SuperNova in NGC 6946
30th September 2004 21:00UT
SC1.5 Toucam + 200mm F5 Newtonian.

A recently reported supernova in NGC 6946 has caught the attention of QCUIAG. I think this is mainly due to the nice positioning of this supernova - at the zenith just as it gets dark!

First, here is an image of NGC 6946 I took last month. This was 80 stacked frames of 50s exposure at 650mm focal length. The galaxy has a Surface brightness: 14.0 mag/sq arcmin and is right on the edge of my equipment limit.

Then I imaged the supernova with 10s exposures and gathered 50 frames. These I stacked in registax and used curves lightly in photoshop. The supernova is marked. The image is roughly the bottom left quadrant of the above image.

Then I took 180 frames of 25 seconds exposure and stacked them with a dark frame. I then saved from registax as a FIT and loaded the red channel FIT into Teleauto and used a reference image to estimate the magnitude.

Next day (2004-10-01) 75 stacked frames of 25 seconds exposure. No change in magnitude.

I also attempted my first spectrum of this object. However, I have changed my grating-ccd distance recently, and have not calibrated it properly in a bright star. I tried to calibrate it on another star image in the FOV, but I am not convinced. Tomorrow I may try this again. I would expect an Ha emission line around 6562.

2004-10-02 No change.

2004-10-04 No change.

2004-10-05 Little change.

2004-10-06 Little change.

2004-10-07 Little change.

2004-10-16 Little change. 21:00UT

2004-10-18 Slight dimming? 21:10UT

2004-10-26 Slight dimming. 21:05UT No IR Filter

2004-10-28 22:00UT On 26th I made a measurement without using my IRB filter. All my other images are with IRB filter. I found on the 26th SN2004et had dropped 0.3 magnitudes. Was this due to the supernova dimming or because of the difference in filters? Tonight I tried both. Left image is without IRB filter, right image is with IRB. Quite a bit of wind tonight limited frames. This experiment is hardly conclusive as the IRB image is of poor quality. However, from these two images we get a magnitude of 12.76+-0.1 with the IRB and 12.99+-0.1 without the IRB. It seems quite likely that the IRB makes some difference. This is probably due to me using the Red FITS file for the measurement, and this would be most effected by the comparism stars having differing brightnesses in the IR region.

2004-10-29 22:50UT No change

2004-10-30 20:50UT No change

2004-11-09 20:30UT Several days later, No change. With IRB.

Finally, here is theimage in full colour. I have pushed the processing to show the host galaxy.

This estimate is in good agreement with other QCUIAGers. Hopefully I will get some follow up images in the next few days. Further information with other images can be found here.

Location: Curdridge, Southampton, UK. 51N 15W.
Details of equipment and method.

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