Astronomy 101: Tips & Tricks
  • Astrophotography
  • Add on Aug. 3, 2017, 2:45 p.m.
Tips and tricks on Astrophotography

Chapter 1

Chapter 2

Chapter 3

Chapter 4

Chapter 5

Chapter 6

Chapter 7

Chapter 8

Chapter 9

Chapter 10

 

 

 

Chapter 1

 



Astrophotography is a most rewarding hobby for many amateur astronomers. It is a wonderful way to capture and hold on to the beauty of the celestial objects we most admire, and provides us with a way to easily share them with friends, even when the telescope is not around.
It was once thought that astrophotography was something that only seasoned astronomers dare try. But, this is certainly not the case, and with the advent of digital cameras and eyepieces, astrophotography is becoming more accessible to more people all the time.
There are several types of astrophotography that vary in terms of difficulty and costs. Fortunately, some of the easiest kinds of astrophotography can be accomplished at the lowest cost. So, you don

 

 

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Chapter 2

The basic technique for video astrophotography is as follows: Point your telescope at the object you wish to photograph. If you are using a motorized equatorial mount in a polar aligned configuration then subsequent tracking of the object (e.g., the moon) will be handled automatically. If your mount is not motorized, or if you are using an alt-azimuth mounted telescope like a SkyWatcher Dobsonian, then you will need to update the position of your telescope manually as the images are being recorded. This makes your task a bit tougher to accomplish, but it can most certainly be done.
For simplicity, we’ll assume that you are using a motorized equatorial mount. Once you are pointed at your object, remove the eyepiece from the telescope focuser and replace it with your digital eyepiece. Now adjust focus and watch the monitor of your laptop or other video device that your camera is connected to.

Venus Transit photo by Peter Roth, Canada. Taken with SK1025AZ3.

 

When you have achieved sharp focus, you can just watch and enjoy, or save the images on your computer. If you save your images you can later use any of a number of freeware programs to stack and process them. Or you can purchase more sophisticated program commercially for more functions and better results.

A digital eyepiece along with your laptop computer and virtually any of our telescopes is a great combination at star parties. With this equipment many people can simultaneously view what the telescope is seeing. It is a great way to share your enjoyment of astronomy with others, but without risking your valuable eyepieces - which can take quite a beating at public outings! Moon photos by Famille Dinant, Switzerland. Taken with 70mm refractor.

Moon photo by Mengoli Giorgio, Italy. Taken with 80ED refractor.

 

 

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Chapter 3

 

There is one exception to this general rule, however. That is prime focus astrophotography done with a video camera, such as digital eyepiece. With a digital eyepiece in place of a regular eyepiece you can take incredible images of the Moon, Sun (with appropriate filter) and planets at the prime focus of your telescope. In fact, you can even do this type of astrophotography with our SkyWatcher Dobsonians and other alt-azimuth mounted telescopes.
Digital Eyepieces can be used with virtually any type of telescope because they take pictures of very short duration and thereby avoid trailing. Consequently, they work exceptionally well on the bright objects like the moon, sun and planets. But for this very same reason, they do not work well on dim, deep space objects, like nebulae.

That is the domain of long-exposure prime focus astrophotography, which is discussed a bit later (see next page).


Imaging of dim nebulae requires long exposures with sensitive cameras and highly accurate tracking.Some of our customers have taken outstanding images with video cameras and eyepieces attached to our Maksutov telescopes. The Maksutov design is particularly well suited for video imaging due to its longer inherent focal length and excellent high contrast optics. The Maks are also very portable and that makes travel and setup a lot easier too.

 

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Chapter 4

The basic technique for video astrophotography is as follows: Point your telescope at the object you wish to photograph. If you are using a motorized equatorial mount in a polar aligned configuration then subsequent tracking of the object (e.g., the moon) will be handled automatically. If your mount is not motorized, or if you are using an alt-azimuth mounted telescope like a SkyWatcher Dobsonian, then you will need to update the position of your telescope manually as the images are being recorded. This makes your task a bit tougher to accomplish, but it can most certainly be done.
For simplicity, we’ll assume that you are using a motorized equatorial mount. Once you are pointed at your object, remove the eyepiece from the telescope focuser and replace it with your digital eyepiece. Now adjust focus and watch the monitor of your laptop or other video device that your camera is connected to.

