10" vs 12"

[thersites]

Hi all

i know this has probably been asked countless times, but if we assume portability is not an issue, is the 12" dob a better option than the 10, or will i have more troubles with issues such as seeing and time to temp equilibrium with the larger mirror? will the larger mirror have more troubles with dancing, shimmering images? these questions may seem daft , so apologies for that, but this is such a good site that i feel almost comfortable in asking anything that bugs me before deciding on a scope.

thanks again
adam

[iceman (Mike)]

but this is such a good site that i feel almost comfortable in asking anything that bugs me before deciding on a scope.

That's great to hear! You should feel comfortable! Keep asking questions! No question is too silly, and there's heaps of people here willing to help you out.

The 12" is great for light gathering, and will show more faint detail. But as you correct assume, there is a trade-off with respect to cool-down time.

Where abouts do you live? If you live where there are large temperature differences between day and night, then even a fan will not bring the mirror near ambient by the time you want to observe. That will be more evident in the 12".

However when the seeing is good, and temperatures are fairly stable, then you'll get fantastic images from a 12".

[ving (David)]

portablitlity not an issue? 2 extra inches +

theres plenty of info here on mirror cooling too, peltiers are cool (litterally)

DSOs will look better too

[janoskiss (Steve H)]

Originally Posted by thersites

i know this has probably been asked countless times, but if we assume portability is not an issue, is the 12" dob a better option than the 10, or will i have more troubles with issues such as seeing and time to temp equilibrium with the larger mirror? will the larger mirror have more troubles with dancing, shimmering images?

Hi Adam, yes to the more troubles with 12". I've owned a 12" for a while but bought a 10" and sold the 12". A 10" Dob is a much nicer, more user-friendly scope than a 12" IMO. I'm very impressed with the optics of my 10" Saxon aka Skywatcher. Much better than the 12" GSO I used to own. Never saw anything close to the pipoint stars in the GSO that I'm routinely seeing with the Saxon. But that could well be luck of the draw rather than anything between the two models.

If you want big, join a club with a big scope (18, 20, 25"...) and use that. For your own personal use I'd recommend an 8 or 10".

[astronut (John)]

Hi Adam,
There's no right or wrong here but TWO EXTRA INCHES of aperture is TWO EXTRA INCHES OF APERTURE!!!!!
It equals to 44% more light. The one drawback is physical size.
One way around this is the Meade Lightbridge, a 12" Truss.
I have one and it fits into my Ford Laser, with plenty of space to spare.
If you're after a EQ mounted scope, then it's a different story a 12" on a EQ6 is a hefty size and weight and so a 10" on a HEQ5 would be better.

[toetoe (Peter)]

Keep in mind the price difference between the two, before you decide, see if you can catch up with other people with the two telescopes you have mentioned and see the difference for yourself. Nothing worse than jumping into a purchase and not being happy afterwards. Keep the questions coming.

[thersites]

wow, what a response! thanks to all yet again. seems like there's no black and white answer. if the choice was purely between the gso 12 and gso 10, and i'm in eastern nsw, would the 12 be better? 1.44 times the light gathering sounds very palatable, just concerned about getting a well figured mirror in such a large mass produced mirror.
adam

[astronut (John)]

Guan Sheng are the major producers of mass produced mirrors available in Australia.
I've looked through many different sizes, and I can't say I've seen a bad one yet.

[janoskiss (Steve H)]

Originally Posted by thersites

wow, what a response! thanks to all yet again. seems like there's no black and white answer. if the choice was purely between the gso 12 and gso 10, and i'm in eastern nsw, would the 12 be better? 1.44 times the light gathering sounds very palatable, just concerned about getting a well figured mirror in such a large mass produced mirror.
adam

I wouldn't worry about it. If you really that concerned then buy a hand-figured locally made mirror. In those sizes they are readily available through dealers who cater for the ATM market.

Re light gathering figures, you should really go out to a viewing night at a local club or informal observers' meeting and look for yourself to see what the numbers mean in practice. Ditto sizes of scopes: 8" vs 10" vs 12"; solid tube vs truss...

[NewToStars (Jase)]

i'm no expert. but teh difference from a 8 - 12" scope is huge.
comparing 47 tuc for example. was a big difference. in teh 12" the stars were brighter and you could clearly see more of them. they spread further out.
my 8" was still great, no doubt about that, but didn't show the same amount of stars.
both scopes were collominated that night so nothing wrong there.

get teh best scope u can afford if you are getting a dob. the bigger the apature the more you will enjoy your viewing. but remember there is the prob in size and portability. you can lug around a 8" scope and setup in 5 mins, where a 12" might take 1/2 hour.

good luck with what ever u decide.

