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How much increase in aperture to see a difference?

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#151 Binosaurus

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Posted 07 July 2017 - 11:54 AM

I enjoy hanging out here because people are more likely to talk about lunar & planetary observations at 5" or under apertures here than in the reflector or cat subforums, ostensibly because here, unlike elsewhere, larger apertures are largely unaffordable. As I have a 5" reflector and next-to-no interest in anything larger, this is a better fit for me than being part of one more discussion of whether to buy a 12" or 16" dob for DSO, a task for which I prefer binoculars. What I'd really prefer would be a small (5" and under) scope subforum. :D


Edited by Binosaurus, 07 July 2017 - 11:55 AM.


#152 spencerj

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Posted 07 July 2017 - 12:16 PM

 

 

I thought I wanted a 140 class APO.  The image and fantasy of it has been kicking around in my mind for most of the year.  They're such nice looking telescopes - what a telescope is supposed to look like.  At a major star party a few weeks ago, I found a beautiful 140 - a very well-known top quality model mounted to atop a big G11 and I asked the owner if he would please show me M15 in it.  He was proud to do so and we looked.  He raved and I was silent.  I thanked him and walked back to my premium 16" Dob.  Looked at M15 in the 16 and raved to myself saying I'm so glad I have the 16.  For the same amount of setup and money, what a difference!

 

 

I tried again a few weekends ago to get a good look through a high end refractor.   Never did get the opportunity, it was the same old story I've seen every time there are higher end refractors around.  The owner was always doing something with the alignment, setting up for imaging, etc.    Observing...not so much.  I don't hang around waiting for a look.    I'll catch a look through a premium refractor one of these days...maybe it will blow my mind. 

 

I don't know, the refractor forum also seems to be a place where people go to tell others their scopes are too small - nearly worthless - or to tell us all about how great their large instrument is.  I keep reading it on a very repetitive basis.  

 

Yet there is no mass migration out of refractors, no rush of TEC160's and AP Travelers hitting the classifieds as people realize they've been duped!   Any delusions one has about refractors dissipate quickly when you fork over the money for one.  Of course you're thinking about how much the money could buy in a Newt, or a Mak, or a helicopter skiing vacation, new kitchen, mortgage payments, etc.
 

I set up and take down next to friends loading behemoths into their vans all the time.  I'm often happy to show up with a 120mm refractor, or even 100mm, just a different choice.

You know, I hear how great these scopes are, yet folks don't offer views through them to other amateurs much.  And they don't bring them out to more casual observing from what I have seen over the decades.  Perhaps this is a way to maintain the aura/mystique/mythology associated with them.  Amusingly, I'm the one who brings out a 110ED for club events sometimes...haven't seen any other refractors at them so far.

 

As for mass migration, I wouldn't expect it as premium refractors are primarily imaging scopes.  Nevertheless, they seem to make the rounds on the used market with far greater frequency than big Dobs so folks don't seem to have trouble parting with them.

 

That is surprising.  If you exude the same attitude in person as you do in this forum, it is difficult to understand why people aren't falling over themselves to give you a chance to insult their personal telescope choice.      


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#153 Redbetter

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Posted 07 July 2017 - 03:23 PM

 

That is surprising.  If you exude the same attitude in person as you do in this forum, it is difficult to understand why people aren't falling over themselves to give you a chance to insult their personal telescope choice.      

 

 

Actually, I don't insult people's scopes here or in person, but I do stay realistic about what one can expect to see.  Unfortunately, if one doesn't quietly accept wild claims about how a small refractor provides better images and detail than a decent scope with twice its aperture, and challenges the same, then it is viewed as an insult here.  ohmy.gif    Oh well, so be it.

 

Even when I had a premium refractor next to me (back in the days when I only had an 8" SCT) I never was offered a look.  The owner was mostly busy with imaging so I didn't bother him, although I was curious.  I have seen this play out in different ways at several major star parties.  There are the imagers, and there are the visual observers.  I respect the imagers' investment in time and resources and assume that they might have limited dark sky time.  So I don't go asking for views through their gear. 

 

When I was just using an 8" SCT, I would end up swapping views and targets with medium and large Dob, Newt, and SCT owners nearby and we had a good time...while the imager did his thing with the frac.  The same dynamic plays out whether I am using a large or small scope...even when that small scope is a 110mm refractor.   And it was the views that I had through large Dobs that prompted me to move that way long ago. 

 

There is nothing wrong with preferring the view, ergonomics, etc. of one type over another.  In similar apertures a good refractor has a substantial edge over other types in my opinion and aesthetically it is hard to beat.  But one should also accept that there are limitations as one begins comparing to larger apertures. 


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#154 Sockrateez

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Posted 07 July 2017 - 03:48 PM

I have an AP 130 F/6 which I use for visual observations primarily of double stars although anything is game. I have read so many impressive things about CFF I have thought about getting one. What is your experience in terms of the need for increased aperture moving from a 130 refractor to see a difference? Is a move to 140 enough or would I really need to get a 160 to make a visible difference?

