Messier 88 and 91 - Spiral Galaxies in Coma Berenices
Two spiral galaxies from the Messier catalogue lying in Coma Berenices. Imaged over 2 nights which is a rarity for me in cloudy Northern Ireland.
Messier 88 lies top right and is a classic spiral galaxy. It measures 6.9 x 3.7 arcminutes. A supernova was detected there in 1999.
Messier 91 lies bottom left, it is a barred spiral galaxy and is classified as "anaemic" - see below! It measures 5.4 x 4.3 arcminutes.
Both galaxies lie in the Virgo galactic cluster which comprises many thousands of galaxies moving at speed under the influence of local gravity. Eventually, they will all collide at the local centre of gravity.
Tenuous hot gases and dust lie inbetween the galaxies forming a hot intracluster medium. As the galaxies race through the resistance of the medium, ram pressure stripping shears their own gas away and leaves them increasingly incapable of forming young new blue stars.
Messier 91 shows this effect more than M88 - it is pale and yellowish for a spiral galaxy - hence anaemic!
Some interesting small galaxies are seen in the field including on the mid right border, a small irregular spiral galaxy - IC 3476 which appears disrupted - probably by approaching too close to a larger galaxy in the past.
Technical Card:
900/120mm f/7.5 Equinox ED doublet refractor.
Skywatcher x 0.85 FR with 2 inch IDAS LPS P3 filter
MoonLite electronic focuser
Astro-modified Canon 80D at ISO400; 26 x 10 minute subs
QHY PoleMaster for polar alignment.
NEQ6 pro mount with Rowan belt drives -2 star align.
Camera control with Backyard EOS
Post processed in PixInsight 1.8.8
60 Flats EL panel: 1/40s @ ISO400
Master Dark from Dark Library, 50 x ISO and Temp. matched.
Master Bias from Library, 03/2021
Camera sensor temperature (external battery): 12-14c
Local parameters:
Temp: 7.0 - 9.2c
Humidity: 55.4%
Pressure: 1010 hPa
Light Pollution and Weather:
SQM (L) at end of session night 1 (0110 hrs UT) =20.33 mag/arcsec2. Clear both nights throughout - no subs lost due to weather.
Astrometry:
Center (RA): 12h 33m 40.785s
Center (Dec): +14° 24' 26.77"
Size: 1d 01m 58.9s x 50m 35.3s
Image scale: 0.977 arcsec/pixel
Focal distance: 792.08mm
Pixel Size 3.75 microm
Polar Alignment:
QHY Polemaster alignment -
Error measured by PHD2= 2 arc minute.
RA drift + 2.07 arcsec/min
Dec drift + 0.52 arcsec/min
Guiding:
PHD2 guiding with ZWO ASI290mm/PrimaLuce Lab 240/60mm guide scope. Every 3rd shot dithered.
RA RMS error 1.3 arcsec.
Dec RMS error 0.84 arcsec.
Personal Notes:
Compared with my last session with this setup - I was pleased to see that the IDAS P3 LPS filter was much better than the D2 filter - subs showed less background light pollution and the horrible star haloes have gone!
The trailed stars produced by differential flexure in my guidescope have also disappeared - just tightened all the guidescope connections.
Messier 88 and 91 - Spiral Galaxies in Coma Berenices
Two spiral galaxies from the Messier catalogue lying in Coma Berenices. Imaged over 2 nights which is a rarity for me in cloudy Northern Ireland.
Messier 88 lies top right and is a classic spiral galaxy. It measures 6.9 x 3.7 arcminutes. A supernova was detected there in 1999.
Messier 91 lies bottom left, it is a barred spiral galaxy and is classified as "anaemic" - see below! It measures 5.4 x 4.3 arcminutes.
Both galaxies lie in the Virgo galactic cluster which comprises many thousands of galaxies moving at speed under the influence of local gravity. Eventually, they will all collide at the local centre of gravity.
Tenuous hot gases and dust lie inbetween the galaxies forming a hot intracluster medium. As the galaxies race through the resistance of the medium, ram pressure stripping shears their own gas away and leaves them increasingly incapable of forming young new blue stars.
Messier 91 shows this effect more than M88 - it is pale and yellowish for a spiral galaxy - hence anaemic!
Some interesting small galaxies are seen in the field including on the mid right border, a small irregular spiral galaxy - IC 3476 which appears disrupted - probably by approaching too close to a larger galaxy in the past.
Technical Card:
900/120mm f/7.5 Equinox ED doublet refractor.
Skywatcher x 0.85 FR with 2 inch IDAS LPS P3 filter
MoonLite electronic focuser
Astro-modified Canon 80D at ISO400; 26 x 10 minute subs
QHY PoleMaster for polar alignment.
NEQ6 pro mount with Rowan belt drives -2 star align.
Camera control with Backyard EOS
Post processed in PixInsight 1.8.8
60 Flats EL panel: 1/40s @ ISO400
Master Dark from Dark Library, 50 x ISO and Temp. matched.
Master Bias from Library, 03/2021
Camera sensor temperature (external battery): 12-14c
Local parameters:
Temp: 7.0 - 9.2c
Humidity: 55.4%
Pressure: 1010 hPa
Light Pollution and Weather:
SQM (L) at end of session night 1 (0110 hrs UT) =20.33 mag/arcsec2. Clear both nights throughout - no subs lost due to weather.
Astrometry:
Center (RA): 12h 33m 40.785s
Center (Dec): +14° 24' 26.77"
Size: 1d 01m 58.9s x 50m 35.3s
Image scale: 0.977 arcsec/pixel
Focal distance: 792.08mm
Pixel Size 3.75 microm
Polar Alignment:
QHY Polemaster alignment -
Error measured by PHD2= 2 arc minute.
RA drift + 2.07 arcsec/min
Dec drift + 0.52 arcsec/min
Guiding:
PHD2 guiding with ZWO ASI290mm/PrimaLuce Lab 240/60mm guide scope. Every 3rd shot dithered.
RA RMS error 1.3 arcsec.
Dec RMS error 0.84 arcsec.
Personal Notes:
Compared with my last session with this setup - I was pleased to see that the IDAS P3 LPS filter was much better than the D2 filter - subs showed less background light pollution and the horrible star haloes have gone!
The trailed stars produced by differential flexure in my guidescope have also disappeared - just tightened all the guidescope connections.