So what is involved in Astrophotography?

Astrophotography requires a variety of interests and technologies including camping, physics, computers, software, photography, astronomy, engineering - mechanical and electrical- and art.  Time, patience and perseverance are also required.


Let's walk throughout the process to gain an appreciation of the complexities to create a scientifically accurate, esthetically beautiful deep-space images.


                                                                         

 

Location, location, location ...

For those of us living in or near highly populated areas with streetlights, businesses, illuminated sports fields, etc., at night  we experience a light dome  arcing across the night sky.  Imaging deep space objects in the night sky requires long exposure times, which is difficult under a light dome

 

I live in Arizona, which is among the best locations for astronomical observing and imaging. In order to find a dark site I travel to, and camp at, locations more than 100 miles away from any light dome areas.
 
Generally I travel to these remote locations about 8 times a year, camping for five or six nights.  Of course, weather is a factor, and travelling in the summer monsoon season is usually not productive.  Additionally, the best (darkest) nights are during the New Moon, when it is "dark".  This period is sometimes called "dark of the Moon" or "DOTM".
 
These 8 or so outings each year will generate sufficient digital data for only a couple good images, but plenty of pressing hours back home to extract the best possible images.

Equipment

My current telescopes:

  • ASA10 Newtonian with a 10 inch concave mirror as the main light collector, and a 3 inch angled secondary mirror aboard an Astro-Physics AP900 German Equatorial Mount.   
  • StellarVue SVS 130 refractor aboard a Losmandy G11, Germini 2, German equatorial mount.

 
The Mount  is aligned to the North Celestial Pole - the point in the sky around which the Earth rotates. With the help of an attached computer and a small guide scope, the telescope stays aligned very accurately and keeps "locked" onto the object being imaged even as the Earth rotates.  
 
My current cameras:

  • Santa Barbara Instrument Group STT-8300M.  
  • Finger Lakes Instrumentation, FLI 11002
 
The CCD chip can be cooled to 50 degrees C below ambient, which helps ensure that the light accumulated during the long exposures is retained and significantly reduces thermal noise.  The small red box is the camera, the black tube is the camera lens, and between the lens and the camera is the 8 position filter wheel.  The filters I use are Astrodome, Red, Green, Blue and Luminance as well as Astrodome narrowband, H Alpha, OIII, and SII.
 

Field Work & Data Collection

For managing my entire equipment set up, I use Maxim DL (software) that controls the telescope and mount (locating and tracking objects), the camera (exposure length, number of exposures, CCD temperature) and filter wheels (which filter to use) as well as other controllable functions.  
 
Technically and mathematically, the digital images collected are called data, which are comprised of both signal (the object we are trying to image) and noise (everything that is conspiring against me to destroy the signal).  "Noise" comes in many forms: thermal noise, light pollution, sky brightness gradients, cosmic rays, pixel defects in the CCD and more.  
 
Reduction of "noise" - which can never be completely eliminated - is essentially for good images, and the CCD chip, which is monitored by the camera and the software, must be cooled as much as possible.
 
In order to reduce the "noise" in the digital image generate directly from the CCD chip and improve the signal to noise ratio, I take "calibration" images (the telescope is covered so no light falls on the CCD chip); the images are later subtracted from the final image.
 
Typically, I take 10 images through each filter and each image is a 10minute exposure.  So the total minimum exposure time is 5 hours for 30 images 
 

Image Processing  - Color & Details

When I arrive home, the image processing work begins to extract a detailed color image from the multiple exposures taken in the field.
 
There are several software packages that support the digital image processing.  Pixinsight, developed by Pleiades Astrophoto, based in Valencia, Spain, is an advanced imaging platform specializing in astrophography.  
 
There are numerous steps and hours of computer time to process the many "noisy" grayscale images into a final, full color detailed image.
 
During the processing, I have many opportunities to make artistic choices.  The final images becomes the personal expression of the astrophotographer.  This creative technique is...
 

                   the Art & Science of Deep Space Imaging