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Why your refractor and not the newt?

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#51 MortonH

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Posted 09 January 2021 - 08:19 PM

What are the real benefits of a refractor over a newt (I Y O) ? Is it just the portability issue?

The main benefit is that a refractor is a telescope while a newt is a small amphibious creature.  If you are referring to Isaac Newton's reflector design then you should write 'Newt'.


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#52 MortonH

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Posted 09 January 2021 - 08:27 PM

View from the back of scope.

For objects high in the sky the refractor eyepiece gets very low unless you have a very tall mount.  Assuming you don't need a ladder to reach the eyepiece a Newtonian is much more comfortable to look through.  I've never had a sore back or neck after a night observing with a Newt, but a night with a refractor or SCT...


Edited by MortonH, 09 January 2021 - 08:31 PM.

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#53 MortonH

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Posted 09 January 2021 - 08:37 PM

Up to five inches in aperture I prefer refractors over comparable light grasp reflectors because:

- They are always collimated properly

Really?  You've never seen a thread about miscollimated refractors on CN?


Edited by MortonH, 09 January 2021 - 08:43 PM.

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#54 KBHornblower

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Posted 09 January 2021 - 09:21 PM

I never though of newts as being apochromatic..... I only ever thought of apo/achro as a refractor thing.  I better read up.

If I were to be a semantics nerd, I would say that a Newtonian reflector is truly achromatic, at least at the prime focus.  The word "achromatic" literally means "without color", but for better or worse became established in refractor jargon as the term for the original crown-flint doublet that greatly reduces the chromatic aberration of a single lens but does not entirely eliminate it.  When triplets with improved color correction were invented, the inventors coined the word apochromatic to distinguish them from the doublets.  The word "apochromatic" literally means "away from color", which I do not see as describing any superiority over what "achromatic" literally means.


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#55 Ballyhoo

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Posted 09 January 2021 - 09:29 PM

No dust, no recoating the lens, no collimating, no coma or little, no secondary spikes, better contrast, punches slightly above its aperture, and chicks dig refractors....what more do you need!

"and no aperture." 

 

Sorry that was a low blow.  I love my fracs, but only for imaging and for observing pretty celestial objects.  



#56 russell23

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Posted 09 January 2021 - 10:28 PM

Well, since I have refractors and I also have Newtonians; and since I choose to use my refractors far more often than I choose to use my Newtonians, I suppose I should make a contribution to this thread:

 

It's not easy to pin down why I prefer using my refractors.  The simple (and rather meaningless) answer is: "Personal Preference."  But the likely followup would be: "Why?"

 

Well, it's easier for me to take my refractors outside and to bring them back inside.  So that may be a part of the situation.  On the other hand, back when I kept one of the Newtonians in a roll-off-roof observatory, the Newtonian tended to get used more often.  On the other hand (It's OK, I have two hands smile.gif )  I switched to my current refractor preference a few years prior to removing the Newtonian from the ROR observatory.  So . . .

 

I don't care much about being able to resolve closer doubles or to see smaller and fainter DSOs.  I can resolve "close enough" doubles and still see plenty of small, faint galaxies, etc. without having to use one of my Newtonians.  It doesn't matter to me if they're not the same doubles nor the same DSOs.  Similarly, I can see plenty of detailed, structured DSOs with either class of telescope.  So, I might as well choose one and enjoy all that I can see with it.

 

So why does my choice always end up being a refractor?  Hmmm . . . Well, it's easier, more intuitive, for me to point a refractor at an object (before looking through a finder) by sighting along the OTA.  After all, the eye is nearly always near the back of the OTA.  So that probably contributes to my preference.

 

What about planetary observation?  Well, from my location it would be a rare night that I would be able to use a magnification with one of my Newtonians that would not be practical for use with one of my refractors.  So, either telescope will work for planetary observation.  Besides, I'm not into this hobby to always see more.  I'm happy to see as much as I can when using whatever telescope I might choose to use.

 

That last sentence might the key for me.  The telescope and the level of detail, light-grasp, etc. are not that important to me.  I just want to make observations.  So what if someone else can see more with their 92-inch telescope?  That doesn't matter to me.  All that matters is what I can see with the telescope I'm using.

 

Am I making any progress here?

 

It's easier for me (during takeout, use, bring-in, and storage) to keep my refractor optics clean than it is to keep my Newtonian optics clean.  It's also easier to safely clean my refractor optics (if they were to ever need it!)  So this might be a factor in my preference.

 

I do prefer my generally "cleaner-looking" refractor views.  Yes, I have some CA with some (but not with all) of my refractors; but my Newtonians collect more light, so any light scatter (more of an issue with mirror optics) and diffraction effects are going to be more obvious to the eye when using a Newtonian.  I simply prefer my refractor views -- personal preference (again).

 

So it looks like, for me, the preference (for the refractor) tends to be related to:

 

     a) easier to take out and bring in

     b) easier to keep clean and to safely clean

     c) easier to direct toward targets of observation

     d) cleaner views

     e) My refractors show enough to satisfy my needs.

     f) The usual Newtonian advantages are of no importance to me.

     g) (not mentioned above) Cool down times for large mirrors -- not an issue.

     h) Oh, and I needn't check/adjust collimation

 

I'm sure there are other reasons that just aren't coming to mind right now.

