Tag: astrophotography

No Pretty Picture Today

Normally on a Saturday, I’d have a pretty picture of a nebula, or a galaxy, or a star cluster to show you. But there hasn’t been a clear sky all week, so I have nothing new to post. On the plus side, my rain barrels, that had run dry for the first time in 18 years, are now full and ready to water the plants again.

I have been looking to do a bit more than take pretty pictures though, and have been tentatively embarking on a couple of astronomical projects. The first one is my first look at variable stars. This is one area where amateur astronomers can make a real contribution to science. There are lots of reasons why some stars vary in brightness. Some are intrinsically variable because of their composition. Others are binary objects where the main star gets eclipsed. Others undergo periodic explosions, like T Cor Bor, that I’ve been observing for well over a year now.

The world’s big telescopes are too precious a resource to spend their time monitoring all the variable stars in the sky. This is where amateurs come in. The American Association of Variable Star Observers allows amateurs to collect and upload their observations of variable stars. Providing a long term database of millions of observations.

https://www.aavso.org/

Naturally, all these observations must be standardised and of the same high quality. I’m still a beginner at this. The technical lingo that surrounds the subject is all a bit baffling to me at the moment. However, I’m hoping that my smart scope will come in handy here.

Seestar S50 All-in-One Smart Telescope

This magic box, about the same size and weight as a bag of sugar, contains a high quality lens, a camera, a computerised mount, various filters, a built in computer, and a phone based app that you can operate from any internet connection. Before this I used to spend about half an hour just trying to find T Cor Bor. Now, I can go to it instantly. As well as producing nice pictures, it records the time, date, geographical location and celestial coordinates of the object being photographed. They should be ideal for variable star observation. There are even people who who set it up and tell it to take automated pictures every ten minutes of things like T Cor Bor, so that professional astronomers can be informed as soon as it goes bang.

As well as T Cor Bor, I’ve had my first glimpse of SS Cyg. My pic on the right, a couple from AAVSO on the left.

This is a cataclysmic variable, like T Cor Bor. A red dwarf star is feeding a nearby white dwarf. And they really are nearby, separated by less than half the distance between the earth and the moon. But whereas T Cor Bor goes off every 80 years, SS Cyg goes off every couple of months. They would be an absolutely spectacular sight to see close up. Although you wouldn’t want to be anywhere nearby when it ignites.

The Seestar S50 brings me on to the the other project that I’ve been exploring this week. While the S50 is an amazing box, it’s not perfect. It only has a two inch objective lens. My “big” telescope has a six inch lens, with nearly ten times the light collecting power.

https://www.firstlightoptics.com/telescopes-in-stock/sky-watcher-heritage-150p-flextube-virtuoso-gti.html

The S50 works so well because it is a tightly integrated system. But this is also a disadvantage. It’s completely enclosed, with no options to change focal length, camera or mount. If you want to try something different then you have to discard the whole box and start with a completely new setup. There are better alternatives, but just look at the price.

https://www.firstlightoptics.com/telescopes-in-stock/celestron-origin-intelligent-home-observatory.html

So I’ve been exploring the possibility of adding the same automation capabilities to my existing SkyWatcher six inch scope. I think it can be done. A lot of the software that powers these smart scopes is based on existing open source software. I’ve been looking at one of the options available on Linux, a package called KStars.

https://kstars.kde.org/

This might look like just another planetarium package, but it’s so much more. It has the built in ability to control almost anything that’s astronomy related: telescopes, cameras, filter wheels, focusers, camera rotaters, domes. It can control them locally, or remotely. The catch is, in order to be able to control every manufacturer’s equipment, it has to be very flexible. And in order to be flexible, that makes it complicated. It’s one of those bits of software where you open a dialog and there are ten tabs. Each tab has dozens of controls with obscure sounding names or initials. And I don’t know what most of them mean.

