A supernova remnant - SH2-91

Apart from the well know Veil Nebula or Cygnus Loop, the constellation Cygnus hosts another supernova remnant called G 65.3+5.7. With a distance of about 25.000 lightyears it is way further away and much fainter. And much, much larger.

The image of SH2-91 resembles about a quarter of that object.

To image the fainter regions and obtain smooth gradients quite much integration time is required.

After trying to capture this object with my ZWO filters, I could not obtain the intended results from my location. Main reason probably is the lesser optical density outside the filter's passband, so too much sky background reaches the sensor.

After switching to Antlia 3nm narrowband filters even the faintest regions rendered pretty nice, even the fast telescope normally would require pre-shifted filters for perfect operation.

The following crops demonstrate the difference between both filters pretty clear. Both images contain the same integration time and were processed identically: