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What do you think is the difference between a good and a great refractor?

Optics Refractor Lens Making
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#51 Kunama

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Posted 24 September 2021 - 06:03 PM

Seriously now,  to me a great refractor is one that gives its owner satisfaction of ownership.  There are far too many different requirements by owners for any one scope to fill everyone’s needs.  A FOA60 is a great refractor to me but an unwanted toy to others…

 

For me a good compromise is the TOA130NFB… Not too big, not too small, not too heavy, decent optics, not too expensive….

a Goldilocks scope bow.gif


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#52 PKDfan

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Posted 24 September 2021 - 07:18 PM

The difference is a lot of what has been already mentioned but I will add my own small wrinkle in the dollars spent to value received discussion.

I have a Sky-Watcher 4 inch F/9 apo that is truly superb, tested at 360× and I could not detect ANY aberrations.
No CA and no SA.
A snap-to focus that is dramatic.

SW is, of course, not marketed as a boutique instrument just a very well executed design with many years of production behind it.

Is it that factor that has transformed them, more likely than not, from being good to being great?

Even if it was just an average sample, a good scope, it would still be a marvelous transportation machine able to take one on many wonderful and great journies to happyland.

A great one does exactly the same journey but the trip is more like taking a first class ticket ride to perfect contrast and amazing sharpness where one runs out of light before image breakdown occurs.

After two years of use it has become crystal clear that it is truly superb and not merely great!

The cost savings maybe assumes a less rigourous quality standard than more upscale brands but I believe its long production history equalizes that margin considerably.

YMMV!!


Clear skies & Good seeing

P.s. I enjoyed spending the savings on some great eyepieces instead.
P.p.s. totally agree that a superb instrument is a VERY ADDICTIVE drug, my drug of choice!
Edit: wording

Edited by PKDfan, 25 September 2021 - 12:05 AM.

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#53 gzljh96

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Posted 26 September 2021 - 12:26 PM

For me it’s rather simple. I have two good refractors: the RedCat 51 and the Borg 90FL. Light, compact, good/great optics, and very good mechanics. A great refractor for me will be something like a FSQ-85, a FC-100DZ, a TV NP-101, or the FSQ-106, a Borg 107FL F/3.9, or even the Vixen FL55: light (maybe), compact, good/great optics, and very good mechanics — and **great** telescopes, for me, are always the ones I **don’t** have.
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#54 rerun

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Posted 26 September 2021 - 01:14 PM

For me, the difference between a good and a great refractor is in the feeling of the owner. If the owner has the feeling that his telescope is great and the pictures it shows are great, then he has the right refractor for himself. The feeling of being happy with her/his refractor has become rare.


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#55 JeremySh

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Posted 26 September 2021 - 01:59 PM

For me, the difference between a good and a great refractor is in the feeling of the owner. If the owner has the feeling that his telescope is great and the pictures it shows are great, then he has the right refractor for himself. The feeling of being happy with her/his refractor has become rare.

This summarises why one of my smallest refractors is one of my greatest: Tak FOA 60Q smile.gif


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#56 jena100

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Posted 26 September 2021 - 02:14 PM

I have 3 Zeiss Jena telescopes, 2 Vixen telescopes, a TEC 140 and a Stellarvue SVX80T. Hands down the Stellarvue is optical the best.


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#57 kmparsons

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Posted 26 September 2021 - 07:49 PM

A great scope is one that is easy to set up, easy to use, gives great views of whatever you want to look at--at whatever magnification you choose, and is easy to take down and store. Then, when you finally get to bed, you recall what you saw and think "now that was something!" 


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#58 doctordub

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Posted 26 September 2021 - 07:59 PM

A good refractor gives you good views.

A great refractor leaves you with great memories!

CS

Jonathan 


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#59 teashea

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Posted 26 September 2021 - 09:38 PM

Any refractor I own is a good refractor, My achromats, ED's and triplets are all good refractors on most nights of average seeing conditions, ie... Clear sky clock seeing conditons of 3/5.

Every refractor I have is a great refractor when seeing conditions are 4/5 or better. It doesn't mater what the optics are or the name on the label and most importantly, it doesn't mater what it cost.

On near excellent nights of seeing conditions, which in my area in Northern California, is a very rare event, sometimes 5/5 seeing conditions happen less then once in any given year.

On those rare nights of excellent seeing conditions, every refractor is a great refractor, every cassagrain and every reflector is a great reflector.

