Orwell Astronomical Society (Ipswich)

Home Events

☰

Solar Total Eclipse, 26 February 1998

Four members of OASI travelled with Explorers Tours to Venezuela and the Caribbean island of Curacao to observe the solar total eclipse on 26 February 1998. All four enjoyed perfectly clear skies for the event and took many photographs! I travelled to the Paraguana peninsula in northern Venezuela where I took the images below using a 900 mm focal length folded refractor. The instrument functions as follows (see figure 1 below). An equatorially mounted 150 mm flat mirror directs light into the grey box which houses the 75 mm lens and three 85 mm flat mirrors to fold the light path. The third of these flats directs the light upwards to the SLR camera body on top. A slot in the side of the top section of the box enables a radial density filter (RDF) to be positioned in the light path during totality. This is an opaque metal disc glued onto a clear glass support: it introduces an obstruction into the light path which compensates for the intensity profile of the solar corona allowing a single exposure to capture detail from the Sun's limb to the edges of the frame.

During the partial phases of the eclipse, I used a Thousand Oaks type 2 filter in front of the lens for safe direct viewing through the camera viewfinder. It sits in a slot on the front of the box and is easily removed using a tab attached to the edge of the filter. The telescope is supported on three legs which I pushed 150 mm into the sand giving a very stable platform. I viewed the Sun throughout the eclipse by looked downwards into the camera, i.e. a fixed viewing position. This was particularly useful as the Sun was at an altitude of 62° at totality.

The partial phase lasted for 90 minutes: this gave plenty of time to practice tracking the Sun with the manual slow motions for the 150 mm flat mirror. Totality lasted for 3 minutes 45 seconds. The following images show a sample of my results.

Figure 1. The 75 mm folded refractor set up on the beach on the Paraguana peninsula awaiting the start of the eclipse.
Figure 2. As the last dazzling crescent of the photosphere faded from view at 2^nd contact, Bailey's Beads became visible against the pink chromosphere which itself showed several small flares.
Figure 3. Image of the corona taken around mid-eclipse using a one second exposure without a filter.
Figure 4. Image of the corona taken around mid-eclipse using the RDF. Note how it suppresses the range of brightness of the corona and makes more detail visible.
Figure 5. Image taken using the RDF close to 3^rd contact, as Bailey's beads start to become visible.
Figure 6. Totality ended at 3^rd contact with a brilliant diamond ring when the blinding photosphere reappeared through a deep lunar valley.

$folded_refractor.jpg$ Figure 1. The folded refractor.

Figure 2. Chromosphere and Bailey's Beads.

Figure 3. Mid-eclipse, unfiltered.

Figure 4. Mid-eclipse using RDF.

Figure 5. Bailey's Beads.

Figure 6. Diamond ring.

More Information on Eclipses

See Fred Espenak's eclipse web site eclipse.gsfc.nasa.gov/eclipse.html.

Mike Harlow