Well, I am a bit peeved.

The weather forecast for Jakarta was for mostly clear skies and this afternoon there were large patches of blue, so I set up the scope. Of course I was being overly optimistic 🙁 .  Clouds, clouds and more clouds !!!  A patch would clear here , then a patch there. It was like that until 10pm when all the clouds suddenly melted away. I thought “you Bewdy” and started taking the frames of the Triffid nebula (M20).  I was aiming to get 20 x 4 minute frames so I would have lots of data to play with, but the clouds rolled in again – and for good, so I only managed an actual 30 minutes of real usage, only about half the integration time from my last attempt.

The following are attempts at editing stacks of 7 x 240s frames @ iso800 with 4 corresponding darks, with also a comparative sub frame.

While taking the subs I was using the UHC-E clip in filter to try to limit the effect of the noise pollution, but there is so much LP it over-rides the picture pretty quickly.  I limited the time to 4 minutes (240s) as this put the histogram on the right 1/3.  I didn’t want to push further than this as I was also hoping to maintain some colour in the stars and I don’t think longer was going to give much more signal to noise due to the temperature of the sensor.

After running the sub frames through DeepSky Stacker to generate the stacked image it was time to try and pull the image out of the murk.  The first editing attempt just used levels and curves until the background noise hit the limit of what I could tolerate..  The second edit I didn’t push it quite as far, therefore the nebula is dimmer, however this time  and I also tried using layer masks to keep the background noise more under control.  This is the first real attempt at using layer masks so it is still a bit ham fisted and I have probably over darkened the background but it is better than habving all the noise I feel.- can only get better with more practice.

M20 does have an associated reflection nebula (blue), however this is at a lower magnitude (fainter) than the main emisson nebula, therefore it gets lost in the light pollution.

I am thinking it is getting time to look at cooled CCD and narrow band imaging, or at least getting away from Jakarta on weekends that are clear – the first is probably going to be cheaper in the long run !