Astrophotography with a DSLR and Tripod (Part One)

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Most people, on hearing the word "Astrophotography", will immediately form a mental picture of a telescope. That's understandable, as most people tend to think that Astronomy itself revolves around the use of a telescope. The latter is partly true, although you can get a lot of pleasure from the night sky just by using your eyes, and even more so if you have a pair of binoculars.

Astrophotography, however, is not solely the domain of the telescope enthusiast. Very good images of deep sky objects can be obtained with just a camera. You'd be amazed at how much is up there, and how wide an area of the sky some of this stuff covers, but which we can't see purely because it's all too faint. For example, the Andromeda Galaxy, the nearest spiral galaxy to our own, is about six times the width of the full moon in the sky - quite amazing (I wonder if nocturnal animals can see it?). The core of Andromeda, the bright bit in the centre, can actually be seem with the naked eye if the skies are dark enough (some lucky people actually have skies that dark!), and can certainly be seen with binoculars, although it will be nothing more than a faint smudge.

Although the image below was taken with the aid of a tracking mount (not a basic tripod), it gives you an idea of what can be done with just a camera and 200mm kit zoom lens:

M31 The Andromeda Galaxy

This image is actually made up of thirty 4 minute exposures, so it was necessary to use a tracking mount - a mount that follows the apparent movement of the stars across the sky - otherwise the stars would have been long streaks. Andromeda isn't an ideal target for a 200mm lens - 300mm would be better, but I don't own one of those ;)

But - you don't need a tracking mount to get some very nice images of the night sky. If you have a camera and a tripod, you're adequately equipped to take some decent images. A DSLR (Digital Single Lens Reflex) camera is preferable, rather than a compact, as ideally you need full manual control of the camera. If you've never done any form of night sky photography before, and don't know where to start, try this simple exercise:

First of all, make sure you are familiar with your camera, not just how to use the thing but the menu settings and options that are available to you. Different makes of camera have different settings but all should have the following options somewhere in the menus:

1. CSM/Setup Menu: Set this to Full, so that all the menu options are visible.
2. White Balance: Set this to Daylight, which seems to work OK. There isn't a setting for Pitch Black in the Middle of the Night!
3. ISO Auto: Off. You need to set the ISO manually.
4. ISO: Set this to at least 1600. If you have a modern camera (modern as at 2012) then you may have ISO settings much higher than this available to you. If you do, you could try 3200, or even higher, but the higher the ISO setting, the noisier the image, so don't overdo it. Try 1600 or 3200 first. 
5. Auto Image Rotation: Off, definitely.
6. Image Quality: Set this to RAW. RAW files hold more information, but the file size is larger. That shouldn't be a problem with a decent sized memory card in your camera.
7. Long Exposure Noise Reduction: If this is available, turn it on. This will double the time it takes the camera to dump the image to the memory card, but that won't be a problem for this exercise.
8. You want to be using remote shutter release, either infra red or cable (or whatever system your camera uses), so set this option, whatever it may be called in your camera. This assumes you are equipped with the necessary bit of kit to remotely control the shutter release - if not, don't worry too much.

Constellation of Orion, 20mm, 15sec, ISO 3200 by Dave DeHetre

Now, a couple of things that you probably already know, but I'm going to mention just in case: A Prime Lens is a fixed focal length lens i.e. not a zoom. A Fast Lens is a lens with a maximum aperture below f4 (some consider f4 to be fast - it's a matter of opinion). Generally speaking, a fast, prime lens is best for astrophotography, but if you don't own one of those (like me), a slow, zoom lens will do just fine (but not too slow!).

OK. Set your camera to full manual mode (this may require a setting on the lens as well). Put your camera on your tripod and go outside, preferably when its dark and moonless, and preferably when there are no clouds in the sky! Make sure you can see some stars - some nights are cloudless but the visibility is terrible. The more stars you can see (and the less they twinkle), the better. Make sure there are no lights on in the house shining at you - you want it as dark as possible. This also apples to neighbour's lights, but I wouldn't suggest you knock on their door and ask them to turn them off! If lights are a problem, at least make sure you can point your camera away from the lights. Use a focal length of about 50mm or less (wider), select the widest aperture (lowest f number), set the focus to infinity, and select a shutter speed of about 10 seconds. Now point your camera at the sky - anywhere will do for this exercise, but stay away from any areas of light pollution if you can (the sky will be orangy where there is light pollution). Make sure the tripod is nice and steady, and release the shutter. Now keep still until the shutter closes - no really, keep still; cameras on tripods are very sensitive to vibration.

