Quick thoughts on refractors vs reflectors

[emadmoussa]

Nothing scientific here, only personal thoughts.

On Saturday night I set up all my three telescopes side by side for a quick comparison. Not that I like using more  than one telescope at a time, I just wanted to see in what way a refractor beats a reflector and vise versa.

Scopes used: 6" corrected achromatic refractor , 102mm ED refractor and GSO 10" Dobsonian.

Generally speaking - I could easily imagine a refractor scoring high against a reflector if they were the same aperture. However, a 10" refractor will be a complete monstrosity in size and weight and of course unless you have a very high mount pointing at the zenith requires a degree of contortionist skills.

Having said that, I noticed that even smaller aperture refractors - although being less capable of collecting as much light as the 10" GSO Dob - produced stunning views of star clusters with a 3D effect. The same targets were also impressive in the reflector. I'm honestly torn now...while I love the rounded 3D stars of a refractor I still found that the spiky twinkly stars in the Dob quite appealing.

The 10" dob produced impressive views of globular clusters. While it showed a lot more details than the fracs due to bigger aperture, it fell short on star colours and to some degree contrast.

Open clusters were  very nice in both telescope types. I was surprised to see that both 10" reflector and 6" frac showed similar amount of nebulosity in M45. There was a hint of that in the 102mm ED as well. Again, the fracs produced slightly brighter stars. Slight difference that you'll notice only if you compare the views side by side.

Open clusters in my opinion are a frac specialty. They're just more appealing in my eyes. While the 10" reflector could delve deeper it lost against both refractors on these clusters. It's probably a matter of subjective preference here. So I stand corrected. And yes, doubles, binaries and variables....well..refractors performed slightly better.

When it comes to galaxies and nebulae you have to give the 10" Dob all the credit given it's aperture. It's very true aperture is king. The Dob showed me very faint galaxies that I've never been able to see in either refractors. I dare to say that even though I had a 11 inch Schmidt Cassegrain, the marginally smaller aperture GSO Dob produced brighter and in some cases more detailed views of a number of deep sky objects - including the little Andromeda satellite galaxies. I don't want to compare reflectors to SCTs here, but it's worth noting that in my experience there's more to say about the resolving power of a reflector as apposed to a Schmidt Cassegrain.

Since I spend most of my observing time hunting galaxies and nebulae, it seems the Dob will be a very good deep sky companion.

There are just light-hearted observations...I'm just saying.

Thanks!

[Moonshane]

I cannot really argue with much of what you say. A good summary. There's little doubt that different objects 'react' in different ways to different scopes and some peoples' eyes appreciate diferent scopes for different reasons. I personally choose based on a number of reasons other than optics too. For me, aperture always matters. Vive la difference!

[emadmoussa]

I cannot really argue with much of what you say. A good summary. There's little doubt that different objects 'react' in different ways to different scopes and some peoples' eyes appreciate diferent scopes for different reasons. I personally choose based on a number of reasons other than optics too. For me, aperture always matters. Vive la difference!

You're absolutely right. There's a fair amount of subjectivity involved.

[Dude_with_the_tube]

very interesting post and i am looking forward to test the same very soon as i have finally managed to get my hands on a fantastic 90mm  F14.4 refractor

I love dobs and for DSO`s there is nothing what can beat them and i agree with Shane here,aperture is the king and always will be,but i always fancied that long focal length refractor for planetary,doubles etc and also for nights when Moon is at full blaze and makes DSO observing obsolete.And as i am interested to observe everything i possibly can,then in my opinions both Dobsonians and Refractors just complete each other and not compete against.

[Moonshane]

agreed 'Dude'. As I suggested above, I find comfort at the eyepiece and ease of set up as important as most things when it comes to scopes. also I really don't get on with the right left reversing of fracs for some reason. I do though have four very different scopes, all newts, and for very different targets.

[emadmoussa]

I have to agree re the eyepiece position in a Dob, Shane. Part of the reason I found it difficult getting along with reflectors before was the position of the eyepiece once mounted on EQ5. Dobsonian mounts on the other hand are very intuitive and quite comfortable.

