WAITING FOR THE SHADOW

SOLAR AND LUNAR ECLIPSE OBSERVING

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TSE2009 Shanghai region
I purchased a 70mm f6.2 APO refractor from William Optics. It is very solidly built with a very good quality solid 360 degree rotatable focuser.  It also weighs 1kg less than my ED80 and sits more rigidly on the LEQ thanks to it's shorter tube.

I made more modifications to the LEQ.  I added some light weight metal struts to the single arm fork to damp some vibration I was getting and I milled a whole lot of surplus metal out of the head that was not contributing to the strength of the head.  I built a new smooth friction clutch for the worm drive. 

Photo : The LEQ with the William Optic OTA.  A mirror flip box sits between the camera and the OTA. It has a 16mm Konig eyepiece with a 65 degree apparent field.  On this instrument this yields a field of view of 2.5 degrees at 25 power. 

The whole mount including tripod and step motor control box weighs in at 4.5kgs (10lbs). Many observers now use a solid photographic tripod with an Astrotrac tracking arm.  While the astrotrac on it's own weighs less, by the time you add a solid tripod and two tripod heads or ball & sockets, one to set the equatorial elevation the other to acts as a declination adjustment, I have seen whole set ups weighing 2 kg more than mine. My setup is a neat two axis mounting that weighs about 4.5kgs (10lbs) for everything but the payload. I have modified the stepper motor cables so that they cannot tear out as they did in 2008.  The equatorial angle isn't adjustable.  I always have a fair idea of my observing latitude for a given eclipse.  I make a wedge out of wood before each eclipse for the observing location.  It's strong and light. This was a deliberate design decision. Adjustable altitude wedges tend to need solid metal and would add a lot of weight to the kit.  I find this works very well.









Unfortunately we were clouded out for this eclipse so I didn't get to try out the new optics.  I had to wait until the 2010 total eclipse to see how the system worked.  You can see more pictures of my scope and another tangent arm tracker I built for my friend Bengt Alfredsson in the report about our failed trip. I discuss equipment quite a bit in this report.
http://joe-cali.com/eclipses/PAST/TSE2009/

Some readers may also be interested in the photo which illustrates how I have set up the back end of my 70mm refractor.  I added a flip mirror box to flip between an eyepiece and DSLR camera. This allows me to quickly swap between visual and photographic observation. In this photo, a 20mm cross hair eyepiece is in place.  I use this to do a quick drift check of the polar alignment.  During the eclipse, I replace it with a 16mm Koenig eyepiece 65 degree apparent field of view yielding a 25x70mm with a 2.5 degree true field of view. The DSLR has a right angle viewer on its finder that is pointing straight at the camera.

I have a 1/10 wave 50% beam splitter plate and at some point in the future I will replace the  flip mirror with a beam splitter allowing simultaneous viewing and photography during totality. Because of the 50% (1 stop) light loss resulting from the beam split, my f6.2 will become an f8.8 - still fast enough for eclipse photography.

I have an article on this website about constructing a solar filter mounting optimized for total eclipse observing.
http://joe-cali.com/eclipses/EQUIPMENT/solarfilters.html
I've tried different variations of this filter setup over numerous eclipses and now I think I've finally got a really effective solution for total eclipse observing.

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