Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

reflector vs. refractor

This topic has been archived. This means that you cannot reply to this topic.
133 replies to this topic

#51 jrcrilly

jrcrilly

    Refractor wienie no more

  • *****
  • Administrators
  • Posts: 35206
  • Joined: 30 Apr 2003

Posted 02 February 2004 - 10:47 PM

there definitely is a difference in views, besides the obvious things you can point out and put your finger on.


Hi, Erik.

Oh, yes. The subjective preference for one sort of view over another is a personal thing and, to me, beyond argument. I like wide starfield views in a fast refractor, planets in a slow reflector, and nebulae or galaxies in the biggest scope I can get my hands on, whatever the type. :roflmao:

#52 Charles

Charles

    Skylab

  • -----
  • Posts: 4111
  • Joined: 12 Jun 2003

Posted 02 February 2004 - 10:55 PM

Hey John, I love stirring things up for a little fun, but it seems most still want to read between the lines. My statement was not that some reflectors are better than APOs but that a inexpensive reflector, which no one would give me a price on will never out perform a APO of the same aperture. Comparing a Cannon to a 4 inch smaller scope is not a comparison and if the statement was true then TAK would never need to build 9,000 dollar Astrographs. High quality optics cost a lot of money whether it is ED glass or Flourite, or hyperbolic mirrors. A high quality reflector will cost the same if not more than a APO and the statement that has been raised that less expensive reflectors can out perform a APO in my opinion is not a accurate statement.

It's like comparing a Volkswagen to a Cadillac, they will both will get you from point A to point B, but which one will give you the better ride and comfort!

I want to hear someone in this thread try and state a less expensive reflector can out perform a same size aperture TAK reflector. That would be a more realisitic comparison than what seems to be going on in this thread by some.

Charles

#53 erik

erik

    telescope surgeon

  • *****
  • topic starter
  • Posts: 24858
  • Joined: 30 Jan 2004

Posted 02 February 2004 - 11:08 PM

charles, no, an inexpensive reflector of the same size can't outperform the same size refractor, but if you add the diameter of the secondary obstruction into the equation, so that both scopes have the same effective aperture,then the reflector would possibly provide as good or better views, depending obviously, on a whole host of things, such as the users preferences, and whether we're talking about a stock or modified newt. there's no doubt that out of the box, the APO would win, but with a couple hundred dollars in modifications, i believe the newt would be as good, and show images that i would find more pleasing.-erik wilcox

#54 Barry Fernelius

Barry Fernelius

    Viking 1

  • *****
  • Posts: 690
  • Joined: 28 Jan 2004

Posted 02 February 2004 - 11:29 PM

Dude wrote:
---
Besides ALL the experts, etc., and I were talking mostly about the image quality being better in the smaller scope which we`ve found to be the case at numerous places around the country as explained above.
---

I have a simple question for you Dude: have you ever looked through a either a Portaball or a Starmaster with a Zambuto mirror on a night of good seeing?

#55 Guest_**DONOTDELETE**_*

Guest_**DONOTDELETE**_*
  • -----

Posted 02 February 2004 - 11:37 PM

Hello,

[quote name="erik"] and due to simpler and easier to make design of a newt, there are less inherent things to go wrong. [/quote]

With all due respect, I disagree with this. So do experts such as Dickinson, Dyer, etc.

From Dickinson and Dyer`s, "The Backyard Astronomer`s Guide",

"Because of the unobstructed design, refractors have, theoretically, the least abberations of any optical system."

and,

"It is easier to manufacture a high-quality surface on a lens than it is on a mirror. Therefore, the intrinsic optical quality is usually superior to that of the other optical designs."

Dickinson and Dyer listed these two things as just two of the many optical advantages of refractors!

Then there`s this from, "The Amateur Astronomer`s Handbook.",

"A refractor is undoubtedly more effective than a reflector of equal size; and it is a fact that more reflectors than refractors turn out to be optically defective."