[emadmoussa]

very interesting post and i am looking forward to test the same very soon as i have finally managed to get my hands on a fantastic 90mm  F14.4 refractor

I love dobs and for DSO`s there is nothing what can beat them and i agree with Shane here,aperture is the king and always will be,but i always fancied that long focal length refractor for planetary,doubles etc and also for nights when Moon is at full blaze and makes DSO observing obsolete.And as i am interested to observe everything i possibly can,then in my opinions both Dobsonians and Refractors just complete each other and not compete against.

That's what I was thinking. They do actually complete each other. Now I know for sure which telescope I'm using for which targets. If I'm observing doubles and binaries or even star clusters I'll go for a refractor. Otherwise I'm going Dob

[Dude_with_the_tube]

That's what I was thinking. They do actually complete each other. Now I know for sure which telescope I'm using for which targets. If I'm observing doubles and binaries or even star clusters I'll go for a refractor. Otherwise I'm going Dob

sounds like a prefect plan to me too

[sbooder]

I have to agree re the eyepiece position in a Dob, Shane. Part of the reason I found it difficult getting along with reflectors before was the position of the eyepiece once mounted on EQ5. Dobsonian mounts on the other hand are very intuitive and quite comfortable.

I have the rotation mod on my EQ mounted 10" it is just a length of cable conduit with a heating duct large jubilee clip holding it to the scope in front of the first tube ring, this means I can rotate the tube for best EP position.

But good post on the comparison.  I have not really got on with fracs not sure why, I just love Newts.

[TractionMan]

Very interesting comparison. Thanks for posting this. I guess there's no such thing as "The One and only Telescope".

[John]

Interesting post indeed 

On some nights and on some targets my 4.7" ED refractor gets pretty close to the views that my 12" dob produces. On other targets though the dob is streets ahead. 

I've not really got my 6" F/12 refractor fully up and running yet but it will be interesting to see what that brings to the party 

My little 4" ED refractor has it's place too as it's so portable and the only scope I have that can show me 3.8 true degrees of sky. 

Variety is the spice of life as far as scopes go !

[Kropster]

Did you use the same eyepiece in each scope?

Eyepieces make a big difference, so that would affect the views.

Also the f ratio will make a difference to the blackness of the background and give different subjective views.

To get a good comparison you really need a similar refractor and reflector in both focal length and aperture otherwise you will not really be comparing refractors against reflectors.

But interesting comparisons none the less.

[peterjtmorris]

You are right of course, but I would like to put in a good word for refractors and also maks. The huge advantage of refractors and maks is that they do not need collimation and are very robust. I have dropped fracs and maks and they survived with no trouble, would hate to think what would happen with a reflector. Furthermore they are easy to handle and are light compared with bigger dobs, which makes them much easier to get out. I also note that refractors and maks are good for planetary observation, clusters (refractors rather than maks), globular clusters, planetary nebulae and above all double stars. What all these DSOs have in common is that you can observe them in light-polluted areas, like my back garden . Hence I would say that refractors and maks are the ideal scopes for suburban backyards. For a big dob you need a dark sky area. Which brings up another advantage with fracts and maks, they are easier to use with go-to systems which I also regard as essential in light-polluted areas as you cannot see much below mag 3 with the naked eye or mag 6 in the finder. And I would like to speak up for maks, I think they are fantastic scopes and unfairly overlooked, if only for their contrast and sharpness, and they are much cheaper than apos which they are equal to in optical terms IMHO. They are no good for imaging of course, but I am a purely visual observer.

[John]

I've found refractors do need some collimation but once set they hold it securely for a long time needing no further adjustment. "out of the box" though a number of the refractors I have owned did need collimation adjustment.

[forasibi]

Now I've acquired my 102mm Apo, I plan, just as you have, to set both up ( my 9.25 SCT) and compare for myself.  I have to profess, though, a bias for refractors - it's the sheer simplicity of looking straight away at the object.  It seems, I don't know, more honest.  But this is an emotional response, not analytical.  I'm reminded of a poem by Walt Whitman "WHEN I HEARD THE LEARN'D ASTRONOMER ".

[emadmoussa]

Did you use the same eyepiece in each scope?

