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Lightbox for flatfield frames


astrovirus
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Hi all,

Just finished my DIY flatfield lightbox and though of sharing it with the forum. It is constructed from isolation foamplates (styropor) with bright warm white LEDs for lighting. 12V DC power needs constructed with some standard resitors and a potentiometer to reduce brightness. Difusers made of drafting paper (first 2) and transparant flyer (not sure if this is correct English, i mean the type of paper to make kids kites?) paper (last one).

First pic shows the basic electronincs and the styropor components for the difusers and for the fit to the skywatcher black line 200P newton.

Second pic shows the nearly completed lightbox with a look down the barrel (taken with the compact cam in Av mode) and a look at the finished product in the dark.

3rd pic shows the final product.

Now it's time to give it a full test during the next few clear nights, which is looking good for the coming days and weekend. :D

Hope you like it,

Greets Tim

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Hi Tim , Looks great. :D

What glue/adhesive did you use on the Styropor? I think that stuff is expanded polystyrene so glue choice would be important . With some solvent based glues it will just dissolve away .

Looks like a strong PVA (such as 'No Nails' ) might fit the bill .

Thanks for posting,

Len E

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Hi Len,

It is indeed expanded polystyrene. I use the following kit (see picture) from Pattex to glue the part together. I had some arround from another project in the garden. I just happened to read on the side of the can that it could be used on polystyrene so I made a sample connection from some left over plates and it worked perfectly.

Unfortunately, it seems that it is not available in the UK as I can't find a Pattex website for the UK.

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Hope you get to try it soon. My DIY lightbox has made a significant improvement to my images. For something so simple and cheap to make it really does make a huge difference, I cannot recommend a flat producing device highly enough!

Getting rid of the gradient makes processing so much easier... Before I had mine I'd always get a big circular blob, for want of a better way to describe it, in the middle of the image with the corners remaining dark. That made it hard to pull out all the image detail without the gradient showing up horribly. That's not a problem any more! :D

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Thanks for sharing this! Looks like I need to build one of those too. I have these gradients on the first test pictures I've taken with my 1000D. Sounds like a fun project for those awful, warm and not very dark summer nights... :D

One question though. You say you need to wait for a clear night to try this out. Is this not something you can do during the day or a cloudy night? Do you need to take flats for each imaging session during the same night? It's beginning to sound like half of each imaging session will be taken up by taking darks, flats, bias, ... ;-)

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Is this not something you can do during the day or a cloudy night? Do you need to take flats for each imaging session during the same night? It's beginning to sound like half of each imaging session will be taken up by taking darks, flats, bias, ... ;-)

You could do this on any night, but to see the effect of the flatfields you need to have matching lightframes. In this way you can actually compare processing these with and without the flatfields. Furthermore, flatfields should be taken with the exact same imaging train (which includes focus and camera orientation) as the lightframes, and therefore is difficult to do in advance or afterwards for a previous imaging session.

And yes, in my opinion every imaging session should include taking darks, flats and bias. Although the latter 2 don't require that much of precious imaging time, the darks do :D. However, other people have great results using masterdark, masterflat and masterbias libraries.

Edited by astrovirus
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Thanks for that explanation. Yeah, I see how camera rotation could be an issue. So flats are short exposure then, similar to bias? That's a relief. I've read up on darks and bias (as that's easy to do) but haven't looked into flats so far.

I seem to remember reading somewhere that a TFT monitor background lighting would be ideal to take flats.... That would make the whole thing a bit smaller...

Ahhh, I see a new project coming up... There's hope yet for those boring summer days and nights .. ;-))

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I seem to remember reading somewhere that a TFT monitor background lighting would be ideal to take flats.... That would make the whole thing a bit smaller...

But also a lot more expensive. That's also my reason to opt for the LED version. Some guys in my local astronomy club do use Electro Luminescent panels and they produce excellent flats, however the panels alone cost around €80 euro or more and I estimate the total costs of my lightbox to be around €20.

Edited by astrovirus
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Hmmm, I happen to have an old 14" laptop panel lying around. It is 220mm high and should be big enough for my 8" scope. If I can remove the backlight "unit" and use it, then that's not going to cost anything. I might give that a go tonight and report back. It might just be possible to buy broken TFT monitors on ebay very cheap and use the backlight....

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I have taken apart the laptop display panel last night. It is indeed possible to separate the TFT part from the backlight part. I now have a display backlight panel and a transparent TFT panel. :D

Not sure what to do with the TFT panel but the backlight panel will be turned into a light box.

I better start my own thread though. I'm seriously off-topic in this thread now. Sorry! :D

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