What's the optimum size for a scope?

[oceanheadted]

Just read Lulu57's comments about her Celestron 4SE which has raised a new question in my mind.

What's the optimum size for a telescope? Before I get a hail of 2m responses, I think the discussions a bit more complex than just light grabbing power. I have a C80ED which usually gets stored on a skywatcher AZ3 mount and a 200p newtonian (on an EQ mount). The C80ED gets used a lot more because I have it up and running in a minute. Setting up the 200p is much more involved so I have to know I am really going to have good conditions because I drag it out of the garage.

I don't think a 100mm refractor would be much more hassle to set up than the C80ED, but 150mm would probably be too high on the hassle factor to cause me to choose it for that spur of the moment foray into the garden.

What are your opinions? I remember Paulo said he could set his 8" dob pretty quickly, so maybe that's the optimum size - well unless you are lucky to have an observatory to pop out into at the drop of a hat.

[Leegsi]

My SW150 stays on its EQ3-2 mount in the corner of the room.

Takes me about 5 minutes to get it outside but thats about as big as I would want to go as its quite heavy/cumbersome.

[kniclander]

I can carry my 10" dob out the shed and be observing in about 30 seconds. a 12" i'd have to carry out in 2 parts.

[John]

I had a 12" dob for quite a while but ultimately found it too much hassle and it was not getting used as much as it deserved. I've replaced it with a 10" Orion Optics newtonian which is very light and portable for a 10". I still find I turn to my 4" and 5" refractors more often though because of quick cool down and no collimation worries. I also like the kinds of views that refractors give

Based on the scopes I've owned in the past I reckon an 8" F/6 dob is probably about the best combination of portability, speed of setup, ease of use, relatively low maintenance and viewing potential.

As you say though, if you have an observatory or similar the whole picture changes.

[brianb]

What's the optimum size for a telescope?

If you're a variable star observer, one with a limiting magnitude 2 - 3 mags fainter than the star you're trying to observe NOW. Otherwise, as big as you can manage.

[tinvek]

like you my c 80 ed on an az3 gets a lot of use as a instant decission grab and go, but the 10" dob is almost as quick to carry out, just the cooling time stops it being the instant choice, it's certainly far easier to carry than the 150 on the EQ3-2 ( which to be honest is getting a bit neglected these days) partly because of the weight but mainly because of the shape and the fact that the tensioner handles make very usefull carry handles, all of which mean it can be carried out in one piece though if someone had back issues it splits and reassembles far quicker than a decent sized reflector on an eq mount by the time you've rebalanced it.

i'd imagine an 8" would be about the optimum sweet point for portability and aperture.

P.S. the 250 seems to hold colimation pretty well aswell, the rather large puppy smacked the tube down onto the edge of the mount a while back and left a dent about the size of a 5p piece in it but the colimation never moved

[oceanheadted]

Wise comments guys. Maybe I should start looking around for a dob base to go on my 200P! Still have a yen for a 12" dob, but I'm just a bit concerned it might end up spending too much time in the garage.

[Rusty Strings]

I'd put it on a dob base, because it takes no time to set it up, you don't mind quite so much when you bring it back in 'cos the clouds came over whilst it was cooling. And you still have the EQ mount should you feel lazy and want to track.

John

[arad85]

I'd echo the above comments on dobs... Whatever you can handle. I can have my 12" outside in about a minute. Given my observing place is just outside the back door, and the 'scope is kept about 3m from the back door, I find it pretty optimum. The only thing you have to worry about is cooldown, but a little forethought here goes a long way

I guess I'm lucky in that at 6'7.5", 19 stone and not suffering any back ailments, I don't find moving the big base/scope around too difficult - although I do have to do it in 2 pieces....

[matt c]

I can carry my 10" dob out of the house and into the garden in one piece, there's even a step and a bottom half of a pvc doorframe to get past. But I' rather that than a 6" refractor, I was going to get one of these originally but kind of glad i didn't:):)

[lguise]

A 10" or 12" Dob is a great all round scope. Particularly the Orion Optics dob bases which are compact, easy to lift and being aluminium do not deteriorate in the way some of the cheaper compressed 'wood' bases do. Only constraint is cost, well worth looking out for good second hand ones. I prefer the longer focal ratio versions, they tend to be much more forgiving and with better contrast. IMO A well set up Newtonian Dob is a great option if you are having to carry equipment outside.

L

[TheThing]

My 4" Mak gets a lot of use because it is small, compact and can bet set up in seconds.

The 6" Newt takes a little longer to set up because of the cables powering the pillar, but is still a breeze to set up as well.

Decisions, decisions!

[vlebo]

I can carry my 10" dob out the shed and be observing in about 30 seconds. a 12" i'd have to carry out in 2 parts.

I have a 12 Flextube and , you are right , it takes about 1 minute to setup.

[moocher]

You can`t go wrong with a 4" apo refractor, a Vixen FL102 on Vixen SP mount for instance.......

Alan:)

[James]

I'd reckon the optimum size is a blend of whatever allows you to do whatever it is you want to see and whatever you find easy enough to set up that you will actually do so. Many go for telescopes that are too big for them and ultimately don't use them as much as they might otherwise as they're too much of an inconvenience to use.

For me it's a 10" Newt for visual as I figured 12" would be just a wee bit too much (I wanted goto - otherwise a 12" Dob is every bit as easy to manage as an equatorially mounted 10" Newt.).

Proof that there's no optimum size is that many have two, or more, telescopes. I'm no different - I have a 4 inch refractor as well for situations where the 10" is too much.

