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Before I make a mistake selling my 250PX

spaceboy

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Damo636

Damo636

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According to the specs the 10'' gathers 56% more light than the 8'' & the 12" gathers 44% more than the 10". In reality would that make the jump from 8'' to 10" more significant than a 10'' to 12"? I realise 8''-12" is the more logical jump but just curious as to how much the 10" would outperform the 8".

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tony4563

tony4563

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This is a great and interesting post.

The old saying "The best telescope is the one you are going to use the most" speaks volumes.

Portability is one of the biggest factors.

Buy a scope thats too big and cumbersome and you'll make excuses not to use it.

We are all of different shapes and sizes, but I think we all know our limits to what we can handle. I love astronomy and I love telescopes. I've bought and sold loads of scopes in my time but I've now narrowed it down to a selection of scopes that I feel I can comfortably handle to get the most out of this hobby. My aperture fever is almost complete.

Dobs: I have two. The 10" is very portable but lives permanently at my mums (she has less light pollution and a wider expanse of sky than where I live) The 12" I keep at home. It's quite heavy and large and just about reaches my limit of portability. (although I have bought, and will be modifying, a sack trolley to aid moving to and from the garage and patio area) I would sadly not go any bigger just for my back's sake. Views from the 10" and 12" are marvellous and worth the effort.

Mak: I have a Skywatcher 127 which is a fab scope for planets. However, I think I can squeeze another inch and get the 150mm at some point. This would be the max as the 180 is HUGE and my AZ4 wont take it. I love Maks for lunar and planetary work. Portable, and great views once cooled down

Refractor: I've just bought a 120ED. Superb scope to use whilst the big guns are cooling down. Any bigger than 120 and they get longer and a LOT more expensive. Also handles well on my AZ4 mount.

Spaceboy, I say go for the 12" and end it there for a Dob. Its a great scope ;)

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umadog

umadog

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But it's not about "second best." Every aperture is second best to that immediately larger, if you want to think about it that way. What matters is if the scope is known to have to have good optics, does it fit into your life style (have the right aperture/portability ratio for you), are you likely to use it, etc. It's hard to say what's best when you think about it that way and it's quite possible that, under these constraints, a 10" is best.

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spaceboy

spaceboy

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Where are you too spaceboy?I take my 300p to my local dark (ish) site with no problems,it is a little heavy but I have no problems lugging it around,if you want your more then welcome to have a go of mine to help you decide.

Thank you Taffy that is a very generous offer but sadly I am miles away in Birmingham other wise I would very much like to do a side by side comparison to see for myself if the extra 2" would be worth the size and cost.

According to the specs the 10'' gathers 56% more light than the 8'' & the 12" gathers 44% more than the 10". In reality would that make the jump from 8'' to 10" more significant than a 10'' to 12"? I realise 8''-12" is the more logical jump but just curious as to how much the 10" would outperform the 8".

Interesting point Damo. Aperture hunger aside when you look at it that was the gain in light over size really dose go in favor of the 10" but if you are gaining 56% over the 8" and the 12" gains 44% over the 10" then if what they are saying is correct that's a total of 100% light gain in the 12" over the 8" :). My math ain't so good but surely you would need a 16" to double the light gain over an 8" ;)

This is a great and interesting post.

The old saying "The best telescope is the one you are going to use the most" speaks volumes.

Portability is one of the biggest factors.

Buy a scope thats too big and cumbersome and you'll make excuses not to use it.

Thanks for your input Tony and I agree. Having a permanent setup I'm often lazy and choose the smaller 8" over taking the 10" the 30 mile drive to dark skies. Commitments at home during the week often means I have early mornings looking after a pair of wild kids so the easy option is often the first choice. When the skies permit and I have no prior engagements I'm ever keen to making the journey out but if I'm honest I've probably used my 10" dob 5 times in 12 months due to clear moonless skies landing on week days. My aperture hunger comes from wanting to make those 5 times memorable but I can't help but think if my craving for a larger scope is going to mean the 8" gets used more and the 12" only gets used 2 or 3 times a year. Again I was trying to think about portability in considering the 12" flex dob but the huge difference in price most have said the gain in 2" isn't worth it.

Stick with the 12", you'll never be happy with second best in my view, also note the portability advice given by John.

