Torn between a large aperture Dob and smaller scope with tracking mount

[Chris Stacey]

As Ben has said the main difference is colour. The colour is nothing like you see in photographs but more colour is apparent the bigger the aperture.

Did you upgrade from an 8", or jump straight for a 16"?

[Doc]

I had a 10" hardin dob I borrowed from a mate.

The 10" showed hardly any colour. The 16" shows stars in clusters that were to dim in the 10" dob. And will show alot more nebulosity in objects like the M45.

A 16" will show you alot of objects but there is no substitute for dark skies. A 10" will beat a 16" if the 16" were under light pollluted skies and the 10" under dark skies.

[Chris Stacey]

That's handy to know, Doc. Cheers.

[Ben Ritchie]

Chris, I wouldn't rule out a move from 8" to 12", I consider it well worth it - you just probably won't be saying "wow" the first time you look through it, it's more of a gradual appreciation of the extra aperture.

As well as cost (as you say, a 12" is considerably cheaper than 16"), I think 12" is probably as large as you can get while remaining manageable in solid-tube form - 14" maybe, if you're big but i've seen a 16" solid tube and it's a beast. My 12" is luggable rather than portable, but I can still get from shed to fully setup inside two minutes, leave to cool down for an hour or so if the shed's warm, tweak collimation and go - it really is very convenient, and i'm a firm believer that the "minimum effort" setup is the one that gets used the most. With a 16" truss you have a fair bit more work to do to get up and running. So there are advantages too.

In the right conditions though there's nothing like sheer aperture, I was lucky enough to spend some time with a 20" (or possibly 24", I forget ... big anyways) Obsession in the Arizona desert and that was stunning. The ladder to reach the eyepiece was a bit scary in the pitch dark though...!

[Ben Ritchie]

A 10" will beat a 16" if the 16" were under light pollluted skies and the 10" under dark skies.

Indeed. I think O'Meara did the whole Messier catalogue and a large chunk of the Herschel 400 with a 3" refractor! Of course, pitch black sky high on Mauna Kea probably helped a bit... in my light pollution things like M74 are so far invisible in my 12"

[Chris Stacey]

I certainly understand what you say about gradual appreciation - I was one of those naive enough to think I would have hubble style images staring back at me the first time I looked through my dob. lol. I soon got over that wake-up call. So I think I'll soon appreciate the subtle differences moving up to a 12".

It's funny you should mention the really big dobs - I talk to a gentlemen on another board (worked on the apollo missions), he uses a 24" obsession. It was talking to him that made me seriously consider a major jump in aperture. That said, I like ease of use, and to be up and running in minutes - plus I have a small house, garden and even smaller shed. The 12" would probably be more practical.

Thanks Ben, you've given me food-for-thought.

[Ben Ritchie]

I think the whole ladder thing would put me off ever going really large, but the fast (i.e. faster than f/4) 18" or 20" dobs are a nice long-term dream - the fast focal ratio means that the eyepiece is still just about usable at zenith without needing anything bigger than a small box to stand on. Expensive though, and you certainly need your cub-scout collimation skills badge to get the most out of something that quick. So for the next few years the 12" will do me just fine

Sorry to the OP for deviating off-topic a bit

[Chris Stacey]

Sorry to the OP for deviating off-topic a bit

That was my fault, sorry spud.

[John]

Another factor to consider is the old saying "the best telescope is the one that you use most often". I was reading a thread on the Cloudynights forum the other night in which a guy with a large dob (18" or so I think) was saying how great it was even though his local viewing conditions were only good enough a few times a year to justify setting it up.

Personally, no matter how fine the occasional views are, I'd hate to see that much gear and tied-up investment not being used a fair bit more than that !. Probably better to join a club that has the use of a large scope.

John

[Whippy]

Indeed John, wise words . I think there's another couple of points that need to be said.

If there's a budget of £700 and no more, make sure you have some spare cash left over from the scope purchase to buy some accessories. Most scopes come with EP's that work but buying a couple of better ones can transform your setup.

Also, astrophography is frankly one of the most frustrating, time consuming and potentially expensive hobbies that you can do. Believe me, it's a rabbit-hole that only gets ever deeper before you have to stop yourself! I'd say newcomers would be best sticking with visual to start with before making that jump to imaging, the relatively limited opportunities to get out there should be enjoyed, not be an excercise in head scratching.

As for a recommendation? My own personal preference is for an equatorial mount so the 8" reflector on an EQ5/HEQ5 would be my favourite. It's big enough to show you loads of objects visually and when you want to start down that rabbit hole, you won't need a comeplete new setup like you would have to do with a dob.

Tony..

[acey]

Spud - looks like you're thinking 8" dob, if I read all this right. That would be a good choice. You can get one for less than £300, which leaves plenty of money for eyepieces, maps, warm clothes and petrol.

My first scope was an 8" dob. After using it for about 8 years I recently upgraded to a 12". I'm glad I upgraded and glad I waited.

My advice would be start with an 8". You never know how much light pollution you've really got until you start observing, but an 8" is easy to transport. (Though when I first got mine I thought it was enormous). It will only occasionally need collimating (even if transported frequently).

12" needs collimating every time you use it. Easy if you've learned the ropes painlessly on an 8". Otherwise a nightmare.

8" from a dark site will show all the Messiers and all the Caldwells above your horizon (I've done it). You can see the M51 spiral arms once you know what to look for. First views will probably be disappointing, as with any scope.

10" will show 0.5 mag fainter, 12" will go 0.9 mag fainter than 8". Whether this is a wow depends on what you're doing - I've only had a couple of sessions with the 12" so far but for me it's a wow.

I'd say get 8" with a view to upgrading to a 12" well down the line if visual DSO turns out to be your thing, or upgrading to something else if imaging is your thing. But an 8" pulls in enough to potentially last you a lifetime.

The one thing you don't want to do is buy as much aperture as you can afford. That only made sense in the days when 8" was as much as most people could afford.

Andrew

[Spud]

Wow, so many replies I'll have to thank you all en masse.

To those worried about this thread going off topic, in my view it hasn't, so carry on. The Dob size question is something that's on my mind anyway, so you've saved me having to ask.

This thread has given me loads to think about. Although I'm craving for a scope, I'll definitely wait until I've tried looking through a few Dobs and other Newts on EQ mounts.

Cheers