What size dob for a beginner?

[_DaveH (Dave)]

Hi all,

So I've bought my binoculars, I've been to an astronomy meeting (the SPSP last month), I've looked through a few telescopes, I've read these forums, and I've done a bunch of research. I think I'm ready to buy a scope now.

Based on these forums and my research, a Dobsonian is the best thing to start out on. I've looked around at prices and Bintel is conveniently close to work, so I've visited the store a couple of times and looked at the telescopes there. The GSO dobs look to be good value, coming with a right-angled finder, 3 eyepieces, a crayford focuser and a cooling fan.

Now I'm just struggling with the final decision, which size to buy?! I won't say money isn't a consideration, but my wife has kindly approved up to $1000 on the scope, so the 12" is within reach (the decision might have been easier otherwise ). With over twice the light-gathering power in the 12" over the 8", is the 12" a good choice? The 8" has the advantage of being easier to store and transport, but will I see enough to make me not regret passing on the 12"? The only scopes I looked through at the SPSP were 12" (mostly Meade Lightbridges, but one 12" GSO), so I don't have a reference point for the difference to an 8". I'm not a small guy, so I don't think I'd have trouble moving the 12" around (though I imagine it would be pretty unwieldy).

Any helpful tips at this stage would be welcome

Cheers,
Dave

[bmitchell82 (Brendan)]

you have put all the things that we would consider in there.

if your doing visual, the more aperature the better.

you have already considered transportation ect ect, go the 12" in my idea you wont regret it

[Brian W (Brian)]

Hi Dave, I own an 8" LB and you will be able to see a life time of observing with it.

I started with a 4.5' reflector which allowed me to do the entire Messier 110 and much more. Thankfully I found that after about a year of observing that I had managed to improve my skills to the point that I was starting to push the 4.5 close to it's limits.

After 2 years with the 8" I am nowhere near the limits of the scope. Better ep's, filters, and greater skills consistently allow me to push the limits of the 8.

Will I someday move up in aperture... probably. But only when my skills have pushed the 8 to near the limits of its performance.

If my experience has taught me anything it is that there is no perfect starter scope... or even finishing scope.

If you buy the 8 odds are you will eventually move up to a 12 or bigger. if you buy the 12 you may well decide one day to move up to 16 or bigger.

The trick seems to be to find out what part of this fascination really grabs you and then to start gathering the needed gear.

Here comes my recommendation and please do not take it as the one and only truth. The 8 is a great size scope that does everything reasonably well and will allow you to find what really grabs you.

Once you have found your passion buy the equipment that will feed it.

Brian

[Brian W (Brian)]

Hi Dave, I own an 8" LB and you will be able to see a life time of observing with it.

I started with a 4.5' reflector which allowed me to do the entire Messier 110 and much more. Thankfully I found that after about a year of observing that I had managed to improve my skills to the point that I was starting to push the 4.5 close to it's limits.

After 2 years with the 8" I am nowhere near the limits of the scope. Better ep's, filters, and greater skills consistently allow me to push the limits of the 8.

Will I someday move up in aperture... probably. But only when my skills have pushed the 8 to near the limits of its performance.

If my experience has taught me anything it is that there is no perfect starter scope... or even finishing scope.

If you buy the 8 odds are you will eventually move up to a 12 or bigger. if you buy the 12 you may well decide one day to move up to 16 or bigger.

The trick seems to be to find out what part of this fascination really grabs you and then to start gathering the needed gear.

Here comes my recommendation and please do not take it as the one and only truth. The 8 is a great size scope that does everything reasonably well and will allow you to find what really grabs you.

Once you have found your passion buy the equipment that will feed it.

Brian

[mental4astro (Alexander)]

Hi Dave,

A 12" is a big instrument. Unless you have a wagon, it will take up the whole length of the passenger side of a sedan. An 8" would take up the back seat, or, if split fold, some of the back seat and into the boot.

