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Observing Report   -   Total Solar Eclipse March 29th, 2006 in Side/Turkey

Introduction

    In spring 2006 my wife and me flew down to Turkey to observe the total solar eclipse on March 29th, accompanied by a crowd of people and colleagues from the 'Heidelberg Astro-Stammtisch'.
    Several reasons made this trip really easy and comfortable for us: pretty good local infrastructure, easy access by aircraft from Frankfurt via Antalya, a pretty long eclipse duration of almost 4 minutes and - last but not least - a nice environment with turkish culture, food and historic monuments. Finally we were also grateful for this opportunity to drop out of the pretty harsh European winter of 2006 just for a week with sun and relaxing at the beach. My local colleague Andy Bender (www.astropic.de) took the effort to organize travelling and hotel for all of us (although I have to say, you kind of over-organized that Raki evening somewhat, Andy ! Anyway I can't really remember it clearly :-).
    Best regards and many thanks to all participants (Andy B., Peter H. aus N., Michael + Christa L., Alex S., Reinhard S., Christina M. and, of course, Sabine W.) for this exceptionally nice week in the turkish sun in spring. It should also be noted that our hotel near Side (Blue Waters Resort Hotel) contributed a lot to the pleasant stay and thus to the success of the whole expedition.

    Apollo's temple on the Side sea shore

Equipment

    I wanted to shoot digital photos of the sun and also observe by eye, both simultaneously if possible. Aircraft limitations on hand baggage put tight constraints on the size of my equipment. So I decided to carry with me a small APO telescope with photographic correction (flat field) for the 35mm film format (Pentax SDHF D=75mm, f=500mm, f/6.7) plus a reasonable binocular (Fujinon FMT-SX 10x50) on a simple azimuthal mount without motors (the swiss-made AYO mount). Support for this comes from a stable carbon tripod (Velbon CF-730). Photography was done using a state-of-the-art digital full-format (35mm format) Canon DSLR (Canon EOS 5D). Weight-wise this all summed up to roughly 12 kilogramms of stuff (case excluded). All the optics and camera was transported in hand baggage for safety reasons. Before and after totality all telescopes were kept covered by certified filter foils (providing high optical quality) with neutral density of 5, i.e. diminishing the light by a factor of 100.000x. The setup is shown in the picture below, which was taken during the first partial phase of the eclipse.

    My wife Sabine is looking at the partially eclipsed sun through the binoculars.
    On the right I have mounted my Canon 5D DSLR camera on a small Pentax APO telescope
    (with built-in field flattener). Both are covered by certified filter foils with neutral density of 5.

Informational Material

    The ultimate web site for eclipses (sun, moon, planetary transits) is authored by NASA's Fred Espenak . Check it out for all details on ephemeris, observational hints, maps and tables. Some of the material below is drawn from Fred's site (unless otherwise noted) by his kind permission:

    (All data below concerning Eclipse Predictions by Fred Espenak, NASA/GSFC).

    Total solar eclipse 2006 - details
    Global view of the eclipse geometry
    Time table for selection of towns in Turkey
    Lunar limb profile

    The central eclipse line almost exactly hits the city of Manavgat on the Turkish seaside of the mediterrenean sea. The small town of Side, which is a pretty touristic resort today, has been an important city back in greek and roman times. It is situated right on the cape directly left (west of) Manavgat. Obviously it was ideally suited for obeserving the eclipse. In fact our observing site was situated just 2 miles (3km) down the coast east of Side near the 'Blue Water Resort Hotel'. The following coordinates apply:
          Latitude: 36:45:33 N = 36.759 N
          Longitude: 31:24:31 E = 31.4087 E

    Map of the solar eclipse path in southern Turkey ( © by F. Espenak, NASA/GSFC)
    (source link)

    Exact times have been calculated by Michael L. as follows (in local time, which is equivalent to UT + 3 hours):
       1. contact:    12:38:20
       2. contact:    13:54:55
       3. contact:    13:58:44
       4. contact:    15:13:32
       Center of totality :    13:56:49


