234 replies to this topic

[mikemarotta]

Allow me to add one more reason for having the refractor: Compatibility.
 
Compatibility. Most of mine - 70mm, 102mm, 115 mm - all fit on Vixen mounts. I can set up on either of two tripods, manual Alt-Az or computerized German Equatorial.
 
And that applies also to my reflector, the OneSky from Astronomers Without Borders. (It fits well on the Explore Scientific Twilght 1 mount, not the Celestron AVX German Equatorial.) 
 

 

Aperture is certainly king, quality is queen and the mount is the minister. 
...
To argue reflector vs. refractor is like arguing Lamborghini vs. Truck.
  

"Aperture is certainly king, quality is queen and the mount is the minister. A truly regal reflector is cheaper and and sets up easier and faster than a refractor of equal capability."
 
I guess for visual the above works.  However for imaging the mount is king, aperture is queen and quality is the minister.

 

Actually, I would say that the mount is king, just as Avalon the sheath of Excalibur was more important than the sword. The optics are pretty much a given. Of course, quality counts and you can go very wrong buying at the entry-level. Even so, with most refractors  sold as first instruments -- Celestron, Meade/Orion, Explore/Bresser --the optical tube assembly (OTA) is acceptable but the seller finds their margin in the mount and eyepieces. 

 

And this discussion was never supposed to be about which is better. I have never responded with that in mind. The original question is "Why are Refractors so Popular, even Though the Aperture is Small." To say that comparing refractors to Dobsonians is comparing a sports car to a truck aligns well with the honest answers here: apples and oranges. (And I happen to own a Civic, not a King Ranch, because I am an urbanite. I also do my astronomy from the city. I twice went to dark sky sites 60 miles outside of town. So, while i grant the attraction for a Dobsonian reflector for other people, it is not what I do in this hobby.)

 

Best Regards (and Clear Skies),

Mike M.

 

(PS: New interesting discussion here which already has come up once this week as I recall: The locking screws cause misalignment of the primary mirror after collimation.

https://www.cloudyni.../#entry12459104

 I had the same problem with my little AWB 130-mm Newtonian reflector. Being careful and gentle helps a lot ... not better, just different...)

Edited by mikemarotta, 30 January 2023 - 04:38 PM.

[CarolinaBanker]

At star parties, on all CN boards and even talking to friends, they are all about buying the best refractor with the best glass.  Overall, I’m a newbie to this amazing hobby but have been here since 2019 but have been studying science/astrophysics forever.  

 

Is the main thing about refractors the wide field view and observing DSO and Astrophotography?  Because the aperture is so small on refractors and people are going crazy about 72mm, 90mm and 102mm scopes.  Anything above that is so expensive.  

 

An SCT or Dob gives so much aperture for planets and solar system objects but their narrow field of view is what the refractor fans are annoyed at?

 

(disclaimer:  I am considering buying a refractor to supplement my Celestron 9.25 and to possibly double mount it).

I own a 60mm and a 102mm refractor, I love their versatility and ease of use. I don’t need much more aperture to see the showcase objects and many of the more subtle ones. I readily acknowledge that I’m the weakest link in the optical chain. I like that I can just walk out the door and observe. If I want to go take a quick peak, I can be set up in 2 minutes, the longest part of which is getting my observing chair from upstairs. I love the grab and go nature, the sharp contrast, no need to collimate, for me it’s just perfect.

[dave253]

I concur with all the above!

 

My little (80mm) refractor gets the most use of our scopes.

 I can pick it up one handed, it shows pinpoint stars, and plenty of DSOs under a dark sky.

[gnowellsct]

If I strapped my ST80 onto my C8, it might save the ST80 for me... I might have to try it. I have little interest in the scope by itself, but it wouln't be too particularly taxing to add to my mount.

That's how it starts. Then one day you think, man, I need to up my game and ride first class. Going to get me an ed doublet. And then when that feeling wears off it's a triplet APO for you! So you better start saving now.

[Wolfwatcher]

As some others here have stated or hinted: refractors are simply cool! They are what most of us imagine when thinking of a telescope. That's for a reason: they ARE cool because they are among the oldest designs and still around, the kind first used to dramatically challenge (and upset) what humanity thought was settled and unquestionable about the night sky. A simple 2" refractor disrupted those old assumptions long ago, and a small one still can, as popular knowledge of the night skies today is, unfortunately, not always so advanced after hundreds of years of progress in scientific observation and technology. 

