Goto Telescope for Beginner

[Luke]

What a lovely place to observe from!

Yes, The 4, 5, 6 etc. usually refers to the diameter of the mirror in inches. I have a lovely C6, a superb six inch SCT from Celestron.

To compare the "light gathering power" (i.e. how bright the faint stuff is in the scope) between two scopes, you compare the square of their diameters.

So, 25 (5x5) vs. 36 (6x6), which means that the six inch scope has about 44% more light gathering power than the five inch.

I find about 35% upwards to be an obvious difference visually, so for me 44% more light gathering power is definitely worth considering.

I would find a five inch a little bit on the small side as a general purpose observing scope and would look at six inches upwards (under dark skies) or eight inches upwards (under okay skies) if funds allow. If it was for bright objects like planets, double stars or bright open clusters, then the aperture is not as important (though can still help to show more detail if the seeing is good).

[ollypenrice]

There's a lot of reference to the 127 Mak here but it wouldn't be my choice. The long focal length limits the wide field possibilities and these make for some of the nicest and most relaxed visual obserivng sessions. Focal lengths around 500 to 700mm have lots to offer, especially when learning the sky. Also the database in the small GoTo scopes includes gazillions of objects the optics have no hope of revealing.

What small scopes do best is give widefield views so it seems a shame to miss out on them. Yes, the Mak will be super crisp on the planets but other scopes can match that, notably reflectors with more aperture.

These things are personal but I'd spend the cash on the bits you look through.

At high powers decking will bounce...

Olly

[Dizeee]

There's a lot of reference to the 127 Mak here but it wouldn't be my choice. The long focal length limits the wide field possibilities and these make for some of the nicest and most relaxed visual obserivng sessions. Focal lengths around 500 to 700mm have lots to offer, especially when learning the sky. Also the database in the small GoTo scopes includes gazillions of objects the optics have no hope of revealing.

What small scopes do best is give widefield views so it seems a shame to miss out on them. Yes, the Mak will be super crisp on the planets but other scopes can match that, notably reflectors with more aperture.

These things are personal but I'd spend the cash on the bits you look through.

At high powers decking will bounce...

Olly

Looks like it may be the grass after all then.

Its amazing at the different points of view I am getting, never knew there was so much difference between lens size and refractor / reflector etc.

Going to need to understand a lot more before making a decision me thinks. Surely if something is able to produce great images of deep space, it would find the solar system a piece of cake - but not neccessarily so?

[ollypenrice]

Looks like it may be the grass after all then.

Its amazing at the different points of view I am getting, never knew there was so much difference between lens size and refractor / reflector etc.

Going to need to understand a lot more before making a decision me thinks. Surely if something is able to produce great images of deep space, it would find the solar system a piece of cake - but not neccessarily so?

Oh, you know the saying, 'Two of a trade never agree...'

The optical requirements of deep space and the solar system are very different. The solar system objects are small and bright. They therefore don't need huge aperture but they do need fine resolution and high contrast. They also need a long effective focal length - ie the combined FL of eyepiece and scope.

Deep space objects are often large and faint so you need aperture to pull in enough light, you need a wide field of view to fit eveything in (so a shorter effective focal length, AKA lower magnification) and, while fine resolution is nice to have, it is less crtitcal than on the planets.

So a Maksutov is optimized for solar system viewing. That doesn't mean it can't do DS but on the deep sky, pound for pound, the Newtonian outguns it.

Don't worry, though, these are all good telescopes and will provide profound satisfaction. No one telescope can do everything.

When running sessions with beginners one of my standard points is to stress that telescopes are usually thought of as being there to make small things look big. But in astronomy they are also there to make faint things look bright. I point to a spot in the handle of the Plough and say, 'RIght there is a face-on spiral galaxy the size of the full moon. The problem isn't that it's small but that it's faint...'

Olly

[brucen]

I expect you will find the decking is ok for general viewing as you tend to be standing - or sitting - still when you are doing it. As Olly said it is at higher power that it is really noticeable and particularly with a webcam. If your grass is anything like mine at the moment it will be so soft that it will be hard to get the mount to stay level anyway.

