The eos M is a very good apn for astrophotography. Light, good sensor, but without intervalometre...
But with magic lantern (and without the low cut filter... ^^ ) you can do this :
I don't know the english name, but this is Orion, 2h20m, with the CLS filter, 50mm f1.4 at f4.
full here : http://www.webastro.net/upload/images/26132-1456930987.jpg
Le coeur & l'âme et le double amas de Persée !
With the CLS, and 1h40m, 105mm f2.8 Sigma @ f4 !http://www.webastro.net/upload/images/26132-1459955030.jpg
The full pictures are an binnig x2 from the sensor resolution, so the picture size is 4,5 mpx.
It may be a good idea to make it natively with ML !