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Aperture Fever? 8" vs 10" or 12"

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#51 Asbytec

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Posted 27 January 2019 - 10:51 AM

Maybe one of my lingering memories is viewing the Helix nebula through my homemade 6" f/4ish Newtonian (that was supposed to be f/6 until I went too deep) from the Tehachapi mountains in southern California circa 1975. 


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#52 aatt

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Posted 27 January 2019 - 02:21 PM

Dont  bother with a 10", go 12".There is a difference between the two, but not enough to make it worth your while.I remember getting a loaner 8" when my primary scope was a 6" years ago. i was expecting a big difference and I was disappointed that things were not much brighter. 


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#53 macdonjh

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Posted 27 January 2019 - 02:42 PM

There is some truth to the saying that a scope being used is the best scope. Ergonomics such as set up, eyepeice height, comfort, and ease of operation is one (or many?) of the reasons a scope gets used. A lot.

My no frills 6" CAT is much simpler than my previous C11. I am often amazed how quickly I am seated comfortably and observing in such short order. For that reason, one of them anyway, my 6" gets used a lot. No regrets. Well, a little...but, thus far, the 6" is still my most used scope. Primarily because of ergonomics.

My solid tube 12" Dob rearranged the pictures on my wall when taking it down the hall and out the door. I'm half kidding. Sometimes I bang the 8" solid tube focuser on the door jam. Not kidding. smile.gif

Yup, I settled on an 8" scope to use at home because I could use a smaller mount than my G11, which takes twenty minutes to set up and take down.  Besides, at home I only observe the moon, planets and double stars.  DSO aren't satisfying to me from deep in my white zone.  When I go to our club's dark site, I'm happy I have 10" and 14" scopes to choose from.

 

I remember an account told by Harold Hill, an esteemed British lunar observer, when he had chance to compare his old 6.25" reflector with his 10" F10. Although the detail in the 10" was much brighter, Harold admitted that everything visible in the 10" was also visible in the 6.25". I suppose this illustrates just how powerful a tool a 6" Newtonian really is. It also begs the question "Is the increase in size, and the more cumbersomeness of the larger scope, going to enhance your over all enjoyment of lunar observing? Or is it going to put you off?

May be the 8" used with a binoviewer would be the best way to go as far as lunar & planetary observing goes!?

I wonder if Harold Hill would have made the same comments if he were observing galaxies?  The moon is a very bright object with high-contrast features.  Quite different from observing faint fuzzies.

 

No point in going from an 8-10". Going from an 8" to 12" will definitely be an improvement, but I feel you really need to step up to a 16" + to really see a difference.

I disagree.  To my eye DSO in an 8" scope are still gray and lacking in detail.  A 10" scope; however, starts to make objects look bright and detailed.  I was quite happy using my C11 and 10" Parks hybrid for seven or eight years total.


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#54 Starman47

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Posted 27 January 2019 - 06:18 PM

Another point to consider: where do you want to end up with telescope purchases? Fo instance, if the 12 inch is your upper limit, then go for it rather than the 10 inch. But consider that a 16 is a giant step up from 8 inches. So an intermediate step may be required. 


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#55 Cosmosphil

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Posted 28 January 2019 - 11:49 AM

If the OP is still around I wanted to mention that several books including classics like "The Dobsonian Telescope" by Dave Kriege & Richard Berry.   Or,  "the Backyard Astronomer's Guide"   by Terence Dickinson & Alan Dyer

offer some very good advice about searching for that ever ending Super scope!   They warn about larger and large scopes.   Even Kriege, who had made his mark with his big Obsession designs, talks about what kind of life style do want with your telescopes.   He sets up various scenarios with various sizes of scopes.   Aperture fever can lead to all sorts of problems and issues that many who are afflicted do not even think about.   

Some here on CN like Jon and a few others have giant scopes resting already to go in a garage and can pull these beasts out on a whim into 6 or 7th mag skies!   Ahhhh, the dream.  These folks are blessed.    But for some of us, age, health issues, work loads, family loads, etc limit us to making some serious choices on what kind and size of scope we can actually use in the real world.    

I also find as I get older that appreciating the very fact of being outside with ANY scope even on the sidewalk in front of my house with street lights a blaze and passing traffic is still far better than sitting inside watching stinking TV!   

Hauling a large dob 50 or 100 miles out of the city just to see fainter & fainter stuff just gets harder and harder.    So, I would say to the OP if you're young.   If your, in good heath.  If your family obligations are such that you can really give the big dob lifstyle a whirl then go for it.   Get a 12" or a 20" or a 30" !!    shocked.gif   Just remember there are trade offs in all hobbies and advocations.       


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#56 Jon Isaacs

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Posted 28 January 2019 - 12:22 PM

I disagree.  To my eye DSO in an 8" scope are still gray and lacking in detail.  A 10" scope; however, starts to make objects look bright and detailed.  I was quite happy using my C11 and 10" Parks hybrid for seven or eight years total.

 

 

The difference between an 8 inch and a 10 inch is about 0.5 magnitudes.  That's significant when viewing a particular object.  But the objects themselves range many magnitudes, i don't see how one can say DSOs are gray and lacking in detail in an 8 inch but start to become bright and detailed in a 10 inch, the views of nearly all objects are more the same in these two scopes than they are different. 

 

In reality,  most objects are dim and lacking in detail.. 

 

Jon


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#57 gwlee

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Posted 28 January 2019 - 02:17 PM

Nice to know. What sort of problems did the light weight ones have? Would you need to inspect it yourself if a big name poster did so first?

Here’s an example. My bespoke 34# 8”f6 from Famous Maker was far too shaky to be acceptable to me for nightly use, much shakier than the inexpensive 41#, 8”f6 Dob that I intended it too replace. Weight and balance issues limited it to a Rigel QuickFinder or equivalent. Weight and balance issues limited the scope to a proprietary 1.25 focuser that was terrible. These were the three main problems. The Zambuto optics were great though. 

 

It met its specified weight, and it would have been fine for an observer that needed an ultra light scope light that could be disassembled and transported once a month to his club’s dark site in the passenger seat of Mazda Miata, but the design tradeoffs made to achieve the desired weight and transportability severely compromised the scope for other purposes. Like most of the ultralight genre that I have encountered so far, it was a one trick pony. 

 

After two years working with this scope, working with Famous Maker, and testing it side-by-side with less expensive productiion scopes, I replaced it with a 6”f8 scope that also weighed 34#, had a better 1.25” focuser, and it cost about 1/8 as much. I haven’t given up on buying or building a larger scope with equivalent portability, but I am a lot more cautious these days. 

 

Weight can be easily and objectively determined by simply putting a scope on a bathroom scale, so I would be confident in the measurements made by experienced and thoughtful CN reviewers. Furthermore, I would be witin my rights to return a bespoke scope to Famous Maker that did not meet its specified weight and request a refund.

 

Shakiness is very difficult to define, specify, or measure objectively, but most agree there are few worse faults. Everyone has their own subjective minimum standard for stability, so if a well known experienced and thoughtful CN reviewer reported testing a 30# 10” Dob and finding it was satisfactory in all respects, I would be thrilled. Thrilled enough to contact him by PM and ask a lot of questions. If the answers were encouraging, I would definitely put this scope on my short lists of scopes to evaluate, but would not purchase it without doing a thorough hands on evaluation myself, which would likely require to travel to the manufacturer’s facility, a tradeshow, or a major regional star party. 


Edited by gwlee, 28 January 2019 - 03:01 PM.

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#58 Dana in Philly

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Posted 28 January 2019 - 02:42 PM

I love my Sky-Watcher Collapsible 8" Dobson...but I am just wondering about stepping up to a 10" or 12 " Dobson in the future.  I primarily enjoy lunar and DSO viewing...and was looking at possibly upgrading to either the Explore Scientific 10" Truss Dob or 12" Truss Dob.  Both weigh about the same as my Sky-Watcher 8".  Is the WOW factor for visual viewing worth the upgrade?  All scopes are f/5. 

Fairly thorough unboxing, review, pros and cons discussion, and modifications/improvements thread, for the ES 10" truss dob has just run its course right over here, if that's of any use to you:

 

https://www.cloudyni...nian-reflector/

 

Not sure how much of a jump it'd be from an 8".


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#59 Starman47

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Posted 29 January 2019 - 11:05 AM

You may also want to just attend a star party and look through various telescopes. Then you can make an informed decision. Which may be better than reading posts. 

 

Not to say there is not a lot of wisdom in CN posts. There is much to be learned. And just FYI,  a few of my problems have been solved by the input from the CN community.   But in this type of question, experience may be the best teacher.


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#60 starcanoe

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Posted 29 January 2019 - 02:11 PM

Another point to consider: where do you want to end up with telescope purchases? Fo instance, if the 12 inch is your upper limit, then go for it rather than the 10 inch. But consider that a 16 is a giant step up from 8 inches. So an intermediate step may be required.

 

Good point...but just to muddy the water some more...if you highly expect to get a big/bigger scope down the line...then it might make sense to just get an 8 incher (thats almost a grab and go scope depending on your life situation). A ten incher starts to be a hassle...and a 12 inch even more so (but IMO not baddd).

