DSOs: what magnitude is viewable and what eyepiece is best

[209herschel (Herschel)]

Hello everyone,

I have a GSO 10" Dob.

I started looking only at the moon and planets but ever since my setting circle mod made things easier to find, I'm really enjoying the search for DSOs.

My question is what magnitude object can I expect to see from my inner city Sydney backyard? I know it depends on my particular conditions but I've been moving through the Messier list and the best I've done so far is around magnitude 9, a cluster. I've seen very faint things up to 10 but I can't even be certain it was what I was looking for, it was that dim. I looked for the Saturn nebula a couple of nights ago and I couldn't see it. I've never been to a dark site before so I was wondering what magnitudes one can see in great conditions? I'm not disciplined enough on keeping my eyes dark adjusted and I wanted to ask how big a difference this makes?

The second part of my question relates to the eye piece to use. I know there's a trade-off between magnification and the amount of light you eye takes in, so is there a technique of getting to the more faint DSOs and is it a matter of trying different eps on different occasions.

Thanks again in advance for any assistance.

Herschel.

[Renato1 (Renato)]

With a 10" dob and an eyepiece giving a 2mm exit pupil, pretty much every DSO plotted in Sky Atlas 2000 will be visible at a dark site, though you'll also need a nebula filter for many of the tiny planetary nebulas to distinguish them from stars.

In a light polluted back yard, every DSO plotted in the much smaller Bright Star Atlas will be visible.

In a light polluted backyard, the dimmer open and globular plotted in Sky Atlas 2000 can be more easily seen than galaxies.

Some people prefer 3mm exit pupil eyepieces for viewing faint stuff. But I've always found a 2mm exit pupil best for galaxies at a dark site, and 1.8mm at a light polluted site.

You will be in for a treat when you do go to a dark site.
Regards,
Renato