10" versus 12"

[Dog Star]

G'day all. Have been happily peering through my 20 X 80 nokkies for about 12 months now but feel myself being gradually consumed by the irrational idea of buying a telescope. As I've been thinking about it for a while, I've come to the conclusion that a 10 or 12 inch dob would suit my purposes quite nicely. Given that the price difference between the two can be up to a couple of hundred dollars, my question is this - Does the extra money translate into measurably superior viewing? My gut feeling is to go with the 12 inch. Is that rational or is that just aperture envy? Any thoughts or comments would be appreciated.:shrug:

[programmer]

Budget, luggability, transportability. If none of these is an issue go the 12 inch :)

[omnivorr]

..buy the 10" now... at the rate the prices are going (and new truss jobs coming) you'll get the 12" for $300 in 6 months ;)

[Ian Robinson]

I've a 10" f4.66 newt , and it's akward enough to getting in and out the Pajero , seeing in my backyard is hopeless.
Difference in it between a 10" and a 12" is not a lot in resolving power, or reaching power (faintest star you can see).

12" has only 1.5 as much area to collect the photons than a 10" , a 14.5" has 2.1 as much area to collect the photons than a 10".

Under excellent seeing
Limiting vis mag is 14.5 for a 10"
Limiting vis mag is 14.9 for a 12"
Limiting vis mag is 15.3 for a 14.5" (nearly 1 mag gain over the 10") , well even if you can't get within a magnitude of these in reality in most cases , you get the picture. Uptake ... not much between a 10" and 12".

When I upgrade , I'll go to a 14.5" newt , seems a good size to me.

[Jeff]

Just expanding on Omnivorr's comments:
- 10" f/5 dob tube will typically fit across the backseat of most medium cars
- a 12" dob tube typically won't

So if you want portability for the occassional dark sky site visit (a treat not to be missed, especially in the mild/warm months), then I would recommend a 10" conventional dob.

If you go larger, I would suggest a truss-dob (eg. 12" f/5) ... but they cost more. I have compared my 10" Lightbridge truss-dob and a 12" GSO conventional dob side-by-side on DSO's at a star party and could not see any differences except for some very faint galaxy smudges which were a little easier to pick up in the 12".

Hope this helps.

[glenc]

I would go for the 10" and head north out of Alice on new moon weekends.
I used to visit my parents in Alice and drive about 15km north for dark skies.
The 12" shows more galaxies but it is less portable.
I use my 10" for weekends away and my 12" in an observatory when I am home.

[Zuts]

Hi,

I used to have a 12 inch GSO DOB, now sold. However, it used to fit no problems into the back of my Hyundai Excel with the back seat down; and fitting through the hatch.

The front seat was still useable so still enough room for my daughter to come with me.

Awkward I know, but doable.

Paul

[Dog Star]

My thanks to all who have responded. I knew I could count on IIS members for helpful advice. Portability of this thing shouldn't be a problem as my position 15 km SW of Alice in a semi rural area means I'm getting nice dark skies so the majority of my viewing should be of the backyard variety. A 20 meter shed right next to me stuffs the Eastern horizon somewhat but I can always drive about 1 km down the road to the claypans where the viewing is virtually horizon to horizon. I've got the trusty old Falcon uterus and I figure there's enough room in the back of that (1650 mm with the tail gate up) to transport most scopes.
So it really does come down to a simple question of whether or not an extra 2 inches of aperture is worth another 200 or so dollars.
Had to chuckle at Ian's reply though. Here's me trying to avoid aperture envy and a man obviously riddled with it slyly advises me to go with a 14.5 inch!:rofl:
All the same Ian, what you said and the figures supplied confirm this as actually very cunning reasoning. I'd be very interested in hearing from you if you do upgrade, but I think that size might exceed my budget:sadeyes:
Thanks to all for posting. You've given me a bit more to think about.:thumbsup:

[Ian Robinson]

Who ... ?? me ??? :D

[dannat]

How can you beat $299 for the 10" from andrew at the moment??:screwy:

[glenc]

Go for the 12".

[Gargoyle_Steve]

Hey there Dogstar! :hi:
I guess you got my pm about the prices on the dobs at Andrews over the weekend after all.

I reckon 10" or 12" you'll love it, but whatever you do don't get one with a Rack & Pinion focuser, get at least the standard Crayford, the R&P's are so frustrating to reach a clear focus with.

Having said that I'd really recommend that you get a scope with the 10:1 Crayford on it, when you're chasing clean focus at higher magnifications to see planetary detail, etc, you'll want it.
ie go 10" at $499, or 12" at $749
(I originally had the standard Crayford myself and had to spend the extra money to buy the 10:1 separately and upgrade it later.)