When you have achieved sharp focus, you can just watch and enjoy, or save the images on your computer.

enus Transit photo by Peter Roth, Canada. Taken with SK1025AZ3.

 

If you save your images you can later use any of a number of freeware programs to stack and process them. Or you can purchase more sophisticated program commercially for more functions and better results.

A digital eyepiece along with your laptop computer and virtually any of our telescopes is a great combination at star parties. With this equipment many people can simultaneously view what the telescope is seeing. It is a great way to share your enjoyment of astronomy with others, but without risking your valuable eyepieces - which can take quite a beating at public outings!

Moon photos by Famille Dinant, Switzerland. Taken with 70mm refractor.

 

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Chapter 5

Long-Exposure Prime Focus Astrophotography
This is considered by many to represent the highest level one can achieve in astrophotography. The allure is that almost any deep sky object can be photographed, and when done well, yields astonishing results. If you pause for a moment and think about the most amazing astrophotos you have ever seen, you will almost certainly be envisioning long-exposure prime focus images. Perhaps the most famous of all is the Hubble Deep Field image, a photograph taken at the prime focus position of the Hubble Space Telescope that had a total exposure of over 100 hours!
Sky-Watcher Telescopes is very pleased to offer a variety of premium mounts and telescopes that have enabled many people to enjoy great success in photographing nebulae, star clusters and galaxies using prime focus techniques. We offer the hugely popular EQ6 and HEQ5 SynScan mounts in both Standard and Pro Series. These high precision computerized mounts can automatically point your telescope to over 14,000 objects in the standard data base, and when connected to a computer with suitable planetarium software they can point at virtually any known object.
For astrophotography the SynScan mounts can’t be beaten. They are capable of tracking the sky with errors limited to a few millionths of a circle. Moreover, they are equipped with built-in autoguider ports and have user programmable backlash compensation that adds even more precision to the tracking process.
In fact, the EQ6 has been described as “The best value in all of astronomy - bar none”. It has earned this reputation due to it’s enormous payload capacity, it’s high precision performance, and it’s amazingly affordable price. Its nearest competition costs more than double the price, yet has no better tracking performance and a lighter payload capacity.
If you need further convincing as to the capability of these mounts then just enjoy the accompanying astrophotos, all taken with the EQ6 or HEQ5 SynScan mounts. Using these mounts and readily available software, multiple images are done in seconds each with state-of-the-art CCD cameras. And then the images are processed allowing incredible photos which were unheard of just a few years ago, even with large observatory telescopes.



 

Eagle Omega photo by Dr. Brady Johnson and Jay Ouellet, Canada. Taken with EQ6 Pro mount.

Rosette Nebula photo by Dr. Brady Johnson and Jay Ouellet, Canada. Taken with EQ6 Pro mount.

M8 M20 photo by Dr. Brady Johnson and Jay Ouellet, Canada. Taken with EQ6 Pro mount.

NGC 7000 photo by Dr. Brady Johnson and Jay Ouellet, Canada. Taken with EQ6 Pro mount.

Gamma Cygni photo by Dr. Brady Johnson and Jay Ouellet, Canada. Taken with EQ6 Pro mount.

 

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Chapter 6

Andromeda photo by Frédéric Caron, Canada. Taken with 80ED refractor.

High precision tracking is just one side of the coin when it comes to taking high quality astrophotos. The other side is optics. Sky-Watcher is pleased to offer a wide variety of telescopes that are highly capable for long-exposure prime focus imaging, starting with our premium ED refractors.
Introduced in early 2005, our Sky-Watcher 80ED refractor has been a highly popular choice with astrophotographers. It offers a relatively fast focal ratio of f/7.5 coupled with a 600 mm focal length to provide a very capable rich-field imaging telescope. It is ideally suited to digital SLRs such as the Canon Rebel, 20D and new 20Da.
The 80ED boasts sharp optics with extremely low secondary colour. This yields sharp, high contrast images that will take your breath away. Our 100ED refractor can also be used for astrophotography. It has the same excellent optics as its little brother along with a longer focal length for higher effective magnification. At f/9 it is a bit slow for film cameras, but it is well suited to digital SLRs and more sensitive astronomical cameras such as those from Santa Barbara Instruments Group (SBIG) and Starlight Express.
Note, the HEQ5 and EQ6 Synscan mounts are plug and play ready for autoguiding with SBIG imaging cameras and autoguiders using the standard cable supplied with the SBIG product. You can also autoguide them with webcams using software that is freely available on the internet.
In addition to our premium refractors, almost any one of our Newtonian and Maksutov telescopes can be used for prime focus astrophotography. From the SK15075 OTA right up to the SK25012 10” Newtonian, your t-ring equipped camera can be directly

California Nebula photo by Frédéric Caron, Canada. Taken with 80ED refractor.

M45 photo by Frédéric Caron, Canada. Taken with 80ED refractor.

 

connected to the focuser for a solid attachment. Add a guide scope or autoguider and you are equipped with an awesome platform for PFA.

 

 

 

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Chapter 7

Young Male Elephant by William Ronald, Canada. Taken with SK 804AZ3.

You may notice that we have not recommended our standard short focus refractors to this point. These achromat designs can be used for PFA but will not provide the same high quality results as our premium ED refractors or our Newtonian reflectors. On the other hand, even our achromat refractor designs work well for daytime photography, making them a great low price solution for telephoto nature photography.
The difference is due to the design of a standard achromat refractor. Such designs, regardless of who makes them, are incapable of bringing all colours of the visible spectrum to a common point of focus. For visual use, this residual or secondary color that achromats produce can be quite effectively suppressed by modern filters, like the Baader Semi-Apo filter.
But for photography, the filters are less effective. The problem is that while they can sufficiently suppress secondary colour where our eye is concerned, they do not suppress it enough where a highly sensitive film emulsion or digital sensor is concerned. Consequently, images taken with achromat refractors will suffer from chromatic aberration, seen as large purplish halos around bright stars. There is simply no avoiding this with the achromat design.

There is one exception to this rule, however. More advanced astrophotographers can get excellent performance from achromat refractors by using an advanced technique called tri-colour imaging. In tri-colour imaging, sensitive astronomical cameras are used with highly specialized filters that pass only a narrow region of the visible spectrum. Since only one colour is being passed by a given filter, it is possible to achieve a very sharp focus, even with an achromat refractor. So, three filters are used: One that passes red light, one that passes green light, and one that passes blue light. The telescope is refocused each time a filter is changed, and when finished, the three images are combined to produce the final colour image.

Rosette Nebula by Claude Baril, Canada. Taken with SK 1025AZ3.

So the best choice for astrophotography is either an ED refractor, which is designed to bring the visible spectrum to a sharper focus, or a Newtonian reflector, which, due to its design, is immune to chromatic aberration.

 

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Chapter 8

What sorts of images can you expect to get with SkyWatcher equipment? Well, we can’t really answer that directly because a lot of human factors go into the making of an exceptional astrophoto. But what we can do is show you results that our customers are submitting, and leave you with the following thought: If they can do it, why not you?
 

Lotus by David Shen, Canada. Taken with SK1025AZ3.

Sun Spots by Peter Roth, Canada. Taken with SK909EQ2.

Moon photo by Bruno Nolf, Belgium. Taken with Sky-Watcher 150mm reflector.

Orion Nebula by , Canada. Taken with SK1025.

Total Lunar Eclipse Sequence photo by Francisco A. Rodríguez Ramírez, South Africa. Taken with SK1025AZ3.

