MarsWatch 1996-1997

Images of Mars from Astronomers Around the World

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Linking Amateur and Professional Mars Observing Communities

for Observational Support of the Mars Pathfinder Mission

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M970315.JPG, MI970315.JPG, M970315A.GIF

Mars images acquired during the night between March 15 and 16 1997 using the "Morais" semi-apochromatic refractor of Pino Torinese Observatory (D.42 cm F/16) at direct focus (for the tri-color images) and with a Barlow lens (1.85 x) for the infrared sequence. The camera was an ISIS CCD-800 (KAF-400 chip, 768x512 pixels, 14 bit A/D converter).

Each monochrome image is the enhanced sum of several normalized original frames. The true color images are the result of the composition of many images in different lights. From the infrared sequence also an animated GIF was obtained (m970315a.gif).

Number of frames per image:

• B filter: from 10 frames
• V filter: from 10 frames
• I filter: from 5 to 20 frames
• True color with B V I filters: 30 frames

The enhancement was obtained by

1. Image restoration using the Van Cittert algorithm
2. Fourier filtering using the Butterworth low-pass filter
3. Contrast enhancement using unsharp masking
4. Image rescaling using biquadratic interpolation to bring the images acquired at two different focal lengths at the same dimensions
5. Histogram stretching for exposure matching

Exp.times:

• 2.00 sec with B filter (centered at 420 nm)
• 0.15 sec with V filter (centered at 530 nm)
• 0.05 sec with I filter (centered at 820 nm) at direct focus
• 0.10 sec with I filter and the Barlow lens

Authors: A.Leo, G.Quarra, P. Tanga
San Gersole` Planetary Group - Florence (ITALY)
U.A.I. - Planetary Section, Mars Program