 

But more seriously, for me, it's really just a matter of my own, personal, preference.  I gain more pleasure out of using my refractors.  And that's really the only reason that matters.

This sums up my feelings.  I no longer have a reflector.  Haven’t for years.


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#57 ShaulaB

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Posted 09 January 2021 - 10:38 PM

Grab and Go. For fun and giggles.

#58 vtornado

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Posted 09 January 2021 - 10:53 PM

There is a lot of dispute about whether Archimedes "death ray" was fact or fiction  -- There was a myth busters episode on this.

It was flagged as busted.  The boat go hot, but did not burst into flame.   However ... It may have blinded the crew and they ran the ships

aground.

 

Back on topic. I am getting old and it is cold where I live.   My fracs live on a mount in the it goes out of the house in a moments notice.

No cool down, no collimating.   It is ready right away.   Too much fidling and I have to go in because I'm cold.

I have a 120 f/5 for sweeping and big wide fields.   A 100 f/9 ed for medium power work.   When the weather turns

warm the reflectors start rolling out.


Edited by vtornado, 09 January 2021 - 10:54 PM.


#59 dan_1984

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Posted 10 January 2021 - 02:56 AM

"and no aperture." 

 

Sorry that was a low blow.  I love my fracs, but only for imaging and for observing pretty celestial objects.  

You simply need a bigger frac :) 


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#60 RadioAstronomer

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Posted 10 January 2021 - 03:48 AM

For me:

1) Aesthetic quality and sharpness of the image. I've looked through some large dobs with premium mirrors and sure, the image is close to that of an APO, but not quite there.

2) Durability. Refractors can last centuries if well taken care of. On the other hand reflecting mirrors need to be recoated every few decades. I'm sure somebody will say that my dob from 1981 still puts great images, yea ok, but those images are dimmer than they were in 1981 with new coatings.

3) Robustness: A refractor does not need to be collimated (unless you use it to play baseball).


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#61 Ihtegla Sar

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Posted 10 January 2021 - 04:40 AM

Durability--there are threads here on CN stating that mirrors need to be recoated every six years, and if you wait too long it not only dims the image but also can cause damage to the surface of the mirror.


Edited by Ihtegla Sar, 10 January 2021 - 08:53 PM.


#62 zirkel 2

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Posted 10 January 2021 - 05:10 AM

Hi,

- Easy to take out / transport / install: speed of implementation.
- Quick heating (for doublets): grab and go use.
- Closed tube: minimizes temperature changes.
- The lens is high above the ground: less sensitive to ground turbulence.
- No obstruction: + contrast and facilitates access to fine details.
- Little or no maintenance: use without maintenance constraints.
- No collimation to be done: stability of optical adjustments.
- Better light transmission (at equal diameter and magnification).
- Stitched and contrasted images: the contrast is as important as the diameter.
- Takes little space for storage.
- Intuitive tube pointing and orientation.
- Versatility of use: astronomy, landscape, animals.

Edited by zirkel 2, 10 January 2021 - 05:15 AM.


#63 Hesiod

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Posted 10 January 2021 - 05:23 AM

Archimedes may have used a mirror to cook his meal, but the "death ray" was a later myth (neither Polybius nor Livy reported their use. They however described several other war engines devised around the principle of the lever). The Roman fleet's failure to establish a tight blocakde was caused by the very same reasons who caused similar failures to previous attempts by Athenians and Carthaginians, namely the topography of Syracuse.

Archimedes' devices helped to repel an early seaborne assault with "sambucae" (a sort of big ladder carried by a couple of fastened warships allowing  the marines to reach the top of the walls)



#64 Rutilus

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Posted 10 January 2021 - 08:12 AM

Due to a medical condition I can no longer use a Newtonian reflector, they are now instruments of pure torture for me.

So no Newts for me now. However I still find my last mirror very useful everyday.

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#65 dan_1984

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Posted 10 January 2021 - 03:13 PM

"and no aperture." 

 

Sorry that was a low blow.  I love my fracs, but only for imaging and for observing pretty celestial objects.  

Aperture is only one part of the equation

Pros have to worry about more aperture cause they allways get high-end mechanical and optical stuff and place scopes in Chille

Amateurs should worry about quality above all else


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#66 mikeDnight

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Posted 10 January 2021 - 06:06 PM

For me refractors = contentment. And a good one packs a punch much greater than its aperture class. Personally I'd rather use a good 4" refractor over an 8" reflector for most purposes. 


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#67 MortonH

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Posted 10 January 2021 - 06:18 PM

Durability--there are threads here on CN stating that mirrors need to be recoated every six years, and if you wait too long it not only dims the image but also can cause irreparable damage to the surface of the mirror.

 

That's scaremongering.  Mirror coatings last a lot longer than six years unless you have weird contaminants getting on the glass (which would also get on a refractor lens).

 

An 8" mirror in need of recoating will still put up brighter images than a 4" refractor.  And it will still have twice the resolution.


