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CHEAP AND EASY ASTROPHOTOGRAPHY
with your own camera and a star tracker
From £260
This picture was taken with 300mm camera lens on a small star tracking mount (although i did use an astro camera not a dslr)
If the earth would just stop spinning then Astrophotography would be easy. We could point a great big light bucket dobsonian up at the sky, take a twenty minute exposure and wind up with a beautiful, crisp picture of deep space. Unfortunately we need a motorised mount to hold our telescope still for the full duration of the exposure while the earth spins beneath it.
When you are at high magnification holding the scope "still" is tough... but when you don't zoom in much its a lot easier. That in turn means we don't have to drop thousands of pounds on an incredibly accurate mount. Instead we can use one of these relatively cheap earth de-rotation device...
I haven't used one of these mini versions but they look great and will be fine up to 200mm focal length
What blow me away with these mounts is that they track as accurately as mounts that cost twice as much. Note this version comes with all the accessories you need although if you're doing wide angle stuff with lenses then you might also want a ball head
All we're trying to do is spin our camera in the opposite direction to how the earth is spinning.
Any sturdy camera tripod will do
but if you don't have one there are these...
My regular travel rig set up
I often use my canon 6d and the Samyang 135mm lens with my Sky Watcher Star Adventurer but on this occasion I pushed the set up with a 50year old 180mm APO Telyt lens and the ZWO asi294mc camera to reveal the reflection nebula M45 (aka Seven Sisters)
The best trackers in my opinion are the Skywatcher Star Adventures. The cheapest, mini version of this device is good although above I recommend its big brother with the pro pack because the extras give you more flexibility and the adjustable wedge makes aligning the mount to the rotation of the earth easier and more accurate. There are other similar astrophotography travel mounts but the Star Adventurer is the only one I've properly tested. Its very good. I've even stuck a little guide scope on it and successfully taken 30minute long subs. It is comfortably accurate to 2 arc seconds whilst guiding.
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How to do it
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Line the mount up to the rotation of the earth using inbuilt polar scope
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Stick the camera on a ball head and then stick them both on the tracking mount.
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Use the ball head to point the camera at the target
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Start taking pictures.
Here is a link to a good and cheap ball head on Amazon
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Great astrophotography lenses
50mm
I love my Sigma f1.4 50mm art lens. It is so fast and sharp it can catch Orion nebula setting through the trees with just a ten second exposure. Perfect for timelapse...
135mm
Amoungst us nerds the Samyang f2 135mm manual lens is legendary.
250mm
Above 250mm focal length the sharpest images can be gotten with small telescopes rather than lenses.
Williams Optics REDCAT 51
Lenses are good for catching lots of photons because they are very fast but the price you pay is that the light has to pass through their 9 or 10 or even more glass elements. the redcat below is made of just four glass elements which makes the image sharper.
The shot above was taken from my roof in London with a little Tak FS60cb. The little Redcat I'm recommending has almost exactly the same focal length as my 60mm diameter Tak and in terms of sharpness the two scopes are very similar. I picked up my tak cheap second hand and paired it with a no longer produced and relatively cheap Borg x0.7 super reducer. New the Tak FS60cb with it's dedicated reducer costs $1400. It is a great scope but not budgety hence my recommending the redcat! FYI I shot this from Light polluted London with expensive narrowband light pollution filters and a cooled mono astrocamera. The cooled astrocamera will eat up power so I'm not recommending it for a travel set up.
Sky Watcher 72ED PRO
350mm
The skywatcher 72 ed with focal reducer is as big a scope as I would recommend with the Star Adventurer mount. Both its size and focal length are right on the limit of what this travel mount can handle. (If you are very good technically you might want to consider pairing this scope with the Sky Watcher AZ-GTI goto mount. Essentially this would make the ultimate travel rig... but its not easy to set up or operate.
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What Camera do I need?
The cheapest option is to use your own DSLR. A DSLR is good for shooting Galaxies, Star Clusters, and reflection nebula. Unfortunately a DSLR is not good at shooting deep red clouds of hydrogen like the clouds that make up most of the Great Nebula of Orion unless you get it modified. Modification removes the internal ir cut filter which blocks the deep red glow from the nebula. You can modify a DSLR yourself. Gary Honis has instructions here . Or for a bit over £100 you can get someone else to do it. In the UK I recommend Astronomiser.
Alternatively you can buy a dedicated astrocamera...
ZWO ASI294MC
ZWO ASI294MC PRO COOLED
If you want the ultimate astrocamera for starting out I recommend ZWO's ASI294MC. this camera is so sensitive I use it my videos to show people what they can expect to see through the eyepiece. The 294 excels at shortish exposures (0-30secs) because of its incredibly high sensitivity and incredibly low read noise. It is a great match for a travel rig particularly if you are shooting at over 200mm focal length because this is where shorter exposures really help to negate guiding inaccuracies in the star adventurer travel mount. It also is very useful having a camera so sensitive that you can clearly see your target when you are lining the shot up and focusing. And as an added bonus its one of the best camera's there is for photographing the moon and its not to shabby on planetary astrophotography either! The downside is that you will need a laptop to control it. That could be a problem if you are in the middle of nowhere. Incidentally Deddy Dayag (who appears in the youtube video) uses the cooled pro version of this camera with his huge 11ich SCT . The cooled version reduces the camera's dark current making it good at longer exposures too. The cooled version also needs a12v DC Power supply... again not the best thing for a travel rig but if you are serious and you want the cooled version then you'll need to invest in a powerful and light weight lithium battery .
You will need a UV/IR cut filter like this one to image with the astrocameras
This extreme light pollution filter allows me to image emission nebula from London. It works particularly well with longer exposures using a cooled astrocamera.
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