[quote] newts can suffer problems, like coma in faster focal ratios, and they need to be collimated regularly, but these issues are a lot easier to correct, or in the case of coma, to live with.i'd rather notice a little coma on the edge of the FOV,than a bright purple halo that fuses double stars together. [/quote]

I respectfully disagree with all this also. I and most of our club members find it easier to live with what few minor issues refractors may have. The fact that they`re almost maintenance-free especially compared to newts has a lot to do with this. Here`s Dickinson and Dyer from, "The Backyard Astronomer`s Guide", again,

"Color-correction of the crown/flint doublet lens is excellent in f/10-f/11 achromats, and the telescope is portable in 80mm-90mm apertures, and they`re durable and virtually maintenance-free for decades."

As for coma and false color, our club`s tested our members and those who`ve attended our star parties on these two issues. We found that most people found the little seaguls flying around the edge of the fov much more objectionable than false color in our longer-focus achromats which many people didn`t even see and needed it pointed out to them. Even then, they barely noticed it and, therefore, found it much less objectionable than coma. And yes - all the newts were perfectly collimated and of good quality.

False color is quite insignificant in a longer-focus achromat and, for ALL practical purposes, not an issue at all in Apo refractors. And the longer that focal length is, the more insignificant false color becomes in longer-focus achromats! :D


[quote] you can spend another $75 on a filter that blocks some of that [/quote]

Nobody in our club even uses these in their longer focus achromats since the color-correction is so good and one has to hunt down the false color to even see it!

[quote] except the very top of the line models, suffer from chromatic abberation to some extent. [/quote]

...usually at levels that are either virtually impossible to see like in good Apos or almost impossible to see like in good longer-focus achromats.

[quote] an inexpensive, well collimated newt will provide nice views right out of the box [/quote]

...except that many newts aren`t collimated right out of the box...

[quote] and with a few modifications, it's easy to make them even better. [/quote]

...and I`m glad to see that this is exactly what you did! Isn`t it??? :D :cool: :D

[quote] just my take on things. [/quote]

That`s quite alright! :D :cool: :D This is America and you`re most certainly entitled to your opinions, etc. :D :cool: :D

Clear, STEADY Skies! :D





#56 Charles

Charles

    Skylab

  • -----
  • Posts: 4111
  • Joined: 12 Jun 2003

Posted 02 February 2004 - 11:50 PM

Thanks Eric, but I'm not trying to win on the basis of APOs being better. I'm just trying to get everyone to compare the same apples against apples. IF someone wants to believe their scope is better than an APO thats fine. I'm a firm believer that Reflectors can out perform a APO only if the reflector has the same quality optics(Mirrors) as the APO has. In which case you are paying more than you would for the APO to get a larger aperture. So the statement that less money can out perform the APO is not quite a true statement. What is true is you can buy more aperture for your money in a reflector if the quality is equal. You will pay slighlty less for the reflector per inch of aperture than you would for the APO. Comparing TAK prices alone a 5" APO will cost you roughly 5 grand and a 10 inch Epsilon will cost you 9 grand. That equates to the refractor costing about 1,000 per inch and the reflector costing about 900.00 an inch. The cheapest TAK reflector is their 212 which cost 4500 at 8 inches. That would be a price of 560 per inch of aperture. Everyone of these scopes will probably easily out perform my 5" APO but the cheapest, CN 212, is roughly 600 dollars less than what I paid for my APO and I'm not really sure the 8" would really be a huge improvement over my 5" APO for the hassles of weight, colimation and size. My only point is there is not this huge decrease in cost from a APO to high quality reflector. Also in the long run the mirrors will require re-coating long before my optics would, if ever, need re-coating. That over a life time, might equalize the price of the two comparisons.

