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At present, all BBSO instruments save data in standard FITS format,
In addition, JPEG images are generated by our data archive process for
quick-look purposes. Selected images are made available on our public FTP
server. Additional images are made available by request.
The following is from our original FTP site from the early 1990s. You are very unlikely
to see any of these ancient file formats, but this information may be useful for
historical purposes. In general, all images on our current public FTP site are either
standard FITS images or JPEG images. Some information, such as that on image orientation,
may still be useful. The Quantex and Eyecom image processors no longer exist.
The Megavision went to the landfill long ago.
All images from them have been converted to standard FITS files.
The Datacube, which is used in the video magnetograph (VMG), still exists, but images from
it, as it says below, are now standard FITS files. It is still possible that you may
run into some of the old file names, though. They will all have the extension .FTS.
********* BBSO IMAGE HELP FILE *********
1. Brief Description of BBSO Files
Available over Computer Networks
Types of Files Available:
H-alpha full-disk images
Vidomagnetograms (longitudinal and transverse)
Dopplergrams
High-resolution "white light" images
Full-disk white light images
Full-disk Ca II K line filtergrams
High-resolution H alpha images
High-resolution images in other wavelengths (e.g. He 10830 A,
3862 A, 4642 A, VG14 filter, 3933 A (10 A bandpass), etc.
Availability of files depends on the current observing program. File
are kept on the system for at least one week after the date of observation.
File Name Description
The file names in the public access area consist of a name of from
6 to 8 characters in length followed by an extension. The name gives
information about the type of image, the date of observation, and
(optionally) the order of distribution. The extensions give information
about the format of the file.
The name consists of a one-letter prefix, three letters indicating the
month of the observation, two numbers indicating the day of the month
the image was made, and (optionally) a letter indicating the order
in which the image was saved if there are more than one of the same
type on the same day.
Example:
Prefix Date Order Extension
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+---+ | +-+ +-----+
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VOCT31A.DAT
Prefix values are:
C High-resolution H-alpha filtergram (usually center line)
D Dopplergram (usually 6103 A)
F Broad-band filter image (3862 A, 3933 A (10 A bandpass), etc.
see image file header for wavelength
H Full-disk H-alpha center line image
I High-resolution "white light" image (usually 6103 A)
K Full-disk Ca II K line image
M He 10830 A image
P Special polar videomagnetogram
V Longitudinal videomagnetogram (usually 6103 A)
X Transverse field line map (usually 6103 A)
W White-light full-disk image
Extensions:
FTS standard FITS format image (readable by IRAF, etc.)
DAT "BBSO FITS" format image
EY "BBSO FITS" format image from Eyecom image processor
PIC Megavision format image -- used by Megavision image processor
in Caltech Solar Astronomy Department
GIF Graphics Interchange Format for personal computers
Image Orientation
The orientation of VMG's (V) and direct images (I) are so that
south is to the top of the frame and east is to the right. Note
that in this paragraph directions are geocentric, not heliocentric.
In the image files the first row of the image is the southernmost row.
The orientation of Ha (C) images from the 26" center bench is also south
to the top of the frame and east is to the right. Broad-band 26" west
bench images (F) have north to the top and east to the right.
Note that on many FITS viewers (such as IRAF) the BBSO VMG images
appear upside-down, with north at the top.
On Ha full disk images (H) south is to the top and west is to the
right, while for full disk K-line (K) and white light (W) images
north is at the top and west is to the right. H-alpha full disk
images are corrected for solar position angle so that the south
solar pole is at the top of the frame. K and W images are not,
so that geocentric north is at the top of the frame. This is
because the K and W images are taken using a small telescope with
a fixed upside-down camera mount.
File Formats
Available file formats include standard FITS format (readable by IRAF),
GIF (for PC's) and several internal BBSO formats. The standard FITS
files may have 8 or 16 bits per pixel. Other formats are always
8 bits per pixel.
[Section 2, dealing with using FTP on VMS and other obsolete programs, omitted.]
3. Description of BBSO Image Formats
Used Internally at the Observatory
This section describes the format of the BBSO image files.
There are several types of images available from Big Bear Solar
Observatory. These include standard FITS files, "BBSO FITS" files,
and other formats. This section only deals with BBSO FITS disk files.
BBSO FITS in this case refers to files with a FITS-like format, but
on disk rather than tape. FITS files consist of a header followed by
image data. On the disk the file is stored in 512-byte blocks. The
header consists of a variable number of 512-byte blocks, followed by
the data also in 512-byte blocks. The header is similar to the
header on a FITS tape image file.
The BBSO FITS disk files are of three types, called Quantex, Datacube, and
Eyecom (referring to the image processors used to create them).
Quantex and Datacube files are quite similar to each other, while
the Eyecom files are somewhat different.
At this time the only "BBSO FITS" format files likely to be found in
the public access area are Eyecom image files (.EY extension).
Internal BBSO Filenames
The filenames used internally at BBSO are somewhat different from
those found in the public access area. While outside users should
encounter these names only rarely, some information about the names
is provided below.
The filenames are intended to give the user some information
concerning the file contents.
Quantex files are named according to the following scheme:
ommmddsss.DAT (or .FTS if converted to standard FITS)
where
o is the observations type, one of V (longitudinal VMG),
I (direct image), Q (-Q image), U (+U image), or D
(dopplergram)
mmm is the month (JAN, FEB, MAR, etc.)
dd is the day of the month
sss is a "sequence number", assigned to each Quantex
image in order after 0h UT.
Sometimes the sequence number is omitted for files in FLEA:[PIX];
such files are representative images for a given day.