 

My own advice for the OP, since a 9+inch scope is already in hand, is to look for the SMALLEST, high quality affordable refractor, to fill in where the other scope cannot so easily fit in. One, it won't compete, meaning for whatever reason (travel, etc.), it's obviously the more useable choice for the situation at hand.  Two, because anything larger than about 6" for me (don't care what kind) necessitates considerations of weight, trouble to carry out, or set up, or travel, with a hefty mount, etc., causing me to think about taking it out, or with me when traveling, in the first place. I do have more lazy tendencies in my older age, and I'm more apt than I used to be to place more value on convenience. Third, a small refractor can easily mount on a larger scope as a finder, or on a dual mount. Finally, such a refractor has a certain "fun" factor not often found in larger, more sophisticated and complicated units. Kind of brings me back to the joys of my first discoveries.

 

Recently, I acquired a 60mm Tele Vue refractor. Weighs 3 lbs., serves as its own finder scope, works on the lightest mounts or camera tripod, simple focusing system, serves up images of Jupiter, the moon and M42 that are just plain enjoyable from my backyard, and dispels for me any questions about the quality of images it delivers. It slips under a plane seat as a "personal item" when getting the chance to travel to a darker site, or to watch wolf behavior in the Lamar Valley of Yellowstone National Park. Mounts on anything (at 10x or less, can easily be hand held), and is a terrific tool! Of course it won't compete with several of my larger aperture scopes, even though it cost much more than some of them, but I could care less because I'm retired and can spring for it, and I'm out using it. A lot.

Edited by Wolfwatcher, 29 January 2023 - 11:48 PM.

[rhetfield]

I hope that's not a serious comment.  I can collimate a Newtonian roughly with no tools at all.  It won't be right on, of course.  A decent Cheshire combo tool, which will put it right on, more easily if you've got a center spot, is something like $35.

 

Chris

99% of the time, I use Polaris for free.  Maybe for 5 minutes every 10 sessions.  My only other tool is the so-so Cheshire that came with the scope.  It comes out maybe once every year or two.

[KWB]

I also have a small 60mm, 360mm focal length refracting telescope. For my usage it's too aperture limited to be a general purpose observing instrument. It does however do a couple of things I can't get with another telescope design and that is using a 2 inch eyepiece over a 6 degree TFOV of the sky at lower powers is possible and it provides me with an excellent little spotting scope for wildlife. Without the diagonal this telescope is 9.75 inches long. It is optically excellent IMO.

[epee]

I'm unaware a 102 mm F/6 ED doublet available the US for under $500. Interesting. 

 

 

I'm curious to hear about this sub-$500 scope, too.

Forgive my poor analogies, I meant no offence.

 

Likewise, I'm pretty oblivious to what the retail market is currently like, because I'm not shopping. When I bought my Meade Infinity 102mm it retailed for about $300. I bought it, used for $100.

[KWB]

Forgive my poor analogies, I meant no offence.

 

Likewise, I'm pretty oblivious to what the retail market is currently like, because I'm not shopping. When I bought my Meade Infinity 102mm it retailed for about $300. I bought it, used for $100.

That must have been quite some time ago. Exceedingly unlikely someone in 2023 will find a used sample in decent condition for $100.

[epee]

That must have been quite some time ago. Exceedingly unlikely someone in 2023 will find a used sample in decent condition for $100.

Defiantly pre-COVID pricing.

At the time I considered it a killer deal; hardly used, still with the box.

[Ihtegla Sar]

 

I'm unaware a 102 mm F/6 ED doublet available the US for under $500. Interesting.

I too am unaware of one for under $500 but you can get this excellent 102mm f/7 ED for $549.

 

 

https://www.astronom...a.html?___SID=U

 

[PNW]

I picked my Infinity 102 for $200, new, delivered. That was then, but deals are still out there. A couple of months ago I was surfing Craigslist and saw an Infinity 102 listed as a "spotting scope" for $50. Could part of their popularity be that there are still plenty of cheap Achro's out there?

Edited by PNW, 30 January 2023 - 03:21 PM.

[epee]

Mine doubles as a spotter when needed.

[TheChosen]

I believe the shortest answer here is "Because it can fit in a suitcase". Which most other telescopes hardly can.

I love my DOB 8 but I was also forced to buy a refractor as a secondary, highly mobile scope. It is called a spotting scope but it is a refractor with 100mm aperture and a weight of only 1.1kg. It has a nice carry bag that I can put on my shoulder. Can't do that with my 23kg DOB.

[Vertigo]

To some extent, this question might better be posed as "Why are small-aperture scopes so popular?"

Given the choice to use a small aperture, refractors have numerous advantages over other designs. That's especially true for apertures of 80 mm or less, where it's actually hard to find any kind of scope other than a refractor. There are a handful of 70-mm Maks running around, and 76-mm Newts are viable as starter scopes. But the smallest widely used catadioptrics are 90-mm Maks, and the smallest widely used Newts have 114-mm mirrors.