Links

Photography

    Dimensions

    Starting off it's advisable to check if focal length and chip size are fitting to the photographic problem. All photos were taken with a Pentax SDHF 75 (f=500mm, f/6.7) as the lens mounted on a non-modified Canon 5D digital camera (DSLR) which is equipped with a full-size 35mm chip (24mm x 36mm chip size, 12.8 MegaPixels). See the table given by Espenak for a bunch of suitable image scales:

    Canon 5D camera specs:
    • Pixel size: 1 Pixel = 3.5 arcsec = 8.4micron = 0.0084mm
    • Pixel number: 4368 x 2912 Pixel = 12.8 MegaPixels
    • Chip size: 36 x 24mm
    Lens specs:
    • Diameter D=75mm, focal length f=500mm, focal ratio f/6.7
    Specs for the complete setup:
    • Field size: 2.7 x 4.1    = 5 x 8 Ds    (Ds= solar diameters 0.5)
    • Size of the solar disk: 5mm = 514 pixel
    • Pixel size at the sun's distance: 2500 km
    • Size of the earth at the sun's distance: 17.3 arcsec = 5 Pixel
    • Pixel size at the moon's distance: 6 km

    The field size is 2.7 x 4.1, so the setup can cover the solar corona out to radii of 5-8 Rs (solar radii). I.e. we should try to take pictures as deep as to show the corona at this distance from the sun. The size of the solar disc on the chip is rougly 4mm, only. Thus we cannot hope to catch really detailed pictures of solar prominences, the focal length is too small to allow this. The size of prominences and lunar limb details can be estimated from the scales given above.

    .

    Exposure times

    Espenak's page of exposure times for solar eclipses is an excellent guide for preparing photographic observations of solar eclipses. Given a specific radius of the corona that shall be reached by the photo, he provides exposure times as a function of aperture and ISO speed. As a preparational check I shot some test photos the day before the eclipse, using my full camera + telescope setup and with an excellent optical foil with neutral density of 5 (provided by Baader in Germany). All numbers provided by Espenak indeed have proven to be both very accurate and useful.

    What are the limiting factors for exposing photos of solar eclipses ? At the very short end, shutter speed is limiting exposure times, although it must be said, that modern DSLRs can reach 1/8000 sec, which is pretty fast (compared to former times where an analog state-of-the-art Nikon F3 provided 1/2000sec as the shortest speed). At the long end, we are limited by the rotation of the earth, which moves the image of the sun across the CCD and spoils image quality at some point. (Of course, you can and should use a motorized mount to compensate for that, but I could not afford to bring along such heavy equipment, and many people will face the same problem, I guess). It's easy to calculate the maximal time that you may expose without image shifts on the detector. This is a function on focal length and of pixel size, of course. Declination effects also do matter, but we may assume decl=0 for the sun in our case here.
       1h = 15 degrees
       1 sec = 15 arcsec
       1 pixel = 3.5 arcsec = 0.28 sec = 1/4 sec exposure time
    So I could not expose longer than 1/4 sec without having the sun smeared out more than 1 pixel by the earth's rotation. In reality, we can afford a little longer, because of the imperfectness of the air (turbulences, seeing) and optics, plus the effects of the sampling theorem. It's good to be aware of what the limits actually are in numbers. If required, you may calculate the limiting exposure time (i.e. defined by shift by 1 pixel) with the following formula: t = 13680 * dx / f, where you should substitute: t limiting exposure time in sec, dx pixel size in mm, f focal length in mm.

