# Added to my astro rig



## griz (Jan 9, 2006)

The DEC axis came in today. New electronics and a keypad as well. Now I can set up an autoguider and do some narrow band. I am going to order a 50mm mini Borg scope tomorrow and the Lodestar guider camera in a week or so. It will all sit on a dual saddle atop the new axis. You need both axis to be motorized to guide. Thought about cobbling up a motor and clutch for the other camera mount but it was going to cost nearly as much as getting the real deal. haven't skimped on it so far so no need to do it now. Its working too well.










Cleared up today the atmosphere is still loaded with water vapor though I thought I might get out tonight but checking things out with the binos but the seeing was just too bad for any decent shots. Looks like a few clear nights coming up so I can test it out then. Going to Temple for some ankle biters Saturday. Finally get to test out the MkII on some action.

Griz


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## griz (Jan 9, 2006)

*Color in astro photos*

Some people have asked me about why you don't see color when you look through a telescope. And if the color in my images is false color like you often see in astro pictures.

The eye is essentially a 16 frame a second video camera. Speaking in computer terms the eye dumps its data/image to the optic nerve and brain 16fps which isn't long enough to develop any color information. There is over 100 minutes of combined exposure in the Orion shot. Even though its averaged and not added together. In some of the dust and gas clouds the wispy ones the actual photon capture rate is on the order of one or two a second so at 1/16th of a second for your eye its just not going to happen. So no there is no false color. The reds are attenuated a bit by the IR filter however in the 7D2 that is minimized. You can raise the frequency of the cut for the IR filter. Noone knows for sure yet but speculation is that the 7D2 has such a filter.

In astro shots you will see several predominant colors. Reds are hydrogen alpha hydrogen that has been heated up and ionized highest temp of the emission gasses. The teal color is hydrogen beta a slightly less agitated form of hydrogen. Blue is reflection from the bright stars off the cold gas. Browns and rust colors are dust particles mixed in with the gas. If you go to narrow band there are a few other colors you will see. The other two you don't see as often is oxygen III and a sulfur compound that has a gold color. Sometimes you see some green but its usually a product of skyglow or bad processing. Those are the colors of space in the visual spectrum pretty much. If you see others its most likely a false color image.

False color is used to allow you to visualize wavelengths you normally can't see. Uv and IR. There is a set of colors that is used most often called the Hubble palette. Basically they assign a color to a specific range of frequencies. And that is pretty much it. There are enough images out there these days its not hard to find one to calibrate your images. Its mostly a problem of getting the saturation up not getting colors spot on with astro work. They are weak to begin with and stretching and processing them drains the color off sometimes.

Griz


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## griz (Jan 9, 2006)

More goodies came in today. The dual saddle for the guidescope.










Griz


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