Parabolic optics and advice on first telescope purchase

[ashenlight]

Fairly new to astronomy (doing it seriously anyway!) and after a couple of years using 10x50 bins, I'm looking to get a telescope in the next couple of months or so.

Haven't got a massive budget, but I'm almost decided on this one:

http://www.uk-telescopes.co.uk/sky_watcher_explorer_130p.htm

Would anyone be able to tell me the benefit of parabolic optics? And would you regard this telescope as a good all-rounder first telescope? I'd like to have good views of a wide range of things, the moon, saturn's rings, jupiter's bands and moons, DSOs etc.

Sure you guys answer loads of questions similar to this from newbies but your help would be greatly appreciated!

Thanks

[Doc]

A lot of beginners go for this scope. Extremely well made and with accurate tracking.

You will be able to see alot DSO's with this. They won't be magazine quality views of course but you will see grey smudges in the sky when looking at objects like M31, M81, M42 etc.

For the price you can't beat it.

[red dwalf]

hello mate,

fairly new to this myself having bought the same scope as you (the 130p) at xmas, used it as much as i could with weather being so awful, but i can tell you that the views of saturn are great, not massive views but you can see the rings and planet well, you can clearly make out the cresent on venus but venus very bright so i use a filter on this, moon is amazing, m42 the orion nebula is seen very well through this scope but alot depends on light polution around your area, i also think i made out the andromeda galaxy one night but was not 100% certain where i was in the sky but i could make out a smudge of light. as for the parabolic optics i think this is just a better made and coated mirror than you would normally get for your money but someone else will put you right on this i sure.

i am very pleased with mine as a first scope, easy setup. easy to transport and on good seeing nights i can be out there for hours.

p.s. keep looking out on this site for a second hand set of eyepieces and a good barlow, the ones you get with the scope aren`t bad but barlow is a cheep one.

[beamer3.6m]

Just to clarify even in bigger scopes you still only see grey smudges so this is not anything to do with the scope you have chosen.

It's a great scope by the way. Most started with one, including me.

[Doc]

Just to clarify even in bigger scopes you still only see grey smudges so this is not anything to do with the scope you have chosen.

It's a great scope by the way. Most started with one, including me.

Thanks for pointing this out. I forgot to mention this.

[red dwalf]

yea, bigger apperatures let in more light, not to be confused with making things bigger

[ashenlight]

Thanks for the replies and advice. I'm glad to hear the telescope is a good starter, with a modest budget I'm keen to get the best for the money.

I'm outside for hours with my bins even now so I think I just won't sleep once I get my scope..

What does the barlow lens actually do, improve the quality of the image, the magnification?

Can't wait to get started now! Looks like I will have to with the generous cloud cover out there tonight...

[Doc]

A x2 barlow will double the magnification so by putting it before a 10mm eyepiece the barlow makes it a 5mm eyepiece.

The same as a x3 barlow a 9mm eyepiece becomes a 3mm eyepiece.

[red dwalf]

yes a good 2x Barlow lens will increase the magnification of the view by changing the focal length of the eyepiece i.e. if you have a 10mm eyepiece and add a 2x barlow then the 10mm eyepiece will seem like a 5mm eyepiece therefore increasing the magnification, if i am making sense.

[Astro_Baby]

The Barlow doubles the magnification - technically it increases the focal length of the scope which has the effect of doubling up the magnification for any eyepiece connected to it.

Magnification is based on the focal length of the scope divided by the eyepiece size.

So for instance a scope with a focal length of 650 ( such as the Sky-Watcher 130 ) with a 10mm eyepiece will procduce a magnification of 650/10 = 65 - so x65 power.

A Barlow doubles this because with the Barlow in the focal length is x2 so you now get 1300/10 = 130 so x130 power

Hope that helps

By the way if your interested the difference between a parabolic and a speherical mirror is this.

A spherical has a cross section rather like taking a slice across a sphere at right angles - ie its cross section is an arc. A Parabolic mirror has a slice taken from a sphere at an angle so in cross section its a parabola.

In a long tube telescope a spherical mirror is fine but as the scope tube gets shorter spherical mirrors cause image problems - a condition called spherical aberration.

To correct this a parabolic mirror is needed.

Years ago parabolic mirrors were difficult and expensive to produce so had a very high price tag ruling them out for most amateur telescopes. In more recent years parabolic mirrors have been able to be machined and mass produced which has produced cheaper and better optics and enabled fast focal ratio scopes such as the 130 to be produced at much lower costs.

A fast scope is lighter ( cos it can be shorter ) and 'faster' ie it can collect more light for its size and 'see' better. Thats a really rough and ready explanation - theres also hyperbolic mirrors which I am not even going to try and explain .

And yes the 130 is a good scope - I had one to start with before I went mad and bought a bigger scope

[ashenlight]

Thankyou Doc, red dwalf and Astro_Baby, understand that alot better now. Thanks for the difference between parabolic and spherical too Astro_Baby, the results I got with a google search on that just didn't suffice.

What a great forum I've stumbled upon!

[Astro_Baby]

Have a look at wiki on speherical versus parabolic - its a better explanation than I could give.

[mdstuart]

I also had a 130mm (5.1) and it was great. Then I bought a 6 inch and then a 10 inch...You have been warned..

Mark

[Astro_Baby]

Absolutely true - I started with a 130PM before I knew what was happening I ended up with an 8" monster and an endless stream of upgrades.

Lulu was finding the same - telescopes and women are a fearful combination Mix a womans abaility to spend cash and grab 'bargains' coupled with a hobby that could empty the bank balance of an Onassis and you have s scary combination :D

[barkis]

Without getting too technical, the difference between a paraboloid, and a sphere, is the difference between a good objective, and a superb objective. Spherical mirrors of sufficient long focal length, can be polshed to a sphere, and will bring parallel light to a good focus.

As the focal length of a mirror gets shorter, the need to parabolise the surface on the mirror becomes essential. The degree of difficulty in acquiring the correct figure, increases as the mirror focal length shortens. Hence, faster, ie shorter f numbers, usually results in a more expensive telescope.

Ron.

[mojolomjl]

Bought a 130P at the beggining of January as my first scope and in its limited use because of CLOUDS I have been very pleased with it, especially looking at the moon.

[Terry]

Hi

I'm another who bought the 130 PM at Christmas and have to agree with everything that all the other post have to say. I've had great views of the Moon, Venus, Pleiades and look forward to when the skies clear so that I can get back out there.

[crepitis]

Absolutely true - I started with a 130PM before I knew what was happening I ended up with an 8" monster and an endless stream of upgrades.

Lulu was finding the same - telescopes and women are a fearful combination Mix a womans abaility to spend cash and grab 'bargains' coupled with a hobby that could empty the bank balance of an Onassis and you have s scary combination :)

Now, if only I could come up with a telescope with shoes attached.....hmmm