Sorry i'm back again!!

[Bigdaddyjeff]

I have a similar observing situation. My solution is i) to keep my scopes readily portable so that I can move around the garden to dodge the trees etc and ii) I use refractors on tall tripods a lot which means I don't have to wait so long for objects to clear the surrounding trees and buildings.

The portability criteria is why I've restricted myself to 10" as a maximum aperture.

Thanks John ...It's all about compromise isn't it. The Dob is such a good bargain for the aperture you get which so many of people have said before. I have read a few threads about balancing problems and dew problems with a dob so how easy are these to overcome???

Thats something i have considered Kris, maybe giving myself an area in the moiddle of the lawn,maybe a foot or 2 higher than ground level

How easy is it to make your own Dob mount Steve????

Gaz

[Chris H]

On my 10" Dob the heaviest ep I use is 980 grams when combined with the 9x50 finder, Telrad, Moonlite focuser and dew shield there is quite a bit of weight up the end of the tube but I have no problems with balance I just put a little bit more pressure on the tension handle. No probs with dew either, the primary is way down the bottom of the tube out of harms way and the secondary is protected by the dew shield.

If you do make a viewing platfrom don't make the whole thing from deck board or timber, I found when viewing on my decking at high powers I could see a small wobble caused by my heartbeat.

[swamp thing]

Hi Gaz

It obviously depends on how practical you are but i found it a walk in the park.

Check out Richard Berry's "Build your own telescope" or just type Building a Dobsonian into google there's a wealth of info on it.

Regards Steve

[Bigdaddyjeff]

Hi Gents and thank you, didn't realise the floor would be so sensitive though Chris so i'll certainly bear that in mind should i build one!

I'll take a look at those too Steve and get back to you

Gaz

[pook]

I believe deep sky imaging needs small refractors on big mounts while observing needs large aperture scopes that can be more simply mounted.

Can someone explain to me why this is so? Why does DSO imaging need a small refractor? Why not a fast reflector? Surely gathering as much light as possible is better isn't it?

[rocketandroll]

Can someone explain to me why this is so? Why does DSO imaging need a small refractor? Why not a fast reflector? Surely gathering as much light as possible is better isn't it?

From my understanding (and being a newbie myself, just getting into DSO imaging) the reason small fast refractors are used on DSO imaging is mainly field of view and weight.

With the very long exposures needed for DSO work I think you're best off keeping the load on your mount as low as possible by using as small and light a scope as possible.

The other issue is focal length and er-go field of view. A lot of DSOs are quite large and you simply can't fit them in the f.o.v of a big reflector.

That's my understanding so far anyway!! I'm sure someone will correct me :-)

I've just had to make the same decision and ditched any observing capability what so ever in favour of a good imaging set up based on the Skywatcher ED80 DS pro apo.

It seems you have to decide on one or the other, though a 6" or so newtonian on an EQ6 woul probably be the best compromise between both needs.

Ben

[Whippy]

Can someone explain to me why this is so? Why does DSO imaging need a small refractor? Why not a fast reflector? Surely gathering as much light as possible is better isn't it?

The needs of a scope for deep sky imaging are slightly different to observing in that aperture isn't really a priority.

Larger apertures do indeed gather more light but that's only faster on points of light objects (such as stars), for imaging extended objects (galaxies and nebulae) it's focal ratio that determines how fast you gather the light.

Using a small refrafctor has many advatages, especially for people that are just starting out in imaging. The weight is low so it doesn't make demands on your mount, the focal length is short so tracking errors are kept to a minimum and there's no need for cooldown time or collimation. There are plenty of people using relectors (I'd also class Mak-Newts here even though they're catadioptrics) and they get great results but they are not as easy to use.

Tony..

[pook]

OK.. thanks for that.