Charles

#57 erik

erik

    telescope surgeon

  • *****
  • topic starter
  • Posts: 24858
  • Joined: 30 Jan 2004

Posted 03 February 2004 - 01:29 AM

charles and dude, i respectfully disagree with you on several points.first, i'm sure you could spend $4500 for a tak 8 inch reflector, but i think that you can get a fine newt with a great mirror for A LOT less than that. even the big 3 manufacturers turn out some good mirrors these days, and smaller guys like discovery make some great mirrors. i read an article where someone replaced there mirrors with custom ground mirrors- i cant remember the exact specs, but they were close to perfect and he could almost never tell the difference between the two.and as for modifications, yes i have modified my scope quite a bit, but i still have less than $2000 into the whole thing, including the mount, which is substantially less than one of your OTA's cost.like i said earlier, on cloudy nights article section, the writer describes not being able to stand the view in his 4 inch apo after making a $20 modification to his newt(multi aperture mask) so i'm not the only one that thinks that newts can perform better. and mirrors need to be recoated how often? i've never had to do it yet.flourite also isn't forever from what i've read, especially in cold temps.and no refractor owners ever mention comparing deep sky views to a newt.come on, cant you refractor guys admit that you think refractors are pretty, and you just like owning a $9000 telescope that you can carry with one hand?

#58 eric moerman

eric moerman

    Ranger 4

  • -----
  • Posts: 309
  • Joined: 08 Nov 2003

Posted 03 February 2004 - 04:21 AM

Erik,

Im pretty sure that there will be a difference between a 4500Tak and a telescope from the bigger names.
Im not saying these are bad buth they just dont perform the way a trully high quality mirror will do.I have read here a couple of times already that people are using of axis mass on there reflector.
I never do that.if seeing is so bad that i cant use the magnification to make the most of my mirror at full aparture
i simply dont look at the planets.its not so ofthen that i cant use at least 400*,even if the seeing is less good and the image is not sharp most of the time there are always small periods of time that the seing becomes stabel and you get a perfect image.Thats when you see the small details that only bigger scopes will show you.

Eric


#59 jrcrilly

jrcrilly

    Refractor wienie no more

  • *****
  • Administrators
  • Posts: 35206
  • Joined: 30 Apr 2003

Posted 03 February 2004 - 05:26 AM

Hey John, I love stirring things up for a little fun, but it seems most still want to read between the lines.


Hi, Charles!

I'm getting really tired of this weather. It's about time to start using the gear instead of talking about it.

I agree with your viewpoint in most ways. There are some subtexts in this discussion that always seem to enter this sort of comparo.

I think most of us agree that at some point optics are good enough that further improvement won't be seen by visual users. After that point the benefits are pride of ownership or imaging potential. Of course, along with that last bit of perfection usually comes mechanical sophistication of a high order, and a serious price tag. I'm not gonna be in the market myself for Mewlons or TOA's; for me the sweet spot in APO's is the 4" $2000 class. Smaller is too small; larger or better is too expensive. I can use such a telescope just about enough to try to keep one around. If I were serious about imaging I'm sure that would change.

I like the concept (again, for visual use) of plenty of aperture in the field. This excludes refractors for me. Even a 7" APO is too heavy, too demanding of a mount, and too expensive for me to drag out into the field. I used to use SCT's exclusively for that but over 11" they, too, get cumbersome. I think I've found my answer; a conventional Newt with the biggest, highest-quality mirror I'm willing to pay for in the best truss dob housing I'm willing to buy. It'll give me excellent optics and will break down for transport. I can get aperture way beyond any refractor I'd consider with very little optical compromise.

Like the Jesus thread elsewhere, what works for me isn't necessarily what works for everyone. You would find a big Dob useless for your primary application; I'd find a TAO to be both overkill and too small for my field use. Of course I still maintain that a fairly large SCT is the Jack of all trades and the best allaround bang for the buck for observatory visual use. Also remember, I LIKE refractors. I still have a very sweet Vixen 120NA and I know a TV 4" APO will be in the arsenal soon for my limited imaging projects - they just aren't a good enough fit for me to justify giving up my other gear to buy a really top-end one.