Eyepieces make a big difference, so that would affect the views.

Also the f ratio will make a difference to the blackness of the background and give different subjective views.

To get a good comparison you really need a similar refractor and reflector in both focal length and aperture otherwise you will not really be comparing refractors against reflectors.

But interesting comparisons none the less.

Yes - I used the eyepieces interchangeably. Well, you don't need to compare refractors and reflectors of the same focal length simply because you decide the quality of views and depth regardless of aperture. And of course it's not possible getting your hands on a 250mm refractor...can you imagine the size and cost of this one it wasn't a comparison per se but rather trying to have a feel of where either telescopes excel. 

[emadmoussa]

Now I've acquired my 102mm Apo, I plan, just as you have, to set both up ( my 9.25 SCT) and compare for myself.  I have to profess, though, a bias for refractors - it's the sheer simplicity of looking straight away at the object.  It seems, I don't know, more honest.  But this is an emotional response, not analytical.  I'm reminded of a poem by Walt Whitman "WHEN I HEARD THE LEARN'D ASTRONOMER ".

Yep - me too. I've got a soft spot for refractors...I dare to say refractor biased. But I had to give credit to reflectors where credit was due. I think your 9.25 SCT will be very nice on galaxies and nebulae, but  it will  probably fall short against your 102mm as far as wide field of view and brightness were concerned.

[sbooder]

I was always under assumption ( probably a mistaken assumption) that in general Newts were better for Deep Sky and Fracs better for the solar system objects?  Probably wrong as I say but for some reason it has always been in my head.

[emadmoussa]

I've found refractors do need some collimation but once set they hold it securely for a long time needing no further adjustment. "out of the box" though a number of the refractors I have owned did need collimation adjustment.

When I received my 102ED few months back I was shocked to discover that the 2" to 1.25" adatper was shattered probably due to reckless couriers. Fearing that it might've  knocked the scope completely out of collimation I gave it a quick day light test and it was fine...later that night I used it the for few hours and it was perfectly OK. I agree there are occasions where refractors require tweaks and collimation (which I have never done and no idea how to do it), but in general they're very robust instruments

[Mike73]

If I only observed from home with moderate LP then I'd go for a good frac just because open clusters look so good with them but from a dark site I'd go for a reflector every time, in dark skies aperture is king.

[Kirscovitch]

Nice report.

[Kropster]

I was always under assumption ( probably a mistaken assumption) that in general Newts were better for Deep Sky and Fracs better for the solar system objects?  Probably wrong as I say but for some reason it has always been in my head.

Reflectors generally have a larger aperture and smaller f ratio so are better for fainter objects.

Solar System objects are generally brighter and smaller and within the grasp of smaller aperture refractors where the higher f ratio gives larger magnification.

[Tonys]

I'm really enjoying this discussion and agree about the importance of subjectivity. For example I find that I need more light these days to read small print, even with my glasses, and I wonder how much scope aperture this equates to. I remember once seeing a sketch of Saturn drawn by a young observer using a 70mm frac and thinking I'd be happy most nights to see that much detail with 200mm. Then again, most nights the seeing doesn't allow my big scope to give anything like it's best detail wise and for me that's what makes those all too brief moments during a session when the atmosphere really settles down so special.

[sbooder]

Reflectors generally have a larger aperture and smaller f ratio so are better for fainter objects.

Solar System objects are generally brighter and smaller and within the grasp of smaller aperture refractors where the higher f ratio gives larger magnification.

I was silly about 4 years ago I sold my Orion UK 8" f8 Hilux coated Newt to help pay for the 10" on the NEQ6.  I should have waited just a little longer and I would have had both one for DSOs and the other for Solar System.  It was such a lovely scope too!  Cracking on planets.

[astro mick]

I think as Patrick used to say both scopes do very different things.

I don't think you can beat a good Refractor,for such things as Double Stars,The Moon,and the Planets.Refractors give lovey clean crisp images,and mosly do not require any collimation.

If your interest lies in Deep Space,ie, Star clusters,Nebulae,Galaxies,then Reflectors win hands down.But of course they require collimation,and a bit more maintenance.

So I think both scopes score well in their own field.

Mick.