Observation Log - May 31, 2001

Observation Log - May 31, 2001 - Tinton Falls, NJ

[Nice night, fairly cool for the season, with temps in the 40's. Dew point was high tonight, so I had the Kendrick on low power from the beginning. Received a new, shorter nose-piece for the MX516 from AVA, so thought I would give it a test on some color shots for once. So the setup on the 12" LX200 was: Crayford, f6.3 reducer, Homeyer filter wheel w/True Tech RGB filters/IR blocking filter in the MX516 nosepiece/MX516. Took darks and flats during evening twilight, and did flats for all filters separately. -GW]

Here is M94, a spiral galaxy in Canes Venatici, magnitude 8.2, 14' x 12', surface brightness 10.0 mag/sq arcmin, distance is 33 million light years, width is 120,000 light years. This is an LRGB image, with all exposures taken between 9:28 and 1:05 a.m. the morning of May 31, 2001. The luminance channel was a 56-minute integration from 1-minute exposures, while red was 40 minutes, green was 32 minutes, and blue was 24 minutes. The images were calibrated using MaxIm, with separate flats for each of the four channels. Each was aligned and composited, and a Digital Development filter (FFT, low-pass, hard) was applied to each channel. Then the four were aligned and combined into a full-color image, with a 50% luminance weighting, and r/g/b ratios of 1.75/1.35/1.15. The resulting image was tweaked for color plane alignment, and the resulting image was finished with a contrast enhancement.

Next is M13, a globular cluster in Hercules, magnitude 5.9, diameter 20', distance is 26,000 light years, diamter is 150 light years, age is 14 billion years. This is an LRGB image, with all exposures taken between 1:22 and 3:39 a.m. the morning of May 31, 2001. The luminance channel was a 15-minute integration from 1-minute exposures, while red was 10 minutes, green was 18 minutes, and blue was 21 minutes. The images were calibrated using MaxIm, with separate flats for each of the four channels. Each was aligned and composited, and a Digital Development filter (FFT, low-pass, hard) was applied to each channel. Then the four were aligned and combined into a full-color image, with a 50% luminance weighting, and r/g/b ratios of 1.25/1.2/1.0. The resulting image was tweaked for color plane alignment, then processed with a Digital Development filter (FFT, low-pass, hard), then an unsharp mask (FFT, low-pass, hard). The color saturation was reduced to 50%, and the resulting image was finished with a contrast stretch.

The last object of the night is NGC7027, a planetary nebula in Cygnus, magnitude 8.5, diameter 14", distance is 3,600 light years, central star is mag 16.3. This PN is also known as PK84-3.1. All exposures taken between 3:53 and 4:24 a.m. the morning of May 31, 2001. This was a 24-minute integration from 1-minute exposures. MaxIm was used to align and composite, and a Digital Development filter (FFT, low-pass, mild) was applied, and the resulting image was finished with a contrast stretch.

I expected there was more detail in the core, so I ran another processing, using a Digital Development filter (kernel, low-pass, more) and a contrast stretch. This brought out a little more detail. I tried yet another trick, this time resampling the image immediately after compositing to double the image scale. Then I applied a Digital Development filter (FFT, low-pass, mild), an unsharp mask (FFT, low- pass, hard) and finally a Maximum Entropy Deconvolution. This final image was cropped, and finished with a contrast stretch. As a comparison, here is a Hubble image, reduced to roughly the same scale and orientation.