What can I see with a 10'' reflector that I can't see with a 4.5'' one? Can I see galaxies' shapes? Nebulas?

Question

Why doesn't my question apper in the Astronomy & Space list?

Answer 1

A 10" aperture has almost five times the area of a 4.5".  This will let you see much fainter, and therefore many more objects than a 4.5" telescope.  Some of the bigger, brighter nebulae will start to look pretty impressive with a scope of this size, like the Orion nebula.  Galactic structure is still a bit beyond a scope of this size, you will be able to tell the shapes, but not see much in the way of spiral arms etc, to get this kind of detail you would need to go up to about 15" or bigger.

Magnification will be better with a bigger scope too, but sky conditions will be a bigger factor too.  A larger aperture will be more affected by less than ideal seeing conditions, at higher magnifications especially.  The bigger scopes, sometimes referred to as "light buckets" are best for low power wide angle viewing of things like galaxies and nebulae.

Answer 2

Really faint things.  I have a 10" reflector, and last summer, was able to see Pluto.  It was about magnitude 14.  The manufacturer claims it's good to magnitude 15 - and i'm starting to believe it.  But the 4.5" scope should have a fifth of the light collecting area, which amounts to about 2 magnitudes - limiting you to about magnitude 13.  This is still very good.

A smaller scope is usually much easier to set up for photography.  And with time exposures, you can see anything in a small scope.  So, the 4.5" scope might be able to reach magnitude 19 or so with a time exposure.  Your eye integrates light over a short time, perhaps a tenth of a second or so.

The limiting factor for me is light pollution.  A 4.5" scope at a dark sky site can see all sorts of galaxies that my 10" scope can't see in from my back yard.  Still, there are a couple messier objects that were a challenge for me even at a dark sky site.  I might have had to have waited until they were higher in the sky.

My 10" scope has an advantage for nebulae.  With an Oxygen 3 filter, i can see most nebula from my front yard.  It blocks most of the light, and only allows light in a narrow band, which turns out to be emitted by most nebulae.  The Oxygen 3 band turns out to be in the green/blue part of the spectrum - and your eye is quite sensitive there.  There are other filters, but this is the best.  Anyway, one summer, i was looking at the Eagle Nebula - m16, which is low in the South for me, at best.  From my driveway, low in the South is a grocery store parking lot.  So directly between two flood lights, i saw m16.  It was as good as i'd remembered it from any dark sky site.  The high pressure sodium flood lights do not emit in the Oxygen 3 wavelength, allowing the background to be black.  Contrast is everything.

But nothing like that works for galaxies.

Check out your local astronomy club.  My club's dues are $30 a year.  My 10 in Orion xt10i (with pushto object locator computer) was about $800.  I can borrow club scopes all i want.  And $800 would get me 26 years of membership. Then you can actually look through a telescope to see if you like it.  I have an eyepiece that i hate, but most people like.  You're own eyes are part of the telescope optics.  And they aren't the same as anyone else's.

edit: I see you actually have the 4.5".  So you know that a store's claim of 576x power is nonsense.  The 10" has better resolving power than that 4.5".  This is noticeable on objects like M13 - the great cluster in Hercules.  But in addition to size, your collimation makes a big difference.  I spent something like forever getting my optics aligned right when i first got my scope.  The scope's view of M13 totally knocked the socks off of everyone.  But the club has a very well kept 22" Dob.  Well, you can't have everything.  My 10" sets up in 3 minutes.

Another edit:  I totally disagree that refractors have anything on a well collimated reflector.  It is true that refractors don't have to be aligned all the time.  What refractors are good for, is compact short focal length telescopes for astrophotography.  I've seen very good work done with an 80mm APO refractor.  It's not cheap though - it's more than twice what my 254mm reflector cost.  And that doesn't count the mount.  Sky & Telescope ran an article on this, and i know i've read it online, but i can't seem to locate it.

Answer 3

It is worth the expense if you want to see faint objects more clearly. I have an 11 inch SCT. With it, I can see - among other things:

1. Clear galaxy shapes for things like M51, M81 / M82, M65 / M66, M104 (dust lane very clear), etc.

2. Excellent detail in nebulae like M42, M8, M17, M27, etc.

3. Resolution of stars to the core of clusters like M13, M15, M11, etc.

I personally never get tired of targets like these, which I find to be stunning and beautiful.

Of course, to see these things - and hundreds of others - clearly, you will need clear, dark skies and patience. I think it's worth it. If you get a good scope and take good care of it, you will not regret the purchase. Clear Skies!

ADDED: My experience is that high magnification is not a real benefit for most observing. Most of my observing is done from 80X to 130X - even the Moon and planets. You should be able to see all of the planets with the 4.5, so a 10 inch won't help much there, unless you want to see Pluto. It will make the planets appear a little clearer and brighter, but the real benefit will show up when you are looking at deep space objects. Good Luck!

Answer 4

lots: galaxsees, nebulae, star clusters, double stars.

what exactly are you asking?

later: if you're asking about magnification you're so far off track that you need to completely rethink this. visit some local astronomers, have a look through their scopes, and make up your own mind.