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Visual observing: big APO refractor VS. big Dobson

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#76 Tyson M

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Posted 26 September 2020 - 01:39 PM

Asking this exact topic in the reflector forum might garner different answers. 

 

I am in the big refractor crowd. If I was into faint fuzzies more a big dob is more practical approach though. 


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#77 Echolight

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Posted 26 September 2020 - 01:53 PM

Asking this exact topic in the reflector forum might garner different answers. 

 

I am in the big refractor crowd. If I was into faint fuzzies more a big dob is more practical approach though. 

Neither is really "practical" for most skygazers. 

 

A which is most practical would be tabletop dob vs small ed refractor.



#78 Jon Isaacs

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Posted 26 September 2020 - 03:48 PM

HERE is a link to very detailed website about astronomical seeing. Below is a relevant statement from that site…

 

“How often do nights of excellent seeing occur? At the William Herschel Telescope site in the Canary Islands, even this superb viewing location, second best in the northern Hemisphere, has many nights of relatively poor seeing: the distribution is positively skewed... and at this excellent site, a 10 inch telescope will experience seeing limitations on 9 out of 10 nights.”

 

If a 10-inch scope is seeing limited 9 out of 10 nights at La Palma, which has some of the best seeing in the world! – What are the odds in your backyard? And if the planets are not well placed, like the past few years, and at many times during an appearance, that will also lower those odds even more.

 

As to imaging, I stated in my earlier post “imaging” is a "different animal", as it is possible to eliminate some seeing issues and add contrast, etc. in data capture and processing.

 

Bob

 

I liked this much better, it's realistic.

 

"“A 5-inch refractor is ideal for high resolution visual use on the sun, moon, and planets. Its resolving power of 0.9 arcseconds is perfect for sampling the typical seeing of 2 to 3 arcseconds common at most amateur observing locations….”"

 

The statement that a 10 inch scope will experience seeing limitations 9 nights out of 10 nights requires some explanation.  

 

The Dawes limit for a 10 inch scope is 0.456".  That means that is sometime during the night, the seeing is not 1/2 arc-second, a 10 inch scope will be seeing limited.  Not many places have better than 1/2 arc-second seeing but plenty of places are between 0.5" and 1".

 

The reality is that in 1" seeing a 10 inch will significantly out perform a 5 inch.  

 

This is why Sky and Telescope said that a refractir with a Dawes limit of 0.9 arc-seconds is well suited for typically seeing of 2-3 arc-seconds.  It's not well suited for 1 arc-second seeing but it is well suited for rather poor seeing. 

 

Jon


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#79 Jon Isaacs

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Posted 26 September 2020 - 04:01 PM

My bold.  I think you are mistaken.  As I understand it, combinations of aperture and magnification that have the same sized exit pupil will have the same sky background brightness.  Perhaps you are having the illusion of a darker sky in the bigger scope because the stars are brighter.  I cannot think of anything else.

 

At the same exit pupil, the sky is the same brightness.  In the larger scope, the object is larger which for small objects and details provides the perception of greater contrast, the eye likes a larger image.  And stars, they are brighter in the larger scope since star brightness is a function of the square of the aperture.  The stars in a 12 inch are 4 times brighter than the stars in a 6 inch and at the same exit pupil, the contrast is 4 times greater.  

 

I think this is the biggest surprise when using large aperture scopes, just how bright the stars are.  In a 25 inch, they are about 25 times brighter than in a 5 inch, that's more than 3 magnitudes.  Polaris becomes Sirius, Sirius is as bright as Venus is at it's brightest.  

 

Jon



#80 Jon Isaacs

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Posted 26 September 2020 - 04:05 PM

Sure the views were brighter in the larger instruments but there was nothing I ever saw in the 16” or 14” I could not pick up in the 7”, either planetary or deep sky.

 

I have to think you were not hunting down faint galaxies.  And clearly you weren't splitting double stars. 

