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Dr. Gordon Telepun, creator of the Solar Eclipse Timer App, 2019 Eclipse images using Seymour Solar Filters!

About Dr. Gordon Telepun and his Solar Eclipse Timer App, Dr. Gordon Telepun is a plastic surgeon who lives in Alabama, He is an expert eclipse photographer and eclipse educator with a special interest in the partial phase phenomena. The 2019 total solar eclipse was his fifth successful eclipse expedition. Gordon is the developer of the mobile app Solar Eclipse Timer, which is designed so he can be your personal guide and photography assistant through the stages of an eclipse. In 2019 the app was updated to its second version and was also released in a completely internationalized version in Spanish. The app geolocates to calculate precise contact times of an eclipse. It does audible countdowns to the contact times and max eclipse, announces when to observe for various partial phase phenomena and automatically calculates the clock times needed to achieve a perfect eclipse sequence image. More information can be found at

Gordon has allowed us to post the pictures taken by him during the 2019 Chile/Argentina eclipse using two Seymour Solar filters on his crucial setups, the following text is written by Gordon to explain the process.

Seymour Solar Caption To Image


My preference for solar filters is high quality glass that results in a yellow Sun disk image.  I think this is more aesthetically pleasing than filters that result in a white or bluish-white image.  For the 2019 solar eclipse in Argentina I used Seymour Solar glass filers on the two main camera setups.  The images in this partial phase image composite where taken with a Nikon D5000 camera at prime focus on a Takahashi refractor working at f10 with a 905 mm focal length.  The ISO setting was 200 and a shutter speed of 1/125 was used except for the last image which was 1/100.  The solar filter was Seymour Solar glass and you can see how clean the images are.


There are a number of important points about taking a sequence like this.


It is very difficult to focus on the full sun disk image when there are no sunspots.  Sunspots are an eclipse photographer’s friend!  If there are no sunspots as you prepare for an eclipse you MUST practice with your system, prior to the eclipse, focusing on the limb of the Sun.  It’s difficult because the limb is not crisp.  Use your camera’s magnifying feature in the LCD screen and practice focusing on the limb and then evaluate your results on your computer.  Get comfortable with it.


On eclipse day, when the partial phases progress and there begins to be a sharp point on the top or the bottom of the Sun, center that sharp point in your LCD screen, magnify it, and focus on that.  That sharp point is a much better thing to focus on than the regular limb.


The Sun has natural limb darkening around the edges.  When you are practicing prior to the eclipse pick a shutter speed that preserves this natural limb darkening.  This will make the center of the Sun disk the proper exposure.  Don’t try to make the entire Sun disk bright yellow.  If you over expose the Sun disk to bright yellow you also run the risk of having a faint blur of yellow around you Sun image bleed into the black edge.  Proper exposure is another area where sunspots are helpful if they are present.


The last portion of the crescent phase emits less light so depending on the spacing between you images you will need to increase your exposure of the final one or two crescent images both before C2 and after C3.  The tenth image in this sequence had the shutter speed slowed to 1/100 where all of the others were taken at 1/125.  But remember, this final crescent, which is almost the limb of the Sun is darker, it is more orange, so don’t over expose it.  But there is no way to practice for this ahead of the eclipse!  That is why you have to have proper exposure of the full sun disk image properly determined prior to the eclipse and then remember to just slow your shutter speed to increase your exposure by 1/3 or 2/3 stops.


Most eclipse photographers look at the partial phase image sequence as a problem that will be solved with an intervalometer set to take images at a fixed interval.  I do not do this because it does not take into consideration one of the astronomy nuances of an eclipse when you are not located at the point of Greatest Eclipse. The duration of time between C1 and C2 is almost never the same as the duration of time between C3 and C4. The only time it is close is at the Point of Greatest Eclipse. The further along you are to the beginning or end of the path, a rising or setting eclipse, the durations become very different. At Bella Vista in 2019 the time between C1 and C2 was 4440 seconds and the time between C3 and C4 was 3771 seconds. So the partial phase percentage visible progresses at a different rate before and after totality.  I take my first image 2 minutes after C1 and my last image 2 minutes before C2.  The time between is divided up evenly.  So for this eclipse the gaps between the first set of images, before totality, was 7m 46s, the gaps between the second set of images, after totality, was 6m 35s.


My app, Solar Eclipse Timer, is the only app in the world that calculates the proper timing of this sequence automatically.  It’s called the Partial Phase Image Sequence Calculator (PPISC) and once the app has calculated your 4 contact times it automatically does the math for you and delivers the proper 20 partial phase image clock times.  My website has a worksheet that you can download and use it to write down you clock times and your exposure notes.


More information can be found at


Thank you,

Gordon Telepun

Thank You Gordon! And Thank You to all of our loyal customers! Happy Viewing!

The Seymour Solar Team!

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What is the difference between a full aperture and off axis solar filter?

An off axis solar filter blocks light into the telescope by only allowing light through a small portion of glass that is off center. A full aperture filter allows the most light into the telescope because it allows the full aperture of your telescope to be viewed. This allows the best possible daytime viewing when there is minimal atmospheric turbulence. If turbulence is present, a mask can be put over the end of the filter to effectively reduce the aperture. With a mask you can effectively change the aperture range to anything less than full aperture depending on the size of the mask. An off axis solar filter cannot be used on a refracting telescope.

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Are the Solar Filters safe?

Yes. All of our Glass and Thin Film Solar Filters are safe for unlimited visual use and photography. Helios Solar Film and Helios Solar Glass® have been tested and meet the requirements for ISO 12312-2.

These filters block 99.999% of the sunlight and therefore are rated with a neutral density of 5. Careful handling and proper maintenance will ensure a long filter life.