Left overs from galaxy season. RGBHa of M51 and M101
Posted: Wed Jun 23, 2021 1:31 pm
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
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