[thersites]

i just want to be a simple visual astronomer (no photography) looking mainly at globulars, colourful open clusters, maybe splitting some colourful doubles. surely the 12 would be better than a 10, regardless of cumbersomeness and mirror cool down? insert thoughts here
adam

[wavelandscott (Scott)]

It is not in total "black and white"...and there is no "easy" one size fits all answer to your question. Better is a realtive term...better in what way?

Yes, the 12 inch will gather more light and this is a good thing...you should be able to see "fainter" objects...

However, cumbersomeness and cool down (or lack of cool down) will matter in how often and how much you will view.

All other things equal size will win but sometimes the "other things" can have much more impact on how you might use the scope.

I'd encourage you to go out and try some 10s and 12s before you jump in and buy...

[rogerg (Roger)]

Make it simple for yourself, just buy one and learn for next time.

Flick a coin if you like.

Personally, for my first telescope, I didn't care too much about practical reasoning, I wanted a telescope that looked like a real telescope, and the biggest I could afford. That's just me. And hence I say just pick one, any old one that you happen to lean towards for whatever impractical reason as both 10" and 12" are great!

Roger.

[GrahamL]

I have a 10 " and have had a look through /at glen cs nice 12 " dob
a couple of times .

The 10 is portable, down the hallway down a few steps to the backyard isn't to diifficult, and the back seat of most cars will fit it in there .
The views are great through this scope .

The 12 is also portable , down the hallway and backsteps does look an ask though at a glance it is a physically large piece of telescope
The views are great and noticably brighter in the 12".

Good luck both will be a long time friend whichever you choose
time over for MY situ ... think i'd go a 12 "truss dob of some type .. or maybe a 13.1 .. or maybe a

[thersites]

thanks for the opinions everyone.
i am learning to deal with this uncertainty in astronomy, i guess this is good since we don't know what 80+% of the universe is made up of!

adam

"someone make my mind up for me, decisions will only put me to sleep"

[norm]

10" GSO deluxe dob or 12" Deluxe Lightbridge. Thats my 2 cents worth!

[ballaratdragons (Ken)]

Originally Posted by NewToStars

you can lug around a 8" scope and setup in 5 mins, where a 12" might take 1/2 hour.

Huh?

They both take the same time to set up. about 3 - 5 mins.

Unless you are carrying it out of an upstairs flat, down the hallway, down the staircase, out thru the bottom hallway, out the entrance and around the back of the building thru the carpark.

I use my 12" quite a lot and it is kept in the house. I have to carry it down a few stairs, turn corners etc. and it takes me 3 - 5 mins to be completely set up.

Cool down time for general visual observing with a 12" is about half an hour, if I use the fan I cut that down to about 10 - 15 mins. During that 10 - 15 mins I am carrying out my table, EP case, power lead, etc. By the time all my gear is out there the scope is cooled enough for observing.

Yeah, the 12" is heavier and more awkward to turn corners with, but it wins on faint fuzzies. Worth the Hernia

[monoxide]

hehe, i love this forum.. you can ask any question you like and end up more confused than you were before you asked it.

i bought a smaller scope to start with and have only just ordered a 12".
there was a graph plotted for cooldown time with the 12" mirror, it was around 30 minutes with the fan on which i allow for a scope half the size anyway. if theres that much temperature difference between day and night then a 10" isnt going to magically be a whole lot better, use low power until it cools if you have to.

i cant really comment on 10 vs 12 but id say the difference in size would go from 'oh nice' to 'woah' hehe
either way you will have a blast.
i just know down the track id be kicking myself, in a few years time the extra $200 or so isnt going to matter if your still happy with the scope.

with a dob your limited to visual observing only anyway and the 12" will perform better than the 10" (unless im missing something

in saying that just remember the best scope is the one you will use most, doesnt matter if its a tasco or sdm.

[xelasnave]

Not my saying but I only borrow from the best...
"the only silly questions are the ones you dont ask"
Go for the 12 inch or you will always be wondering...
and another saying..
A bad decision is worst than no decision or indecision.
I had, (er actually I still have it) a 235mm not a 10inch but close... the 12inch beats its socks off.
The optical tests I have done with my 12inch tells me that anyone who levels critism at the optics have extrodinarily high expectations.
BUT the larger the app the longer the clouds will stop you from using it .. and believe me once purchased that will be your only concern .
Good luck lets move on to what additional EP,s to get .
best wishes alex

[xelasnave]

Whatever you decide please consider adding baffels or flocking this is not a problem confinded to any particular app but the improvement to a good scope takes it to a higher level. Chalk and cheese comes to mind. I like an extended baffle past the secondary like the approach they take with hubble...dont let the fact they had teething problems convince you they dont know what they are doing... and if you go a truss dob style get it a nice black dress ..very suitable evening wear for a lady even better for a scope.
alex