M31 Andromeda Galaxy

[UKJay1971]

This is first light on my newly modded Canon 100D, taken from my light polluted backl garden in Wakefield. It's been 6 months since I began imaging and I'm pretty chuffed to finally get onto Andromeda. I do have an issue with some odd streaking (zoom on on a border on the spiral or in the background). I get also get it on my Altair 178c and on all my scopes so I can't put my finger on what is causing it other than light polluted skies - any ideas?

100 x 180secs, 30 darks, 20 flats

 

M31 Andromeda Galaxy by Jay Bolt, on Flickr

[tooth_dr]

11 minutes ago, UKJay1971 said:

This is first light on my newly modded Canon 100D, taken from my light polluted backl garden in Wakefield. It's been 6 months since I began imaging and I'm pretty chuffed to finally get onto Andromeda. I do have an issue with some odd streaking (zoom on on a border on the spiral or in the background). I get also get it on my Altair 178c and on all my scopes so I can't put my finger on what is causing it other than light polluted skies - any ideas?

100 x 180secs, 30 darks, 20 flats

 

M31 Andromeda Galaxy by Jay Bolt, on Flickr

 

I used to get this streaking, and once I started dithering my exposures it disappeared. If you can do this it'll also do wonders for overall noise.

 

Thats a fabulous image..

[wimvb]

Nice image. The streaks are called walking noise. They're caused by residual hot/warm pixels that were not removed during image calibration. Darks, or a hot pixel map can help. So can cosmetic correction in dss or pixinsight. You can avoid them by dithering (= moving the fov slightly between exposures) during data collection. For cmos osc sensors, dither 12+ pixels in ra and dec.

[UKJay1971]

That makes sense - I had thought I had dithering switched on in BackyardEOS but it might not have been working, or not as strong as it needs to be. I don't get any streaking when I image in SGPro.

Thanks!

[bobro]

Beautiful image! How do you reduce the light pollution effects?

[John78]

Given the amount of colour you've got your "light pollution" is nothing like my LIGHT POLLUTION!

 

Good effort.

[John78]

Oh, and to re-confirm the other answer in the thread with a cmos camera you want dithering when shooting, 0 darks and sigma clipping when stacking and master bias as dark.

[UKJay1971]

Thanks for the comments

Wakefield has some of the worst light pollution in the UK (surrounded by other major towns / cities plus the M1 / M62 motorways. I use a CLS filter in my DSLR (just bought a CLS CCD 2" filter to notch some more LP bands out), and also stack a lot more images - this is 100. To draw out the data, I used a series of masked stretches that allowed the outer spirals to be stretched while progressively protecting the core. The most important skill I have learned was how to use masks in processing.

[tooth_dr]

50 minutes ago, John78 said:

Oh, and to re-confirm the other answer in the thread with a cmos camera you want dithering when shooting, 0 darks and sigma clipping when stacking and master bias as dark.

See this was what I wasn't sure about. Do you use the master bias as an actual dark in DSS or just as a bias and use 0 darks in DSS or use Bias in both bias and darks ?

[UKJay1971]

I never use bias frames - they certainly knacker my CMOS frames (introduce amp glow rather than help calibrate it out) and, as my DSLR is also a CMOS sensor, I don't use them. I do use darks and flats and they seem to work ok

[stepping beyond]

Kudos on Andromeda and surrounding galaxies.

 

[Allinthehead]

That's a great job from light polluted skies.