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Refractor VS Reflector

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#26 Iwi

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Posted 11 May 2006 - 12:27 PM

I agree on the quality issue:
- the average 8" refractor is a work of art, either a f/15 achro or f/7 apo or the like, made by some small company reknowned for it's high quality refractors
- the average 10" reflector is from china, made by a benchpress reknowned for it's low operating cost

I'm waiting for the day that newtons have quartz primaries, true dielectric secondary's, and a fully temperature controlled rig using peltiers and 30 something sensors...

#27 Mark Harry

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Posted 11 May 2006 - 04:39 PM

Hope you don't mind my quoting you Bill,

"My personal belief is that the biggest thing holding the performance of Newtonians back is the willingness of consumers to spend money on them. If we were willing to spend $3000 for a 6" Newtonian, most of the common Newtonian problems could be mitigated or eliminated and Newtonians would probably also be viewed as premium instruments. Alas though, most look at Newtonians as a source of relatively cheap aperature."

Exactly my sentiments. There is one rule that applies to ALL scopes. YOU GET WHAT YOU PAY FOR.(cheap=inferior)

Generally in my case, I have the choice to put as much work as I see fit in making a good optical train, so I have an advantage of being able to see what's possible with reflectors. Personally, I can, and have, made 6" reflector scopes ranging from F/6 through F/11, and if it's not extremely close to a dead-nuts tie, (refractor) other types of scopes are simply outclassed.

One detail, I believe the cost of a tube assembly for an exceptional 6" Newt can be had for around $12-1300 minimum bare bones. More frills, more money of course. Only one precisely figured surface, and a small accurate flat. Compare an apo, with 3 elements, (6 surfaces), and a diagonal. So many surfaces, and microfinish and smoothness becomes much more stringent in requirement.(hence the refractor's expense) not to mention the transmittance of selectively filtered light through 3 elements of glass. This is where the good reflectors catch up! Mark

#28 reflector74

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Posted 11 May 2006 - 05:10 PM

I would put up my 10" f/6 against any 9" refractor. I think it either would come very close or match it for tens of thousands of dollars less. At one point, you have to ask how much the secondary really intrudes into the actual visual image in the end. I have gotten stunning planetary images from a C14. Certainly, no planet killer equipment with its almost 40% obstruction! And, Mak-Cass' have the same obstruction as well.
I can only refer this back to the excellent posts from Daniel M's ideas on how to maximize newts that blow away large refractors consistantly!!! :ubetcha:


Aperture is everything, given the CO isn't outa control. I agree any good 10" reflector beats the pants of some smasller fancy shmancy refractor. Though for planetary viewing, it is best to have a longer focal length reflector with a small CO.

#29 galaxyman

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Posted 11 May 2006 - 10:49 PM

First I want to add also that the refractor will have a cleaner or crystal clear image compared to the reflector. No matter how small the secondary obstruction there is, it still will not be a tight or clear as a refractor. So I think the clearer and greater contrast image does give the refractor a different perspective in deep sky viewing.


I think one needs to be careful about overstating the difference made by the central obstruction, particularly when the c.o. is small. Generally when its below 20% and especially when it is <= 15% it has virtually no visible impact on the image.

The areas where the refractor has the advantage tends to come from the issues that are often left unaddressed in a Newtonian. Thermal currents, baffeling, the surface smoothness of the mirror, etc. Even when some of these issues remain unaddressed, I have seen 8" Newtonians perform as well as or a 6" Astro-Physics refractor (the Newtonian had an excellent mirror that was very smooth). I looked through another Newtonian that was made by an ATMer... he addressed many of the common shortcomings and it was a real stunner; no Astro-Physics or other large refractor was on that field that night to compare against, but its performance certainly would have given them a good run for the money had they been there.

Fortunately I do have both a large reflector and now a large refractor. As soon as the next dark window with hopefully clear skies comes around, I will put the BIG refractor through a thorough test on many deep sky objects, and will report it to Cloudy Nights.


The only problem here is that, I would guess that your Newtonian is not baffeled nearly as well as the refractor, and probably hasn't had the Newtonians additional thermal issues addressed either. It makes it hard to do a very good apples to apples comparison. Even really good Newtonanians like Starmaster and Portaball often make compromises to make the scopes easier to transport.

Below is my response from the same question posted in the refractor forum:

Actually a refractor that is close to the size of a reflector will outperform the larger scope on almost all deep sky objects.


I think I would qualify this statement carefully. A good reflector will trounce a poorly made refractor. Further, I think I would limit it to scopes of equal size. An 8" refactor can outperform an 8" Newtonian, but I am not sure that given the right scope that an 8" refractor would beat a 10" Newtonian (Indeed reports on the Better Mak-Newtonians seem to show that a really good 6" MNT is the essentially the equal of a 5" apo).

