KPO

Observatory
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Instruments

The Telescope


KPO's telescope is a 306mm f/10 Dall-Kirkham Cassegrain with a tertiary corrector to give extremely sharp and flat images. The secondary mirror is held in place by a piece of optical glass. This is to avoid the diffraction spikes normally caused by a spider  holding the mirror.
Telescope assembly without drive covers. The glass 'window' and secondary mirror mount.


The Mount

The mount is a German equatorial which, while not particularly ideal either for manual use or automatic use, is perhaps the simplist to build.

A better view of the mount.

This an 18" telescope that we had at KPO for a while doing optical tests before installation in another observatory. It is on the same mount that normally carries the lighter 12". Had no problems at all thanks to the conservative over-engineering.


Still Imaging

This is a Meade Pictor 416 CCD camera (on the back of a 4" finderscope) which we intended to use for field identification in the object acquisition stage as well as some image-oriented science work. The Pictor 416 was chosen because of its SCSI interface which (back in the early 90s) had the benefits of being both fast and standard, as opposed to proprietary parallel interfaces which are useless unless you have the right computer. We are investigating replacing this with a more modern camera with a USB interface.
Meade wouldn't provide the necessary information required to drive the camera from our own software but after a couple of years (during which time the camera did absolutely nothing!) Rick obtained the required information by, um..., other means. As this information would be invaluable to anyone wishing to support this camera in their software this information is provided here. Specifically the format of the SCSI commands required to drive the camera are detailed.

Note that SCSI control of the camera is basically just like a normal SCSI scanner and I'll be buggered if I know why Meade are so secretive about it. It's not like there's any proprietary communication going on.

Download Pictor DIY SCSI technical manual  [16K ASCII text]

This information is provided "as is" with no support or guarantee of correctness.

Despite having a 12" telescope, sometimes it's handy just to use the system as a tracking platform for a film camera!


Video Imaging


A video camera of 80s vintage.

A modern ultra-sensitive surveillance camera works great for astronomy. The camera is dwarfed by the 50mm focus assembly!
Originally we did some experiments with a reasonably old video camera (above left) as it has a 50mm aperture lens instead of the smaller ones that prevail nowdays. Despite its bulk it was, for some reason, easier to mount to the telescope than any other camera that we tried. This is not really the ideal setup for attaching a camera to a telescope since the telescope is effectively a giant lens anyway and should be usable without projecting the telescope's image onto the camera's own lens.

A domestic video camera is actually not that great for astronomy because they are not really sensitive enough for anything except the moon and some planets.
We have been experementing with ultra low light surveilance cameras that usually use Sony's HAD technology. As well as being able to record occultation events this will also be very handy for "looking" through the telescope from across the network. Using this camera we can easily record stars at 10th magnitude and is usable down to 12th while maintaining a 50 field/second rate.

See some work we have done with this camera.
To be useful, video astronomy needs a good on-screen time reference in order to time events. To do this we use our GPS clock (below right and here ), and generate a video on-screen display (OSD) with the UTC date and time to millisecond precision. The OSD board can be seen below left and its display on the 4" monitor. The simplicity of the board doesn't hide anything at all - OSD is as simple as a video sync separator and a microcontroller.

Practical uses of this can be seen on our science  page

GPS video timingstamper. The text near the bottom of the screen is overlayed onto the video by the microcontroller on the PCB.

The GPS clock is at the top of the left pole (the other thing is a rain gauge).


Photometry

Photometrry  used to be the domain of dedicated instruments called photometers but for many applications the CCD camera (in still or motion form) is taking over.

The photometer that we use is the relatively low cost Optec SSP5a photomultiplier tube photometer with Johnson UBV filters. This was a natural progression from the SSP3 that we started off with (the PIN diode version) since no change in acquisition hardware was required. It reports counts in DC mode rather than a direct photon count.