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Its really more about location, location, location. A 4" frac will show more under a truly dark sky than an 8" refelector will when its in light polluted skies. So the nub of this is the biggest controlling factor is the sky and that means location.

Unless your lucky enough to live in a dark sky site to really get the best you need to travel and that brings in the maximum aperture you can transport and set up.

A 4" scope you will use will always see more than a 10" scope that never makes it out of the house because its too much of a chore to lug it about.

Think about how you feel when you get home from work, do you feel tired ? I know ai do and the thought of having to drag a 10" scope down the stairs and load i into a car, drive it to a site, set it up, tear it back down and repack it was enough that my 10" got used a grand total of errrrrrrrrf once !! It was sold off in favour of my 8" scope.

Bear in mind as well that almost all deep sky objects are faint and fuzzy in almost any scope, yes a really big scope like a 16" will make a difference but the difference between say an 8" and a 12" wont be that big, the target will still look faint and fuzzy.

A really big scope under pristine skies will of course do a lt better and up in the 16" size there ally is an advantage but you have to decide whether a) you can afford it and even more critically B) can you lug it about with you and c) can you store it.

Bear in mind also that most larger refelectors, in order to keep the size down, have faster F ratios which makes eyepiece performance an issue with the consequence that you will find it harder to get good EPs on a budget and will have to spend more.

There are a lot of factors in choosing a telescope and the aperture argument, in my opnion, is grossly overstated. I may have been true years ago when there was little in the way of fast scopes, less light pollution, simpler eyepieces etc but ai feel its too simplistic a dictum these days.

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Ye canna change the Laws of Physics Jim - The greater the aperture of a telescope, the better (smaller) its resolution.

So yes, all other things being discounted (irrelevant(?) things like its mass), aperture IS King !!

Edited by cantharis

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i think astro-baby has given a fair few important points to consider - and yes it's fair to say for DSO a 6" to 8" telescope over a 4 will give you more smudges to look at, for the most part.

andrew

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In a word - No! Aperture is all well and good but if it's not mounted conveniently for your requirements or has poor optical quality you'll be put off as soon as you start. Plus, it depends on what you want to do with it. Focal ratio is also important, particularly if you want to get into AP.

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The mount! Don't skimp on the mount! No matter how big your aperture is, if you are wobbling around everywhere you just won't see a thing!

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Yes, its well said that the mount is a critical bit as well. A solid mount is worth an inch of aperture at least.

Thes nothing so sad as a wibbly wobbly telescope and it makes viewing a misery.

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Yes, its well said that the mount is a critical bit as well. A solid mount is worth an inch of aperture at least.

Thes nothing so sad as a wibbly wobbly telescope and it makes viewing a misery.

Hear hear - I had a 10" dob on an apalling plywood mount. Whilst the views were terrific, they were useless when they were pinging back and forth wildly as I tried to keep them in the centre of the FOV!

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I agree re the mount. Built Dobsonian mount for my 6" and while it saves my back much pain, it does wobble s bit and detracts from the experience . On a similar vein, my Meade LB mount squeaked awfully and drove me demented until I polished the alt bearing and now all is good with the world again. I suppose what I'm saying is that the system must work as a unit

Barry

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when the OP asked the question I must confess I assumed they were talking about the scope not the mount. clearly you need a mount capable of handling whatever you want to mount on it. badly made dob mounts are, well, badly made. but a well built dob mount is more robust and less wobbly than anything else especially with apertures of 6" or more, or long focal lengths. dobs are the best mounts for visual in my experience, they are just not designed for imaging.

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I'm probably just repeating what has already been said here. If you are stuck under the same sky whatever scope you buy then the bigger the better (assumiing you can move in and out of the house if needs be). If a smaller scope means you can travel from light pollution to dark skies then the smaller scope wins. Of course the reality will be some where inbetween. A 10" dob is ideal for me, about as big as I would want to cart around. Of course if I had a garden observatory and the money then I would have 25" obsession, but would still want something smaller form star parties.

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when the OP asked the question I must confess I assumed they were talking about the scope not the mount. clearly you need a mount capable of handling whatever you want to mount on it. badly made dob mounts are, well, badly made. but a well built dob mount is more robust and less wobbly than anything else especially with apertures of 6" or more, or long focal lengths. dobs are the best mounts for visual in my experience, they are just not designed for imaging.

You've obviously never used a rotted plywood one :p !

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Hii,

Just wanting to say, sometimes it seems aperture is everything, Using Vixen ed80 Doublet and a Williams Zstar ed80 ddg, sharp as they come..looking trough a bigger opening from friends in a normal achromat seems sometimes aperture is everything...seems...with the problem i dont want to go bigger.

I discoverd a ED with 102 minimal or 120 maximum is awesome to use as long its around f6/7 max. Wonderfull i just now discovered to upgrade what was missing.

