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Method for taking Flats


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I have built one similar to the LED one shown in the link using Display Mount board I used laminating pouches as the diffuser instead of tracing paper..

This was fine for the 66 but seeing as I started using a range of scopes and camera lens I use an EL panel behind a couple of opalescent diffusers this can be hung from the obs roof and any of the scoeps or camera setups can take flats off it...

You dotn really need the diffuser but they protect the panel and dim it as well meanin longer expsoures for the flats which helps make sure you dont capture any banding from the EL Driver...

Peter...

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Twilight sky -- but we have a permanently mounted camera which means I can afford to wait for clear twilight sky.

I do have a flat field screen set up in the dome -- just a bit of white card I can illuminate from below and point the telescope at. It does in a push, but the large scale structure is noticeably worse than the twilight flats.

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I use my laptop for my falts. Open notebook on a full white empty page and hold it up to the scope. I have set the exposure in camera tp +2/3 and so far it seems to have worked really well. I don't know why I found them so scary initially!!

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I have an old 15 inch flat screen monitor in the obs that I put full screen notepad on. I place a sheet of A3 paper over it and a white cloth / teashit elastic banded to the scope.

I alter the brightness by moving the monitor closer to the scope.

The monitor sits on a chair by the scopes and has one of those flexy stands to allow you to raise, lower and tilt it to be inline with the scope.

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Sky flats for my Canon 1000D, White T shirt over scope and camera set to Av and never had a problem with these.

Atik mono CCD is another ball game, it need at least 4 secs exposure to eliminate the affects of the mechanical shutter, for this I use white Tshirt with a light shining on a white canvas some 2.5-3m away

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white card and lantern shining on it. ultra low tech and works so far for me. just have to make sure the card is larger than the scope (A4 no good.. A3 only just ok :))

Derek

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Apparently, the flatest part of the twilight sky is 85 degrees altitude and at the anti-sun azimuth (i.e. ~east at sun-set).

But yes, sky flats can be a problem for wide fields of view.

I think it is light leaks in my case. I use a manual FW, though from memory the closed electric was the same.

Also I want to process images the next day, not wait till twilight. I can't do them in advance because of focus and framing affecting the flat.

Olly

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I can never avoid gradients in sky flats (but I live in a place with intense sunlight.) I have made two lightboxes but the best and easiest are with an Aurora panel from Gerd Neumann. Foolproof and a reliable spectrum.

Olly

Seriously dark skies and too much sun ..... rub it in Olly :D

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I have used a laptop monitor before, but now I tend to use the TV when I bring the scope in. I open up a blank white image and point the scope at that, with mixed results... One problem here is that the mirrors can dew up; also I always wonder if the change in focus due to temperature has an effect.

My most successful flats have been using the twilight sky.

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I have used a laptop monitor before, but now I tend to use the TV when I bring the scope in. I open up a blank white image and point the scope at that, with mixed results... QUOTE]

I thought one golden rule with flats was not to move ANYTHING from when imaging.

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EL panel from Poster Power plus a couple of perspex sheets from EBay - black one on the back and a tinted one plus an opal one (to act as a diffuser) on the front.

Are these guys any good? Just pinged them an email.

Other companies never replied to my emails so I'm giving them a miss.

My lcd screen I was recently using smashed and I used the other half's lappy with note pad this morning with great effect. But I need to just get an el panel.

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I thought one golden rule with flats was not to move ANYTHING from when imaging.

So long as nothing moves in the imaging train it should be ok... In reality, I guess there is a chance of knocking things when bringing the scope inside; in fact I did just that on my last imaging session and so had to forego the flats :)

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Are these guys any good? Just pinged them an email.

Other companies never replied to my emails so I'm giving them a miss.

My lcd screen I was recently using smashed and I used the other half's lappy with note pad this morning with great effect. But I need to just get an el panel.

I bought a A5 EL panel from them and it arrived next day. Very good service.

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Ah, good to here.

Unfortunately they won't reply to my emails.

Did you buy the 12V adapter separately or was it an option/alternative? They mention it in one of the pages but I can't see it in the product list.

And how much was postage?

Sorry for the Qs :)

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Ah, good to here.

Unfortunately they won't reply to my emails.

Did you buy the 12V adapter separately or was it an option/alternative? They mention it in one of the pages but I can't see it in the product list.

And how much was postage?

Sorry for the Qs :D

Can't remember....I'm getting old:)

I'll dig the invoice out and come back to you asap.

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