Steaphany
Well-Known Member
One of the subjects of photography that I enjoy is Astronomy and astrophotography. Prior to purchasing my SD14, I was well aware of the Nikon and Canon dSLRs being the predominant choice, but the capabilities of the Foveon imager, regardless of the reviewers complaints about high ISO noise levels, would still provide the functionality I was looking for. My decision was also based on wanting a general purpose camera flexible enough to handle all my photography needs.
I know that imager noise in astrophotography can easily be handled by the multitude of image stacking software packages which are commonly used to clean up and combine multiple frames. A common image medium used by amateur astronomers is adapting a low resolution webcam to a telescope and recording and stacking from AVI video files. I was sure a SD14 would out perform any webcam.
This is the results of my first astrophotography test. I used my Sigma 28 mm f1.8 EX DG Aspherical Macro which provides a 40.57° x 27.69° field of view. My SD14 was on my Velbon DF50 tripod which offers no means to track the sky. The used a manual focus and manual exposure was set to 16 Seconds with an f1.8. I set the ISO sensitivity to 100, to keep the noise down and to see just how well the SD14 would perform. I chose 16 Second exposure since it was the trade off point between maximum light collection while keeping the stars looking like point sources and not streaks across the sky. The White Balance was set to Overcast since my earlier attempts to photo a Moon rise turned out very inconsistent results with auto. To trigger the shutter, I used my RF remote control that I purchased through a vendor on ebay (I know I need to update the thread on Gear-Talk/Accessories).
I chose to aim the SD14 to Cassiopeia since it was on the meridian and nicely high in the sky, well away from the effects of the atmosphere near the horizon. Cassiopeia also has the Milky Way passing through it along with several star clusters and faint nebulae. It was also a small enough constellation to completely fit in the field of view.
I never bothered to let my eyes adapt completely to the dark, so I found it difficult to focus the 28mm lens on the bright stars of Cassiopeia since they were too faint. I knew they were in the center of the field of view, but not clear enough to properly focus. I knew that the 28mm lens, at f1.8, had a hyperfocal distance of 24.23 meters, so I temporarily aimed the SD14 towards the lights of a cellphone tower roughly 3 miles away, which would have the stars, effectively at infinity, in perfect focus.
This is what the SD14 recorded:
View attachment 871
This is a decent star field, low noise, with good focus. The bright stars of Cassiopeia are easily visible as is some of the color variations between the stars.
I then continued to shoot a total of 24 light frames while leaving the tripod and SD14 exactly in the same position. I also placed the lens cap over the lens and shot 2 dark frames. This took me roughly 15 minutes from start to finish. Keep in mind that the tripod has no means to track the sky as time passed by. Each frame had the stars in a slightly different position when compared to the other frames. The image stacking software combines the light frames, subtracts the effects of the imaging system recorded in the dark frames, and aligns each field to produce the final image.
I used IrfanView, http://www.irfanview.com/index.htm, to bulk convert the 26 X3F files into PNG format and I used DeepSkyStacker, http://deepskystacker.free.fr/english/index.html, to align, stack, and adjust the final image. An advantage of DeepSkyStacker is that it is able to identify a star from the surrounding sky making alignment automatic.:
View attachment 869
I was really surprised to see just how many stars where captured. DeepSkyStacker discarded several low quality frames and built this up from just 17 of the original 24 light frames. Remember this was at ISO 100 and the total exposure time was only 4 Minutes and 45 Seconds.
I did trying using RegiStax, http://www.astronomie.be/registax/, but found it taking a lot longer and the alignment algorithm brought the stars tagged by multi-point references into proper alignment but the surrounding faint stars were dragged into arcs facing the nearest reference point, caused by segmentation of the image. By contrast, DeepSkyStacker uses an alignment algorithm which positions and rotates each frame as a whole. Both have their place as I found Registax will accurately align and combine terrestrial and non-star field photos.
