The
mount is a GEMINI-G40 as mentioned before. Nevertheless, after many nights
of observation (more than 20) this mount turned out not to be completely satisfactory
in terms of open loop tracking performances : it looks not able to track properly
images with a pixel size of 3 arcsec.
20% of images acquired with a 60 sec exposure have to be thrown away, 60%
of images acquired with a 120 sec exposure. Exposure more than 120sec have
all to be thrown away.
So I decided to make it renewed/refurbished by VALMECA,France
(Serge Deconhiout).
The following items where changed :
1.
New RA worm and recutting of the main gear
2. RA and DEC axis remachined
3. New bearing holder + bearings
4. Complete redesign of the RA tracking system
Serge
and Me, the day I got back the mount.
New RA worm, before drive installation.
Complete
RA tracking system, bottom view
Drive
and detector for the PEC correction.
Also, in the meanwhile, I had a new spider from Gemini, because the older one was too difficult to adjust optically speaking.
Left,
new spider, right, the use of a laser autocolimator system, to avoid painfull
settings overnight....
So, I could get back my mount in April 2001. All the problems have been fixed and this is a really a GREAT work done by VALMECA : the first tests showed an excellent tracking, reliable PEC (no phase changes), now i could achieve 180sec exposure in open loop tracking, the next image shows a part of the M51 field, raw CCD image, unguided 180sec exposure :
Here, you can have a look to an image gallery, as a testimonial of the good results achieved with this system.
Finally, a 240sec exposure, showing the performance in suburb skies (15 km north of Munich). Based on this new technical achievements, plus the observation of a fast asteroid, my observing place became registred as IAU 214 observatory.