 

Jon


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#81 Urbyz

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Posted 26 September 2020 - 04:08 PM

Yes, it pulled in more faint fuzzies, but high-power planetary on that AZ platform? Nope. I prefer GEMs for serious observing (30 minutes or more studying 1 object). So, I meant it about my 1980s Meade 826 -- it does everything well. It's easy to set up, take down, and use -- easier than my much more $$$$ 2017 APM 152ED. (In fact, I'm thinking of selling the Big ED.) A light 8" F6 Newt on a solid GEM with good visual tracking up to 400x... what's not to love??


So far i only have a 6” table dob. Itmight not be much to some, but for me it so convenient to handle and set up in no time. I guess bigger more complex dob mounts may be more cumbersome, but putting the newts on a GEM instead might just be a great idea.
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#82 Urbyz

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Posted 26 September 2020 - 04:15 PM

Hoi Urbyz,

I can recommend you to go to Rijswijk observatory. There in even more light polluted skies you can see for yourself if a large aperture instrument can help you what you are looking for.
Have fun.


Dank je!

That’s a great tip. I’ll look into it and see if i can finally put all of the shared wisdom on here to the test.
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#83 hoof

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Posted 26 September 2020 - 04:18 PM

I think this is the biggest surprise when using large aperture scopes, just how bright the stars are. In a 25 inch, they are about 25 times brighter than in a 5 inch, that's more than 3 magnitudes. Polaris becomes Sirius, Sirius is as bright as Venus is at it's brightest.

Jon


And this affects the perceived aesthetics. When a star appears as just a disc (because the first ring is too dim), they look like stars. Brighten them up a lot, and that first ring becomes obvious. Ironically the lack of light gathering capability of small aperture refractors may be aiding in the aesthetics of starfields, at least for exit pupils small enough to show the first ring distinctly.

#84 areyoukiddingme

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Posted 26 September 2020 - 04:25 PM

My location is frequently 1.8 to 2.0 arcsec seeing, at least according to: 

 

https://www.goodtostargaze.com/

 

Tonight's prediction is 1.8 to 2.1 at different hours. For comparison San Diego is .6 to .8 (lucky buggers!).

 

These are, of course, average estimates. So even if a 10" Dob has a Dawes limit of about .5 arcseconds, my bet is that where I live there are moments and little 20-30s runs on the seeing that would get me close to that resolution.

 

Given that planetary viewing is a patience game, I'm more than happy to wait for those moments.


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#85 stevew

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Posted 26 September 2020 - 07:50 PM

 

 I’m starting to wonder if maybe a 10” dob aside a high end refractor would be a nice combo to last me.

A good quality refractor and a 10 inch Dobsonian is a great combination that will keep you busy for decades..
 


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#86 Tyson M

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Posted 26 September 2020 - 08:24 PM

My location is frequently 1.8 to 2.0 arcsec seeing, at least according to: 

 

https://www.goodtostargaze.com/

 

Tonight's prediction is 1.8 to 2.1 at different hours. For comparison San Diego is .6 to .8 (lucky buggers!).

 

These are, of course, average estimates. So even if a 10" Dob has a Dawes limit of about .5 arcseconds, my bet is that where I live there are moments and little 20-30s runs on the seeing that would get me close to that resolution.

 

Given that planetary viewing is a patience game, I'm more than happy to wait for those moments.

Nice webpage! Bookmarked for the seeing calculator and relevant info.  Tonight is not the greatest (1.7-1.8), so I will be using my APM 100 Binoculars.


Edited by Tyson M, 26 September 2020 - 08:38 PM.


#87 gnowellsct

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Posted 26 September 2020 - 09:02 PM

HERE is a link to very detailed website about astronomical seeing. Below is a relevant statement from that site…

“How often do nights of excellent seeing occur? At the William Herschel Telescope site in the Canary Islands, even this superb viewing location, second best in the northern Hemisphere, has many nights of relatively poor seeing: the distribution is positively skewed... and at this excellent site, a 10 inch telescope will experience seeing limitations on 9 out of 10 nights.”