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#68 MortonH

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Posted 10 January 2021 - 06:22 PM

For me refractors = contentment. And a good one packs a punch much greater than its aperture class. Personally I'd rather use a good 4" refractor over an 8" reflector for most purposes. 

Mike, what are the "most purposes" of which you speak?  On all but the brightest deep sky objects an 8" reflector will walk all over a 4" refractor.  Not saying the 4" frac wouldn't be nice but when I had one at the same time as my C8 it was the C8 that got used almost all the time.


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#69 stevew

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Posted 10 January 2021 - 08:00 PM

In large reflectors M13 always ruins my night vision.

Reflectors also suffer from optical fatigue from too much light gathering. And don't get me started on Photon Splatter...


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#70 Ihtegla Sar

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Posted 10 January 2021 - 08:42 PM

That's scaremongering.  Mirror coatings last a lot longer than six years unless you have weird contaminants getting on the glass (which would also get on a refractor lens).

 

An 8" mirror in need of recoating will still put up brighter images than a 4" refractor.  And it will still have twice the resolution.

Refractor coatings typically last a lifetime but mirrors need periodic recoating.  "We think of a mirror coating as a consumable."  From the linked post linked, mirror coatings can last from one year to ten years or more depending primarily on local atmospheric conditions and how often they are used.  

 

Ten years seems to be about the average but two posters in this thread from last year reported needing a recoating after six years and one reported damage to the surface of the mirror requiring the mirror to be re-polished in addition to a recoat that resulted merely from the alkaline air in southern California, which I would not consider a "weird contaminate."  Plenty of refractor coatings last a lifetime in southern California.



#71 Ihtegla Sar

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Posted 10 January 2021 - 08:51 PM

Mike, what are the "most purposes" of which you speak?  On all but the brightest deep sky objects an 8" reflector will walk all over a 4" refractor.  Not saying the 4" frac wouldn't be nice but when I had one at the same time as my C8 it was the C8 that got used almost all the time.

Depends a lot on where you live, and what the seeing and weather conditions are like.  My C8 rarely comes out of its box and I really should sell it because it is routinely outperformed by my 4" refractors due to issues with seeing and thermal equilibrium.  I live under the jet stream where seeing typically limits magnification to about 200x or less and where temperatures drop continually throughout the night so the C8 has a lot of trouble reaching equilibrium, and even when it does, I cannot take full advantage of the larger aperture due to magnification being limited by the seeing. 

 

In theory,  the C8 is capable of outperforming my 4" refractor, but in practice that only happens when seeing and temperatures cooperate, so the 4" refractor puts up better images on most nights, at least on double stars, planets and the moon which are my primary targets. 


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#72 Mitrovarr

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Posted 10 January 2021 - 09:09 PM

Mirror coatings last a lot longer than 10 years in terms of functionality. You might want to recoat every 10 years for optimal performance, but many mirrors that are 40-50 years old are still usable.


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#73 MortonH

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Posted 10 January 2021 - 09:09 PM

Depends a lot on where you live, and what the seeing and weather conditions are like.  My C8 rarely comes out of its box and I really should sell it because it is routinely outperformed by my 4" refractors due to issues with seeing and thermal equilibrium.  I live under the jet stream where seeing typically limits magnification to about 200x or less and where temperatures drop continually throughout the night so the C8 has a lot of trouble reaching equilibrium, and even when it does, I cannot take full advantage of the larger aperture due to magnification being limited by the seeing. 

 

In theory,  the C8 is capable of outperforming my 4" refractor, but in practice that only happens when seeing and temperatures cooperate, so the 4" refractor puts up better images on most nights, at least on double stars, planets and the moon which are my primary targets. 

Fair enough, but before you give up on the C8 have a search for various threads on CN about solving thermal issues in SCTs and Maks by insulating instead of cooling them.

 

I love looking at globulars and planetary nebulae as they are relatively unaffected by light pollution but to resolve then I need more than 4".  However, I agree that on planets I prefer the image from the refractor a lot of the time.


Edited by MortonH, 10 January 2021 - 09:15 PM.

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#74 Bomber Bob

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Posted 10 January 2021 - 10:23 PM

As I posted in another Frac vs. Newt thread (more than a few of those on CN!!):  Most nights, why do I choose a Refractor rather than a Reflector?  The Convenience Factor.  My work night sessions are short, and I'm more likely to take out a small scope vs. a Big Scope.  My mitigation is to make deploying a Big Scope easier:  Mounts stored in the shed.  Casters on the heaviest EQs.  Multi-scope / common mounts with rings & dovetails for quick & easy swaps.  It can be done.  My only limitation for now is cradle height.  But I have everything settled to where using my 8" Newt is no harder than my 4" refractors.  Scope selection is back to Object Type and Seeing, as it should be... 


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#75 teashea

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Posted 10 January 2021 - 10:49 PM

For objects high in the sky the refractor eyepiece gets very low unless you have a very tall mount.  Assuming you don't need a ladder to reach the eyepiece a Newtonian is much more comfortable to look through.  I've never had a sore back or neck after a night observing with a Newt, but a night with a refractor or SCT...

I find using a Newt is much more cumbersome and awkward that using a refractor.


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