Which one?

Hi,

After some good advice from albertw on boards.ie I've revised my shopping goals. I'm a beginner to this and after albertw's advice and several sites' I've decided against a GoTo as my first scope. I want to learn my way around the sky and point and click is not going to help me with that.

So now my decision lies between a refractor or reflector. I popped into AI's shop today to have a look at the scopes on offer and (based on my budget) the two there that looked decent were the C6-N and the C4-R. I've already found both of these €350 cheaper on Greenwich including shipping to Ireland.

So now I'm looking for the advice. Should I go for one of these or can anyone recommend a better brand with a similar pricetag? As for reflector -vs- refractor I know there are pros and cons with both. I'm interested in both planetary and deep-sky viewing but can't afford two scopes . The reflector has a 150mm aperture and the refractor a 102mm one but F/10 is better than F/5 right? (ok - no flaming - I know the tradeoff :lol: ) The reflector seems to be a better all-rounder but the refractor has better image quality (based on Dave Lillis' comparisons). On top of that my brother has a Refractor so we could probably swap over on occasion or go viewing together for the best of both worlds

So - let the games begin between the mirror-fans and the lens-fans :lol:. I'm already leaning towards the refractor but I'd be very interested in hearing of other brands - I'm not tied to Celestron but they're the only brand I know anything about.

TIA,

Steve

Steve,
Firstly, welcome to the IFAS website. I hope you find your time here enjoyable!

The best "value" scopes are dobs. "Value" as in the largest aperture for the cheapest price. If you're starting off, keep the focal ratio fast, ie about f5 is fine. The slower the telescope (i.e f8, f10 etc), the smaller the portion of the sky you'll see. As it's your first scope, a wider field of view will make it easier to operate which is important as you try and get used to a telescope.

An 8" reflector and a 6" refractor capture a similar amount of light. However, a 6" refractor is a much bigger instrument. Also, refractors vary in optical quality significantly. Ever wonder why some 3-4" refractors cost several thousand?...it's to do with the quality of their image. To buy a 6" refractor that will produce the same quality image as an 8" reflector, it'll cost significantly more, especially when talking about observing the moon and planets.

Don't get me wrong, refractors do have their place. Lidl have sold some nice refractors for very reasonable prices. However they are around the 70mm size. If you want something bigger but don't want to break the bank, it'd be very hard the beat a dob.

For a first scope, I personally would advise to go for a reflector on a dob mount rather than an equatorial mount. I know some people here will disagree with me, but from my own experience, I would recommend a dob mount, especially as a first scope and if it's in the 8" aperture range or larger. Something like these perhaps?? www.pulsar-optical.co.uk/catalog/index.php?cPath=21_45_46

However, THE single most important advice we can all give you is to meet up with astronomers at club meetings or observing sessions and get to try out all the different telescope designs. Then you can make a much more informed decision. There's a wide selection of telescopes to choose out there and they suit different people's tastes. The only way you'll figure out yours is to try a few scopes for yourself and make your own mind up.

Steve,

My advice drop the refractor idea. Euro for Euro/pound for pound a reflector will give you better bang for buck hands down every time. My advice to you is to buy the biggest reflector your budget allows. Remember the C4-R is still a 4 inch scope the C6N has over twice the light gathering power.

It is untrue to say that F/10 is better than F/5, or in fact F anything is better than another. It depends on what you are interested in. F/10 will give you higher magnification but a narrower field of view. F/5 will have lower magnification but wider views so the lower F/ratios are better for deep sky stuff (generally) and the high F/ratio for planetary stuff.

Now heres the cruncher. In order to give perfect views refractors generally need to be of a very high optical specification called (apochromatic) otherwise different colours come to a focus at different points and you see halos around bright objects like the moon. Apochromatic refractors are very expensive. Reflectors dont suffer from this 'chromatic aberration. They are cheaper to make therefore you get a bigger scope for your money. In the end thats what really matters.

Good luck.

Hi Steve and welcome,
You seem to have done some homework on the subject

You mention that your brother has a refractor, can you tell us what size is it?
The thing you need to keep in mind here is "expectation".
Only receintly, I met a person who was seriously underwhelmed by a telescope they got.
If you can, go to your nearest club and try get a view through a scope which is similar to the choices you're thinking about.
Most of them wont charge you for it.

The refractor would be easier to use (no collimation) but the reflector is bigger so the images would be brighter, then again its central mirror does block some light. Given a 4 inch refractor versus a 6 inch reflector, I'd be more inclinded to go for the refractor, as long as it doesnt have serious colour issues (achromatic abberation), some are better then others. Its only when reflectors get bigger do they enter a league of their own.

I know I'm going to get shot for this, but I think a 6 inch reflector is real borderline, I used one many years ago, I now use a 102mm F5 refractor and the refractors images are better.

If you want bright deepsky (galaxies, fainter nebulae and clusters) then get a Dob like Michael says, they give you the biggest bang for your euro.
Since Dobs usually have medium/big apertures, they can show decent planetary images also.
My next scope is going to be a Dob.

Hi Marcos,

Glad to see you are getting some helpful advice from the folks here. Welcome to the site!

Cheers,
~Al

Rather that three separate replies I thougt it might be better to combine them...

Steve,
The best "value" scopes are dobs. "Value" as in the largest aperture for the cheapest price. For a first scope, I personally would advise to go for a reflector on a dob mount rather than an equatorial mount.

However, THE single most important advice we can all give you is to meet up with astronomers at club meetings

I kinda ruled out dobs cos they look damn ugly :lol:. Seriously - I want one that will stay fairly steady and from the ones I saw that means a tripod mount.

I'd like to get to a club meeting. I might try and get down to Tullamore next weekend. I've been advised that the Phoenix Park meetings are basically just an ad for Celestron and if I get to a club meeting then I want one that'll cover all angles. Anyone know any clubs near me? (I'm looking at voyager here cos we live in the same town ).

Remember the C4-R is still a 4 inch scope the C6N has over twice the light gathering power.

It is untrue to say that F/10 is better than F/5

Reflectors dont suffer from this 'chromatic aberration

Twice the light? really? I missed that class :oops:

I know that F/x has a tradeoff between view/mag. But I'd like nice clear views of the planets but also be able to look at deep space - is that possible with the 6" reflector I mentioned?

Reflectors do suffer from spherical aberrations thought right? Again a trade-off. Or am I talking s**te?

You seem to have done some homework on the subject

Most of it on your site :lol:

You mention that your brother has a refractor, can you tell us what size is it?

It's a NexStar 130GT. tbh he hasn't used a lot himself at all (something to do with a new baby being born and all that - don't understand the problem myself - my twins are 18 months now and I still get out once every two months :shock: )

I now use a 102mm F5 refractor and the refractors images are better.

It's only 500mm long? Didn't know that refractors came that length. The one I mentioned is 102mm F10.

get a Dob like Michael says, they give you the biggest bang for your euro.
Since Dobs usually have medium/big apertures, they can show decent planetary images also

Yeah but the look awkward. How easy are they to use - the equatorial mount looks so much easier to follow an object with for a complete beginner. After deciding not to get a GoTo I still want it to be easy

Thanks for the advice guys - I knew there was never going to be a definitive answer - for every option there's an opinion . I'm happy to get the opinions but I do know that the final mistake is my own to make

Steve