Autoguiding is a technique used in long-exposure astrophotography to accurately track celestial bodies, compensating for the Earth’s rotation. This approach ensures that stars appear as perfect points of light, rather than streaks or trails, even in very long exposures. By mastering autoguiding, you can capture sharper, clearer images that reveal the intricate details of our universe.
In this comprehensive guide, we will explain the science behind autoguiding, delve into its many benefits, and walk you through setting up and using an autoguiding system. So, whether you’re a seasoned stargazer or an astrophotography novice, this article aims to shed light on how autoguiding can enhance your celestial captures.
What is Autoguiding?
As the Earth spins on its axis, the stars appear to move across the sky. This can create beautiful star trails in photographs but can be a challenge when trying to capture detailed images of specific celestial objects. Autoguiding, a technique widely used in astrophotography, helps combat this issue.
Understanding Autoguiding
At its core, autoguiding is a system that allows your telescope to accurately follow celestial objects as they move across the sky, a process known as “tracking”. While all motorized telescope mounts provide a basic level of tracking, it’s often not precise enough for long-exposure astrophotography.
Autoguiding systems take tracking to the next level by using a secondary, smaller telescope (known as a guide scope) and a specialized camera (a guide camera). The guide camera continually takes short exposure shots of a chosen guide star and relays this information to the mount.
Camera: Canon T3i (stock / unmodified / unmodded DSLR)
Telescope: Explore Scientific ED80 f/6.0 Apochromatic Refractor (with ES field flattener)
Mount: Orion Sirius EQ-G
Guide scope: Svbony 50mm f/4.0 Guide Scope
Guide camera: Orion StarShoot AutoGuider
Bortle Class 6 (Charlottesville, VA)
The Science Behind Autoguiding
Autoguiding’s prowess comes from its real-time adjustments. By continually monitoring a guide star, the autoguiding system can detect even the smallest movement caused by imperfect tracking or atmospheric disturbance. The system then sends corrections to the telescope’s mount, adjusting its position to keep the guide star – and therefore your main target – perfectly in place. This meticulous tracking provides the stability needed for long-exposure astrophotography, ensuring your images are as crisp and detailed as possible.
Components of an Autoguiding System
An autoguiding system consists of three main components:
- Guide Scope: A small secondary telescope that rides along with your main telescope. Its job is to keep an eye on a particular guide star.
- Guide Camera: Attached to the guide scope, this camera takes continuous short-exposure shots of the guide star.
- Autoguiding Software: This software analyzes the guide star’s position in each frame and sends any necessary corrections to the mount.
Autoguiding, with its careful calibration and real-time corrections, can significantly enhance the quality of your astrophotography. It’s a worthwhile investment for anyone looking to take their celestial captures to the next level.
Benefits of Autoguiding in Astrophotography
Autoguiding can seem like an overwhelming concept at first, especially when you’re just starting your astrophotography journey. However, the benefits of mastering this technique far outweigh the initial learning curve.
Improved Image Quality
One of the main advantages of autoguiding is the noticeable improvement in image quality. By providing precise tracking, autoguiding eliminates the ‘star trailing’ effect in long-exposure images. It enables you to capture sharp, detailed photos that truly showcase the mesmerizing beauty of the cosmos.
Compensation for Gear Imperfections
Even the highest-quality telescope mounts aren’t perfect. Small errors known as ‘periodic errors’ can occur in the gears, which can affect tracking accuracy. Autoguiding compensates for these imperfections, constantly adjusting for any small movements to keep your target object centered.
Efficiency in Capturing Long-Exposure Shots
Without autoguiding, you may find yourself frequently adjusting and realigning your telescope to keep your target object in view, which can be especially tedious during long photography sessions. An autoguiding system automates this process, allowing you to capture long-exposure shots more efficiently. This makes autoguiding particularly important for deep sky imaging.
Autoguiding doesn’t just enhance your astrophotography skills; it also elevates the entire stargazing experience. It allows you to focus more on exploring the universe and less on constantly tweaking your equipment.
Setting Up Your Autoguiding System
Ready to dive into autoguiding? The first step is to set up your autoguiding system. This involves choosing the right equipment, connecting everything, and getting your settings just right.
Choosing the Right Guide Scope and Camera
Your guide scope and camera are crucial parts of your autoguiding system. The guide scope should be sturdy enough to hold the guide camera but light enough not to overburden your main telescope’s mount. When choosing a guide camera, look for one that’s sensitive enough to detect the guide star’s motion. A monochrome camera is a good option, as they’re typically more sensitive than their color counterparts.
