Author Topic: Batch processing help DSLR  (Read 6090 times)

Offline pfile

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Re: Batch processing help DSLR
« Reply #15 on: 2013 July 25 08:06:33 »
the blues are still way overexposed in those new flats. you want those histograms all in the middle of the display.

Offline MikeOates

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Re: Batch processing help DSLR
« Reply #16 on: 2013 July 25 15:15:55 »
Rod,

Glad I could help. Yes that is the type I mean, the one I use is this http://www.earlsmann.co.uk/sections/product/id/10 They can be cut to size and with a bit of DIY I made this:

I used translucent plastic (2 sheets) to diffuse the light even more, the card cutouts are just to space the sheets, this fits on the end of the scope and I don't need to move the scope to take the flats. Works fine with the Astronomik CLS-CCD filter and Astrodon 5nm Ha, not tested with other filters yet. At f5 I give 0.3s exposure ISO100 with the CLS and 5 seconds ISO200 for the Ha.

Here are screenshots of the histograms for each filter (using lightroom), the top being the Ha. I am having good results from these flats. But regarding the Ha, this needs special processing, which I will reveal when I get the time to write it up on this thread: http://pixinsight.com/forum/index.php?topic=5748.0

Mike

PS: The blue you see in the photo is a peel off cover, the plastic is white underneath.

astropixel

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Re: Batch processing help DSLR
« Reply #17 on: 2013 July 25 16:01:05 »
Rod. I have used flats from various screens. More recently a Samsung Galaxy - with no deleterious effect.

The streaks in your image are most likely  produced by images too closely aligned during acquisition. The effect is pronounced with a small amount of drift between images. Irrespective of mismatched calibration frames, the effect can be eliminated by dithering all your images during acquisition by 10 - 15 pixels.

Dithering will resolve a large proportion of your current difficulties. But dithering must be agressive with DSLRs.

Flats - about 70 - 75% on your camera preview histogram is about right for starters.

There is a tendency to get bogged down in the detail. Unless you dither your shots you will spend all your time post processing artifacts out, which can be minimized by basic acquisition techniques.


Offline Rod771

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Re: Batch processing help DSLR
« Reply #18 on: 2013 July 25 17:44:03 »
the blues are still way overexposed in those new flats. you want those histograms all in the middle of the display.

Cheers Rob,

 I'm finding the blue channel hard to control (possibly due to the F2 ratio??). The pink screen definitely helps the red channel as you've proved but the blue is still very strong. I've experimented with the screen colour by lowering the blue values thus creating a mustard/orange colour. It did bring the blue back in line with red and green but am i getting way off track? I've haven't heard or read of anyone using mustard colour light sources for flats.  ???

Offline Rod771

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Re: Batch processing help DSLR
« Reply #19 on: 2013 July 25 17:48:21 »
Rod,

Glad I could help. Yes that is the type I mean, the one I use is this http://www.earlsmann.co.uk/sections/product/id/10 They can be cut to size and with a bit of DIY I made this:

I used translucent plastic (2 sheets) to diffuse the light even more, the card cutouts are just to space the sheets, this fits on the end of the scope and I don't need to move the scope to take the flats. Works fine with the Astronomik CLS-CCD filter and Astrodon 5nm Ha, not tested with other filters yet. At f5 I give 0.3s exposure ISO100 with the CLS and 5 seconds ISO200 for the Ha.

Great work Mike, I will look into that, thanks

I had read your HA thread and will keep an eye on it  :)

Offline Rod771

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Re: Batch processing help DSLR
« Reply #20 on: 2013 July 25 18:06:03 »
Rod. I have used flats from various screens. More recently a Samsung Galaxy - with no deleterious effect.

The streaks in your image are most likely  produced by images too closely aligned during acquisition. The effect is pronounced with a small amount of drift between images. Irrespective of mismatched calibration frames, the effect can be eliminated by dithering all your images during acquisition by 10 - 15 pixels.

Dithering will resolve a large proportion of your current difficulties. But dithering must be agressive with DSLRs.

Flats - about 70 - 75% on your camera preview histogram is about right for starters.

There is a tendency to get bogged down in the detail. Unless you dither your shots you will spend all your time post processing artifacts out, which can be minimized by basic acquisition techniques.

Thanks Rowland  :)

I've been concentrating on the flats because my image seemed to get worse after apply them. I originally just integrated the un calibrated lights had the result wasn't too bad.

But yes, shots weren't dithered and is a concern. I printed this off last week.  ;)  , I will implement it the next time I'm out , big thanks  :)

Offline pfile

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Re: Batch processing help DSLR
« Reply #21 on: 2013 July 25 22:39:55 »
if you get autoguiding going it will become a lot easier to dither... it can be done automatically.

Offline MikeOates

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Re: Batch processing help DSLR
« Reply #22 on: 2013 July 27 09:13:53 »
Rod,

Just a quickie, if you do for the EL panel I linked to, get the battery box as well, it takes 8x AA batteries which is very compact & convenient, it only costs an extra £1 (without batteries of course).

Mike

Offline Rod771

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Re: Batch processing help DSLR
« Reply #23 on: 2013 July 28 02:34:14 »
Thanks for the tip Mike

Cheers

Rod