You'll be interested to hear that our other brother had his superannuation payment come through yesterday, we were on the phone this morning and have ordered for him a 10" dob with 10:1 Crayford ($499), hoping to have it to take out to Ron's place this Saturday night. As a very vague guide, freight to Brisbane from was quoted at $90 for the 10" package.

If we manage to fit both our scopes in next time we come over to the Alice we can all get together and have our own star party, we could call it a "3 dob night"!
:lol:


Here's my 10" and 12" dobs side by side - the difference doesn't look like much, but it comes into play a bit when moving it. Still, when all else fails, remember the Golden Rule....

Aperture Rules!

[Screwdriverone]

I agree with Steve,

I have had my eye on the 10" Super Deluxe for $499 for a while now, with drool at the corner of my mouth and wondering all the time how long I can wait and whether I can use my upcoming tax refund (if I get one) to buy one.

Considering the extras you get with it:

Super Deluxe version includes a right-angle correct image 8 x 50 finderscope, 2" Crayford style microfocuser with 10:1 fine focusing and a 2" to 1.25" adaptor, fan, GSO 6mm, 9mm, 15mm and 25mm 1.25" Plossl eyepieces - and a bonus SP32mm 2" eyepiece, too!

I am just trying not to belt myself over the head repeatedly with a piece of 2X4 for not getting this one in the first place rather than my GEM newt (only 5" too!)

It has the essential fan, 10:1, 2 inch focuser and a bucket load of EP's. Sooner or later you will want to get a nice ED eyepiece to really spice things up (only about $60 or so) and then you will be having to wear a bib to stop the drool from dropping on the primary from having your mouth gape open at the EP.

Go on, you know you want to. Hell, now I want too as well. I'll race ya!

Chris

[Starkler]

Its pretty simple really. Yes there is a difference between the 10 and 12 which is noticable at the eyepiece.

If transporting the scope isnt an issue then buy the 12 and you wont be wondering later down the track.

[Kokatha man]

Strrrruthh Screwie - those lederhosen will sure come in handy, but you'll still need a bib too: and all I've got to offer you is my older welding apron!

There's so much drool coming off your post me flamin screen is hard to read; our elderly labrador couldn't keep up with you at the moment, not even as he's waiting for his tea: surely you're not telling us that if the supplier offers you a replacement scope, or the money back, your going to forsake another of those little barlowed beauties and find the extra cash difference for a 10" or 12" dob?

Cheers, Darryl.

[Screwdriverone]

Hi Darryl,

Yes, the lederhosen are being recycled as a bib, mmmm, suede bib, I am sure Gunter would approve!

Best Case scenario is they say " ummm, we cant fix it as it has a MAJOR problem, but we can offer you a replacement or a refund!" Then I kick up my heels and trundle down to the shops in my BMW with my Kraftwerk blaring from my Blaupunkt speakers and grab said $499 10 inch dob and giggle like a schoolgirl for at least a few months. Until I have to collimate it!

I am hoping to get it back in a tip top condition as it is quite a good scope, just been too idle without it and looking at what I could have bought for the same money.

Oh well, Oz Lotto's $40 million isnt mine, so I will have to start saving up zie fünfhundert deutschmarks ya?

Auf Wiedersehn!

Kristoff

[Kokatha man]

Gunter agrees Kristoff, but you're not keeping my Kraftwerk cd's after what you said some time ago.....excuse me Kristoff - "what's that Gunter....? No, Kristoff's Telekunken scope is still telefunken, he's hoping to swap it for a dob: I just want my Kraftwerks back before he manages to do something to them!"

Sorry about that screwie, Gunther reckons that he's got no problems with lending you his cordless and wire brush.....

Regards, Darryl.

[Screwdriverone]

Ha Ha Ha - Telefunken, nice one! :rofl::rofl:

Chris

[psyche101]

I very recently added a 10" Dob to supliment my Celestron Nextar GT. I went looking at what was available (2 shops I could find on the Gold Coast) and I ended up finding that the price difference between 8 and 10 a couple hundred, but upgrading to 12" was just over double the cost of the 10". I was assured I would not grow out of my 10", and I must say the clarity is every bit as good as I was told. I picked up a brand new 10" Dob for $550. I thought that quite well priced? The 12" was $1200. Seemed a hefty upgrade as opposed to 8-10. The Meade eyepice kit was as much as the Dob though. The wide field peices are a real treat. I thought that better value than the larger mirror. Weight is something too, it's qute a beast to even lug into the backyard, but I find well worth the effort.

