Tag: space

Different Types of Photo

I’m still struggling to get my big old scope to reproduce some of the behaviour of my smart scope. I won’t bore you with the endless rounds of incompatible software versions, missing drivers, missing star catalogues, multiple connection issues etc. etc. etc. Suffice to say that, after several months of mostly trial and error, everything nearly works. I can control the telescope from inside the house. The computer can compare the stars the camera sees with the stars it ought to see and move the telescope accordingly – a technique called “plate solving”.

My big problem at the moment is that, once the telescope reaches its target it tends to wander off somewhere. The photos from this aren’t very good. This one, of the Dumbbell Nebula is about the best of a bad bunch. Notice that the stars have diffraction spikes on them because this was taken with a reflecting telescope rather than a refractor.

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

The smart scope, on the other hand, allows me to explore a wide variety of photographic techniques. This, for example is the Triangulum Galaxy. At 2.7m light years away, it’s part of the Local Group that include the Andromeda Galaxy and the Milky Way. It’s a bit smaller than those two and can fit in a single frame of the smart scope.

The interesting thing about this image is that it was taken over several nights, each with a couple of hours exposure. Astrophotography has its own image file format that stores things like the coordinates and orientation in the sky of the photograph. This allows the images over different nights to be much more easily combined with one another. Notice – no diffraction spikes this time.

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

This same storage format also makes it easier to build mosaics of nearby bits of the sky. This picture of the Seven Sisters is actually a composite of two nearby frames. The whole cluster won’t fit in the smart scope’s field of view. But that’s no problem. Just photograph one bit then move the scope a little bit and photograph the next bit. The storage of coordinates makes it easy for software to combine the two.

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

I would love to sit up all night watching images appear on the smart scope. Unfortunately I have to sleep sometime. And sometimes the best bit of the sky appears exactly when I want to go to bed. The smart scope comes to the rescue once again. I can tell the scope to wait until a given time, and then spend a specified period photographing a named object. You can even give it a whole list of things, times and exposures, then just go to bed and let it do all the work. This photograph of M15, the Great Globular Cluster in Pegasus, was taken using just this technique.

https://en.wikipedia.org/wiki/Messier_15

I’ve got a very long way to go before I can get my old scope to emulate all these techniques.

All of the above photos were taken this week from my garden in Southend. The first with a Skywatcher Heritage 150p (6 inch reflector) and a ZWO ASI485MC camera. The rest with a Seestar S50 smart scope (2 inch refractor)

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.

Would you like to look at a Black Hole?

Obviously you won’t see the Black Hole itself. A Black Hole is, well, black. It’s gravity is so intense that not even light can escape it. But I can point you to a couple of places where there almost certainly is a black hole.

Every large galaxy (probably) contains a supermassive black hole at its centre, including our own. So you just have to look at any galaxy in the sky and you’ll be looking at a black hole. Our own galaxy’s supermassive black hole is called Sagittarius A*. It has a mass over 4 million times the mass of the sun. If you’re familiar with the “Sagittarius Teapot” then it’s an easy find.

https://earthsky.org/favorite-star-patterns/teapot-of-sagittarius-points-to-galactic-center/
https://en.wikipedia.org/wiki/Sagittarius_A*

Unfortunately this is too low in the sky for me to see from my back garden. However, there are much closer black holes to earth, some of which are on our cosmic doorstep.

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

The one I’m going to point out was the first confirmed, stellar mass, black hole. Lying 7,000 lights years from earth, it’s very easy to find in the night sky, especially right now.

We begin with our friend, the Summer Triangle. The three vertices of the triangle are the stars Deneb, Vega and Altair. They all lie due south at midnight at the moment and dominate the summer sky in the UK. The Milky Way, if you’re lucky enough to be able to see it, runs along the line connecting Deneb and Altair.

Deneb is the brightest star in the constellation of Cygnus, the Swan. This constellation also goes by the name of the Northern Cross, for obvious reasons when you see the picture below. Here’s a picture of the Summer Triangle and Northern Cross, taken with my Panasonic GF7 and a wide angle lens.

Follow the cross down from Deneb to Sadr, the centre of the cross. Then keep going to Eta Cygni. This is the star we’re interested in.

In the 1960s, when they first sent rockets equipped with X-Ray scanners above the earth’s atmosphere, it quickly became apparent that there was a very strong X ray source somewhere in the constellation of Cygnus. This was labelled as “Cygnus X ray source number one”, Or Cygnus X-1 for short. As better and better satellites did more refined observations, the source was narrowed down to near Eta Cygni. The actual star where they seemed to originate was very nearby. The star doesn’t have a name, just a catalogue number, HD 226868.

HD 226868 is a very massive, very hot star, about 30 times the mass of the sun. However, it’s not that hot that it should be emitting the kind of X rays that are observed from it. Studies of the star’s spectrum revealed a wobble due to a hidden, equally massive, companion. This hidden companion lies about the same distance from the star as earth is from Venus’ orbit. Almost everyone agrees that this hidden companion is a Black Hole. Even long term sceptic, Stephen Hawking, eventually conceded the point. The solar wind from HD 226868 provides just enough material to feed this hidden companion and let it generate the X rays that we see above the earth’s atmosphere.

Here’s a picture of HD 226868 taken with my Seestar S50. The bright yellow star on the right is Eta Cygni. For scale, the distance between the two stars in this picture is about half a degree in the sky, the width of the full moon. That may sound like a lot, but the full moon isn’t nearly as big as many people think it is. It only spans about a tenth of the angular distance between Eta Cygni and Sadr at the centre of the Northern Cross.

So next time you’re looking up at the sky, see if you can find Eta Cygni. When you do, you’re looking almost directly at a Black Hole.

https://en.wikipedia.org/wiki/Cygnus_X-1

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!