IC1396 in Ha - WIP

[alan4908]

Given that we have infrequent clear nights in the UK, I'm always interested in exploring ways of increasing my imaging efficiency. So, recently, I acquired 7 30mins Ha subs of IC1396 but I noticed that quite a few of the subs had eggy stars (see below - I think it may have been windy).  Rather than discard some of these, I'd thought I'd explore if I could somehow use these in an image stack but in a way that wouldn't erode image quality.  After a bit of research and considering that I had only 7 subframes including quite a few dubious ones, I decided to use the Poisson Reject algorithm in CCDstack. A feature of CCDstack is that you can see which pixels are marked for rejection within an individual sub frame. This is useful since it allows you to experiment with different rejection strengths and visually see what is going to be rejected.  So, since I had about 5 eggy subframes and I was keen that my stars should end up round, I decided to set it to 5 iterations which means that it can reject up to the 5 pixels in each 7 pixel stack.  After a bit of experimentation of seeing which pixels where being marked for rejection, I also decided to instruct the algorithm it to reject about 1% of all the pixels within each individual subframe. I've put the stacked result in quite a high resolution below. 

Alan

 

 

 

[Allinthehead]

Nice image and workaround for dodgy frames.

[newbie alert]

Nice image Alan.. what did you use,kit wise please?

[alan4908]

10 hours ago, Allinthehead said:

Nice image and workaround for dodgy frames.

Thanks for the comment Richard. 

2 hours ago, newbie alert said:

Nice image Alan.. what did you use,kit wise please?

Thanks - the image was taken with an SW Esprit 150 on a 10micron GM1000HPS, the camera was a SX-814. This combination gives an image scale of 0.7 arc seconds/pixel.

Alan

[newbie alert]

Very nice too...what HA filter was you using?

[alan4908]

11 minutes ago, newbie alert said:

Very nice too...what HA filter was you using?

A 3nm Astrodon - which I've found is excellent at maximizing image contrast. 

It also helps at increasing imaging efficiency, to explain: since it's very narrowband, it's very good at rejecting light pollution.  This allows me to image DSO objects that are quite close (in an angular sense) to the moon and still achieve a satisfactory result.  I use this fact with my ACP controlled observatory which I've programmed to only acquire Ha images when the moon is up and a certain angular distance away from the moon. Since I can get quite close, I can acquire more images for a given quality threshold.

Alan