[Dog Star]

I guess my original question is very similar to the old "How long is a piece of string?" question. (The correct answer to which I was taught was - twice the distance from its middle to its end.) ;)
Having weighed the essence of good sense of the replies to my original post and taking all relevant matters into consideration, I've decided to ring up and order a 12" dob bright and early Tuesday morning.
My thanks to all who participated in my time of confusion and soul searching.
As I suspected all along; all other things being equal, aperture does indeed rule!:doh:

[glenc]

A good decision, if you live in a rural area and there is no need to move the scope, the 12" is the best choice.
With a 10" you have to bend over a lot, with a 12" you rarely do.

[Dog Star]

Now that is an important piece of information that no one thought to mention. A bloke who suffers from a bit of back pain needs to know little snippets of information like that. It had never occurred to me that the viewing posture of each could vary somewhat. Many thanks Glenc, you've helped me to confirm my decision.

[glenc]

But you can hurt your back if you lift the 12" the wrong way.:)
I have wheels on mine so I can wheel it around like a wheelbarrow.
See: http://www.iceinspace.com.au/forum/attachment.php?attachmentid=9461&d=1139814803
That is an example, not my scope.

[Wombat_In_Space]

As a long time owner of a GSO 12" nearly 3 years, if you are not worried about transporting it e.g: have a wagon or 4WD then go for the 12" solid if you have small car go for the truss 12".

[Screwdriverone]

Hey Dog Star,

Check this (http://www.iceinspace.com.au/forum/showthread.php?t=31502) out, I just found a hot damn! special at Andrews for 12inch Skywatcher DOBS - $599.

Sorry Psyche101 I know you just bought a 10" :doh:

Cheers

Chris

[Dog Star]

Thanks for that Screwey, most thoughtful. Hmmm. Working out what you want is only half the battle. The major battle is to work out who to give your money to.

[Gargoyle_Steve]

The choice has become trickier now Phil ... keep in mind however that these are the exact same basic scope from the same manufacturer, it's only the "trimmings" that vary slightly.

I've pasted the relevant bits from both websites below - Bintel have more "florid" detail but I've removed some of the "filler" and left the basics.

The main diferences I can see is that you get 5 ep's at Andrews, and a Right Angle / Correct Image finderscope for $50 less, Bintel appears to provide the basic "Straight Through" finderscope instead and 3 ep's.

Bintel will also pre-collimate the scope, the alignment of the primary mirror will most definitely move around while on it's way to you up there and will need adjustment again, but the secondary position "up and down" the tube should not move. While all aspects of collimation are skills you can learn to do well, on your own, from the internet (I did) there is some value for you, being so remote, in having that done for you first. I strongly suggest you also buy a Combination Sighting / Cheshire tube to assist in your own collimation, and perhaps a laser collimator afterwards as well to augment your ability to do a "quick touch up".

The 6mm (from Andrew's) will be hard to use when wearing glasses due to it's very short eye relief (ie distance from lens to eyepiece to obtain a proper image), and the 25mm is almost redundant since they give you a wide angle 32mm as well. That leaves a 9mm, 15mm, and 32mm wide - which is what Bintel provide.

(Interestingly though Andrews state clearly that the "GSO dobs have a 3 year factory backed warranty" while Bintel advertise "You get piece of mind with our comprehensive 2 year guarantee.")


The choices in more detail ....

$749 at Andrews Communications

http://www.andrewscom.com.au/site-section-10.htm

Super Deluxe version
Super low price!
$749.00 AUD
First grade 12" (300mm x 1500mm) Dobsonian reflectors with truly outstanding 1/12 surface wave BK7 mirrors and 2" Crayford style focuser with 2" to 1.25" adaptor.

Super Deluxe version includes a right-angle correct image 8 x 50 finderscope, 2" Crayford style microfocuser with 10:1 fine focusing and a 2" to 1.25" adaptor, fan, GSO 6mm, 9mm, 15mm and 25mm 1.25" Plossl eyepieces - and a bonus SP32mm 2" eyepiece, too!


or.....


$799 at Bintel

https://www.bintelshop.com.au/Product.aspx?ID=6994


Bintel BT-302 12" Premium Dobsonian
Click here for larger picture (https://www.bintelshop.com.au/Images/Stock/6994X.jpg)

$799.00



Stock code: 6994 New models now include 10:1 fine focus Crayford focuser
302mm mirror diameter with a 1500mm focal length (f/5). A cooling fan ..... equipped with a 2" 10:1 Fine focus Crayford focuser

Standard Accessories include: - Eyepieces: 32mm Wide View (2"),15mm and 9mm Fully Multi-coated Plossl (1.25").
- Moon filter 1.25" for improved Lunar contrast and detail
- 8x50 Finderscope
- Mirror cooling fan


Every Bintel Telescope has been given a full checkup prior to sale. The Optical Tube Assembly is thoroughly checked and collimated to ensure your new telescope is going to perform as you would expect. Not only can we supply an excellent telescope at a fantastic price, we offer the after service support to ensure years of happy observing.


