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Description
This all sky mosaic was created by Axel Mellinger and is used
in <i>SkyView</i> with his permission. A fuller description
is available at the
<a href="https://www.milkywaysky.com/">survey website</a>.
<p>
Between October 2007 and August 2009 a digital all-sky mosaic
was assembled from more than 3000 individual CCD frames.
Using an SBIG STL-11000 camera, 70 fields (each covering 40x27 degrees)
were imaged from dark-sky locations in South Africa, Texas and Michigan.
In order to increase the dynamic range beyond the 16 bits of the camera's
analog-to-digital converter (of which approximately 12 bits provide data
above the noise leve) three different exposure times (240s, 15s and 0.5 s)
were used. Five frames were taken for each exposure time and
filter setting. The frames were photometrically calibrated using
standard catalog stars and sky background data
from the Pioneer 10 and 11 space probes. the panorama has an
image scale of 36"/pixel and a limiting magnitude of approximately 14. The
survey has an 18 bit dynamic range.
<p>
The processing of these data used a custom data pipeline built using
IRAF, Source Extractor and SWarp.
<p>
The data used here were converted to three independent RGB color planes
of 8 bits each and provided to SkyView as a single 36000x18000x3 Cartesian
projection cube.
To allow users to efficiently sample data in a region of the sky,
this cube was broken up into 2100x2100 pixel regions with a 50 pixel overlap
between adjacent images. Tiles at the poles were 2100x2050.
<p>
In <i>SkyView</i> each color plane comprises a survey. The individual planes may be
sampled as surveys independently as Mellinger-R, Mellinger-G and Mellinger-B.
The color mosaics can be regenerated by creating an RGB image of all three
surveys. Since <i>SkyView</i> may stretch the intensity values within
each color, linear scaling and a minimum of 0 and maximum of 255 should
be specified to keep the original intensity scalings.
<p>
The full spatial resolution data is used for images of less than
30 degrees on a side. If a user requests a larger region, data are sampled
from a lower resolution 3600x1800x3 data cube. Please contact the survey
author if you need to use the higher resolution data for larger regions.
The Mellinger survey is only available in
<i>SkyView</i> through the website. SkyView-in-a-Jar cannot access
the underlying data. Provenance: Axel Mellinger. This is a service of NASA HEASARC.
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