 

Saturn photo by Riccardo Cosenza, Italy. Taken with Sky-Watcher 130mm reflector on EQ5 mount.

 

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Chapter 9

Photographing a solar eclipse is not difficult, but you must be careful because the sun can quickly cause eye-injury and damage to your equipment. Even if only a small slice of the sun is showing, a correct solar filter in front of the lens or a projection methods must be used. The only time that the sun can be safely viewed without protection is during "totality"; even the ring of an annular eclipse can be unsafe.
The sun and moon are each about one half degree in apparent diameter so their images are very small with a normal 50mm SLR lens or a "point and shoot" camera. Filling the small dimension of a 35mm slide requires a focal length of almost 3000mm. Short-tube refractors with their focal ratios of f5 to f7 and fixed focal lengths of 400 to 500mm are very good for full-sphere shots, and to get more detail their focal lengths can be increased using a teleconverter (TC). For example, with a refractor acting as a 500mm f5 lens, a 1.4x TC will make it 700mm f7.1, a 2x TC will make it 1000mm f10, etc. The exposure is controlled by varying the shutter speed. To reduce vibrations, the telescope and camera should be mounted on a solid tripod with the weight centred as much as possible. A cable release should be used, the camera mirror may be locked up and under really bad conditions anti-vibration pads can be placed under the tripod feet. Finally, unless a tracking mount is used, the exposure cannot be long. For example, about one second is the maximum exposure length for a focal length of 800mm because any longer will result in image trailing.
Lunar eclipses and the partial phases of solar eclipses are easy to photograph because they take place over hours, but totality lasts for only minutes so organization is needed.
 

 

 

So many things can be photographed in such a very short time! There are "Bailey's beads" and "diamond rings" at 2nd and 3rd contacts and the chromosphere, prominences and the corona during totality. At the same time, many other interesting things are happening such as temperature changes, shadow bands, approaching and departing shadows, reactions of local wildlife and other people, and the feeling of awe that can leave you just standing and looking, or laughing, or cheering. The most important thing is to observe and experience totality. Photography should be only a small part of it and every effort should be to limit the time spent fiddling with a camera.
The following example is a fairly ambitious shooting schedule, like the one used to take the eclipse pictures seen in these pages, with ISO 400 film, a manual focus SLR, a 400mm short-tube refractor (without the finder scope) and a 2x TC to give a final focal length of 800mm. Photograph the partial phases using a solar filter or a projection method. If necessary, change the film so that it doesn't run out during totality. At second contact, having recently focussed, remove the filter and, without looking through the camera's finder, shoot Bailey's beads and the diamond ring. If the partial phases were shot through a solar filter, such as mylar which gives a blue image, refocus on the red prominences. Now, shoot the chromosphere and prominences, and a corona series within about a minute. The corona series, running from your fastest shutter speed down to one second, can be manipulated and combined digitally at a later date. Finally, after presetting the camera speed for the 3rd contact diamond ring, "look and experience" until it is time to release the shutter for that gem of a shot!

Diamond Ring photos by William Ronald, Canada. Taken with SK 804AZ3.

 

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Chapter 10

If the mount is not tracking, quickly centre the image just before 3rd contact. Don't forget to put your filter back on after the 3rd contact diamond ring and Bailey's beads, then finish taking the partial phases.
The key to successful eclipse photography is careful planning and good technique. In order to decide what events you want to capture, and what exposure times you should use, consult current eclipse reference books and webpages. Before the eclipse, practice on the Moon or the filtered (or projected) Sun, with your particular equipment and the film that you have chosen. You can't test all of the exposures but you will become familiar with your setup. Finally use a prepared shooting script which includes accurate event times for your viewing location, shutter speeds and when solar filters should be on or off. If possible have someone calling out the event times for you, but if you don't have that luxury, you can prepare an audio tape timed to give you the warnings.
Good luck and clear skies!

 

Corona photos taken with SK 705AZ3, other Solar Eclipse photos taken with SK 1025AZ3, both by Francisco A. Rodríguez Ramirez, Spain.

 

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