The blog has been looking a bit bare this month, though with Astrofest and a somewhat dented credit card I do have something to talk about despite the terrible weather.
I went to Astrofest with the plan of replacing my mount, I love many things about the sphinx and I’ve done well with it over the last year but unfortunately my load capacity requirements have reached the point that it is beyond the ability of the sphinx to cope with it. So I had to make a call on a new mount, the choice was between the EQ6 and the Celestron CGEM, the EQ6 had the advantage on initial price, but would need upgrades to replace the saddle mount to a losmandy style which would bump it up to not far off the CGEM. It does however offer access to the excellent EQmod software suite.
The CGEM is at heart a modified EQ6 sporting several useful upgrades to the budding astrophotographer, servo motors replace the stepper motors, the bearings are different, it comes with a long losmandy style saddle as standard and will track up to 20 degrees past the meridian for excellent uninterrupted imaging.
In the end I went with the CGEM based on the above reasons and some excellent reviews, I took it home after the show finished on the Saturday and spent the Sunday modifying my temporary pier to get it mounted, more on that later.
Once mounted the long wait for a clear night started, I managed to snatch a few hours here and there which gave me enough time to get the mount aligned and to learn how to use the goto properly and configure the many options. I’m loving having a mount that can park and hibernate, it saves so much time in setup.
Eventually the skies cleared for a full night which finally gave some proper time for testing. In all movements the mount is very positive, making no sign of being under strain when slewing. Once aligned using the two star alignment and a couple of additional calibration stars goto accuracy was excellent, putting each object central on the canon 1000d.
Periodic error however is much worse than seen on the Sphinx and will need properly training, my initial results using Celestron’s own PEC tool were disappointing. However I have read of very good results achieved with PEMpro and the CGEM, but unfortunately the software currently has a bug which stops it properly working with my SPC900NC webcam. If anyone knows of any other software for training PEC which can upload it’s results back to the mount please let me know, I seem to have no end of software which can analyse PE but none of them can push the results back.
Right now guiding is basically perfect in declination but I am getting elongated stars in RA, so PEC is a priority.
The pier is problem, the CGEM is much heavier than the Sphinx and the amount of vibration and movement in my cobbled together multi-section pier is not acceptable. I have now managed to get hold of a length of 6″ outside diameter steel tube and some 10mm steel plate. I’ll be cutting this during the week and heading down to my parents on the weekend to get some helping welding it all together. Hopefully that will fix some of the unwanted movement in the mount and improve the guiding.
Over all though I’m happy with the CGEM, I’ll update with some pictures and PEC results once I have them, though the weather continues to look miserable for a while to come.
