Sti All Sky mod

DIY All-Sky Camera using a

SBIG STi Planetcam/guider

The core of the All-Sky system is SBIG's ST-i autoguider planetcam with guider rings and a C-thread to 1.25" adapter ring. The camera was chosen for the following reasons:: Sensitive KAF340 CCD rather than a less sensitive/noisy webcam type CMOS sensor Internal shutter and the ability to take (noise reduction) dark frames. Ability to take very low-noise time-exposures High dynamic range due 16 bit output Image output in a number of formats: .jpg, fits, tiff 8 bit, tiff 16 bit & SBIG native. Fast, i.e less than 1 second for full frame USB downloads. Robust & reliable (manufacturer supported) capture software that allows manual or automated capture of images. Good 3rd party software support
Another key element is Fujinon's C-mount fisheye lens. Very sharp optics, even when wide open. Fast F 1.4 focal ratio Full-sky (185 degree) circular fisheye coverage with a 1/2" sensor.
You'll need a set of these, or at least the 0.89mm Hex (aka Allen) Key to fine tune the focus of the Fujinon lens.
There are 3 small grub screws around the circumference of the C-thread fitting on the Fuji lens. There were set fairly tight by Fujinon, so be sure to insert the 0.89mm hex key fully to aviod stripping the hex-socket, while loosening the grub-screws. Do not unscrew them too far or they will fall out! After attaching to the ST-i, the silver coloured C-thread assembly can then be rotated on its internal thread, to fine-adjust the focus of the lens. The included ST-i software, CCDOPS, when in focus mode, gives very fast image updates and makes focusing quick and easy. Simply inspect the fisheye's image while turning the lens until best focus is achieved. To ensure the CCD to lens distance is perfect, make sure the lens aperture is set to F1.4 while adjusting the lens distance. After you dial in the best focus, re-lock the grub screws.
With the focus nailed, the assembly can be mounted into a weather-proof housing. As the camera has a 1.25" diameter barrel, standard 1.25" diameter eyepiece fittings may alternatively employed to help mount the camera & lens. The SBIG guider rings are an easy solution as they have a 1/4" -20 (photo tripod) thread on the mounting block which can be used to easily mount the camera and rings with a single 1/4"-20 bolt.
Inexpensive 90mm PVC plumbing fittings can be employed to make up the weather proof housing. Due to a lack of a suitable o-ring for the acrylic dome, it was fixed in place using wet-area Silicone sealant. However I wanted the ability to be able to remove the dome assembly. Using a PVC drain fitting and plumber's teflon tape, the fitting now had a weather proof seal, but could be easily removed for cleaning/replacement if required.
The almost complete ST-i All-Sky camera! All that was required to mount the camera rings was to drill a 1/4" hole for the ring assembly mounting bolt, plus a Dremel tool was used to cut a square hole for the mini-usb connector. Parts list so far: ST-i planet cam ST-i guide rings & C-mount adapter Fujinon FE185 fisheye lens 2" 1/4-20 bolt, 2 matching nuts 3x stainless washers Mini USB male/female cable extender Security camera Acrylic dome Silicone Sealant 90mm PVC pipe 90mm PVC drain fitting 90mm PVC threaded end cap & seal PVC pipe glue Total cost of the project was about $US1000.00
The (very simple) internal layout of the housing. Nuts and washers were spaced appropriately along the 1/4"-20 bolt to position and lock the ring assembly in place. A mini-usb male/female cable was used to allow easy external connection of the camera. Silicone sealant was applied internally around the connector for a neat appearance.

Pictured below the completed weather-proof camera housing

First all-night test of the camera below (22mb .mp4 file...may take time to load )

Some operational notes:

After just a few nights use the camera USB connection became very intermittent. Further investigation revealed the mini USB connector had some pin corrosion due moisture intrusion.

Make sure the external USB cable connection is made moisture-proof by encasing the connector with two or three layers of thermal shrink tubing, electrical tape or similar.

As with any fisheye lens, take extreme care when handing the (protruding) Fujinon lens. Any damage to the front element or coatings will almost certainly show in subsequent images.

Dew formation on the acrylic dome as not been a problem to date, as the camera produces enough heat while running to keep the dome clear. That said, cold-climate users may need to add internal heaters to the housing to keep the dome clear.

The camera is too sensitive to use during daylight without stopping the lens down to F16, and even then, the Sun causes significant blooming. It's nighttime performance is however, excellent !! 3 second exposures at F1.4 easily capture magnitude 7-8 stars.