Which Telescope Is Better And Why?

Question

Hi,

I have been looking at telecopes for some while now.
I have now narrowed my choise down to two telecopes within my £250 budget.

They are both 6" Celestron reflectors, although one is a Dobsonian, and the other is a more regular one on an equatorial mount.

I would like to know which one would be best for me, if i were to probably use them at home, and move them around fairly often... I would look at the planets, star clusters, and nebulars.

Here are the two 'scopes:

Here is one:

http://www.telescopeplanet.co.uk/ViewProdDetails.asp?prod_code=PON05H000038

And this is the Dobsionan:

http://www.telescopeplanet.co.uk/ViewProdDetails.asp?prod_code=PON06G000027

Please say which is better, and why.

Thank You.

Oh, could you also state wheather Celestron Is a Good Quality Make??

Thanks.

Gene stated that the non Dobsonian it could track objects...

I guess he means that i would need to buy another tri-pod to do that??

Also, the focal ratio is f/5

What are the advantages and disadvantages of the smaller focal ratio?

And hopefully thelast additional detail, but do you really think I would be able to see the M51 galaxy like in the picture on the website?

Surley not...

Answer 1

For dim deep sky objects like M51 its generally better to get the biggest aperture you can afford, which means a Dobsonion mount. However, you are not going to see much if any color with your eyes, and frankly not much more than gray blobs under light polluted skies. I hope that does not turn you off to astronomy. If you are interested in deep sky objects consider the portability of the scope, and your ability to get out in the country side under dark skies, and with a decent scope you will see things that will leave you astounded and speechless.
The moon and planets are brighter objects, so you could get a smaller aperture scope with a motorized equatorial mount. Celestron, Meade, and Orion are all good brands
I looked around a bit, and found that Celestron makes a 10 inch Starhopper Dobonsion, and a 102 mm refractor with a go to mount, both of these scopes are under $500, which I believe is about 250 pounds, although with taxes and shipping would probably be a bit more.

Answer 2

Celestron is a good brand.

The one on the equatorial mount you will be able to do astrophotography with, if you eventually buy a drive for it.

The Dobsonian, you may be able to snap some quick shots but you won't be able to take like 30 minute exposures.

The focal ratios of a telescope can be found by dividing the focal length by the aperture of the primary mirror or lens. The equatorial mounted telescope is a f/5 and the Dobsonian is an f/8

Here's what the differences are.
The f/5 has a wider field of view when used with any given eyepiece. However, this means that it will also offer less magnification for any given eyepiece.
Magnification = (telescope focal length)/(eyepiece focal length)

The f/5 will require shorter exposure times for astrophotos but this is somewhat irrelevant being the f/8 is a Dobsonian. The f/5 will also be a little trickier to collimate than the f/8 and will have more edge distortion.

The f/8 will give you more of an advantage if you want to look at planets though, because it will be easier to reach a higher magnification. You will be able to use an eyepiece with a longer focal length which will be more comfortable to view through. Both telescopes have the same pratical magnification limit though. But again, the f/5 has a slight advantage for nebula and star clusters.

One focal ratio isn't really better than the other though. They both have advantages and disadvantages.

I think, personally, for the price, I'd just get the one on the equatorial mount because it does give me some versatility as far as astrophotography goes.

I did not see the photo of M51 but I can promise that you will not see that in either telescope, however, you may be able to get a photo that looks like that with the right astrophotography setup. The reason is, the camera can see more than the eye. In either of those telescopes, under dark skies very dark skies, ,super dark skies, you may be able to see some structure in M51, and a few other galaxies, but they'll look kind of fuzzy. Most other galaxies will look like little oval blurs.

If astrophotography isn't important, you may want to consider buying an 8" or 10" Dobsonian from www.telescopes.com

You will be able to see more, especially with the 10". The shipping to the UK will be about $141 though, which is 70 UK pounds.

Answer 3

It is a close call in my mind, but I would get the Dobsionan.

It has a longer focal length, which means it will be more tolerant of optical imperfections. Even the best telescopes have some small imperfections in the shape of their lenses and mirrors.

While an equatorial mount can track the sky if properly aligned, the one you are considering has no motor. You will have to turn the RA knob by hand to track the sky. I am not sure that is really worth the trouble. If it had a motor drive, that would be different. Also, aligning a portable equatorial mount every time you set it up can be a lot of trouble.

Answer 4

The one that is not a Dobsonian will be batter at higher magnifications because it can track objects as they sweep across the sky. The drawback is that you'll need to buy a tripod for it which will raise the cost.

More: The non-Dob has the mount but not the tripod. Celestron makes good scopes. I have had a C-8 for a long time and am pleased with it.

Answer 5

Celestron is the Cadillac (..or for you Brits I guess it would be Jaguar..) of telescopes. Top quality systems..!

Get the Celestron on an equatorial mount. They're a bit more time-consuming to align and set up properly, but you won't need to be constantly moving the 'scope tube to stay aligned with whatever you're observing as you would have to do with the Dobsonian.

Answer 6

Go for it and build your own type of reflector. Plus it's fun and you learn all about optics and what is really necessary for a decent telescope and what is not. And the size limit is up to you! There are many good books and websites. Just google up "How to make your own telescope".

The book Build Your Own Telescope: Complete Plans for Five High-quality Telescopes That Anyone Can Build
by Richard Berry is a good one.