DSOs from Punggai

[Meng Lee]

Here are some pics taken from Punggai (on the 2nd day). Hope you all enjoy it:

1) Omega Centauri



2) Lagoon Nebula



3) Eagle Nebula



Thanks.

[swimaniac]

Nice shots. Glad the trip turned out well.

Waiting to see more.

[cataclysm]

Nice images Meng Lee ! Care to share your imaging info ?

[Meng Lee]

Hi,

Here are the info:
1) Scope: William Optics 80 FD with 0.8x reducer
2) Camera : Atik 16HR
3) Omega Centauri : 6 x 3mins (Clear filter)
4) Lagoon Neb : 4 x 15min (Baader H alpha filter)
5) Eagle Neb : 4 x 15min (Baader H alpha filter)

[zackae]

wooh great shots! Would be great if there are some colours in the picture. Some noise are apparent in a few photographs. overall great job, love the details in the Eagle.

[rcj]

how come it looks noisier here than on screen during our trip? hmm.... btw, the stars show some radial distortion. is the reducer effective? how about trying the 0.67 telecompressor from AP? Focus is good.

[Meng Lee]

Oh, on the screen the zoom is 1:2 and the pics here are 1:1 and the noise increased a little due to high pass sharpening.

The distortion is due to that the chip to reducer distance is too large. So need custom T-adapter to get the right distance.

[rcj]

don't quite understand...if the on-screen was 2:1 and now is presented in 1:1, the noise should be less evident. but the on-screen view felt quite similar to what is presented here. also, my comment on the reducer effectiveness was prevalent because if you look at ngc5139's stars at the top right corner, they are curved and distorted more than those stars at the bottom left corner. this is asymmetric already, so even if the reducer distance is incorrect, the distortion extent should be similar at all edges. the effect is similar for the last image (M16). hence, from these observations, the image train could be experiencing flexure somewhere. notice also that the HA image for Lagoon does not exhibit this. it should, but it didn't. was the dynamic range fully explored? looks 8-bitish. but the images are well calibrated though, black and white points fully taken care of.

[Meng Lee]

This is Omega reprocessed with the choice of alignment stars chosen close to the cluster and not at the edges. This gives rounder stars for the cluster and the edge distortions are more symmetrical. The remaining asymmetry is due to that the pic has been cropped to centre the cluster.



So for the eagle neb, I will reprocess with alignment stars chosen near the neb. For the H alpha images, the SNR is still really low though its 15mins exposure. So when I stretched the images over the full dynamic range, the noise becomes evident as it is quite close to the signal level. 4 frames only allow a 2 times SNR boost. Subframes need to be really exposed longer as you said.

[rcj]

this image is much better! but the reducer performance is not optimal. sigh.