Need help choosing my first (planetary) scope

[dvd88]

Hi all,

I really need some advice for a first scope, feels like I've read through half the internet but still can't decide. Doesn't seem like there's any astro clubs near me either so I can't see some first hand.

Some background.. in a few months I'll be moving back to SW London (suburbs), so a fair amount of light pollution. At the moment I live close to dark sky areas but won't be traveling much to find them once I move. Mostly interested in viewing planets and the Moon anyway, maybe one day dabbling in astrophotography as well. Basically, I just want the biggest clearest view of Jupiter/Saturn for my budget of around £400 (can stretch this if it would really be worth it). Would love to catch a glimpse of some DSOs but I know they may be hard to see most of the time, so it's not a priority.

It looks like the best choices are the SW Skymax 127 Mak or the SW Explorer 200P. Or maybe the 150PL? (aaaah can't choose!) Not too sure if a dobsonian is for me as they seem to be best suited for DSOs, and I would prefer a scope with tracking capabilities. But I'm all open ears for opinions/advice.

Some specific questions..

- Will the aperture of an 8" Newt give much benefit over the 5" Mak under moderate light pollution and primarily looking at the planets?

- How important is focal ratio? Seems like you can reach high enough magnifications with a 2x barlow and short eyepieces with say the Explorer 200P which is f5. Is there an advantage of not needing such short focal eyepieces to get higher zoom with the 127 Mak??

Hmm I know I had a few more questions but I can't think of them right now. Anyway this post is long enough, sorry you must get threads like this all the time but some specific advice would be much appreciated, even just a sentence or two. I want to make sure I feel happy with my first purchase.

Thanks

[brianb]

Will the aperture of an 8" Newt give much benefit over the 5" Mak under moderate light pollution and primarily looking at the planets?

Light pollution isn't an issue for lunar/planetary work but the extra aperture gets more resolution too. IMHO 6" is about the least which should be considered for planetary work these days, and (quality being equal) 8" is definitely better.

How important is focal ratio? Seems like you can reach high enough magnifications with a 2x barlow and short eyepieces with say the Explorer 200P which is f5.

Yes, but the shorter focal ratio brings some other problems ... collimation is much more critical, and first rate eyepieces are necessary if a f/5 scope is going to perform to its potential, especially for high resolution work on the planets. f/5 Newts are popular because the shorter tube makes them lighter and easier to mount than one with a sensible focal ratio; and you get more in a shipping container.

But, for planetary work, a f/8 or even longer Newtonian will be better. The contrast is a bit higher because the central obstruction is smaller.

Orion Optics (UK) do an f/11 6" Newtonian which would be brilliant for planetary work, especially since you can order it with "research grade" optics (1/10 wave PV) - these will outperform the mass produced optics in Skywatchers, not that they're bad but they're built down to a price point not up to performance potential.

Edit: If you need a more compact scope than that, consider the Skymax 150 Maksutov-Cassegrain - Maks make excellent planetary scopes but the field width is too restricted to make them good general purpose instruments. The Skymax 180 would be better still.... as would the Orion Optics OMC200, with premium grade optics.

[dvd88]

Thanks for the reply Brian. So a larger aperture will give me a better resolution for a given magnification.

Is the f11 Newtonian you're referring to this one?

Dobsonian OD150 L

Looks tempting but again I'm not sure if a dobsonian is for me as I can imagine myself wanting to try out some astrophotography. Would it be possible to put a dob on a mount with tracking some point down the line?

The others you suggested, like the 150 Mak, I had looked at but with a mount they would be out of my budget

[brianb]

Is the f11 Newtonian you're referring to this one?

Dobsonian OD150 L

Looks tempting but again I'm not sure if a dobsonian is for me as I can imagine myself wanting to try out some astrophotography. Would it be possible to put a dob on a mount with tracking some point down the line?

Next page, you want the "de luxe" model with the top grade optics .... unfortunately quality costs money ....

Yes, the tube can easily be mounted on an equatorial mount. The Orion Optics (UK) Dobsonians already have the tube riings, you just need a dovetail bar & you're in business .... and the Dob bearings can stay on for when you want a fast setup.

[John]

My suggestion would be to get an 8" F/6 dobsonian (eg: the Skywatcher 200P). I found the one I had performed very well on planets and double stars (better than I expected in fact) and also had enough light grasp to give nice views of deep sky objects as well - especially globular clusters, the brighter of which were really excellent through it !.

An F/6 focal ratio newtonian is relatively easy to keep collimated and the optical tube can be mounted equatorially if that's the direction you go.

The skies I was observing under were moderately light polluted, probably typical semi-suburban skies.

John

[dvd88]

Thanks for the replies.

Brian, I think the Orion Optics dob is just out of my price range. Maybe one day I'll buy a decent primary mirror make a DIY dobsonian

John, do you encounter any of the problems usually associated with a faster focal ratio? The Explorer 200 spec says it's f5.

Anyhow, I've narrowed down my choice to two scopes.. an Explorer 200 on an EQ-5, or a second hand Skymax 150 Pro (f12 Mak). Which would be best for photography? The Explorer would have better resolution and let me see more DSOs, but what are the advantages of the Mak??

(Sorry for the constant stream of questions)

[A McEwan]

I progressed from the Skywatcher 127 Mak to an 8" f6 Dob for exactly that reason - to see more planetary detail. While the 127 was a first class planetary scope, the 8" Dob showed more detail. Also, it holds collimation easily and is more useful for general purpose observing too. It can go from deep sky to planetary viewing at the switch of an eyepiece. I still love the 127 Mak, but the 8" f6 is just "more" of everything.

Ant