When seriously viewing DSO's there are many variables to consider. First as everyone knows dark skies makes a world of difference. As for the telescope three things must be taken into consideration. First, very good optics, second, is good eyepieces, and third is the key ingredient on why refractors perform so well. It's called the human eye and how does the first two parts of this equation help's the eye in observing DSO's.

Now the good eyepieces are used in both types of scope, but the refractor does give sharper and more contrast images then the reflector. This allows the eye of an experienced observer to pick out detail more easily. Basically, the refractor helps our eyes more then the reflector at the eyepiece. Also most refractors can be used at higher magnification, which also is essential with serious deep sky observing.


Ok, I agree that the refractor tends to have a slight edge in sharpness, but unless the reflector is poorly made, it will only be a slight edge... and that is only if we are comparing the Optical Tubes alone. Reflectors are often easier to mount since they can be mounted much closer to the ground. As a result it is usually substantially easier to get the Newtonian to be steady enough to take advantage of its capabilities. Regarding the magnification advantage, the Newtonian, again if well made, should support magnifications of up to 50X per inch, where the refractor might be able to go to 60-70X per inch. For Deep Sky work, I really don't see that extra boost to be that crucial.

I'm not saying that my new 8" f/9 refractor can outperform my 22" dob, The BIG dobs just overwhelms it on sheer size, but reflectors in the 10" to 12" can much indeed be challenged by a large refractor.


Karl, no offense, but if your 12" reflector is challeneged by an 8" refractor then there is something seriously wrong with the reflector. Even assuming the reflector uses standard aluminum coatings and the refractor the latest coatings, the 12" scope will be pulling in twice as many photons as the 8" scope.


Central obstruction has a impact, not so much of less light (though there is some), but more to
do with contrast and image quality. Basically less is better (thank
goodness for low profile focusers). In this case a refractor does have and
advantage with no central obstruction at all.


In many deep sky objects it will be apparent while others it's not. So inch
for inch the refractor will be superior. A refractor utilizes light more efficiently.

I have put my former 6" refractor against an 8" f/6 Meade. The refractor
did better on low surface brightness objects like M-33. It also was right
there when resolving tight globs. It also gave a more pleasing view of
M-42, thanks to higher contrast. From a decent dark site was seeing small
galaxies at 13.5 magnitude. Not bad for a 6" f/8 Chinese Achro (it did have
very good optics).

On a night a few months ago, my 4.7" refractor showed a better image of the galaxy Ngc-2683 than an old 8" SCT at the same magnification. Contrast and image quality was very apparent.

I think it's more than a slight edge in sharpness. It's not huge, but there
is a difference.


For seeing detail in most DSO's, high power is essential. So refractors
usually can handle high power more clearly.

No, nothing is wrong with my 12.5" dob. In fact many who have seen through
it say it's one of the best 12.5" scopes they've seen. A club member and I
built it back in 1993. It has a great Parks mirror with enhanced coatings.
So when I make my comparison between the two, it will be objective (pun
intended).

My thought ahead of time is the 12.5" will be better on most objects, but I
seriously believe it will be closer than one may think.

Also I did say slightly in size where the refractor will outperform the
reflector. A 10" may be surpassed (by the 8" refractor) on many objects,
but the 12.5" is almost 60% larger then the 10".

As I said the eye has a lot to do with what detail can be seen. Give it
clearer more contrast image at higher power can make a big difference.

One analogy can be used on DSO viewing and cost with a refractor.

Take a $350 36" standard TV. Then take a $2000 25" Plasma screen. Though
the 36" has the larger screen. The clearer 25" screen with better contrast
can be more pleasing.

This is why I spent the money for this BIG refractor. Though my 22" Dob is
my deepest scope, the 8" refractor will give a different perspective on
many objects.

Karl

22" f/4.5 Dob
12.5" F/4.8 Dob
8" f/9 refractor
4.7" F/5 Refractor

#30 galaxyman

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Posted 11 May 2006 - 11:14 PM

I would put up my 10" f/6 against any 9" refractor. I think it either would come very close or match it for tens of thousands of dollars less. At one point, you have to ask how much the secondary really intrudes into the actual visual image in the end. I have gotten stunning planetary images from a C14. Certainly, no planet killer equipment with its almost 40% obstruction! And, Mak-Cass' have the same obstruction as well.
I can only refer this back to the excellent posts from Daniel M's ideas on how to maximize newts that blow away large refractors consistantly!!! :ubetcha:


Aperture is everything, given the CO isn't outa control. I agree any good 10" reflector beats the pants of some smasller fancy shmancy refractor. Though for planetary viewing, it is best to have a longer focal length reflector with a small CO.

Actually aperture isn't everything. You need optical quality in any type of scope.

After years of observing and owning 5 refractors from 4.7" to 8" and 10 reflectors from 6" to 22" I can say inch for inch a refractor does better in both planets and deep sky.

