NGC 1964 - a rarely imaged galaxy in Lepus

[wimvb]

NGC 1964 is a small galaxy in Lepus. Its distance is about 65 MLy. The photons that formed this image left this magnitude 10 galaxy when dinosaurs still roamed the earth.

This object covers about 5.5' x 2' of the night sky. A google search turned up very few images of this object, and most were of poor quality.

Data from the Liverpool telescope, La Palma

Blue: 12 x 75 s

Green: 14 x 75 s

Red: 14 x 75 s

Total integration time approximately 50 minutes @ D = 2 m, f/10

Despite the number of subs and the total integration time, most of the details barely cleared the noise floor, especially in the blue channel. Hence the strong reflection donuts from the primary mirror.

Suggestions for improvements welcome.

(Click the image for a larger version)

[gorann]

Hi Wim

I had a quick go at your image in Photoshop, just pulling a bit on the curves for the different channels (masking off the stars with the reflections not to make those worse). That brought out more blue in the galaxy and probably also improved the colour of many of the stars. The reflections are more difficult. I would have tried clone-stamping them out from the blue data before I merged it into an RGB. I assume there is something like clone stamp also in PI? I do not mind clone stamping as long as it is used in a fight against artifacts and not real things.

[gorann]

It is also possible to suppress the blue rings by suppressing the blue and cyan saturation, like this, but I am not sure it is the best way or if it looks any better

[wimvb]

Looks better. I'll reprocess this image. When I tried boosting the blue, all I got was uggly rings around some of the brightest stars in the galaxy, and a few uggly blue patches in the galaxy itself.

I don't mind the reflections too much, since they don't intrude on the target. Your reprocess also shows that I have to clean up the star cores.

[gorann]

As you know, I have not started on the PI track yet, but it looks like your colour balance went the wrong way somewhere as many of your stars look too orange. I do my colour balancing totally manually as I stretch each colour separately, put them together and then tweak the curves for each colour a bit until it looks ok (often looking at the stars, making sure there are at least a few pure white ones in there). Very non-scientific approach, and sometimes I realize I have to start over with one or more of the colours.

It is interesting with these striking blue ring reflections in the multi-million-Euro Liverpool Telescope. If we got that in one of our one or two thousand Euro scopes, we would be very upset and send it back. Maybe it was too big and heavy to send back....

[wimvb]

I went over my process history, and found out that I had included the bright star below the galaxy in the colour calibration process This threw the colour balance off, as you just noted.

Am doing the reprocess now. At the same time, I correct the star cores of the brightest stars.

The advantage of PixInsight is that it saves the complete process history, including the settings of all methods. Redoing a process is so easy.

[wimvb]

reprocessed, with better colour calibration and repair of star cores. 

(click to enlarge)

 

[MikeODay]

Very nice image Wim. 

[gorann]

Yes, that is more like it! Nice one!

I get the feeling that PI processing is more automated that PS so you need to get all the setting right before pressing Run. However, there is History info also in PS, but I rarely look at it.

[wimvb]

In PixInsight, I can get the image history in two ways:

1. if I save the project, all relevant files (masks and processes) are saved with the image(s),  including full history. I can load a previously saved project, hit ctrl-Z or ctrl-Y for undo and redo.

2. I can save the process history of an image as a process container on the workspace. If I then select a process from this container, it opens up the process with the exact settings that were used. I can save a process container with a default workflow for, say, OSC, or LRGB.

I wouldn't call PI automated (as in 'just press Go'). E.g. there are 17 different stretching methods, each with its own setting controls, and 6 different noise reduction methods, also each with its own setting controls. Like I wrote before: PI is like a mixer table in a sound studio.

[simmo39]

Another fine image Wim.

[wimvb]

Thanks, Simmo

After Görans tweaks, my reprocess turned out better than the original, I think. It clearly shows that making one small mistake in the beginning of a process, can lead to serious trouble in the end. 

[Rodd]

The most amazing aspect of this image are the ridiculously small amount of data! Only a few  few 75 second subs!  amazing (and the processing of course).  A mega mosaic with the LP telescope would be something to see (hint)

Rodd

[wimvb]

Unfortunately, that hint is lost on me; I would love a mosaic. But you'd need to convince the telescope operator. There are actually a few mosaics from this scope. M51 is a two panel, and M106 is a four panel mosaic. I've also seen panels for M101 and M16. But the real charm is in all these small galaxies that hardly ever get imaged. Nice to see other targets than the M-series.

The challenge with the LT images is not so much the lack of data. Since the primary mirror is a whopping 2 m across, and the sensor has real photon buckets with 15 micrometer pixels, there isn't lack of data. But with this data also comes a lot of noise (despite the low temperature at which the camera is run). Another problem is the high rate of cosmic rays hitting the sensor. Various targets have Ha data as well, but often this is limited to single subs. The absolute minimum I have managed to pull something out of is 5 subs per channel. Anything less, usually is too noisy to bother.