IC 10 - Starburst Galaxy in our local group

[GalaxyGael]

This is the penultimate image from my Intes MN56 Maksutov Newtonian (127 mm / 762 mm). It is the dim but interesting galaxy IC 10, a very active starburst galaxy in our local group.  You must image through the plane of the milky way. Somewhat similar to the small magellanic cloud but packed with Wolf-Rayet stars.

I decided to stop at just over 8 hours data, which took 5 weeks due to the weather and an f/6 scope. This week (Aug 24-28) has great weather, but a full moon (and getting first light on another scope), so I called it a day for IC 10 for now.

4.2 hours OSC using ASI2600MC Pro, -10C, Gain 100, no filters aside from the UV-IC cut on the camera. Subs were 240 s. Stars as they are.

I added 4 hours Ha data using altair quad band filter with the OSC. I extracted Ha (which is noisier than mono due to green and blue pixels ignored) and added the Ha stack with split RGB channels using Astropixel Processor.

Gentle tweaks in PS CS5. Bortle 5/6 location with LED street lights pouring in to the backgarden.

15 px dither for every frame.

Master flat used, no darks.

This would be a great target for a f/5 longer focal length system, and Ha (7 nm or narrower), R, G and B filters with a mono camera. Still, I think it came out quite nice.

 

[vlaiv]

23 minutes ago, GalaxyGael said:

Master flat used, no darks.

Any particular reason for skipping the darks?

Luckily, you have set point camera and you can create darks and apply them later on. Maybe give it a go and see if it improves your result.

[GalaxyGael]

Darks rarely needed for the imx571 chip, and I tested with and without with no obvious difference from the library I made before finding out more about this system. Almost no electroluminescence glow and comparing darks with different gain and exposure is very different to most previous cmos generations. It's an interesting back illuminated cmos junction layout. 

There is a little more noise from the extracted ha from the osc compared to the rgb osc 4.2 hours data. H alpha from a mono cam would be nice. I might use the ha-o3 data from the filtered osc together as a mono luminance layer in this image someday as a comparison experiment. 

[vlaiv]

40 minutes ago, GalaxyGael said:

Darks rarely needed for the imx571 chip, and I tested with and without with no obvious difference from the library I made before finding out more about this system. Almost no electroluminescence glow and comparing darks with different gain and exposure is very different to most previous cmos generations. It's an interesting back illuminated cmos junction layout.

Darks also contain bias signal that you should remove, even if dark current is very low and there is no significant amp glow.

 

[GalaxyGael]

Indeed, I know. Bias-calibrated darks did not make a perceptible change to my eyes. When I run short exposures and lots of them, with only periodic dithering every n-th sub, I do notice the benefit of bias-calibrated darks in nebula images at low gain, but longer exposures on this chip for me, with 15-20 pixel dithering between each sub, make the dark vs no-dark surprisingly similar at the whole image scale even when the bias persists. Its quite a leap compared from the asi1600 OSC chip, which was sometimes troublesome with flatdarks etc. 

 

[Padraic M]

Very nice shot Colm! It certainly is faint - I took a peep at it myself last night but got absolutely nothing in 10 minutes of Ha (f6.3 C8 @1340mm), and RGB is almost a waste of time in Dublin skies. I moved onto a brighter target.

It's one I'd love to try from dark skies.

[wimvb]

That came out very nice. I've seen this galaxy tagged in star charts, but never an image of it. Thanks for sharing

[GalaxyGael]

Thanks Padraic, similar situation. Even the first 2 hours were woefully dim and the image above is a crop to 50% of the whole frame area. Then something appear after 3 hours, a bit more after 4 but that took weeks with bits of clear sky. A case of 'I've come this far, I will do some more'. Had plans to go to 20 hours figuring some maths on the SNR, but added Ha because this week clear skies are full of moon.

Cant remember when I looked up at the night sky when in dublin, but I guess you have light pollution in all directions?

[GalaxyGael]

Thanks Wim. I cannot recall why I chose to try and image it, but I did measurements on it years ago in IR and maybe it was in the right part of the sky when planning what to image...images of it are rare enough, a few with longer focal length and a lot of very tight Ha data. Its much better in IR, and also in Ha if the image is very deep (as in Chile Atacama scope deep), where the Ha surrounds the galaxy for a huge region of space.

[Padraic M]

7 minutes ago, GalaxyGael said:

I guess you have light pollution in all directions?

Unfortunately yes - Bortle 8 at best. NB works well, but WB really not a runner. Had a few weeks in Kerry recently and really noticed when I got back how few stars I can actually see naked-eye in Dublin.

@wimvb this might be an option for some of those long Swedish winter nights! I presume it's circumpolar for you at +59 degrees?