If a 10-inch scope is seeing limited 9 out of 10 nights at La Palma, which has some of the best seeing in the world! – What are the odds in your backyard? And if the planets are not well placed, like the past few years, and at many times during an appearance, that will also lower those odds even more.

As to imaging, I stated in my earlier post “imaging” is a "different animal", as it is possible to eliminate some seeing issues and add contrast, etc. in data capture and processing.

Bob


Well I think the key thing is to spend time at the eyepiece rather than searching for sacred texts to cite and throw in people's faces.

seeing limited observing does not mean that you have to limit yourself to small apertures. Seeing limited observing might mean that one second out of three is bad and one second out of three is mediocre and one second out of three is pretty good. You can even have situations in nights of bad seeing where you will get a 10 or 15 second run of an excellent view. then you observe for another 60 seconds or so and then maybe you get another 10 seconds of a good view. anyone who knows anything about statistics knows that an average means nothing if not accompanied with a standard deviation. This is especially true where there is wide variance as is the case with seeing.

Anyone who has spent time at an eyepiece knows that this is the way it works: You observe a while, might seem okay, suddenly it becomes spectacular, then it goes back to okay then it gets bad. Then it might stay bad for quite some time. But giving up is not how planetary observers are made. It is disingenuous to suggest that the best one can do is with a 5-in aperture even if it is an apo.

And since when is a tiny exit pupil the best way to see anything if observing over extended periods? actually I don't know why I'm arguing this point. Anybody who spends 15 seconds on a good 10 to 15-in newt will know that it is outperforming a 5-inch Apo.

I shall add I think refractors are fantastic and they represent just in the optical tubes about 1/2 of my total investment in astronomy including mounts oculars SCTs and innumerable other peripherals.

I have invested heavily in them because they're beautiful and deliver value to my observing as well as the possibilities of simplified set up and easier management in cold weather.

I'm not arguing against refractors I'm just saying they're not miracle devices.
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#88 Jon Isaacs

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Posted 27 September 2020 - 04:52 AM

And this affects the perceived aesthetics. When a star appears as just a disc (because the first ring is too dim), they look like stars. Brighten them up a lot, and that first ring becomes obvious. Ironically the lack of light gathering capability of small aperture refractors may be aiding in the aesthetics of starfields, at least for exit pupils small enough to show the first ring distinctly.

 

I think you are much more likely to see diffraction rings with a small scope than with a large one. The Airy disks are so much smaller, the rings so much smaller, it's rare to see them in a large scope.

 

As far as aesthetics..  If you don't mind M79 looking like a fuzz ball.. When I sold my 25 inch, the buyer spent the night with it.  He had brought his C-11, it was in his van already and he asked if I minded if he set it up to compare. I said I had no problem but that I was confident after his first look, he would realize it was unnecessary.. 

 

The next morning he told me:  M79 in the 25 inch looks like M13 does in my 11 inch SCT.  Now M13 is actually quite detailed in an 11 inch SCT.  And the numbers work out. 

 

There is an place for aesthetics but not at the expense of seeing detail.  The 25 inch F/5 with an aperture mask could be a 10 inch F/12.5 with no CO. 

 

jon 


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#89 Jon Isaacs

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Posted 27 September 2020 - 04:59 AM

So far i only have a 6” table dob. Itmight not be much to some, but for me it so convenient to handle and set up in no time. I guess bigger more complex dob mounts may be more cumbersome, but putting the newts on a GEM instead might just be a great idea.

 

Big Dob mounts are as simple as small Dob mounts, it doesn't get any simpler.

 

In my experience, Newtonians on GEMs are not such a great idea.  A GEM is far more complex than any DOB mount and the observer faces a number of issues.  The biggest is the eyepiece position.  As the scope moves about the sky, the tube rotates.  The eyepiece ends up in the wrong place and it's necessary to rotate the tube.  This makes "rotating rings" necessary.  They work OK but it's easy to lose alignment.  

