Primer - Choosing a Telescope

[Rob]

Choosing a Telescope

1: Avoid buying a low cost "beginners", or "starter" type telescopes from high street stores / tv shopping channels. You will almost certainly be disappointed and discouraged. Most of these inexpensive telescopes have poor optics, with flimsy mounts that will be of no use and provide you with shaky images.

A good start telescope range such as the Skywatcher / Celestron will give the amateur astronomer a great start in the hobby. As with binoculars, the most important factor is the light gathering power of the telescope, this of course depends on the lens / mirror diameter, known as aperture. The bigger the aperture, the more light is gathered by the telescope.

2: When buying a telescope, you need to consider portability.

A 16" Dobsonian or (light bucket as some may say) might be appealing if you're interested in deep space observing, but not if you live in a flat on the 4th floor!!. Carrying around a telescope of that weight 80 kilos (176 lbs) which could be around 67 inches long, can be daunting + put you off the hobby in one easy step! (oh yes, it can also put your back out!). So match your ambitions to your main observing site. Its easy to get aperture fever!. Don't overdo size, weight, or price. Choose a telescope you can carry and set up by yourself, just in case a family member or friend can't or won't go with you.

3: What kind of telescope?

Many telescopes are capable, with varying degrees of success of showing you virtually everything in the night sky. But no one telescope does it all perfectly. This is the hardest part of telescope selection. Every telescope excels in particular areas, and others where it's only adequate. Refractors, for example, are usually better at high power lunar and planetary observing than they are at finding faint fuzzy nebulae and galaxies. Reflectors are the reverse.

4: What magnification should you use?

Any telescope can magnify to any extent, however, the highest useful power of a telescope under ideal seeing conditions is only 50 to 60 times per inch (25mm) of aperture. Under average seeing conditions, atmospheric turbulence limits the highest useful magnification to 25 to 30 times per inch (25mm) of aperture.

So, how much power do you really need? High magnifications are OK when viewing the solar system, as there is plenty of light available, although you don't always need to use high magnification as there is plenty of lunar and planetary detail to see at 50 to 100 times.

Except for resolving close binary stars and globular clusters, very high magnifications are not usually needed outside the solar system either as stars always look like points of light, no matter what the magnification. Many planetary nebulae, like the Ring, Nebula, M57, look great at 100 times, but are too dim to see well if you increase the magnification. The Andromeda Galaxy is over 3° across, or six times the diameter of the moon. You don't need high magnification to see something that big!

Clear Skies

Rob

Source: R.M. Clarke. The salopain web - edited by R Hughes. 2005

[ukbigd]

Very useful infomation Rob....... I wished that I had read this before buying my telescope...... lol

[Staypuft]

Very helpful - many thanks!

[astropete]

a very good and helpful report.

[EntropyStar]

Thanks, i'm undergoing the trauma that is picking a first scope!

[Smood]

Choosing a Telescope

The Andromeda Galaxy is over 3° across, or six times the diameter of the moon.

What? Is that true?

Or am i being thick and totally getting that wrong..

Its that big?

[Ags]

M31 is big, but it has a small bright core surrounded by a much fainter extended disk.

[Vali x]

good info buddy

[earth titan]

A dob is a newtonian scope on a 'dobsonian' mount. Named after the inventor / populariser - Mr. Dobson.

[Moonshane]

Great suggestions and advice Rob.

I'd also add that considering the used market in this sort of friendly forum environment will save money and allow you to safely avoid buying a duffer.

This will also mean that you have a little money to set aside for the inevitable sundries you'll also want like e.g. a Telrad/Red dot finder, perhaps a star map book, an observing seat etc. (note that I don't mention eyepieces as these should be left until you know what sort of observing you prefer and what focal lengths, eye relief, field of view etc suit you and your scope). It also opens your mind the possibility of selling/swapping your gear should you feel like you have made an error or just want a change. The accessories and eyepieces etc will stay with you for the next scope so the price to change is often not too bad once you have the basic kit.

Edited August 30, 2011 by Moonshane

[Nimon]

Excellent thread. Was just linked to it.

[saturn4me]

I agree.An excellent article and very informative:icon_salut:

[heathenwoods]

Very useful food for thought. Ta!

[ADR]

Excellent info, particularly about not needing huge magnification. Thanks.

[wesley]

Thanks Rob very useful information but i have a silly question, i am looking to buy a all round telescopeas i am interested in both planetry and deep space, im also interested in astro photography so im looking for a telescope that will allow me to do both if possible but i believe i have narrowed it down to one of two choices Both being sky-watcher. The choices are 1. Sky-Watcher Skymax-180 PRO

2. Explorer 200p. Which one would you go for and why. Im leaning more towards the Sky-Watcher Skymax-180 PRO because it has a longer focal length, smaller in size i would appreciate yours and any body elses view on this matter.

Many thanks

Wesley

[Ags]

Wesley, if you mean photography of deep space objects, then the skymax 180 is completely unsuitable. The 180 is very slow (F15) so exposures would take a very long time. For example a 1 minute exposure in a 200 PDS scope would take 9 minutes in the skymax 180. Also the long focal length of the skymax would make tracking DSOs for such long exposures almost impossible.

[Cindy]

Total newbie trying to decide which first scope to buy: 6" or 8" Dobsonian. Difference in weight: 6.6 pounds. More aperture, right? Am I plunging too fast too soon? Would also need extras like 10mm Plossl, moon filter,....

[ScopeDog]

Hi Cindy,

I'm pretty new to the forum myself, but I reckon you'll get a lot more responses if you post your question in the main Beginners Help and Advice forum. I'll be happy to give you my opinion on the 8" SW Dob, which has been a great first scope for me.

[Adwonas]

I'm glad I read this post cheers

[clking61]

wish i would have read this before purchasing the powerseeker scope...allthough i have enjoyed it so far....

[SionStar]

Thanks I wish I had read this before I brought one from a high street shop, which I took back. However I'm considering this one

First Light Optics - Skywatcher Explorer 130

It will be my first telescope.

[LukeSuppalot]

Hi SionStar

Being a newbie myself I understand exactly where you're coming from. From what i've been told the sw130p is a very good telescope. I would suggest e-mailing First Light Optics and tell them what you want to look at and or photograph and your approx budget and they will advise you as best they can. I found them very helpful.

Hope this helps.

[SimpSmooth]

Help me please. I am fairly new to astronomy and want to buy my first 'proper' telescope. I have got a budget of around £250 - £300. What sort of thing should i be looking for? reflector or refractor? goto or not? I have been looking on the net for days but always end up getting confused. Should i buy something brand new? Could i look for something second hand that might be better? I really dont know what to do..... I didnt think choosing my first scope would be this hard!!! Any help would be a massive help.

Thanks in advance,

p.s. I would like to do some astro-photography...

Edited January 30, 2012 by SimpSmooth

[binzo62]

Great article, thanks for the info ... Stu

[4 moons]

hi , just got a SW 200p few weeks ago and feel i made the right choice, this forum is great , it has helped me alot members very helpfull, had to join, happy gazing to all