AGAIN A GREAT AMERICAN ECLIPSE
Total Solar Eclipse of 8 April 2024
USA - Arkansas, Nimrod Lake, +34°57'50.7" N, 93°12'35.8" W, 80 m a.s.l.
Local circumstances: C1 17.32.30, C2 18.49.31, max 18.51.39, C3 18.53.47, C4 20.10.24 UT, dur 4m17s
by Lorenzo Comolli, Emmanuele Sordini, Alessandro Gambaro

Updates:
20/6/2024: most of the images uploaded (TEC140, flash spectrum, contacts, video, field images...)

8/8/2024: new article on gravitational deflections of stars during the total solar eclipse of 2024. Verification of the Einstein theory using standard  amateur instrumentation, 105 years after the first measurement of Arthur Eddington during the 29 May 1919 total solar eclipse (see 3rd image here below or click here for full article).
18/9/2024P75@500mm+ASI2400MC,  HDR corona Canon100-400@150mm+Canon6D
25/9/2024P75+Canon90D reprocessed with better flat field
Coming soon
: EDPH61@268mm+ASI2600MM, P75@1000mm+ASI294MC, 80ED@500mm+ASI2600MC
Come back here in the future to see more images.

HDR Corona with TEC140

Click for hires
The HDR corona from the TEC140+ASI6200MM setup. A great quantity of fine details is visible all along the corona. Prominences were added from C2 and C3 contacts, red coloured. Moon edge is clearly oval due to the long duration of this eclipse (more than 4 min), and during the image acquisition the Moon moved. This is the biggest setup of our eclipse expedition and it was extremely difficult to take this setup from Italy. The telescope has beed dismounted in 3 pieces and two big suitcases were necessary for transportation via airplane.
The camera is a ASI6200MM, a full frame of 61 Mpix 16 bit monochrome, and it was a first time for us uf using an astronomical camera instead of a reflex camera. This was possible thanks to the big improvement in download speeds of modern camera, e.g. this big frame sensor is downloaded to PC in less than half a second!

TEC140 apochromatic refractor (dia 140 mm, FL 1011 mm, f/7.2), ASI 6200 MM camera (CMOS full frame 62 Mpix, 16 bit monochromatic, binning 1, 3.76 um/pixel, cooling at 0°C), ZWO AM5 mount, Luminance filter, exposures between 1 ms and 512 ms at 1 EV stops at gain 100 (equivalent to 680 ISO, EV stops from 15.9 to 3.9), 381 frames used summing for a total of 52.2 s of net exposure captured during 187 s of gross duration. Image capture via an automated sequence in SharpCap recording data at 2 fps with a data flux of 242 MB/s into a SER file.

Image processing by Lorenzo Comolli. Image setup controlled by Lorenzo Comolli. This image is a collaboration between Lorenzo Comolli, Emmanuele Sordini and Alessandro Gambaro.


Click for hires
Rectangular projection of the above image. The radial structures can be appreciated in a different prospective.
Image processing by Lorenzo Comolli. Image setup controlled by Lorenzo Comolli. This image is a collaboration between Lorenzo Comolli, Emmanuele Sordini and Alessandro Gambaro.

Click for a detailed article
Gravitational deflections of 54 stars. Click on the image for a detailed article with much more details about the gravitationa deflection as forecasted by the Einstein theory, a small introduction on the Eddington experiment and the method used for this measurement.
Image processing and analysis by Lorenzo Comolli. Image setup controlled by Lorenzo Comolli. This image is a collaboration between Lorenzo Comolli, Emmanuele Sordini and Alessandro Gambaro.



