Part One Of Our Course On Astrophotography, This Section Tries To Give

Transcript

Slide 1 Capturing the sky with a Digital Camera Part one of our course on astrophotography, this section tries to give a whistle stop tour of the basic technique and some of the pitfalls of this fascinating but often frustrating hobby. Paul Fellows MA FIET FRAS Slide 2 Eye…Camera…Telescope • Your eye • 7mm Pupil That’s for young folk too Older eyes don’t open up so far! • Your Camera • 14” ‘Scope • 35 mm Lens That’s five times the width = 25 times the light • 350 mm Work it out. It captures the light of 2500 eyes Its all about light gathering power Our eyes are amazing, but they can only let in a certain amount of light due to the size of the hole – the pupil – which can be up to 7mm across , though in older people it often fails to fully open and makes vision in poor light more problematic. Cameras have much bigger lenses, and of course the main purpose of a telescope is to gather up enormous amounts more light than the mark one eyeball. Slide 3 Can I use a Phone-Camera? • The lens on you phone camera is probably no bigger than your eye. • So its not really a good plan Though people will try to sell you add-ons… Typical smartphone cameras are amazing these days, with high numbers of pixels and are great to have around – as long as there is enough light They are not really much bigger than your eye after all. However you can get attachments with wider lenses, often with zoom capability, but these are still no match for the power of a full 35mm lens – let alone a modest telescope. Slide 4 Some Typical Cameras Nikon Coolpix 4500 Panasonic Lumix DMC-FZ38 Canon EOS 600D Full DSLR • Simple Digital Camera • 2 Million pixels • non-removable lens • • • • • 18 Million pixels • Lens removable and interchangeable 12 Million pixels 18x optical zoom Lens Plus 4x digital zoom Non removable Remember! Make sure you get a remote control or “cable release” Or better still an “intervalometer”… Here are three cameras that I have played around with and tried out both on their own and with various telescopes The key characteristics are shown, with increasing numbers of pixels, better lenses and improved electronics across the range. With a telescope, you often want to remove the camera lens and so the DSLR on the right is the winner overall, beating the others on all fronts but many of the images in this course are taken with the others, so one should not discount them immediately. Slide 5 ISO = “Digital Film Speed” Nikon Coolpix 4500 • 800 Faster Film means shorter exposure times – right? But this comes with more “noise” Lumix DMC-FZ38 • 3200 Canon EOS 600D • 12800 Hint: There is a reason that the high setting is “H” on the Canon and that 800 on the Coolpix comes up in red ISO was a measure from the film world for the sensitivity of the material in the film. Numbers like 40 or 100 being typical. Digital cameras are much more sensitive than film every was, but we still use the numbering system to identify how “fast” the sensor is. However, this is controlled to some extent by the electronic amplifier circuit – and it pushed too far can result in the electronic “noise” being amplified as much as the signal, or worse. What is Noise – whenever the electronics tries to make a measurement of the level in a pixel, it inevitably can make small errors in the measurement due to a range of factors, such as interference from elsewhere, and indeed just from the heat in the system making the electrons a bit jumpy. In fact the hotter the camera the more noise you tend to get. Perhaps its fortunate that astronomy involves standing out in the cold. However, the internal electronics of the camera can often warm it up – and the longer the exposure, the more it can warm up. Slide 6 Star Trails Turn the earth’s 360 Degrees per day rotation to your advantage! This is about 3 hours of rotation Remember • 15 degrees per hour • That’s 0.25 degrees per minute • Stop-down the lens • Drop the ISO setting to the lowest Slide 7 Hot tip • Use the intervalometer to create a series of short exposures of say 5 seconds, Once Every minute • Then use photo shop to layer all the images Coloured Star Trails Advantage of a camera is that it can pick up the colours of stars really well Great fun – just try opening the shutter with the camera held still for a long time and you get to see the rotation of the earth! The slide makes some suggestions for the settings, and if you have an intervalometer that can operate your camera for you taking a series of equal shots at intervals, then this is made easier, and much less tedious! The human eye can really only see colour for