Datacube files are named according to the following scheme:
ommddssss.DAT (or .FTS if converted to standard FITS)
where
o is the observations type, one of V (longitudinal VMG),
I (direct image), Q (-Q image), U (+U image), D
(dopplergram), or X (transverse field line map)
mm is the month (01 = January, etc.)
dd is the day of the month
ssss is a "sequence number", assigned to each Datacube
image in order after 0h UT.
Sometimes the sequence number is omitted for files in FLEA:[PIX];
such files are representative images for a given day.
More recent Datacube files are also stored in the following format:
omddssss.FTS
where
o is the observations type, one of V (longitudinal VMG),
I (direct image), Q (-Q image), U (+U image), D
(dopplergram), or X (transverse field line map)
m is the month (1 = January, 2 = February, etc., but A = October,
B = November, C = December)
dd is the day of the month
ssss is a "sequence number", assigned to each Datacube
image in order after 0h UT.
More recent OSL CCD images are similar. These formats were devised for greater
compatibility with DOS PC ("8.3") file names.
Eyecom images have two possible types of names:
The first type is:
ommmddsss.DAT (or .FTS if converted to standard FITS)
This type of name is the same as the Quantex-style names, except
that the observation type will be one of:
H full disk H-alpha image
K full disk Ca II K line image
W full disk white light image
C H-alpha image from the 26 inch center bench
The second type is of the form:
ommmdd.EY (or .FTS if converted to standard FITS)
where
o is the observation type as above
mmm is the month
dd is the day of the month
"BBSO FITS (or .DAT and .EY)" File Structure
******
Note: Due to historical reasons, the "BBSO FITS" format is **NOT**
the same as the real FITS disk formats supported by IRAF or IDL. Real
FITS files at BBSO have the extension .FTS. The difference is in
the size of the header disk blocks and the logical block size of
the file (512 as opposed to 2880 bytes).
The .FTS files in the public access area ARE standard FITS files
similar to those produced by IRAF.
This section is added for those curious about the .DAT file format.
The header information is also the same as in the .FTS files. The
.DAT format is now obsolete and has been replaced by standard FITS
format.
******
A Quantex or Datacube image file consists of a header followed
by data. The header and data are each contained in a whole number
of 512-byte disk blocks. Within the header blocks the header
information is organized in 80-byte lines, the last line containing
the word END followed by 77 blanks. A header line in general
consists of an 8 character keyword, an equals sign, a space, 21
characters of data related to the keyword, a slash (/), and 48
characters of comment about the data. A keyword of COMMENT may
be followed by 72 characters of any kind. The first keyword is
always SIMPLE, and its value is always T. CRVAL1 and CRVAL2 are
the RA and DEC offsets from center Sun, with west and north positive.
BITPIX indicates the "size" of the pixels (currently always 8 bits).
NAXIS1 and NAXIS2 show the length of row and columns, respectively.
This is an example of a Datacube image file header:
SIMPLE = T /
BITPIX = 8 /
NAXIS = 2 /
NAXIS1 = 512 /
NAXIS2 = 481 /
BZERO = 0.00000 /
BSCALE = 1.00000 /
OBJECT = 'BB#2293 ' /prominence
TYPE-OBS= 'DOPPL ' / 64 FRAMES
SEEING = 2 /
CTYPE1 = 'E-W ARCS' /
CTYPE2 = 'N-S ARCS' /
CRVAL1 = -914 /
CRVAL2 = 297 /
TIME-OBS= '17: 9: 3' / 3.15 SEC SPREAD
DATE-OBS= '19/ 9/90' /
ORIGIN = 'BBSO ' /BIG BEAR LAKE, CA
TELESCOP= ' 10"' /
OBSERVER= ' m/v' /
FRAMES = 64 /
DELTAT = 4 /
BIAS = 15 /
GAIN = 4 /
COMMENT ORIGIN FILE NAME CLAW:[DCIMAGES]D09190110.DAT
END
This is an example of a Quantex image header.
SIMPLE = T /
BITPIX = 8 /
NAXIS = 2 /
NAXIS1 = 512 /
NAXIS2 = 481 /
BZERO = -1.27000E+02 /
BSCALE = 1.00000E+00 /
OBJECT = 'BB# 2290' /ACTIVE REGION
TYPE-OBS= 'VMG ' / 384 FRAMES
SEEING = 2 /
CTYPE1 = 'E-W ARCS' /
CTYPE2 = 'N-S ARCS' /
CRVAL1 = -45 /
CRVAL2 = -415 /
TIME-OBS= '16:11:10' / 13.30 SEC SPREAD
DATE-OBS= '19/ 9/90' /
ORIGIN = 'BBSO ' /BIG BEAR LAKE, CA
TELESCOP= 26 /
OBSERVER= 'M/V ' /
FRAMES = 384 /
DELTA-T = 13 /
BLACKLEV= 3 /
WHITELEV= 3 /
COMMENT ORIGIN FILE WAS NAMED VS2:[DISKMG]VSEP19057.DAT
END
For Quantex and Datacube images, if the header lines do not fill
up the last block of the header, the remaining space is filled
with junk characters.
The "BBSO FITS" Quantex and Datacube formats are obsolete, and
have been replaced by standard FITS format files.
Eyecom images are similar to the other two types. The difference lies
in how the header is treated. For the Eyecom images, the last line of the
header need not be a complete 80-column line. If the current header block
ends before the end of the last line of the header (but after the word END)
the header ends at that point.
The image data start at the beginning of the next block, and continue
to the end of the file. For all current BBSO images, the data are
stored as unsigned 8-bit bytes. Quantex and Datacube images are
481 rows by 512 columns. Eyecom images are 481 rows by 640 columns.
If a block ends in the middle of a row, the row is continued in the
next block.
Eyecom images are typically also available in standard FITS format.
[This information from 1995 or so.]
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