Cloudy this evening, but here's my shot of Comet C/2023 A3 (Tsuchinshan-ATLAS) last night βοΈ
It's a 9 min stack of 5 sec images with my DSLR+85mm lens on a tripod, unguided, so the stars are slightly trailed π€·ββοΈ
I've removed a gradient due to light pollution over Mannheim, but there some residuals as I've kept the sky bright to trace the tail extending 10ΒΊ towards Ξ² Oph & the IC4665 cluster at top-left & see the faint anti-tail below π
Also worth noting that I didn't do any dark or bias removal or flat-fielding, which probably also makes for some of the background funkiness in the image. I did take darks, but ... π€·ββοΈ
I used Siril to make the stack & while it works well, I couldn't find a good way of getting it to pick & use alignment stars across the full sequence of images, as I wasn't tracking.
I took a total of around 300 images in two sequences, but there are only 108 combined here.
And for those with a perhaps a scientific interest in young stellar clusters like IC4665, here's a paper from almost 20 years ago that I was on looking at the low-mass end of its mass function.
This work was done in the context of an EU-funded collaborative network called CONSTELLATION involving many star formation groups across Europe and which I led while working at the University of Exeter.
Simpler times, although it didn't feel like it then π€·ββοΈ
https://www.aanda.org/articles/aa/abs/2006/10/aa4102-05/aa4102-05.html
We present the combined results of three photometric monitoring campaigns targeting very low mass (VLM) stars and brown dwarfs in the young open cluster IC4665 (age ~40 Myr). In all three runs, we observe ~100 cluster members, allowing us for the first time to put limits on the evolution of spots and magnetic activity in fully convective objects on timescales of a few years. For 20 objects covering masses from 0.05 to 0.5 Msol we detect a periodic flux modulation, indicating the presence of magnetic spots co-rotating with the objects. The detection rate of photometric periods (~20%) is significantly lower than in solar-mass stars at the same age, which points to a mass dependence in the spot properties. With two exceptions, none of the objects exhibit variability and thus spot activity in more than one season. This is contrary to what is seen in solar-mass stars and indicates that spot configurations capable of producing photometric modulations occur relatively rarely and are transient in VLM objects. The rotation periods derived in this paper range from 3 to 30h, arguing for a lack of slow rotators among VLM objects. The periods fit into a rotational evolution scenario with pre-main sequence contraction and moderate (40-50%) angular momentum losses due to wind braking. By combining our findings with literature results, we identify two regimes of rotational and magnetic properties, called C- and I-sequence. Main properties on the C-sequence are fast rotation, weak wind braking, Halpha emission, and saturated activity levels, while the I-sequence is characterised by slow rotation, strong wind braking, no Halpha emission, and linear activity-rotation relationship. Rotation rate and stellar mass are the primary parameters that determine in which regime an object is found. (abridged)
Mark McCaughrean
Aleks Scholz
Dunc
Derick Rethans