 

In general, a larger Newtonian on a GEM is a real beast. Heavy, awkward, time consuming to setup.  The Dobsonian really did revolutionize the Newtonian.

 

Jon


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#90 Jon Isaacs

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Posted 27 September 2020 - 05:03 AM

My location is frequently 1.8 to 2.0 arcsec seeing, at least according to: 

 

https://www.goodtostargaze.com/

 

Tonight's prediction is 1.8 to 2.1 at different hours. For comparison San Diego is .6 to .8 (lucky buggers!).

 

These are, of course, average estimates. So even if a 10" Dob has a Dawes limit of about .5 arcseconds, my bet is that where I live there are moments and little 20-30s runs on the seeing that would get me close to that resolution.

 

Given that planetary viewing is a patience game, I'm more than happy to wait for those moments.

That was about right. 

 

Last night the seeing was decent.  I got a clean split on Lambda Cygni. Its a mag 4.7-6.3 double with a separation of 0.92 arc-second.  I was using my 10 inch GSO Dob.. "$240 on Astromart 17 years ago."   

 

Jon


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#91 bobhen

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Posted 27 September 2020 - 07:34 AM

Well I think the key thing is to spend time at the eyepiece rather than searching for sacred texts to cite and throw in people's faces.

seeing limited observing does not mean that you have to limit yourself to small apertures. Seeing limited observing might mean that one second out of three is bad and one second out of three is mediocre and one second out of three is pretty good. You can even have situations in nights of bad seeing where you will get a 10 or 15 second run of an excellent view. then you observe for another 60 seconds or so and then maybe you get another 10 seconds of a good view. anyone who knows anything about statistics knows that an average means nothing if not accompanied with a standard deviation. This is especially true where there is wide variance as is the case with seeing.

Anyone who has spent time at an eyepiece knows that this is the way it works: You observe a while, might seem okay, suddenly it becomes spectacular, then it goes back to okay then it gets bad. Then it might stay bad for quite some time. But giving up is not how planetary observers are made. It is disingenuous to suggest that the best one can do is with a 5-in aperture even if it is an apo.

And since when is a tiny exit pupil the best way to see anything if observing over extended periods? actually I don't know why I'm arguing this point. Anybody who spends 15 seconds on a good 10 to 15-in newt will know that it is outperforming a 5-inch Apo.

I shall add I think refractors are fantastic and they represent just in the optical tubes about 1/2 of my total investment in astronomy including mounts oculars SCTs and innumerable other peripherals.

I have invested heavily in them because they're beautiful and deliver value to my observing as well as the possibilities of simplified set up and easier management in cold weather.

I'm not arguing against refractors I'm just saying they're not miracle devices.

 

People should read the complete article linked. Skip to the last 8 paragraphs for somewhat of a summary.  HERE is the link.

 

Using the word “sacred text” is not only laughable but is a complete misrepresentation of this comprehensive article with studies done at professional observatories over many years. How seeing is evaluated by professionals and the “probabilities” derived are of interest. I have not even quoted some of the more interesting findings.

 

Have fun.

 

Bob



#92 aztrodog

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Posted 27 September 2020 - 09:35 AM

I have to think you were not hunting down faint galaxies.  And clearly you weren't splitting double stars. 

 

Jon

Jon - Hard to chase faint galaxies from anywhere close to South Florida on account of light pollution. However, I have “seen” more deep sky objects from the comfort of my backyard with the 7” than any other scope. Just my eyeballs were not peeking into an eyepiece. The 11” SCT does lend itself nicely to alternative viewing of deep sky viewing. 
 

Splitting doubles I would also vastly prefer the refractor. Much easier to make out even small elongations of really right pairs under most conditions with the 7” the larger aperture scopes I had access to,

 

A top notch bigger Newt in the 10 to 14.5" range will kill any 6" APO in my super steady seeing.  A world class 6" APO and mount are gonna be $10 to 13k when a used 14.5" Starmaster or other top notch Dob is gonna be around $3 to 5k.