bright objects due to the nature of the two types of light sensitive sensors in the eye. The rods are very sensitive, but only give a monochrome image. The less sensitive cone cells work in normal daylight and give the red, green and blue signals that let us see in colour. A camera can pick up the colours of the stars much more easily than we can, and in fact being slightly out of focus, or letting the stars “trail” make this very apparent Slide 8 The Moon, Venus and Jupiter Earthshine, and even a little hint of detail Here is a simple shot of the moon, venus and Jupiter which all happened to be in the same area of the sky at once. The Nikon coolpix has managed to grab these, and even show some of the un-lit side of the moon via the Earthshine… The light reflected off the Earth that is illuminating the night side of the moon. You can just make out some details. Slide 9 Orion : point and hope Camera placed on the ground, with the lens aimed at Orion Settings: ISO 400 Manual “M” mode With “B” Bulb exposure time As the slight says, this is a picture of Orion, taken as an experiment with the settings. The main stars are visible at least. Press the button, and count to 30 Slide 10 Taurus And the Seven Sisters Camera placed on the ground, with the lens aimed at Orion Settings: ISO 400 Manual “M” mode With “B” Bulb exposure time Press the button, and count to 30 And another one, this time aimed at Taurus, with the Pleiades cluster showing. Slide 11 Orion, a longer exposure, and this shows the star colours • Orion – and the lights from the Guided busway • However it also shows the scourge of the astrophotographer – orange light polution from distance street lights! Coolpix, – propped on the fence – 30 seconds – The nikon’s lens is too small – its ISO settings don’t go very high – so you really need 30 second+ exposures – and that means tracking… Slide 12 Stepping up… The lumix, with its big lens, optical zoom and high ISO settings does rather better immediatly The effect of a bigger lens- the Lumix camera can do so much more because it has a better light grasp, and is more sensitive, and with more pixels too! you can get great wide field shots without tracking! Overall a step up in every way compared to the coolpix – but there coolpix does have a trick up its sleeve You can even begin to see barnard’s loop in orion in this image. Slide 13 The moon 1/250th of a second Rested on a fence! A happy snap of the moon. Because the moon is so bright a very short exposure is required – and so actually camera shake is not a problem so you can even do this hand-held. Slide 14 The Crescent Moon Another more zoomed moon with the power of the lumix • Lumix – 1/400th Second – ISO-400 – F/4.4 Slide 15 Slide 16 The moon during a total lunar Eclipse The Sky - At Night? Saturn Lumix , 60 seconds, at ISO 80 and F2.8 at midnight! The blood moon at an eclipse – a longer exposure here because it was rather dimmer – but you can figure out how long if you ever get the chance! The night sky is not really black. This picture looks like broad daylight, but it was a very long exposure at wide-angle with the lumix, and as per the arrow, you can see Saturn in it. The background of the sky is always an issue, and its never really black because of light pollution and a phenomenon called airglow. Slide 17 Far from the madding crowd. This is the milky way taken from the top of a Scottish island devoid of light polution 30 seconds, with the canon camera and a 50mm lens. Slide 18 Longer Lenses? Great for the moon, but at this magnification you need to track! Increasing the focal length of the lens you use zooms you in – increasing the magnification of “image scale” of the picture. Smaller objects get larger, and large objects overflow the field of view. The Canon with a 500mm telephoto lens on a home made mount It makes finding and centring harder And focussing more critical And of course as the light is more spread out, you will need to expose for longer to compensate That can work on the moon without yet needing to introduce tracking of the object, but faint objects are another story Slide 19 The moon just before half phase • Cannon EOS and a 50mm ‘scope at Prime focus Another snap of the moon, using the canon camera with its lens removed and it hooked up to a small telescope Remember! • You’ve removed the camera’s lens So turn off autofocus! Slide 20 Exposure Time - Moon • Try 1/250th Remember: • Use manual mode “M” • Set the exposure time with the dial • Shoot, and then try other settings! • Find a level where the brightest parts are no over-saturating And the moon again with some hints on controlling the settings on the camera You will want to turn on manual mode to do this. The automatic settings provided don’t tend to work for astronomy! Turn off autofocus and do it manually, set the ISO yourself, and finally, TURN OFF THE FLASH or you will get a surprise! Slide 21 Exposure Times - Planets • Mars, Jupiter and Saturn – start with 1/15th Remember! • Planets appear small • And you need lots of pixels • With A-Focal you can either use a shorter focal length eyepiece, or a “barlow” lens to increase the magnification Some typical settings for the brighter planets are shown her, along with some images from a very small telescope with a camera. Because these are around 1/15th of a second, you can get away without having to follow the movement across the sky Slide 22 Gamma Andromeda Often forgotten, and worth doing – some double stars show up rather well with a long lens and especially those that have good colour contrast like this one. Don’t forget to try imaging some nice colourful double stars Slide 23 Brian…. Slide 24 Colour vs Black and White The Bayer Matrix Time to heat the water for tea Colour cameras use a filter to make the sensor array – which would otherwise be sensitive to all wavelengths (colours) – pick out the colours separately. Pixels are grouped in fours one Red, one Blue and a pair of greens, and a colour-super-pixel value is made by combing these. The pattern of the filter is called a bayer matrix. Note that • each real pixel is therefore only getting 1/3rd of the light, the other two colours being blocked and • The pixel resolution is halved. For this reason some dedicated astroimaging cameras are black and white, doing away with the bayer matrix. This lets them image without wasting any of the light, and at full resolution of the technology. You can always reconstruct a colour image by using external filters, and stacking three images up – or more if you want. Slide 25 “Modding” a DSLR Don’t try this at home How to void the warranty of your camera in the name of Astronomy! There are people who will do it for you for a fee, and be prepared to never have a warrant ever again. In addition to the bayer colour matrix, normal cameras have to balance the natural appearance of the white and colours that they measure to try to match the way the human eye perceives things. To do this they block out parts of the spectrum and usually block the deep red end down into the infra-red which the electronics could otherwise record, but to which our eyes are not sensitive - as shown in the graph As astrophotographers though, we want all the light we can get, so we can remove this filter and gain access to the IR part of the spectrum. We can also as part of this INCREASE the sensitivity to the deep red part of the visible, and it just so happens that a key colour line from Hydrogen – the “alpha” line at 656 nanometers wavelength is in this zone. This is often the main light output from nebulae – and so we gain about a factor of four if we have the sensor filter un-blocked at this wavelength. Slide 26 Infra-Red Talking infra-red, here Is a chart that shows which wavelengths make it to the ground. Its no conincidence that our eyes see in a band which the atmosphere lets in, but there are longer wavelengths that mostly get through, and we can try to use them without going into space if we choose carefully Note how the radio guys have a huge advantage too. Slide 27 Visible vs Infra-Red Left and right, visible and IR images from cambridge of the orion nebula Slide 28 The spin of the earth is such a nuisance for long exposures. Longer Exposures? • So, you’ve pushed the ISO to max, and used the biggest fattest lens but there will be a limit.. And with a telescope showing perhaps ½ a degree of the sky, any object will sweep through in just two minutes. • If you want see fainter things, you will have to do longer exposures • And that means you will either have to stop the world turning, or get a tracking mount of some sort At higher magnifications, that gets even worse of course, and images become subject to motion-blur very easily Slide 29 A “Barn Door” mount Tracking without a telescope or a motor Hinges Camera on its cradle can be pointed anywhere Winding handle, raises this side Rubber Band to hold the tension Remember • Point the hinge north • Open the shutter • And rotate the handle once per minute But we can track it with a barn door mount. This is called a barn door because it is a fixed plate, with a hinged flap that can swing open. The camera is mounted on a tilt-androtate fitting that can point it anywhere in the sky. The mount is constructed with a tilted hinge, the angle of which matches the latitude that you want to use it from. In our case in Cambridge that would be 55 degrees. By aligning the mount North-South, the hinge then points up at the polestar and so as the hinge swings open, the movement of the camera mounted on it compensates for the rotion of the earth, If you open the hinge at the right rate. The winding handle controls that. Rotating it forces a bolt to raise the “Barn Door” flap. Rotating the handle at the right speed is then all you have to do – and the cunning desing makes that easy as we shall see on the next slide Slide 30 How ? • Use these dimensions • Each turn of handle raises that side by one thread on the bolt. – That’s 1/20th of an inch, or 1.27 mm – Its 290mm from the hinge – Some GCSE maths – Tan(theta) = 1.27/290 – Theta = 0.25 degrees • So one turn per minute matches the Earth’s rotation Here are the dimensions and the math that shows how it works to give the right rotation speed. We need to have the hinge open at a rate of 360 degrees in 24 hours, which as you now know, but can easily work out, is 15 degrees per hour, and therefore 0.25 degrees per minute. To achieve this we make the distance between the hinge and the winding bolt 290mm, and use a bolt with a thread-pitch of 1.27 mm (20 turns per inch) Why those numbers…? Each complete turn of the winding handle opens the barn door by that 1.25mm – the bolt’s threadpitch.Some simple trigonometry then on the long thin triangle that we created: The “adjacent” side to the hinge angle is 290mm and the “opposite” side is 1.27mm and so the Tangent of the angle at the hinge is TAN(theta) = 1.27 / 290 And this is such that theta is 0.25 degrees. So, if you wind the handle a one revolution per minute, you will open the hinge at 0.25 degrees per minute. To do that get a watch with a second hand that sweeps around, and move the handle in step with it. Simple! And effective. If you use a different bolt thread, you can work out the distance to mount it at in the same way Slide 31 Sword Handle In Orion • Nikon • With a 300mm lens Slide 32 Cable Release • No! You won’t be able to hold it still! You can get simple ones which you press and the exposure time is controlled by the camera Or you can set the camera to “B” for “Bulb” and hold the button down for as long as you want Or get a fully programmable intervalometer… Barn door tracking with a 300mm lens A 300 mm lens gives a nicely framed view of the sword handle in Orion, using a few minutes of exposure, tracked with the barn door mount Again, you will need a cable release so that you can sensibly set the camera up and then trigger the exposure of your shot with one hand, while you wind the barn door handle with the other and watch the watch second hand with your eye there is a lot to do otherwise and trying to press buttons on the camera body will wobble everything and disturb the shot Slide 33 Intervalometer About £15 Set the delay before it starts shooting The interval between shots And the length of each exposure And how many to take So you can trigger a long sequence and just let it do it while you go an have tea! With these “programable” remote controls you can set up a long series of shots let it run while you concentrate on tracking or indeed if you have a motorised tracker, just leave it to do its thing. They control the opening and closing of the camera shutter (the exposure time), and can be told to do a number of shots one after another, which is great, but also allow you to set an initial delay – so that any vibrations from fiddling with the camera can die down, and you can get out of the way, and not get you face and the headtorch you had on to read the settings as part of the image. And, they let you set a gap between the shots – the interval between them can be very useful because the camera often takes time to process and save the image to its flash card, but also it can be a good idea to give the camera electronics a chance to rest and cool down between shots. Otherwise the chip can heat up and then the noise level caused by all those hot little electrons jumping about in the chip increases Some people contrive to have cooling fans and other fancy gear to combat that, it’s a serious problem Slide 34 Tea? Half time Slide 35 Using a Digital Camera with your Telescope A-focal imaging? Exposure times? Cable Release? Tracking? Slide 36 What if I just put my phone cam to the eyepiece? • Well, yes, it works. Sort of… You can do this, I have, and it can work – but its really too wobbly by a long way – find a better answer if you possibly can! The chance of getting the lens lined up left-right and up-down, and having it flat-parallel and at the right distance so that it focusses properly, AND then pressing the button without messing up it pretty thin. But it its not your scope, and you only have a moment or too --- try making it a video not a single shot, you might then get one or two frames that are OK Slide 37 Imaging through the eyepiece There are three different ways to organise the optical path. • • So called “a-Focal” method – This does not mean you don’t have to focus it! – It means you have both the eyepiece AND the cameralens in place As in the picture Telescope main optics, and eyepiece + camera with lens body and sensor = “A Focal” (2) Remove the camera lens and remove the telescope eyepiece … just using the telescope main optics as a giant camera lens if you linke Telescope main optics, + camera body and sensor = “Prime Focus” (3) Leave the eyepiece in but remove the camera lens This also works and is called “Eyepeiee projection” – it not a very common way to go by has some advantages for imaging planets. Slide 38 Imaging through the eyepiece The Coolpix with an eyepiece attached Plugs into the telescope Focus, Exposure, Shoot! Various adapters and other Heath-Robinson devices are available to attach almost any Camera Remember! • Turn the flash off • Turn the auto-focus off • Set the focus to infinity • Focus as normal with the telescope The nikon coolpix camera is unusual in that the fixed lens has a thread on the front that was designed to allow external filters to be used with it. A couple of companies seized on this and made eyepieces that have the same thread for their foam eyecomforters. So you can remove the latter, and fit the eyepiece to the camera as in the picture above. This then plugs in neatly into the eyepiece holder tube in the focuser and you are ready to go. Much neater than some of the bracketry that is shown in the other images, which looks more likely it will poke you in the eye in the dark to me. Slide 39 Prime-Focus – DSLR cameras • Remove the camera’s lens • Plug the body of the camera straight onto the ‘scope • You will need a T-adapter (or equivalent) Remember! • The T-ring adapters are different for Canon, Nikon, and others • You can’t do prime focus with fixed lens cameras --- (Sorry Coolpix, you’re out!) Perhaps the best way to go if you have a camera with a removable lens is to get a T-adapter and go primefocus (no eyepiece) This minimises the number of glass elements in the optical train, and that’s a good thing as each can degrade the light’s sharpness, scatter, absorb or reflect it and give trouble – not to mention have dirt on it. In fact a common problem with other methods can be that there are so many elements in line that each get s slightly misaligned and the whole result is poor. Note though that while people refer to a “standard T adapter” there are three different fittings and you need the right one for your camera – provided of course the lens can be removed at all…. Take your camera to a telescope shop and make them show you that it fits! Slide 40 Tracking is needed as we have said for long exposures Do I need tracking? The “Cardboard” 6 inch, non tracking newtonian, with the coolpix camera But some bright objects don’t need long exposures event when we have used only a modest telescope. The moon is so bright that even a small scope will need a very short exposure and no tracking is therefore required. Here is an image of the moon taken through a home made 6 inch telescope with no motor drive to track the sky Slide 41 Likewise the planets can be bright enough for short un-tracked exposures Do I need tracking? The “Cardboard” 6 inch, non tracking newtonian, with a webcam Slide 42 Using Video Here is Jupiter from the 6inch “cardboard scope” The image of Jupiter was plucked out of a video stream – shown here. The scope was equipped with a cheap webcam, with the webcam’s lens removed, and the eyepiece of the telescope removes (Prime Focus mode) The telescope was line up carefully on Jupiter and focussed, and then a video captured as the planet swung through the field of view. This was a bit fiddly to achieve, as the field of view was very small, and the planet only took about seven seconds to swim into and out of shot, but at 5 frames per second we got a few nice images Slide 43 Simple deep-sky photography All the deep-sky objects – the nebulae, clusters, galaxies and so on that lie outside our solar system are faint. The are too faint for “short” untracked imaging. So we are going to need to raise our game if we want to capture these. On this slide : The Orion nebula, the Hercules Globular Cluster and the Blue Snowball Slide 44 Deep-sky means Tracking The Earth turns ¼ degree per minute. That’s half the