
Cheers
Stephen

[cfranks (Charles)]

Hi Stephen,

I've had mine for a few years now so I can't remember where I bought it from. It was A3 in size and I just scissored off the bit I didn't need (to make a square). My scope is a 10" RC but the tube is nearly 12" dia. The power source has a built in control to dim the light for better exposure control. I do most imaging in Narrow Band and find the my EL panel is not too good at Ha and SII frequencies. H-alpha flats @ 1x1 were taking ~ 400 secs! I now use a translucent panel over the end of the scope and take flats in dull daylight.

Charles