Buying 12" Dob - Expectations

[fbk (Fraser)]

Hi all, first post here..

I'm currently enjoying a 130mm Celestron with goto I bought not too long ago.. I generally know my way around the sky and this little telescope with Skyportal app is great. But as I'm sure many of you can attest to, aperture fever is real, and I have it. I believe something in the region of 6x my current light gathering power shall suffice as a cure initially so have my sights set on getting a 12" Dob.

Problem is, I've never looked through a bigger scope so I'm not entirely sure what to expect. I wouldn't think I have unrealistic expectations - but I'd really like to see more detail in some DSO when I have the opportunity to take it out to a dark site. Which from where I am in Perth means an hour or two drive away from the city.

I wrote to a local astronomy club assuming they would welcome potential new members and hoping for the opportunity to see some bigger scopes for myself, but I never got a reply.

So before I bite the bullet, for someone with some so far beginner experience with a 5" goto telescope, what am I likely to think when I first look through something that's 12". Will my jaw drop looking at globs and galaxies? Will I see more detail and/or colour in nebulae? I'm really only interested in the deeper/fainter stuff with this scope and will keep my 5" goto for the back yard, quick looks at the moon and planets, etc.

No need to take into account any size and storage/transportation issues as I have them covered. I'm also happy to have to star-hop and manually move this thing around the sky - I'm really only interested in what to expect visually when looking through something so much bigger than what I have, and whether you think I'll be blown away by the better views, or underwhelmed by how similar things still look. Any and all opinions welcomed. Thanks!

[Kunama]

I would strongly recommend that you try before you buy... Yes the difference is huge but only you can decide if it is for you.

I just recently compared a top shelf 5" refractor and an equally impressive 12" scope on 47Tuc and the difference is night and day...

[clive milne]

The difference between a 5" SC and a 12" dob (for deep sky) is night and day.

However... my preference would be for a 16" ultralight.
Things start to get interesting around that aperture and it's small enough such that you shouldn't need a ladder to get to the eyepiece.

If you are a purist though, nothing beats the 'gosh-wow' factor of looking through a pair of large Newtonian binoculars.

2c

[clive milne]

Some will tell you that size isn't important.

[AstralTraveller (David)]

Originally Posted by fbk

Hi all, first post here..

....
I wrote to a local astronomy club assuming they would welcome potential new members and hoping for the opportunity to see some bigger scopes for myself, but I never got a reply.
...

From my experience with astronomy clubs the lack of reply is almost certainly due to administrative incompetence. I've never known a club that didn't welcome new members and visitors with open arms (expect perhaps the old BAA which had an entrance exam). It's been nearly 30 years since I was in Perth but the ASWA was a very friendly and active group in those days. My wife and I went to the Dryandra astro camp without a scope and were able to spend the night looking through a range of scopes. The thing with voluntary clubs is that things don't always work well; contact details aren't updated, mail isn't checked, some people are lax or become lax, they go on holidays and no one fills in, all sorts of thing could happen. I suggest you simply turn up to a meeting and see what happens. I'd be surprised if it isn't positive.

[N1 (Mirko)]

Hi fbk, doubling the aperture (or more) is certainly a meaningful increase. Extended objects will appear 12"/5"=2.4 times bigger, at the same brightness, assuming your eyepiece set allows similar exit pupils for both scopes. Resolution will increase by the same factor. It will seem more than that due to the way our eyes and brains work, so expect a big imporevement for what you want to do. However I'm not entirely sure you've had a chance to develop an understanding yet of what that actually means at the eyepiece. I have a feeling that any objects you can't already see in your 5" are unlikely to make your "jaw drop" in the 12". You are more likely to go WOW at the extra detail you will see in familiar objects. And the more familiar you are with them, the bigger the WOW factor. Nothing wrong with that, just don't expect to see a staggering amount of detail in objects your existing scope doesn't show at all.

You've never looked through a bigger scope before, so I'm with Matt - do try before you buy if at all possible. And understand the limitations of your existing scope by using it to its potential.