#60 Rhadamantys

Rhadamantys

    Mariner 2

  • -----
  • Posts: 214
  • Joined: 25 Apr 2003

Posted 03 February 2004 - 06:13 AM

It is true that from a technical point of view, an unobstructed telescope is better than an obstructed one, at least if the apperture and optical performances are identical.

However, to judge the efficiency of a design, I also take money into account. It is widely known among serious observers that with 25% central obstruction, a reflector will perform just as well as a 8" unobstructed refractor, at least on the planets.

Price of a 8" f/9 APO objective only (from APM): US$ 16,900

Price of a 10" f/6 high quality mirror (L/16 PtV or better, superpolished, etc.) from Astro-Telescope: €1,850 (US$ 2,308)

When price is factored in and all the rest being equal (mount and OTA), I think that the efficiency of the reflector is pretty easy to understand.

Don't get me wrong, APOs are indeed superb telescopes, especially efficient as small portable telescopes, but... unless you are also a wide field imager (an area where APOs are also very good), simply no longer very efficient above 4" or 5" of apperture: there are definitly cheaper, more efficient solutions, especially if visual work is only considered. The best planetary pictures I have seen so far have been made using reflectors in the 10" - 40" range. For such a task, even the best 6" APO remains no match for such a telescope. For a serious semi-wide field imager (1°-1.5° FOV), a 12" or larger Newtonian or Cassegrain with a Wynne corrector is a much more satisfying solution.

Everybody is free to spend his money as he wishes. I simply lay the stress on efficiency more than other people usually do.

Vincent

#61 LivingNDixie

LivingNDixie

    TSP Chowhound

  • *****
  • Moderators
  • Posts: 19250
  • Joined: 23 Apr 2003

Posted 03 February 2004 - 08:19 AM

Charles,

You make a good point, where does the good reflectors start... Well in my oppion that start with the Discovery PDHQ line. Optically and mechanically they are a good notch or two above the imports comming from the orient.

Secondly lets not forget one thing when it comes to scopes. The experience of the observer. An experienced observer knows how to eek about every bit of performance from his/her scope. I have friends that see things in their homemade 8 inch dobs that I don't see in their scopes (or mine). A well trained eye makes up for some of the lower performance....

One last thing, if I were to consider getting into astrophotography I would prolly save the money and buy a APO when I could afford it vs buying an SCT...If your thinking about picture taking a APO is pretty hard to beat.

LivingNDixie

#62 Jarad

Jarad

    Fly Me to the Moon

  • *****
  • Posts: 6393
  • Joined: 28 Apr 2003

Posted 03 February 2004 - 09:25 AM

Charles wats to compare high-end reflectors to high-end refractors. I consider Starmaster telescopes to be pretty much the top end of reflectors with Zambuto mirrors. I know, there are other excellent mirror makers (Swayze, Pegasus, Royce, etc.) and other excellent scope makers (Obsession, Portaball, Nightsky, etc.) but I am going to use Starmaster's prices for now and the other high-end ones will fall into a similar range, or slightly less depending on options.

Someone else posted a price for an 8" refractor of $16,900. That seems on the high end, but I doubt you will find one for under $10,000 anywhere. I also think that was OTA only, you still need a mount....

Starmaster sells a 14.5" reflector for $4895. You can upgrade that with GOTO tracking, Feathertouch focuser, secondary dew heater, transport handles, etc. A fully loaded 14.5" with all the options will cost $8310. An 18" fully loaded will cost $9810. A 24" fully loaded will cost $15410, getting close to the 8" refractor. So for the same money as the 8" refractor, you can get a 24" high quality reflector with GOTO and tracking, dew remover, etc. And I don't think the price for the reflector included a mount, which will add another $5000-$6000.

