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How to do Fast Astrophotography, 10 of My Secrets!

Here are 10 of my secrets to the firehose of astrophotography I publish!

I’m a very active astrophotographer (see my Instagram for proof). People often say to me “How do you do so many astrophotos?” and I can’t give them a single answer, so I decided to write this article. I asked prolific solar astronomer Paul Stewart the same question and he replied without hesitation: “If the sun is out, I’ll image it.

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I can’t say I’m as dedicated as Paul, and many a perfect night has been lost to sleep, beer, or a good rock show, but there are several things I do that keeps me bombarding my friends and family with endless Facebook posts of my photos of space. I’m almost certain they’ve muted me by now.

Of course, different types of astrophotography are faster than others. The sun can be imaged in seconds and planets in minutes, though a good result can take an hour or more of processing. Night sky photography also returns results in minutes, but deep space takes, well, as long as you’d like to sacrifice to the timelords. Here are 10 of my secrets to my firehose of astrophotography.

1. Fast optics


Celestron’s incredible 11″ RASA is an example of an F2 telescope designed for fast exposures.

Obviously having an F/2 Hyperstar lens, dedicated astrograph telescope, or L-series wide aperture DSLR lens is literally going to speed up your exposure time by orders of magnitude. This is only one way, though, and buying your way to better photos, while fun, is not sustainable for most people.

Such fast optics however, really cut down a night’s work to a few hours. Or a week’s work to a single night. If you can afford the glass, why not? The time saved is a real justification for the cost, depending on what your time is worth to you.

2. Shooting in colour

The ATIK 314 is one of many colour CCD cameras available. The ZWO range of high speed colour CMOS cameras are also good.

I’ve written here before about the superiority of monochrome chips and their unrivalled sensitivity and detail compared to colour. Then I went away and happily kept imaging with my colour CCD!

For deep space astrophotography, getting at least 3 and sometimes 4 or more series’ of exposures in each different filter (e.g. Red, Green, Blue & Hydrogen Alpha) is hugely inefficient. It means you’ll almost never get a decent stacked astrophoto in a single night. This is the one true benefit of shooting in colour, if you can sacrifice that bump in quality mono will give you. If you do shoot in mono, settling for a bi-colour image using only two filters is a good compromise.

3. Versatile setup

It’s natural to want to specialise. But most telescopes and cameras are capable of a wide variety of focal lengths with different reducers, lenses, multipliers (Barlows & Powermates) and camera chip sizes. Having a DSLR for nightscapes in your toolkit as well as a telescope means you can try a whole variety of different methods and a single target may be photographed in several different ways. My current rig with adapters and lenses offers about 6 different fields of view with the one telescope, DSLR, and mount. Check to see what adapters, magnifiers and reducers yours supports – they are much cheaper than everything else.

Check out my C9.25″ with 2 separate image trains! One for planets, and one for high-speed F/2 Hyperstar deep-space imaging.

The author with his C9.25" with 2 separate image trains! One for planets, and one for highspeed F2 hyperstar deep space imaging.

4. Permanent setup

It goes without saying that getting your own little observatory setup will increase your output immeasurably, but it’s no panacea to quicker astrophotos. Before mine, I was always making the best of the clear nights, but having everything set up and ready to roll can shave an hour or more off your setup and pulldown time, and may simply motivate you to get out and use your equipment more. At some point the amount of money you’ve spent on this pursuit really does justify making sure you use it, and a personal observatory is a logical next step.

The Sky Shed Pod, from Canada, is a relatively cheap prefab kit observatory with a small footprint, perfect for backyard astronomers.

The Sky Shed Pod from Canada, is a relatively cheap prefab kit observatory with a small footprint, perfect for backyard astronomers.
My Sky Shed Pod

5. Consistent workflow & practice

It’s common when setting up at a star party to completely screw up the polar alignment due to the sheer unfamiliarity of the process away from your usual location. Knowing your steps to align your mount and get it guiding, setting up your DSLR in the dark, getting your guiding configured quickly, etc will help you get exposures quicker. Try to introduce new equipment one piece at a time and be ready to waste a night here and there just fiddling and practicing and working out the kinks in your process and gear. After a while, you’ll be playing it all like a piano. I know it sounds obvious but wasting good imaging time because windows needs a reboot is something that happens to everyone – even the professionals.

This image of the Lagoon Nebula, by the author, was created from a mere 9 exposures for a total of 27 minutes.
Photo: Dylan O’Donnell

6. Just enough exposures

There is a bit of mythology about stacking and what it actually does. Some people have the idea that stacking ridiculous amounts of exposures will magically make the image proportionately better. It doesn’t. It has two main goals.

Firstly, noise removal. That’s it. That’s literally all stacking does.

The other one is just having enough exposures that you can actually throw away the less perfect ones and keep the best. Otherwise known as “lucky imaging”. Knowing this, you can aim for around 30 good exposures (of whatever length you’re using). If you get 40, great! If you have more than 40 good exposures, you’re wasting time for little tangible benefit. Nobody on Instagram is going to notice, trust me.

SNR Stacking
Shown here in this graph (source: PixInsight.com), is the theoretical signal-to-noise ratio improvement as more images are stacked. As you can see, exposures beyond 40 offer diminishing returns. The image above this section (Lagoon Nebula) is a particularly bright target and was imaged with only 9 frames for a total of 27 minutes, without particularly fast optics.

