Just before Christmas I returned to the UK University of Central Lancashire's Alston observatory to finish off installation work that was started a number of weeks earlier. The completion work had to be put on hold due to a couple of factors and for scheduling reasons too. You can read more about this first visit here.
Checking the level of the top of the levelling flange. We think thats fairly level!
Working on the partly dismantled telescope
The morning of this visit's first day involved a partial dismantling of the set up. With help from Dr Mark Norris (who leads the teaching at the observatory) with some of the heavy item lifting, the L-mount was first removed and laid carefully on the floor followed by the wedge and pier flange. A new pier flange was then fitted, levelled and secured, followed by the reattachment of the L-350's wedge (taking time to get it pointing as close to true north and the correct elevation to minimise any later adjustments) and then the L-350 itself was then lifted back in position and bolted to the wedge. Due to afternoon teaching commitments, Mark left to return later, leaving me to continue some other work involving the set up of their observatory PC. All the necessary and up-to-date PlaneWave software was installed followed by their QHY camera software and drivers and MaximDL which is required for doing the mount modelling. All the software was tested and worked as it should. The observatory's imaging camera was also equipped with its Baader UFC accessories ready for connection to the telescope. The remainder of the day involved discussing/training on how to operate the telescope/camera and doing the necessary mount modelling.
Sunrise over the UCLAN Alston Observatory's Mosen Holden CDK700 enclosure
The following day started with a lovely sunrise over the observatory buildings - a nice sight to behold to start the day's work activities. The first task was to balance the telescope. From the previous visit we had marked the DEC balance point for the telescope with all accessories attached but what was left to do was to balance the mount in RA. We knew that the mount was "fork arm (heel) side heavy" so the fork arm end of the mount needed to be moved inwards towards the RA rotation axis.
PlaneWave make this a relatively easy task to do without detaching the complete L-mount from the wedge or a pier. The first step was to remove the mount's access coverplates, unplug it's power and data connectors and safely store the cables to avoid them being damaged during the removal and reattachment of the fork arm assembly. There are six hex-bolts that hold the L-mount to its drive base. With the mount's arm pointing down towards the ground these bolts can be removed without the worry of the mount falling from the drive base as there are two shoulder bolts that are located in keyhole shaped openings on the drivebase top plate to keep it in place. With help from Mark we gently pushed the mount upwards and then away from the base and laid the mount on the ground cover. On the underside base of the mount there are two pairs of six holes and the shoulder bolts were each in the "factory default position". These bolts were unscrewed and were moved to the last hole meaning that the arm was in towards the RA axis as far as it could go. The mount was then reattached to the drive base, secured with some bolts and the telescope attached.
The L-mount drive base after removal of the upper portion of the L-350 mount
Final location of the shoulder bolts on the underside of the L-350 before reattaching to the drivebase
We found that the mount was now too heavy on the opposite (telescope/toe) side. The above procedure was repeated but now moving the shoulder bolts to an intermediate position. After reattaching the mount and scope we found that the balance was much better but just ever so slightly telescope/toe-side heavy - but not by much all. To get the balance "even more perfect" Mark proposed an idea was put into practice. A bag of bolts (used for balancing purposes on old telescope!) hung off the side of the fork arm and additional bolts were added to the bag until perfect balance was achieved - all that was needed was a few hundred grams of bolts. A small plastic electrical junction box was found that was the perfect size and fit for the volume of bolts and also for fitting to the fork-side base. The box was drilled and bolted to the base of the fork arm and then the lid screwed on to keep the bolts securely in place. This was a simple, quick and a neat solution for fine balance...and it actually "looks quite the part too!".
With the telescope attached and the whole system balanced, the job of data and power cable routing was then done taking time and care to make sure there was no strain or snagging on the cables. Cables were then labelled and the mount access coverplates were then replaced and then the observatory PC was brought into the dome and set up temporarily next to the telescope. With the PC now powered up, the mount and camera were all detected and other software tested for proper operation. After a well deserved coffee break, it was time to tune the mount's direct drive motors. This is a simple task that is done through the PWI4 software and took about 20 minutes, with the mount making different pitched noises as it progressed through its tuning cycle.
Performing the cable routing. The black box is the "fine balance weight" described in the text
Just waiting for the sky to clear!
The observatory enclosure is operated through ACP Observatory Control Software and after a few changes with some of its settings, the software picked up the pointing position of the telescope and moved the dome accordingly. Although it was cloudy, using PWI4 to control the mount was slewed to different parts of the sky to check operation and how the mount was performing where the RMS was typically 0.03"-0.05" on both axis.
Now it was all systems go!
Earlier in the day the weather forecast had predicted 50% chance of clear sky after sunset. However that forecast had changed for the worst - 100% chance of cloud cover. With that forecast seemingly becoming more likely for the rest of the night, the two day's work and this project was concluded with everything working as it should.
Updates: Contrary to the weather forecast for that (final day), later on in the evening there was a short period of partly clear sky which allowed Mark to take a quick "first light" image of the Moon and then later on obtain a "quick" 40-point model using a random grid pattern and with no mechanical adjustments the telescope pointed at a target and it was dead centre in the field of view.
First Light image of the Moon (note the very low RMS highlighted in green); Courtesy of Dr Mark Norris
Target centred after 40 point model; Courtesy of Dr Mark Norris
5th Jan 2022: Mark used the telescope to track and image the movement of the recently launched James Webb Space Telescope (JWST; Where is Webb?) showing a change in its apparent brightness, and which is on its way to the L2 point in space.
About the author: Lee Sproats
Dr. Lee Sproats has been interested in astronomy since watching Star Wars in 1977 and has appeared on the UK Sky at Night TV programme. He then went on to study Astronomy where he obtained a degree and then a PhD in the subject at University College London/Mullard Space Science Laboratory. He has worked in Australia in radio astronomy and used optical/infrared telescopes on Hawaii and La Palma and Lowell and Kitt Peak observatories in the USA. After working for the University of Surrey to promote the use of computers for teaching in UK higher education and then as an IT trainer for a stock market company, he went on to work for Greenwich Observatory Ltd where he ran their northern branch and then worked for David Hinds Ltd dealing with our and Celestron products. He is often involved in flight excursions that take passengers to observe the northern lights, has led trips to see the great USA 2017 eclipse near Hopkinsville and was lead astronomer onboard a specially chartered 737 to view the 2015 total solar eclipse at 38,000ft. Lee`s astronomical interests include Lunar observing, astrophotography, photometry and pro-am collaborations.
Since David Hinds stopped operation in December 2020, Dr. Sproats works for Baader Planetarium as our UK representative/consultant and is responsible for looking after our UK/Eire dealers, dealing with Baader Planetarium/PlaneWave/10Micron product support, writing articles and also is involved in our large telescope and observatory instrumentation projects.
