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Where does "serious aperture" begin?

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#1 Karl_Bonner_1982

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Posted 04 March 2010 - 11:04 AM

As we mature and catch aperture fever, we start wanting bigger and bigger telescopes. But you usually don't hear any specific numbers about this phenomenon.

What do you consider to be the minimum aperture that could be classified as a "light bucket"? And when you think of aperture fever, what number first comes to mind? I'm looking for a serious answer, not a clever joke or exaggeration.

I'd bet that most aperture fever patients never get above about 16 while a sizable minority probably makes it to 20. Anything beyond that and you're likely looking at a few diehards, the absolute top of the pile.

As for me, I think the fun begins as soon as you get above 10", with 20" getting into hardcore territory.
 

#2 Lard Greystoke

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Posted 04 March 2010 - 11:49 AM

If you've been around for any number of years, the "supply side" of the equation has changed dramatically.

When I was starting out a 12" scope was considered huge. Typically they were home-made; the mass market was in the 6-8" Dynascope range. (Setting circles were literally that: mechanical circles, and they were not at all easy to align precisely).

Now mass market runs up to 16". I suppose "serious aperture" begins around that point. Apart from the improvements in technology and marketing, for deep-sky objects I think 12" starts to make a difference.
 

#3 epee

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Posted 04 March 2010 - 11:51 AM

Serious aperture is the scope you just bought or are wanting to buy. :lol:

"Light bucket"; in my mind, is more a function of f ratio than aperture. If a scope is designed primarily to look deep rather than close it is a light bucket.
 

#4 dave b

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Posted 04 March 2010 - 11:55 AM

a serious Newtonian where suddenly everything seems within reach happens around 22-24".

i know some people are going to howl about that, but if you have owned a bunch of large dobs for years, you find that to be totally true. at that point you are allowed to wear the "averted vision is for kitties" t shirt and not get laughed at.
 

#5 skyward_eyes

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Posted 04 March 2010 - 12:08 PM

I agree with Dave, I have used several large dobs (my weapon of choice) up to 30" and after a lot of time at the eyepiece of a 28" I have found that once you get to the 22" range things really start to take shape. I believe serious aperture starts at 24" and goes up.
 

#6 FirstSight

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Posted 04 March 2010 - 12:09 PM

Undoubtedly, the most meaningful definition of "serious aperture" relates to the optical resolution reach of the scope - what is it capable of resolving with articulate sharpness and sufficient brightness, without unacceptable aberrations.

Nonetheless, a meaningful (nonoptical) informal correlation with "serious aperture" used to be the size where it is no longer possible for average-height people to observe near the zenith without aid of a stepladder. That's because it used to be forbiddingly difficult and expensive to obtain consistently high-quality mirrors below about f/4.5. The dividing line fell between 15-inch f/4.5 scopes at the upper end of "don't need a ladder", and 18-inch f/4.5 scopes at the lower end of "need at least a two-step stool", with 16-inch scopes in ambiguous territory, depending on your height. Beyond 18", and you used to need a regular multi-step ladder at least four to five feet high for an f/4.5 20" scope.

Now, however with consistent high-quality sub-f/4.5 mirrors becoming available from a limited, but sufficient (to meet current premium-price demand) number of sources - f/4.2, f/4.0, f/3.7 and even f/3.3 mirrors...this "stepladder" heuristic is becoming badly frayed (at least at the highest premium end of the spectrum), and 20-inch scopes have replaced 15-inch scopes as the upper bound of "stand on the ground". Another informal (nonoptical) heuristic measure these new very fast f-ratio larger-aperture scopes have recently frayed is the distinction between scopes small enough to be easily portable in an average-sized sedan, vs ones requiring a more ample vehicle, which used to correlate roughly (though imperfectly) with the "stepladder" heuristic. (Maybe it still does, though shifted along with the stepladder heuristic toward 20" instead of 12" or 15").

One informal optical measure is how overtly the aperture is capable of showing spiral structure in how many galaxies under say, mag 6.0 skies. This can start with as little as 10" or especially 12", but occurs much more readily with 18" or 20". I've heard lots of people comment that good 20" scopes is where significantly more detail begins coming out, just as 10"-12" seems to be another similar lower-level quantum boundary.
 

