TEC 140 and TeleVue NP101

Started by garybhooper, 10/29/2006 04:06AM
Posted 10/29/2006 04:06AM Opening Post
The last few nights I have been doing a side by side comparison of
double stars with a TeleVue NP 101 and my new TEC 140. A couple
of examples are 36 Andromeda and Delta Cygnus. 36 Andromeda, @ 1.0 sec, mag 6.1/6.8 is cleanly split with the TEC, but it is a figure eight in the TeleVue. The companion of Delta Cygnus @ 2.5 sec, mag 2.9/6.3 is a grey dot on the difraction ring in the TeleVue, and
appears to be about twice as far away from the primary in the TEC. I
seem to prefere the view through the TeleVue, even though the TEC
has better resolution. The TeleVue has a textbook diffraction pattern,
with a sharply defined central disk with a faint ring. With the TEC, I
don't see the sharply defined disc, and I have not seen a good
difraction ring yet. The smaller aperature with the larger difraction
image is more estheticaly pleasing to my eye. These results don't make me disapointed with the TEC, it just illustrates to me that a 4 inch APO is a great choice for a scope. I am waiting to see what the TEC will do with the planets, I expect it to show more detail than the TeleVue.



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Posted 10/29/2006 06:52AM #1
Comparing a three element 5" F/7 scope against a four element 4" F/5.4 scope...Interesting. Wouldn't it have been a more fair comparison if you added the TEC 140 Prime Focus Field Flattener and possibly stepped the TEC-140 down to 4".
Posted 10/29/2006 07:21AM #2
beautiful scopes.. what kind of magnification were you using ?

Izar was beautiful in my 4" TMB, it was also very beautiful in my later larger refractors but the view in the 4" for sure had its own thing going.

Mike

Posted 10/31/2006 05:55PM #3
The airy disc in a larger scope will be smaller than one with less aperture, which is why larger scopes can resolve better. Also, lack of rings (or very faint, thin ones) is the sign of an excellent optic: more energy is concentrated in the airy disc.
But I know what you mean, aesthetically speaking. The larger airy discs and thicker rings thru my Brandon 94mm (vs. the Tak) were very pleasing to look at.

Steve O.