Tag: space

Mare Crisium

The few clear nights recently have been dominated by a near full moon. You know what that means by now, more moon pics!

I’ve highlighted the Mare Crisium (“Sea of Crises” – who came up with these names?) on this full moon from the night of 15th Dec. It’s the dark patch on the top right of the red rectangle.

P1070719mareCrisiumRectSml

https://en.wikipedia.org/wiki/Mare_Crisium

I wouldn’t think close ups during a full moon would be that interesting. But a few days later, with the shadows beginning to grow on the surface, zooming in is a bit more fun. Here’s a close up of Mare Crisium from 17th Dec. I’ve tried to up the contrast a bit and bring out a bit of detail. Hopefully not too much. If you exaggerate the detail too much then the picture stops looking natural and it becomes very obvious that it’s been manipulated.

Fans of Star Trek: the Next Generation might be interested to know that one of the craters in Mare Crisium is named Picard. Not, it has to be said, after Jean Luc Picard, the captain of the Enterprise, but another Jean Picard, the 17th century French astronomer.

https://en.wikipedia.org/wiki/Jean_Picard

To give you a sense of scale. Picard crater is 23 km across. So about the size of a large town or city. The whole Mare Crisium is about 550 km across – roughly the size of England.

Three days later, on the morning of 20th Dec, Mare Crisium had disappeared into the shadows. The terminator between night and day had moved west. I’ve highlighted the area with the yellow rectangle.

The closeup from that night is centered on the large crater Theophilus between Mare Tranquillitatus to the north and Mare Nectaris to the south.

https://en.wikipedia.org/wiki/Theophilus_(crater)

None of these pictures are likely to win any prizes. But bear in mind they’re taken with a relatively cheap (by astronomy standards) 6″, entry level telescope, and a second hand mirrorless camera. Neither of which are designed for astrophotography. I’m still trying to see just how far I can push such modest equipment. I suspect the real limit is my location in the heavily light polluted Southend-on-Sea.

Any dark skies next week should be mostly moon free. So I have to start planning what to look at.

And if you managed to get this far, Happy Winter Solstice!

Jupiter

Jupiter is beautifully placed in the southern sky at midnight just now, with no moon to spoil the show. You might remember my previous effort to capture it was not a great success. Since then, I’ve picked up a new x2 magnifier for my scope. (Called a “Barlow” in telescope-speak.) I got it for £20 on Ebay, which I consider a bit of a bargain. I’ve no idea if it was responsible for any improvements. There are a myriad of factors that can affect a picture on any one night. But here are the old and the new compared, with the new picture on the right.

jup20Nov28nov

This isn’t what you actually see through the telescope. It’s heavily cropped. The original picture looks more like this. This is a 1/60s exposure at iso 1600.

I don’t normally save “raw” images on the camera. But that night I accidentally had that option switched on, and I’m glad I did. Just a reminder, most images on the web are jpeg type files, or similar. These are compressed images. But the compression algorithm is lossy, it doesn’t preserve all the original information. All the images you see above are based on jpeg originals.

This can work very well for every day pictures in bright light. However, for high magnifications, every bit of detail is important. Raw images save every bit that is captured by the camera. And what a difference it makes. Here they are compared, with the raw image on the right.

As you can see, there’s a lot more detail in the raw compared to the jpeg image. This feeds through the image processing. I took a dozen images in rapid succession and stacked them using my favourite photo processing program, called “Siril”. This is the result (raw on the right).

And here’s that final image close up.

Given the cheap equipment, and basic processing, I’m fairly chuffed with this.

Having said that, Jupiter is by far the easiest planet to photograph. More massive than all the other planets combined, and able to swallow 1,000 earths whole, it presents an easy profile to photograph in the night sky. Mars is tiny in comparison, Saturn is much further away, and Venus is just a featureless, cloudy blob. Initial attempts to photograph them haven’t been an outstanding success so far. I’ll let you know if my efforts improve.

Meanwhile, back in the Andromeda galaxy. No telescope this time, just an old Carl Zeiss lens I found in the cupboard, This was only a brief test, iso 3200 4s x28, so under2 mins total exposure. Based on the result, this might be worth playing with a bit more.

Some Photo Experiments

I’ve been trying out some different things over the last few weeks with my telescope and camera. Mostly I take photos by removing the eyepiece in the telescope and placing the camera there. This is called “Prime Focus” astrophotography. Even there I’ve been trying to push the boundaries a little bit.

Magnification is directly linked to the focal length of the telescope. This isn’t usually the main consideration in astronomy, where the size of the main lens or mirror is usually the principle characteristic. This is what controls its light gathering power and so determines the faintest objects it can see. My scope is relatively compact with quite a low magnification.

However, for planets and the moon, magnification is everything. You might have noticed that I’ve never posted any images of the planets and that’s the reason why. You need to add some extra optics to alter the focal length if you want to do planets with my scope. The result will never be as good as a dedicated instrument, but I can try. Here’s a single 1/200s iso 3200 shot of Jupiter.

jup20nov

That’s fairly typical of what you would actually see through the scope. I was hoping to get a few more over the last few nights, but weather, the moon, and me having to sleep sometime, have conspired to get in the way. To get improved results I need to take lots of images and stack them. This is most easily done by taking a movie. Here’s one of Saturn.

https://mega.nz/file/Ro4C3KTC#qwqi0L2sRXmHwE9wO8tH9om9PxEtq08ujE-g_jqB3DE

Unfortunately, my attempts to stack the frames from this haven’t worked out too well so far.

Increasing the focal length can also be used to get high magnification images of the moon.

This is the Mare Nectaris using this technique.

https://en.wikipedia.org/wiki/Mare_Nectaris

As well as increasing the focal length of the scope, I’ve also been experimenting with just using the camera directly. The problem I’ve always had with this in the past is that you need a really good tripod, with fine adjustments and preferably a motorised mount to track the sky. Expensive. Trying to take photos of the sky on an ordinary tripod has just proved too awkward.

However, I recently figured out a combination of lumps of metal, bolts and clamps that has allowed me to remove my telescope from its mount and put the camera directly in its place.

This has been great fun to use. It allows me to use the app on my phone to point the camera wherever I want and track it fairly accurately. It also lets me play with all the old lenses that are sitting in cupboards in the house. I’ve hardly begun to explore the possibilities here. At the moment I’m mainly using an old Pentax K mount f1.7 50mm lens. This has a field of view of about 15 degrees. perfect for Orion.

And Andromeda.

The way I’ve mounted the camera also allows me to balance it so that it isn’t front heavy. A big problem on a normal photographic tripod. This’ll let me play with some old telephoto lenses that are currently sitting unused. So I might be able to try out some new stuff in the months to come.

Comet Tsuchinshan–ATLAS

Last night, finally, I managed to get some pictures of the comet that’s being dominating the astronomy news for the last couple of months. Until now it’s always been below the horizon or behind clouds.

I struggled to find it at first even with binoculars. I was expecting a naked eye object, but in the end it took a camera to reveal it.

So here it is, looking west from my back garden in Southend at about 7.30 last night.

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This is a cropped and slightly enhanced version. The original looks more like this.

(The comet’s near the bottom in the middle of the picture.) 0.5s exposure at ISO 3200.

And through the telescope.

Again, this has been slightly enhanced. The original is a bit darker.

2s exposure, ISO 3200. These are single frames, so no stacking.

The comet should still be visible for a while, although I’m told it will fade rapidly. As you can see above, it’s already not that bright.