[Davestate]

What a lovely place to observe from!

Yes, The 4, 5, 6 etc. usually refers to the diameter of the mirror in inches. I have a lovely C6, a superb six inch SCT from Celestron.

Hi Luke,

I'm looking at possibly buying a C6-SGT XLT and have a question - I assume the auto movement can be overridden to operate manually?

Regards,

Dave.

[Dizeee]

Oh, you know the saying, 'Two of a trade never agree...'

The optical requirements of deep space and the solar system are very different. The solar system objects are small and bright. They therefore don't need huge aperture but they do need fine resolution and high contrast. They also need a long effective focal length - ie the combined FL of eyepiece and scope.

Deep space objects are often large and faint so you need aperture to pull in enough light, you need a wide field of view to fit eveything in (so a shorter effective focal length, AKA lower magnification) and, while fine resolution is nice to have, it is less crtitcal than on the planets.

So a Maksutov is optimized for solar system viewing. That doesn't mean it can't do DS but on the deep sky, pound for pound, the Newtonian outguns it.

Don't worry, though, these are all good telescopes and will provide profound satisfaction. No one telescope can do everything.

When running sessions with beginners one of my standard points is to stress that telescopes are usually thought of as being there to make small things look big. But in astronomy they are also there to make faint things look bright. I point to a spot in the handle of the Plough and say, 'RIght there is a face-on spiral galaxy the size of the full moon. The problem isn't that it's small but that it's faint...'

Olly

Great post, thanks for taking the time to type, makes a lot of sense. I think I would easily prefer to sacrifice little sharpness in the solar system planets(so long as I am able to see them) in preference for enhanced clarity / brightness with some deep space imagery. Thats what really excites me most. Can you see andromeda with telescopes like the ones we are talking about? That's the sort of thing Im after. How would a schmidt cassegrain suit my needs? 5 or 6 inch?

[Dizeee]

I expect you will find the decking is ok for general viewing as you tend to be standing - or sitting - still when you are doing it. As Olly said it is at higher power that it is really noticeable and particularly with a webcam. If your grass is anything like mine at the moment it will be so soft that it will be hard to get the mount to stay level anyway.

Oh yes, very soft now I wouldnt dream of it. I am planning more for when it gets drier. Where I am is a water meadow anyway so wouldn't consider anything until Spring at least.

[Luke]

Hi Luke,

I'm looking at possibly buying a C6-SGT XLT and have a question - I assume the auto movement can be overridden to operate manually?

Regards,

Dave.

Hi Dave,

By operate manually, do you mean e.g. operating it with all the electrics off and moving it by hand? If so, I don't think it would work very well, you'd have to undo the clutches and tighten them up again every time you want to move it I believe, which would be quite awkward and a pain. Things soon start moving out of view, so you would forever be undoing and redoing the clutches. I'm not sure you would be able to look through the eyepiece while fiddling with the clutches. Or did you mean something else?

[stevetynant]

Great post, thanks for taking the time to type, makes a lot of sense. I think I would easily prefer to sacrifice little sharpness in the solar system planets(so long as I am able to see them) in preference for enhanced clarity / brightness with some deep space imagery. Thats what really excites me most. Can you see andromeda with telescopes like the ones we are talking about? That's the sort of thing Im after. How would a schmidt cassegrain suit my needs? 5 or 6 inch?

You can see the Andromeda galaxy with a normal pair of bins - from dark skies with good seeing you can apparantly see it naked eye if you know where your looking.

[PeterW]

Guildford and Farnham have astro societies. Guildford regularly hold observing at newlands corner and Albury Heath. The online group astronomy4everyone use Albury too. Go look thru stuff, see what things look like and then decide. I'd get as big a scope as is practical and that you can use/afford. With the right finder scope and a good atlas like the downloadable TriAtlas finding stuff is as hard as map reading.... Takes a bit of practice but is not too hard. The size if the scope then determines if you'll see anything down the eyepiece. Goto can be like GPS, it can take you to the wrong place too. If you want to do imaging then I'd worry more about tracking and goto.

How clear and bright is the Milky Way from your garden?

