Dark Frames when binning

[PhotoGav]

Hello all,

I am preparing myself for the plunge into mono CCD imaging, so please excuse my lack of knowledge and probably silly questions, but it's always better to ask before rather than after...

I will be creating a library of dark frames for calibration purposes, but should I make a library of both 1x1 bin and 2x2 bin to apply to the subs shot at the relevant binning?

Thanks,

[johnrt]

Yes, but depending on your choice of CCD you may not require darks at all, I haven't used them with either my Atik 314l+ or 460ex.

[ChrisLX200]

As above, yes - create a separate library for each binning level. Despite the low noise of these Sony sensors I do find dark frames essential for recovering faint details. I did find that once you get down to about 0 deg C the improvement of going to an even lower temperature is very small. Which is just as well because the Atik490EX that I use only has a Delta-T  of -25deg. Dark frames are temperature dependent so your library will only be useful for images taken at the same temperature. I'm not sure the stabilisation is that great either because I had to replace a library recently because it was over-compensating (resulting in black holes instead of normalising the background).

ChrisH

[PhotoGav]

Thanks John. I've gone for the Kodak KAF-8300 chip, so hear that I will need to use darks...

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[johnrt]

Thanks John. I've gone for the Kodak KAF-8300 chip, so hear that I will need to use darks...

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Yes in which case a decent set of darks is required. As Chris says just match the temperature as closely as possible for each binning mode.

[PhotoGav]

Excellent, thank you for the advice both. Can't wait to get started and suss it all out!

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[Zakalwe]

Don't forget that the colour data doesn't have to be that sharp, so you can take *some* liberties with it. For example, a mild Gaussian blur would be more than likely sufficient to cover up any noise without impacting the overall finished product.

Absolutely use calibration frames for the Luminance layer as all the detail is stored in the Lum. That needs to be a sharp and as noise-free as possible.

Here's a really good demonstration of this:

http://lefevre.darkhorizons.org/articles/colorbinornot.htm

[ollypenrice]

There are alternatives to darks, which I no longer use in standard form. I stack in AstroArt 5 (easy, logical, controllable, fast and effective.)

In AA5 you can make a Defect Map. Mine comes from a 30 minute master dark. In Arithmetic you just clip 2000 ADU from the black point and this is your defect map, for which AA has a box on the stacking page.

In the box intended for darks you just put a master bias.

I like this system because it gives the cleanest results. Darks sometimes seem to do almost as much harm as good. It also means that one Defect Map fits all exposure lengths (but binning would need its own. I don't bin, myself.) I use the big, noisy full frame Kodak sensors and get exellent results. I also have a 'repair column' feature which is good because two of the cameras have column defects which is one of those things with CCD. The column is always perfectly repaired. I also run the hot pixel filter quite aggressively, set to 60%.

Enjoy the camera. CCD is great!

Olly

PS You do the defect map in Arithmetic - Clip.

[PhotoGav]

Thanks for that Olly. I use Nebulosity for stacking, so will see if similar things can be done with that.

[lensman57]

Excellent, thank you for the advice both. Can't wait to get started and suss it all out!

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Depending on the make of your camera building a darks library is very easy. Use the set point cooling to -20 C, even an Atik should be able to reach this, and do the darks during the daytime for each Bin mode and exposure times, 300s, 450s, 600s, 900s and 1200s. This will save time , during the processing have the dark optimisation checked in the stacking software.

A.G

[Zakalwe]

There are alternatives to darks, which I no longer use in standard form. I stack in AstroArt 5 (easy, logical, controllable, fast and effective.)

In AA5 you can make a Defect Map. Mine comes from a 30 minute master dark. In Arithmetic you just clip 2000 ADU from the black point and this is your defect map, for which AA has a box on the stacking page.

In the box intended for darks you just put a master bias.

I like this system because it gives the cleanest results. Darks sometimes seem to do almost as much harm as good. It also means that one Defect Map fits all exposure lengths (but binning would need its own. I don't bin, myself.) I use the big, noisy full frame Kodak sensors and get exellent results. I also have a 'repair column' feature which is good because two of the cameras have column defects which is one of those things with CCD. The column is always perfectly repaired. I also run the hot pixel filter quite aggressively, set to 60%.

Enjoy the camera. CCD is great!

Olly

PS You do the defect map in Arithmetic - Clip.

I've not used it, but I think that the Bad Pixel Map in Nebulosity is similar? Allied with dithering and Bias files a BPM can dispense with the need for darks.

[lensman57]

I've not used it, but I think that the Bad Pixel Map in Nebulosity is similar? Allied with dithering and Bias files a BPM can dispense with the need for darks.

The problem with Neb3 bad pixel map is how to incorporate this into the confusing and long winded process, something that I wish Mr  Stark would look into. There is also the provision for something similar in PI but I don't know how to use it.

A.G

[Zakalwe]

The problem with Neb3 bad pixel map is how to incorporate this into the confusing and long winded process, something that I wish Mr  Stark would look into. There is also the provision for something similar in PI but I don't know how to use it.

A.G

I know what you mean. I can't be bothered with using New for stacking as it's all a bit of a faff. I don't know with Craig Stark didn't automate the process as all you are doing is loading the output of the last stage into the input of the next stage.