The basic reasons that refractors work so well in small apertures is that they have no central obstructions and they have a virtually unlimited focusing range. Both of those are serious issues for small-aperture Newts and many catadioptric designs.

 

More to the point, the disadvantages of refractors -- which are overwhelming in large apertures -- are very minor in small apertures. For any given kind of glass and focal ratio, a refractor's false color is directly proportional to its aperture. So a 60-mm f/10 flint/crown achromat has barely perceptible false color, whereas a 200-mm f/10 flint/crown achromat has terrible false color.

 

For any given aperture, refractors are the least portable and most problematic design, due to the fact that you're viewing from the bottom of a long tube. That means that the eyepiece height varies more than it does for any other design, and that you need a taller and heftier tripod than you do for any other design.

 

Consider, for instance, my Z130, a 130-mm f/5 tabletop pseudo-Dob. When it and I are both sitting on surfaces at essentially the same height, I can view all the way from the horizon to the zenith in perfect comfort. The entire setup, including the table and the chair, is trivial to carry in a single trip.

 

Now consider a 130-mm refractor. You have three choices: use a small focal ratio and accept the massive false color, use exotic glass and a focal ratio likely around f/8, or use flint/crown with a focal ratio around f/15. The APO will have a tube roughly one meter long, and the achromat around twice that. Moreover, due to the heavy objective, most of that length ends up behind the pivot point. So even if you're sitting on a low stool, the pivot point needs to be really high when you're viewing (say) 60 degrees above the horizon. In practice, you end up needing a really tall, really heavy tripod for any refractor with a focal length much longer than a meter.

 

However, those disadvantages become very modest in small apertures. A really short refractor, like my 70-mm f/6.9, with its 480-mm focal length, works well on any half-decent tripod, and the variation in eyepiece height is easy to handle. Once the focal length gets up to 600 mm the eyepiece height becomes more of a problem, but it's still easy to accommodate with an adjustable-height chair, and you still can get away with a pretty modest tripod.

 

So, in short, if you want a scope with an aperture of 80 mm or less, a refractor is by far the most practical design unless you're really poor or need something ultraportable, and even at 100 mm the benefits of a refractor outweigh the downsides for many people. Once you get bigger than that, refractors start to become more of a specialty item.

 

Which then begs the question, why use a small-aperture scope? And the answers to that are obvious -- wide field of view, portability, and faster cooldown time.

Hi,

 

very well explained!

 

I would add a good refractor shows the most aesthetic image for me.
It's the cherries on the cake.

 

Andreas

[John Fitzgerald]

Two caveats:

 

If you are an extreme perfectionist to the point of OCD, 

or

You are not at least a bit mechanically inclined,

 

Then you probably should NOT own a telescope.

[JOEinCO]

....I wouldn't have the wide field views I get with a sub-$500 f/6 102mm apo....

....I'm unaware a 102 mm F/6 ED doublet available the US for under $500....

 

I'm curious to hear about this sub-$500 scope, too.

....When I bought my Meade Infinity 102mm it retailed for about $300. I bought it, used for $100.

 

No worries. But I was pretty sure a sub-$500 102mm APO was made of powdered unicorn horn. That Meade Infinity is not an APO.  

 

Clear Skies...! 

[Echolight]

My ST102 looks good in the living room, five feet from the back door. And is easy to carry out on the mount with one hand.

[Chad7531]

Dob. It has aperture and resolving power. Cooling or grab n go makes no difference to me, I intend to observe when my alarm goes off some 8 hours after taking it out. Would I subject a 3k refractor to this for views that aren’t even comparable? No. And my other mount is sitting there polar aligned too if I do want to grab my 6” reflector for 3.5* views or a quick look.

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Edited by Chad7531, 30 January 2023 - 09:00 PM.

[Vertigo]

Dob. It has aperture and resolving power. Cooling or grab n go makes no difference to me, I intend to observe when my alarm goes off some 8 hours after taking it out. Would I subject a 3k refractor to this for views that aren’t even comparable? No.

After the opening fever comes the sweetness.

 

Andreas

[Jon Isaacs]

 

Forgive my poor analogies, I meant no offence.
 
Likewise, I'm pretty oblivious to what the retail market is currently like, because I'm not shopping. When I bought my Meade Infinity 102mm it retailed for about $300. I bought it, used for $100.

 

No apology necessary, I was just curious to know of a 4 inch F/6 ED Doublet for under $500. As has been said, the AT-102ED for $549 is an unbelievable deal and the lowest price I have ever seen for a 4 inch ED.