Thank you for youre post, helped myself a lot it seems also..

May u find the right choices in that.

S.J.

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I'd agree with that, my f6.5 106mm EDT is a lovely scope, though I tempted at some point to venture up to 120 or 130mm mainly just to get a little more resolution on planets.

Stu

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I'd agree with that, my f6.5 106mm EDT is a lovely scope, though I tempted at some point to venture up to 120 or 130mm mainly just to get a little more resolution on planets.

Stu

Stu,

As i hear from lots it starts at 120 ED and can stay at 120 ED..then again where is the line for more without ending with a huge reflector, Transportability is still my main point to be able to handle, yet seems the line in that is till drawn further. My next one wil be a 120ED..i should come real close to the perfect thing. let me know if one time u come to any new setups or conclusions in that.

Greets,

S.J.

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Thanks S.J.

I'd be very interested to look through a 120ED to see how the colour correction compares with a triplet. In an ideal world I'd find a 130mm ED triplet at a not too exorbitant price.

Will keep you posted.

Stu

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I have an ED120. It's the best scope I've owned in my years in the hobby :grin:

It shows slight colour around the brightest stars. On the Moon and Jupiter there is a little colour either side of focus but I can't see any at sharp focus.

I've owned a few 6" refractors and things start to get very large and clumbersome at that aperture. The ED120 is a pretty portable package for it's performance - I've used mine on an AZ-4 mount for short sessions.

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HI

BEEN LOOKING TO GET MY FIRST SCOPE AND THINK IV DECIDED ( 6 SE ) BUT ALSO QUITE FANCY A REFRACTOR , IV READ LOADS OF REVIEWS ON SCOPES LATELY AND THE CHOICE IS BEWILDERING .

I WAS READING ONE THAT WAS MATCHING 6 INCH SCT's TO 4 INCH REFRACTORS IN IMAGE QUALITY FOR DSO's ,DO THEY COMPARE IN ANY WAY AS I UNDERSTAND APERTURE IS EVERYTHING ANY HELP WOULD BE GREAT AS IM LIKE A YOUNG SPANIEL ON HOT COALS AND CARNT WAIT MUCH LONGER :)))

Well, what can i say...mak, reflector, Ed, achro, cassegr....as u said it..its either have one and be happy with it or try many, i already have a Mak 90/1250 Vixen Ed80 En Williams Zstar ED80 II..also etx 80. in 2 days comes a 120 achro...u see,, sort of lost also here till i find the right one..my idea? 120/500 ED would be awesome, still managable for transport ...it wil be interesting to folow youre experience in the Scope world. Best of luck and fun.

S.J.

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I know it's been said before, and might sound trite, but the best 'scope for you will be the one you use most.

If you can get down to a local club and have a look at some different 'scopes first it might help you decide, if you can wait that long!

Cheers

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The best scope is the one you use! So going too big and making the setup too difficult is going to reduce its usage. Aperture for visual will increase brightness of the object, but also the brightness of the sky, so a dark sky is good. A dark sky will also make the object stand out more, even with a small scope.

Even with a 10" scope I was unable to see any colour in the Orion nebula in a moderate LP sky and this is the brightest nebula. Everything else was a feint grey whisp, mostly very feint.

The 6SE is basically a compact reflector (light path folded), so good if you need compactness, but you'll pay extra for the priveledge. At the other end A 6" refractor would be huge and heavy and without ED/APO optics, may have halos around bright objects, unless it's got a long focal length, in which case it would be even bigger!

So if aperture is the priority, choose between reflector or SCT/Mac. If a reflector is too big and you can afford an SCT/Mac, then get one of those for compactness, whilst maintaining aperture.

Then there's the mount.....!

I found that an exposure of just a few seconds with a camera would reveal far more than I could see with a 10" scope, eg. colour in Orion with a single 5s shot, so I've stuck to AP. Not that I'm suggesting trying the 'dark side' of course.

Edited by sgazer
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Out of interest, very big Dobs tend to be cheap second hand. Our 20 inch, no beauty parade winner but nice to use and with fair to middlin' optics, was £1400 about nine years ago. Not many people will consider them.

At least one other member has a giant Dob bought cheaply like this. Ours is like beer. Good if you're thirsty. Our top end apochromatic refractor is like champagne. Sip, don't swill, and quench your thirst first. :grin:

Olly

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Out of interest, very big Dobs tend to be cheap second hand. Our 20 inch, no beauty parade winner but nice to use and with fair to middlin' optics, was £1400 about nine years ago. Not many people will consider them.

At least one other member has a giant Dob bought cheaply like this. Ours is like beer. Good if you're thirsty. Our top end apochromatic refractor is like champagne. Sip, don't swill, and quench your thirst first. :grin:

Olly

Post of the year :cool:

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