Orion 80 ED f/7.5 or Orion 120 ST f/5?

[Vince]

Hi guys,

Okay, I already own a Celestron C90 Mak (1st Gen 1000mm f/11)for 8 years now and I'm thinking of going for a shorter focal length (but faster) refractor.

Optically, based on a review I read, the 80ED does have better resolving power but practically, I feel that a 600mm f/5 would be faster and hence more sutiable for deep sky.

Does any of you guys own one or the other? How do you think they will compare to the C90 Mak?

[weixing]

Hi,

Optically, based on a review I read, the 80ED does have better resolving power but practically, I feel that a 600mm f/5 would be faster and hence more sutiable for deep sky.

The 120mm F5 Achromatic Refractor will be a good choice if you only use it for DSO and wide field... that's mean you don't use it for planet, Moon and double stars.

Anyway, base on review ( http://www.cloudynights.com/item.php?item_id=1691 ), it don't work well if magnification is over 120x.

Have a nice day.

[Vince]

Thanks for the prompt reply!

I guessed as much that the 120mm would be better off. It's now going for under 1K at Astra SSC. Guess with the CG-3 GEQ Mount that I already have, it'll be a good improvement for shots of M42 and M31 then.

[weixing]

Hi,

I guessed as much that the 120mm would be better off. It's now going for under 1K at Astra SSC. Guess with the CG-3 GEQ Mount that I already have, it'll be a good improvement for shots of M42 and M31 then.

If you are getting only the OTA and intend to shot some Astrophoto with it, then may be you can also consider the 150mm F5 Newtonian. It'll be better than 120mm F5 Achromatic Refractor and more suitable for Astrophotography... but you need to do collimation which ,IMHO, not difficult.

Have a nice day.

[Meng Lee]

My opinion is:

1) If you are doing photography, then get ED 80 and you will have much nicer pics.

2) If you are viewing (big) DSOs , then get ST 120.

3) If you are getting something for both, then consider something else. Maybe my R135 newtonian.