Now take a look at the result. You may be surprised at how many stars are in the image compared to how many you can see in the sky - the image should show quite a few more. That is your first astro image (well, it may not be, but I'm assuming you've never done this before!) Zoom in as as far as you can on the LCD screen and examine the stars. If you are using a good quality prime lens, they may be in focus, but the chances are they are slightly out of focus. You'll know this because they will be slightly "blobby" as opposed to nice sharp points of light. If setting the camera to infinity was all that was required to achieve focus, a DSLR astrophotographer's life would be a lot simpler, believe me! Unfortunately, it doesn't work like that - most lenses go slightly past infinity (which doesn't sound possible, does it?) so you need to do a bit of work to get perfect focus. If you have a distant street light visible, you may be able to switch your camera to Auto Focus and focus on that, or the Moon if it's out (best to do this on a moonless night though - the Moon's inclined to be a little bright!). If this isn't an option, you'll need to make a tiny adjustment to your focus ring (and I mean really, really, tiny) and give it another go. Zoom in again - do they look better? If not, keep at it, making very tiny adjustments, until you've got the stars as small as possible. This is very much a trial and error thing, and can be quite frustrating (welcome to the world of astrophotography), but keep at it and, as is the case with most things, with practice you'll get better. If you have an M and A switch on your lens (Manual and Autofocus), or something similar, then after each adjustment set it to A. This will lock the focus and stop it slipping, but remember that if you need to make another adjustment you'll need to switch it back to M, otherwise you won't be able to move the focus ring. If you don't have this switch, and you're having problems with the focus slipping (this can be the case with inexpensive zoom lenses), then a small blob of blu-tack conveniently placed will help to hold the focus ring in position, but be aware that this may leave a residue (there, you can't sue me now!)

Orion again, 50mm, f1.8, 5sec, ISO 3200 by Fred Agustin. Very dark skies I would assume :)

You may also find that the stars are slightly sausage shaped, which is caused by the apparent movement of the stars across the sky - this will depend upon the focal length you used and the shutter speed. There is something called The Rule of 600 which you can use as a guide: just divide 600 by the focal length you are using and this will give you the longest shutter speed you can use without getting star trails e.g. 50mm focal length = 600/50 = 12 seconds. Very useful.

You may want to target a constellation you are familiar with, in which case you'll need to use an appropriate focal length to get it all in the frame. You could end up with a portfolio of images of all the major constellations, or perhaps all those in the Zodiac - the possibilities are endless! Good luck, and don't get frustrated and give up - this hobby takes practice and perseverance.

I've reproduced throughout this blog a few images I've discovered on Flickr that were taken using this method, with appropriate credits. In the next blog, I'll cover the stacking of images to reduce the noise and enhance the signal, which should give you a result you can be even more proud of - so watch this space for Part Two :)

The Plough, or Big Dipper. 20mm, f2.0, 29sec, ISO 400 by Paul Richards

OK guys, have fun out there. Feel free to post any images you take using this technique (or any technique for that matter) to my Facebook page - there's a link at the top of this post. It would be good to see them, and at least then I'll know I'm not talking to myself here. :)

As always, may your skies be forever cloudless :)


Doug

M51 The Whirlpool Galaxy in Canes Venatici

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Messier 51 The Whirlpool Galaxy in Canes Venatici

The Whirlpool Galaxy (also known as Messier 51a, M51a, or NGC 5194) is an interacting grand-design spiral galaxy that is estimated to be 23 ± 4 million light-years from the Milky Way Galaxy in the constellation Canes Venatici. It is one of the most famous galaxies in the sky. The galaxy and its companion (NGC 5195) are easily observed by amateur astronomers, and the two galaxies may even be seen with binoculars. The Whirlpool Galaxy is also a popular target for professional astronomers, who study it to further understand galaxy structure (particularly structure associated with the spiral arms) and galaxy interactions. Wikipedia

This image was created using data from last year combined with data I captured in April 2012. It consists of 142 individual sub-frames, each of 60 seconds duration (the most I can get out of my EQ5 mount without star trails becoming a problem). The sub-frames - or subs - were stacked in Deep Sky Stacker (DSS), and the resultant tif file was processed in Photoshop CS5. For those of you already familiar with DSS, there's a vid on stacking multiple sessions on my Youtube channel here. For those of you not familiar with DSS, there's a (rather lengthy) vid on how to use it here :)

This is a relatively bright and easy target and is a good one to aim for once you've got the hang of using a scope and camera. Once this blog gets off the ground properly, I'll post a JargonBuster page, to give you an idea of what all the technical stuff means. I also hope to post a blog for each of the more popular targets that us amateurs like to aim at, giving you an idea of where it is and the best way to approach imaging the thing.

Promised blog on DSLR/Tripod imaging will be with you shortly.

May your skies be forever cloudless :)

Doug

So you want to do Astrophotography?

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It is now 19:30 (UK time) on Tuesday 19th June 2012. I say this because if you happen upon this blog tomorrow, you'll know why there is very little content :)

OK. If you want to get into Astrophotography, then apart from kit, like a camera (always useful), some sort of mount (preferably an equatorial mount - more on that later) and a computer with an image processing program installed, you will need:

1. Time, and lots of it
2. The ability to survive on very little sleep
3. Dogged determination
4. Patience of a saint, preferably a little bit more
5. Shed loads of enthusiasm
6. The ability to persevere under the most testing circumstances
7. A sense of humour
8. The ability to not take all this stuff seriously :)

If you've got all that, and you really, really want to do this, then I can offer a few tips and tricks, the benefit of my very limited experience, and a virtual shoulder to cry on when it all falls apart, as it will do - frequently.