As previously stated, high end observing is what the scope and eyepieces do for the eye. Contrast and clarity is what the eye craves for in seeing detail, this is a refractors strongest points. Also a refractor usually can be pushed in higher magnification, which benefits both planetary and deep sky.

Hey, I will tell you my most important scope for me is my 22" Dob. I observe galaxies at the very edge, so obviously the BIG dob is best. My point to all of this, is refractors are not just planetary scopes, but can do very good to great work in the deep sky.

Karl

22" f/4.5 Dob
12.5" F/4.8 Dob
8" f/9 refractor
4.7" F/5 Refractor

#31 bucky

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Posted 12 May 2006 - 12:49 AM

I spend the bulk of my observing time on the planets and
the moon. I have owned a variety of reflectors and
refractors over the years. Without a doubt, my refractors
produced the most consistenty sharp images. Only on rare
will my 8" or 10" newts show a clearer image over the refractors (I have a 4.7" and a 6" refractor). Better yet,
the refractors never need collimation and they are much less affected by "atmospherics".

Bucky

#32 Daniel

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Posted 12 May 2006 - 10:05 AM

My 10" SN and 5" achro Refractor are really close when it comes to visuals. I have compared on many nights which was better. The same mount, eyepieces, ect. Planetary views were better with the 5", while DSO's were better with the 10".
I can't complain about either nor compare. I am just kinda caught in the middle. I cannot afford....well I guess... justify spending thousands on a small app. refractor when I could take that 2-3 grand and purchase a large app reflector. I guess that app. does rule, but there are certain cases that a refractor is simply a better choice for the observing session planned.
Just my 2 cents from an average equipment owner.
I feel most peeps on this forum are of the type like me, and just want to have clear skies and a decent chunk of hardware to look through.
Final thoughts are that, both are the same... but app. does rule.

#33 mistyridge

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Posted 12 May 2006 - 11:01 AM

Just an observation after reading this thread and and Dans big 15 page thread. It seems, based on all the various qualitative shoot outs, and anecdotal comments and views, that really good reflectors need to be about 1" larger than a comparable refractor. Now this is just an observation since I am no expert optical engineer.

#34 Bill McHale

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Posted 12 May 2006 - 01:30 PM

[quote name="galaxyman"]
Central obstruction has a impact, not so much of less light (though there is some), but more to
do with contrast and image quality. Basically less is better (thank
goodness for low profile focusers). In this case a refractor does have and
advantage with no central obstruction at all.
[/quote]

Two thoughts here. 1. People do make unobstructed reflectors, DGM for example makes a highly regarded one.

2. As I pointed out, the effects of obstructions have been shown to be effectively negligable much below 20%.

Actually, in larger scopes, low profile focusers can do more harm than good since they make it harder to properly baffel the focuser.

[quote]
In many deep sky objects it will be apparent while others it's not. So inch
for inch the refractor will be superior. A refractor utilizes light more efficiently.

[/quote]

It is granted that a refractor utilizes light more efficiently, however, I think some of us are disputing the level of efficiency you seem to be giving to the refractor. A really well made reflector is not going to trail a refractor by that much.

[quote]

I have put my former 6" refractor against an 8" f/6 Meade. The refractor
did better on low surface brightness objects like M-33. It also was right
there when resolving tight globs. It also gave a more pleasing view of
M-42, thanks to higher contrast. From a decent dark site was seeing small
galaxies at 13.5 magnitude. Not bad for a 6" f/8 Chinese Achro (it did have
very good optics).

[/quote]

Ok, but how good exactly was the Meade? How good was the figure? How smooth? Did it have good coatings on the mirrors? Was the scope collimated properly? Had any attempt been made to baffel the scope against stray light? Was any attempt made to mitigate the thermal effects?

See this is where anecdotal evidence is limiting. If I had a lousey refractor and an excellent reflector I could make the same sort of claims about the reflector. Its really only when you have excellent examples of each, that a valid comparison about the merits of the design can really be made.

[quote]
On a night a few months ago, my 4.7" refractor showed a better image of the galaxy Ngc-2683 than an old 8" SCT at the same magnification. Contrast and image quality was very apparent.

I think it's more than a slight edge in sharpness. It's not huge, but there
is a difference.
[/quote]

Just a point, but SCTs are not renowned for their sharpness, also as sold they are not effectively beffled and many users never collimate them properly. All of which leands to decidedly substandard performance.

[quote]
For seeing detail in most DSO's, high power is essential. So refractors
usually can handle high power more clearly.

[/quote]

Sure they can handle the power more clearly if you are going to be pushing it beyond say 50X an inch. For many of us though, that simply is not an issue with scopes 8" and larger by the simple fact that local seeing conditions just don't often support that kind of magnification. Most of my observing is done at under 300X simply because anything more is not supported by the seeing in the Mid-Atlantic.