So far I’ve got it to talk to the telescope and point it where I want it to go. I’ve got it to talk to a cheap astronomical camera that I bought. Although it’s not quite taking pictures they way I’d like. If I get this working properly then I should be able to get the big scope to do what the smart scope does. The way it works is this.

The smart scope uses a mixture of GPS and a built in compass to point to roughly the right part of the sky that you want to image. It then takes a picture. It compares the picture to its database of stars and figures out where the scope is really pointing and then moves the scope in the direction needed to get closer to the target. It repeats this over and over until the target is dead center. The technique is called “plate solving”.

When everything is setup correctly, KStars should be able to do this for my big scope. And that should make my life a whole lot easier for finding targets and performing long exposures.

I should be able to get higher resolution images, using my existing gear and at almost no cost. What’s more, I won’t be tied to any particular system or manufacturer. If I want to upgrade the camera, or mount, or telescope, or if I want to add a separate guide scope or focuser, or filter wheel, I can do it one piece of equipment at a time. But it looks like it’s going to require a bit of perseverance and patience. Watch this space…

Andromeda

This iconic island of 1 trillion stars, 2 million light years away, is simply gorgeous.

When I first bought my Seestar S50 smart telescope, I took a quick picture of the core of the Andromeda galaxy, and then forgot all about it as it largely disappears during Spring. Now that’s it’s popping back up again, I thought it was time to revisit.

There are a couple of challenges to photographing this with the S50. Not least of which is that it’s too big to fit in the S50’s field of view. You have to take several images of different parts and then patch them together.

I haven’t put a lot of effort into matching colours and orientation, so you can probably see the lines where the images overlap.

But this leads to the second problem. There are only about two hours of darkness this time of year. Each image takes about half an hour. With the inevitable overheads of setting up and checking that everything is OK, I just ran out of time before the first hint of dawn started to spoil the view. Which is why there’s a big black empty bit in the bottom left. In a few months time, Andromeda will be overhead for most of the night. All I need is one, long, moon free, cloud free, wind free, neighbours party free, night, and I’m hoping to get something much better.

The s50 has it’s own “mosaic mode”, where you can tell it to do it’s own patching of multiple images. It just about manages to do this in two hours over Andromeda.

Which isn’t bad, but I prefer my manual one. The automated one gives equal exposure to the whole image, whereas I can given more time to the fainter outer spiral arms.

Andromeda is quite easy to find at the moment.

Look northeast at midnight and find the “W” of Cassiopeia. Follow the right hand “V” down to a line of bright stars that form the Andromeda constellation. Where you hit Andromeda, there are three stars going up at a right angle. The Andromeda Galaxy is right at the top of those three. If you’re lucky enough to have a dark sky, then you might see something like this.

I need to use a camera to see this. This is a five minute exposure, iso 3200, f2.8, using a 35mm lens on a Panasonic GF7. If you are lucky enough to be able to see it, then I would love to see some photos.

Have you Seen the Eagle Nebula?

It’s kind of a rhetorical question, since most people reading this almost certainly have seen the Eagle Nebula, also known as M16 (number 16 on Charles Messier’s list of things that aren’t interesting because they aren’t comets). It’s just that it probably wasn’t called that when you saw it.

First of all, some directions for finding it. If you look due south at about 2am you should see an unmistakable triad of stars that span most of the southern sky. These are the three bright stars Vega, Deneb and Altair, often referred to as the “Summer Triangle”. The Eagle Nebula can be found southwest of the lower star, Altair.

The nebula lies about 7,000 light years away. But as always, unless you have exceptionally dark skies and a large telescope, you’re unlikely to see very much. Point a camera at it and take a couple of hours exposure and you get this.

The “Eagle” refers to the dark silhouette at the centre. But that still might not look familiar. If I zoom in and crop then you should get a better clue where you’ve seen it before.

And if that still doesn’t ring any bells then it’s time to see it as Hubble sees it.

