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Mini Observatory

Mini Observatory is the name I have given to a very small but functional and fully automated terrace observatory.

 

The project arose as an idea for the use of an old 8" tube disassembled from an LX200 to operate in an automated way in different functions based on planned astronomical photography.

 

The assembly is supported on an EQ5 mount and the design has been made based on these requirements:

 

  • That the assembly of the mount and telescope is deployed and stationed permanently on the terrace with some system of protection against water and wind.

  • That the set occupies the minimum possible given the restrictions of space on the terrace. That the protection works with an automatic opening and closing mechanism

  • That the whole is controlled by a mini computer and is completely autonomous and remotely controllable

  • That during the manufacture the basic elements have a size that allows them to be transported through the doors of the house to make on the terrace only the assembly

 

The design is based on a very light and minimalist structure of aluminum profiles that allow to cover the frame (without the option to fit a person inside so it is not a suitable solution for visual astronomy) and that supports two shovel-shaped structures very light and that are closed one on another to protect to the set of the rain and the wind.

 

The aluminum structure is shown in the following photo:

The shovels are structures with three pieces of white expanded PVC joined together by two threaded bars of metric 10, which at their ends hold two cuts of aluminum profile that allow fixing the side panels with screws. The largest piece of expanded PVC is folded with heat to give the whole shape of the shovel. In the lateral joints, wood has been used for fixings with 8mm bolts. The metal part seen in the center is not part of the structure of the shovel but is the support that will pull the opening and closing mechanism. The opening and closing operation is done by pivoting on the 4 corners (a reinforcement with metal washers can be observed).

In the following photo you can see the observatory assembled with the mount and the telescope inside. The two  shovels are practically identical, only the difference that the one on the left (north shovel has a protrusion that is mounted on the other shovel (south shovel) to make the closure and correctly protect the whole water. The shovels are attached to the structure by two aluminum plates of 30mm wide and 2mm thick on each side that allow the movement of opening and closing and are designed so that when moving the shovel there is at the same time a movement of displacement and height. That is, when the shovel opens, at the same time it lowers and moves outwards, and when it rises, it makes the opposite logically.

The set when it closes leaves the telescope, camera and other elements protected from water and wind, although it does not isolate from the outside temperature, which I have not considered necessary. Only when the system is not going to be used for a season, can the telescope and mount be holstered before closing the mini observatory. The set is oriented north - south.

 

In the following photograph the closed set is shown and it can be observed how the north shovel mounts with a projection on the south shovel for the correct protection against rain.

The opening and closing of the mini observatory is done with a MaxDome II control board acting on two electric spindle actuators. The control board makes the opening and closing in two phases: in the closing the south shovel moves first and when it has reached the end, detected by a limit switch the movement begins the north shovel, in the same way until it detects a limit switch. In the opening is the opposite, first the north and when it reaches its final position moves the south shovel. Doing the maneuver in two phases has several advantages, on the one hand we do not overload the source with the simultaneous consumption of the two actuators, and what is more important, we guarantee that in the closing the north shovel, which carries in its upper part a supplement that must be above the south shovel for a correct closure, comes after the south shovel is in position. The following video shows a part of the closing process:

In the video you can see how the telescope is horizontal. Given the small size of the mini observatory, the normal position park with the telescope towards the polar one is not possible to use it, due to the height. To do this, it is necessary to define a park position in the mount with the telescope horizontally. In the video the park position is horizontal with the telescope to the south in the west, but still another combination can be used. I have finally chosen north - west since I have a preference to observe in the north because to the south is the wall of the house that limits the altitude and from that park position there is less movement to reach the objects to be photographed, and consequently less error in the first plate solving.

In the lower part of the structure there is a enclosure with weather protection where the entire control system is housed, which includes:

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  • Single phase protection

  • 12VDC power supply

  • Intel NUC Mini Computer

  • MaxDome II control board

  • USB hub they connect to:

    • EQ5 mount

    • SBIG ST8XME camera

    • SX guidance camera

    • Moonlite focuser

    • MaxDome II

 

The cenclosure already sealed and is also protected in that position of water and sun.

Despite the small size of the mini observatory, once opened, the mount has total freedom of movement without any restriction to point to any part of the sky.

 

The open shovels offer some limitation to point at low altitudes, but in reality the walls of the terrace and adjoining buildings impose higher limitations .

 

The legs of the mount are independent of the structure, in fact in the photo it can be seen that the north leg of the mount is outside the structure. Being independent elements, once the station has been put into station, the movement of the structure will not touch it and the system will remain oriented and stable.

 

The structure can be fixed to the floor of the terrace or simply marked with a marker in case of accidental displacement, since being very light, tripping over it can make it move.

The set is completely automatable by software.

 

In the mini PC it has been installed:

 

  • Maxim DL for control of cameras (main and guidance)

  • Autofocus for focused control

  • ACP DC3 for the automated control of mediating operations scrips

  • VNC server for remote control of the equipment through WIFI

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