[quote]
No, nothing is wrong with my 12.5" dob. In fact many who have seen through
it say it's one of the best 12.5" scopes they've seen. A club member and I
built it back in 1993. It has a great Parks mirror with enhanced coatings.
So when I make my comparison between the two, it will be objective (pun
intended).
[/quote]

Intended, but not necessarily possible. The only way to make the test truely objective is if you could view without knowing which scope was which. You seem to have some very preconceived notions regarding the performance of the scopes which tends to bias observations... often rather strongly.

Another thought is that, even if it is one of the better 12.5" scopes out there, it is still possible that the scope's performance is still well below optimum. Most scopes that large make compromises to improve portability, not to ensure the scope is very well baffeled.

[quote]
My thought ahead of time is the 12.5" will be better on most objects, but I
seriously believe it will be closer than one may think.

[/quote]

Only if seeing conditions just are not that good. On Globulars and double-stars the contest should not even close; on other deepsky the extra aperature still should overwhelm any disadvantage that might be gained by the refractor.

[quote]
Also I did say slightly in size where the refractor will outperform the
reflector. A 10" may be surpassed (by the 8" refractor) on many objects,
but the 12.5" is almost 60% larger then the 10".
[/quote]

Well, assuming the 10" is a good one, I am even highly dubious that the 8" refractor will outperform it even then. The image may appear cleaner, but the 10" should be able to resolve finer details. Assuming it has a reasonable sized secondary it should also have a higher signal to noise ratio and therefore have better contrast and thus be able to see fainter details. Again, I am talking about a 10" where efforts have been made to ensure it has a very good mirror, and efforts have been made to adress all the potential issues that can limit the performance of the reflector.

[quote]
As I said the eye has a lot to do with what detail can be seen. Give it
clearer more contrast image at higher power can make a big difference.

One analogy can be used on DSO viewing and cost with a refractor.

Take a $350 36" standard TV. Then take a $2000 25" Plasma screen. Though
the 36" has the larger screen. The clearer 25" screen with better contrast
can be more pleasing.

[/quote]

Of course you can spend $800 and get a 30" Hi-Def CRT and it will outperform either of the other Televisions. This is what I am talking about. Just as alot of people seem to think that a plasma necessarily produces a better picture than a CRT (They don't, in fact CRTs still lead all the other display formats in just about every category on an inch per inch basis) alot of people seem to think that reflectors necessarily can't match up with more exotic designs. The simple fact is that much of the difference between telescopes has alot to do with what is done with the design, not with the design itself. We love the fact that we can get 12" Newtonians for under $1,000 and 6" Newtonians for $300, but then we talk about how much better the $5,000 5" inch Apo is than the 6" Newtonian. I firmly believe if you put half of that money in the Newtonian that people would stop talking about how great the Apo is (and mind you, I own a 5" Apo myself and love to use it).

#35 Mark Harry

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Posted 12 May 2006 - 08:00 PM

I just verified about a week ago,in another thread, of using a 6" Newt at about 70x,80x, and 100x/inch with much better than expected results. If the time, or money is spent wisely in getting a properly made Newt, it's possible to have something that's going to give an expensive refractor a really hard time. (inch per inch) for a fraction of the price.

(What's in YOUR wallet?!) Mark

#36 galaxyman

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Posted 13 May 2006 - 12:23 AM

Two thoughts here. 1. People do make unobstructed reflectors, DGM for example makes a highly regarded one.

2. As I pointed out, the effects of obstructions have been shown to be effectively negligible much below 20%.

Actually, in larger scopes, low profile focusers can do more harm than good since they make it harder to properly baffel the focuser.


Effects of obstruction are still there. Stars are never as sharp as a refractor nor is contrast as good. We are most definitely going on circles with this part.
It is better to use a low profile focuser no matter how large. It can make a big difference in the size of the secondary obstruction. Many large dob owners use a shield opposite of the focuser.

Ok, but how good exactly was the Meade? How good was the figure? How smooth? Did it have good coatings on the mirrors? Was the scope collimated properly? Had any attempt been made to baffel the scope against stray light? Was any attempt made to mitigate the thermal effects?

See this is where anecdotal evidence is limiting. If I had a lousey refractor and an excellent reflector I could make the same sort of claims about the reflector. Its really only when you have excellent examples of each, that a valid comparison about the merits of the design can really be made.


It was a very good Meade with that highly regarded mirror. Well collimated.
Also my 6” f8 refractor was not top of the 6” refractor line either, so both scopes were in the same class or playing field.

Sure they can handle the power more clearly if you are going to be pushing it beyond say 50X an inch. For many of us though, that simply is not an issue with scopes 8" and larger by the simple fact that local seeing conditions just don't often support that kind of magnification. Most of my observing is done at under 300X simply because anything more is not supported by the seeing in the Mid-Atlantic.



