| Raheny Observatory Was founded in 2006 and was issued observatory code J41 in Sept. of 2007. Having spent endless frustrating nights setting up equipment only for the cloud to roll in and spoil my fun, I decided an observatory was the only option. But what type of observatory, A dome, roll off roof, roll away shed. Given a number of factors including sometimes strong prevailing wind and budget, I opted for the roll off roof type. This gave me some protection from wind but also kept the cost as minimal as possible. Thanks to some good friend, Carl O'Beirnes, Gary Clarke and Ray Doyle, the bones were in place over a long weekend. I for a design similar though not exactly akin to 'Sky Shed' Initially I used roller type ball bearings running along a flat steel , but this became very stiff over time. This year I replaced them with serious roller bearings running along a stell U section (since its upsaide down I should probably call it an n section!) . These are the type used for heavy gates of gated apartment complexes. Each one is rated for 600kgs for of these make my roof glide like its on air. The next step is to motorise this arrangement. |
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Fig.1 - Raheny Observatory (MPC #J41)
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The first job to build the observatory was to install a pier. The observatory site is just 15 metres from a main train line here in Dublin, there are trains every few minutes at peak times so I knew the pier construction would have to minimise dispruption from vibration when trains passed. The pier is basically an 8ft piece of PVC pipe 14" diameter. It is sunk 4ft into the ground and protrudes 4ft above (ain't my maths brill;-). The hole was then filled with concrete and the pipe itself also filled with concrete. As you can see from Fig.14 (bottom of bage) two steel plates are mounted with vibration isolation rubber sandwiched between them. Although this does not take away all of the vibration when a train goes by, it keeps it to a minimum. Only very short exposures show the shake, anything over 30 secinds averages out the couple of seconds where a train goes by. There was already slabbed patio stones in place and well seated so I just left them there, built the observatory on top and then poured 2" on concrete inside to make a level floor. The rest of the observatory was built from various timbers. The shiny exterior is thin aluminium sheeting which is there for two reasons. For security (to stop someone popping off the timbers, and for heat reflectance, so it all stays cool during the day. There is plently of ventilation under the eaves of the rook to allow airflow at all times.
I'm not going to go into the previous equipment just to say I started with a 9.25" SCT on a CG5 mount, moved up to a 10" f/4 newtonian on a Celestron CGE mount, the replaced the 10" Newt with a C14 and then replaced the CGE with my beloved AP1200 mount.
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So lets get onto the current equipment. The overview shot (fig.3) shows all the important bits. You can see the pier with the AP1200 ontop. The C14 is mounted on the AP1200. The focuser is a Moonlite SCT crayford and the main camera is an SBIG ST8-XME. The guided scope/wide angle option is a Celestron 80EDF 'Onyx' refractor and the guidecamera is an ATIK 16IC. Just a note on the dew shield. This is just a simple home-made job made from insulation material. I don't know what it is called but it's basically bubble wrap coated on both sides by aluminium foil. Makes a great dew shield. There is a 'Dew Not' 14" heating strap under there.
Fig.2 - Hitecastro Mount Hub Pro.
The blue box you see attached to the pier (fig 2)is the Hitecastro Mount Hub Pro. I must declare a vested interest here. I am part owner of the Hitecastro company and develop(ed) many of the products so I'll just say the the MHP contains a focus controller, 4 dew strip outputs, 8 relay controlled power outlets and a build in USB 2.0 hub. This means that all those cables go only as far as the pier rather than trailing across the floor to the PC itself. Only a single USB cable and a single power cable are needed to power the lot. All of these items are controlled through software so I can operate remotely.
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Fig.3 Equipment Overview
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Fig.4 - Astro-Physics AP1200 CP3 German Equatorial Mount.
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Lets have a look in a little more detail. Here's my baby my beloved AP1200 mount. Although it costs a fair bit, it is simply the very best you can but without remortgaging the house. The tracking/guiding/pointing ability is second to none and it carries all of the other equipment without even breaking a sweat. Out of the box periodic error was +/- 3.4 arc seconds. With periodic error correction trained, I have this down to +/-0.67 arc-seconds. I spent a lot of time getting very precise polar alignment and typically the polar alignment error is single figure arc seconds. This allows for quite long unguided exposures over 5 minutes with the C14 and pretty much indefinite with the refractor. |
| Moving on we look at the business end of the OTA (fig 5) with the camera focuser and focal reducer. The camera as I mentioned is the SBIG ST8-XME with CFW9 filter wheel. The filter wheel houses 1.25" astronomik LRGB filters. This camera is very sensitive (Over 80% QE at some parts of the spectrum) For science work the CCD is binned 2x2 to produce extra sensitivity and an image that fits on screen without resizing. The moonlite crayford focuser is a real joy to use hooked up to mount hub pro a single step of the motor moves the draw tube only 1.2 microns. The focal reducer is the NexGen 0.50x from Optec. From what I can tell its as good as you can get. However flat fields are still required. I do this with a home made flat field box. |
Fig.5 - SBIG ST8-XME Camera, Focal Reducer and Moonlite SCT Focuser.