These high-end reflectors are simply outstanding. The Zambuto mirrors are usually close to 1/20th wave, and VERY smooth. The scopes are well desgined, well baffled, open cell for quick cooling, smooth movement, Feathertouch focuser, etc. There just isn't much to criticise as far as optical performance. The only real downside to big reflectors is, well, they are BIG. If you have the vehicle to transport them, and 1 other person to help setup in the largest sizes (I can set up an 18" by myself, but the 24" mirror cell gets a bit heavy....), they will certainly beat an 8" refractor. Even the 14.5" will beat an 8" refractor on everything except wide fields and photography. And the 14.5" isn't that big, and is probably more portable than an 8" refractor.

So, I still maintain that in terms of performance per dollar, reflectors win. Even when you look at high end reflectors. In terms of performance per inch, refractors win, but you pay for the privilege. In small sizes, refractors have the edge in performance per unit of portability (hard to define, but you know what I mean), although that switches to reflectors in larger sizes. For wide field and/or photographic use, refractors generally win (reflectors have to be optimized for photography with things like larger secondaries, which makes them not as good for visual use).

Jarad


#63 LivingNDixie

LivingNDixie

    TSP Chowhound

  • *****
  • Moderators
  • Posts: 19250
  • Joined: 23 Apr 2003

Posted 03 February 2004 - 09:29 AM

Jarad,

I couldn't haven't said it any better and I don't think I can add anything... Excellant

LivingNDixie

#64 Rhadamantys

Rhadamantys

    Mariner 2

  • -----
  • Posts: 214
  • Joined: 25 Apr 2003

Posted 03 February 2004 - 09:43 AM

$ 16,900 is the price of the APO objective: you still have to build/buy the OTA! That's why I compared it to a 10" mirror of prime optical quality.

What more and more people are doing right now in France, is to buy those chinese 8" or 10" f/5 or f/6 Newtonians, play with them for some time, then have the primary mirror refigured to an exceptional quality for around €1,000 (US$ 1,250) with enhanced reflective coatings. They perhaps add a better focuser and tweak the spider a little bit. After that treatment on a 8" reflector with 20% central obstruction, a 6" APO can no longer match it for visual work.

#65 erik

erik

    telescope surgeon

  • *****
  • topic starter
  • Posts: 24858
  • Joined: 30 Jan 2004

Posted 03 February 2004 - 11:02 AM

rhadamantys, yes,thats basically what i did. i bought the orion newt because i liked the steel tube, and the cardboard discovery tubes,(even though they're much nicer than the meade sonotubes), just weigh too much. one of the first things i did was replace the plate glass mirrors with discovery pyrex mirrors.although i can see a slight difference in the star test between the chinese made orion and the discovery, visually there's really not much, if any difference, and the discovery mirror is figurerd very well. the main difference i can see is the pyrex takes a lot less time to reach thermal equilibrium. even with a drastic temp change, it rarely takes more than an hour to cool down if i'm running the fan, wheras the original mirror could take an hour and a half to completely cool down. i think that it's important to realize that sometimes expensive improvments can yield small gains, because beginners should know that they dont have to spend thousands of dollars to get a well performing instrument.(unless they want an APO refractor) and definitely, for visual work, i agree, it would take a 7 inch APO to match the views in a modified 8 inch newt.maybe for astrophotography you'd want the APO, but i've seen some nice pix taken with newts too.(after all, the hubble IS a reflector)and coma isn't an issue in my f/6 scope, i had an f/4 that had coma but in my 8 inch f/6 it's only slightly visible on the VERY edge of the field in a 2 inch eyepiece. otherwise, there's no difference in the center or edge of the FOV. the whole FOV is the sweet spot.

#66 Jarad

Jarad

    Fly Me to the Moon

  • *****
  • Posts: 6393
  • Joined: 28 Apr 2003

Posted 03 February 2004 - 11:36 AM

Sorry, Rhadamantys - your post was on the previous page so I couldn't flip back and forth while I was typing. That tilts it even more towards the reflector.

