Looking at buying one of these Celestron telescopes...

[Purplehayze104]

its a good little find is that shop, they just specialise in Scopes & Bino's have a nice display of various types an sizes was good to get idea of sizes etc as was newby, only downside is have to order it then wait couple weeks for it to arrive, but that was me just being impatiant haha ! got my 150p/eq3-2pro from them very helpful staff to know there stuff.

[Tammie_M3ENF]

Hi everyone,

Don't worry I haven't gotten totally confused (yet, ha)... I have printed out various spec sheets on the scopes I'm looking at as well as a little price comparison.

Funnily enough today I bought an astronomy magazine (not sure if we're allowed to say names of magazines?) today from a local well-known supermarket and let my Dad read it and he immediately asked me about the Celestron SE series which of course is on my shortlist.

I am a beginner when it comes to astronomy although I do know the names of quite a few constellations and where they're located, I just never got any further than perhaps reading the odd magazine or watching a TV show on the subject. When the national newspapers mentioned a comet or meteor shower my Dad and I would usually pop outside to see if we could see it. I remember seeing Hale-Bopp out the bedroom window which was a pretty cool thing.

I'm grateful for all your suggestions and comments, thank you so much! I may ask more questions once I've narrowed down the list. I am so far rather partial to the SE range but then I like the look of the other two 5" ones I asked about. I do definitely want the GoTo feature though, from others comments it helps you learn which is always great.

[Chris]

Hello Tammie,

In terms of optics different scopes do different jobs:

Maksutov-Cassegrains optics such as the 4SE have a very long focal length (1350mm focal length) folded into a very compact tube. These types of scopes are best suited to brighter objects such as the Moon, planets, double stars, globular clusters such as M13, and some bright DSO's such as the ring Nebula M57. The reasons they are best suited to these bright objects are 1) a long focal length creates a lot of magnification thus a narrow field of view so planets and globs etc are well framed in the field of view. 2) focal length divided by aperture equals focal ratio thus 1350/102mm =13.2 = f/13.2. A focal ratio (f/) of 13.2 is very 'slow'. Slow focal ratio scopes give a relatively dim image so this is perhaps the main reason why they are best suited to planets, doubles, globs etc because these objects have a relatively bright apparent luminosity they appear relatively bright so the slow optics don't matter.

In summary the Pros of Mak-Cass optics are that they are highly portable, great for bright objects like planets, they don't need collimating so no tweaking mirrors or lenses so good for beginners, good for planetary imaging with a webcam. Cons are that there slow optics rule out alot of fainter deep sky objects, there is a lot of glass in the optics and the optics are sealed so cooling times are long (cooling optics is important to prevent air turbulance in the tube blurring the image), no good for DSO imaging due to both the focal lengh and ratio, and the narrow field of view can make objects harder to find even with goto sometimes.

A scope at the other end of the scale would be a Newtonian reflector. Using my 130mm Newt as an example, this has a focal length of just 650mm and a focal ratio of f/5 thus it gives a gneraous field of view and the image would be bright because the optics are 'fast' f/5 is pretty fast. These are ok on planets and brighter objects but you would need to use a barlow lens for very high mags, they have the best aperture per price, dim diffuse objects will fit in the field of view better and will appear brighter, the cool down is fast (open tube), the only con is that they need collimating, although this isn't as hard as it sounds but does require the purchase of a cillimation tool such as a cheshire collimator (20 quid ish).

I could go on but I'm aware that I've bombarded you with quite a bit all ready!

Any qustions just ask and good luck with your purches, you are doing the right thing asking questions

Chris

[M4lcs67]

Might be an idea to download a free programme called stellarium to your computer. It gives you a complete 360% view of the sky and everyone on SGL uses it. Also perhaps an idea to invest in a planisphere. A great device to use in the field. Just set the date and time and hold it up to the sky for an instant reference point.

[Chris]

Oh this might be handy as well, its a field of view calculator, just select a scope, swich to visual mode, then select a celestrial object:

http://www.12dstring.me.uk/fov.htm

Chris

[M4lcs67]

Yeah Chris,

Nice one. Forgot about that. I have it saved to my desktop.

[m37]

All I can usefully contribute is, if you want an AZ GOTO then I would choose Celestron over Skywatcher. I didn't! but there are a couple of useful features that Celestron has in the software that Skywatcher don't. EQ mode for one if you ever want to use a wedge, Skywatcher removed this and there is no way round it but Celestron has the option of AZ or EQ mode. Not a deal breaker but it would be there if you wanted it.

Celestron also have the Wifi option. The Nexstar 102SLT pretty much lines up with the Skywatcher Startravel 102T which I have. The focal lengths/ratios are different though.

I've also noticed that drivers are more readily supported for Celestron in various bits of software (ASCOM most noticeably).

[66mikeg]

Only problem with SW go to is the manual, once you find a sensible explanation it is fairly straightforward for visual use

[Pig]

Maybe you should buy one of each type

[Joves]

I started off with a 130 SLT and absolutely loved it. Have upgraded to a 10 inch Schmidt Cassegrain since, but still have the 130. Would never get rid of it. The optics are fantastic and the GOTO is an absolute breeze to use... and, more accurate than my 10 inch, I might add. I wouldn't hesitate in recommending anyone purchase one of these. For the money, I think they're probably the best GOTO scope you could hope for.

Best of luck with your purchase. I'm sure you'll love what you see through it, regardless of which one you choose!

[CSM]

I started off with a Skywatcher 130mm f 6.9 Newtonian, which worked well but finding objects was a problem. The extra aperture of my 150mm NexStar SE and focal length (f/10) does make a difference together with the GOTO facility which really is a great help. Ok - if you want to spend all your time hunting for objects that's fine as well. And as far as alignment is concerned the Celestron 1-star alignment can work very well if you do it by accurately centering the star with a reticule eyepiece. I used to do it by eye using a 10mm eyepiece and defocusing the star to get a larger circle, but this is nowhere near as accurate.