Stopping stray light from my EL Panel

[cjdawson]

Hey all.  I recently built an EL Panel from an A3 picture frame, some tracing paper and an EL sheet.  It works great.

However, as the thing is A3 sized, there's quite alot of light spent from the remainder of the panel when I have it attached to my 8" SCT.

So, I'm wondering about ideas on a way to cut out the stray light from the panel, when I'm trying to take flat frames.

Any Ideas?

[Lonestar70]

How about using a sheet of black art card available from most good craft shops in various thicknesses... cut an 8" hole in the right place and you could also add a ring, made from a strip or 2 of the same material about 1" wide, to slip over the OTA... easy to do, not overly expensive and simple to work with... also totally light proof.

Would fit directly into your frame if you use A3 size card.

A couple of coats of clear matt varnish or laquer on the outside will give protection from atmospheric pollution and damp.

Good luck and clear skies.

Sandy.

[cjdawson]

I like that idea, nice an simple.

There is a clear plastic front to my frame, which I've already epoxied a piece of wood too.  This let's me hang the panel on over the front of the scope. So, the card would have to go behind the clear plastic.  There there will be a small gap, some like would still leak out.   I'm only talking about a very small amount of light.  Also, I'd need to add a couple more supports to ensure that I line the scope up with the lit portion of the screen.  That's do able.  nice and cheap.

I've also had a thought about making a bag from some black fabric.  As long as the fabric doesn't let the light escape, that might work too.  Bascially it would be a tube of material, with an elasticated hole at the front, this slips over the dew shield to stop light escaping.  Not sure what fabric would be good to use for that.  It's a second idea.

wonder if there are any more ideas?

[NigeB]

Hi...

Well, the EL panel material I've used in the past can be cut (so long as you don't cut off the electrical connector of course  ) so assuming yours is of the same kind, you could trim it down - depending on where the connector is you might have a tab of luminescent material outside of the desired active footprint which you'd need to shield with black paint, foil, card etc. 

Personally however, I don't like cutting the stuff, so I'd go for something along the lines described by Sandy. 

Nigel

[cjdawson]

I've already decided not to attempt to cut it down.  Whilst the retailer said that it wouldn't be a problem to cut it, there's always the rick of slipping as I'm cutting making for a £60 mistake (8" scope, so used an A3 panel).

Sandy's solution is looking good, but I'm also sure that there will be a little bit of light leak.   I also just looked as I was demoing the flat panel to someone, and found that the panel isn't sitting flush against my ota anyway, so there will be a bit of light leak there too.

So in the end, I'm probably going to end up going for a solution where I get a big bag to put over the panel, like how photographers used to do when taking photos 150 years ago.

[Epicyclus Dave]

Hello

When I built my flats panel for my SW ED80 refractor, I used a 200mm x 300 piece of  50mm thick closed cell foam sheet (it is very stiff and almost no debris when drilling) , I then used a hole saw drilling in reverse to stop cutter jump & mangled circular hole effect & sliced the final size with a long craft blade, the el panel was fixed to the back of the foam with the light side peering through the hole in the foam and the back side of the EL panel was capped with a bit of 6mm ply wood , when I do my flats I push the foam square onto the dew shield and it holds the panel flat against the rim of the shield and stays put  allowing coffee to be enjoyed / histogram monitoring/ flat frame taking  .

On the back pic you can see the 12V to high voltage step up power pack that runs the EL panel.

Dave

[cjdawson]

That's perfect!  And a very elegant solution too.  Now, if I can get hold of another picture frame (for the plastic front as I've epoxied a piece of wood to mine) and some foam sheets,  wonder where I can get those from?

google is my friend...

https://www.efoam.co.uk/closed-cell-polyethylene-foam.php?gclid=Cj0KEQjwtaexBRCohZOAoOPL88oBEiQAr96eSODlzeblBO-Hxd4hYBxZ7kzpMecmOSwEmG6hCrLgsEEaAu9W8P8HAQ

so, whilst I'm at it, I'll get the measurements of a JCB toolox.  I'll be able to use that to make a new eyepiece box that will be the same style as the rest of my astronomy gear.