 

Go up to a 8" APO when the cost is around 25 to 35k for the scope and mount and it still won't touch a 14.5" Zambuto in my seeing.

Chas you need to sell your Vette, get a Yugo so you can free up some cash to buy yourself a real 6” APO and keep it long enough to see what it can do. 

 

My friend Sergio owns a 16” Starstructure with a Zambuto mirror and it has yet to “kill” his Tak 152. As a matter of fact, the 152 and a smaller 90mm Tak have become his most used scopes.The 11” you sold to my other compadre here in Miami some years back is wonderful, but it does not smoke any decent 6” APO much less the 7”. And yes, our skies are just as steady as yours in Tampa and better if we travel 2 hours south into the Florida Keys. Different views with different appeal given the object and observing conditions yes, but for sure killing, smoking, leaving in the dust are not something most experienced observers who have had these two side by side for extended periods of time would agree with.
 

As far as costs and since you like cars....should we all drive Tesla Model 3s because it smokes anything from vettes to lambos at a fraction of the cost? I think not.

 

When I go under the stars I want a Swiss Army knife of a scope, a scope with enough aperture and the best possible optics so I won’t have to questions If I am getting the best possible image. A scope I can roll out, plug into a 12vdc source, focus and enjoy...only a refractor has checked all of those boxes for me (excluding my sorry 178ED) in close to 40 years as a backyard astronomer and countless number of telescopes. 


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#93 Bomber Bob

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Posted 27 September 2020 - 12:25 PM

I have to think you were not hunting down faint galaxies.  And clearly you weren't splitting double stars. 

 

Jon

Even in my back yard, my small (these days) 8" F6 Newt delivers 2x to 4x the number of galaxies in the Coma-Virgo Realm of Galaxies than my APM 152ED F8.  FWIW:  When I really want to study the dust lanes in M31, I use my antique Tinsley 6" F20 Cass.  Or, one of the best views I get of the Dumbbell Nebula is with my 1958 Questar Standard.  IOW:  Different objects, seeing, etc. = different scopes.

 

Buy / Use enough scopes, under a variety of seeing conditions, and you figure out that variety in type & design matter.  Not every object is a nail, so there is no one perfect hammer. 


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#94 Bomber Bob

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Posted 27 September 2020 - 12:34 PM

A top notch bigger Newt in the 10 to 14.5" range will kill any 6" APO in my super steady seeing.  A world class 6" APO and mount are gonna be $10 to 13k when a used 14.5" Starmaster or other top notch Dob is gonna be around $3 to 5k.

 

Go up to a 8" APO when the cost is around 25 to 35k for the scope and mount and it still won't touch a 14.5" Zambuto in my seeing.

Similar seeing here at The Swamp -- just more clouds.  A clean & collimated reflector can challenge a much more expensive APO.  Seen it myself.  Make some modest contrast & functional improvements to that reflector, and... Wow!  I've seen it at the Mid-Tier level -- I'm not paying Big Bucks for any scope.  This is a hobby.  Folks who have invested in top-tier refractors & reflectors probably have a different opinion, and that's okay.  

 

Anyway, OP, I hope we haven't gone too far off-topic from your original question.


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#95 Urbyz

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Posted 27 September 2020 - 04:36 PM

Anyway, OP, I hope we haven't gone too far off-topic from your original question.


To be truly honest. The thread has turned out to be exactly what i believe confuses beginners looking to find what scope suits them best. But this time around it was slightly different, not as confusing, since i saw the whole discussion unfold.

The last couple of posts is where it gets confusing. Different experienced users claiming opposite to each other. If it weren’t for the start of this topic, where posts felt more balanced and objective, i still would’ve been left with confusion. The take-away for me is, even though some might back their claims with research, that the choice between a big dob or refractor depends greatly on seeing conditions, quality of equipment, the objects being observed and maybe most leading of all: personal preference..