#7 Mike B

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Posted 04 March 2010 - 12:16 PM

Excellent reply, Chris! A very well-thought-thru analysis, touching on several key aspects of the matter.
:bow:
 

#8 jayscheuerle

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Posted 04 March 2010 - 01:21 PM

It begins when you need to make payments instead of buying it outright... - j
 

#9 D. Perry

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Posted 04 March 2010 - 02:53 PM

Where does "serious aperture" begin? Exactly where frivolous aperture ends.

:-)
 

#10 Garfield

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Posted 04 March 2010 - 03:19 PM

I hate to tread water with the likes of this group(!), but all I can do is answer this question based on my own experience. The biggest aperture scope I've ever owned (out of more than a dozen) was a 12.5" reflector (Portaball actually). Compared to my smaller scopes it was impressive....initially. But in a few years I realized that a 12.5" dob was the proverbial jack-of-all-trades, master-of-none (though it performed spectacularly well on the planets/binoviewer).

Of course I've viewed through larger scopes from time to time...and decided a long time ago that if/when I ever buy a light bucket it will be a fast 18" -- because I think that's when DSO's really start to become satisfying without going overboard in terms of size/weight and cost.

But for now, I'm going settle for a piddly 8"...and that's very well where I may stay.
 

#11 StarStructure Telescopes

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Posted 04 March 2010 - 03:37 PM

This is one of those questions that will be highly opinionated.

If your accustom to viewing through smaller apertures (IMO 80mm to 18”), I would say that 16” is where the common objects, that we all view, show nice detail and satisfy most people. Another words, If someone with a good quality 16” looks through someone else’s good quality 24” they don’t go back to the 16” with total disappointment.

If your accustom to viewing through larger aperture (IMO 20” to 32”) I have to agree with Dave B. 22” to 24” is where most everything worth looking at is going to be very satisfying.

So I would have to say that serious aperture begins at around 22”.

Mike
 

#12 Jim Romanski

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Posted 04 March 2010 - 03:39 PM

I haven't owned anything as large as what Dave talks about but have looked through many at star parties.

My take on the question is that it begins in the 18-20 inch range.

This is really the size where globulars become as nice as open clusters in a small scope.

It's also the size where you really get significant contrast improvemenst when using a filter.
 

#13 Don W

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Posted 04 March 2010 - 05:18 PM

I've always felt that you really start to see some good detail in galaxies with a 12" scope. It's also a very easy size to handle. I have spent some time going up and down tall ladders to view through friends 20" plus scopes as well as my own and really would rather keep my feet on the ground or maybe one or two steps up a short ladder.
 

#14 gnowellsct

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Posted 04 March 2010 - 06:01 PM

Serious aperture begins at 4 inches. 4 inches opens up the sky relative to the naked eye and revolutionized astronomy for two centuries. Sue French filled a book with observations made with a four inch scope and continues to add details in her current S&T column. You can see the planets (Saturn's rings, Jupiter's GRS) and even Pluto in a four inch, and many thousands of galaxies, open clusters, nebulae, and planetary nebulae.

So, if we take a 5mm pupil and compare it to a 102mm scope, as a ratio 5:102mm, the next step up is 102mm:2080mm, which is an 82 inch scope.

I conclude therefore that the next step up is 82 inches and that everything under that, particularly amateur level instruments from 5 to 30 inches, is just piddling around.

Incidentally to my way of thinking it is not coincidental, looking at things this way, that the apertures of the 19th century up to and including the Rosse telescope charted the sky but did not revolutionize our understanding of it. It was the hundred inch Hooker telescope that took things to the next level by resolving stars in other galaxies.

regards
Greg N
 

#15 John Miele

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Posted 04 March 2010 - 06:32 PM

...at that point you are allowed to wear the "averted vision is for kitties" t shirt ...


Love it!!! :roflmao: :lol: :roflmao:
 

#16 siriusandthepup

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Posted 04 March 2010 - 06:37 PM

Of course it is opinion, but based on using a lot of different scopes - I see two "breaks" for serious aperture. The first is at 12". For me there is a threshold at 12" that a 10" just doesn't meet. 12" is the first step on the road to serious aperture. More nebulosity, more color, more detail, fainter stars, more galaxy detail = More. This bracket goes from 12" to 16", maybe including 18". The next break I notice is using a 20" to 22" as others have also noted. Again I get the same feelings about the difference between an 18" and a 20" that I have for the difference between a 10 and 12". At 20+ I see more again, especially nebula color and galaxy details and fainter galaxies. You really wouldn't expect there to be that much difference between an 18 and a 20 but for me it is obvious. Above 22" you get into discussing "how much it looks like the photos".

