F.A.Q.
Observations
Can I use freely BASS2000 data?
Data available through the BASS2000 web site are exclusively for science and educational use. For publication, data providers should be directly asked for. In case of commercial use, please contact us.
Where can I find older spetroheliograms?
Go to the Multimedia Galley (link on the bottom of the left menu). then in the “Spectroheliogrammes » directory to access digitized older observations.
Where is solar north on spectroheliograms?
It’s oriented towards the upper side of the image. All full Sun images are straightened (except for USER-Brussels images)
Which images are used to build synoptic maps?
Filaments are obtained using H alpha observations
What is the rate of observations available at BASS2000?
For visible observations, we publish between one and three daily observations, approximately, weather permits at observing places. Nançay RadioHeliograph data (when the instrument works normally - it is currently in upgrade mode) continuously observe the Sun as long as antennas can track it. Nançay Decametric array also observes continuously the Sun except during Jupiter’s visibility as Jupiter is a priority for the instrument. Coimbra and Brussels provide one image a day for each wavelength. CLIMSO, at Pic du Midi observatory send 3 images a day.
Where are N, S, E and W on solar images
Except for USET-Brussels observations where slope of the Sun should be corrected, N is up, and W is on the right, as is the use in solar physics.
Are lines identified on vacuum or in air?
All wavelength values are given in vacuum.
When were Meudon images first recorded on a CCD camerai?
It began the 13th of May, 2002.
Some Halpha files from Meudon contain 5 images. What does it correspond to?
It corresponds to 5 wavelengths, related to central wavelength of the line shifted respectivement by -1/2, -1/4, 0, +1/4, +1/2 Angstrom. The central image is then the one for the central wavelength.
Are images corrected from P0 angle?
Yes, except for Brussels’ USET observations. (P0 correction to apply can be find under the “Ephemerids“ link, in the left menu)
How can I download an important amount of observation?
On https://bass2000.obspm.fr/data in /pub directory, one can find all data providers instruments. For each instrument, various datasets can be accessed through sub-directories where recent data are sortes by year and month. Older data can be accessed using a “Olderdata“ alias.
How can I obtain a solar grid?
In the left menu, item “Tools/Ephemerids“ brings you to a web page where you can enter the required date and hour.
Solar spectrum
In what units are solar spectrum axis?
Abscissa gives wavelength in Angstrom, while ordinate provides a count rate in arbitrary units. Data are normalized in % of the continuum, which is to be determined for each part of the spectrum. Blue note under solar spectrum gives information about normalization.
Is it a quiet or an active sun solar spectrum?
This is an averaged quiet sun spectrum.
Can I use directly solar spectrum data, not using web interface?
Data are available in BASS2000: https://bass2000.obspm.fr/data in /pub/spectrum directory.
Do Earth atmosphere lines appear in solar spectrum?
Yes pour visible and IR wavelength as observations were ground-based. On the contrary, UV observations, obtained from SUMER instrument of SOHO spacecraft, in space have no contamination by Earth atmospheric lines.
Where can I find information about the way solar spectrum was obtained?
On the lower part of the spectrum page (https://bass2000.obspm.fr/solar_spect.php?lang=en ) you can find links towards PDF files describing the way spectra were obtained.
How can I know the corresponding chemical element of a line on the solar spectrum?
When you move the cursor above the spectrum, wavelength automatically appear. You just have to clic on the location of the max (or min) of the line and chemical element as well as transition responsible for the line (and some few other information) appear in a small window.
Are the indicated wavelength values given in vacuum or in air?
All written wavelength are given in vacuum
Is solar spectrum plotted in vacuum or in air?
It is in vacuum (this explains why there are some differences between axis and written value.
Is solar spectrum continuous from UV to IR?
No. there is a gap between 2000 and 3500 Angstrom. We lack data there and have no hope of filling it in the short term.
Does solar spectrum correspond to whole Sun flux, or is it local?
Spectrum is obtained with a slit, ranging from North pole to South pole. Il is averaged along the slit’s heigh, the over a series of observations ranging during several years.
Are wavelength corrected from the respective movements of Earth and Sun?
Yes. Doppler effect is corrected.
Tools
Can I download an image of the grid of coordinates for the solar disk?
Yes. You just need to go to the page https://bass2000.obspm.fr/ephem.php and enter date of interest to get back a grid, in .png format.
How can I obtain a grid of solar coordinates?
In the left menu, item « Tools/Ephemerids » gives access to grids for the required dates.
What is the unit for the area of NOAA active regions?
It’s millionth of solar hemisphere.
Synoptics maps
Where can I find synoptic maps of the solar activity?
In the left menu, in the “Query“ item, choose ‘Synoptic maps’. Then a pull-down menu, on the top of the page, allows to choose the date of the beginning of the rotation, or the Carrington rotation number.
Which images are used in order to build synoptic maps?
Filaments come from H alpha observations, active regions from Ca II K3 data, and sunspots from Ca II K1 data.
What do hachure density mean, for filaments, in synoptic maps?
The closest the hachures, the steadiest the filament. Details on the building of synoptic maps can be found in https://bass2000.obspm.fr/data_guide.php?what=18
Where can I find recent synoptic maps?
There are no synoptic maps since 2008, but we hope to create the again in the short term.
Solar features
Where can I find information about Solar Features?
Last line of item “Query“ on the left menu is a link towards Heliophysics Feature Catalogue from HELIO, which is a database containing several solar features, some of them since 1996.
What is the unit for the area of NOAA active regions?
It’s millionth of solar hemisphere.
WDC-Solar Activity, Regular Member of 
Last update: 18 Jul 2024 14:10