:) I have the 10"

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perrin6

perrin6

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Another option would be to make an ultralight dobsonian such as by using one support truss like the award-winning scopes made by Ross Sacket at this link : http://stardazed.com/MoonsilverIII.html

By keeping the secondary cage very light the mirror box can be kept shorter as the balance point is lower. This enables the additional benefits of large bearings and a shorter rocker box that makes the motion much more stable.

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spaceboy

spaceboy

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Very interesting design Alan.

I made up my mind today and went for option 3 which will hopefully arrive by the end of the week. I figure this will help keep me and the wife occupied during the cloud covered nights learning the ropes of photography while offering me a chance to dabble further in to imaging than my SPC880 allows. Not my ideal scenario but I have come to the conclusion a large dob is going to be unrealistic both in portability and price for the 4" upgrade I'd need to see a significant difference.

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cyg

cyg

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The dissision has to be yours, but I agree with the others that say if in doubt, wait with your 10" and explore furyther the larger appurture. Could another make/brand scope give you better flexibility with traveling/setting up?

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Veracocha

Veracocha

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I'm gonna go against the grain here and say this.....something prompted you to consider a big dob and I suspect it was Moonshane at PSP. A few weeks before I looked through Demon Barbers 15" Obsession. A month before that I looked through Albireo's 14" Dob. Then at PSP I too had the pleasure of Shanes 16" (that sounds bad doesn't it) and I now know that at every sitting with my setup I am missing an opportunity.

Like you Nick I am struggling to accept that my own gear provides me with the best views, it doesn't so I am in the same situation as you only probably closer to making the jump. Let's see ;)

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Astro Imp

Astro Imp

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Interesting point Damo. Aperture hunger aside when you look at it that was the gain in light over size really dose go in favor of the 10" but if you are gaining 56% over the 8" and the 12" gains 44% over the 10" then if what they are saying is correct that's a total of 100% light gain in the 12" over the 8" :). My math ain't so good but surely you would need a 16" to double the light gain over an 8" ;)

Remember light gathering varies as the square of the mirror size. So a 16" gathers 4 times the light of an 8". To double the light gathering of an 8" you need 11.3", near enough to the 12" quoted.

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Damo636

Damo636

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Remember light gathering varies as the square of the mirror size. So a 16" gathers 4 times the light of an 8". To double the light gathering of an 8" you need 11.3", near enough to the 12" quoted.

Exactly why i intend going for the 12" as soon as i can gather up the readies ;)

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Moonshane

Moonshane

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I'm gonna go against the grain here and say this.....something prompted you to consider a big dob and I suspect it was Moonshane at PSP. A few weeks before I looked through Demon Barbers 15" Obsession. A month before that I looked through Albireo's 14" Dob. Then at PSP I too had the pleasure of Shanes 16" (that sounds bad doesn't it) and I now know that at every sitting with my setup I am missing an opportunity.

Like you Nick I am struggling to accept that my own gear provides me with the best views, it doesn't so I am in the same situation as you only probably closer to making the jump. Let's see :)

oops. sorry guys!!

;)

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spaceboy

spaceboy

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I'm gonna go against the grain here and say this.....something prompted you to consider a big dob and I suspect it was Moonshane at PSP. A few weeks before I looked through Demon Barbers 15" Obsession. A month before that I looked through Albireo's 14" Dob. Then at PSP I too had the pleasure of Shanes 16" (that sounds bad doesn't it) and I now know that at every sitting with my setup I am missing an opportunity.

Like you Nick I am struggling to accept that my own gear provides me with the best views, it doesn't so I am in the same situation as you only probably closer to making the jump. Let's see :)

Your right about the hunger coming from the views through Shane's dob. I know you have some great EP's but I thought you were more into imaging than visual Mick ? I hope you are able to get the big dob you want. I doubt I will ever get over the hunger now I have it but budget and portability was the deciding factor. As many have said.... a good scope is one that gets used. Although at PSP I think my 250PX was out on "display only" as I spent more time in line to look through the 16" Moondob ;)

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Moonshane

Moonshane

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it's weird how things work out though and how our minds work.

I was gutted to be just pipped on a Vixen 8" f4 newt OTA on the bay. I'd have probably used this as my travel scope and sold my small frac. I think a lot of thinking originates from rubbish nights when we just sit in mentally re-arranging our kit!

all that said, I remain convinced that for me I definitely did the right thing with more aperture. it's really worth the inconvenience on those great nights.

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