All this is only occasionally relevant because it depends on me getting to a dark sky. Otherwise the view of M51 I get at my home in my 16" is woefully pitiful compared to the view I had at the dark sky location (3.5 hours away)with and 80mm short tube scope. Sad, but true. So reality check time. I view from my home 95% of the time in 5th mag skies. Best compromise scope for all around use? I think a 12" or 12.5" works best for me in terms for ease of use vs. horsepower. Great for planets, moon, mild deep sky and that occasional wandering comet.
 

#17 scoping

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Posted 04 March 2010 - 06:45 PM

a serious Newtonian where suddenly everything seems within reach happens around 22-24".

i know some people are going to howl about that, but if you have owned a bunch of large dobs for years, you find that to be totally true. at that point you are allowed to wear the "averted vision is for kitties" t shirt and not get laughed at.


Dont let Dave fool you. He is just being nice not to hurt anybodys feelings. After having my 20" for years it now seems more like my 13.1. Dave knows serious aperture starts at 28 to 30".

I am saving some serious cash to buy one. Scopes this size are Galaxy Cruisers.

Mark Kaupas
Wimpy 20" :bawling:
 

#18 Shawn H

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Posted 05 March 2010 - 10:21 AM

Dave's probley right at 22-24", but for me "serious aperture payments" started at 18"! :grin:
 

#19 Shawn H

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Posted 05 March 2010 - 10:25 AM

AND at 18"! I can get by with a little step stool, I don't need a fire engine ladder! :grin: :rainbow:
 

#20 FirstSight

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Posted 05 March 2010 - 10:42 AM

...where "serious" money begins.
 

#21 Jeronimo Cruz

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Posted 05 March 2010 - 10:43 AM

I use a 16", a 20", and recently a 36".

Aperture rules, no doubt. But, at least visually, the 16" doesn't give up too much to the 20". When I use the 16", I am satisfied. I don't have that gnawing feeling that I'm not seeing something that I could in the 20". For me there is a bigger jump visually between a 12" and a 16".

So for me serious aperture begins at 16".
 

#22 skyward_eyes

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Posted 05 March 2010 - 11:07 AM

Its helps when you have amazing equipment atop Kitt Peak at 7000 feet elevation...
:grin: :grin:
I need to come up and play with those scopes!
 

#23 magic612

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Posted 05 March 2010 - 11:07 AM

Serious aperture begins at 4 inches. 4 inches opens up the sky relative to the naked eye and revolutionized astronomy for two centuries. Sue French filled a book with observations made with a four inch scope and continues to add details in her current S&T column.


Truthfully, I really like Greg's answer. :)

But in my mind, it's when you need a trailer and (likely) more than one person to set up the scope that it becomes "serious" aperture, because that's the point where:

1) You can seriously hurt your back moving it
2) You can seriously hurt your bank account buying it
3) You can seriously hurt your eye(s) viewing through it (imagine viewing Sirius through a 22" scope with a 7mm exit pupil...)

I'd say whatever aperture that requires, it's pretty serious. That said, I like my 10" Dob. I can see a lot in it, and I can still transport it in the backseat of my Buick Century without needing a collapsible OTA. Or a trailer. Or a second person to help me set it up. Or a second mortgage to pay for it. (Sorry, gotta tweak you guys with that really big glass somehow. Yes, it's a twinge of jealousy.) ;)

But opinions will vary, and the aperture size of "serious" will continue to climb as costs continue to come down (just wait til the Chinese start making mass-produced 22" mirrors!). 12" was considered "serious" not all that long ago. Now it's considered the start of being able to see significant detail.

In 20 years, "serious" aperture will be 50 inches. I mean shoot, just look at what Orion is currently offering. People will be scoffing at those "piddly" 18" and 22" scopes then. :lol:
 

#24 Darenwh

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Posted 05 March 2010 - 11:46 AM

Serious aperature for the Moon: 75mm
Serious aperature for the Planets: 6"
Serious aperature for all else: Depends on where you are observing from. Top of Mauna Kea or equally dark site: 8", Green zone: 12", all others: 16"
 

#25 Lard Greystoke

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Posted 05 March 2010 - 11:50 AM

I conclude therefore that the next step up is 82 inches and that everything under that, particularly amateur level instruments from 5 to 30 inches, is just piddling around.
regards
Greg N


That's saying it. And of course this includes the Orion "monster Dobs" as well. Nice to see someone finally put that fire out.
 


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