What seems to be agreed upon at least, is that dobs can achieve the same or at least close to performance as the refractors for a fraction of the price. Though be it the views would be slightly different due to their differences in design.

All in all I don’t think there is any good or bad choice to be made and it all comes down to what works for you. It kind of stinks i’m not able to “see for myself” as easily these days. But i think a reasonably sized dob, let’s day 12”, companioned by a high end 5” APO would be a nice versatile couple to have. Separate as wel some might say.

Price always plays a factor and i’m not in a situation where i can easliy finance an APO 6” or above. So the claims of 7” do-it-all APO’s don’t apply to me. Also portability wise it’s a no go. As i said earlier: it’ll probably come down to personal preference and what you like to see and consider nice views.

If we’re being real i’ll probably save up for a nice 5” APO and buy a 10 or 12” dob not long after because i’ll wonder what views i’m missing.. or vice versa.

Thank you all for the great insights and please add to the topic if you feel like there’s more to add.

Best,

Ruben
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#96 Kunama

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Posted 27 September 2020 - 06:07 PM

To be truly honest...........

If we’re being real I’ll probably save up for a nice 5” APO and buy a 10 or 12” dob not long after because I’ll wonder what views I’m missing.. or vice versa.

Thank you all for the great insights and please add to the topic if you feel like there’s more to add.

Best,

Ruben

I think a 5" ED or Apo refractor paired with a nice 12" F5 Dob would give you a lifetime of nice views.  waytogo.gif

 

I don't agree that a Dob will always beat a good refractor, there is a quality about the view in a good apochromatic refractor that is hard to beat.  It takes a very good mirror in a well collimated and set up Newtonian to match that quality.  To many people it is still all about quantity/aperture, perhaps they haven't used a decent refractor yet.  cool.gif

 

My advice to you would be to find a club or other astro gathering (even if it means a longer trip) and try out a few scopes before jumping in with your Euro/$$.

I have paired a 6" refractor and an 18" Dob (with one of the finest mirrors I have ever used) as my "lifetime" scopes, but a 5"/12" pair would be fine as well.


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#97 gwlee

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Posted 27 September 2020 - 06:19 PM

Hi there,

I’ve been a proud owner of a small 6” dobson and enjoy using it very much. Being a little smaller and looking at other scopes online, naturally the mind starts to wonder what a bigger scope might reveal through the lens. I might’ve caught some aperture envy!

Looking online i started developing an interest for refractors. Not exactly sure why, but something draws me to their form factor and it might be due to the stories about crisp, contrasty views you’ll only get with a high end APO triplet refractor. Visually as wel as for AP.

I’m very aware that larger dobsons deliver the best bang for buck views and aperture possibilities. Their big aperture lends well for viewing both DSO and planets and the dob mount lends itself perfectly for easy visual observing. But when i read high-end APO triplet refractor (~6k $) product descriptions, it tells me they are capable of also showing details in faint DSO’s and sharp images of planets at very high magnification.

Now my question is: (And forget about the cost for a minute. I realize it can costs thousands on top of the scope for a big refractor) Purely visually. What will be the difference looking at planets and dso’s through a 6k, let’s say 130-140mm, APO refractor compared to a good 12-16” dobson?

I only observe visually so far, but might take up AP in the future.

Best,

Ruben

In round numbers, the  Dob you described will resolve objects more than twice as small, which is very important for planets, and gather more than four times as much light, which is very important for DS0s. 
 

My garden variety 6”8 Dobs have have easily out performed my pedigreed, 4” class refractors for resolution and light grasp. Expect it would take at least a 115mm refractor to equal a 6” Dob, but refractors have other endearing qualities, so I have two of them. 


Edited by gwlee, 27 September 2020 - 06:22 PM.


