The Science Museum Archive

On Thursday I visited the London Science Museum Archive near Kensington Olympia (not far from Shepherds Bush, West central London, quite far from Tottenham).  You cannot get access to this huge archive without special permission.  This was a cultural visit which may or may not lead to something tangible and if it does, I will tell you about it.  Anyway, the archive is the place where they put stuff which isn’t on show and it’s in this building, Blythe House:-

blythe house 003 Stitch(if you squint you might see a relativist checking his phone near the gate…) .

This building used to be the post office savings bank –  for those who remember, when you left your passbook at the post office, it would go here to be processed before coming back to you.

Anyway, this place is brilliant, and I didn’t know what they wanted to show us.  They took us to a room where there was loads of audio equipment.

Some of the oldest recording equipment in the world is here, including a crying doll, wax and tin-foil recording disks and the horns were apparently to help focus your voice down to the stylus cutting into the wax/tin, which had to vibrate only through the power of your voice…  Then through the range of electromagnetic recording devices, which culminated in cassette tapes.

They showed us crazy stuff like the Cello-phone duotrac:-

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which used photographic film to record sound!  Before this there were only 78 rpm records so this was in fact the first way to record an LP’s worth of music or sound in general, but it came out just before the war and didn’t survive the subsequent nonsense.  The Betamax of its time :(.

Then I spotted this:-

which I realised was a fairlight sampler (and if you don’t know what that is, here is Quincy Jones explaining to Herbie Hancock what that is… ) and I started to get a little bit more excited than I had been before.

Then they took us into the next room…

and we found loads of old synthesizers (and several mellotrons which strictly speaking are not synthesizers).  Priceless old synthesizers.  The last two (moog modular and ARP 2500) would cost many many tens of thousands of pounds each now.  If getting into the place had not been so comically difficult with locked turnstiles, CCTV, alarmed walkways etc etc I would DEFINITELY have stolen some stuff – these things need to be played and that’s it.

So by this point, me and one of the cultural people I was with were in a pretty weird kind of euphoria.  Then things started getting really trippy.  This:-

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Is a Pyro-phone.  Which means it plays music with fire.  Obviously.   And this:-

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Is a sequencer which makes up its own songs.

BUT THEN SUDDENLY WE RAN OUT OF TIME.  So the other group went into the room and we got left in another room.

Which was really boring.

Because it was full of telescopes.

(I mean, come on, I was expecting Salma Hayek to walk in at any moment wearing a Talking Heads t-shirt carrying a massive bag of pistachio nuts and some New Zealand Pinot Noir.)

Oh yes and by the way, this next wooden telescope just happens to be ‘on original Herschel‘ (their words not mine)

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And this was just a small part of a whole room full of goodies!

and then in the evening I got to say goodbye to my old student who is emigrating to Chile, as well as seeing our old friend Ruben from Stockholm.

So, yes, that was a good day.

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Student Shots of the Orion Nebula

As I mentioned I have a group of students doing their third year projects at the moment. We got some stellar spectra and Jupiter like last year.  I wanted to get them to do some imaging as well, we’ve been trying to get some nice images, we tried the Crab but it didn’t come out very well.  So I got them to find the Orion Nebula, take images and then stack and process those images, removing the dark frames.  This is entirely student obtained.

Here is the first effort, student Karan Solanki was first to analyse the jointly obtained image files.  Doesn’t mean he gets the best mark but he’s done a great Job and now gets to move on and do something else.  (I’m keeping them all busy with lots of different tasks).  So lets see if anyone does better.  Of course the Orion Nebula is easy, but they have looked at other objects…  hopefully we’ll see them here eventually.

M42_Combined

M42 Orion Nebula obtained by students, this one processed by Karan Solanki

Best Shot of Jupiter Yet

BESTYET

I have a new set of students doing their 3rd year projects on the telescope and they are very good.  I will post some of their stuff soon.  However, tonight I was out on the roof with them and after even the most enthusiastic one ran out of steam, I still felt like having a go at Jupiter, just a quick go, so I stayed up alone.

Two extremely frustrating hours later I managed to spend about 34 seconds getting this.