To help those here who are not astronomically inclined, I created a composite of the DeepSkyStacker image with a screen capture from my Sky map program. The alignment is not 100% but close enough for each of Cassiopeia's features to be identified:
View attachment 870
I know that imager noise in astrophotography can easily be handled by the multitude of image stacking software packages which are commonly used to clean up and combine multiple frames. A common image medium used by amateur astronomers is adapting a low resolution webcam to a telescope and recording and stacking from AVI video files. I was sure a SD14 would out perform any webcam.
This is the results of my first astrophotography test. I used my Sigma 28 mm f1.8 EX DG Aspherical Macro which provides a 40.57° x 27.69° field of view. My SD14 was on my Velbon DF50 tripod which offers no means to track the sky. The used a manual focus and manual exposure was set to 16 Seconds with an f1.8. I set the ISO sensitivity to 100, to keep the noise down and to see just how well the SD14 would perform. I chose 16 Second exposure since it was the trade off point between maximum light collection while keeping the stars looking like point sources and not streaks across the sky. The White Balance was set to Overcast since my earlier attempts to photo a Moon rise turned out very inconsistent results with auto. To trigger the shutter, I used my RF remote control that I purchased through a vendor on ebay (I know I need to update the thread on Gear-Talk/Accessories).
I chose to aim the SD14 to Cassiopeia since it was on the meridian and nicely high in the sky, well away from the effects of the atmosphere near the horizon. Cassiopeia also has the Milky Way passing through it along with several star clusters and faint nebulae. It was also a small enough constellation to completely fit in the field of view.
I never bothered to let my eyes adapt completely to the dark, so I found it difficult to focus the 28mm lens on the bright stars of Cassiopeia since they were too faint. I knew they were in the center of the field of view, but not clear enough to properly focus. I knew that the 28mm lens, at f1.8, had a hyperfocal distance of 24.23 meters, so I temporarily aimed the SD14 towards the lights of a cellphone tower roughly 3 miles away, which would have the stars, effectively at infinity, in perfect focus.
This is what the SD14 recorded:
View attachment 871
This is a decent star field, low noise, with good focus. The bright stars of Cassiopeia are easily visible as is some of the color variations between the stars.
I then continued to shoot a total of 24 light frames while leaving the tripod and SD14 exactly in the same position. I also placed the lens cap over the lens and shot 2 dark frames. This took me roughly 15 minutes from start to finish. Keep in mind that the tripod has no means to track the sky as time passed by. Each frame had the stars in a slightly different position when compared to the other frames. The image stacking software combines the light frames, subtracts the effects of the imaging system recorded in the dark frames, and aligns each field to produce the final image.
I used IrfanView, http://www.irfanview.com/index.htm, to bulk convert the 26 X3F files into PNG format and I used DeepSkyStacker, http://deepskystacker.free.fr/english/index.html, to align, stack, and adjust the final image. An advantage of DeepSkyStacker is that it is able to identify a star from the surrounding sky making alignment automatic.:
View attachment 869
I was really surprised to see just how many stars where captured. DeepSkyStacker discarded several low quality frames and built this up from just 17 of the original 24 light frames. Remember this was at ISO 100 and the total exposure time was only 4 Minutes and 45 Seconds.
I did trying using RegiStax, http://www.astronomie.be/registax/, but found it taking a lot longer and the alignment algorithm brought the stars tagged by multi-point references into proper alignment but the surrounding faint stars were dragged into arcs facing the nearest reference point, caused by segmentation of the image. By contrast, DeepSkyStacker uses an alignment algorithm which positions and rotates each frame as a whole. Both have their place as I found Registax will accurately align and combine terrestrial and non-star field photos.
To help those here who are not astronomically inclined, I created a composite of the DeepSkyStacker image with a screen capture from my Sky map program. The alignment is not 100% but close enough for each of Cassiopeia's features to be identified:
View attachment 870