Arp242, The Mice Galaxies

[tomato]

Having spent what seems like half of this galaxy season trying to do justice to the mighty M101, (I blame @ONIKKINEN, he shouldn't have posted such a fantastic 25 hr image!😄), I have returned to my original list of small but interesting galaxy targets. This is 7.37 hrs on NGC 4676 A&B an interacting pair catalogued as Arp 242 in Coma Berenices. The long, narrow tidal tails have given this pair the very descriptive popular name of the Mice galaxies. Integration was divided equally between L and OSC RGB on the Esprit150/QHY268 dual rig. For some reason, my usual PI workflow would not work at all, I simply could not get any colour in the galaxies. However I noticed that this was not the case with the auto stretched image in APP after channel combination, cropping and star colour calibration, the colour looked OK so I have worked on this in it's non linear state instead. As is usual for this region of sky, there are lots of tiny, more distant galaxies to be found in the image.

Thanks for looking.

[ONIKKINEN]

Not seen this one before, nice shot. Some Ha is visible in the tidal tail of the right galaxy, probably due to the messy collision. Star formation rate must be very high in these two at the moment.

Do you use Asinh stretches in PI? Its kind of a cheat code for colour processing. Otherwise i find it hard to get colour out in PI.

[tomato]

Thanks for the feedback, I have not tried the Asinh stretch in PI, I confess I don't tend to stray off my PI well trodden track too much, and I really should. Is that the tool you used to stretch your M101 data? I'm still playing around with my 30 hr dataset, I've took some improved flat frames but I'm really struggling to get any Ha highlights back with the recalibrated data.

With regard to Arp 242, this system has apparently been used a lot in recent years for galaxy interaction simulations, owing to the fact that the two galaxies are of similar masses, and that the spiral planes of the galaxies are perpendicular to each other, makes for simpler calculations I suppose.

[ONIKKINEN]

I usually start stretching with Asinh at a value of 1000 + some blackpoint adjustment. Not every image takes the full thousand well, in which case i use something like 300-500 but i do always use Asinh stretches at first. Its not a panaceum and often inverts bright starcores which might require some work in Photoshop later, but usually its only a handful of stars so not a deal breaker.

[tomato]

I've just given Asinh a quick go on this data, and it has worked well on the colour. I'll try it out on M101, after I have had a break from the monitor screen.

[WolfieGlos]

Interesting target, not come across this one before. Nice image too 🙂 I guess the tails are fairly bright if they've come out so well with the short time?

That trick of Asinh to 1000 @ONIKKINEN told me about too, on a post a while back now (might have been M33?), and I still use it to this day. Often dialed back from 1000, but I always use it as a start point.

[ollypenrice]

Very good. These interactions are fascinating to see.

Olly