Yes, the justly famous “Pillars of Creation” form a small part of the Eagle Nebula. You can see more of these iconic images on NASA’s website.

https://science.nasa.gov/mission/hubble/science/explore-the-night-sky/hubble-messier-catalog/messier-16/

Three degrees to the southeast of the Eagle Nebula, you can find the Swan Nebula, M17. I’ve been collecting a regular zoo this week.

Personally, I struggle to see a swan anywhere in this. I think the bright patch is meant to be one of the wings with the neck starting on the left and curving up to the right. But I’m not at all sure about that. Maybe you’ll have better luck?

More images on the Sky at Night web page.

https://www.skyatnightmagazine.com/astrophotography/nebulae/the-omega-nebula

And if you’ve read through all of that, or even if you haven’t, a very Happy Summer Solstice to you all!

The Dumbbell Nebula and Markarian’s Chain

M27, the Dumbbell Nebula, has made regular appearances on this blog. It’s a large “planetary nebula” blown off from the surface of a dead star, which now lies as a white dwarf at its centre.

https://www.skyatnightmagazine.com/space-science/planetary-nebula

White dwarf’s themselves are fascinating objects. They have a mass similar to our sun, but compacted down to something the size of planet earth. They no longer generate energy and are in the process of cooling down. Eventually, they will become black dwarfs: dense, burnt out cinders. But since the time taken for a white dwarf to cool is calculated to be longer than the current age of the universe, no black dwarfs are currently expected to exist.

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

My previous best effort for the dumbell was limited by the use of a manual telescope and camera. The colours here are false.

The other night, for the first time, I pointed the smart telescope at it. I took two, 5 minute, stacked exposures. One with the telescope’s light pollution filter (which makes the nebula brighter) and one with it’s infra-red and ultraviolet filter (which shows more stars). The result is a combination of the two.

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

At about 1,000 light years distance, The Dumbbell Nebula is on our cosmic doorstep. This was a rather pretty distraction from the real effort this week though. That was Markarian’s Chain, a long string of galaxies about 50 million light years away. They’re named after the Armenian astronomer Benjamin Markarian, who demonstrated that they were all part of the same group, moving through space together.

This is too large an object to fit in most telescope and camera combinations. It takes multiple images, patched together as a mosaic to build the whole picture. Fortunately, the smart telescope knows exactly how to do this. The following image took it four hours to assemble fully. This took several attempts, but I’m fairly happy with the result.

https://en.wikipedia.org/wiki/Markarian%27s_Chain

I really recommend the full size version of this, seen on a big screen rather than a phone.

https://mega.nz/file/B9oxySBJ#bRNB8hOzvV-D8jSefOKfzTDKx-UQukrSghr6jZ1gxyc

I’m hoping to do even better some time soon. I’ve been experimenting with putting the smart scope on an “equatorial mount”. This allows it to track the apparent rotation of the sky by having a fixed axis that points at the north celestial pole. Initial efforts look good, but I need some clear, moon free, nights to really try it out properly. This would remove a lot of the rotation artifacts present in the above picture.

Tycho and the Terminator

The “terminator” in this case is not some sci-fi sounding robotic killer. Instead, it is the line that marks the sunlit from the dark part of the moon. As it moves across the moon’s surface each month it has a dramatic effect on what is visible.

Here, for example, is Tycho crater, taken on 11 April.

Tycho is the centre of the large “splash” in the middle of this photo. Large rays of ejected material, resulting from the impact that caused the crater, are clearly visible, extending over a thousand miles in all directions.

Yet when we look at the same crater a few days earlier, the scene is completely different.

Tycho is more to the left in this picture. The rays are much less pronounced, with some of them barely visible. Instead, the crater walls and central mount are much clearer. These two photos barely even look like the same moon.

As I’ve pointed out before, even over a single night, the terminator moves visibly across the moon’s surface. It is this constant interplay of light and shadow that makes photographing the moon so endlessly fascinating.

Moon Mini-Phases

You can read more about Tycho crater on Wikipedia.

https://en.wikipedia.org/wiki/Tycho_(lunar_crater)