 

Then when you get the big/bigger second scope...your smaller scope makes more sense...rather than having one that is sort of pain and one that is a pain relatively speaking.



#61 vdog

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Posted 29 January 2019 - 04:32 PM

For me personally, when I decided to upgrade my 4.5" I figured that if I were going to spend the money, I would go as big as I could afford and at least double my aperture, so I skipped right past 6" and 8" to 10."   I don't regret it; it's a huge difference in what I can see and do, and I've still got the little dob for a grab-and-go option.

 

So I would say if you can afford the 14", and limited portability is not a factor, go for it.



#62 GeneT

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Posted 29 January 2019 - 05:13 PM

Going from 8 to 10 is not going to be a major jump, so I'd only go that way as a replacement, not as a complementary scope.

 

I'd go to 12" and that should be a nice bump. Globulars in particular will be a lot more resolved.

I agree with this. Also, a 12 has twice the light gathering capability of an 8. 



#63 jnmacastro

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Posted 29 January 2019 - 06:44 PM

Going from 8 to 12 is a good jump.   My CFO reluctantly okayed my purchase of a 12 inch dob (I had an 8 inch).  She likes globs.  After seeing M13 (and other globs) in the 12 inch, she said it was a good purchase!  smile.gif

Jeff


Edited by jnmacastro, 29 January 2019 - 06:45 PM.

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#64 MalVeauX

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Posted 29 January 2019 - 07:58 PM

Being that you can now get a 16" from ExploreScientific without a custom job price tag that is fairly lighter weight (reasonable) and/or the Meade Lightbridge 16" (great, but quite heavy, not a simple task to move this thing), that seems to be the logical means to upgrade and see a significant difference without it being a ladder-job joke.

 

Very best,


Edited by MalVeauX, 29 January 2019 - 07:59 PM.


#65 TOMDEY

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Posted 29 January 2019 - 08:11 PM

You may also want to just attend a star party and look through various telescopes. Then you can make an informed decision. Which may be better than reading posts. 

Not to say there is not a lot of wisdom in CN posts. There is much to be learned. And just FYI,  a few of my problems have been solved by the input from the CN community.   But in this type of question, experience may be the best teacher.

Indeed, lot of wisdom there!

 

Most all of us have an active local club not too far away. And most all of those have monthly meetings, field activities, and shared/personal equipment galore! They will be happy to discuss and demonstrate. It's a bountiful resource to be availed! Can also befriend local folks who are into the same avocation... LOT to be said for that!    Tom

 

DISCLAIMER: Sigh... I still belong to ours, but became substantially inactive, once I built my own rural observatories and got sorta burned out being very active in multiple NFP Orgs... found I was doing very little astronomy, at that point! There's a happy-medium in there someplace?    Tom



#66 25585

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Posted 29 January 2019 - 08:37 PM

Being that you can now get a 16" from ExploreScientific without a custom job price tag that is fairly lighter weight (reasonable) and/or the Meade Lightbridge 16" (great, but quite heavy, not a simple task to move this thing), that seems to be the logical means to upgrade and see a significant difference without it being a ladder-job joke.

 

Very best,

If the OP wants solid tube, 12" is the limit. 16" any make will be truss. 

 

Generally a point on mirror size and weight - handling, cleaning and eventually recoating will be proportionately more difficult. With recoating, if shipped somewhere it's riskier and more expensive as size increases.    


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#67 gwlee

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Posted 30 January 2019 - 01:05 PM

You may also want to just attend a star party and look through various telescopes. Then you can make an informed decision. Which may be better than reading posts. 

 

Not to say there is not a lot of wisdom in CN posts. There is much to be learned. And just FYI,  a few of my problems have been solved by the input from the CN community.   But in this type of question, experience may be the best teacher.

Clubs and star parties are a good places to get a little hands on exposure to a variety of scopes. It’s excellent advice for metro observers who most likely have a club nearby, but less viable for rural dwellers.

 

For rural dwellers without a club are star party within reasonable driving range, suggest doing your best to sort out the conflicting advice on CN. Then buying a used scope off Craig’s List, which can easily be resold for what you paid if it turns out to be too big or too small for your needs.

 

I have bought and resold two popular scopes in excellent condition on CL in my rural area in the last two years for about 50% of new cost, and I am searching for my third now. Might take a few months in this rural area to find what I want though, but that’s to be expected. 


