M81, M82 and the IFN

[sharkmelley]

This image of M81, M82 and the Integrated Flux Nebulosity is an integration of 480 x 30sec exposures i.e. 4 hours in total.  It was taken over 3 nights (23/24/25 May 2017) at Astrofarm in France.

This is a slight re-process of an image I have already posted on the Deep Sky Imaging section of SGL.

Technical details:  H-alpha modified Sony A7S on Takahashi Epsilon 180ED.  480 x 30sec dithered exposures (4 hours total integration time) at ISO 10000.  Stacked in PixInsight with darks, flats and bias followed by DBE and Arcsinh stretching. Residual gradients removed in Photoshop CC.

Larger version can be found here:  http://www.markshelley.co.uk/Astronomy/2017/M81M82IFN_20170525_v2.jpg

Mark

[Davey-T]

Lovely image Mark, have you tried the same thing from home just to see the difference ?

Another project abandoned until next year here.

Dave

[sharkmelley]

12 hours ago, Davey-T said:

Lovely image Mark, have you tried the same thing from home just to see the difference ?

 

Thanks.  Yes I have tried it from home but the result was quite noisy.  I would have needed twice the total integration time to do it any justice.  The difference is totally due to the sky darkness.  At home I typically get an SQM reading of 20.9 mags/arcsec^2 but at AstroFarm it was pretty close to 21.6

Mark

[Davey-T]

More like 15 round here, I took some 30 min subs of M81/M82 this year using QSI683 and W110FLT and there wasn't a whiff of any IFN

Dave

[sharkmelley]

8 hours ago, Davey-T said:

More like 15 round here, I took some 30 min subs of M81/M82 this year using QSI683 and W110FLT and there wasn't a whiff of any IFN

I'm not surprised you saw no IFN - it was difficult enough with my fast scope and a dark site.  Here is a single 30second sub from that imaging run:

It has been software binned by a factor of 5, stretched and noise reduction applied.  Ignore the background gradients and there is just a hint of the IFN near the bottom, left of centre.  Elsewhere it is completely buried in noise (the noise is dominated by skyfog).    That's why I needed hundreds of subs.

Mark