Jarad


#67 Barry Fernelius

Barry Fernelius

    Viking 1

  • *****
  • Posts: 690
  • Joined: 28 Jan 2004

Posted 03 February 2004 - 12:30 PM

Since we've all gotten to the point where we're talking at each other rather than to each other, I'll make a final observation, and anyone else who wishes to speak is free to have the last word.

First, Charles has been clearly stating that when one compares a reflector and a refractor of equal aperture and equal optical quality, the refractor will win. I heartily agree.

Some have claimed that a mass-marketed reflector (Like a 10" Orion Dob) will outperform a much more expensive refractor like a 6" AP. Although the performance of the mass-marketed reflector is a good value for the money, my experience is that the refractor still has an edge in this situation. Like Charles, I say that the optics have to be higher quality for a reflector to compete with a refractor.

I also concede that refractors are better telescopes for some situations. I've seen firsthand that refractors provide outstanding wide-field views that simply cannot be duplicated with a large reflector. Refractors do well on bright objects like the planets and the moon. High quality refractors make great camera lenses, if imaging is your thing. Also, if you aren't the type of person who wants to hassle with collimation and cool-down time, a high quality refractor is an outstanding choice for the discerning amateur astronomer. (In fact, I'd love to go observing with Charles some time. Between the two of us, we have equipment that's great for almost any observing condition!)

However, for most visual astronomy tasks, high-quality aperture rules. Charles said that high quality reflectors are more expensive than high quality refractors. I say that there are high quality reflectors available (Starmaster, Mag1 Portaball, TelePort, PlettStone) with excellent mirrors that dollar-for-dollar provide better planetary and deep-sky views than refractors.

Take a look at all of the large observatories that have been built over the past 60 years or so, and you'll see a lot of large reflectors. Ask yourself the question, "Why didn't they build a bunch of large refractors?"

Finally, I'd recommend that the best (and most fun!) way to figure all of this out is to go to some dark sky sites under clear steady skies, and look through a bunch of telescopes. If the seeing conditions are good, make sure that you make some critical observations with reflectors made with Swayze, Zambuto, Royce, Mark Harry, (and so on), mirrors. Then, under those same conditions, take a look through high quality refractors from Takahashi, Astrophysics, TMB, (you know the drill). After this exercise, I decided to own a 12.5" f5 Mag1 Portaball.

Is this the only valid choice? Absolutely not! Set all of the books and opinions aside, go do your own work, and make your own decision.

#68 Guest_**DONOTDELETE**_*

Guest_**DONOTDELETE**_*
  • -----

Posted 03 February 2004 - 12:58 PM

Hello All,

It`s just too bad that all that extra aperture that a Newt can get you for the same money goes to waste most of the time in most places.

According to Dickinson, Dyer, experts, etc., ALL scopes are limited to 300x or less mag. and 1-3 arc secs. resolution on most nights in most places.

For ex., this means that most of the time in most places, a 5" Apo will show just as much planetary detail, etc., as larger newts including the ones mentioned above, but with better contrast, sharpness, clearity, etc., (much better in a lot of cases.). In other words, a 5" apo will be reaching it`s full potential on even several of these nights, (which helps to provide owners with their money`s worth throughout the yrs. since the scope`s reaching it`s full potential most of the time like it was intended to unlike larger newts), while larger newts won`t including many of the larger ones mentioned above which won`t even come close most of the time in most places.

And I know that on such nights of bad seeing, there`s rare, brief moments of good seeing. But not everyone has the patience, etc., or wants to look and wait for such rare, brief moments which may even occur while one`s resting their eyes, etc. Just like them, I`d much rather be looking at other objects such as dso`s or sketching, etc.

