10 inch dob vs 12 inch dob for planetary

[JokubasJar]

I have been debating with myself for days now and I can't decide. I plan on buying a dob with an equatorial platform for planetary. But I can't decide if I should get a 10 or 12 inch dob. The two scopes I am looking at are the StellaLyra 10'' f/5 and the 12'' f/5 dobs, the two scopes are identical except for the aperture. I'm pretty skinny so I figure the 10'' would be easier to carry around but in theory the 12'' should provide better images. I remember a saying: "the best telescope is the one you use the most". So I wonder, are the extra 2'' of aperture going to make that big of a difference for planetary? The two scopes aren't that far apart price-wise either. The EQ platform is rated for up to 50 kilos so both scopes are suitable but perhaps the 10'' would put a bit less strain on the motors too? 

Also, sort of an off topic question but, let's say I would want to dabble in deep sky with this setup, what is the limit on sub length? I don't assume they could be any longer than 25 seconds for the EQ platform but even 5 sec subs would be enough to get some kind of result.

[niallk]

What's the seeing like at your typical observing location(s)?

Edited March 22, 2022 by niallk

[Guest]

Neither scope will be particularly fun to handle if you are putting it on something other the a dob base.  It's not that they are heavy, but they are awkward as heck to handle.  My 10 inch lives on a cart and is fully assembled so it is kind of grab and go.  As to the 12 inch it will definitely gather more light and that is always a plus.  If I could go back and start over....I would get the 12 inch 

[Mr Spock]

As a StellaLyra 12" owner all I can say is it has already given me the best views of the moon I've ever had. Over the years I've had two Skywatcher 10" scopes and the 12" is far better. Earlier in the month under perfect seeing conditions I was picking up craters as small as 1 - 1.5 km. The sharpness and contrast are beyond anything else I've looked through. That night I was up to x447 at times with the best views coming at x397. A large scope in good seeing conditions can do that.

As for the size, I have a bad back but can still lift the tube on and off the mount. Having said that, the 10" flextube Dob I had I could pick up with one hand... The most difficult was the 10" solid tube on an EQ6. It was just too bulky to lift up to that height which is why I sold it and went for a C9.25. So, I've gone 10" on and EQ6, C9.25 on an EQ6, Skywatcher 10" flextube, 12" StellaLyra 

I have fitted Bob's Knobs primary springs and secondary screws which I think are a must. I've also strengthened the base and fitted a new bearing as it was a bit wobbly. A bit of extra cash but the scope worth it; I don't know what else you could get with such quality optics.

[Astrobits]

As above, both will be unwieldy to put onto an equatorial mount. However, I am always surprised to see no/little mention of sub-aperture masks on a big 'scope when the seeing does not favour the full aperture on planetary detail. Way back in the mid-80's I observed a particularly close opposition of Mars using three 'scopes on the same equatorial mounting and I could switch between them in seconds. The three 'scopes were: 6" Cooke refractor, 7" refractor ( I can't remember the make ) and a 12" Tinsley Laboratories Cassegrainian. The best view of detail on Mars was with the 6", the other two providing somewhat less pleasing images.

So, Go for the 12" and try sub-aperture ( and off axis ) masks to see if the view is improved on those less-than-good nights. And when you want deep sky you'll have that extra aperture.

Nigel

[Carbon Brush]

Have you been able to get a hold/carry/lift of a couple of dobs?
Where in the country are you? Could someone local let you have a look?

As someone who has owned at various times 8"/10"/12" reflectors, I would say they are very different beasts to what might be thought from 2" mirror steps.

HTH, David.

[callisto]

I'll throw a spanner in the works and give a big thumbs up for the 10"'.

Mine is on a EQ platform and tracks very good,

Also as above I've added Bob's knobs primary springs and secondary screws to my Orion Dob.

Planetary wise, it gives me excellent views when used with the EQ platform for around an hour 

[Stu]

I’ve had 8”, 10” and 12” and like everything it’s a compromise decision as to what’s most important to you.

Useability is a big thing! A big scope is useless if you can’t lift it, or be bothered to take it out. My most used scopes remain my 76mm and 100mm refractors which are outside on lightweight mounts within a few moments.

A 10” is actually quite a good compromise between the two, and will show you plenty. I would try to see (and lift!) one in the flesh before deciding.

Orion Optics tubes are significantly lighter because they are aluminium tubes, but are also a lot more expensive. They can be picked up cheaper used of course.

A lot depends on where and how you will use it. If you can put it on a trolley and just wheel it out then things get a lot easier. If you have to load it into a car to take to a dark site each time then it’s more of a challenge.

[Paz]

A straight comparison between f5 scopes gives a like for like choice but another option for planetary would be a 10" f6 scope, still lighter than a 12", with kinder optics and a smaller central obstruction.

[Guest]

On 23/03/2022 at 07:02, Carbon Brush said:

Have you been able to get a hold/carry/lift of a couple of dobs?
Where in the country are you? Could someone local let you have a look?

As someone who has owned at various times 8"/10"/12" reflectors, I would say they are very different beasts to what might be thought from 2" mirror steps.

HTH, David.

Here in the States Explore Scientific sells them, but any strap that gets all the way around the scope would work just fine.  Maybe add a little padding.

[Cosmic Geoff]

It depends on the seeing.  I soon realised that I could get better views of the planets by imaging than visually.   And I realised after a while that even with an 8" SCT the results were variable, apparently dependent on the seeing.  I read that the most fanatic planetary imagers take their big SCTs to the Carribean, where the seeing is better than in the UK. 

 And if you want to "dabble in deep sky" a much smaller scope would do to start with.  Many deep sky imagers use small refractors rather than big Newtonians.