4"ED vs 6" f/8 Newton

Hi!

Guess this thread must have been up a million times....
Still here I go: Which scope do you think would performe best for planets, binaries and globular clusters, a Synta 4" ED or a 6" f/8 Newton ?
The cost for the OTA:s are just about the same.
I already have EQ mount.

The scopes I have are S-W 4,7" f/5 refractor and a C80ED.

Hope anyone can help me with advice....

/Magnus

>>Still here I go: Which scope do you think would performe best for planets, binaries and globular clusters, a Synta 4" ED or a 6" f/8 Newton ?
The cost for the OTA:s are just about the same.
----

In the US, I believe Synta 4 inch ED is around $900, a 6 inch F/8 Newtonian is around $200.

jon

An optically perfect and collimated 6" Newton telescope is going to show more details on the planets than a 4" APO refractor according the laws of physics. But there is a big caveat with the Newton and that is the time it takes to cool down to near ambient temperature. If you use a fan and are willing to wait an half an hour until the heat turbulence layer above the mirror disappears I recommend the Newton. The optical path in a Newton is going twice through the tube and thus is twice as much affected by air density irregularities than the refractor.

Personally I would choose a high quality 10" f/5 Newton for planetary studies because I can not afford 5" to 8" APO refractors and I'm willing to wait for the cool down time. Also you get more resolution, light and contrast than the 6" Newton.

Google for Thierry Legault. He has some good informative pages about high resolution. Especially read his page about obstruction.

Roger Persson
(8" f/6 and 20" f/5 dobson)