Sunday, August 6, 2023

Saturn With Five Moons

The Unistellar telescopes are not exactly known for being great telescopes for imaging planets. But that's okay, as they deliver much better images of deep sky objects. But there are times when you want to look at the planets. Thankfully, last fall they implemented a software update that greatly improves planetary imaging for Venus, Mars, Jupiter & Saturn (see my post A Harvest of Planets for more). 

Last night I used my eVscope to look at Saturn:

The view isn't quite the same as what you get in a traditional telescope. When you look through a normal telescope you can see Saturn, its rings and its brightest moons too. But here the view is optimized to show just the planet, so the moons sort of drop out of view. 

If instead you point the telescope at Saturn's brightest moon, Titan, then the view is completely different. 

The optimization used for planets is no longer in place and you can use Enhanced Vision to see farinter objects. I intentionally didn't center things here, but the big bright thing is Saturn, which is completely over exposed. Also visible are many stars and some of Saturn's gazillion moons. How do you tell the moons from the stars? Consulting an app like SkySafari helps, but a surefire way to find them is to photograph them again to see what moves. 

The animated gif below is cropped a bit from the image above. It was made from two images taken 22 minutes apart that were then aligned on the stars. Everything that is moving is part of the Saturn system.


I've got an annotated version below, but can you spot all five of them? Two of them are close to the glare of Saturn itself. Titan is just to the upper right of Saturn and Rhea is in the seven o'clock position, looking here like it is touching Saturn. Along that same line (Titan-Saturn-Rhea), but much fainter and further out is Hyperion. It is basically in the middle of the image. Extend that line further and you come to the much brighter Iapetus. The left of Iapetus is a star of similar brightness and a much brighter star below that. In between those two stars is faint Phoebe. SkySafari plots Phoebe in the wrong location but lists its magnitude at 16.8. 

Finding Phoebe was my main goal here. The best time to catch it is when Saturn is closest to Earth, which it will be later this month. Phoebe is a small (132 miles across) irregular moon in that it isn't completely round. It is far enough from Saturn (8 million miles!) that it takes 550 days (one and a half years!) to make a full orbit around Saturn. 

Here's the annotated version of Saturn and its moons. It's full sized so that you can actually spot Phoebe:

I am happy to have tracked down another faint moon of the outer Solar System.