Hmm, I live in Pa. and have pushed my 6” refractor to 490x with good results. My 22” Dob to 1002x. So sometimes 50x or more can be utilized.

Intended, but not necessarily possible. The only way to make the test truely objective is if you could view without knowing which scope was which. You seem to have some very preconceived notions regarding the performance of the scopes which tends to bias observations... often rather strongly.

Another thought is that, even if it is one of the better 12.5" scopes out there, it is still possible that the scope's performance is still well below optimum. Most scopes that large make compromises to improve portability, not to ensure the scope is very well baffeled.



First of all the 12.5” is very well baffled. It’s made completely of wood and has an internal skeleton with natural baffles.
If you want to know how good this scope is, call High Point Scientific and ask for Dave Barrett. He owned this scope for a time when I sold it to him to buy a 16” Meade Dob. I bought it back when I sold the 16” to get the 22” Dob. Needed a mid-size dob to compliment the BIG scope.
As for comparison, yes the very best way would be side by side. But, I will tell you that after 38 years of observing with many notes on various DSO’s with all my scopes. I think I can make a serious judgment on how well the 8” refractor compares. Also as lead observer for what may be perhaps the most serious DSO observers (Chesmont Astronomical Society) you will find anywhere. I’m sure many of my club members will scrutinize what the BIG refractor will do in deep sky observing.

Well, assuming the 10" is a good one, I am even highly dubious that the 8" refractor will outperform it even then. The image may appear cleaner, but the 10" should be able to resolve finer details. Assuming it has a reasonable sized secondary it should also have a higher signal to noise ratio and therefore have better contrast and thus be able to see fainter details. Again, I am talking about a 10" where efforts have been made to ensure it has a very good mirror, and efforts have been made to adress all the potential issues that can limit the performance of the reflector.



Yes, this is a possibility, though as with reflectors, refractors can be fine tuned also. For years the bad to fair diagonals were used on very good refractors. These were the weak link. Fortunately the exceptional diagonals that are available now strengthen that link substantially.

Of course you can spend $800 and get a 30" Hi-Def CRT and it will outperform either of the other Televisions. This is what I am talking about. Just as alot of people seem to think that a plasma necessarily produces a better picture than a CRT (They don't, in fact CRTs still lead all the other display formats in just about every category on an inch per inch basis) alot of people seem to think that reflectors necessarily can't match up with more exotic designs. The simple fact is that much of the difference between telescopes has alot to do with what is done with the design, not with the design itself. We love the fact that we can get 12" Newtonians for under $1,000 and 6" Newtonians for $300, but then we talk about how much better the $5,000 5" inch Apo is than the 6" Newtonian. I firmly believe if you put half of that money in the Newtonian that people would stop talking about how great the Apo is (and mind you, I own a 5" Apo myself and love to use it).



My point on the TV analogy was only about how different scopes give different views. The refractor no doubt gives the clearest most contrast image across the whole field of view. In other words, it’s a different look.

Basically saying people who purchase these high end or large refractors are just wasting money is incorrect. They as I do, feel these scopes do a terrific job in any type of astronomical interest. The views per inch of aperture are second to none.

Keep an eye out for my review of this beautiful TMB 8” F/9 refractor I just received.

I promise it will be thorough and quite honest. I will also have many of my club members on hand to offer their comments.

Though I will say after 38 years of observing (started at age 10) owning 15 telescopes and basically taught most of the Chesmont members on deep sky observing, I believe I made the right choice in my newest purchase.

I saw what my 6” refractors could do. Now this much larger with better optics refractor will most definitely provide some stunning views.

Karl

22" f/4.5 Dob
12.5" F/4.8 Dob
8" f/9 refractor
4.7" F/5 Refractor

#37 claytonjandl11

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Posted 13 May 2006 - 04:02 PM

It's kind of interesting, I started this thread on the refractor forum and the reflector forum to see what both sides had to say about the 2 different scope desighns. Basically what size would a refactor have to be to equal a reflector, or visa versa, assuming all things are equal ie. quality of optics, seeing conditions, thermal currents, ect. I tend to slightly agree with Bill more than I do with Karl, but only on some little issues. Mainly with Karl's comment about using high power for DSO? What do you consider high power? On my 20" Starmaster I average no more than 150X or less on DSO, and on my NP127 I find the average highest usefull power for most DSO is well under 100X. Now there are a few DSO that will take much more power on both scopes but they are few. I find the more I up the power on DSO on my Np127 the dimmer it gets and the less I can see and the less pleasant it looks, and I understand that it's an appeture thing and no fault of the scope, where as my 20" even though I could go much higher in power it will not dim as much, and I can see the same if not slightly more detail than before. What amazes me most on my little NP127 is at the detail I CAN see with it, which I didn't expect to see, which is on average I'd have to say give or take about half of what I can see in my 20".(I hope this makes sense to what I'm trying to say)

Still being what it is I can see much more in my 20" than my NP127 on DSO or even planets at much higher power.

