Welcome to Houston Astronomical Society

Image Capture Workflow

By Don Selle

This is the first in a series of “how-to” articles to help beginners learn astrophotography. The series will assume that long exposure imaging will be done through an OTA on a GoTo telescope mount that can be polar aligned. The camera attached to the OTA is either a cooled dedicated astronomy camera or a DSLR attached at prime focus. Since there are so many combinations of specific equipment the articles will assume that the telescope and camera have been set-up, equipment connected to a computer, powered up and checked out.

Most beginning astrophotographers (me included) were inspired by the work of others to jump into the hobby, not realizing how involved creating those beautiful pictures can be. No matter how much you know about daylight photography or how technically inclined you are when starting out, learning astrophotography can seem like a huge steep hill to climb.

If you can develop a consistent imaging workflow, a series of steps that you follow each time you go into the field, your astrophotography experience will be much more pleasant and productive. In this column we will explore at a high level the steps involved in a typical imaging workflow. Over the next several columns, we will take each of the steps and dig into them in more detail. So, let’s get started.

By Don Selle – Guidestar Editor

The month’s Guidestar cover is a wonderful image by HAS member Don Taylor of the eclipse of August 21, 2017. I thought it was very appropriate image for the April cover because the next total eclipse to race across much of the USA will happen on April 8, 2024, and we are a little more than half-way timewise between the two events.

The 2017 event was dubbed the Great American Eclipse because the path of totality ran the entire length of the USA. From the Pacific Ocean, it crossed the Oregon coast, ran across the Rockies and Midwest, then exited into the Atlantic Ocean over the coastline of South Carolina. The build-up for the event was tremendous – practically everyone knew it was coming, and its summer date encouraged many (including me) to schedule family vacations planned for observing the eclipse.

False Twilight: The Zodiacal Light – Is it a Reflection of Mars?

By Will Sager

Some evenings it seems to take forever for the sky to get dark. Normally, we progress from sunset to civil twilight to nautical twilight to astronomical twilight to dark. The civil twilight occurs between sunset and the sun being 6° below the horizon, nautical twilight when the sun is between 6° and 12° below the horizon, and astronomical twilight from 12°-18° below the horizon. After astronomical twilight, the sky should be dark and remain so until astronomical twilight begins before dawn. But sometimes, especially in the spring and fall, the sky is brighter longer because of the Zodiacal light.

This phenomenon is attributed to the scattering of light by tiny dust particles in the plane of the solar system. It usually appears as a diffuse triangular region, broadest at the horizon and narrowing towards the zenith. Zodiacal light is dim enough that light pollution or the Moon’s glare will mask its faint glow. In clear, transparent skies with no light pollution, the Zodiacal light soars across the entire sky, with a slight brightening at the anti-solar point, where backscattered light causes a brightening called the gegenschein. In less perfect conditions, Zodiacal light is a brightening of the western sky after sunset or the morning sky before dawn, when it is called the “false dawn”. Although Zodiacal light can be seen on most dark nights, it is most prominent after sunset in the spring and before sunrise in the fall.