Right. So, this flat...

[BrendanC]

... is a master taken from 25 flats in DSS, for which I used this: https://www.amazon.co.uk/dp/B07N128B74/ref=pe_3187911_185740111_TE_item

Yep - cheap, probably not ideal, but I thought it was worth a go, just put it on the lowest setting, cover the scope, take the shots so the histogram is central (works out at around 1/80s on my DSLR).

Out of curiosity, I loaded it into StarTools and stretched it. I've attached the result.

If I zoom in, I can see lots of dots. Now, are those dots the individual LEDs from the panel, or the camera's matrix? Because if they're from the panel, I'm obviously going to have to think of a different approach, probably using paper or t-shirt to diffuse the light, or something completely different such as sky shots or laptop screen. If it's the camera's matrix then I guess that's ok. As is often the problem here, I'm doing this totally on my own with nothing to compare it with!

master flat.tif

[tooth_dr]

2 minutes ago, BrendanC said:

... is a master taken from 25 flats in DSS, for which I used this: https://www.amazon.co.uk/dp/B07N128B74/ref=pe_3187911_185740111_TE_item

Yep - cheap, probably not ideal, but I thought it was worth a go, just put it on the lowest setting, cover the scope, take the shots so the histogram is central (works out at around 1/80s on my DSLR).

Out of curiosity, I loaded it into StarTools and stretched it. I've attached the result.

If I zoom in, I can see lots of dots. Now, are those dots the individual LEDs from the panel, or the camera's matrix? Because if they're from the panel, I'm obviously going to have to think of a different approach, probably using paper or t-shirt to diffuse the light, or something completely different such as sky shots or laptop screen. If it's the camera's matrix then I guess that's ok. As is often the problem here, I'm doing this totally on my own with nothing to compare it with!

master flat.tif 58.16 MB · 0 downloads

I use the same cheap panel but put an A4 piece of opaque acrylic over it just to diffuse it slightly further.  You wouldnt pick up the dots like that especially as you would be really out of the focal place, so I'd say that it is ok.  You could rotate the panel between the first and second half of the set of flats if you so wished to eliminate any gradients.

[tooth_dr]

A3 but the same. 

[BrendanC]

Excellent. Thank you @tooth_dr, looks like you have a fairly serious setup too, so that gives me confidence. I need confidence.

[tooth_dr]

2 minutes ago, BrendanC said:

Excellent. Thank you @tooth_dr, looks like you have a fairly serious setup too, so that gives me confidence. I need confidence.

No problem, I bought my acrylic off here, it just finishes it off (if that makes sense) and means you dont necessarily have to use the lowest setting on the panel.

Opal Acrylic Plasticx Sheets (plasticsheets.com)

White Perspex Sheet | Colour Code 069 (plasticsheets.com)

 

[BrendanC]

Which one of those two sheets do you use? 

[BrendanC]

Hi, @tooth_dr, just bumping this one, hope you don't mind - you listed two links for the acrylic sheet. I'm really interested in getting one - but which one? Or do you use both, and if so, why?

[Dinglem]

@BrendanC I use a couple of sheets of white A4 paper between my cheap panel and the scope, I also turn it 90deg half way through taking the flats, it seems to work ok.

[BrendanC]

Thanks - I've tried that too, also used tracing paper, but I'm very interested in an acrylic sheet just because it might diffuse better and be a bit more durable!

[Dinglem]

I'd be interested in your results as I'm forever managing to crease my bits of paper, it doesn't go to waste though as I have 3 young granddaughters that like to paint 👍

[BrendanC]

Exactly! I've heard that apparently laminating them helps, but even that somehow seems a bit flimsy. I'm sure I could just get any old acrylic sheet, but as @tooth_dr seems to have a working solution I'd like to know which one! Also thickness, colour etc.

Edited November 24, 2020 by BrendanC

[tooth_dr]

22 minutes ago, BrendanC said:

Exactly! I've heard that apparently laminating them helps, but even that somehow seems a bit flimsy. I'm sure I could just get any old acrylic sheet, but as @tooth_dr seems to have a working solution I'd like to know which one!

Sorry, I don’t how I missed your reply last night. I use a white one and a grey one (!) together to get the right timing (>3.5s) on my camera and luminance filter. I can use just the white sheet ones own with my Ha filter. I would suggest the white 3mm sheet as the opaque one is quite see through and the white diffuses better. 

Edited November 24, 2020 by tooth_dr

[Nicola Hannah Butterfield]

@BrendanCI don't think colour would matter too much, though I would personally go white., what thickness though 3 or 5mm.

Edited November 24, 2020 by Nicola Hannah Butterfield

[BrendanC]

I'll probably go for the white 3mm sheet then! 

Thanks all.

[tooth_dr]

6 minutes ago, BrendanC said:

I'll probably go for the white 3mm sheet then! 

Thanks all.

Good idea. That’s what I’m using, 3mm. 

[wimvb]

23 hours ago, BrendanC said:

If I zoom in, I can see lots of dots.

What you're seeing is the Bayer or CFA pattern (RGGB). All is as it should be.