After all thats been posted it seems to me if you had 2 high quality scopes, reflector and refractor at the same appeture, that the refractor would slightly edge out the relector by a hair. If that is the case and there is no big difference, at that point I would not worry about splitting hairs.

Nick T.

#38 Alan French

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Posted 13 May 2006 - 04:36 PM

Nick,

If you are interested in a good discussion on how refractors and reflectors compare on the planets, look up the two part article "Rules of Thumb for Planetary Telescopes," by William Zmek in the July (page 91) and September (page 83), 1993, issues of Sky & Telescope.

Clear skies, Alan

#39 skynut

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Posted 13 May 2006 - 05:19 PM

After reading this entire thread,it seems to me that it's a matter of personal perference. I lean toward DSO's so I have a 16" dob, but it also provides good images of the moon and planets too. I think it all depends on what pleases YOU in the eyepiece. if it's a refractor -- KOOL , if it's a big Dob, or an SCT -- GO FOR IT!!! Nobody can tell you what pleases you in the eyepiece but YOU!!

#40 reflector74

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Posted 13 May 2006 - 06:35 PM

I would put up my 10" f/6 against any 9" refractor. I think it either would come very close or match it for tens of thousands of dollars less. At one point, you have to ask how much the secondary really intrudes into the actual visual image in the end. I have gotten stunning planetary images from a C14. Certainly, no planet killer equipment with its almost 40% obstruction! And, Mak-Cass' have the same obstruction as well.
I can only refer this back to the excellent posts from Daniel M's ideas on how to maximize newts that blow away large refractors consistantly!!! :ubetcha:


Aperture is everything, given the CO isn't outa control. I agree any good 10" reflector beats the pants of some smasller fancy shmancy refractor. Though for planetary viewing, it is best to have a longer focal length reflector with a small CO.

Actually aperture isn't everything. You need optical quality in any type of scope.

After years of observing and owning 5 refractors from 4.7" to 8" and 10 reflectors from 6" to 22" I can say inch for inch a refractor does better in both planets and deep sky.

As previously stated, high end observing is what the scope and eyepieces do for the eye. Contrast and clarity is what the eye craves for in seeing detail, this is a refractors strongest points. Also a refractor usually can be pushed in higher magnification, which benefits both planetary and deep sky.

Hey, I will tell you my most important scope for me is my 22" Dob. I observe galaxies at the very edge, so obviously the BIG dob is best. My point to all of this, is refractors are not just planetary scopes, but can do very good to great work in the deep sky.

Karl

22" f/4.5 Dob
12.5" F/4.8 Dob
8" f/9 refractor
4.7" F/5 Refractor


Dah.. We must assume optical quality obviously, but a good reflector with enough aperture will blow the doors off most refractors on any object in space. To me, refractors do have snob appeal, but to get a really good one, you have to spend a fortune. I'm not into that scam.

#41 braindontstop31

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Posted 13 May 2006 - 06:51 PM

I have only had 4 refractors, three achros and one chinese apo. I have to say the Orion 100 ED is a very nice scope, great optics, quick cool down . But my old Celestron C8 Newt would blow away the Orion 100mm ED hands down on planets and deep sky for a little less money. It is a personnel preference of course. Every scope has it good and bad points. I have bought and sold a lot of scopes trying to find the correct mixture for my viewing preferences. I have ended up with a 6" mak-cass and a 10" dob. I can take the 6" camping with me and the 10" dob is quick to setup and for kids it is great. I quess the bottom line is to enjoy your scope whatever it is and use it!!!! :jump:

#42 Alan French

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Posted 13 May 2006 - 07:02 PM

Dah.. We must assume optical quality obviously, but a good reflector with enough aperture will blow the doors off most refractors on any object in space. To me, refractors do have snob appeal, but to get a really good one, you have to spend a fortune. I'm not into that scam.


Why do you call it a scam?

Clear skies, Alan

#43 galaxyman

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Posted 13 May 2006 - 11:41 PM

It's kind of interesting, I started this thread on the refractor forum and the reflector forum to see what both sides had to say about the 2 different scope desighns. Basically what size would a refactor have to be to equal a reflector, or visa versa, assuming all things are equal ie. quality of optics, seeing conditions, thermal currents, ect. I tend to slightly agree with Bill more than I do with Karl, but only on some little issues. Mainly with Karl's comment about using high power for DSO? What do you consider high power? On my 20" Starmaster I average no more than 150X or less on DSO, and on my NP127 I find the average highest usefull power for most DSO is well under 100X. Now there are a few DSO that will take much more power on both scopes but they are few. I find the more I up the power on DSO on my Np127 the dimmer it gets and the less I can see and the less pleasant it looks, and I understand that it's an appeture thing and no fault of the scope, where as my 20" even though I could go much higher in power it will not dim as much, and I can see the same if not slightly more detail than before. What amazes me most on my little NP127 is at the detail I CAN see with it, which I didn't expect to see, which is on average I'd have to say give or take about half of what I can see in my 20".(I hope this makes sense to what I'm trying to say)

Still being what it is I can see much more in my 20" than my NP127 on DSO or even planets at much higher power.

