Walter's LogBook
	Sun/Mon August 15/16, 1999

My fifth night of imaging on the front porch in Oshawa. The sky wasn't as dark/transparent as last night, but still pretty good. The night was cut short as cloud came in just after 3:00. Low temperature was +14C, so I had to put on a coat at midnight (a few months from now, I'll be dreaming about +14C nights...). Tonight I imaged M57 and M27 again with the MX5C, paying closer attention to focus this time. Then I imaged M2 and M15 with the MX512, again with better focus! I am completely satisfied with these images, so now I can move on to some new objects!

Tonight's topics are Focusing and One Shot Colour...

Focusing

I have found that FWHM in x and y of about 2.5 and 2.0 respectively is usually about as good as I can get. Any bigger and the images lose detail and have rather bloated stars. My technique for focusing with MaxIm is to find a star that has a brightness of about 4000 with a 2-second exposure. I then continuously image a small subframe around that star (with 400% magnification in the window), and also use the "Inspect" feature's wireframe diagram and FWHM x and y numbers to determine when I have reached a reasonable level of focus. There is quite a bit of variation in the numbers, but if you are focused at 2.5 by 2.0, then those numbers should come up often with only a few occurrences of higher numbers. Of course, the final determination of focus is made by taking a full frame and looking at the stars to see how "tight" they are.

MX5C One-Shot Colour

When converting the raw MX5C images to colour in MaxIm there are a number of slider controls, buttons, and check boxes. The sliders I never use (they let you tweak the R,G,B levels). The only button I use is "Auto", which I click for each image. The check boxes (X Offset and Y Offset) are of more interest. The first time you do colour with an MX5C, you should try all four possible combinations of these and see what the image's colour looks like in the preview window. You only have to do this once, since the Offset is a property of the camera and shouldn't ever change.

Processing MX5C One-Shot Colour Images

When it comes right down to it, there are only two ways to process a bunch of MX5C shots: combine them and then convert them to colour, or convert them to colour and then combine them. The first way is the easiest. Unfortunately it doesn't really give much in the way of colour. So, as is so often the case, it's the harder way that gives the best results! As you convert each individual image to colour, you will probably be thinking something along the lines of "Man, these images really suck!" They do look awful don't they? The real magic is in the combination of colour images, when the colour image finally emerges in all its glory!

M57	10 minutes (20 x 30s)
Better focus than my last night's image...

Processing steps for image above:

• Each of the 20 frames was converted to colour and saved as a new file.
• The 20 colour frames were combined using the "Manual with Centroid" function.
• The pixels were squared.
• A high pass filter was applied to the image.
• The resulting image was saved as an 8-bit TIFF using a screen stretch with a gamma of 1.2.
• JPEG conversion was done using a 70% Quality factor.

Interestingly enough, I did not have the "pink sky" problem with M57 that I had yesterday, so the processing was much simpler this time around!

M57	10 minutes (20 x 30s)
The December 2000 re-processed version...

Processing steps for image above:

• Each of the 20 frames was converted to colour
• All were combined (Process/Combine menu option)
• DDP FFT low pass with medium hardness
• High pass filtered twice
• The pixels were squared.
• JPEG conversion was done using a 50% Quality factor.

M27	21 minutes (42 x 30s)
Much better focus than last night's colour image!

Processing steps for image above:

• Each of the 42 frames was converted to colour and saved as a new file.
• The 42 colour frames were combined using the "Manual with Centroid" function.
• The background and range levels were tweaked slightly on the histrogram.
• The resulting image was saved as an 8-bit TIFF using a screen stretch with a gamma of 1.0.
• JPEG conversion was done using a 50% Quality factor.

M15	5 minutes (10 x 30s)
My final version of M15.

Processing steps for image above:

• The 10 frames were combined using the "Manual with Centroid" function.
• The pixels were squared.
• A high pass filter was done on the image.
• A straight-line histogram specification was performed.
• The resulting image was saved as an 8-bit TIFF with a Gamma=3.0 stretch.
• JPEG conversion was done using a 70% Quality factor.

M2	5½ minutes (11 x 30s)
My final version of M2.

Processing steps for image above:

• The 11 frames were combined using the "Manual with Centroid" function.
• The pixels were squared.
• A straight-line histogram specification was performed.
• A high pass filter was done on the image.
• The resulting image was saved as an 8-bit TIFF with a Gamma=3.0 stretch.
• JPEG conversion was done using a 70% Quality factor.