The Scruffy Astronomer

Sight, in humans, is quite a popular thing. People regard it highly, and do seem to think it's an overall good idea. My experience of sight has been, like most other people, a given. It started great, and as a kid my family would occasionally use me to find things, like shop signs, in the distance. Of course, it does deteriorate over time, and I've worn glasses since early university. It started just for reading, but soon I was wearing them full-time.  It turned out that apart from being long-sighted, I had astigmatisms which were reasonably severe, and getting worse.  You get old Eventually I wasn't able to look through telescopes any longer: unless I had an eyepiece that I couldn't afford, the eye relief - the required distance between the eyepiece and your eyeball - was so short that I had to remove my glasses. Without glasses, of course, all I could see were comets. No, they weren't meant to be there.  Resignedly, I gave up visual astronomy and went deeper into ...

We've uploaded another video onto the Optics Central YouTube channel. This one is me unboxing the saxon Astroseeker 15075. This is a 6-inch Newtonian on a light computerised alt-azimuth mount. The mount is a nifty little unit, well capable of carrying the weight of the tube. It's a heavier duty mount than the SkyWatcher mini AZGTi, and is capable of taking a heavier tube than the Newtonian here. In fact, this mount is often found with a 127mm Maksutov. The mount can be controlled by the hand controller that's included in the box. Alternatively, because the newest versions of the mount have a built-in WiFi connection, you can also control it using the SynScan app for your phone. The tube is a standard Newtonian, with a parabolic mirror and a focal length of 750mm. This makes it an f/5, meaning it's good for deep-space objects, such as galaxies and nebulas. Star clusters and the Moon are also well within your reach, especially in light polluted areas, but planets wi...

I'm a refractor guy. I've seen these things called Schmidt-Cassegrains, and someone told me they can do astronomy with mirrors. One day I might be beguiled by the hyperbolic surfaces of a Ritchey-Chrétien, or the pure beauty of a well-machined truss tube. For now, though, I reckon that if it was good enough for Galieo, Kepler, Brahe and Copernicus, then it's good enough for me. But refractors have their problems. Chromatic aberration, where the different colours components in the light from stars don't focus at the same point, is the bugbear of the design. Of course, other designs do have their problems. Newtonians have coma, Schmidt-Cassegrains have astigmatism, and Ritchey-Chrétiens have an air of intolerable smugness (with apologies to the late Douglas Adams) So how do we manage chromatic aberration? We have two main ways of controlling the way light changes as it passes into and out of a glass lens. First, the amount the light bends is determined by the ...

I've shown astroterrestrial photos before, photos with a subject on the ground with a night sky background. Here's a stunning example. It's Uluru (obviously) from the viewing area with the South Eastern sky behind it. The photo was taken by Prasun Agrawal a little while back, and I was knocked out by its quality. I love the hook shape of the Rho Ophiuchi cloud complex near Antares. But there's more to the image than than this. You can easily see details in the rock, such as Kantju Gorge on the mid-left, that interesting line of circular features in the centre of the rock, and bushes in the foreground. It's an unusually high level of quality. How did Prasun do it? It's a composite: a common way of producing this type of image. Single images are more challenging as you need to focus separately on foreground and background. With a composite, you take a single foreground image and combine this with a "stacked" image of the sky. The stac...

The Hubble Space Telescope has been in orbit since 1990. That's incredible for the high-radiation environment it has to work in. After a shaky start, it's been sending mind-boggling photos back to Earth for more than 30 years. Image: NASA But a few weeks ago the payload computer stopped. The computer equipment on board the HST has many levels of redundancies: there are backups for their backups. So the first problem is identifying the component that has failed. But even after they've found the problem, NASA can't just go up there and start soldering. Since the retirement of the Space Shuttle, they have to do it all remotely. What's currently up there is going to have to do. What's more, while many astronomers on Earth communicate with their equipment at a distance, remote maintenance is difficult when it might be the remote computer that's gone on the fritz! There are a few suspect parts. Initially, NASA though it may have been a bank...

Just take a look at this photo of M16 - the Eagle nebula. The Pillars of Creation are right in the centre of the image, and to the left there's the Stellar Spire. Note the horseshoe shaped structure at the top of the nebula - I'll get back to that. John uses a saxon 127mm FCD100 triplet refractor. This is one of the big ones. For an imaging array, John uses the popular ZWO ASI1600MM-Pro monochrome camera and shoots through narrowband filters. All his exposures are four minutes long. John has presented his image in the so-called "Hubble Palette", where images taken though the Sulphur filter are shown as red, those taken though the Hydrogen alpha filter are shown as green and those taken through the Oxygen filter are shows as blue. As a contrast, here's one of my own photos of M16. It's taken with similar equipment, an ASI1600MM-Pro, a slightly smaller 107mm triplet refractor and narrowband filters, which are presented using the Hu...

With the winter solstice coming up, it's time to send around my regular viewing list. Those of you who have small telescopes or (like me) are stuck in the city, start by searching for clusters, either open clusters (which are pretty groups of stars) or globular clusters (which are tight spectacular swarms). Once you've done that, start looking for double stars, which are pretty in a different way. One day I'll get around to photographing some... For planets, Saturn and Jupiter are currently your best bet. Here's a photo I took of Saturn. I used budget equipment (about $1000), which I was testing for work. Open cluster: Mel 111 - Coma Berenices Star Cluster (06:55 PM) Galaxy: M 87 - Virgo A (01:55 AM) Galaxy: M 104 - Sombrero Galaxy (02:09 AM) Dark nebula: C 99 - Coalsack Nebula (02:24 AM) Open cluster: NGC 4755 - Jewel Box Cluster (02:24 AM) Galaxy: NGC 5128 - Centaurus A (02:52 AM) Globular cluster: NGC 5139 - Omega Centauri (02:52 AM) Galaxy:...