Which Dobsonian should I buy?

zumka (Daniel) · #1 20-10-2015, 12:00 PM

Hi Everyone,

I know over the years there was many questions in relation to the dobsonian size.

Should I buy 10" Dob or 12" ?
Is there a big difference between 8" 10" 12" aperture in dobsonians?

I found very good comparison image on another forum and would like to share it with you. This image shows what to expect when you are looking at the stars with the different size telescopes.

madwayne (Wayne) · #2 20-10-2015, 12:41 PM

An interesting question Daniel.

I can easily move my 12" solid tube dob, but I am 6'5" and my wing span certainly helps with that. If I were too much shorter and smaller and my viewing area more than the 5 metres or so from where my dob is stored then forget it. A 12" solid tube is big, make no bones about it.

Transportable? Just, I drive a Toyota Aurion (Camry newer model) and lay the passenger seat flat, tube just fits between the glove box and the rear of the back seat. The mount then sits on the back seat behind the driver's seat, again it only just fits.

I've given you this insight so you can make an informed decision about the sheer size of the 12". The best bang for your buck will be the telescope you use the most. This will be the one that is easy to setup, use and potentially transport to your chosen dark site.

And is always the case in a which telescope thread, I'd suggest a trip to your local astronomy club or retailer so you can these things of beauty in the flesh.

Wayne

zumka (Daniel) · #3 20-10-2015, 12:53 PM

Wayne,

Completely agree with you, best scope is the one that you going to use all the time. I had 12" solid Dob. As much as I loved it I had to sell it because it was very big and heavy. In my view 10" collapsible is the perfect combination between being more or less easy to move around and at the time give you reasonable viewing. The image in my previous post is to give people rough indication what to expect when looking at the stars with the different size scopes.

Daniel

N1 (Mirko) · #4 20-10-2015, 01:44 PM

Agree about the user friedly dob sizes. But the image is misleading. If my 2.4" or 3" "good quality telescope" was showing stars like that at 150x I'd consider turning the focus knob a few times. If that was unsuccessful, I'd throw the thing away and get an apo of the same aperture

To be more accurate, the images should become fainter, not blurrier, as aperture decreases. Higher powers , different story. But this is 150x.

zumka (Daniel) · #5 20-10-2015, 01:47 PM

Quote:

Originally Posted by N1

Agree about the user friedly dob sizes. But the image is misleading. If my 2.4" or 3" "good quality telescope" was showing stars like that at 150x I'd consider turning the focus knob a few times. If that was unsuccessful, I'd throw the thing away and get an apo of the same aperture

To be more accurate, the images should become fainter, not blurrier, as aperture decreases. Higher powers , different story. But this is 150x.

As I said image is the rough indication of what to expect.

N1 (Mirko) · #6 20-10-2015, 01:50 PM

Quote:

Originally Posted by zumka

As I said image is the rough indication of what to expect.

Showing M13 at "roughly" the same brightness in a 2.4" and a 14" at the same power? I don't think so, sorry.

But on the subject, yes a 10" is a good, manageable yet capable size.

zumka (Daniel) · #7 20-10-2015, 01:57 PM

Having another look at he photo the image should be fainter the lower the aperture.

N1 (Mirko) · #8 20-10-2015, 01:59 PM

Quote:

Originally Posted by zumka

Having another look at he photo the image should be fainter the lower the aperture.

Correct

Edit: I can see what they mean by making it blurrier the lower you go. I just don't think that this effect kicks in at 150x. Not like that anyway.

Sammas · #9 24-10-2015, 11:04 AM

Regardless of scope size, make sure the dob base has very smooth movement. When you're looking at a celestial object even very small movements can send the object out of your field of view and then you can spend minutes trying to find it again. If the dob has stiff movement then you will have a terrible time trying to keep the object in the view, and this will really negatively impact on your experience.

Irish stargazer (John) · #10 26-10-2015, 05:40 PM

As has already been mentioned, a 12" solid tube Dob is a heavy piece of kit. I looked at them when I was considering a Dob for travelling to dark sky sites (Pony Club, Wiruna etc..). The solid tube would not fit in my older Camry at the time. A 10" is about the limit as a solid tube which would fit on the back seat.
I ended up with a truss tube 12" (Lightbridge) which when disassembled easily fits on the back seat of any car and only take a few minutes to set up. No heavy parts to lift. I like having the 12 inches of aperture. it gives great views of the moon and planets as well as deep sky objects. I leave it fully assembled in my study. The scope (OTA) can be carried out fully assembled (heavy)

SkyWatch (Dean) · #11 26-10-2015, 08:57 PM

I agree, a 12" dob is do-able if you have a truss or a collapsing version: the Lightbridge or the Skywatcher collapsible are good commercial options. My 12" is home-made and is smaller than my 4" refractor to carry around in the car...
If you aren't into ATM, but have the budget for a really nice commercial version, one of the forum members makes light-weight easily transportable dobs here in Australia. Have a look at: http://gondwanatelescopes.com
All the best,

Dean