5th Nov 2010
I have been having collimation issues with my 20” mirror since taking it out of the Dobsonian chassis and putting it into a new custom built open tube in the observatory. The builder who is a friend of mine, Rod Greening has continued to develop the cell for me to overcome this problem.
On Friday evening our mutual friend Es Reid brought returned the cell after Rod had been working on it for a few days to get the mirror to float more easily and hold collimation better.
The evening was foul, the rain was torrential lashing onto the observatory as we worked inside and the wind howled through every nook and cranny! But there was something both exciting and comforting in being able to work on my astronomical kit despite the weather outside.
Installing the modified cell took a little over an hour and Es says it shows a good chance of improvement although at the time of writing this blog entry up it is untested.
In addition to the cell installation Es had bagged some aluminium channel which he intended to beef up the side of the 20” tube and move the heavy 6” triplet refractor onto to elevate flexure and to aid keeping both instruments in alignment with each other. This project took a little longer as it involved searching for bolts to fit the new support struts, cutting and drilling and filing to get a good fit and finish.
Es is a fine engineer and makes a tidy and accurate job of just about everything he turns his hand to, I don’t and Es rightly terms my crude efforts as “agricultural”.
I will prime and paint the bright aluminium supports at some future date to blend them in with the rest of the structure.
With the tube rings fitted to the new struts it was time to put the tube back, the back end complete with focuser had been removed to facilitate this and as I manoeuvred the front end heavy tube my left foot went down into the ‘Dob pit’ a corner of the observatory without a raised floor where the old 20” chassis is stored. I fell backwards landing against the wall on my backside. The tube crashed to the floor, or rather the heavy OG end did I managed to keep a grip on the lighter end. The steel dew shield took the impact and was crushed virtually flat, dramatic as it was this ‘crumpling’ likely save the precious triplet objective by absorbing the impact.
Shaken and a little bruised we continued to fit the refractor in place before we closed up and Es departed in the still wild night at 11pm.
6th November 2010
Saturday dawned in complete contrast to Friday evening, bright blue sky and sunshine.
By late afternoon I managed to grab an hour to start to align the telescopes by around 4pm I could make out Jupiter and Altair in the dusk sky. I sent the goto system to the later and then one by one got all of the scopes directed onto it. I collimated the 20” slewing it around the sky and then testing it again, seating the mirror with a few bangs on the cell back board I eventually go it so that the shift was pretty small, but it was still there!
I then fitted Watec cameras into the focusers of the 20” & 6” and the Mintron camera onto the 80mm F5 finder and for the first time ever I had achieved what I had hoped for quite a few years, 3 scopes, 3 cameras, 3 differing fields of view and Altair bang centre in 3 monitors simultaneously!
The next clear night will show if things can stay that way?
Clear Skies, Dale