Annular solar eclipse photography and experience
On October 14th, 2023, an annular solar eclipse was visible across North, Central, and South America. In the United States, the path of the eclipse stretched from Oregon to Texas. We report time series astrophotography of this event obtained from Robstown, west of Corpus Christi, Texas, the last location where the eclipse was visible in the continental United States. Our experience proved that successful astrophotography of a solar eclipse can be achieved despite significant cloud cover.
Our main objective was to photograph the different phases of the annular solar eclipse and attempt to capture Baily's beads. Baily’s beads are the rough edge of the moon causing spots of light to appear like a string of beads. Another objective was to create an annular eclipse photo mosaic and gain experience for the upcoming total solar eclipse on April 8th, 2024.
The path of the annular eclipse was 160 miles (257 km) away from the campus of the University of Texas in Brownsville, where we are based. Travel plans were made to ensure that we were on the path of the eclipse before the beginning of the event. Driving time to the designated observing site was about 2 hours and 30 minutes. A suitable, open space was located using Google maps before the day of the event. The location chosen to obtain photographs of the annular eclipse was the Richard M. Borchard Regional Fairgrounds (coordinates: 27.79, -97.65) in Robstown, Texas. This particular location was in the path of totality, has no obstructions such as tall buildings, and is located in an area with low population density. We were undeterred by the weather forecast for the day of the event, which predicted significant cloud cover.
We primarily used the Nikon Digital single-lens reflex (DSLR) camera, a 50-200-millimeter DX lens, a solar filter, and a tripod (Joilcan brand) with an apron. The solar filter used to protect the camera was a Daystar 50mm White-Light Universal Lens Solar Filter that uses 12312-2 ISO-certified SOLARITE film with a paperboard construction that you fold to assemble. This white light filter blocks out 99.9% of optical light and 100% of IR & UV light, making it safe for the equipment and observers looking though the view finder. We note that some Neutral-density filters do not remove harmful IR & UV light. The universal solar filter was chosen in order to have the ability to quickly exchange the filter between cameras. In addition to the digital camera, a Nikon F3, which is a 35mm film camera, was also used. This camera was used to capture the eclipse with a 50mm and a 210mm lens using Kodak Professional Ektachrome E100 Color slide film.
On the morning of the 14th of October, there was heavy cloud cover over South Texas. We were not discouraged by the clouds or the forecast for the rest of the day and drove to Robstown. During the drive up, the blanket of clouds had only small breaks. The parking lot adjacent to the fairgrounds was almost deserted at 10:00 am when we arrived (all times are in Central Time Zone). We encountered sustained winds of 30 mph from the NE with gusts up to 35 mph. Due to the wind, a vital piece of equipment was the tripod apron. The apron allowed us to place two five-pound weights to keep the tripod steady. As a safety precaution, the camera was removed from the tripod when we were not taking photos in case a strong gust would blow over the tripod. From arrival until annularity, the Sun was obscured by a heavy layer of relatively fast-moving altocumulus clouds with small breaks, (see Figure 1). Photos with short exposure times were obtained through the small breaks in the clouds. We had difficulty aligning the camera to the Sun, because the cloud cover would make the Sun unobservable when the solar filter was installed. The clouds were so thick that the Sun was possible to view with the naked eye, which was a beautiful sight to behold. Luckily when annularity began at 11:55 am, there was a large break in the clouds which would last until annularity ended. We were able to capture the entirety of annularity.
When we started to photograph, we decided to use a higher ISO and exposure times of 1 to 2 seconds to compensate for the limited sunlight though the clouds as seen in Figure 2 and Figure 3. With the longer exposures, multiple photos were blurred due to movement, which was induced by touching the shutter release or from the wind. As annularity approached, the clouds cleared allowing us to shorten the exposure time and reduce the ISO to the recommended 1/13th of a second and 64 ISO, respectively, to capture a balanced image of annularity, as shown in Figure 4. During the duration of the event, we experimented with different exposure times and ISOs to capture the Sun, which had varying brightness due to the inconsistent and varying cloud cover. As a result, we adjusted the ISO we used, as a function of cloud cover. The breaks in the clouds enabled us to take a sufficient number of clear images to create a photo mosaic of the annularity, which was one of the main goals (see Figure 5). During the entire event, we obtained a total of approximately 275 individual digital images. A few of which contained Baily’s beads.
After we had finished with the digital photography, we had enough time to attempt to capture the tail end of the eclipse on 35mm color slide film. We prepared the film camera the same way as the DSLR, by taping the solar white light filter to the 50 mm lens. We removed the view finder prism so we could frame and focus without using the view finder. We took 10 shots on the 50mm lens, bracketing them to have the best chance of finding the correct exposure. We switched to a 70 mm by 210 mm Vivitar lens and repeated the process of framing and bracketing to finish capturing the end of the eclipse. We enjoyed the experience of shooting on film and the anticipation of whether the images would come out useable.
Witnessing an annular solar eclipse was an amazing experience. During annularity, the sky darkened, the ambient temperature dropped, and even the birds, abundant in South Texas, became confused and sought a spot to spend the night. We hope this article will encourage others to take a chance and travel to the path of any future eclipse even if the forecast seems hopeless.
For the April 8th, 2024, total solar eclipse, we plan to obtain a remote shutter release. It is strongly recommended to have a shutter release and a tripod with weights to remove the possibility of shaking the camera. This is particularly important for longer exposures. We also plan to obtain a screw on or drop-in filter for a more secure connection to the lens to reduce the risk of the filter falling off. It also allows for smoother installation and removal of the filter when taking photographs during the different phases of the eclipse.