 

7. Diversity of subjects & techniques

The great thing about photographing space is — there’s so much of it! At any given time there are dozens of easy targets overhead, and then an insane amount of difficult ones.

Solar disc, flares, and spots, lunar craters, planets, galaxies, nebulae, clusters, conjunctions, eclipses, star trails, Milky Way. The list is endless! Not to mention the exotic ones: aurorae, sprites, the ISS, fireballs!

We all have a favourite and a least favourite (globular clusters – YAWN), but if you open your repertoire to the possibilities you’ll find a vast array of celestial wonders and you won’t be a one trick pony” either. Adding to this, any given target can be imaged a variety of different ways. Colour, Mono, Bi-colour, LRGB, Hubble Palette, 3D … There’s no shortage of variety.

Below is my ISS transit of the moon with full colour processing, of which tutorials for both available here and here!

ISS-TRANSIT-2048
Photo: Dylan O’Donnell

8. Planning

I can see your eyes glazing already. Boring. Who am I? Your parents? Telling you to plan your shoots!?

I know, I know. I spent a long time just setting up then looking at my software and seeing what’s up. I’m coming around to knowing ahead of time what I’d like to get in any particular season, then ensuring it’s well positioned and timed so the time I spend imaging works around the rest of my life’s timetable. Software like Photopills, Stellarium, and Sky Guide for iOS are all great programs for this. Have a think about how you are going to frame the shot before you even set up.

Sky Guide for iOS isn’t too sophisticated, but using photography from the Photopic Sky Survey – it sure is pretty!

SkyGuide for iOS isn't too sophisticated, but using photography from the Photopic Sky Survey - it sure is pretty!

9. Processing is king

All astrophotos are a result of processing. Yes, even yours – hipster film nerds from the 1980’s. Don’t get me started.

It’s true these days that software is getting so good, and so advanced, that sometimes it takes just as long to process the stack of images as it does to get the light frames in the first place. Darks, flats, bias, noise reduction, sharpening, colour calibration, star reduction, etc., these should all be in your toolkit. Not to simply enhance a poor image (though that’s possible too), but to reveal the good image of space that is sitting in there under all that star bloat, light pollution, noise, and optical and digital aberration.

Processing can compensate for not having enough frames, or not being in the ideal location. As long as you keep it honest. Don’t just paste the starship enterprise onto the setting sun and share it with a straight face. Keep it real.

Below is my image of the Cat’s Paw Nebula, before and after processing in PixInsight and Photoshop.

Author's image of the Cat's Paw Nebula before and after processing in PixInsight & Photoshop.
Photo: Dylan O’Donnell

10. Sharing is caring

sharesArt is never finished, it is only abandoned, so they say.

I know too many astrophotographers with amazing work and amazing gear whose photos never see the light of day beyond technical forums or a close circle of astro friends. Us astrophotographers can be very critical of each other’s work (in a good way), which also leads to a heightened sense of self criticism. Try to let that go and get those images off your hard drive and in front of the eyeballs of the general public, they love what we do! The positive feedback will motivate you to keep going, and the critical feedback will motivate you to get better – it’s a win/win situation. I, for one, need less celebrity and politics in my news feed, and more sharing and appreciation of science the natural world we all have direct access to!

Clear skies, and keep shooting!

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About the author

Dylan O'Donnell

Dylan O’Donnell is an Australian web developer, Director of DNA Digital and zen10 Australia and public science communicator. He has a Masters of Information Technology and his astrophotography been featured by NASA and ESA among others. He is also a member of Team Celestron where he also contributes. To date, two of his images have been selected for NASA Astronomy Photo of the Day (APOD).

See more of Dylan’s work on his website.

3 Comments

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  • Excellent article Dylan. I like the idea of speed in AP. Probably when I retire I’ have the time and patients to spend hour shooting the night sky, hi on something and not a care in the world 🙂
    Right now in my 30’s with a full-time job and a wife I like to sleep next too at night I want to maximize the results of my rare AP outings.
    I’m currently using an f5 Newt. with a DSLR camera.
    Do you think that upgrading to a fast wide field Refractor and maybe color CCD would speed things up for me? Or is aperture as important as f ratio for fast AP ?
    Should I go for the CCD first to get the sensitivity ? and then upgrade to and SCT in the far future…
    Sorry for ranting, amazing work by the way.

    • Hi Tudor! I’m glad you enjoyed the article 🙂

      I’m not sure what you mean about aperture vs F-ratio .. they are inextricably linked. (The F-number is ratio between the physical aperture and the focal length.). But obviously a lower f-number is ideal for shorter exposures. A DSLR is probably faster than a CCD camera as is essentially stretches the data “in-camera” using ISO to bring the signal (and noise) up. CCDs main advantage is cooling for less noise, and a higher dynamic range. If you want speed, you might like to consider the new generation of high-speed CMOS cameras like the ZWO1600 or others in that range, that are great for planetary but also good for deep space objects with shorter exposure time required.

      I hope this helps!

      d

      • Thanks for the fast reply Dylan.
        Yes that clears things up.
        Still a newb when it comes to lenses/photography. What makes the SCT particularly fast is the combination of the aperture and focal lenght (with hyperstar). So CMOS is the way to go for speed when it comes to sensors.

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