After 10 years with my SBIG ST-8300M, I have finally upgraded. Despite its quirks, halos and spikes around bright stars, bad columns, and incredibly slow download times, this camera has performed admirably well. It has taken some of my best astrophotos to date, and managing its idiosyncrasies has taught me more about image processing than I ever thought I would know. In the time I have had it, this camera has taken on dripping humid winter nights, wonky power at remote sites, suspect USB cables, being dropped, and has just kept going. So, before I move on, I wanted to take a moment to celebrate this aging, but still very capable camera with a teardown and a close look at its innards.
I bought my ST-8300M in 2015 second hand. The seller told me that it was a very early version he had purchased new in 2010. This one is the ST model with the extra slow download times. It takes about 7 seconds to download a 1×1 binned full frame with this camera. Frame and focus is not a fun exercise with the ST-8300M. (The STF model came along a later and reduced the download times to about 1 second.) It did come with a nice SBIG branded case though, and a power supply that has survived the years without a single hiccup.
The camera came with the FW5-8300 5 position filter wheel that takes 36mm filters. I got really lucky one day and found a spare FW5 carousel selling on CloudyNights and snapped it up. This allowed me to have one carousel for RGB imaging and another for narrowband imaging, and swap them out as needed. Otherwise, I’d have to change the individual filters each time I wanted to switch.
Below the filter wheel is shown with the cover that holds the filters in place removed. 5 hex screws hold the cover in place. The wheel takes mounted or unmounted filters and includes rubber gaskets for the unmounted filters. The wheel is shown with mounted RGB filters in positions 1, 2, and 3, an unmounted luminance filter in position 4, and an IDAS LPS-D3 (36mm/2.5mm/unmounted) filter in position 5.
The filter wheel unit shown in various states of undress. The first photo shows the complete FW5-8300 unit as it was sold. To install the filter wheel, the original front plate of the ST-8300M is removed and the FW5 is bolted directly to the camera. (middle photo) The last photo shows the filter wheel with the carrousel in place and the cover removed.
I also got a Nikon lens adapter with the purchase. However, I had issues with in-focus (the lens needing to be closer to the CCD) with most of my lenses, and I didn’t wind up using it very much. The Nikon adapter is mounted on a “port” plate which then attaches to the filter wheel. The camera has a separate port plate with M42 female threads that I use to connect it to the telescope.
The filter wheel is connected to the camera via a DB9 connector and uses the I2C protocol to communicate. I found this an interesting coincidence as it is the same protocol I use to connect temperature, humidity and atmospheric pressure sensors on my Raspberry Pi based weather stations.
The connectors side of the camera provides a standard ST-4 style guide port connector, the power connector for the 12v 3.75A supply, and the USB 2.0 port for connecting to the computer.
The back end of the camera has the fan for the CCD cooling and a pair of handles which are helpful for moving/slewing the telescope the camera is attached.
When I got the ST-8300M, the camera didn’t even have a dew heater and would frost quite easily. This was introduced in later models of the ST and STF cameras. I reached out to SBIG and their support was awesome. They sent me a dew heater, detailed instructions on how to install it, and some silica packs for the CCD chamber, all at no cost. Great company, and stellar support for a 2nd hand camera that was already discontinued at the time.
The orange/brown rectangle is the dew heater, which is held in place by high-temp double-sided tape. It connects to a jumper on the main camera board. The shutter plate is shown in the open and closed positions. The shutter is super helpful for taking dark frames without having to cover the telescope. It has been very reliable, and it auto-calibrates itself each time the camera is powered on.
Under the shutter is the metal CCD chamber cover, where the glass window for the CCD is mounted. The whole assembly is warmed by the dew heater. The underside of the cover shown in the first picture below. The glass window on my camera was in rough shape due to various cleanings over the years, and I recently replaced it with a spare 36mm unmounted luminance filter I had. It is fixed in place with some high-temp black silicone. Changing the glass was an improvement, and I found that halos around bright stars to be much less prominent. The silicone has done a great job sealing the whole thing together, and the CCD has been frost-free since the upgrade.
The other two images show the CCD chamber with the Kodak KAF-8300 sensor. The KAF-8300 is a 22.5 mm diagonal (17.96 x 13.52 mm) four-thirds format sensor, rocking 8.3 megapixels (3326 x 2504), with 5.4µ pixels at 1×1 binning.
The chamber has a rubber gasket to keep it air-tight, and a metal mask that blocks stray light, and holds the silica gel bag in place. I have replaced the bag several times over the years when I notice dew or frost inside the chamber. Replacing it can be a tedious process. Getting the chamber closed and absolutely dust free can take several attempts. It can also take several days and cooling/warming cycles to get the residual humidity in the camber to be absorbed by the silica.
A few more images of the camera’s guts… The first shows the back of the camera and the NPM PF25 50 ohm motor that controls the shutter. Interestingly, my aging Starizona Microtouch focusers use the same brand of motor. Given the age of my camera and focusers, and the number of cycles they have performed, these motors are insanely reliable.
The middle photo is the Infineon/Cypress CY7C68013A USB microcontroller responsible for sending data from the camera to the computer. I believe this was upgraded in the STF version of the camera, which greatly reduced the image download times.
The third image is the brains of the camera – an Xlinx Spartan-II XC2S50 FPGA (field-programmable gate array) chip. It is responsible for controlling all of the camera functions, from reading the CCD data, to controlling the I2C interface, and everything in between.
Despite all the good stuff, the sensor did have its issues… There are a few predominant bad columns, plus a bunch of less visible ones that have gotten worse over the years. Using good dark and bias frames, as well as dithering has helped to tame the worst of it.
This is a stack of 30, 120 second dark frames at -15C that shows the sensor issues well. However, the biggest challenges I have with this camera are the halos and spikes around bright stars, and how uneven the background is in the final images. I have tried various methods of bias/dark/flat frames, but I always had issues, and it wasn’t until upgrading to the QHY268M that I realized it was an “it’s not me, it’s you” kind of problem.
The images below show how I attach the camera to my FSQ-106EDX4. The first is at native f/5 (530mm focal length), the second is using the CR Reducer 0.73x at f/3.6 (385mm focal length), and the third is with the Extender-Q 1.6x at f/8 (850mm focal length).
Some links and resources related to the SBIG ST-8300M
The official manual for the ST-8300 camera:
https://cdn.diffractionlimited.com/downloads/legacy/ST-8300-Manual_12.pdf
Drivers page for the ST-8300 cameras. (Search for “USB Port Cameras – STF, STX, STXL, STT, STL, ST”)
https://diffractionlimited.com/legacy-product-support/
New product announcement page for the ST-8300:
https://www.atscope.com.au/sbig/ST8300.htm
Spec sheet for the Kodak KAF-8300 CCD:
https://www.robani.ch/KAF-8300ProductSummary.pdf
Data sheet for the Kodak KAF-8300 CCD:
https://www.onsemi.com/download/data-sheet/pdf/kaf-8300-d.pdf
Data sheet for the Xlinx Spartan-II CX2S50 FPGA chip:
https://docs.amd.com/v/u/en-US/ds001
Data sheet for the Infineon/Cypress CY7C68013A USB microcontroller:
https://www.infineon.com/assets/row/public/documents/24/49/infineon-cy7c68013a-cy7c68014a-cy7c68015a-cy7c68016a-ez-usb-fx2lp-usb-microcontroller-high-speed-usb-peripheral-controller-datasheet-en.pdf