    Another problem is the movement of the moon across the disk of the sun. This happens on a longer/slower timescale, though. The approximate angular velocity can be estimated by dividing the path length (2x solar diameter of 0.5) by the time between 1. and 4. contact (155 minutes). This results in an angular velocity of 0.4 arcsec/sec. Given the scale of my pixels in the focus of my f=500mm lens (3.5arcsec/pixel), the moon moves across 1 pixel in roughly 9sec of time. This number puts an upper limit on the number of photos that you can stack exactly using the edge of the lunar disk in front of the sun. My 4 x 3 exposures were made in an interval of 63arcsec, so the total shift amounts to roughly 7 pixels. So positioning all exposures by using the lunar disk limb will not be an exact procedure in my case here. One may expect some loss of corona detail, if only the limb is used.

Time Schedule

    In order to reach good signal to noise ratios in the final images, I planned to take several exposures with identical shutter speed and stack those on the computer. In addition, you need to take exposures of different exposure times to bracket the whole (or at least a bigger part of the) dynamical range of the corona. During testing it turned out however, that the total time needed quickly reaches the total eclipse time available. But I wanted to have time to look as well, of course ! So I compromised on a total time of 2min to spend for photography, resulting in the plan to shoot 4 different shutter speeds, each with 3 identical exposures.

    I also planned to take photographs only in the first half of totality, then take off the camera and observe visually. Doing photography first was useful, because I could use the non-critical time before totality for focusing and arranging everything. The foil filter (on top of the front lens) does not shift the focus of the telescope, so the pre-totality focus could be reused in totality, too.

    The series of 3 identical exposures was shot with a Canon timer device and using mirror locking (6 timer impulses with 1 sec of delay in between). This procedure reduced the danger of making errors. Locking the mirror avoids residual movements of the telescope at the time of exposure.

    One should keep in mind that DSLR may run into buffer full problems when shooting large and fast series of RAW exposures. Waiting for the write buffer to be freed while precious totality time is wasted - could be a potential nightmare. So I tested everything in beforehand. I did not encounter any problems, simply because you need some time to change the shutter speed and so you do not shoot continously. Storing in Jpeg does ease this problem also. I had absolutely no problems with my Canon 5D, even when using RAW (10 MB per image), although I had no especially fast CF card installed.

    I should also remark that the clock of my camera was mis-adjusted. I had a shift in time of 215sec and still had a time setting on CEST, instead of UT or local time. So image times are converted to local time by adding 1 hour and subtracting 215 sec (local time in Turkey = CEST + 1h = UT + 3h). I measured this shift by calibrating with the exposure of the 2nd contact (imgae #2528 take at 11:58:32 CEST).

Single Shot Images

    In order to capture a large dynamic range , I took exposures as follows (EV differences provide the difference in aperture steps):
    - prominences (1/1000 sec)
    - inner corona (1/60 sec, +4 EV)
    - outer corona (1/8 sec, +3 EV)
    - dark side of the moon (1/2 sec, +2 EV)

    All exposures taken together are covering a dynamic range of roughly 9 aperture steps. When adding the internal dynamics of one picture to this, we end up with a total dynamic range of roughly 15 aperture steps.

    Below you find some non-processed single images taken during totality. They were binned by a factor of 5 and have medium (80%) Jpeg quality only. All images were taken at a setting of 200 ISO. No further processing (except camera-internal processing of course) was applied.

    Click on any image to enlarge it !

    Totality image taken at shutter speed 1/1000 sec (left, EV=0) and 1/60 sec (right, EV=4).

    Totality image taken at shutter speed 1/8 sec (left, EV=7) and 1/2 sec (right, EV=9).

Image Composits

    Below you find two composite images composed from all shutter speeds (1/1000, 1/60, 1/8, 1/2 sec), rebinned to 1/3 of the raw resolution. Each single shot was processed with Pellet's method. This works as follows: first of all, images are filtered/smoothed in tangential direction only, erasing most corona structures, which tend to have radial direction. (Photoshop filter Blur/Spin, which corresponds to rotating the image around the center of the solar disk). These unsharp masks get subtracted from the original image, resulting in images with radial structures only. These images are multiplied into the original (non-filtered) image in order to enhance radial structure. Finally, all images of different exposure times are overlaid and added into one single composite. All processing steps were performed in Adobe Photoshop CS2.
    One cannot hope to realistically show the extreme luminosity and dynamics of the solar corona in any such image (especially not so because of the limited colour resolution of web-based 8-bit images). This is obvious from the considerations of corona dynamics above. Total dynamics exceeds 15 aperture steps (so >15bit of depth in luminance would be required). So by necessity, the image is shown in a pretty much compressed mode here.