I’m supposed to do the following official bit now, people complain when I don’t so here goes:-

3000 shots at 83 frames per second, best 50% stacked, 2.5x televue barlow, skyris 618c, Celestron C14, about a million Zeiss lens wipes and an awful lot of bad language.

The students got some awesome images too, including an object we’ve never seen before.  I’ll report this soon, but I need to give them a chance to analyse their data first… (I’ve done a sneak analysis.  It’s awesome data.)

The Maxwell Society viewing the planetary line up

The undergraduates here at King’s College London have a society called the Maxwell Society.  Named after James Clerk Maxwell, it boasts some famous members in the past including Peter Higgs and Arthur C. Clarke.  Today they run a variety of events throughout the year depending upon who’s in charge that year.  This year’s lot wanted me to let them up to the telescope, which of course I was very open to but I realised that there are not so many cheap thrills with a telescope in the middle of London, you have to work hard for your pictures/spectra and your views through the eyepiece will be so-so.

Anyway, they asked about the planetary alignment which is currently taking place and when I told them they’d have to get in around 6am, they barely skipped a beat before arranging it. So this morning I went in at 5am.  gah.  Anyway around 20 intrepid astronomers showed up at the crack of dawn.20160203_063307

As usual, it turned out the conditions were less than ideal, it was very windy, which meant the “seeing” was very bad, which means that the turbulent atmosphere makes the image extremely wobbly.  That also means you can’t even think about using a very high magnification as the images just get worse and worse so I stuck with a 24 mm eyepiece which gives 156x magnification.  In principle I could combine my 11mm eyepiece with my 2.5x barlow and get some massive magnification but it would look very bad- all the imperfections of seeing are enhanced non-linearly as you increase magnification.   Since all the planets we were looking at were close-ish to the horizon this was not ideal.   Even on a good day you shouldn’t even bother trying to see anything less than about 25 degrees above the horizon in central London.  I tried looking at Mars before they got up there but it was… underwhelming.

However I showed them Jupiter with cloud bands and three moons visible and then we saw Saturn.. it was very shaky but every so often they got a clear focused view of the rings, albeit a bit small.  Then some views of the moon, even the moon looked shaky, indicating how bad the conditions were.  Despite all this, they really seemed to enjoy the whole thing a lot!  I very much hope that they come again to see some better views when the conditions are improved.

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That moment when you realise you’ve been handling ALL your image files wrongly (or 65,534 shades of Grey vs. 254)

Another post so soon?  Well I’ve discovered something and its pretty significant.  It’s really rather embarrassing, but well like I keep saying I REALLY don’t know what I’m doing and I try to pride myself on always admitting when I am wrong, (and if necessary apologising although on this occasion I don’t know who I’d apologise to.)

I recently discovered something about the free image processing software GIMP (photoshop for cheapskates) – it is 8 bit.  That means within the image every pixel has a value between 0 and 2^8-1 which is 255.  If it is 0 then the pixel is completely dark and if it is 255 then the pixel is completely saturated and there are 254 shades of grey between those two extremes.

I also recently discovered something about our camera, it is 16 bit, so each pixel has a value between 0 and 2^16-1 which is 65535 with 65534 shades of grey in between.

Unfortunately I’ve been using GIMP to stack and analyse our images.  So if the camera was reading 100 on a particular pixel out of a possible maximum 65535 then once you read the file from the camera into GIMP it will divide everything by 256.  The closest integer to 100/256 is zero.  If we were to stack 20 such images, then 20 times zero is still zero.  If you use a proper 16 bit software, you would have 20 x 100 which is a respectable 2000.

So basically we’ve been missing out on a heck of a lot of detail.  Luckily I’ve still got the original image files, so I’ve been spending the last part of my holiday re-analysing and stacking some of those old images.

The difference is remarkable:-

 

These two images come from exactly the same data, cropped very slightly differently.  The one on the left uses all 16 bits while the one on the right is only 8 bit.  So all this time we’ve been getting much better images than we thought.  This makes me even more eager to get out and look at more things, but the weather is awful.  Luckily I’ve got a UG project coming up with the telescope, so that will give me a chance to get some new images…

So I do feel like a bit of a fool but a relatively happy one…

End of Cloudy 2015

The weather has been horrible for months, its been mild but terribly cloudy.  For example, the only two clear nights in London lately have been Christmas Eve and New Year’s Eve, both of which I had plans for. It has really been very difficult to get good views of the sky from London for that whole time..  We haven’t had chance to do as much as we would have liked in continuing to learn how to use the telescope.