 

Many people, including myself, over the years have played the telescope shuffle game, many times looking for the scopes that advertise the best optics made with the highest strehl ratios, tightest spot-diagrams and most pixel density's. I would guess that every current modern day ED and triplet refractor from any country, exceeds the resolution and sharpness limits of what our eyes can detect, especially those of us getting up in the years.

 

To me, there are many ways we can  help make our good telescopes become great telescopes. The seeing conditions on any given night, can makes or breaks our optics, and our impression of how are scopes perform. The quality of the eyepieces we use is another factor in how well the sky presents itself to us. Another of course is the front objective and how its configured and the types of glass it uses. Some may add the stability of the mount is a factor and if the scope is acclimated to the outside conditions long enough. Other may consider the ground the scope is sitting on, concrete or pavement seems to generate more heat then lawn or natural ground coverings. How much heat is coming off of the homes we have to look over can also play a part in how our refractors perform. In my area, I have to also consider overhead jet streams since these can destroy seeing conditions despite what appears to be clear crisp skies we are observing in. Smoke from fires are always and issue here in California in the late summer months. Sometimes, the Clear Sky Clock is showing dark clear skies, but the smoke in the sky will block out everything but the moon.

 

I wonder how many refractor aficionados consider all of these options in their area before taking out their refractors for a night of observing. I usually do, unless I just wanna go out for a quick hour or two. On weekends where I plan to stay out till early morning, those results determine the size and type of scope I take out. Just some food for thought.

 

...Ralph

seeing conditions ---- indeed



#60 Ballyhoo

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Posted 26 September 2021 - 10:00 PM

I wonder if I get too wrapped up on this issue and instead should savor the views my not so great refractors deliver.  I am still stunned by the views of the moon I got on my ED 152 ED triplet - not considered a great scope and the one who sold it to me is or has gone on to a more expensive brand. But for me the 6" in its current no so great state yields stunning images and views.



#61 imtl

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Posted 27 September 2021 - 08:12 AM

The difference is that with a good frac you "discuss it" on CN while with an excellent frac you brag about it on CN.


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#62 Lookitup

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Posted 27 September 2021 - 09:06 AM

For me the "best" is always knowing it can't get any better in the given aperture. Tak DF qualifies waytogo.gif


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#63 bobhen

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Posted 27 September 2021 - 09:58 AM

Any refractor I own is a good refractor, My achromats, ED's and triplets are all good refractors on most nights of average seeing conditions, ie... Clear sky clock seeing conditons of 3/5.

Every refractor I have is a great refractor when seeing conditions are 4/5 or better. It doesn't mater what the optics are or the name on the label and most importantly, it doesn't mater what it cost.

On near excellent nights of seeing conditions, which in my area in Northern California, is a very rare event, sometimes 5/5 seeing conditions happen less then once in any given year.

On those rare nights of excellent seeing conditions, every refractor is a great refractor, every cassagrain and every reflector is a great reflector.

 

...Ralph

Seeing will have no impact on the quality of the optic. If the optic is one-tenth wave, it is one-tenth wave in poor, average or excellent seeing. If the optic is one-quarter wave, it is one-quarter wave in poor, average or excellent seeing.

 

That you get sharper views in excellent seeing in any scope is of course obvious. But a one-tenth wave optic will deliver even sharper views and even better/more detail in excellent seeing than will a one-quarter wave optic, just as it will in any type of seeing.

 

In other words, seeing impacts all telescopes, no matter their quality level. But better seeing will not turn an average optic into a great one, even if on an excellent night what is seen is more detailed than on an average night, because in comparison, an excellent optic will do even better on the same night, take more magnification, remain sharer and deliver more/better details.

 

As a matter of fact, the best defense for those many nights of average seeing is a high quality optic, because average seeing and an average optic combine to equal "below" average views in the eyepiece whereas average seeing and an excellent optic combine to deliver "average" views in the eyepiece. On an average night of seeing, what would you rather have, an "average view" or a "below average" view?

 

The “quality of the optic”, "not the seeing",  is what separates a great refractor from a good one.

 

Bob


Edited by bobhen, 27 September 2021 - 09:59 AM.

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#64 csrlice12

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Posted 27 September 2021 - 10:34 AM

A good scope has the capability to perform at its best when called upon....a great scope is the one you use the most.


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#65 25585

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Posted 27 September 2021 - 10:53 AM

A good scope has the capability to perform at its best when called upon....a great scope is the one you use the most.

Army or Marines?



#66 doctordub

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Posted 27 September 2021 - 12:29 PM

Army or Marines?

Space Force! lol.gif

CS

Jonathan


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