I recently purchased a used Svbony 48P, it's a 90 mm F/5.5 achromat with a 2 speed rack and pinion focuser, a sliding dewshield, a metal thread on objective cover. New the go for $240-$290 depending whatever. I paid $150. It's the nicest looking fast achromat I've ever seen. The focuser is a little stiff but I handled heavy weights like the 31 mm Nagler quite nicely. It's a fun scope under dark skies 

 

One of these scopes is an WO 80 mm F/7 FPL-53 doublet. The other one is the Svbony achromat.

 

Ok.. I admit it, I like an attractive refractor..

 

 

Jon

[Victory Pete]

Two caveats:

 

If you are an extreme perfectionist to the point of OCD, 

or

You are not at least a bit mechanically inclined,

 

Then you probably should NOT own a telescope.

I am affirmative to #1 and negative to #2. I have a Tele Vue NP127is and an 8" EdgeHD that share an EQ6-R. Can you explain #1 please?

[John Fitzgerald]

I am affirmative to #1 and negative to #2. I have a Tele Vue NP127is and an 8" EdgeHD that share an EQ6-R. Can you explain #1 please?

If you are an extreme perfectionist to the point of OCD, you will not be pleased with, and will find fault with any telescope.  It will be a source of frustration and anxiety.

 

If you are not the least bit mechanically inclined, you may be unable to accomplish such tasks as routine collimation, focuser adjustments, mount adjustments, etc.  Again frustration, sending the scope to others for adjustment, possible shipping damage....

 

I see people on here time and time again, who seem so frustrated, that a telescope/mount is probably not for them.

Edited by John Fitzgerald, 30 January 2023 - 08:30 PM.

[GGK]

At star parties, on all CN boards and even talking to friends, they are all about buying the best refractor with the best glass.  Overall, I’m a newbie to this amazing hobby but have been here since 2019 but have been studying science/astrophysics forever.  

 

Is the main thing about refractors the wide field view and observing DSO and Astrophotography?  Because the aperture is so small on refractors and people are going crazy about 72mm, 90mm and 102mm scopes.  Anything above that is so expensive.  

 

An SCT or Dob gives so much aperture for planets and solar system objects but their narrow field of view is what the refractor fans are annoyed at?

 

(disclaimer:  I am considering buying a refractor to supplement my Celestron 9.25 and to possibly double mount it).

I'm a long time SCT user and purchased an AT60ED a while back to piggyback on my C9.25 and to use as a hiking and small travel scope.  It's opened up a whole new path of visual astronomy for me.  I had no idea what I was missing.

 

I started here:

 

 

But now use the scope by itself a lot more often:

 

 

I've found that I really like ultrawide field observing, especially from 4^o to the 7.4^o max capability of the 60mm.  My targets there are usually extra-large DSOs, moving groups, large star formations / asterisms, and large nebula rather than the smaller cataloged DSOs that I observe with my SCT.  It is truly a complimentary telescope with unique wide field capability. Most of my time spent with this scope is above 5^o TFoV, and I'm often just scanning the sky.  Sky brightness can impact the image when using large exit pupils in small scopes, so I might take the 60mm out in the morning rather than the evening to avoid a gibbous moon.

 

I use the AT60ED instead of my binoculars because it's more capable / flexible and makes observing a lot more fun for me. I optimize the view by changing exit pupil and TFoV.  Observing large star formations at very low power is more about getting the best exit pupil and background sky brightness with proper framing than having a specific magnification.  Yesterday I was in the Milky Way at 6.7^o with a 5.2mm exit pupil and saw a smaller area where I wanted more contrast, so dropped to 3.5^o with a 2.2mm exit pupil to make the image pop.  Doing that can often highlight asterisms that aren't easily seen otherwise. Putting an 8mm Ethos in the 60mm f/6 refractor gives 2.2^o with a 1.2mm exit pupil which can be quite interesting on bright clusters under dark skies.  

 

There is no doubt that the AT60ED is a small scope and struggles when you need a little more aperture, so for those targets, I take out the TV-85 or NP101is.  I rarely use magnifications more than 1.1 X aperture in my refractors unless I'm looking at double stars or the planets / moon.

 

I agree with all those above who promote the small size and grab and go utility of a small refractor.  The result for me has been significantly more outings.  These small scopes are so portable and easy that I'll even take them out for a short 30-minute session and just look between the clouds to see what's there.  The three refractors I have are different enough in capability that I keep them all, but if I kept only 2, I'd keep the NP101is for the flat field and larger aperture, and the AT60ED for the ultrawide field.

 

I like my AT60ED piggybacked on the SCT well enough, but set-up time is longer.  So, since I started using my AT60ED on its own, I only piggyback it when I have friends coming over so they can easily view an object fully framed first, and then close up.

 

Gary

[Philip Jodry]

Refractors are handy and comfortable, and sexy.