The second scope (size increment)?

[Macavity]

The second scope (size) increment. Too obscure? OK, say you have one (or two!) "first" scopes (qv): What would be your choice for the next size increment. Would you go for (say) 1.5x diameter (2x light gathering), or try for more: 2x (4x)? Obviously there are physical constraints: type/availability, size (new mount), COST etc.

Some might instantly say "light bucket"? But, not aspiring to be a galaxy observer, rather e.g. clusters, doubles, planets: Would going from say a 5-6" (generic reflector) to say a 7-8" be worthwhile? Or would one need a 10-12" scope to see much of a difference?

Aside: To me a 12" scope seems very big and heavy! With slightly "dodgy" health (weight lifting capacity) and around £1000 to spare, maybe the BETTER investment would be a small "run-off" shed. Do things in comfort... for a change?

[Doc]

If you want to aim for double stars, clusters and planets I would say go for a refractor.

IMO a APO refractor will beat a dob on double stars and planets.

[MartinB]

For observing I have a 12" dob and an ED120 refractor on a motorised Super Polaris mount. This pair complement each other very nicely.

[Macavity]

Thanks. I also quite like the idea of the "complementary" scopes. Another thing I did wonder about, re. refractor-like capabilities, was the new Skywatcher 190MN MAK-Newt. A versatile 7"/F5. The only minor blot on the landscape might be weight (24lb). Even for visual use an HEQ6 would be needed?

[brianb]

Even for visual use an HEQ6 would be needed?

I'd say so.

The EQ6 isn't that much harder to manage than the HEQ5, and it's a lot steadier. Hint, remove the counterbalance weights for carrying, it makes life quite a lot easier & refitting is a matter of seconds.

The real issue with Mak type scopes (whether newtonian or cassegrain) in sizes over about 6" is that they take forever to cool down, and until they do you won't get the sharp images which is their strong point.

Your 5" Skymax should do well for moon & planets, the downside is the long focal ratio. For a second scope I'd go for a shortish scope, either a 10" - 12" Dobsonian or a 80mm apo refractor on an altaz mount like the WO EZTouch, for wide field views of star fields which your Mak simply can't deliver.

[MartinB]

If you can handle an EQ6 or even an HEQ5 then a 12" skyliner dob would be no problem at all. It would be a great companion to your mak.

[Macavity]

Actually might not be able to handle an HEQ6.

But, there's wisdom in ALL this. I sense a straight MAK (150/180) is going to have a long cool-down, plus we're getting into significantly LONG focal lengths too. The MN190 has a nice (F5) focal length, but again cool down, and "twice the needed" weight for a 7-8" scope.

I do sense the MAK127 is worth keeping - Especially now, with it's 2" adaptation. A 10" Dob, with nothing to lift above waist height might be good - PLUS a decent APO refractor at some stage! It may seem like splitting hairs, but a 80mm APO paired with a MAK127 on my Giro III might have been a better "grab and go" than my present 4" ST102 achromat/MAK combo.

Despite initial circumspection, I'm actually now quite TEMPTED by (say) a 10" driven DOB. They don't seem QUITE so "monumental" as a 12"! And, if they can make them fully (alternatively?) GoTo, PushTo, whetever... so much the better!

[Whippy]

Personally, I don't think gaining an extra 2" of aperture with the MN190 is going to show you a great deal more than your 5" MCT. At the end of the day, it's a 7" newt (albeit with a very nice FOV with no diffraction spikes ). You're going to need an EQ6 with it too no question, which not only bumps up the price but also the weight too. I'd keep it and go for a 10 or 12" dob and stick come casters (with brakes?) underneath the base to make it easy to get out of the house.

Tony..

[Macavity]

Thanks Tony - Which sounds a pretty good summary... A plan even.

Yeah, having got over my (theoretical) trepidation re. DOB collimation (recently and neatly described elsewhere!) it now seem a lot clearer. Personally, I find the Alt-Az (Scale + Wixey) idea quite attractive. Fun stuff too, re. my limited carpentry (MDF Lite, wheels etc.) skills.

I see there are other threads on merits of driven DOBs, modularity weight etc. A relief to know we're not ALL "Pocket Herculeses"? Herculii? So probably a 10" DOB, with change from £1k, and time to ponder quite I might do with a soon to be mine (house move) SHED!

Cheers guys.

Of course, a nice big APO refractor... But for another day maybe.

[adamsp123]

I have a 120ED F/7.5 refractor and 10" Meade Schmidt Newtonian F/4, and they compliment each other quite well IMO, light gathering of the 10" is 4X the refractor which translates to my eyes/brain as 2X the brightness.

