Dob 8 / 10

[Trent (Trent)]

Hey guys, just in the process of choosing my scope once ozscopes restocks. At the moment, I'm going with the 10 dob over the 8, which is $200 less then the 10. So my question is, does a 10 vastly outperform an 8? And is it worth paying that extra amount of cash in buying the 10 or getting a decent eyepiece for the 8?

Thanks!

[mental4astro (Alexander)]

Hi Trent,

Both the 8" and the 10" are good scopes, size wise. The difference between the two is their f/ratio. The 8" is f/6, the 10" is f/4.7. It is like closing down the diaphram of your camera. It improves contrast, but the image is dimmer. So, more light or more contrast is your question. I've used both f/ratios in scopes, in 8" and 10". Where the f/6 is better for the planets, for faint fuzzies, the faster the better, so f/4.7 for me. You can also stop down an f/4.7 scope to what ever ratio you care for, but you can't make a slow scope fast.

The foot print between the two is pretty much the same. What ever hassels you may have transporting one you will with the other, same focal length.

Before you lay down your cash, I suggest you try to get to some 'star party' and see what I mean about the image brightness. Sure a big scope will show more stars, but that is not the only thing. You really will see a differnce when you look through an f/6 and an f/4.5 or f/4.7 regardless of scope size. Really.

Know what you get before you buy, and what suits you better.

Mental.

[Trent (Trent)]

Thanks for your reply mental4astro. I'de love to make it to a star party but will be strapped for time over the coming year or so with university starting, plus having problems with my car at the moment doesn't help things.

My main interest lye's within seeing deep space objects, and thats what I'm really buying the scope for. Thats why i just wanted to confirm the performance between the two, and for deep space viewing the 10 may be the go. Anymore insight would be great.

[DavidU (Dave)]

Yes, the 10" everytime !

[Trent (Trent)]

Ok great.
I've been looking to purchase of ozscopes, as they seem very reliable.
Has anyone bought a telescope / accessories of another website their willing to vouch for?

[barx1963 (Malcolm)]

I have used Andrews, Bintel, Star Optics and Sirius Optics with absolutely no problems. Generally service from our specialist suppliers here in Oz is first rate.

[floyd_2 (Dean)]

Go for the 10". My second scope was a 10" dob and I just loved it. I still wish I hadn't sold it 20 years ago

If the 10" you're interested in has a short focal length, you might want to take a good look through it at night if at all possible. As far as I'm aware, shorter f/l mirrors need to be figured much more accurately. It would be good to be sure that the mirror has been figured well enough to satisfy you, and looking though the scope at night is a good way to find out.

Check the primary mirror cell as well. Some mirrors are glued onto the mirror cell, and the cell is sometimes made of custom wood rather than being alloy etc. If possible, the mirror cell is better to have mirror clips etc rather than having a mirror glued to it (which can cause the mirror to flex).

Some tubes are made from a sort of cardboard too (the old shorty Orion 10" scopes were made from sonotube I think). Try to get one with a rolled metal tube rather than sonotube etc.

Check the bearings on the mount and tube as well to make sure that they run well and don't stick. Bearings can always be tuned / buffed etc, but it's better to star off with a good setup if you can.

I guess that there are a lot of things to keep an eye out for, however I'm sure that you'll make a great decision and that a 10" scope will make your eyes pop! Buying a new telescope is always exciting!

Dean

[JethroB76 (Jeff)]

If you're into DSO's get the biggest you can handle/afford, other wise you'll be looking to upgrade in no time.