I think it all depends on which end of the telescope you look through.



#155 infamousnation

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Posted 13 July 2017 - 03:25 AM

I enjoy hanging out here because people are more likely to talk about lunar & planetary observations at 5" or under apertures here than in the reflector or cat subforums, ostensibly because here, unlike elsewhere, larger apertures are largely unaffordable. As I have a 5" reflector and next-to-no interest in anything larger, this is a better fit for me than being part of one more discussion of whether to buy a 12" or 16" dob for DSO, a task for which I prefer binoculars. What I'd really prefer would be a small (5" and under) scope subforum. laugh.gif

I'd be interested in a small scopes forum.


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#156 Jon Isaacs

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Posted 13 July 2017 - 04:12 AM

 

 

I agree that globulars look best at larger apertures. I like my 10"  Dob for those. However, my 140 APO does a very good job on the brighter ones like M15. Perhaps the one you looked thru was not as "top quality" as was assumed. Or perhaps you require greater magnification in order to get any "wow" out of objects.

 

If one looks at M15 in a perfect 140 mm and then walks over to a decent 16 inch, I think the difference is quite stunning.  There's a factor of almost 3 in resolution and about 8 in terms of light gathering, that's more than 2 magnitudes.. 

 

Jon

 

Yeah, I know. So...?

 

 

This what:

 

One should not be surprised when some one was not impressed with the views of a bright globular in a 140 mm when they had been viewing it in a 16 inch.. even the most perfect 140 mm will pale in that comparison..

 

Jon



#157 Vondragonnoggin

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Posted 13 July 2017 - 04:50 AM

Well, it depends on the eyepiece used in some cases. Having seen the horsehead in an AT72 ED I'm inclined to think that the refractor owners eschewing what great objects are visible in their modest refractors haven't explored opportunities provided by electronic means without the hassle of goto, tracking, dark skies, and PC help.

 

120ST and Night Vision eyepieces with narrowband filters has afforded me views well beyond what traditional eyepiece/scope combinations provide. All in a form factor fit for easy views with zero hassle setup.

 

It's a game changer for a substantial introductory price. 6 of 1, half a dozen of another, take your pick on how you want to observe with modest equipment and a modest scope and mount.


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#158 mogur

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Posted 13 July 2017 - 06:58 AM

 

 

 

I agree that globulars look best at larger apertures. I like my 10"  Dob for those. However, my 140 APO does a very good job on the brighter ones like M15. Perhaps the one you looked thru was not as "top quality" as was assumed. Or perhaps you require greater magnification in order to get any "wow" out of objects.

 

If one looks at M15 in a perfect 140 mm and then walks over to a decent 16 inch, I think the difference is quite stunning.  There's a factor of almost 3 in resolution and about 8 in terms of light gathering, that's more than 2 magnitudes.. 

 

Jon

 

Yeah, I know. So...?

 

 

This what:

 

One should not be surprised when some one was not impressed with the views of a bright globular in a 140 mm when they had been viewing it in a 16 inch.. even the most perfect 140 mm will pale in that comparison..

 

Jon

 

I'm impressed. That's all that matters to me.



#159 planet earth

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Posted 13 July 2017 - 09:41 AM

 

 

 

 

I agree that globulars look best at larger apertures. I like my 10"  Dob for those. However, my 140 APO does a very good job on the brighter ones like M15. Perhaps the one you looked thru was not as "top quality" as was assumed. Or perhaps you require greater magnification in order to get any "wow" out of objects.

 

If one looks at M15 in a perfect 140 mm and then walks over to a decent 16 inch, I think the difference is quite stunning.  There's a factor of almost 3 in resolution and about 8 in terms of light gathering, that's more than 2 magnitudes.. 

 

Jon

 

Yeah, I know. So...?

 

 

This what:

 

One should not be surprised when some one was not impressed with the views of a bright globular in a 140 mm when they had been viewing it in a 16 inch.. even the most perfect 140 mm will pale in that comparison..

 

Jon

 

I'm impressed. That's all that matters to me.

 

Exactly waytogo.gif

 

Sam



#160 salico

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Posted 13 July 2017 - 10:17 AM

feel the same with my ED120 binocular telescope: Of course, large reflectors show more, but I'm simply amazed by the pinpoint wide field views of DSOs



#161 Max Power

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Posted 15 July 2017 - 02:07 PM

Where small fracs can really strut their stuff is on planets.
My 90mm -53 triple can see all the major features on Mars at up to 350x.
About the same views as an average 6" dob. Much smaller and lighter but at a cost for the higher quality optics.
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#162 BigC

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Posted 17 July 2017 - 10:43 PM

Going from 130 to 140 will give a small improvement and I would do it only if the cost was also small.

 

The different view in a 100mm vs. 120mm is obvious.

 

As for the apo circulating more than big Dobs that is surely related to the phyical size.Shipping costs for the individual can easily approach or exceed the price of the used Dob.




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