Experimenting with Long Exposures

Having finally worked out 90% of the bugs in my observatory I've begun trying some long exposure narrowband imaging.  Until recently all my exposures were less than 5 minutes or less.  Recently I've been experimenting with 10 - 30 minute sub-exposures.  I've noticed that while my tracking is good its essential to have a rock solid autoguiding.  And the payoff it great.  Even from my heavily light polluted urban locale I can still get exceptional detail out of my images.

Over the past month or so I've been imaging a few different targets.  First was NGC 6992, the Viel Nebula.  I started with mostly HA but then realised the signal strength was pretty low; I'm still trying to figure out why. I'm not sure if its the camera quantum efficiency drop off, the filter or just the nebula.  Anyway, I ended up taking about 2 hours of OIII along with 30 minutes of HA and SII.The result is below:

I plan on returning to the Viel at some point but for now IC 1805 is in an excellent location for some imaging.  So despite some persistent clouds and an issue with my autoguider I managed to pick up 15 x 900s OIII exposures. Since I didn't take any HA or SII images yet the image is monochrome.