|
Hi Shaun,
What are you interested in ?
If you want wide field, the 8" will have a better field of view.
If you want something you can move, the 8" will weigh less and fit in the car much more easily.
If you want galaxies and faint stuff, the 12" will deliver more galaxies.
If you want planets, the 12" will have a better resolution and will handle higher magnification.
Now... how much better ?
One stellar magnitude in brightness is about 2.5 times more light. So an 8" dob will have about 50 square inches of surface area (ignoring central obstruction).
A 12" Dob will have about 113 square inches of surface area. That's about 2.26 times light collecting area - which translates to about 1 magnitude.
So you should be able to see stuff that is 1 magnitude dimmer in the 12" than what you can see in the 8".
If that sounds like a minimal amount of improvement for a fair bit of cost ... well it is not a huge increase. But it might be the difference between seeing something and not seeing it.
In terms of resolution, well the 12" will resolve smaller features, if the seeing permits. Most of the time the seeing will be your limit, not the scope's optics. So that may not translate to a great improvement except on those odd nights when things are All Good In The Heavens.
My feeling is that the 12" dobs are the sweet spot in terms of price to aperture, and weight to aperture, right now.
But the improvement is what I would call incremental rather than revolutionary.
Hope this helps.
Regards,
Tony Barry
WSAAG
|