How to choose your Binned level

 

Setting up your binned level correctly is very important. If your set wrong you will have problems getting clear pictures. Here is a simple formula to help figure out the correct setting for your camera and scope. You want about 1.5-2 seconds per pixel

 

206* pixel size (microns)/ focal length (mm) Using my set up as an example. 10"LX200 with 416 CCD

206*9/7500=.25 arc seconds per pixel @ F30 4x4 or 8x8 binning

206*9/5000=.37 arc seconds per pixel @ F20 4x4 binning

206*9/2500=.74 arc seconds per pixel @ F10 2x2 binning

206*9/1575=1.18 arc seconds per pixel @ F6.3 1x1 or 2x2 binning

206*9/825=2.25 arc seconds per pixel @ F3.3 1x1 binning

My telescope is a 10" LX 200 F10 with a focal length of 2500mm. My camera is a 416 with a pixel size of 9 microns. To figure out different focal length when using a focal reducer or barlow. Simply take scope focal length times the barlow i.e. 2x barlow would be 5000mm. If using a focal reducer, simply take your focal length times the reducer, i.e., f6.3 would be 2500*.63=1575. Just move the decimal point one place to the left.

Looking over this setup you can see that F3.3 has no problem using 1x1 binning. F6.3 could use 1x1 if the mount is stable and tracking is good, but could be switched to 2x2 making each pixel 2.36 arc seconds. F10 will need to be switched to 2x2 giving 1.48 arc seconds. F20 can be set to 4x4 giving 1.48 arc seconds per pixel. F30 could be set to 4x4 giving 1 arc second but will require a stable mount and stable atmosphere. Or can be set to 8x8 giving 2 arc seconds per pixel.

 

q. Why would you want to set binning so high?

a. By having more arc seconds per pixel you can remove distortions caused be unstable air, poor tracking, and vibrations

q. Wont setting the Binning higher drop resolution?

a. Yes, it will. But most images will be shot in the F3.3 and F6.3 range. Going higher will give you a poor image because of bad seeing. Remember that turning up magnification also magnify any distortion. Setting Binning higher can prevent this.

q. Other then removing distortion, vibration, and tracking errors, are there any other befits?

a. If each well can handle 65536 electrons of light before it starts blooming, by combining 4 wells in to one super well, you have increased it's holding capacity by 4 when binning at 2x2. So this allows you to take longer exposures of fainter objects, even if a bright star is near by without blooming that area because the well is saturated.