James

[michael.h.f.wilkinson]

I like my Celestron C8, it takes longer to set up than a Dobson, IF if want really accurate polar alignment (which is actually quite easy using the polar finder in my Great Polaris mount). If I am just observing casually, I do not need such accurate alignment, and can set it up in under 5 minutes (longer than a dobson perhaps, but still pretty quick). Polar alignment takes another 5-7 minutes I suppose. I am planning to buy a bigger newtonian (12"), but will not discard my old C8. It is still compact (just about) enough to take along on holidays (in a big car). A 5" or 6" SCT or Maksutov is probably better.

Of course, if you are really into planetary work, a smaller refractor would be the better choice.

[russ]

Of all the scopes i've owned my current 8" dob seems to be the optimum. Sets up in seconds.....simply be impossible to setup a scope faster. So no point having a small frac on a tripod. The views are great on all targets. 8" is a great balance of size and performance. Cool down is not a big issue coming from the shed. It's so darn easy to use. And holds collimation well.

So 8" dob gets my vote.

Russ

[pvaz]

I vote on 8" dob too. 10" is probably easy too.

Mine is kept in the garage and I never feel it needs cooling down. Images stay sharp from the start. Takes about 1 minute including opening the garage door, move the scope 10 to 15 meters. Then remove the caps, put an ep in and there you go.

The rear side of my house haves better East - North view while the front haves a better south - west view. I often move the scope mid session depending on what I want to observe. Since I didn't waste time aligning no harm done.

That said I still want to add an EQ mount and maybe 1 or 2 more scopes to my collection. But the dob is a keeper.

[russ]

Sounds much the same as me Paulo. I do have the tube rings and dovetail so the dob can be mounted on the EQ5 should i wish but i haven't done that since May 2009. Works best as a dob

[oceanheadted]

H'mm I already have a 200p which gives me a bit of a dilemma (ok it's a good one). If I bought a 10" dob it would it be worth the extra expense (versus the 200p) or do I go for a 12" it might be too big and lose the convenience factor. Otherwise look around for a dob base for the 200p and stick with that for a while.

[russ]

That is a dilemma. There's no disputing that a dob based newt is far easier to use and setup than a EQ mounted one. I know i wouldn't use it as much if i had to setup the EQ5 each time and probably would go looking for a small refractor setup. But it's not just the setup that appeals but the way you use a dob. There's no part of the sky it won't go to easily, unlike the EQ where at times you are battling the mount. And there's no awkward eyepiece moments, everything can be done sitting on my ironing chair. So it's definitely worth getting a dob.

I would be tempted with the 12 dob. The setup time will be 3 times that of the 8 but 3 times 60secs still isn't anything. I had some real wow moments with the 12". I would consider a 12 again if the secondhand chance came up.

Russ

[Beulah]

H'mm I already have a 200p which gives me a bit of a dilemma (ok it's a good one). If I bought a 10" dob it would it be worth the extra expense (versus the 200p) or do I go for a 12" it might be too big and lose the convenience factor. Otherwise look around for a dob base for the 200p and stick with that for a while.

If I were you, ignore the pangs of Aperture Fever for a while and enjoy the scope you have - also ignore all the advertising, and all the astro mags who tell you such and such can only be viewed with a 12" aperture and higher - some of that gumph is only to keep the market in momentum and foster a deep dissatisfaction with what you have already. (Why do you think a 50" Dob is now being sold by Orion USA?)

Granted, light pollution has increased, but there is still a lot of worth in the scope you have.

Just get good use out of the scope, try all sorts of different observation sites and test the scope's capabilities in both very dark and LP'ed skies.

Astronomy is all about exploring the night sky, not constantly hankering over bigger and better equipment.

When you have felt you have gone as far as you can with the scope, then it might be time to relapse fully into Aperture Fever... (Plus the fact you may have saved some hard earned cash in the meantime to buy a REAL monster! )

[Macavity]

Well, I'll remain in dilemma for now... 'cos the gas fire just "konked out",

so inevitably eroding the telescope budget!

For me personally (with sometime angina) it seems mostly lifting stuff ABOVE waist level that hurts. If I'm going to do it infrequently, "OK scopes" - i.e. between weights 5-6kg are: ED120, C8 and MAK180 - Each with their own characteristic (dis)advantages.

Re. the Skywatcher Dobsonions, I note that the 10" is the same length as the 8", simply fatter (heavier)! Sizewise, the 12" seems to be a quantum step bigger in most things? So, to me a 10" Dobsonian, on wheels, stored "locally" looks to be still of interest... And of course, proportionally, the 8" to 10" increment may be more significant.

Another thing of potential interest is the F number? The 8" and 10" Dobs are the same height and have f=1200mm. This makes them F6 and F4.8 resp. The 12" is F5. But it occured to me... What of this COMA thingie? Large® Dobsonion owners (sic? LOL) seem to place importance on this "Paracorr" idea. I have no feel for THIS aspect. Would an F4.8 scope need one and an F5 (F6) not. Obviously it's not a "sudden" factor, re. size, but just generally wondering...

[russ]

If I were you, ignore the pangs of Aperture Fever for a while and enjoy the scope you have - also ignore all the advertising, and all the astro mags who tell you such and such can only be viewed with a 12" aperture and higher - some of that gumph is only to keep the market in momentum and foster a deep dissatisfaction with what you have already. (Why do you think a 50" Dob is now being sold by Orion USA?)

That is right. And the 12 is a beast. While i do fancy one again, i have no burning desire to ditch the 200P tomorrow and get another 12. It would have to be a mega bonkers secondhand deal for me to switch. But even then i would have doubts about swapping from the 200P. The 200P is so capable and i'm always amazed at just what it can manage everytime i take it out.

So i'll echo Beulah and say just enjoy your 200P.

Russ

[oceanheadted]

Thanks Russ/Beulah, wise words. I'll stick with the 200p maybe look around for a dob base, that would be a cinch to set up.