After all thats been posted it seems to me if you had 2 high quality scopes, reflector and refractor at the same appeture, that the refractor would slightly edge out the relector by a hair. If that is the case and there is no big difference, at that point I would not worry about splitting hairs.

Nick T.


Nick - First of all I understand that some people like to use low power for DSO observing. Problem though is to see detail the eye needs both good contrast and in many cases a more magnified object. Basically more detail can be seen in and object large and dim, then small and bright. For most objects to increase contrast, higher magnification is needed. In fact many objects if not most seem brighter at higher power, thanks to the contrast gain. it's a signal to noise thing. Basicllay the gain in contrast out weighs the spreading of light.

Using say no more than 150x with a 20" is missing not only a lot of detail, but a lot of objects, period. Many galaxies and planetary nebula which there are a large number that can be seen with your scope, need more magnification to really be seen at all. In your 20" and from a dark location all Ngc galaxies are visible, so are many IC's, UGC's, MCG's and so on. Dust lanes in edge-on galaxies, spiral arms, HII regions are more readily visible at higher magnification. Also your 20" can see many of the Abell galaxy clusters, Hickson groups and so on, but only using high power.

Most planetary nebulas are small, and some times even to pick them out from a star field, high power needs to be used. Detail in many of them can be terrific with some big time power! Take a look at the Cat's Eye nebula (Ngc-6543) at over 400x. I guarantee you it will be something you won't forget! Many tight globs also will not resolve at low power.

Even some big nebulas like the Lagoon or Orion can take on a incredible experience at high power. It feels like you in the nebula itself with detail galore.

Deep sky observing is really an art. Experience and patience will go a long way.

More power to ya!

Karl

22" f/4.5 Dob
12.5" F/4.8 Dob
8" f/9 refractor
4.7" F/5 Refractor

#44 galaxyman

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Posted 14 May 2006 - 12:35 AM


Dah.. We must assume optical quality obviously, but a good reflector with enough aperture will blow the doors off most refractors on any object in space. To me, refractors do have snob appeal, but to get a really good one, you have to spend a fortune. I'm not into that scam.


Why do you call it a scam?

Clear skies, Alan


Alan, some people just don't get it, as in reflector74.

Every type of scope has it's own appeal and view of the Universe.

My large Dobs (12.5" and 22") show an amazing amount of objects and detail, But the views are different then the refractor. The contrast and clarity of a refractor has a certain appeal. It's not just about my 22" Dob blowing away my new 8" refractor. It is the different look the refractor gives on each object with unsurpassed contrast and clarity.

So no I'm not a snob, but someone who loves to observe and really appreciates the fine equipment that I have been able to own (and of course my wife agreed upon).

I know from experience what to at least expect from my new refractor. My excitement comes from what I will undoubtedly not expect!

I guess here's to all of us refractor snobs out there :waytogo:


Karl

22" f/4.5 Dob
12.5" F/4.8 Dob
8" f/9 refractor
4.7" F/5 Refractor

#45 reflector74

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Posted 14 May 2006 - 12:45 AM


Dah.. We must assume optical quality obviously, but a good reflector with enough aperture will blow the doors off most refractors on any object in space. To me, refractors do have snob appeal, but to get a really good one, you have to spend a fortune. I'm not into that scam.


Why do you call it a scam?

Clear skies, Alan


Alan, some people just don't get it, as in reflector74.

Every type of scope has it's own appeal and view of the Universe.

My large Dobs (12.5" and 22") show an amazing amount of objects and detail, But the views are different then the refractor. The contrast and clarity of a refractor has a certain appeal. It's not just about my 22" Dob blowing away my new 8" refractor. It is the different look the refractor gives on each object with unsurpassed contrast and clarity.

So no I'm not a snob, but someone who loves to observe and really appreciates the fine equipment that I have been able to own (and of course my wife agreed upon).

I know from experience what to at least expect from my new refractor. My excitement comes from what I will undoubtedly not expect!

I guess here's to all of us refractor snobs out there :waytogo:


Karl

22" f/4.5 Dob
12.5" F/4.8 Dob
8" f/9 refractor
4.7" F/5 Refractor


You're entitled to your opinion, and so am I. "Snob appeal" doesn't mean refractor owners are snobs. Don't misinterpret and take things so literally! Refractors are lovely, but pricey per inch of aperture. I call it a scam, but it doesn't affect me that much - I own a Coronado SM 60 .5A refractor and it is a beauty! Chill. I meant no offence whatsoever, sir.

