Tag: jupiter

A Multiplicity of Moon Images

It’s been a splendid couple of weeks for moon pics. And unusually for my part of the world, there’s even be a few clear skies.

I’ll start off with the phases of the moon, beginning with first quarter on 6 Jan, all the way through to the full moon on 13 Jan. There were still a couple of cloudy nights, so it isn’t a complete record. I also haven’t got the scale and illumination quite right, so don’t pay too much attention to that. The first two photos on the top left are from consecutive nights and give a good, clear indication of how much the phase changes in a single day. These were all taken with my main 6″ telescope and the Panasonic Lumix GF7 camera.

The moon’s been doing a regular tour of the night sky, starting on 4th Jan by visiting Venus. Sadly, I didn’t get a picture of this one, so you’ll have to rely on the BBC for that.

https://www.bbc.co.uk/news/articles/c3rqe2ndl0lo

On the 9 Jan it was the turn of the Pleiades star cluster, better known as the Seven Sisters, to receive a visit from the moon.

The photo above is really a composite of two photos taken a few seconds apart with very different exposures. The moon is much, much brighter than the brightest stars. A single image tends to either grossly over expose the moon, or make the stars invisible. Here’s what a single exposure from a few minutes later looked like.

Both the above images taken with the GF7 and a Carl Zeiss 135mm lens.

Next up on the grand tour was Jupiter. Once again, I needed to combine two separate images. Even Jupiter is no match for the brightness of the moon.

The inset on this image is a crop of Jupiter from the same photo, showing a close up of some of the Galilean moons. GF7 + Carl Zeiss again.

Finally, on the morning of 14 Jan, there was a lunar occultation of Mars, where the planet passed behind the moon. This wasn’t fully visible in the UK. Here, the moon just edged closer and closer to Mars, but never actually obscured it. For an excellent description of why occultations are important, especially when it’s a full moon, see this post by Matt Strassler.

Tonight! Mars Meets the Moon (and Ducks Behind It)

I was in my back garden until about 3.30 am. The closest approach wasn’t until about 4.30, but I was just getting too cold and too tired to wait up longer. So this was one of the final pictures that I took.

Taken with my 6″ scope and the GF7. It’s been cropped and I’ve slightly increased the brightness and colour saturation of Mars, but otherwise it’s a single image from the camera. I was reasonably chuffed with this. Then I saw this totally amazing image on Astronomy Picture of the Day.

https://apod.nasa.gov/apod/ap250115.html

Oh well, keep practising!

Jupiter Problems

I normally stack lots of short exposures. Due to the limitations of my telescope, I need to spend a lot of time re-centering whatever I’m taking pictures of. This is OK for star clusters or galaxies or nebulae. I can spend hours collecting as many frames as I like. These objects barely change over a period of hundreds of years. So I did the same with Jupiter.

This picture was taken on 21 Dec at about 2 am. It’s a stack of about ten frames. It’s OK, but I thought I could improve it by stacking more exposures. But it seemed that the more frames I tried to stack, the worse the result became. What’s going wrong?

It took me ages to figure out the reason: Jupiter has changed! It may seem obvious, but the planet Jupiter rotates. In fact it rotates fast. Despite being large enough to swallow 1,000 earths, it’s day only lasts 10 hours.

This adds another complication when you’re trying to photograph it. For a planet that’s rotating fast it means I don’t have much time. Here’s the same picture on the right. This time contrasted with another, taken 20 mins earlier.

The planet does a full rotation of 360 degrees in 10 hours.
36 degrees in an hour.
12 degrees in 20 mins. 12 degrees is a huge amount.

Even in these low resolution, blurry images you can see that cloud features have moved significantly in 20 mins. Here’s the same comparison again. This time there’s a yellow rectangle highlighting a small collection of three greyish clouds against a brown background. The same three clouds are visible on the right hand image too but have clearly moved.

If only the planet would just stay still while I photograph it!