Left overs from galaxy season. RGBHa of M51 and M101

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timh
Posts: 515
Joined: Mon Aug 26, 2019 5:50 pm

Left overs from galaxy season. RGBHa of M51 and M101

#1

Post by timh »

A couple of galaxy compositions here. They combine most of the frames that I took over the Spring of M101 and M51 using an 8 inch Newtonian at F ~ 5.0. RGB was collected with an OSC camera and no filter. HA collected using a mono camera with the image then added into the red channel.

In each case about 2/3 of the frames were collected on moonless nights from a Bortle 6 site and the remainder on a moonless night from a Bortle4 site. The final integration was weighted according to the measured SNR. Thus, despite constituting only a third of the total, the weighting of the dark sky frames meant that they contributed about 70% of the final signal. The Bortle 4 SNR was about 4 fold higher than at Bortle 6. However seeing was relatively poor at the Bortle 4 site. Thus the pictures are weighted more towards trying to detect the full extent of the galaxies rather than towards getting high resolution to the core.

SW200 PDS Newtonian, Baader flattener F 5.0. CEM70 mount, ASI120MM guide camera (50 mm, f = 160mm guide scope)
PDH2 guiding, Sharpcap (livestack) capture, PixInsight pre and post processing

ASI294 PRO MC camera, gain 124 at -10C
ASI294 PRO MM camera, gain 124 at -10C

Optolong 7nm HA filter

Image 1 of M51 is 210 x 40s plus 54 x 70s RGB frames plus 9 x 3 min of HA

Image 2 of M101 is 243 x 40s RGB frames plus 19 x 3 min of HA

Image 3 of M101 is the same as 2 but without HA and also annotated

One thing that I learned from this was that darker skies make an enormous difference to how quickly you can get to a high SNR image ...BUT ..it also helps if the seeing is good.

Tim
Attachments
CaptureM51_3.JPG
CaptureM51_3.JPG (70.42 KiB) Viewed 702 times
Capture_M101_2.JPG
Capture_M101_2.JPG (147.46 KiB) Viewed 702 times
Capture_M101_3.JPG
Capture_M101_3.JPG (190.66 KiB) Viewed 702 times
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Menno555
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Re: Left overs from galaxy season. RGBHa of M51 and M101

#2

Post by Menno555 »

Whish I had left overs like that :)
Darker skies are something I still have to try with my setup but can imagine it makes a difference.

Menno
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oopfan
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Location: New York
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Re: Left overs from galaxy season. RGBHa of M51 and M101

#3

Post by oopfan »

Tim, I love your M101. I tried it a couple years ago. Disappointing. I gotta get me a bigger aperture!

Brian
timh
Posts: 515
Joined: Mon Aug 26, 2019 5:50 pm

Re: Left overs from galaxy season. RGBHa of M51 and M101

#4

Post by timh »

Thank you for the comments. I was pretty pleased with the M101 images especially since much of it is quite faint - never quite sure how far to go with imaging time and at what point it is just diminishing returns. The annotation tool is useful I think because it defines a circumference for each galaxy and I suppose that when your picture approaches that then there is not much further extent to find. The fast optics also help but it is quite a big set up to travel around with.
Tim
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