In addition to focussing, the tri-Bahtinov also indicates collimation status along three axis. You could basically do the same by turning your classic Bahtinov at 120° angles and check focus each time.
This is a famous sight: Messier 51, also known as the Whirlpool Galaxy (not hard to see why!) in the Hounting Dogs constellation (Canes Venatici).
I remember being able first time ever to see this galaxy with 8×40 binoculars when I was 14. That was a major achievement back then. We spent the night under the stars in April with three friends, and as the spring sky is not very rewarding to binocular users, at least this one made our hearts beat faster.
In this picture, images from last year in April are combined with images from February 15th, 2018. All are taken with the C11, Nikon D750 and now in February with the ASI174MM as a guiding camera, replacing the Lacerta MGEN for off-axis guiding work.
The ASI174MM has delivered every time since it’s purchase in January a decent guiding star. With PHD combined with BackYardNikon the guiding goes excellent.