    It is interesting to note the big prominences (at least 4) on the left image. The minimum corona shows strong structure, with pronounced axis symmetry (the maximum corona shows central symmetry instead). The sun's rotation axis is oriented from lower left to upper right. The left image very nicely shows the visual impression we had when looking at the totality with binoculars or in the telescope at low power.
    The picture on the right had a little bit more enhancement with respect to radial structure, in order to optimize corona detail in the outskirts. Coronal spikes can still be detected out to at least 3 solar radii.

    Please click on the images for a full-frame view and switch your browser to full frame mode (using F11 in MS InternetExplorer).

   

Two image composits (each made of 4 single exposures) taken during totality in Side.
Both are processed with Pellet's method and reproduced at 1/3 of original resolution.
The left image fits very well the visual impression we had of the eclipse. The right picture puts more emphasis
on the outskirts of the corona showing the prominent spikes reaching out to large radii
(Please click on images for full frame views!)


Observing Report

    We arrived on sunday just 3 days before the eclipse and were spending our days in a kind of 'alerted' mood. We did some sports, enjoyed the excellent food, went to Manavgat and Side and finally also made tests of our equipment and procedures that we had figured out. (However, I am going to be real silent about the 'Raki' business of Andy's here !). The hotel got more and more crowded as time went by and the day before the eclipse it seemed completely booked out. I guess that 80-90% of all people had especially come to see the solar eclipse. Although, some really lucky guys dropped in accidentially and all of a sudden wondered what all the camera and telescope equipment in the gardens was to mean. We had many groups from Germany, some 50 Indians, 30 US people, guys from Austria and the Netherlands...

    Weather conditions were improving more and more in the days before. The satellite images indeed looked very good on the very day of the eclipse. On the morning of March 29th, the sky showed no clouds at all and we were all very happy to be that lucky (there was an initial estimate of 40:60 for good : bad weather). We had figured out a good site just 100m off the hotel buzz on the upper part of the beach, just 30m away from the sea with free view to southeast. This was the direction where the shadow was predicted to come flying towards us. The beach runs rather accurately in east-west direction here. So we guessed that we had a pretty optimal site for observing the eclipse at elevation of 55 in this direction.

    The observing staff at this site consisted of my wife Sabine and my colleagues Andy, Michael + Christa, Peter H. aus N. :-) and Alex (Christina + Reinhard had gone off to find a different site). A group of guys from the Netherlands installed their equipment just next to us and we had some nice talks on what was going to happen. All other hotel guests set up themselves inside the hotel area or on the beach right in front of it (about 200m away). We set up the equipment around 10:30 local time, and I re-tested my camera and timer setups for a final time. Focusing turned out to be more tricky than I had thought before, because I had no point sources at the daytime sky, of course. Finally I made up my mind to use a ship far off the coast and/or the (point-like) light reflexes on the sea far out. I re-checked this with the details on the sun's surface. We were lucky to have some clear sunspots (even a small group) available this day.

    Exactly as calculated, at local time 12:38:20 (local time = UT+3h) the eclipse starts with the first contact. The moon starts to shift its dark disk in front of the solar disk from the lower right. We can hear lots of people clap and cheer somewhat further up the beach. The world-wide eclipse community seems to love parties anyway ! I am now shooting the first exposures and plan to keep on doing so regularily every 15 minutes (through the pentax equipped with the ND=5 filter foil). Actually it's good having a watch with alarm function. Still 1h 20m to go till totality. Some cirrus has appeared now at the sky, but it seems pretty small and localized and only in the west. Atmospheric turbulence seems to be OK, as we can see from the reasonably sharp visual images at our telescopes. Michael's Coronado image shows Hα details on the sun's photosphere pretty well, too. From using the Coronado we already can tell now, that we are going to see some prominences in totality, too. Although they seem pretty small. One group of sun spots also shows clear flares in its surroundings. Our photos already show that the lunar limb is not exactly round and smooth. Is this alread evidence for the mountains on the limb ? Several photos taken with some time in beetween show the same structure, so yes, it seems we are seeing mountains on the moon here (and this is not atmospheric turbulence or something artificial) ! This can be checked with this profile of the lunar limb .

