It has been a long time since I’ve written on the blog. Quite busy with the family and other projects.
In early august, I was able to complete the HyperTune of the Celestron CGEM. Re-greasing and re-assembly of the DEC axis went without a glitch. The videos from Ed Thomas at Deep Space Products are easy to follow and made the improvement process less stressful.
The gears meshing adjustments were made following the Hypertune technique (i.e. making the adjustments while the motors are turning and listening for any changes to the pitch of the motors’ sound). Worm, ring and spur gears were all carefully adjusted to reduce backlash and limit friction.
After re-installing all the equipment on the mount and making sure that all equipment and counterweights were back in their exact original positions. I ran two basic tests:
- While the scope perfectly balanced, I’ve measure how far I needed to slide the counterweights up the shaft to create enough unbalance and get the mount to move from the effect of gravity (i.e. I did this before and after the Hypertune process). Results: It looks like I was able to reduce the friction in Right Ascension by approximately 87%. Before Hypertune, I had to move the counterweights by 5.5″ for the mount to start moving. After Hypertune, It only took about 0.75″.
- Auto guided before and after Hypertune at same azimut and altitude. Results: It did not really improve auto guiding. I am still experiencing some oscillation in the Right Ascension axis. Enough to create 12% to 30% of star elongation on my 10 minutes sub-exposures. I even tried 3 different auto guiding configurations and obtained about the same end results:
- Guidescope at 480mm with QHY5L-II camera (3.75 microns pixels)
- Guidescope at 960mm with 2X barlow and QHY5L-II camera
- Celestron Off-Axis-Guider (OAG) at 1625mm
Conclusion: I believe I’ve reached the limits of the Celestron CGEM mount and no longer expect to improve these results with the current equipment and configuration.
New Image with a new technique
On August 24th 2013, I captured my first narrow band image of the IC63 nebula (The Ghost of Christmas Past) using the following filters (i.e. Hydrogen-alpha, Oxygen III and Sulfur II): 9 X 10 minutes sub-exposures though each filters. I processed the image with Pixinsight using the Hubble color palette. You can find the results here.
My equipment and process have improved over the years but with the limits imposed by the Celestron CGEM mount and the limited sky conditions present in my sub-urban area, I don’t believe I’ll be able to obtain tremendous improvements.
Next steps: try to image another nebula with narrow band filters with longer sub-exposures (i.e. 20 minutes instead of 10) and compare the results.
Thanks for reading and clear skies.