#46 reflector74

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Posted 14 May 2006 - 12:55 AM

Karl,

To me, there shouldn't be any contest between the two designs IMHO. I generally prefer Newtonian designs, but I know where to go to spend tons of money if I want the really wonderful exquisite clarity for a particular unit of aperture. I suppose ease of setup with my dobs come into the picture for me. It's a blessing that I now do astronomy day and night. My Coronado SM60 double stacked scope has a CO for its intended purpose! Go figure! That 8" refractor of yours is likely beyond amazing on the planets and a pleasure to observe with... You'll get more good nights of seeing with it than the 22" dob.

#47 blandp11

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Posted 14 May 2006 - 08:49 AM

To steal a line from Arthur Dent, "Ah, this is obviously some strange usage of the word 'scam' that I wasn't previously aware of." ;)

Philip

I call it a scam...I meant no offence whatsoever...



#48 Alan French

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Posted 14 May 2006 - 08:58 AM


Dah.. We must assume optical quality obviously, but a good reflector with enough aperture will blow the doors off most refractors on any object in space. To me, refractors do have snob appeal, but to get a really good one, you have to spend a fortune. I'm not into that scam.


Why do you call it a scam?

Clear skies, Alan


I still have no idea what you mean when you say it is a "scam."

Under rainy skies, Alan :question:

#49 snorkler

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Posted 14 May 2006 - 09:37 AM

Since you SRFs won't stop beating the dead horse, there is some snob appeal to claiming your refractor is only a _", and rivals Newts that are a couple inches larger. In a way, it's a scam, because we all know a bigger and cheaper Newt can beat any refractor on detail and digging out the dim fuzzies like Arp Madore 1. It's just a matter of how much larger your Newt has to be to beat the refractor.

I think of the woman who bought a Cadillac Escalade to drive up the mountain to her hillside property. She got scammed because it doesn't have a low range in its transfer case. Anybody thinking their refractor has the best views possible has never looked through a large reflector. The refractor may have the best views possible for a 4" or 6" or 8" scope, but the best 8" isn't going to beat a well-built and operated 12, 14, 16, or 18, let alone a 22, 25, 28, 30, 32, 36, 40, etc. For the price of a top 8" refractor, I can buy five 30" reflectors. Believe me, I would feel scammed if I spent $100,000 on a refractor marketed as "the best", only to learn that I don't have a chance to see 1/5 the objects that an 18" reflector can show me, and that the reflector shows me more detail on every target below mag 15, or mag 10, or mag 5, ad nauseum. If I went into it knowing it's the best for a given aperture, that's different. Then I'm just buying the best for a certain set of conditions, knowing there are better choices.

#50 reflector74

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Posted 14 May 2006 - 02:24 PM

Since you SRFs won't stop beating the dead horse, there is some snob appeal to claiming your refractor is only a _", and rivals Newts that are a couple inches larger. In a way, it's a scam, because we all know a bigger and cheaper Newt can beat any refractor on detail and digging out the dim fuzzies like Arp Madore 1. It's just a matter of how much larger your Newt has to be to beat the refractor.

I think of the woman who bought a Cadillac Escalade to drive up the mountain to her hillside property. She got scammed because it doesn't have a low range in its transfer case. Anybody thinking their refractor has the best views possible has never looked through a large reflector. The refractor may have the best views possible for a 4" or 6" or 8" scope, but the best 8" isn't going to beat a well-built and operated 12, 14, 16, or 18, let alone a 22, 25, 28, 30, 32, 36, 40, etc. For the price of a top 8" refractor, I can buy five 30" reflectors. Believe me, I would feel scammed if I spent $100,000 on a refractor marketed as "the best", only to learn that I don't have a chance to see 1/5 the objects that an 18" reflector can show me, and that the reflector shows me more detail on every target below mag 15, or mag 10, or mag 5, ad nauseum. If I went into it knowing it's the best for a given aperture, that's different. Then I'm just buying the best for a certain set of conditions, knowing there are better choices.


This guy knows what he is talking about. The money you end up spending IS a scam. For some 8" APO that requires additional HUGE and EXPENSIVE mounting, I can spend a fraction of the price and still have a fine 20" reflector of excellent quality. When it comes to resolving the finest detail - I'm not sorry btw - aperture wins. The refractor forum is where people need to argue the superiority of refractors and not take it personally when someone says they are just so darn expensive. Best for a given aperture.... Hmmm.... Let's say my 12.5" f/5 or 20" f/5 Obsession eats a 8" whatever design for breakfast. Am I at the reflector forum??


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