What are the Differences...
Posted 11 November 2003 - 05:55 PM
Posted 11 November 2003 - 06:23 PM
The 120mm will gather much more light than the 80mm. 67% more light.
The f/ratio is the ratio between the objective diameter and the length of the light path through the tube. The ratio or f/ is found by dividing the focal length of the telescope by the aperture diameter of the objective.
Posted 11 November 2003 - 06:35 PM
Posted 11 November 2003 - 06:43 PM
From what I've read in the way of customer reviews (mostly here at CloudyNights), there's a lot more to compare these 2 scopes than just aperture. If I were you, I'd poke around here in CN's Refractor's Forum and Product Reviews. Other folks are much more qualified than I to compare the 2.
Posted 11 November 2003 - 07:05 PM
Posted 11 November 2003 - 07:21 PM
Posted 12 November 2003 - 01:16 AM
"Between the Orion 120ST EQ Refractor and the Orion 80mm ED Apochromatic Refractor? Quality...Viewing...Other. When they say 120mm and 80mm what does that mean exactly. Also could you give me a rundown on the f/?, how do I make sence of this?"
This is a great topic for dicussion! All the information here is excellent and very important. All things being equal, the aperture theoretically wins the game. I was talking to a member of the local astronomy club here who owns a gorgeous 14" SCT about the very sharp views through my humble 120mm refractor. He told me a smaller aperture won't pick up the amount of atmospheric turbulence a larger telescope will. Thanks to the useful advice from my friends, my scope is now perfectly collimated. *thank you for that* Aperture, while of significant importance, is only one major factor to look at when purchasing a new scope. For me, I finished most of the H-400's, all the Messier's, and the RASC Finest NGC's with my 10" reflector. I decided to go with a refractor because I love planetary work and recording what I see at the eyepiece especially. My site is quite light polluted. In my case, the refractor is a real performer and allows me to fulfil my observing objectives- where I am located. When I can afford it in the future, I'm thinking big aperture again (more deep sky objects), and longer focal ratios (planets, etc).
Those are my thoughts. Btw, I'm so glad about the collimation advice!