Tutorials
Astrophotography is a very large and specialised field within Astronomy and tutorials on the subject are very specific and can be extensive depending on area covered. In astrophotography, post-processing is as extensive as actual imaging with your equipment. Tutorials posted on this page are written by members of the Gibraltar Astronomical Society unless otherwise stated. They are posted here with the author's consent (member or otherwise). Some tutorials are hosted off-site and are therefore linked as such. Please click the desired tutorial title in order to gain access.
POST-PROCESSING
by Kayron Mercieca
This tutorial is not a full workflow for PixInsight. It is a succinct noise reduction guide to using PixInsight's ATrousWaveletTransform, MultiscaleMedianTrasnform and ACDNR tools in tandem. These are applied to linear and non-linear images, both monochrome and colour. Noise is unavoidable even in the best of circumstances. Even dedicated, astronomical, cooled CCD cameras generate a level of noise through various means. Signal-to-Noise Ratio (SNR) also plays a critical role in how post-processing is later able to bring out the detail in images above the noise floor. The philosophy of noise reduction however is that noise should be reduced, not eliminated. This point is made numerous times throughout the tutorial with reference to consequences if noise is extensively smoothed out to the point of elimination.
The data used for this tutorial is Kayron Mercieca's Whirlpool Galaxy data, in LRGB broadband. The point of noise reduction and not elimination is nailed at the end with a demonstration of the possible end result by conservative noise reduction as opposed to aggressive noise reduction. This tutorial is hosted off-site in Kayron Mercieca's personal astrophotography website and the link therefore opens in a new window.
TECHNIQUE: PixInsight Guide for Noise Reduction with TGVDenoise (Off-Site)
by Kayron Mercieca
This tutorial is not a full workflow for PixInsight. It is a very succinct guide to using PixInsight's very powerful TGVDenoise tool for noise reduction of linear and non-linear images. Noise is unavoidable even in the best of circumstances. Even dedicated, astronomical, cooled CCD cameras generate a level of noise through various means. Signal-to-Noise Ratio (SNR) also plays a critical role in how post-processing is later able to bring out the detail in images above the noise floor. PixInsight has numerous powerful algorithms for noise reduction, but after an official assessment made in May 2013, it was concluded that TGVDenoise was the most versatile and also the most powerful. This tutorial aims to instruct in the use of TGVDenoise.
The data used for this tutorial is Kayron Mercieca's Heart Nebula data, in Hydrogen-Alpha narrowband. It is a monochrome image but demonstrates perfectly how TGVDenoise is employed. The same technique applies for colour images. This tutorial is hosted off-site in Kayron Mercieca's personal astrophotography website and the link therefore opens in a new window.
TECHNIQUE: PixInsight Guide for Combining Narrowband and RGB Data (H-α and O-III) (Off-Site)
by Kayron Mercieca
This tutorial is not meant as a full workflow through PixInsight, but instead is a guide regarding the process of combining narrowband and broadband data. It is generally a well-known technique to combine data from Hydrogen-Alpha into the Red channel of an RGB colour image. This technique strongly enhances nebulosity across entire images, bringing out fine detail and producing more intense overall nebulosity. Oxygen-III data can also be used in much the same way, mainly with the Green and Blue channels of an RGB colour image. This tutorial guide is based on an officially documented technique by Vincent Paris of PixInsight, instructing in the best way to combine Hydrogen-Alpha and Oxygen-III narrowband data with RGB colour data. The resulting images produce strongly enhanced nebulosity while maintaining realistic star colours.
The data used for this tutorial is Kayron Mercieca's Great Orion Nebula data, in RGB broadband as well as Hydrogen-Alpha and Oxygen-III narrowband. Luminance data is not used because that is a process for a complete workflow tutorial and is unrelated to narrowband-broadband data combination. This tutorial is hosted off-site in Kayron Mercieca's personal astrophotography website and the link therefore opens in a new window.
EXAMPLE: Eastern Veil Nebula - PixInsight Workflow for Small Targets (LRGB) (Off-Site)by Kayron Mercieca
This tutorial is another thorough workflow tutorial on post-processing images with a monochrome CCD camera using PixInsight. Often, we image targets that do not encompass our entire camera field of view. As a result, we are left with much of the image having a very low SNR (due to pure background) or saturated with thousands of stars. Rather than crop, it is at times desirable to tame the background and thousands of stars carefully in order to maintain image contrast and dynamic range. The general recommendation in these scenarios is to perform minor noise reduction on the background, keeping in mind it is about noise reduction and not elimination. This is done to prevent resulting images taking a fake, almost plastic-like profile. A star size reduction procedure is also carried out to tame the star sizes and thus achieve more contrast on the faint, diffuse nebulosity.
The data used for this workflow tutorial is Kayron Mercieca's Eastern Veil Nebula data, which is comprised of 30 Luminance, 20 Red, 20 Green and 20 Blue exposures, calibrated and stacked. This tutorial is hosted off-site in Kayron Mercieca's personal astrophotography website and the link therefore opens in a new window.