On those quite rare nights of excellent seeing, (we only had one such night around here last yr.), the larger newts will strut their stuff. But I`d much rather be looking at objects with good contrast, sharpness, clearity, etc., with the same amount of planetary detail the vast majority of the time.

Of course, these are just some of my preferences, etc. Yours may vary depending on several different factors.

Btw, I agree completely with ALL the excellent points that Charles brought up. :D :cool: even if others haven`t gotten them yet. ;) :D

Here`s another question to add to the one Charles posed several posts back. We all know that a 6" Apo and a good, well-collimated 8" newt will provide around the same planetary performance and the 8" newt probably will show a few more faint fuzzies in a perfect world which we, unfortunately, don`t live in. But with a FULL 2" more of aperture, much greater light-gathering power, much better resolution, etc., etc., etc., why is the 8" newt ONLY tied with the 6" refractor?! With ALL such advantages, the 8" newt should be stomping all over the 6" refractor! But it isn`t. Why do you think that`s so?! I`ll tell you why! It`s what I as well as others have been trying to say throughout this thread. Generally, it`s ALL because of the superior optical design, etc., of refractors in amateur sizes!!!

And I know people will try to bring money back into this discussion despite the fact it`s not even a telescope part and, therefore, irrelevant to ALL the different designs as mentioned already in this thread. But since there`s still some who will disagree with this, (as if money really is a telescope part ;) ), please also keep this in mind then. One can get most of their money back should they decide to sell their Apo. Because of this, often times Apo owners lose less money in the long run than cheap, etc., newt owners!

Hope ALL this Helps. :D

Clear, STEADY Skies!


#69 Jarad

Jarad

    Fly Me to the Moon

  • *****
  • Posts: 6393
  • Joined: 28 Apr 2003

Posted 03 February 2004 - 01:40 PM

Dude -

The aperture doesn't go to waste. If you are limited to 250x-300x by seeing (which is a reasonable number for most places), and you compare a 6" refactor to say a 14.5" high quality newt, they will both show the same level of detail on planets (both limited by seeing rather than aperture). The newt will have a brighter image, and will occasionally show more detail if the seeing steadies up for a moment. At no time will the newt show less detail than the refractor. Under the same conditions, the newt will clobber the refractor on deepsky objects, which don't need high magnification and do need lots of light gathering (and you said you'd rather spend the time looking at DSO's than waiting for moments of excellent seeing, exactly where the newt has the biggest advantage).

As to why the 8" newt can only at best equal the 6" refractor, I think everyone here agrees that refractors are the best in terms of performance per inch of aperture. The secondary causes diffraction, with the general rule of humb that a reflector can roughly equal a refractor of D-d, where D is the primary diameter and d the secondary minor axis (this is just an approximation, and assumes equal quality).

As to money, no it's not a telescope part, but it is relevant to what scope you can get. And high quality newt's hold their value quite well. Look in Astromart for Obsession, Portaball, and Starmaster scopes - they usually sell for around 80% or so of the new price, similar to high quality refractors. Cheap chinese refractors tend to go for closer to 50% of the new price. The key to holding value is quality, not type.

Finally, I LIKE refractors. I have an ED-80, which is a great little scope. If I was into imaging, I'd be getting something like a Televue NP-127, or a TOA 130 like Charles. Refractors are very good at what they do best, but they are limited to small sizes primarily by price. Newts are not as good per inch, but they have a much higher upper size limit, and there are smoe things that just require aperture. Both are avaialble with high quality (which is important, but doesn't distinguish between the two).

Jarad




#70 jrcrilly

jrcrilly

    Refractor wienie no more

  • *****
  • Administrators
  • Posts: 35206
  • Joined: 30 Apr 2003

Posted 03 February 2004 - 01:56 PM

Hello All,

It`s just too bad that all that extra aperture that a Newt can get you for the same money goes to waste most of the time in most places.


Hi, Dude.

