Telescopes

Comparison of 4 different planetary cameras using a Celestron EDGE HD8 on an Advanced VX mount for the moon and Jupiter.

Comparison of 4 different planetary cameras using a Celestron EDGE HD8 on an Advanced VX mount for the moon and Jupiter.

 

Introduction

 

A comparison of 4 different planetary cameras using a Celestron EDGE HD8 on an Advanced VX mount for the moon and Jupiter is provided in this article. There are a number of different planetary cameras on the market. They range in price from approximately £100 to £2000 to suit a wide range of different budgets. The quality of images increases with higher cost. However, lower budget cameras still offer images that show details on objects such as the moon and large planets.

 

This article compares 4 planetary cameras by taking images of the moon and Jupiter. Capture and processing of images is described, images are presented for comparison and the results discussed. Finally, possibilities for further work are also presented.

 

Method

 

A Celestron EDGE HD8 Schmidt Cassegrain Telescope (SCT) was used on a Celestron Advanced VX Mount. The following cameras were compared ranging from approximately £100 to £400 to provide an indication of the quality of images produced by relatively lower budget cameras for the beginner or customers with lower budgets.

Solar system imager (colour)

ZWO ASI 120 MM (monochrome)

ZWO ASI 130 MM (monochrome)

Celestron Skyris 618M (monochrome) and the updated 132C (Colour)

 

The VX mount was aligned by lining up the peg on the top of the tripod with the North Star (polaris). Precise polar alignment was not carried out. The mount was then placed on the tripod and aligned using a two star alignment method and 2-3 calibration stars. A 40mm eyepiece was used for alignment. This method was found to be sufficient from planetary imaging.

 

The eyepiece was then removed and replaced with the planetary camera. The USB lead (supplied with each camera) was attached to the camera and placed in the USB2 port of a laptop. There was no USB3 port on the laptop used so the Celestron Skyris was plugged into the USB2 port, for which it is still compatible. Capture software supplied with each camera was downloaded onto the laptop prior to the procedure. This is supplied with each camera.

 

An 8 inch Bhatinov mask was placed on the front of the EDGE telescope. The telescope was then slewed to a bright star and focused. Once focused the telescope was slewed to the object of choice for imaging.

 

Using the appropriate capture software, the exposure and gain were adjusted as appropriate for the object being imaged. The frame rate was chosen to provide an optimal image for the particular camera. 30fps was used for the Solar system and ZWO cameras and 60-70fps for the Celestron Skyris cameras. 1 minute exposures were taken in each case. The solar system and ZWO images were processed using Autostakkert 2 and the Skyris images using Registax. The percentage of frames stacked was adjusted based upon the quality of image obtained.

 

Results

 

The images below show the results obtained for each camera. The Jupiter images were cropped so they were the same size for comparison purposes.

 

Solar system imager

moon solar system imager

Moon taken with the Solar System imager and processed in AS2

Jupiter solar system imager

Jupiter taken with the Solar System imager and processed in AS2.

ZWO ASI 120 MM (monochrome)

Moon ASI 120 1280x960

Moon taken with ASI120MM at 30fps and processed in AS2.

Jupiter taken with an ASI120MM through a Celestron EDGE HD8.

Jupiter taken with the ASI120MM at 30fps and processed in AS2.

ZWO ASI 130 MM (monochrome) 

The moon taken with a ASI130 through a Celestron EDHEHD8

Moon taken with the ASI130MM at 30fps and processed in AS2.

Jupiter ASI 130 1280x1024 TIF

Jupiter taken with ASI130MM at 30fps and processed in AS2.

Celestron Skyris 618M (monochrome)

Jupiter skyris0001 R6 stacked

Jupiter taken with the Celestron Skyris 618M at 60fps and processed in Registax.

moon skyris 4

Moon taken with the Celestron Skyris 132C at 70fps and processed in AS2

 

A difference in quality of images can clearly be seen comparing the 4 cameras. This is particularly pronounced in the level of detail resolved in the gas bands of Jupiter. More gas bands are identifiable using the celestron skyris and the image appears sharper compared to the other cameras.  A significant difference can be seen comparing moon images with the solar system imager and ZWO cameras. 

 

A difference in field of view can also be seen comparing the 2 ZWO cameras. This is due to different sized chips on each camera. The wider field of view on the ZWO ASI130MM makes this camera better for moon images compared to the ZWOASI120MM. Conversely the smaller field of view of the ZWO120MM makes it better for imaging Jupiter. The original image of Jupiter was much smaller using the ASI130MM compared to the ASI120MM before they were cropped to the same size during processing. The solar system imager offers an even wider field of view compared to the other cameras. The FOV can be altered for all cameras by using either a barlow lens or a focal reducer. These 2 products normally need to be bought separately. However, some telescopes include barlow lenses as well as eyepieces when purchased.

 

It should be borne in mind that the images were not all taken at the same time or necessarily on the same night. Therefore, the quality of images will be affected by differences in sky quality. Also with experience of using a specific camera, optimal settings are learnt for different objects. This means that someone experienced in using a particular camera tend to obtain better images, even compared to more expensive cameras.

 

Further work

 

This experiment could be developed further to include the following:

 

  • Image the moon and Jupiter using other planetary imagers according to the same procedure:
  • Use the planetary cameras to image bright deep sky objects such as M42 and M13:
  • Image other objects such as saturn, mars, venus and the sun;
  • Do an accurate polar alignment using a polar scope and the Advanced VX polar align function to see if it made a difference to the quality of images;
  • A comparison of images received at varying levels of sky quality.
  • Using a different telescope to compare planetary imagers.
  • Comparing planetary imagers using barlow lenses and focal reducers.

Like this post? Spread the word!


Posted on November 26th, 2015.