EXAMPLE: Wide-Field Orion - PixInsight Workflow for DSLR (One Shot Colour) (Off-Site)
by Kayron Mercieca
This tutorial is a thorough workflow tutorial on post-processing images captured with a DSLR camera (or other One Shot Colour camera) using PixInsight. The tutorial starts with tips on capturing a cleaner image that will allow for better detail and post-processing. It follows on extensively through each and every step necessary and recommended to treat your data with care and produce a stunning final result, with continual considerations made for the limits of DSLR cameras in terms of noise. This tutorial is essentially a post-processing example with real data and can be treated as such for relevant images to be post-processed with PixInsight.
The data used for this workflow tutorial is Tom Toughill's Orion's Belt and Sword image data, which comprises five exposures each of two minutes in length with a Canon EOS 7D and a 200 mm lens at ISO 200. Five dark and ten bias images were also used in the calibration process before post-processing in PixInsight (this is described in more detail within the tutorial). This tutorial is hosted off-site in Kayron Mercieca's personal astrophotography website and the link therefore opens in a new window.
by Kayron Mercieca
This tutorial is an extensive workflow tutorial based on post-processing images in PixInsight. The tutorial guides you through the process of taking your monochrome LRGB images comprising mosaic segments into producing the final result, going through each step one by one, in detail. It is essentially a post-processing example with real data and should be treated as such in order to learn post-processing techniques in PixInsight applicable to images of this kind.
The data used for this workflow tutorial is Kayron Mercieca's Garnet Star and Elephant Trunk Nebula Mosaic image data, which comprises two mosaic segments, shown joined up and fully post-processed in the final result. This tutorial is hosted off-site in Kayron Mercieca's personal astrophotography website and the link therefore opens in a new window.
by Kayron Mercieca
This tutorial is a quick guide tutorial based on post-processing images in PixInsight. The tutorial guides you through the process of taking your two monochrome narrowband images and producing a bicolour resulting image, through creation of a synthetic third image to fill all three RGB channels required for a colour image. Various methods are discussed as there are essentially numerous ways to combine two narrowband images into forming the synthetic third image. There is no final result in this tutorial but real data is used to demonstrate the differences obtained in colour balance.
The data used for this guide tutorial is Kayron Mercieca's Rosette Nebula in Narrowband image data, which comprises solely Hydrogen-Alpha and Oxygen-III narrowband data. This tutorial is hosted off-site in Kayron Mercieca's personal astrophotography website and the link therefore opens in a new window.
EXAMPLE: Rosette Nebula - PixInsight Workflow for Narrowband LRGB (with Ha as Luminance) (Off-Site)
by Kayron Mercieca
This tutorial is an extensive workflow tutorial based on post-processing images in PixInsight. The tutorial guides you through the process of taking your monochrome narrowband images into producing the final result, going through each step one by one, in detail. It is essentially a post-processing example with real data and should be treated as such in order to learn post-processing techniques in PixInsight applicable to images of this kind.
The data used for this workflow tutorial is Kayron Mercieca's Rosette Nebula in Narrowband image data, which comprises Sulphur-II, Hydrogen-Alpha and Oxygen-III narrowband data. This tutorial is hosted off-site in Kayron Mercieca's personal astrophotography website and the link therefore opens in a new window.
by Kayron Mercieca
This tutorial is an extensive workflow tutorial based on post-processing images in PixInsight. The tutorial guides you through the process of taking your monochrome RGB and Hydrogen-Alpha images into producing the final result in High Dynamic Range (HDR), going through each step one by one, in detail. It is essentially a post-processing example with real data and should be treated as such in order to learn post-processing techniques in PixInsight applicable to images of this kind.
The data used for this workflow tutorial is Kayron Mercieca's Great Orion Nebula in HDR image data, which comprises RGB data and Hydrogen-Alpha narrowband data in two sets - 1 minute exposures and 7 minute exposures (in order to produce the HDR result). The Hydrogen-Alpha image is used as the Luminance channel in order to maximise detail shown throughout. This tutorial is hosted off-site in Kayron Mercieca's personal astrophotography website and the link therefore opens in a new window.
CALIBRATION
by Kayron Mercieca
This tutorial covers a deeply important aspect of preparing your raw images for post-processing. Raw images contain the read-out noise from the camera, thermal noise from the CCD sensor (in the form of electrons firing off due to temperature producing unwanted signal) and vignetting from the optical system. Dark, bias and flat images are captured in order to calibrate the raw images and remove these artifacts.
Covered in this tutorial is the theory behind each type of image, guidelines of what to be aware of and method of capturing them to later use them for calibration of your raw images. A CCD camera with temperature control (ATIK 383L+) is used in this tutorial along with its included capture software (Artemis Capture). This tutorial is hosted off-site in Kayron Mercieca's personal astrophotography website and the link therefore opens in a new window.
by Kayron Mercieca
This tutorial covers a deeply important aspect of preparing your raw images for post-processing. Raw images contain the read-out noise from the camera, thermal noise from the CCD sensor (in the form of electrons firing off due to temperature producing unwanted signal) and vignetting from the optical system. Dark, bias and flat images are captured in order to calibrate the raw images and remove these artifacts.
