Upgrading from cheap refractor?

[maxwolfie (Greg)]

Hi all,

We have a Sky Watcher SW708 (http://www.tasco.com.au/Products/Cat...uctID/770.aspx) however it is a bit (very) limiting as to what we are able to see in our heavily light polluted city (Sydney, Australia).

Ideally we want something that will allow us to see a bigger and clearer Saturn, some galaxies, a very detailed moon and hopefully be able to make out some of the easier to see nebula (as well as whatever else is interesting). We haven't gotten around to getting up early to see Jupiter, Venus or any other planets though. We'd obviously like something that will do a good job with these, too. I have been told by my local shop that simply upgrading may result in disappointment, as dark skies are generally required. We want to be able to see a pretty substantial improvement or else we probably won't bother.

Portability is something that needs to be considered as we visit my inlaw's farm (dark site) every couple of months, however we won't be moving it around all the time so not a major issue. Ideally something that is quick to assemble to chuck in the car and easy to put back together again once there. The rest of time it will be stored no more than 10 metres from where we observe from, no stairs or anything difficult to navigate either. We are young (26) and fit so maneuvering it around isn't really an issue...

Another thing I should mention is that I also do a bit of AP with my Astrotrac and my DSLR. I guess the idea is to try the SW708 on the Astrotrac and see how it goes with Eta Carina, Trifid etc, and observe with whatever the new scope will be.

At the moment it is difficult to see anything other than planets. And even those are quite small and lack a lot of detail. I can make out Saturn's rings but I can't make out the Cassini division.

I guess the question is, what else can I be sure to see with a better telescope, that I can't see with the little refractor?

Considering an upgrade but not sure what, budgeting around $300-$400. Suggestions?

[GeoffW1 (Geoff)]

HI Greg,

I too have been down this path. In Sydney nowadays you will always be flat out seeing any galaxies, and none but the brightest nebulae like M57 and M42. I can't now with a 200 mm scope.

I've tried a 300 mm dob reflector in the past, and found that not portable enough to travel with, then a 100 mm refractor, which was quite portable, but it lacked the aperture I wanted at dark sites. I now use a 200 mm C8, a Schmidt Cassegrain. It is easy to collimate, quite portable, and has a bit of power.

So with something like that, 200 mm to 250 mm aperture, at a dark site, you will get a good view of all the well known objects.

Now, the cost, most important. With the budget you plan, you will will get the most scope for the money in a 2nd hand dob reflector, and paying attention to portability and speed of setup, I reckon a 200 mm dob is the way to go, since you intend it for visual use. It will still be portable enough. You can also fit it out with a push-to kit like Argo Navis (the best option I think), and that can be transferred to a future scope.

eg http://www.iceinspace.com.au/forum/s...ad.php?t=94746

Cheers

[MattT]

The 10" dobbie in the classifieds for $400 is a bargain will be able to see lots with that.

[sil (Steve)]

I like my Celestron 114EQ now that I bought some better eyepieces (Baader Hyperions). The eyepieces that came with it are pretty bad and I thought I'd bought an unusable scope, but with good eyepieces its so incredibly clear. The same eyepieces in my celestron FirstScope I am able to make out Saturns rings (just, no Cassini obviously). Cassini division and Jupiter bands and Saturn/Jupiter moons are all visible to me in the 114EQ. Collimation is still letting me down and I know the scope has more to give. I'm still learning so I haven't looked beyond the solar system except at a few open clusters so I don't know how well it performs observing beyond those. I think it is a pretty capable and good value scope (under $350), not enough magnification (is there ever?) but should be around double what your current scope delivers at similar f. I'm still toying with getting a decent cassegrain + eq5/6 combo for astrophotography but the 114EQ sits near the back door and is easy for me to (carefully) pick up and carry outside for visual sessions.

[cjamo9 (Clinton)]

if you are going to get a reflector make sure it has a parrabolic mirror not spherical. unfortunately most of the cheaper ones like the celestron ones have spherical mirrors cause they cost a lot less to make. if you are planing on doing a bit of ap. avoid the celestron 127 eq reflector. it has another lense in the eyepiece holder to achieve a longer focal lenght than the short tube can deliver and a spherical mirror. this type of scope is called a jones bird scope. and this is what it does to pics. looks a lot better when you just look through one though.

[Shiraz (Ray)]

Agree with Clinton that you make sure it is a parabolic mirror if going for a Dobsonian.

However, don't get too hung up on spherical mirrors per se. Jones Bird scopes (like the small Celestrons) can work pretty well - although as Clinton's image shows, performance can be sensitive to camera placement if you want to do AP. However, even the top line Celestron and Meade SCTs - and all Maks as well - use spherical mirrors with correctors of some form, so there is nothing inherently wrong with scopes with spherical mirrors.

To answer your original question, an 8 inch Dob will be only a bit over your budget and give you much better views of the planets and the moon, but heavy light pollution will still limit views of DSOs. Will do well at your dark site though.

[Poita (Peter)]

I have a fork mounted C8 you could borrow if you want to try that out to see if that might suit you. Easy to transport and is great for the planets.
I'll be in Sydney in a couple of weeks time and I could meet you somewhere and you can borrow it for a month or two.

[maxwolfie (Greg)]

Thanks all for sharing your knowledge, thanks also Peter for the offer. I'll have a think about what I want to do

[Poita (Peter)]

No problem, it is just taking up space here, I'm happy to see it get some use, I'm not after a sale.
It might help to have a look so you can see what an 8" scope gives you.

These are some images from a C8 with a webcam.
http://astrogazer.us/jupiter2006.htm
and with a DBK21 camera.
http://www.flickr.com/photos/jasmel90/6275849504/

[maxwolfie (Greg)]

Originally Posted by Poita

No problem, it is just taking up space here, I'm happy to see it get some use, I'm not after a sale.
It might help to have a look so you can see what an 8" scope gives you.

These are some images from a C8 with a webcam.
http://astrogazer.us/jupiter2006.htm
and with a DBK21 camera.
http://www.flickr.com/photos/jasmel90/6275849504/

Looking good!

Would it be fair to say that observing through an 8" Dobsonian (which I believe is essentially a "ground mounted" Newtonian?) is comparable to looking through a C8 - which I think is an SCT? Both different types of Newtonians?

[maxwolfie (Greg)]

Dob bought

[Shiraz (Ray)]

good decision Greg. If you haven't used a Newt before, make sure you work out how to collimate it to get it to work properly.