What's The Best upgrade option from Optex 8" Dobson

[PeteMo]

I enjoy using my Optex f1200 8" Dobsonian, but want to see more. I'm currently eyeing up the 10" and 12" GSO Dobsons the Andrew and BinTel flog as I definintely want to stay with Dobs.

I've done the maths and know that a 10" captures about 50% more light than my Optex 8", and a 12" captures 125% more light than the Optex. The 10" (f1250) gives me a fraction more in magnification whilst the 12" (f1500) will increase the magnification by about 25%.

What does this mean in real viewing terms? Will a 10" be a noticeable improvement in resolving power, or would the 12" be more significant. For example will the cloud bands on Jupiter and Saturn be more noticeable with a 10" or 12" compared with my 8"? When I view M42 in Orion, will I see more colours or gas cloud?

If any members have experience using an 8" Dob and then upgrading to the GSO 10" and 12" I'd greatly appreciate their advice.

[ving]

if you wait till feb next year andrews should have the 16 inch GSO dob. the bigger the aperture the more you see :)

[iceman]

Hi Pete

:welcome: to the forum! How did you hear about us?

If you're weighing up the option of a 12", I'm guessing you've already factored in the size, weight, portability etc?

If I was going to upgrade from an 8", it would definitely be to a 12", as long as I could still transport it as required.

I've got a 10" dob (GSO from Bintel), and I've looked through plenty of 8" and 12" versions of them, and the 12" is definitely worth the extra $$$. It will show you more detail on planets (if the seeing is good) thanks to the longer focal length and more light gathering.

I can't really justify going from a 10 to a 12" at this stage, but would probably more be looking at going to a 15 or 16" truss dob.

[g__day]

Hi Pete and welcome aboard!

It would be fair to say bigger scopes give you more light grasp, which in turn reveals hidden or faint detail more.

I'm on my fourth scope now - a C9.25 + 80mm refractor, both of which I normally use at very low magnification to get a wider field of view. I commonly use a 25mm Vixen UWA eyepieces on both - so say around 120x magnification on my main scope.

I'd doubt a 4 metre scope would show colour in even Orion to the naked eye. Only a CCD can well distinguish colour with these low light levels.

So consider you choices which tool for grabing light - not magnification most of the time (excluding planets) and that means the 12" would give much more satisfaction.

[janoskiss]

I have both an 8" and 12" GSO Dob. The 12" certainly has more lightgrasp and resolution, but the 8" is still often all I need. I use the 8" much more often.

The 12" is somewhat awkward not only to set up but to use as well. The 12" Lightbridge seems better in this regard, not so much because it's a truss but because the OTA diameter is smaller. It's easier to observe with it sitting down. Any 12" will take longer to cool. On moderately cool nights (say ~10 degree diff btw outside and inside), it's at least 15 minutes before the 12" catches up to the 8" ito resolution.

IMO a 12" is not an upgrade to an 8", but a second bigger scope for special nights/occasions (eg. w/e's away galaxy hunting). OTOH a 10" is comparable in size to the 8" and it's worth considering upgrading. And still just as comfy observing sitting down.

[PeteMo]

Thanks you have all convinced me that the GSO 12" is worth the extra $100. I just had visions of it being a bit big and clumsy compared with my Optex 8".

Hi Ving
Thanks for the tip, but I think I'd need to move somewhere bigger to house a 16" supergun. Also, I can't justify $2500 for a 16" at the moment, but I will definintely go for the 12".

Hi Iceman
I think I'd be OK transporting a 12", but did consider the extra tube length as maybe a little clumsy, but now that you mention the extra magnification, plus light gathering abilities, I'm definitely swayed towards the 12".

Hi G__Day
Thanks, I'm going for the biggest that I can afford. I'm certainly after more detail of faint things.

Hi Janoskiss
Thanks for sharing your experience with various sized dobs. The 12" will be my next step. I intend to keep my 8", so visitors would have 2 scopes to play with.

[PeteMo]

My next question is do I get the 12" from Andrews or Bintel?
Thanks again
Pete

[janoskiss]

up to you. It depends what you want to do with it. Bintel are better if you want them to customise it for you. Andrews is better if you want to customise it yourself, i.e. fit your own fan, focuser, finders etc (because they still have the basic models afaik).

[ving]

ANDREWS AND BINTEL.... its six of one and half a dozen of the other really. which ever you like. they are both as good as eachother :)

just bought a heq5 mount from andrews, no problems :)