Covered in this tutorial is an explanation of what each type of image is for and the process of using the free software DeepSkyStacker to perform the actual calibration of your raw images. This includes registering (aligning) all the raw images with each other, calibrating each image to clean them up and stacking the results to average them out and improve the Signal-to-Noise Ratio (SNR). Following this, for those using a monochrome CCD camera and having multiple calibrated images to later register (align) with each other, a final registration is performed so all images fall precisely one on-top of the other. This tutorial is hosted off-site in Kayron Mercieca's personal astrophotography website and the link therefore opens in a new window.
IMAGING
Setting up an Equatorial Mount on ASCOM with EQMod, Stellarium and Cartes du Ciel (Off-Site)
by Kayron Mercieca
The hand controller on mounts is a very popular accessory. It is both an aid in setting up an equatorial mount and a control-point for Goto to access stars, galaxies and nebulae around the night sky. With it however comes limits, mainly through the control interface being a simple hand controller with a tiny screen. Letting go of this may be hard for those used to it, but controlling your mount entirely through a computer is a very rewarding move. Not only do you gain simpler setting up, but you also gain a planetarium of the entire night sky around you, graphically displayed on your computer screen and updated in real-time. This also affords you all the functions of the hand controller, and many more on top. Fast and precise star alignment, going to your desired targets from a real-time view of the night sky around you (including being able to search for targets), plate solving to precisely frame targets for astrophotography (with no input from yourself) and being able to work with deep space mosaics are just the tip of the iceberg.
The tutorial goes through the process of preparing your computer for connecting it to your mount, by installation of the ASCOM platform and the program EQMod (to replace the hand controller). It then follows on to guide you through successfully making a connection between your mount and EQMod and then configuring and using Stellarium and Cartes du Ciel for Goto. All software used here is completely free and freely downloadable. This tutorial is hosted off-site in Kayron Mercieca's personal astrophotography website and the link therefore opens in a new window.
by Kayron Mercieca
Astrophotographers are well aware of the issue of not viably being able to zoom in or out in order to capture certain objects within their field of view. Large deep space objects (commonly large nebulae) tend to require multiple image segments comprising a mosaic in order to fully capture them. Though this is an easy task in terrestrial photography, it is not so easy in astrophotography where ultimate precision is key and your subject is not visible to the naked eye.
The tutorial covers the fundamentals of capturing mosaics in astrophotography, with tools needed for the aforementioned precision. This tutorial requires the user to control their mount directly through a laptop via ASCOM and employs use of the free ASCOM tool EQMosaic. This tutorial is hosted off-site in Kayron Mercieca's personal astrophotography website and the link therefore opens in a new window.
by Kayron Mercieca
When an astrophotographer aligns their equatorial mount to Polaris, it is common to follow the setting up with a star alignment. This requires picking a number of stars (normally two or three) across the night sky in order to slew to, precisely centre and therefore correct GOTO alignment. Not only is this process annoying to have to perform but from one night to the next, your alignment will not be identical and your target will therefore be in a different place in your images. This makes capturing the same object from one night to another a difficult task involving a level of guess-work. Plate solving resolves this problem.
AstroTortilla is a free tool that requires the user to control their mount directly through a laptop via ASCOM. The tool captures an image with your imaging camera, analyses it to figure out precisely where you are pointing to and then corrects the alignment so that your intended target is precisely in the centre of your field of view. While doing this, AstroTortilla adds an alignment point as if you were performing a star alignment procedure. This essentially does the job for you without much user interaction, does so precisely and allows night-to-night imaging of a target with ease and precision.
This tutorial covers the installation and setting up procedure of AstroTortilla - something that needs to be done properly for it to work at all. Instructions for actual usage are also covered. This tutorial is hosted off-site in Kayron Mercieca's personal astrophotography website and the link therefore opens in a new window.
by Kayron Mercieca
Astrophotography is a hobby requiring precision. Equatorial mounts have motors and are designed to follow the night sky so that a target object is tracked throughout the night. Since deep space astrophotography involves very long exposures, precise tracking is key and unfortunately this is a very rare thing. Autoguiding is a way in which a second camera is put into the system (commonly through a second, smaller telescope mounted on top of the main telescope) in order to lock on to a star near your target, continually monitor its movement and if movement is detected, send correction commands to the mount to ensure the mount is precisely on-target throughout entire exposures.
The Orion StarShoot AutoGuider (SSAG) commonly comes packaged with Orion's Mini 50mm Guide Scope, providing a pretty inexpensive, lightweight, convenient and effective autoguiding system that adds very little weight to your existing imaging setup. This tutorial discusses its advantages, ups and downs and how to set it up from the box to using it from night to night with minimal setup time (under one minute once initially set up). Moreover, PHD Guiding is a free tool used for autoguiding and this is discussed in detail relating to its settings and optimum settings found for this autoguiding setup. This tutorial is hosted off-site in Kayron Mercieca's personal astrophotography website and the link therefore opens in a new window.