Fe XI, 789.2 nm
Our expedition observed emission from several ions in the visible
and near IR wavelength range. The strong emission of Fe X (637.4 nm),
Fe XI (789.2 nm) and Fe XIV (530.3 nm)
enables to create high resolution images. These emission lines provide an excellent
diagnostic tool
for probing the physics of the solar corona. One of these tools is clear from the following graph.
Fe XI line at 789.2 nm is very interesting because
Fe XI ion is the most
dominant ion of all Fe ions in the solar corona.
Even though Fe XI is a relatively strong near-IR emission line, it
is not easy to obtain an image of Fe XI. It is not as simple as deep sky photography of emission
nebulae where only sufficiently narrow band filter is needed to isolate the emission line. The emission in
the
solar corona is dominated by continuum - photospheric light scattered on free electrons. The light emitted
by different atoms and ions is very weak relative to the continuum. See the following two unprocessed images.
The left one was taken through a narrow band filter (bandwidth 1 nm) with a transmission band centered on the
Fe XI 789.2 nm emission line. The right image was taken through a filter with transmission band
outside the Fe XI line in the continuum. It is clearly visible that the left image is highly
contaminated
by continuum irradiance. It is not advisable to use a filter with a narrower band of transmission because
the emission line is thermally broadened. If the filter is too narrow, the situation becomes even worse.
Therefore it is necessary to make a precise photometric calibration of all images and then subtract the
continuum - the right image from the left one. You may see these two images as an
animation.
The full resolution version of the Fe XI image (2.6 arcsec/pixel) you may find
here.
Click on the image or on the following reference to display the
higher resolution image version (1.1 MB, PNG format).
|
| Image | TSE_2024_Fe_XI_Sims.png |
| Date | 08. 04. 2024 |
| Time | 2nd contact 18:48:17 UT, 3rd contact 18:53:03 UT (duration 4 min 17 s) |
| Place | Sims, Arkansas, USA |
| Coordinate | N 34° 38.1787', W 93° 41.4097', Alt. 230 m |
| Conditions | Clear sky, solar altitude at mid-eclipse 61.9° above horizon |
| Optics | 2× Zeiss Tele-Tessar 4/300 mm equipped with following narrow band filters:
on-band filter: Alluxa, center wavelength 789.2 nm, bandwidth 1 nm
off-band filter: Alluxa, center wavelength 782.2 nm, bandwidth 1 nm |
| Camera | 2× ZWO ASI0294MC Pro |
| Exposure | 0.025 s - 3.2 s |
| Processing | Composition of 344 eclipse images (172 on-band and 172 off-band) taken with two cameras. Images were calibrated by means of dark frames and flat-fields, aligned by means of phase correlation, composed by means of LDIC 6.0 software, continuum was removed from Fe XI emission by subtracting the off-band images. The resulting image was processed using Corona 5.0 software in order to visualize coronal structures. The final processing was done using ACC 6.1 software.
Image processing by Miloslav Druckmüller |
| Software | Astro D3F 2.0, PhaseCorr 8.0, LDIC 6.0, Corona 5.0, Sofo ACC 6.1 |
| Orientation | Image must be rotated 26.8° counter-clockwise to achieve standard orientation i.e. solar North up. |
| Copyright | © 2024 Matěj Štarha, Shadia Habbal, Miloslav Druckmüller |
|
Miloslav Druckmüller
Institute of Mathematics, Faculty of Mechanical Engineering
Brno University of Technology, Czech Republic
druckmuller@fme.vutbr.cz
|
Page last update: 20.6.2024
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