Specifications:
- Aperture: 302mm
- Focal length (f/#): 1500mm (f/5)
- Limiting magnitude: 14.9
- Resolving power: 0.38 arc sec.
- Weight: 20kg OTA, 12.5kg Base
- Dimensions: OTA 1450mm long ~ 450mm diameter including tube bearings

[PeteMo]

There is a defininte difference between a 10" and 12" but how much difference depends on what type of object you are looking at. I've a 10" SkyWatcher dob and had the opportunity to have a look through it's bigger brother. The 12" seemed a bit brighter to me with Omega Centauri, along with galaxies like M104 (sombrero), M65, M66 and M96. A lot of differences will be subtle, like extra detail in cloud bands on Jupiter/Saturn, or extra definition to whisps of gas in nebulae etc. The 12" dob user didn't complain about light loss when he viewed through my 10" scope, so for most run of the mill stuff you may not notice much difference.

Although a 12" dob mirror has 1.44 times more surface area than the 10", please remember that this does not equal 1.44 times brighter, or sharper.
If I remember correctly, to double the amount of light you see you will need a mirror with 4 times the area, (square law). Going from 10" to 12" won't be like going from a 60W bulb to a 100W bulb. More like a 60W to 75W, for want of a light bulb anaolgy. I certainly don't regret getting my 10".

In the latest ads for BinTel in AS&T, they state that the 8, 10 and 12 dobs have "8 x 50 90 degree Finder Scope", so the spec is identical to Andrews minus the 6mm and 25mm Plossls.

It's amazing just how much dobs have come down in price, even SkyWatcher 12" dobs are now under a grand, whereas they were close to $1400 when I got my 10" SkyWatcher last year.

Enjoy!

[Screwdriverone]

Hey PeteMo, check out my post on reply 25, the Skywatcher 12" dob is now only $599! :eyepop:

But from what you are saying, the 10" version more than does the job hey? For $599, could you say no?

Chris

[Jen]

i would be happy with either of those :P:D

Oh hi Chris

[Screwdriverone]

Hiya Jen,

Didnt notice you there, until I saw the emoticons, ha ha ....

Its good to be noticed

Cheers
Chris

[Jen]

:hi::hi::hi::hi:
:rofl::rofl::rofl:
:D
:whistle:
i think we have just hacked this thread heheheh
:scared3:

[psyche101]

Thanks for the heads up Screwdriverone, but I really do not go for the mail order stuff. I have very limited time,and dearly love to browse, so I thought the 10" @ $549 still good value, and I used it that very night. I would be devestated if I waited a week for something and the mirror was broken in transit or something. I would like a 12", but think I might hire one for planned nights. The 10" alone is one heavy cannon to lug into the backyard even I find, I am going to glenc's wheel thread he mentioned (thanks for that) to apply the principal to the 10". Us old fellas can't lift like we used to LOL ;) Although I didn't realise that the 12" was less bending over, wish I had known that as that would certanly have been a major consideration, but as I said, locally the 12" was more than double the price of the 10", and I was told the difference was not at the eyepiece, but the eypiece at that size. Can anyone clarify/expand on that? I spent the differerence between a 10 and a 12 on a set of Meade eyepieces, good compass, filters and a 3x barlow, which it seems woks real well with my new 14mm eyepiece. Not a patch on some of the closeups I have seen on the photography section in here, but I assume there is a few tricks for a beginer to learn to get that close. It dead set looks like some members have flown, landed on the moon, and spent a few days in Jupiters orbit with camera in hand!!! The Hubble would be jealous!! The talent here amazes me.
I must say I am more than happy with the 10". I am just amazed at messier objects, and I really am taken with the large eyepiece, although I only have a 32mm, it really is impressive on clusters and the like. I have never seen the Milky Way in the way that my Dob showed it to me. I really was amazed (and continue to remain that way). The range of eyepieces is just great too, they offer a very satisying diversity.

[Jen]

:clap::clap:

[AstralTraveller]

You probably looked straight over her :P. She's a self-confessed short**** (says big, strong 6'2" Dave ducking for cover) :scared3:.

[Jen]

:lol::lol::lol:
look out Dave i can still see ya wif my telescope :astron:
:poke::poke::poke: size dosnt always matter when :D umm well maybe but........... :P

:lol:

[AstralTraveller]

:confused:Huh?? That's a funny name for a scope. Or does your scope wif? If it does I suggest you don't keep it in such a damp spot.:P

[Jen]

:rofl::rofl::rofl: