An Advanced Processing Technique

for Lunar and Planetary Images

Uploaded 10/30/04

 Producing highly detailed images with a broad tonal value, yet retaining good contrast is the key to breathtaking lunar and planetary astrophotos. Here I present to you a technique to greatly enhance your lack luster moon shots, to something even the average viewer will be impressed with. This is not an unsharp masking or sharpening technique. It is a tonal masking technique that highlights low level contrasts without boosting grain.

The starting image.

The original is a fast, well focused exposure with my Pentax K1000 with E200. The scope however is an RFT, poorly suited for high resolution work, but excelling at wide fields with low coma. As you can see from the first image, the shot was rather unextrordinary, and even after a high level of unsharp masking in Photoshop, this was the best I was able to get after much experimentation in processing. So I knew that more could be seen if I could retain the resolution, but expand on the tonal range of the image. I came up with this technique, which I am going to share with you now.

Please click the thumbnails for the enlarged view (800 x 600)

 The original image, 1/500 sec with a 6 inch f/3.6 schmidt Newtonian. I have applied the unsharp mask at a fairly high level, but the photo still is lacking in tonalities.
 Copy the image to the clipboard and paste over original. Combine layers with "Multiply". You will get a rather dark contrasty image as seen here.
 The next two steps are crucial to get top results from this technique. First, we will only work on the background image. Turn off the top layer. Using the magic want tool, select the black sky around the moon. Get as much of the terminator as possible. Go to quick mask mode, and using the paint tool and a sizable brush, finish masking the last bit of terminator so only black sky remains. Go back to standard selection mode to see selection.
 Next, using the eyedropper tool, select a brighter area on the moon as a sample. Fill the black background around the moon. Why is this critical? because when you use the high pass filter on a sharp transition in brightness from the limb of the moon to black sky in our next step, you will get haloing which will show up in your final image as a limb brightening.
 We are next going to apply a high pass filter to this layer as seen here, BUT it will be with the top layer turned back on (this is an example of what high pass filtration does to the moon)
 Now turn on the upper layer, the combine method is still set for multiply. Select in the layers dialog box the bottom layer to work on only. Now apply the high pass filter to this lower layer only - while looking at the combined composite image. Adjust the amount to enhance the details such as rays and subtle variations in the seas and crater bottoms to suit. The image will look a bit dark at this point.
 Finally, when the image is rich and detailed, flatten the layers, and adjust levels to bring up the white point. (top slider)
 The Final image, full of detail and tonal variations !

Instrument: 6" f/3.6 Schmidt Newtonian Platform: Televue GEM Film: Kodak E200 CCD Autoguider: Exposure: 1/500 Filters: NONE Location: Payson, Arizona Elevation: 5150 ft. Sky: Seeing 8/10, Transparency 8/10 Outside Temperature: 10 C Processing: Photoshop HOME SCHMIDT GALAXIES EMISSION NEBS REFLECTION NEBS COMETS GLOBULARS OPEN CLUST PLANETARIES LINKS 


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