All the best

PEterW

[Luke]

For looking at faint objects like galaxies, the most important aspect of a telescope is its aperture, hence the popular saying:

- Aperture is king

If you want to look at galaxies, it is a real dilemma with your budget whether to go for the very nice benefit of goto if you are keen on the idea of goto, or to go for aperture.

The goto will take you to the galaxies, but many of them will be barely visible in 5 or 6 inch scopes, they will be too faint. The Andromeda galaxy, M31, can be seen with the naked eye, as pointed out. I can catch it naked eye with indirect vision at home under my okay skies (looking slightly to the side of it - strangely, you can see fainter stuff if you don't look directly at it - this also applies when looking through the telescope).

As Olly points out with a lovely example, large telescopes like dobs aren't really about magnifying things even more, they are about collecting more light to make the faint stuff brighter. My 5 inch refractor can effectively magnify just as much as my 16 inch dobsonian, because under UK skies, you can't really magnify much past 300x and still get a reasonably sharp view, and a 5 inch refractor can reach 300x with no problem.

Anything faint benefits from extra aperture, from galaxies to supernova remnants to spectacular globular clusters.

However, there is the other very important saying, which makes buying telescopes or recommending them very tricky:

- The best telescope is the telescope you use the most.

If you found you hated moving a telescope manually and trying to find things for yourself, then large aperture with no goto is not really going to help. Or if you had to lug a large telescope down a flight of stairs as part of your setup process, that isn't going to encourage you to get out and use it once the initial buzz wears off, so a more compact design like an SCT, or a refractor, might make sense. If you wanted to do long-exposure deep sky photos, a dob is the wrong type of scope - the goto and tracking versions do not track accurately enough.

All of the scopes by the good makers are very good at certain things and I think scopes are a little bit like a set of golf clubs. You can't play a superb round of golf using one club. Imagine trying to putt using the driver.

If you use a telescope for what it's best at, be that wide low power views, high power planetary, or a giant dob for looking at the faint DSO's, then they are a real joy to use. Where it gets frustrating is when trying to use a scope for things that it's not so good at.

re: Andromeda, no matter how big your telescope, it will not look anything like the amazing photos in books and on magazine colours. If possible I would recommend you look through a few scopes before buying one.

Good luck with the purchase. I've been into the hobby for about four years and it's always difficult to figure out what to buy!

[PeterW]

Or get a small low f-ratio scope with goto and a "video" camera. Short exposures can show a lot more than the eye, though not works of art. The SGL and cloudynights forums have subsections on the right camera and how to do it.

Good luck

Peter

[Dizeee]

Thanks again, SCT> Schmidt Cassonian Scope? That was one that was recommended.

Photo / video hasnt even crossed my mind re all this, viewing is the key. The more I read and the more I go outside with my rubbish bins looking at my Stellarium I downloaded, the more confident I feel that I would be albe to find things / enjoy trying to find things.

[Dizeee]

Sorry , Cassegrain - dunno why I typed Cassonian!

[Leebert]

Thanks again, SCT> Schmidt Cassonian Scope? That was one that was recommended.

Photo / video hasnt even crossed my mind re all this, viewing is the key. The more I read and the more I go outside with my rubbish bins looking at my Stellarium I downloaded, the more confident I feel that I would be albe to find things / enjoy trying to find things.

Reading the above, and other posts it looks like a 6, 8, or maybe 10" dobsonian would be a good start. Completely manual so not suitable for photography really and you have to find your target but with good light gathering for faint objects (the larger the better but this will increase the weight). The link below is for an 8" Skywatcher version as an example...

http://www.firstligh...-dobsonian.html and a recent mini review here:

However, as has been said a few times previously, get along to a meeting and look through other peoples scopes. It's probably the best way to see if you get on with the different types of scope before spending your money. Also, whilst you are waiting to find out which one is the right one for you, continue to learn the night sky with your binoculars as it'll help loads when you get a scope

[toilandtrouble123]

the celestron 127slt was what i asked for as my first (didn't get it-got a 90mm refactor instead). its a great little piece, might be able to get a few decent planetary pics with a webcam and effort.