#98 CHASLX200

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Posted 27 September 2020 - 06:27 PM

Jon - Hard to chase faint galaxies from anywhere close to South Florida on account of light pollution. However, I have “seen” more deep sky objects from the comfort of my backyard with the 7” than any other scope. Just my eyeballs were not peeking into an eyepiece. The 11” SCT does lend itself nicely to alternative viewing of deep sky viewing. 
 

Splitting doubles I would also vastly prefer the refractor. Much easier to make out even small elongations of really right pairs under most conditions with the 7” the larger aperture scopes I had access to,

 

Chas you need to sell your Vette, get a Yugo so you can free up some cash to buy yourself a real 6” APO and keep it long enough to see what it can do. 

 

My friend Sergio owns a 16” Starstructure with a Zambuto mirror and it has yet to “kill” his Tak 152. As a matter of fact, the 152 and a smaller 90mm Tak have become his most used scopes.The 11” you sold to my other compadre here in Miami some years back is wonderful, but it does not smoke any decent 6” APO much less the 7”. And yes, our skies are just as steady as yours in Tampa and better if we travel 2 hours south into the Florida Keys. Different views with different appeal given the object and observing conditions yes, but for sure killing, smoking, leaving in the dust are not something most experienced observers who have had these two side by side for extended periods of time would agree with.
 

As far as costs and since you like cars....should we all drive Tesla Model 3s because it smokes anything from vettes to lambos at a fraction of the cost? I think not.

 

When I go under the stars I want a Swiss Army knife of a scope, a scope with enough aperture and the best possible optics so I won’t have to questions If I am getting the best possible image. A scope I can roll out, plug into a 12vdc source, focus and enjoy...only a refractor has checked all of those boxes for me (excluding my sorry 178ED) in close to 40 years as a backyard astronomer and countless number of telescopes. 

I did lemon law the new C7 Vette. Got a spark on a lark, Got tired of fast cars and the cost that go with them. Also done with scopes.  Unless a nice used 18" Obsession or a very well made 18" F/6 Dob pops up local for a crazy price i don't see me having a scope again.

 

That 16" Zambuto would be a easy 1000x+ killer on the planets on my best nites. The 6" Tak runs out of light past 550x.  That Tak can do 100x per inch easy on the moon and doubles.

But planets dim out at powers above 500x in a 6" Tak. I have the money to buy most anything i want, but just don't want anything really at this time. I have had 6" APO's and a few ED's. They can't touch a bigger top notch made Newt 10" and bigger. I have world class seeing that lets big Newts shine. I also had a 178ED that was a hunk of junk with the mount image shift and a lens that would never stay on center.  I could never wrap my head around spending big money on a 6" AP or Tak when a bigger Newt just does so much better for much cheaper.


Edited by CHASLX200, 27 September 2020 - 06:33 PM.

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#99 CHASLX200

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Posted 27 September 2020 - 06:36 PM

Similar seeing here at The Swamp -- just more clouds.  A clean & collimated reflector can challenge a much more expensive APO.  Seen it myself.  Make some modest contrast & functional improvements to that reflector, and... Wow!  I've seen it at the Mid-Tier level -- I'm not paying Big Bucks for any scope.  This is a hobby.  Folks who have invested in top-tier refractors & reflectors probably have a different opinion, and that's okay.  

 

Anyway, OP, I hope we haven't gone too far off-topic from your original question.

You do any real side by sides with my 826 you bought and that 6" ED?  By heck that 826 Meade ran neck and neck with a 6" APM and Skywatcher 150ED.



#100 CHASLX200

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Posted 27 September 2020 - 06:40 PM

To be totally fair to refractors, when you start going to premium dobs the price goes up a lot. Cheap dobs sometimes have good optics but there's no guarantee, and you'll probably need to tinker on it somewhat to kill tube currents and possibly to remove strain on the secondary mirror.

Well built big Dobs are now a easy 20k or more. A 7" APO with mount runs around 20k. 8" 35K and 9" around 50k+.  Once you get into the 10" size then we are looking at home prices and something that needs to be housed.

 

A well built 16 to 20" F/6 Dob would be my top pick for planets.


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