M 74

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Date
2017/11/12

Observation place
My permanent observatory in Longueuil
in white light pollution zone

Technical

TelescopeCelestron Edge HD - Diamè. 203mm (8 ''), focal length 2032mm, f / 10
Focal reducerf / 6.3 (63%)
MountCelestron CGEM
Imaging cameraAtik 383 L + monochrome regulated at -20o Celsius
Autoguiding cameraZWO ASI 120MM with one optical splitter
Auto Guidance Accuracy (RMS)2,04 '' of arc (4,08 '' of arc in total)
Image typeL (RVsB)
Vs: synthetic green image
ExhibitionLuminance (50 x 1 'bin 2 × 2), Red (30 x 2' Bin 2 × 2) and blue (29 x 2 'Bin 2 × 2)
Image acquisition softwareMaxim DL
Guidance softwarePHD Guiding 2
PretreatmentMaxim DL
TreatmentPhotoshop and PixInsight
Traitements spécifiquesCreate a synthetic green layer

Object description

Object typeSpiral galaxy front view
ConstellationFish
Visual magnitude9,8
Surface gloss (mag / arcmin2)14,2
Distance29,4 million light years
Diameter 84800 light years
Dimension seen from Earth10,5x 9,5 arcmin 
M74 is a face-on spiral galaxy in the constellation Pisces. It has a mass equivalent to one-fifth of our galaxy. It is 24,4 million light years away from our earth. Its diameter is about 84800 light years. The spiral arms of the galaxy contain many young and still forming stars. The galaxy contains about 100 billion stars. Three supernovae have been observed in M74: SN 2002ap, SN 2003gd, and SN 2013ej.  

In visual observation, it is difficult to find M74 if there is any light pollution or if the weather conditions are not perfect, because of its almost stellar core (visually looks like a star) and the very low brightness of the spiral arms. Its visual magnitude of 9,8 makes it invisible to the naked eye as well as to binoculars. A refracting telescope allows you to see only the core of the galaxy and so, it should not be confused with a star. To hope to discern the spiral structure of the galaxy, a 250 mm instrument is necessary and it must be observed in a site of very low light pollution.  

In my site of extreme light pollution (white area), I managed to define very well the two main spiral arms of the galaxy as well as the weak nebulosities which surround them. It was a challenge for me to be able to resolve this faint galaxy in my sky of significant light pollution.  

To successfully solve this galaxy, I did not use a light pollution filter. Instead, I chose to take a lot of short exposure photos in order to benefit from the increase in the signal-to-noise ratio according to the following formula: Increase in the S / N ratio = √ number of images. Also, the exposure time per photo chosen was determined so as not to overexpose the sky background of my site of significant light pollution (white area).  
Richard Beauregard
Sky Astro - CCD
My impression "We cannot be alone in this gigantic universe"