You are the only person I've ever heard say something like that except on someplace like SAA.

It's not true for me in a couple of ways. For thing I can count on a large reflector going about three magnitudes deeper than a 5" APO. It's never wasted here except when weather makes viewing impossible.

#71 Guest_**DONOTDELETE**_*

Guest_**DONOTDELETE**_*
  • -----

Posted 03 February 2004 - 05:08 PM

Hello Guys, :D

Ok. But please don`t misunderstand. I know that the extra aperture isn`t wasted when it comes to dso`s, etc. I thought my statement about viewing dso`s, etc., on bad nights of seeing made this clear.

As for planets, I simply meant that the extra aperture is wasted during bad seeing, outside those rare, brief moments of good seeing and rare nights of good seeing. I thought my explanation of my preferences, etc., made this clear also.

with the general rule of humb that a reflector can roughly equal a refractor of D-d, where D is the primary diameter and d the secondary minor axis (this is just an approximation, and assumes equal quality).


I agree completely and even posted a version of this earlier in this thread along with several links to sites which explain Modulation Transfer Functions in detail.

And high quality newt's hold their value quite well.


I also agree with this. I`m sure that the high quality newts do just fine as you describe.

My Apologies for any misunderstandings; :D

Hope this Helps to clear things up, (especially the skies overhead :cool: ;) :D),

Clear, STEADY Skies!

#72 erik

erik

    telescope surgeon

  • *****
  • topic starter
  • Posts: 24858
  • Joined: 30 Jan 2004

Posted 03 February 2004 - 08:21 PM

hey all, as john brought up earlier and i reiterated, the best scope is the one that you like.some people like newts,some refractors,some SCT's. i'm sure there's probably someone that likes a 60mm tasco that has a plastic lens(a lovely xmas present when i was about 11).i like newts because they're more versatile. as jarad said, if the seeing is bad you can look at DSO's, after all there's thousands of them, and only a few planets. i think we can all agree that aperture is never wasted on DSO's.i like refractors to, i've thought about getting an ED-80, but it's just small for MY tastes. i recognize that it's a great scope, probably one of the best values out there right now, but it's not for me. now if orion comes out with a 5" or 6" OTA for $700, then i'd get one. as for now, i use my 120mm short tube achromat when i'm traveling or just want to view for 30 minutes. it's an all right little scope, but i certainly notice all of its shortcomings, and i never take it out if i have a choice between the two.even as much as like my 8- inch newt, i know at some point, i'm going to get a 16 inch newt, because i always want to see MORE. if 4 inches is all you need to be happy, more power to you! as for me, i want aperture, and i dont want to spend a fortune and waste 2 years of my life on a waiting list to obtain it.

#73 Charles

Charles

    Skylab

  • -----
  • Posts: 4111
  • Joined: 12 Jun 2003

Posted 03 February 2004 - 08:49 PM

I just love this thread. Barry and John are the only two that seem to understand what I'm trying to say and that is compare Reflectors with reflectors, not with refractors.

Charles

#74 erik

erik

    telescope surgeon

  • *****
  • topic starter
  • Posts: 24858
  • Joined: 30 Jan 2004

Posted 03 February 2004 - 08:57 PM

charles, okay but this thread is called "reflector vs. refractor" , not reflector vs. reflector

#75 Relativist

Relativist

    Cosmos

  • *****
  • Posts: 8143
  • Joined: 11 Oct 2003

Posted 03 February 2004 - 10:06 PM

I just went back and read the original question, so far I think the answer is no, he is not missing anything, the reason people like refractors is for other stuff (size, astrophotography, etc.), and has little to do with the veiw one gets. All I know is, I will have ~ $500 to spend on a scope next month, and I'm getting a 10" dob, and, if I had $1000, I'd get a 12", if I had $2000 I'd get a 14", if I had enough for a folded 20"+ scope I'd get that. (don't want to climb ladders)


......Curtis


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics