Arp 117 (IC 983 & 982) & Arp 79 (April 2018)

I've always been fascinated by these galaxies.  They are out of my league for "pretty picture" imaging because my skies are not the best.  I think the dimmest spiral arm of IC983, the huge spiral galaxy on the left, is almost dimmer than my local skyglow.  Still, a guy can observe.

The thing is, these galaxies are amazing.  IC 983 and the smaller spiral IC 982 appear to me to be interacting.  Two of IC 983's spiral arms appear bent toward the smaller spiral.  In a way, these remind me of M51 and NGC 5195, which is Arp 85.  But whereas M51 is small, perhaps 50,000 light years across, IC 983 is huge, perhaps 400,000 light years across!  M51 is a mere 25 million light years away, but IC 983 is ten times further—254,000,000 light years away! Yet IC 983 still dominates the view in this image (taken with the exact same setup used to image M51 earlier this year; you can see how massive IC 983 must be!).

One thing that always intrigued me about IC 983 and Arp 79, the small spiral on the right, was that in most images I have seen, their spiral arms are bent at seemingly impossible, nearly 90-degree angles.  This seemed odd to me; how could gravity cause that?  Yet in my fairly deep and detailed image (equal to the most detailed images I've seen of these galaxies), the spiral arms of both galaxies look pretty normal, their angles normally curved.  I've decided that prior images suffer from lack of depth or over-processing.  I am happy to see this mystery ended.

This image is 28x720", taken over three nights (because these galaxies set behind a tree after three hours).  The camera was the SXVF-H9, and the scope was the CFF 290 Classical Cassegrain at f/8.1.

The best color images I've seen of this set are here and here.  The second of these is quite detailed.  Both are worth a look.