The fact that you are susceptible to "aperture fever" means that you'll never be fully satisfied, whether you get a 12" or a 16"

[fbk (Fraser)]

Thanks all for the comments. I'm aware of the prospect of never being satisfied with aperture as long as there is something bigger available! But for now the price of a 12" dob is about where I want to jump in. Trying before buying would be ideal but I'm impatient haha.. and I did suspect that the reason for no reply from the club had more to do with email issues than being unfriendly.

I'm a big guy and drive a ute so being able to lift and transport the thing doesn't concern me. I really just wanted some first hand confirmation that the differences I'll see at the eyepiece will indeed be worth the extra hassle. I believe they will be so have decided to get one.. I appreciate the advice.

[astro_nutt]

Hi fbk. Have a read from the Equipment Reviews section. That helped me with my choice in purchasing a Bintel 12"dob. I am more than pleased with it. I did, however, made some mods to the mirror cell, stiffer springs, etc. Some quality EP's, Panoptics or similar, make viewing the faint objects easier. It will be a while before you view everything a 12" dob is capable of!
Cheers!

[Mokusatsu (Australia)]

I'm in Perth,

My instruments are a 12" goto dob and a 4" apo refractor.

Though the refractor cost me three times as much as the 12", on every single object except widefield stuff like the Pleiades and the Magellanic Clouds the 12" just blows it away. The dob even beats the expensive Televue refractor on planetary detail. Aperture matters!

If you'd like to compare I could meet you at AGWA's observatory in Chittering some time and I'll show you the sky through both scopes (bring your own as well) so you can compare. You can come as my guest.

Travis

[fbk (Fraser)]

Thanks for the advice astro_nutt, I've ordered a GSO 12" from Andrews identical to the Bintel 12". I'll definitely be looking at what tweaks I can do to it once I get it.

Travis - thanks for the offer! I'll PM you regarding meeting up some time.

[AG Hybrid (Adrian)]

Originally Posted by fbk

Thanks for the advice astro_nutt, I've ordered a GSO 12" from Andrews identical to the Bintel 12". I'll definitely be looking at what tweaks I can do to it once I get it.

Travis - thanks for the offer! I'll PM you regarding meeting up some time.

Grats. First thing. 2-3 Milk bottle tops(The soft rubbery bits that create a seal) between the spider and the secondary mirror holder. Some minor disassemble and reassembly required. Makes collimating the secondary mirror much easier.

Use the scope for a bit and get used to it.

Second, upgrade the main mirror springs to make collimation easier and hold collimation for much longer.

Step Three:

Throw it all away and buy a Skywatcher instead.

Just kidding.

Consider counter weights. The tension knob on the larger GSO scopes are not always sufficient to maintain balance.

Then spend several hundred dollars on a digital setting circle setup.
Then spend several hundred more dollars on eyepieces that correct well at f5.

and on
and on
and on
and on

Until your scope is no longer recognizable as a GSO telescope.

[astro_nutt]

Hi fbk. I should have mentioned that the Bintel 12'dob have an adjustable pivot on the optical tube so you can adjust the balance of the scope to your liking, then use the tension control. I had to place some 1mm x 10mm x 20mm plastic strips, about 6 in all, between the side of the main mirror and the mirror cell. They're held in place with a little dot of blu-tac from underneath the mirror. This helps stop the primary from moving when you go from horizontal to vertical after you collimate. Oh! and congrats to you also.

[fbk (Fraser)]

Thanks for the tips guys. I did the milk bottle washer trick to the secondary of my 130mm Newt. along with a few other tweaks. So the GSO will get what it needs too, all part of the fun... including stiffer collimation springs and mirror spacers etc, cheers astro_nutt.

Was planning to add a digital angle gauge for alt. and a setting circle for azimuth. Or maybe DSC but one thing at a time. Current scope is F5 and I'm happy with the eyepieces I already have. For now...

And Adrian I could have got a used 10" SW flex with goto for not much more than the GSO but decided I wouldn't settle for less than 12 inches. Cue jokes.