size of the moon on the sky. In just one second, an image of Saturn will drift by its own diameter. Exposure times of 30s or so will see your object right out of the field of view Can you tell me what this is a picture of? An un-tracked telescope image of … something… I think its saturn by you get the idea Slide 45 Deep-sky methods • You can still use the A-Focal method • Through the eyepiece with cameras like the coolpix Or • You can use Prime-focus • With a DSLR body • Or a specialised imager The methods and cameras discusses can still be used, but there are now a range of specialised imagers such as the meade DSI shown here and more modern ones with much improved performance that can be used. The imagers tend to have smaller fields of view and are good for detailed shots whereas the larger chips in the DSLR cameras are good for wide-area shots And of course we have to consider the choice between single-shotcolour of general purpose cameras and the dedicated monochrome imagers Slide 46 A-Focal With the Coolpix The good old coolpix can get you a long way mind! I still like using it and its now 15 years old as a design! Orion Nebula, 30 seconds, Nikon Coolpix On 28mm eyepiece and 250mm Newtonian Remember! With A-focal, a range of eyepieces or barlow lenses lets you choose the area of sky to cover Slide 47 A-Focal With the Coolpix Again, a decent shot of the cluster with the trusty coolpix, on a ten inch telescope The exposure time of 15 seconds meant that we needed tracking, but it didn’t need to be perfect. M13 in Hercules with the coolpix, 15 seconds Slide 48 Prime Focus with the Canon EOS However, the modern DSLR canon EOS does rather trounce the coolpix in comparison as this image shows. It was of course more expensive though. Same telescope though. • 18 Million pixels vs 2 Million Slide 49 M51 – the whirlpool • Canon EOS, Prime Focus of 250mm F4 Newtonian. ISO 800, 2 minutes Here we see the M51 whirlpool galaxy, and you can see how the large area of the chip for the canon, combined with the 1000mm focal length of the main telescope (a Meade scmidt-Newtonian ten inch ) sets the galaxy in a wide area of sky The galaxy is a bit small like this, and a boost to the focal length would have enlarged it, perhaps a 2x or 3x barlow lens could have helped – but then the exposure time would have had to have been increased by a factor of 4, or 9 and the tracking on that telescope was not that good! If you compare this to the result with the dedicated meade DSI and its smaller sensor, the galaxy nearly fills the field, even with the same 1000mm focal length. Slide 50 Deep Sky Focussing How do I focus on things I cannot see? • Getting your images focused is definitely the hard part • The simplest way is to focus first on a bright star and then lock the focus in position. • Then move to the object you are looking to photograph Focussing is hard, really hard. And good focus makes all the difference Either • The target is so faint you can’t see it at all • Touching the focus knob makes everything wobble • Atmospheric turbulence makes the image twinkle so you cant see if you have it right Or all of those. You can deal with (a) but focussing on a nearby star that you can see (b) Is addressed with a motor controlled focuser, more of which anon And (c) well, there is a clever gadget that can help… Slide 51 Focussing with a mask • Bahtinov was quite smart! A bahtinov mask, creates diffraction spikes that come from the star, with two angled pairs of spikes that form a cross-hair and a third line that needs to intersect them. When you change the focus, the angled ones stay put, marking the centre for you But the clever part is that the third line moves laterally. See the left image, the third line is clearly offset leftward. This tells you it is out of focus. Changing the focus moves the line and your task is to get it to split the others right down the middle This technique is immune to the twinkling of atmospheric turbulence But remember to remove the mask of the front of the telescope before you image! (we've all don that haven't we!) Slide 52 Left – out of focus Right, spot on….? Well actually it’s a little off to the right isnt it… Slide 53 Make life easy.. Par-focalise your eyepieces So they need the focuser in the same place as the camera You may not be able to do this for PRIME FOCUS… You can also get these clever little par-focalisation rings to fit onto the eyepeices you have and make them so that all the eyepeices sit in the tube at the same focal position correctly. This is OK, and worked for me with the A-focal setup and the coolpix camera But with the Canon at prime focus, you have to wind the focus