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Fig.6 - Guiding Arrangement.
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The guide scope camera arrangment. The guide scope is ayttached to the Atik 16IC by a 2" extension tube needed to bring it all to focus. Focus is achieved using another one of Hitecastro focusing products, HitecDCFocus, focusing the guider is not too critical but every so often focus drifts and I like being able to correct this hands off/remote, The other thing just about visible in fig.6 is the losmandy guide scope rings and plate these are as solid as they come which is essential for good tight auto-guiding when required. The black box with the red buttons ontop of the C14 is the Hitecastro DC focus controller. This again allows remote control of the Skywatcher Motor (on the left side of the guide scope. |
| Some other items of note. Being so close to a public park, although its probably best not to into this on the web, I have some fairly extensive security arrangements in place not least of which is my main man, the mutt:) While the observatory is in use I operate an IP camera (fig 13), this enables me to see whats going on while i'm upstairs in the study. Partly for security and partly to ensure no disasters with bits falling off or cables snagging. Speaking of which to minimise this very real risk, the mount hub pro helps a lot, but it is also important to gather up the cables. Here the lowest tech gets used, some green garden tie is cheap and easy to replace while re-arranging cables from time to time. |
| Fig 7 shows the desk and computer (yes my desk is always that untidy, thats how I like it!). The computer is really nothing special, Dual Core processor, 4GB RAM, 500GB HD. What of more interest is the software I use. The heart of it all is a combo of ACP by DC3 Dreams in conjuntion with Maxim DL. This allows me to automate almost every aspect of the observatory. Collecting images becomes a snip. I just tell the observatory what I want to do and then go away and leave it. All going well (clouds keeping away) I will come back and find the images I asked for. The way ACP works is very clever bit still quite simple. Basically point the scope, take a short image to see where the scope is really pointing (plate solves the stars) then if required adjust the scope the last tiny bit to ensure the target is centred. All other aspects such as switching filters, calibrating with flats and darks and even focusing are taken care of automatically. Without ACP/Maxim DL it would not be possible for me to gather as many images as I do given the limited clear skies we get here in Ireland. Their is lots of other software too. Focus Max assists ACP/Maxim with focusing, PEM Pro, looks after periodic error correction of the mount plus polar alignment when required. My own Mount Hub Pro software lets me power all the equipment up remotely. There are lots of other pieces of software which look after everything from keep |
Fig.7 - The Computer.
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Fig.8 - L200 Spectrograph.
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Another piece of equipment not shown previously is my spectrograph. For those unfamiliar a spectrograph breaks up starlight into its component parts so that we can derive lots of information about the stars such as what they're made of and how they are behaving. The spectrograph shown in Fig 8 is an L200. This is made by tibetan monks using nothing but their toes. Only 2 are produced each century. (Only kidding the L200 is provided as a kit by the renowned amateur spectroscopist, Ken Harrison. I also use a Star Analyser on occasion. This is like a filter which has the same effect but at much lower resolution. |
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Fig. 9 - 2 x 10Amp, 13.8V Power Supplies provides all the power I need.
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Fig 10. There are several of these locks for added security.
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Fig.11 - The Counterweight Bar.
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The counterweights are an interesting issue. Astro-Physics can provide absolutely beautifully finished counterweights made from stainless steel for their mounts. However although these are not overly priced when shipping of such a heavy item and import taxes are taken into account these end up costing over €200 each. Therefore I got my counterweights made up at a local machine shop and even made some myself on a lathe. Of course these are not as shiny and good looking as the original astro-physics ones they end up costing only about €40 each. I prefer to invest money where it makes a real functional difference. I prefer to spend the money that I would have spent on these weights elsewhere. At the end of the day its a personal choice but thats my take on it. |
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Fig 11 - Close Up of a roof Roller. There are four of these.
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Fig.12 - Me and Carol in the observaotry Image: Press Association.
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Fig.13 - IP Camera for security and Monitoring
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Fig.14 - Sandwiched Rubber helps minimise vibration from passing trains.
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So what do I use all of this equipment for anyway? There are a number primary areas of research done at Raheny observatory. The main function is surveying the sky for new objects. I just love discovering stuff! To date I have discovered 2 main belt asteroids, (215016) Catherinegriffin (named after my late mum) and 2009 FV19. Also in 2010 I was lucky enough to become the first person to discover a supernova from Ireland.
While not looking for new objects I spend a lot of time monitoring existing objects such as near earth asteroids which might be potentially dangerous. Confirming the discoveries of new ones and follwing up on well know ones helps the astronomical community to determine if there is an impact threat at some point in the future. Another area of research is spectroscopy. I have described this process previously. Sometimes I just like to take nice pictures of the sky for no other reason than aesthetics. However time available for this is quite limited.
Moving forward I have mentioned motorising the roof will be a priority, adding automatic weather sensing equipment will also be done. I cannot risk getting all of this equipment caught in a rain shower.
Anyway I hope you enjoyed this tour of my observatory and equipment. If you have any questions please us the contact us section of the website to get in touch.
Dave Grennan - 25th July 2010
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