    Some 40 minutes later, we are halfway gone, 50% of the sun is covered by the moon. We already notice a change in the character of the daylight. It seems dimmer (like at late afternoon), but it's not correspondingly reddish, rather a little bit more blue and with less colour saturation. If you calculate, you see that we've already lost 0.75mag (a factor of 2) in light now (if you neglect scattering from the sky + only calculate ratios of the areas covered). We can also feel a drop in temperature, already. The radiation field simply has faded (colleagues have measured a total drop of 7 Kelvin in the shadow, during the eclipse). Still, our eyes compensate for those effects by adaption and you have to consciously examine things to notice them.

    Another 20 minutes later, effects have become more outstanding now. Light has dropped by another factor of 2 and another 0.75mag are gone. Changes seems to accelerate notably now. We are also getting more nervous, feeling that totality is coming towards us. I'm re-checking the critical parts of my equipment. The time taken to cut the amout of light down by a factor of 2 is now getting shorter and shorter. This acceleration by itself already creates some kind of low-level panic. This gets real real massive when totality is only 1-2 minutes away. You feel like falling into a hole, a true collapse. People around us are now clapping and cheering louder and louder. We're definitely bound to drop down now... Looking to WSW we see it's getting threateningly dark. We can not see a clearly defined shadow approaching, but anyway my pulse frequency goes up considerably.

    The sky gets dark like during twilight after sunset and some stars start peaking out. Venus can be seen in the southwest. Just 30sec before totality I take off all filters from the binoculars and the telescope. Bailey beads are as big as the sun at first, but it's dimming down rapidly during the final 20sec. I'm now shooting the first 3 exposures through the Pentax with manual control (exposure times 1/250sec ... 1/800sec at ISO 200). Although you can still see a piece of the solar photosphere, the corona now is celarly visible...! At 13:54:55: BANG - we have 2nd contact, start of totality ! The sky very suddenly gets dark like 1h after sunset. The only thing remaining is the corona shining bright and the dark side of the moon in its center. Wow, it's crazy to watch this happening - it's still like a shock ! You feel like some huge guy far above is pointing his finger towards you...

    People on the beach run crazy like on new year's day (only those rockets and stuff are missing). I have no time to watch since I first need to run through my photographic schedule, shooting 3 exposures with 2sec spacings in between, controlled by the remote exposure controller. Then increase exposure time, check position in the camera viewer and off goes the next short series of exposures. This happens 4 times. In a hurry I now take the camera off the telescope and get the eyepiece in place for visual observing. 'Now, DO get rid of the camera', I think to myself - but instead I wonder and wonder if I should shoot another exposure with the 50mm standard lens... but finally I remember that I have enabled mirror locking and I would need to zap through the camera menues to switch off the mirror locking mode.... I finally manage to get rid of the camera, and store it in my flight case.

    The first glimpse on the corona through the binoculars is absolutely fantastic. The corona isn't round like 1999 but elongated and only axis-symmetric. It is coverered all over with radial hair-like stripes and details, and on top of this 4 or 5 long spikes are reaching out diagonally to large radii. In the pole regions the hair is pretty short. Below this bright detail there is also a non-structured round and diffuse distribution of light. At the upper edge of the sun I can now clearly see the prominence that we saw in the coronado narrow-band images before, but it's now much more saturated, luminous, bigger and with much more detail. The colour is a screaming mix of pink and orange. There are even more prominences to be seen nearby. I am just looking at the details of all this in the telescope when someone shouts '...watch out, only 30sec left to go!' It's incredible how the time flies by...