HDR Corona with Pentax75+ASI2400MC

Click for hires
The HDR corona with medium field of view. Raw data obtained by my friend Gianni Galli from another location, only 7 km from my location. Setup composed of a Pentax 75 apo refractor (500 mm f/6.7) and a ASI2400MC cmos color camera, controlled via the same Sharpcap script I've used for my setup. A lot of stars are visible thanks to the large field of vew, while mainteining good details in the corona.
The center of the image (Moon, prominences and the very inner corona only) are from the TEC140+ASI6200MM setup, because the data from the Pentax 75 was unfortunately ruined a little bit by thin clouds.
Pentax 75 apochromatic refractor (FL=500 mm, dia 75 mm f/6.7), ASI 2400MC
(CMOS full frame 24 Mpix, 16 bit monochromatic, binning 1, 5.94 um/pixel, cooling at 0°C), Ioptron Skyguider Pro mount, exposures between 1 ms and 512 ms at 1 EV stops at gain 140 (equivalent to 465 ISO, EV stops from 16.5 to 4.2), 1044 frames used summing for a total of 151 s of net exposure captured during 208 s of gross duration. Image capture via an automated sequence in SharpCap recording data at 7.7 fps with a data flux of 362 MB/s into a SER file.
Note: image location is not the one at the top of the page but very near, only 7 km at North:  USA - Arkansas, Ola Lake, +35°01'45.4" N, 93°14'02.9" W, 120 m a.s.l.
Image processing by Lorenzo Comolli. Image setup controlled by Gianni Galli. This image is a collaboration between Lorenzo Comolli and Gianni Galli.


HDR Corona with Canon 150mm + Canon 6D

Click on the image for high res version. MOUSE OVER for star magnitudes. Look also to the hires with star magnitudes.
The HDR corona at large field of view. Image setup piggybacked on the TEC140 mount. Setup composed of a Canon 100-400 photographic lens set at 150 mm focal length and a Canon 6D camera with Magic Lantern software onboard and controlled via an internal eclipse script. Many stars are visible thanks to the large field of vew. The center of the image (Moon, prominences and the very inner corona only) are from the TEC140+ASI6200MM setup.
Canon 100-400 lens set at 150 mm f/5.6, Canon 6D magic lantern, ZWO AM5 mount (setup mounted on the same mount of TEC140, on the counterweight bar, exposures from 8 ms (1/125 s) to 1 s at 1 EV stops at 400 ISO, 244 single RAW images captured during totality.

Image processing by Lorenzo Comolli. Image setup controlled by Lorenzo Comolli and prepared by Emmanuele Sordini. This image is a collaboration between Lorenzo Comolli, Emmanuele Sordini and Alessandro Gambaro.


HDR Corona with Pentax75+90D

Click for hires
The HDR corona with medium field of view. Obtained with a "standard" setup, i.e. a Canon reflex camera, while most of the other images from this expedition where obtained with astronomical CMOS cameras (like the ASI6200MM on top). The difference in the noise and details is quite noticeable. This image was also penalized by a bad flat field that increased the noise and reduced the visibility of fine details. With the same setup we shot also the 2017 and 2019 eclipses.
Pentax 75 apochromatic refractor (FL=500 mm, dia 75mm f/6.7), Canon 90D (32 Mpix, RAW files), Kenko NES mount, exposures between 1/250 s and 1 s at 200 ISO, plus 1 s at 400 ISO. 177 total exposures were used.
Image processing by Lorenzo Comolli. Image setup controlled by Emmanuele Sordini. This image is a collaboration between Lorenzo Comolli, Emmanuele Sordini and Alessandro Gambaro.



Flash spectrum
The Flash Spectrum is the spectrum of the Chromosphere during the very few seconds after C2 and before C3. This part of the atmosphere of the Sun has an emission spectra, on the contrary of the Photosphere with an absorpion spectra. The Chromospere is visible only for a few seconds at the C2 and C3 contacts, so this is the reason for the name "flash". We used a monochrome sensor without filters, gaining the full spectral sensitivy of the sensor from 330 nm to 1000 nm. The colors in the images below are pseudo-real colors, added to the BW original image.

