Tuesday, September 09, 2008

Telescope/Lens for the next total solar eclipse

My Canon 200mm f2.8L was used with a Kenko 2x Teleplus, but as you can see from below:

the internal reflection is very bad. Another friend of mine was using another lens, and also another Kenko 2x Teleplus, and he got very similar internal reflection pattern as well. Therefore, I should not use this Kenko 2x for the next time.

My TG-SP II should probably limit me to stay around 400mm and I should not go anything much heavier. So right now I've three candidates in my mind:-

1. Canon 400mm f5.6L:- this is a proven lens, both for total solar eclipse, the diamond ring, as well as for deep sky imaging. However, my TG-SP II will not be able to support it for deep sky imaging, and thus, this lens will be less than useful for me.

2. Canon 100-400mm f4.5-f5.6L:- this is also a proven lens, but I've to ask my friend to see if it has any internal reflection for the diamond ring. It's a little bit heavier than the Canon 400mm f5.6L so the TG-SP II should still be able to carry it for short exposure like up to a few seconds. Deep sky imaging is not a real concern for me, again due to the TG-SP II and thus I don't have to worry about it's deep sky performance. It features a wide zoom range as well as the image stabilizing function and thus, it should be very versatile for day time imaging.

3. Borg 77ED II:- this is a very light weight telescope, between the weight of the above two lenses. It has 500mm focal length which is even more attractive for solar eclipse. Internal reflection is an unknown and I've to do some Google work to see if that's okay on this aspect. Deep sky imaging is out of question due to the TG-SP II again. What makes it attractive again is due to its versatility - it's a telescope so that it can be used for visual observation, however, this is too close to my existing Tele Vue Ranger. But then it will be a perfect match with a Lunt's Solar System 75mm H-alpha filter, if I ever go for one.

In conclusion, if the totality alone is concerned, (1) will be the best. If day time photography together with totality is concerned, (2) will be the best. If other than totality, visual observation and H-alpha possibilities are concerned, (3) will be the best.

To me, right now the Borg 77ED II is the lowest priority candidate, since I would want something bigger than my Tele Vue Ranger, let say the Borg 101ED. Of course, the 101ED will be too long, in terms of focal length, for the totality given my TG-SP II. So most likely I will go for a Canon 100-400mm f4.5-5.6L IS due the versatility.


From this shot:-


Canon 100-400mm f4.5-f5.6L does not even show internal reflection with a Canon 1.4x.

And this shot:-


also shows zero internal reflection, this is the Canon 100-400mm f4.5-f5.6L without any tele-converter.

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