Low light and the HS20EXR…how it performs.
Unfortunately the weather until this week hasn’t been good for night viewing, mostly overcast or rain. However the past to nights have been clear and frosty, so I decided to setup the HS20 piggybacked on my 4 inch short focal length Refractor.
Rather than use a dedicated mount with slow motion drives I used it on my “Grab & Go” mount as the maximum exposure time would be 15 seconds at most. This would produce a reasonable image with only a tiny amount of star-trailing. As it turned out the wind, although only a very light breeze caused more elongation in the images than the exposure time.
|The business end. HS20 mounted on
105mm Skywatcher Refractor.
Once set up in the late evening I covered everything with a towel and left the equipment to cool to ambient temperature. There’s nothing worse than seeing heat shimmer in an eyepiece or photo.
Next on the list was a couple of shots about 30 minutes after dark, looking at a bright star and testing focus method. It turned out that the most reliable focusing was achieved by having focus set in “Tracking Mode”.
The camera setup that was used for every shot from then on was as follows.
- Focus: Tracking Mode
- Mode setting: Manual mode
- White balance: Shade
- LCD Brightness: -5
- ISO: 200 & 400
- Shutter speeds used: 15, 13 & 8 second exposures
- Display information: Off ( once setup confirmed).
- Shutter release: 2 second timer.
- Focal lengths used : 30 to 80mm equivalent (DSLR)
- AE Metering: Average
- Image Stabilisation: Off
The amount of detail in one
frame when processed through Registax 6 is remarkable.
The finished frames seen here are two stacks of two images (4 in total) stacked and processed using Registax 6.
|Processed image 4 x stack of
Sagittarius & Scorpio
As these images were shot in the southern hemisphere our northern readers will need to flip the images. In the two images above, Scorpio is at the top of the frame & Sagittarius at the bottom. The large open star cluster M6 can be seen at center of the image.
|The Southern Cross is easily seen
here lying on its side, with Acrux, the brightest star in
the constellation at center of image.
The following two images were processed in exactly the same manner as the ones above.
|Processed image of the Southern Cross
The region of the Southern Cross contains massive star fields and dark lanes of dust. This includes the dark nebulae the “Coal Sack” Some of the darker areas are evident but these exposures are too short in duration to record the dark nebulae effectively, even though it is visible to the naked eye after one has become well dark adapted.
The second of the two Southern Cross images gives some indication of the amount of stars in this region. When photographed with large telescopes, the amount of visible stars is truly staggering. The final two images were taken with the HS10 last summer, the first is the original and the second was put through processing in Registax (a mild treatment) and is shot in Black & White. Shot at ISO 800 and showing considerable noise even after processing. This gives some idea of just how much better the HS20’s sensor really is. I wonder what a 2/3 sensor would be like in this EXR mode? One can only speculate.
|Unprocessed B & W image
from the HS10 of the constellation
|Single processed frame of the constellation Orion.
Processed with Registax