As I am getting more into photography I might look in the future at a 14" or 16" Dob for visual use, note not 12" as this IMO is too close to the 10" to really see a major difference.

BTW the my 10" SNT cools pretty rapidly but like all CATs suffers from dewing.

[acey]

Would you go for (say) 1.5x diameter (2x light gathering), or try for more: 2x (4x)? Would going from say a 5-6" (generic reflector) to say a 7-8" be worthwhile? Or would one need a 10-12" scope to see much of a difference?

Going from a 6-inch to an 8-inch would allow you to see 0.6 mag fainter, from a 5-inch to a 10-inch is a difference of 1.5 mag. (The relevant formula is 5log(A/a), where a is the smaller aperture and A the larger one). 1.5 mag is the difference between a light-polluted suburban sky and a dark rural one - it's huge. But 0.6 is the sort of amount that many people might not even really notice.

How much difference you see depends largely on how much experience you already have. Someone who has driven their scope to it's deep-sky limit will certainly appreciate another half a magnitude; someone who's just starting on Messiers will still see a lot of faint fuzzies with no spiral arms in sight.

I went from an 8-inch to a 12-inch (increase of 0.9 mag) and certainly saw an enormous difference. But portability, ease of use etc are hugely important factors, and there's no point getting a scope that's too big to be fun. I find the 12" flextube a breeze for transporting to dark sites, but that was after several years of doing the same thing with an 8-inch (which seemed enormous when I first got it).

If ever I upgrade I'll probably jump another 1.5x aperture (and 0.9 mag) which would take me to an 18-inch - but it'll be a while before I'm brave enough to face that. I'm waiting until the 12-inch seems genuinely too small for what I want to do. I don't expect that to happen any time soon.

[dweller25]

I use a 4" refractor and an 8" reflector - they compliment each other very well.

[MartinB]

I hate the sound complicating a dob. Finding targets is part of the fun (except at the zenith!) and if you can't find a target it may not be worth finding. Many of the DSO targets I hunt around for and eventually find turn out to be only worth it because of the hunt.

[John]

My current scopes are a 102mm F/6.5 ED refractor and a 305mm F/5 dobsonian. I've recently added a pair of 20x80 binoculars to the "fleet" and I reckon that set covers just about all the angles for a visual observer like myself.

My only concern is that the dob does not come out to play that much due to the mixed weather we have had lately - but when it does the views of DSO's are worth the effort - globular clusters particularly

John

[Macavity]

My only concern is that the dob does not come out to play that much due to the mixed weather we have had lately - but when it does the views of DSO's are worth the effort - globular clusters particularly

Yeah, I think that's the bottom line - And I do take your point re. refractors. There is STILL something "special" (contrast?) about the view through even a modest ST102! Apologies for my "extended wibbles". The interweb has assured me that they are not to everyone's taste. LOL. But I DO learn things... Or at least have my (mostly theoretical!) prejudices confirmed.

For MANY reasons (and despite optimism) astronomy was not really sustainable from a "communal garden" FLAT. With a little judicious... "downsizing", I shortly get a modest dwelling with a GARDEN (yard)! Heck, last time I moved house it was so my CAT could have space to run about in.... (believe me!). THIS TIME it's for my (indoor cat and) Astronomy! Whatever happens, it's been a long apprenticeship from my "Observers Book of Astronomy" (P.Moore c.1964). Hope springs eternal, I reckon...

[albedo0.39]

eventually find turn out to be only worth it because of the hunt.

I once spent ~30mins looking for the Blinking Nebula (I'd given it another name by then) and when I found it, the object was located exactly where I started. If I had my way, my 2nd scope would be a 25" Obsession. However, in the real world a good solid workhorse 5" apo would do just as niceley.

I'm by no means used to my scope, but I now wonder what a larger scope would be like... (I think they call this aperture fever and I can feel my temperature rising already)

[acey]

Most important thing is darkness of the sky. My back garden has limiting mag 4.5, I drive to a site that reaches mag 6. An 8-inch in my garden performs the same as a 4-inch at the dark site. I now take a 12-inch to the dark site. To get the same views from my garden I'd need a 24-inch, and even then I wouldn't get as good a view, because of stray light and the inability of the eye to dark-adapt.

Nobody expects to do mountaineering or water-skiing in their back garden, and light pollution increasingly means that astronomy is going the same way. The easiest way to increase your aperture is to take the scope to a darker site. Even half a magnitude is like going from an 8-inch to a 10-inch.

I know that some people think you can beat light pollution with aperture, but if that were really true then if you made a big enough scope you'd be able to see stars in daytime.

[brianb]

if you made a big enough scope you'd be able to see stars in daytime.

You can. 2" will show Polaris nicely....

[acey]

But how's the view of M51?