The first bit of advice I will offer, and this is pretty boring guys but I make no apology, is to prepare yourself before you even think about pointing a camera at the heavens. By that I mean research the subject on the internet, read books, and then do some more research and read more books. When you think you've done enough, do some more research and read more books. Until I say stop ;) There's a good reason for offering that advice: If you don't know what you're doing and just jump in, you will fail and you'll give up - guaranteed. Astrophotography is an extremely steep learning curve - not just taking the images (the easy bit), but processing them in Photoshop or whatever (the hard bit). If you try doing all this without even the basic knowledge that you need, your results will be very disappointing and you'll think it's just you that can't do it - everybody else seems to be able to. And you'll give up and carry on watching the telly or something.

This is the very first astro image I ever took:

M45 The Pleiades aka The Seven Sisters  in Taurus

and this is the second:

M42 The Great Nebula in Orion

A bit blotchy, and not superb processing, but for first images they're not bad. Now I don't show these images to demonstrate how clever I am - far from it. The point is that by the time I came to take these images I had a reasonable idea of what I had to do and how to do it, because I had spent at least two months reading as much about this stuff as I could. There really are no short cuts guys - IMHO :) These images were taken with a Nikon D40, which I already had, and a second hand Skywatcher 200p and EQ5 mount that I purchased together on ebay for £200. I had to add motors to the mount so that I could do long exposures (these images are about 30 seconds) and that cost about £80. I still use this kit now, although I now use a second hand Nikon D70 (£99) which I modified myself (£0) :) So you don't need to spend a fortune on kit (although you may very well end up doing that) - hence BudgetAstro :)

Now take a gander at this stunning image:

Orion by Rogelio Bernal Andreo - Deep Sky Colors

Not bad eh? When I first saw Deep Sky Colors I was gobsmacked. I didn't know such images were possible, and Rogelio's website was a huge motivating factor in my decision to take up astrophotography - I urge you to pay it a visit (the link is in the caption above). This particular image is a mosaic of 32 individual frames, with a total exposure time of 28 hours, taken over several nights in October 2010. Rogelio will think nothing of driving for ten hours into the desert to find the darkest of dark skies to take his images, and having acquired the data, he will spend countless hours processing it - total dedication to his craft.  Now if I'm brutally honest with myself, I know that I will probably never take an image of such quality. Not because I don't have the ability (although that may very well be true), but because I do not possess that extraordinary level of  dedication. Oh, and he probably doesn't use budget kit - but that's another story ;)  The point here is setting expectations. You'll find plenty of stunning astro images on Flickr and other image sharing sites - I would suggest that you don't try to match them, at least not in the early stages of your astro imaging career, because you probably won't be able to. Use them for inspiration by all means, and for reference, but don't beat yourself up if your images aren't as good. The creators of those images have probably been doing it for years, and have acquired a great deal of knowledge and skill, and probably some decent kit, along the way. Apart from that, no matter how good you are, there will always be someone doing it better (not sure that applies to Rogelio though!)

I know a guy that is forever buying new golf clubs: new complete sets, new and better (and more expensive) drivers, the latest utility club - it goes on forever. He honestly believes that if he buys better and better clubs his game will improve, and it probably would if it wasn't for the fact that he can't play golf. He just isn't very good, and it doesn't matter how good his driver is, it will never go further than 100 yards. The same applies to astrophotography. I promote astrophotography on a budget, because that's what I do, but you may have more funds at your disposal. I would suggest that you don't go rushing out buying the best kit that you can afford at this stage, because you probably don't know what to do with it (I make that assumption because you're reading this blog :) ). As a result your images, taken with your expensive driver - sorry - telescope, probably won't be as good as mine, taken with kit that cost next to nothing (relatively speaking). You need to learn to crawl before you can walk before you can run, and I hope the stuff I put on this blog will go some way towards giving you the required knowledge. Mind you, I'm still very much a learner myself, and I've made many mistakes along the way, but if I can help you avoid the same mistakes, I'll have done my bit :)

One final point before you doze off: Astrophotography has a reputation for being a bottomless pit, and so it is. As you're experience grows, and your images improve, you'll always be able to find a bit of kit that will improve your images further. Unfortunately, they don't give this stuff away for nothing. My advice would be to keep the plastic well and truly hidden and to set yourself an upper limit above which you will not go - you don't want to end up re-mortgaging the house :)

OK, OK enough already! The next post will be about taking images with just a DSLR and a tripod, which you may already have - you won't need to do too much research for that :)

Cheers guys, and may your skies be forever cloudless :)

Doug