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#68 stargazer193857

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Posted 30 January 2019 - 03:20 PM

I went to someone selling a 12". I got to lift it up and look through it and look through his 80mm binos. I learned that my 50mm binos showed M31 about as well and found it much faster too even hand held. I also got a wow effect from the 12" vs my 8", even with the dirty, out of collimation mirror. And I learned that I could lift the parts of the 12", but each was quite hefty and bulky. I hurt my back by not keeping it straight for just a second. I like the aperture, but my health needs me to stay smaller. The 12" owner was a tall fit farmer who wanted a 9.25" SCT instead.

I also borrowed an 8" SCT from a club. It was on a heavy GEM. It hurt my back a few times, but I got my best view of the Orion Nebula I've ever seen. My reward for braving the cold.

An 8" dob is hefty in one piece. I carry it 50 yards when I need to. But it is just enough trouble that I stayed in and missed more than a few good nights. A 10" is noticeably more but not bad at all in two pieces.

I am 150 pounds, thin, not so young, and have several old injuries. My fit 150 pound 28 year old friend used the 8" more than I did, but even he missed some good nights rather than take it out. He is willing to move 12" Scopes and agrees with me that 14" is too heavy, even though he was shopping for 16" at first.

Edited by stargazer193857, 30 January 2019 - 03:21 PM.

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#69 25585

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Posted 30 January 2019 - 04:41 PM

Lot to be said for an 8 inch C8 CPC kit. Astronomics has deals from time to time. 



#70 Achernar

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Posted 31 January 2019 - 06:03 PM

If you are looking for a dramatic improvement on most but not all objects that would be visible in both, get the 12-inch. Yes you can see a difference in the views between an 8 and a 10-inch, and yet again between a 10 and a 12-inch. It won't be dramatic however, but the difference between an 8 and a 12-inch is much greater. You'll get more than twice as much light gathering power, and that will improve the views of many objects you can see through an 8-inch, and show others that won't be seen through an 8-inch. However, if you are going to transport it in a car, the truss-tube or collapsible Dob is the option you want. If you have a bigger vehicle, or do not need to transport it to use it under at least reasonably dark skies, a solid tube Dob might be a better, and a less expensive option too.

 

Taras


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#71 stargazer193857

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Posted 31 January 2019 - 06:26 PM

I don't think you can have your cake and eat it too. The choices are less capable but less unmanageable, much more capable but much more unmanageable, or in between on both.

#72 stargazer193857

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Posted 31 January 2019 - 06:32 PM

M13 resolves in an 8" at 200x, but it is averted vision. Same eyepiece at 10" resolves it direct vision. This is at a dark site. Could 160x be the bright ticket for 8"? I don't know.

I've not directly compared 10" and 12", but I know the 12" shows a bright M31 at 6mm exit pupil.

#73 Jon Isaacs

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Posted 01 February 2019 - 06:46 AM

An 8" dob is hefty in one piece. I carry it 50 yards when I need to. But it is just enough trouble that I stayed in and missed more than a few good nights. A 10" is noticeably more but not bad at all in two pieces.

 

 

I have yet to understand why many move their Dobs in one piece.  It just makes what could be an easy,  relaxed job more awkward and difficult.  There are unique situations like Gary's where he moves it frequently throughout the night and has quite a distance to go .

 

But for setup and tear down, it's just one more trip and takes but a minute or so. 

 

I don't think you can have your cake and eat it too. The choices are less capable but less unmanageable, much more capable but much more unmanageable, or in between on both.

 

But. .  With a bit of thought and planning, working with the scope rather than fighting it (see above ) the difficulties associated with larger scopes can be reduced .

 

Jon


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#74 daquad

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Posted 01 February 2019 - 01:37 PM

M13 resolves in an 8" at 200x, but it is averted vision. Same eyepiece at 10" resolves it direct vision. This is at a dark site. Could 160x be the bright ticket for 8"? I don't know.

I've not directly compared 10" and 12", but I know the 12" shows a bright M31 at 6mm exit pupil.

I don't fully agree with this.  I am able to resolve M13 with my 6" ED refractor with direct vision in my 5.5 mag skies.  But then again, how do we define "resolve.?"  To me, in the 6-inch the core appears not only mottled, but individual stars are apparent.  Same is true for M92, M15, M22.   I should think an 8" Newt should be able to do the same.

 

Dom Q.


Edited by daquad, 01 February 2019 - 01:44 PM.

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#75 DNA7744

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Posted 01 February 2019 - 11:13 PM

Well after much lively discussion, and with consultation with my finance minister (spouse)...I have decided that the ES 12" truss Dobson is in my future. Will be looking on CN and other dealers for a deal and hope to have finances in place within a couple of months! My 8" Sky-Watcher will be my quick set up scope and the ES 12 will be my detail scope when good stable weather prevails! Thanks for all the comments!
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