in so far that the eyepieces need an extension tube and it all gets a bit messy. Its worth doing if you can though because anything that saves refocussing is a belssing Slide 54 Go Robo… • Motorised Focus will make it much easier • Some ‘scopes have this out of the box • Others mean a visit by Mr.Heath and Mr.Robinson I mentioned that you cant hope to focus well if you are touching the tube. The motorised focuser solves that, but get a good one, making your own heath-robinson might look like a great idea but it will probably just cause trouble Slide 55 Putting it all together So, now a series of image to round up and whet your appetite ALL of these have been taken by myself, from a Cambridgeshire back garden observatory Its amazing what you can do these days without needing Hubble or Voyager! Slide 56 The planets Mercury, always tricky as its so close to the sun Venus, very bright, but can be hard to image without issues such as atmospheric dispersion getting in the way Mars, nice detail, but this was taken when the planet was at close approach AND high in the sky in the winter. At other times is can be rather small and difficult Jupiter – clouds, belts, the red spot, fabulous colours. 2000 frames of video with a glorified webcam called the QHY 132 E and a 14” Scope. Saturn, the planet has been low in the southern summer constellations and I’ve yet to get what I think is a great image. This one is OK, but I’m sure will be improved on Uranus and Neptune as small and on the limit of the video-based imager that I have, however equipment keeps improving! Slide 57 Comets Its been a while since I tried to capture any comets. I caught these two (Holmes on the left, Machholtz on the right) but imaging these is another whole speciality of its own. Often by the time they are bright enough they are moving across the star fields fast enough that simple earth-rotation-tracking is not good enough, and you have to abandon it and track the target itself. Or so I am told! I have yet to have a go! Slide 58 Some nebula The top left california nebula is an example of one that is so large that here I used a camera with a 70mm lens, riding it “piggy back” on the main scope. The main scope’s field of view would have only shown a tiny portion of it. However with the main scope superbly set up to track the sky we can do long exposures using the piggy backed camera and its own lenses, and the intervalometer, and capture wide area shots with long exposures. As this nebula is glowing due to ionised hydrogen, a special H-alpha filter can be uses to good effect – cutting out all the light polution and just letting us see the light from the gas in the nebula. The Horsehead nebula also benefits from this H-alpha technique, and is shown imaged - through the telescope this time Then lower left is the dumbell nebula in mono-chrome with the DSI imager, and the crab nebula at the lower right in colour. Slide 59 Planetary nebulae are the remains of dying stars Here we have (Top left to bottom right) The blue Snowball The Eskimo Nebula The Dumbbell Nebula And The Ring Nebula These are generally rather small, and suited to imaging through the main telescope as a result. To the eyeball they are small grey blobs with no colour, but what I love about using the camera is that the true colour beauty of them comes through Slide 60 The rosette nebula – Again this is a hydrogen alpha filtered shot with the camera piggy-backing on the main scope. This rose-like nebula is almost invisible to the eye even in the 14” scope at low power all you can see is the stars at its centre. It is so large that the full moon would drop into the whole in the centre that you can see – and so a short focal length camera lens is the only way to capture it all. Slide 61 Top left, the Lagoon nebula (Canon DLSR prime focus on the 10” F4 reflector) Bottom Right, the Trifid nebula (same kit) Bottom Left, this is the great Hercules globular cluster – (same kit) And top right was supposed to show the flame nebula but the trifid nebula image is blocking it. Oops. Slide 62 Galaxies galore Top left to botom right, and all taken with the meade DSI pro monochrome imager The Triangulum galaxy our secondnearest neighbor (M33) The Whirpool galaxy and its companion, wth the tidal tails(M51) The Sombrero galaxy with is dust ring (M104) The Outer Limits galaxy and again its mid line dust lane show fully edge on to us (NGC891) Slide 63 Top left-bottom right Catherine wheel – a barred spiral (NGC 2903) The bubble nebula The sunflower galaxy And Bodes Galaxy (M81) All taken without the benefit of a high mountain, or rocket assistance. I hope you are inspired to have a go too.