Images at C2 (above) and C3 (below), QHY5III-174 camera (1920x1200 pix, 5.86 um, 12 bit monochrome, gain 0 equivalent to 672 ISO, USB 3.0, 77 fps i.e. 338 MB/s of data flux), optics made with a Atik 0.5x doubled (FL=100 mm, dia 25 mm, f/4), Star Analyzer 200 reticle (31.8 mm 200 lpm reticle placed in front of the lens), 13 ms exposure, each of the two above is an average of 800 frames from C2+0s to C2+10s and from C3-10s to C3+0s. The spectrum is strongly defocused in the left and right regions becase unfortunately we forgot to add a diaphragm designed to close the optics to f/9 so to improve optical quality.
Image processing by Lorenzo Comolli. Image setup controlled by Emmanuele Sordini e prepared by Lorenzo Comolli. This image is a collaboration between Lorenzo Comolli, Emmanuele Sordini and Alessandro Gambaro.

A "professional" processing of the data at C2, made by our friend Paolo Berardi. The maximum SNR has been obtained by curving the chromosphere and vertical averaging the lines. Moreover the continuum spectrum has been subtracted. In this way, tens of emission lines are clearly visible. See above for tech data.
Image analysis by Paolo Berardi. Image setup controlled by Emmanuele Sordini e prepared by Lorenzo Comolli. This image is a collaboration between Lorenzo Comolli, Emmanuele Sordini and Alessandro Gambaro.


Video of totality with a GoPro

Recommended: 1080p, full screen, audio on.
The video of totality with our main setups and the eclipsed Sun in background. The video starts about 1 minute before C2 contact and shows the authors moving around the telescopes, removing the solar filters at C2-30s, checking the data recording of the cameras, obsering visually with a Pentax 75 refractor, taking ambient measurements and taking a group photo.
Video setup is a GoPro Hero5 camera at 2.7k resolution, large field, automatic exposure and sensitivity.
Video setup controlled by Lorenzo Comolli. This video is a collaboration between Lorenzo Comolli, Emmanuele Sordini and Alessandro Gambaro.


Prominences

Click for hires
Solar prominences at the C2 and C2 contacts from the TEC140 setup, with also the chromosphere at maximum visibility. Rectangular projection, so the circular profile is converted in a straight image. Look at the hires image for full details and scroll left-right the image at 100% resolution.
TEC140 refractor (1011mm f/7.2), ASI6200MM, ZWO AM5 mount, 0.39 ms exposure at gain 0 (equivalent tot 215 ISO, EV=15.9), average of 23 images per contact, processing with Autostakkert 3 and Registax 6.

Image processing by Lorenzo Comolli. Image setup controlled by Lorenzo Comolli. This image is a collaboration between Lorenzo Comolli, Emmanuele Sordini and Alessandro Gambaro.

Click for hires
Sequence of C2 and C3 contacs at 4.1 fps from the TEC140 setup. 25 images per side show a total duration of 6 s per side. The very fast change in the solar appearance is clearly appreciable expecially in the high resolution version.
TEC140 refractor (1011mm f/7.2), ASI6200MM, ZWO AM5 mount, 0.39 ms exposure at gain 0 (equivalent tot 215 ISO, EV=15.9), image capture at 4.1 fps.

Image processing by Lorenzo Comolli. Image setup controlled by Lorenzo Comolli. This image is a collaboration between Lorenzo Comolli, Emmanuele Sordini and Alessandro Gambaro.

Click for hires
Sequence of C2 and C3 contacs from the Pentax75+Canon90D setup. 20 images per side show a total duration of 12-10 s per side. Unfortunately the continuous shooting of the reflex camera was not at a constant framerate as the TEC140 setup.
Pentax 75 refractor (500 mm f/6.7), Canon 90D, Kenko NES mount, 1/2000 s exposure at 100 ISO.
Image processing by Lorenzo Comolli. Image setup controlled by Emmanuele Sordini. This image is a collaboration between Lorenzo Comolli, Emmanuele Sordini and Alessandro Gambaro.