Five guide scopes you might want to consider
| Name | Estimated Price | Focal Length | Aperture | Features |
|---|---|---|---|---|
| Meoptex 50mm Mini Guide Scope | $75 | 190mm | 50mm | Cheapest option, works with scopes up to 800mm focal length |
| Orion 50mm Mini Guide Scope | $99 | 162mm | 50mm | Affordable option, works with scopes up to 1000mm focal length, includes dovetail base |
| Starwave 50mm Guide Scope | $129 | 242mm | 50mm | Solid option, works with scopes up to 1200mm focal length, includes mounting rings and dovetail bar |
| Orion 60mm Guide Scope | $169 | 240mm | 60mm | Higher quality option, works with scopes up to 1500mm focal length, includes mounting rings and dovetail bar |
| Sky-Watcher EVOGuide 50ED Guide Scope | $349 | 242mm | 50mm | Premium option, doublet guide scope with FPL-53 glass, can also be used as a main imaging scope for widefield astroscapes |
As for guide cameras, here are some options to consider:
| Name | Price | Sensor Size | Pixel Size | Features |
|---|---|---|---|---|
| ASI120MM Mini Guide Camera or QHY 5L-II (equivalent) | $149 (ZWO) or $159 (QHY) | 1/3″ CMOS (4.8×3.6 mm) | 3.75 microns | Affordable option, good for short focal length guide scopes, can also be used for lunar and planetary imaging |
| ASI290MM Mini Guide Camera or QHY 5-III-290 (equivalent) | $299 (ZWO) or $329 (QHY) | 1/2.8″ CMOS (5.6×3.2 mm) | 2.9 microns | Higher quality option, good for longer focal length guide scopes, can also be used for lunar and planetary imaging |
| ASI178MM Mini Guide Camera or QHY 5-III-178 (equivalent) | $349 (ZWO) or $369 (QHY) | 1/1.8″ CMOS (7.4×5 mm) | 2.4 microns | Highest quality option, good for longer focal length guide scopes, can also be used for lunar and planetary imaging |
Connecting and Configuring Your Equipment
Once you’ve chosen your guide scope and camera, you’ll need to mount the guide scope to your main telescope and connect the guide camera to your computer. Your autoguiding software will use the images from the guide camera to track the guide star and send corrections to your mount.
With everything connected, you’ll need to configure your autoguiding software. This will involve selecting the right guide star, setting the exposure time for the guide camera, and adjusting the correction settings for your mount. Remember, each setup will require a bit of fine-tuning, so don’t be disheartened if you don’t get it perfect right away.
Setting up an autoguiding system can seem like a daunting task, but it’s a worthwhile investment. With some practice and patience, you’ll soon be on your way to capturing better, sharper, and more detailed astrophotography images.
How to Use an Autoguiding System
Once your autoguiding system is set up, it’s time to put it to use. Here’s a basic step-by-step guide to get you started.
The Calibration Process
Before you can start using your autoguiding system, it needs to be calibrated. This process involves the software learning how much it needs to adjust the mount’s movement to compensate for the guide star’s motion. Most autoguiding software will guide you through this process, which typically involves selecting a guide star and letting the software make some test adjustments.
Understanding and Adjusting Settings
Once your system is calibrated, you can start adjusting the settings. One of the most important settings is the ‘aggressiveness’ of the corrections. Setting the aggressiveness too high can lead to overcorrections and a ‘chasing’ effect, where the system is continually making large adjustments. On the other hand, setting it too low may not provide enough correction, leading to star trailing in your images.
Another crucial setting is the exposure time for the guide camera. Shorter exposures will provide more frequent updates, but the guide star may not appear in every frame. Longer exposures ensure the guide star is always detected, but you might have longer gaps between corrections.
Troubleshooting Common Issues
Like any complex system, autoguiding systems can encounter issues. Common problems include not being able to find a suitable guide star, the guide star disappearing during a session, or the corrections not having the desired effect. Each of these issues can usually be resolved by adjusting the settings or re-calibrating the system.
Understanding how to use your autoguiding system is an important step in improving your astrophotography. With practice and patience, you’ll soon be capturing breathtaking images of the cosmos.
FAQ
What equipment do I need for autoguiding?
For autoguiding, you will need a guide scope, a guide camera, a computer with autoguiding software, and a motorized mount compatible with the software.
Do I need a special camera for autoguiding?
While you don’t necessarily need a “special” camera, a dedicated guide camera will typically provide the best results due to its high sensitivity and compatibility with autoguiding software.
How do I choose a guide star?
Most autoguiding software can automatically select a suitable guide star. It’s best to choose a star that’s near your target and bright enough for the guide camera to detect.
Conclusion
Autoguiding is a powerful tool in astrophotography that enables you to capture the breathtaking beauty of the cosmos in vivid detail. It may seem complex at first, but with some patience, practice, and the right equipment, it’s an accessible technique that can dramatically enhance your astrophotography skills. So, why not give autoguiding a shot and see how it transforms your celestial captures?