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First Light For TT2 (Turret Telescope 2)

Started by David Simons, 04/26/2004 01:42AM
Posted 04/26/2004 01:42AM Opening Post
I finally got enough pieces together to do a decent first light test of my version of the Turret Telescope at Stellafane.

Earlier post:

http://www.astromart.com/messages.asp?message_id=189733&page=

For comparison I also used a Tak 152 f8 refractor for a fairly reliable bench mark : ) I only did a quick star test, also Jupiter and the Moon. From what I could tell, the two big mirrors on the TT2 were taking their sweet time cooling down this eve. Slow undulating wavery views, with sometimes very fine detail on the moon and Jupiter. The star test was not really showing any rings, just a symmetric donut with a very small hole out of focus on either side. But the good news was no discernable astigmatism, as this was a concern since the main steering mirror is not exactly a "flat" but a >very< long focus spherical mirror. Sorry I'm not really a star test evaluator yet : )

Collimation was intuitive. A laser down the focuser tube was aligned to hit the center of the parabolic mirror and return into the focuser. With the big cutout in the side of the OTA it was clear what needed to be aligned. Cooling will be the next hurdle in this design !

My wife and three year old son wanted to see what Daddy was spending all afternoon doing : )

The Takahashi did not seem to have the same cooldown issues. The same level of detail was usually present most of the time in the Tak, but the really detailed views did not seem to pop into view very often, as the TT2 occasionally did. The Tak showed nice diffraction rings on either side of focus, with a slight amount of purple on one side of focus, and a good hard sn-a-p when it hit best focus with no extra color. Powers were ~60/48,169/135 and 250/228 for the TT2 and Tak respectively. Eyepieces: Vixen silvertop plossl, and Pentax ortho 9,6mm.

I suspect the views I had through the TT2 are similar to what premium dob owners are getting, but without the spider diffraction effects.

Comments welcome !

David Simons

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David Simons's attachment for post 15330

David Simons