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Wednesday, October 23, 2013

RGB Imaging Planetary with a Mono CCD

I've tried planetary imaging over the years with limited success. I learned quickly that single images just weren't that good. I found that all of the great planetary images were taken by combining video frames and stacking them into one image. I attempted this with the movie mode of my Canon T3i.

 Taking the next step, I decided to get a camera dedicated to planetary imaging. I chose the QHY5L-II because of it's ability to also act as an autoguider for deep sky imaging. So since June 2013 when I got the camera there has been a lot of trial and error. I haven't quite got it down yet, but I'm learning. I decided to pass on my workflow so far.

1. The Equipment

The telescope I use is a 15+ year old 8" Meade LX-50 SCT. This is a F/10 telescope and I usually use a 2x's Barlow making the telescope F/20. A longer focal length is desired for planetary. The longest focal length I've heard of being used successfully for planetary is F/40, F/20 seems to work works fine. I've also imaged planetary with my 4" refractor, a 2 year old Orion ED102T CF with decent results. I plan on upgrading my SCT in the future with something larger with better glass, perhaps an 11" SCT.


2. Acquiring the Image

I've learned since June that sky conditions or "seeing" is very important. It may appear to be a clear night, but the atmosphere may be turbulent resulting in less than perfect images. I've found that sometimes imaging with my Barlow lens is next to impossible due to the increased magnification.
 The morning of the 21st the skies were clear and bright due to a nearly full moon. There was a slight haze, so I guessed the atmosphere was calm. I probably captured my most detailed images to date.

I've been experimenting with different frame rates and gain with the QHY5L-II. Usually I have the gain at 50% or better. This results in a "grainy" image, but I capture at least 2000 frames in less than a minute. I try to keep my FPS(frames per second)  at least 35. With all the planets some rotation will occur. I try to keep my Jupiter videos about 60 seconds due to rotation.
I shoot 1 video through each color filter, red,green & blue. In this example each video was about 1 minute long and about 2100 frames each.

Below are single Red, Blue & Green frames from the videos taken, shown in the stacking program AutoStakkert. The single frames are very grainy, but it gets better!


3. Aligning & Stacking the Videos

AutoStakkert automatically aligns the images if they are recorded using the same image size. In the example above all the videos were taken in a 1024x768 format. This is important because the RGB images will need to be stacked later. I used about 60% of the 2100 frames recorded for each color

Once stacked some of the graininess has been removed due to stacking 1000+ images. These are the red, green and blue videos aligned and stacked:


4.Wavelet processing via Registax6

Next the aligned and stacked RGB images need further processing. This is where the images really start to come to life. There are many great tutorials online dealing with Registax and wavelet sharpening. I'm still learning this myself. Shown below is the red frame in Registax6 after wavelet processing, sharpening & de-noising

5. Combining RGB images

Once wavelet sharpening and de-noising adjustments have been made the resulting RGB images need to be stacked and color applied. It's important the each image is aligned or the RGB stacking process won't work. Again as I mention before, I found AutoStakkert works great for aligning the RGB frames to each other during stacking.  There are several programs that will auto-stack RGB images or it can be done manually in Photoshop. I choose to use StarTools:



I select my red, green and blue images and StarTools does the rest. Again this can be done manually in Photoshop by "colorizing" each layer & using the "lighten" command on the top 2 of the 3 frames.

StarTools does this automatically & I've also used Nebulosity with similar results.



6. Post Processing & Final Adjustments

Once my RGB images are "stacked"  further sharpening & de-noising may be necessary. I choose to use Astra Image, although Registax or another program may be used.
Before sending this image to Astra Image, I rotated it  in StarTools*

The final image 

I decided to send the image one more time through Astra Image for more wavelet sharpening:

I've only been at this style of planetary imaging since June and haven't had many clear nights to experiment. Hopefully my results will improve with more practice!

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