    It's been too short, simply much too short ! I'm angry about having spent so much time 'in vain' on photographs rather than looking and experiencing...

    My chronometer reminds me: watch out; the sun's gonna pop out any moment now. People on the beach are clapping and cheering once again and BANG, here comes the first beam scratching the lower lunar limb! Again we can see the corona shine, despite Bailey beads shining bright just next to it. The stars still can be seen.. Venus .. some others ... I simply forgot to look for mercury, Mars, Formalhaut. But now, I urgently need to get my filters back to protect my lenses and our eyes. It's getting brighter and brighter very very fast, and the beach people are still very excited, clapping, shouting... Venus remains to be easily seen for a considerable time - we almost have normal daytime light already. I again take off the filter from the Pentax trying to check out Venus, zooming in. We have a half venus today ! Christa's really astonished, 'hey, looks like moon ?!' Sure Christa, - Venus has got phases ! :-) I negotiate with Sabine to let me have her little Powershot A80 DigiCam to make some automated shots into the zoom eyepiece on the Pentax (just holding the cam behind the eyepiece and watching the TFT sceen). In fact, we can seen venus on these shots quite nicely. Great. Even 5 minutes after 3rd contact we easily find venus with the naked eye (you need to remember the position on the sky though). In the telescope we easily see it even 15 minutes later...

    With time, our excitement settles down slowly but steadily. All body functions back to normal - but real slowly ! All the stress (that started with second contact, and even before already) fades away, finally. It's incredible that everythings seem to be over already. And, coming back with some remorse to my camera, I am finally very glad of course: I've spent much time taking some pictures, but they turn out to be excellent when browsing through the files on the camera's built-in 2.5inch TFT. Especially the pictures taken of Bailey beads seem really wonderful on first sight. Yeah ! I quickly forget my bad wording towards my photo equipment (I felt really bad about time running out with ending totality).

    Everybody's relieved now, and people are checking their photos and videos. I'm staying busy with shooting some photos of the partial phase now with the Canon + 50mm lens through the Pentax with eyepiece projection - just for fun. Now I also can afford a little walk with taking pictures of all the people around. Everybody is still upset and checking and discussing their images. 'Yeah, that one's really great !' Andy crying out loud, because he has shot down his WebCam programs just at the wrong moment - aaarrrggh ! But still, he has got something, and he will get some nice pictures after stacking the video data... Peter H. has taken a video including sound, and you can hear all the excited people on it... A recording that reminds you really intensely of the atmosphere and the beach party during totality !

    We are spending the partial phase really relaxed. Taking some photos. Some detail look on the lunar limb, where you can see the mountains ! Finally, at 15:13:32 the moon detaches from the sun. A big final cheer and thank you from everybody around. We are all very happy, about our lucky weather, about the impressive observations and nice photos that we have taken. It also warms up now again. And, really thinking about it, we are finally not unhappy to have the sun back again. :-)

    In the afternoon everybody meets on the terrace for a coffee - a nice thing to compensate for the exhaustion during totality. We enjoy lots of cookies, as most people (unusually) did not have lunch today. We get known to some new friends and colleagues from all around the world, exchanging images and email addresses.

    It's been really really wonderful ! - the next eclipse, where and when did you say it'll happen ?

...and some pictures !

    Please click on the picture for a larger view !

    Partial phase 1, shortly after 1st contact

    Partial phase 2

    Partial phase 3

    Partial phase 4

    Bailey Beads 1

    Bailey Beads 2

    Bailey Beads 3

    Bailey Beads - details

    Totality starts, 2nd contact

    Composit image of the corona

    Totality on the beach with Venus in the southwest

    Venus after 3rd contact, photograph taken with a simple DigiCam through an eyepiece on the Pentax


Version: 24.04.2012
© 2007-2012 by P. Surma