An 8" scope is no slouch. Last year, a mate brought over his 8" dob, and we did a side-by-side comparison with it and my then solid tube 17.5" from my backyard in Maroubra. Where we spied 6 moons of Saturn in the big dob, 5 were visible in his. The galaxies we managed to pin from town in the 17.5" were all visible in the 8", not as bright, but very much there.

I'm mentioning this so you've got some reference to go by. Like Brian said, an 8" will serve you a life time, and without the bulk. You do need to consider your car to transport the thing. Or, you can always just get a semi-trailer and go down the 50" monster dob way, !


If you do go down the 12" route, and you find it difficult to manage, you can always do a DIY on it. A solid tube is not the only possibility. And the DIY option can then be configured to how you budget also develops, with or without altering the tube. Simple push-pull to start, then add the Argo-Navis, and then the whole hog goto option.

If Sydney's skies clear for the 12'th of June, me and a few others will be at Katoomba Airfield. There I'll be also taking an 8" f/4 dob. There might be one or two other GSO 8" dobs too, and maybe a 12". You'd be most welcome to join us and see what each scope offers, and how they affect each of their owners mobility and ease of use. Check out the 'Star Parties' forum for details. My 8" f/4 sits inside its mount, and sits upright in the back of my Mazda tribute, right along side my 17.5". Very comfy.

[wavelandscott (Scott)]

Decisions decisions...

No doubt that aperture rules...however, that does not mean that an 8 inch or 10 inch is a poor choice...I have reflecting scopes ranging from 8 inches to 15 inches and they all get used sometimes...

If transport (car or lifting ability) or storage is an issue avoid the 12 inch solid tube Newtonian reflector...consider a truss style or move down to a 10 inch or 8 inch solid tube.

Another thing to consider as the "additional" accessories that you may be interested in buying...

For example, one of my most used "extras" is an adjustable height chair...I use it every time with every scope...I can not imagine a night under the skies without it. The added comfort helps me be a better observer and in effect "adds inches" to what ever scope I am using with it.

Another often used "extra" is the telrad (zero power finder) it literally puts a "bulls eye" target on the sky and helps me find things fast...

Don't even get me started on premium eyepieces...

And the list goes on.

My counsel would be to apportion your total budget between scope and some accessories...

An 8 inch scope would have been considered "large" for an amatuer not so long ago and it will give you many nights enjoyment...

I found it easy to use and transport and I was not frustrated by the bulk of moving it around...I was able to concetrate on using it.

The 8 inch afforded me the opportunity to get some nice accessories that I use with all of my scopes.

No doubt that over time you will want to "move up" (aperture does rule) but there is no need to jump in the deep end as your first scope. A "right sized" scope and some accessories I believe will put you in good stead for many nights of enjoyment.

[astro_nutt]

Hi Dave.
My first "big" scope was an 8" dob. I found it to be a very capable instrument and provided me with years of enjoyment. Easy to transport and set up, and with the money you save on a bigger scope, spend it on some premium eyepieces, etc. Also an 8" dob is a good learning scope in collimation, practicing to locate various objects and to keep an object in view.
Whatever you choose, good luck!

[_DaveH (Dave)]

Thanks for the helpful replies all. I re-measured and thought about it for a while, and in the end I've compromised and gone for the 10". With the price difference I bought a collimating eyepiece and a Telrad.

Cheers,
Dave

[Brian W (Brian)]

Hi Dave, congratulations, if you have half as much enjoyment with your 10 as I have had with my 8 you are in for a wonderful time. Might I make 3 more suggestions.

(1) a pirates eye patch will make a world of difference. After an hour of keeping one eye closed it gets tiring but with an eye patch no pain no strain.

(2) download Stellarium a free astronomy program. It will show you (once set up) real time night sky at your location and will help you find things.

(3) download Astrobyte software. It is an excellent way to keep records and plan your evenings.

have fun and clear skies.
Brian

all right I was wrong about only 3... (4) get a chair, adjustable or not, that will allow you to comfortably observe.
B

[timmo567 (Tim)]

If your too cheap like myself to get an adjustable chair grab a pillow or two to put on a regular chair and you can stack and fold them to get different heights.