This camera was sent out to SRO to be installed on the new 24" RC. Last night was the 1st cleat nite I've had in months it seems to do some testing and I ran into a major issue. Keep in mind I'm not experienced with this camera at all. It was installed on the system and when I tried taking an image last night it appears that the guide camera is set as the main chip camera so in MaxIm 6.40 I went into the camera 1 setup and had two choices, the AC4040 and the guider. I chose the AC4040 and set camera 2 as the guider. Regardless no matter it was always using the guider as the main camera. So several questions come up, is the wiring of the cameras to the computer a possible issue or is it in the setup approach? I'd really like to get this tested as soon as possible but at least this part doesn't require an open roof or dark skies. -Steve
Go to the Camera Control Window Camera 1: [Setup Camera] Camera Model = DL Imaging [Advanced...] This will bring up the list of cameras seen by the DL Imaging drivers. Double Click on the AC4040 in the list. [OK] [OK] Camera 2: [Setup Camera] Camera Model = DL Imaging [Advanced...] In the list, double click on the SC1300. [OK] [OK] Then you should be good to go.
I'm reasonably sure I had it set this way last night. Changing the setup sometimes resulted in program errors and shutdowns. As I just remote connected in and had Sam on standby because my 1st test was to be sure we were connecting everything. On that startup and connection to the cameras I had the same experience as last night with switched sensors. I then turned off all power after disconnecting and had everything bot the main camera disconnected and made connection as expected. Image was as expected and confirmed by the FITS header. Then we tested the filter wheel which responded as expected. Powered everything off, Next connected the star chaser and other connections and powered back on. As a note, we connect via ASCOM Direct to the mount. Powered back on and made connections and it seemed to respond as expected. Attached are the screen captures of the camera configurations. Hopefully this will validate or point to an issue.
The first camera, Camera 1, the main detector, DL Imaging needs to be AC4040 *. The second camera, Camera 2, the guider, needs to be SCE1300 *. The AO is on Camera 2's FIRST sensor. Camera 2 only has a single sensor, so set Camera 2 AO = Sensor 1. Self guiding cameras that have 2 sensors would have the AO set to Sensor 2.
OK I think that part is cleared up. Next question is does the image display always show the image and a identical black square below it normally?
It's reading out both High and Low Gain channels, showing you the low gain below the high gain in one 8k x 4k image. Note that you can play with screen stretch and brighten up the bottom half which is much lower gain, and then it may wash out the top. Camera Control Window - Expose Tab Change the Readout Mode to High Gain Then shoot an image, and you should get a 4k x 4k image. Other tip: The sensor is natively 12-bit = 0...4095. So, saturation is going to be around 3600, and hot pixels would be a maximum of 4095. This is UNLIKE a 16-bit CCD like an STX-16803, which would saturate around 56000-58,000 of 65535. 12 bit x 16 = 16 bit; So if you take the AC4040 saturation of about 3600 x 16 = 57,500 equivalent. Then if you want the camera to give you a 16-bit image, you can change the readout mode to High Gain StackPro; and you have to set the Camera Settings Subexposure time.
One last question, and you've been very patient with me, what is a reasonable cooling set point for this camera? With mys STL-11000 and STX-16803 I typically use -20 year round here in Virginia. With this camera at SRO at altitude of 1405 M what would you aim for? I think these CMOS cameras have less noise inherently but I've never used one before. With this I retire for the night and hope to get some better results in 3-4 hours if SRO is clear and open. Rest of week there is rain/snow.
Start with a setpoint of -15C. The CMOS Active Pixel Sensors heat up a lot during the readout process, and even when idle soaking up photons, the onboard electronics generate heat / logic glow. More aggressive cooling has diminishing returns.
I'll expand on Colin's comments a bit. CMOS cameras will not get as cold as a comparable CCD, because the power dissipation of the CMOS technology is much, much higher. A typical CCD sensor might have a couple of transistors for the readout amplifier. This will generate milliwatts of heat. The clocking electrodes that move the electrons around don't generate much heat as they are passive elements. Compared to a CMOS sensor, these are relatively simple devices. A typical CMOS sensor will have millions of transistors, including amplifiers/switches at each pixel, double-correlated samplers on each column, rows of A/D converters along the top and bottom (typically one per every 8 columns), and output drivers and control circuitry. This stuff all takes power - a lot of it. Typical large CMOS sensors can generate 1.5 - 2.5 watts of heat while reading out, depending on model and operating mode. That is 1000 times more than a CCD. For long-exposure operation it is often possible to partially power down the sensor during integration, but it still generates more heat than a comparable CCD sensor - and as soon as you read it out you are at full heat. So naturally even with a powerful cooler system the CMOS sensor will run quite a bit warmer, as in 10C to 20C warmer. Running a series of short exposures can increase the sensor temperature 10C compared to long exposures. I'll just mention that some camera manufacturers out there aren't terribly honest about their sensor temperatures. It's not hard to figure out that their actual dark current is much higher than it ought to be - this is easily measured using dark frames. Another giveaway is unreasonably low power consumption - it takes more power to pump out all that extra heat.
Thanks Colin. By time I was making any real progress the clouds had moved in and the roof closed (wasn't connected to SRO weather). Bottom line the mount is lost and the scope needs collimation.......
Thanks Doug. Last night while trying to do some mapping I had it set to -5 which seemed to do well and used auto dark. I didn't look to see what the ambient temperature was at the time. Unfortunately there is other "work" that needs to be done before this 24" can be put to work....
It may be obvious at this point that my experience with the STL-11000 and STX-16803 not to mention ST7, ST8, ST10 and so on aren't helping me here much and for some reason the manual was sent to SRO with the equipment so I need to download a copy and print it out for reference here. I appreciate the time and effort you guys have provided. Hopefully I will get some more time on this over the next week. Weather at SRO has been less than ideal.....
You can find the manual under the +DOWNLOADS on the camera page here: https://diffractionlimited.com/product/aluma-ac4040/ Thank you for the kind words.