Sequence of the complete eclipse with a 50 mm lens
 
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Sequence of the full eclipse from C1 to C4 on a single image at 3 min intervals. This is a classic goal for eclipse astrophotograpy, that at the time of film photography was obtained on a single film piece, and now with digital imaging is obtained from many shots added together via software BUT with the requirement that pointing of the camera is maintened fixed.
Sequence 
obtained with a Canon 6D baader, Canon 50 mm f/1.8 used at f/5.6, exp 1/30 s during partiality (with solar filter) and 0.25 s during totality (without filter), 100 ISO, 3 min intervals. The last 6 frames were digitally added because pointing of the camera was not perfect and the Sun went outside of the field.


Large field HDR group photo during totality

 
Click for hires
The authors in a group photo taken during totality. This was a goal of our expedition, something to take with us in the future as a reminder of the expedition. Taken near mid totality, with the eclipsed sun at the top, with Venus on the bottom right, the double setup of Alessandro on the left (Pentax75 and EDPH61), the authors in the middle (from left Emmanuele, Alessandro, Lorenzo), on the right the setup of Lorenzo (TEC140) and at extreme right part of our car with engine on for powering all the instrumentations and PC. Also a buffer car battery (in the middle bottom) is present. Btw powering all our setup was very difficult because we found many unexpected problems caused by the long time under the Sun before the eclipse, heating all the PC and mounts.
HDR composition obtained at mid totality with a Canon 6Dmk2, Samyang 14 mm f/5.6, exp 2.5s, 0.66 s, 1/6s, 800ISO.



All Sky HDR during totality
 
Click for hires
An All Sky shot gather all the sky in a single image, a very important feature when the time is limited like during an eclipse totality!
HDR composition obtained near mid totality with a Canon 6D, Peleng 8mm f/5.6, exp 4s, 1s, 1/4s, 800ISO.


Rectangular projection of the above all sky image. The orange/pink horizon is at 360° but it is visible only in a small part of the horizon due to the trees. At left the telescope setups and authors while taking the group photo (see below).



Environmental measurements
A solar eclipse greatly influences the Earth atmospere. The temperature, relative humidity, luminance data show typical trends, peculiar to each eclipse and location.
During this eclipse I've used a T/RH datalogger with the sensors positioned at 1 m heigth on a small tree, on the side in shadow from the Sun light. This way data are quite reliable and much less influenced by the ground temperature respect to the measurements I've made in the past eclipses. In this eclipse I've found a 5°C decrease, to be compared to 9°C in 2017 USA Wyoming, to 4°C in 2006 Egypt, to 7°C in 1999 Hungary.
A digital luxmeter measured the horizontal luminance: this is a really interesting measurement, that show the tremendous fall of the light, between full Sun at 110000 lux and totality at only 1.8 lux, to be compared to 3.4 lux 2017 USA Wyoming, 4.1 lux 2006 Egypt. The lower value, in my opinion, is due to 2 reasons: first the eclipse was quite long and deep (as confirmed by the SQM reading below), and second the selected location was surrounded by many trees, reducing the ambient light coming from the horizon.
During totality I've measured the sky brightness with a SQM-L, obtaining 13.56 mag/arcsec^2, that is equivalent to the twilight sky when the Sun altitude is -6°C, i.e. civil twilight. Do you what to feel how dark is the sky during totality? Wait for the civil twilight, that is about 30 min after sunset!

Here are the plots of:
  • temperature
  • relative humidity
  • luminance





Landscape and instrumentation images

Click on the image for landscape and instrumentation images of the authors and telescopes.



HDR image processing of a Total Solar Eclipse

Click for the PDF presentation
If you're interested in processing your HDR corona, I invite you to follow the tutorial that Lorenzo Comolli prepared after the USA 2017 eclipse. On 27 January 2018 Lorenzo was invited by VVS association in Belgium for presenting at the Astrofotografiedag 2018, a conference about astrophotography. One of the presentations was on how to process the great American eclipse. Look also to the other presentation on the dedicated page.




Any comment about the images is highly appreciated, email me at comolli@libero.it


HTML Editing and Publishing by Lorenzo Comolli. Email me at comolli@libero.it.
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