Messier 81, about 5 times as far away as Andromeda.

Sunayana and I did get this image of M81 earlier this month, which is a large Galaxy not very far away but it should be a lot brighter.  I hope you can see there is a galaxy there though!  We’ve also been trying to learn how to use Colour as you can see with this image of the Ring Nebula M57

M57

which is not bad for the time being at least.  There are very many tricks that we are learning about stacking images, but we haven’t started to do things like subtracting flat fields and dead pixels.  Hopefully we will get better weather in 2016.  Certainly we are looking forward to the return to the skies of Jupiter which already feels like an old friend.  February will be good for that.  However we want more galaxies and more student access to the telescope, which we are working on and will report more about soon…

best wishes for the new year to you all.

Sunayana’s image processing Software

This post is by Sunayana who has been helping me with the telescope over the past year.  Unfortunately she is now leaving us to pursue an MSc in Astrophysics at UCL but I sincerely hope she will find time to come back and visit us up on the roof as often as possible.

One of the key purposes for the KCL telescope is its use within third year project work. Trialled in early 2015, the first set of project students used spectroscopy to analyse the composition of elements in the atmosphere of Jupiter, the Orion Nebula and Sirius. This involved grappling with raw images, plugging them into software and outputting a spectrum of intensities plotted against a range of wavelengths. In pursuit of a more efficient solution, a challenge was posed – to write concise image processing software which would take any greyscale image of emission/absorption lines and immediately convert it to its corresponding spectrum. This would circumvent the tediousness of cropping images manually and having to abide by the constraints of external software, allowing for flexibility and swifter analysis.

So immediately I got to work, contemplating the most suitable programming language for manipulating image files in a streamlined and precise way. Reluctantly turning away from my familiarity with FORTRAN 90, I embraced C for an easier ride into image manipulation.
The programme opens a grayscale bitmap chosen by the user and scans each pixel, processing its intensity value. Since these are 8-bit grayscale images, each pixel contains only intensity information and therefore has a value between 0-255 (2^8). Then, the intensity of pixels in each row for a given column is summed and plotted. So, going across the image, any detected non-zero intensity value for a given column will yield a peak in the spectrum. Proportionally, the larger the number of non-zero intensity pixels, the bigger the peak will be. An all-white vertical line across the image, for example, would have the maximum intensity possible. Of course, the non-zero intensity pixels represent the areas on the image where characteristic emissions are occurring (or vice versa for zero-intensity pixels where absorptions are occurring).

It is important to note that the intensity of each pixel is typically non-linear and discrete data analysis of an image which supposedly contained equal increases in intensity across its width was terribly unhelpful in the early stages of writing the programme. Finally, the number of pixels across the width of the image is calibrated according to the wavelength range of the spectroscope (between 300nm and 1100nm). Therefore, a spike identified at the 50th pixel of a 200 x 200 image, will translate approximately to a peak at the 500nm mark. Automatically, all the pixel data of the image is written to a readable, graphable text file which is easily plotted on any data analysis software including GNUPLOT, Xmgrace and Microsoft Excel. Hopefully, this swift and user-friendly method for image manipulation will serve the next cohort of third year undergraduates well. Watch this space…

More recently, we have been trying to ratify, more broadly, student access to the telescope in both an academic and extracurricular capacity. We’ll be instrumentalising the (optimistic) novelty of a telescope on a rooftop in central London through termly events, titled ‘A Night on the Roof,’ where undergraduates will be able to attempt to find and focus on solar system and/or deep sky objects according to visibility. This will hopefully be the first of many streamlined operations to allow wider access to the work being undertaken at the telescope. Later we may have a series of public lectures on astrophysics and related themes, which might feature a live-feed from the telescope as an additional bonus.

We have been attempting to make the dome rotation smoother and now there an additional monitor has been mounted to the wall inside in the dome so we can have the computer in the hut but still work in the dome (see below).DSCF1656