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Artemis285 CCD Camera
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There are many new and exciting tools coming available to the amateur Astronomer in the past few years. The area of astro-imaging is one area where these tools have advanced in both a technological and affordable manner. The Artemis series of astronomical cameras is certainly a part of this astronomy revolution. I have had an opportunity to use and review an Artemis285 camera. Here are my findings and thoughts.
First here are some basic specifications of the camera. I reviewed the Artemis285 Camera – one of several Artemis cameras in the camera line:
Characteristic Published by Artemis My Comments
Description 16 bit Monochrome
Format 2/3 inch 10.2 x 8.3 mm
Pixel Size 6.45x6.45um
Read out noise 8 electrons
Dark Current less than 0.01 electrons per sec
Estimated well depth 32000 electrons
Binning Up to x4 independent x and y Actually up to 8x8
Flexible subframing Yes
Read out Speeds
Full frame high quality 11 seconds I found 14 sec
Full frame high speed 6 seconds I guess this means 2x2 bin
Subframe focus update <1 seconds
Dimensions (box envelope) 147x77x77 mm (WxHxD)
Interface.. T-Thread or M42 (F)
Weight 0.620 Kg
Interface USB 1.1
Cooling Peltier and Fan (unregulated)
Power Requirement +12 Vdc and +5 Vdc
Control/Guide Port 6-pin RJ-12 style (F)
Control/Guide Port 6-pin RJ-12 style (F)
provided by Artemis
Image provided by Artemis
Image provided by Artemis
Interesting and Notable Features:
Camera. The first thing that is noticed is the unique case and shape of the camera. The designers explained to me that the design goal was to minimize camera depth dimension so that it would not interfere with the fork frame or wedge mounted fork style OTA mounts. I have a GEM so I could not appreciate (or test) this design feature. This feature may be of interest to those astronomers with such fork mounted equipment such that there would be no worries swinging through 90 degrees declination.
The case is also made of a milled aluminum with cover. This is a substantially robust case. I feel like I could drop it off the mount without ill effects. (I did not attempt this test.) The downside is that this camera weighs about 620 grams. This is more than twice the weight of the comparable Starlight Xpress camera.
The designers apparently were looking for a robust design in more than just the case. This philosophy is evident in their electronics as well. In the designers words….
“Throughout the project we have aimed to use current, tried and tested hardware rather that the latest bleeding edge approaches. This playing it safe has probably prevented us getting bogged down in ‘novel’ problems and also allowed us to use more cost effective components. These choices are particularly evident in the choice of readout speed of the camera’s CCD. Its fast compared with the old parallel port cameras but relatively slow when compared to USB2 offerings from SX and SBIG. However by not chasing readout speed as a main goal it has allowed us more leeway with the components optimized to image quality.”
One of the first things a user will notice is the slow download speed of a full frame 1x1 bin 1392x1040 pixel image (my system was about 14 seconds). The designers did employ an apparently unique readout system. In simple terms, a CCD readout consists of precharge level and a data level. The difference of these two signals is the desired image data for any given pixel. Traditional methods store a precharge level on a capacitor in hardware and then take the difference with the data level in an amplifier in hardware. The Artemis camera reads both levels into the camera’s processor and takes the difference in camera software. This method eliminates a hardware stage in the camera and potential additional noise or error. It is the added A/D readings that impact download time and not the USB 1.1 protocol. Does it work? Well I really don’t have any comparative basis to other 16 bit cameras. But I can say that this camera’s output does respond well to substantial histogram stretch and gamma while keeping a smooth and consistent image – well beyond anything I have experienced with the most sophisticated webcam modification.
Capture Software. Artemis provides a driver for camera operation with a PC. Driver and capture software is for Windows XP and operates on Windows 98SE. Artemis Capture is the operating application for capturing images. There is also a Maxim DL plugin and Astroart3 plugin. I used the Artemis software on a very minimal Windows 98 SE system with a very 450Mhz PIII and 192Mbytes RAM and did not have an opportunity to use the Maxim or Astroart plugins. This PC system does operate a PCMCIA USB card in order to operate two USB cameras.
Artemis capture is a simple, uncomplicated program that has all you need to target, focus, your object and capture images. Its installation consists of copying a 100KB (approx) EXE file to the desired program folder and launch. It has settings for exposure, binning, visualization of the downloaded image (stretch, gamma, negative), zoom and pan controls. There is a centering reticule for targeting and a basic FWHM focus tool. Files are saved in 16bit FITs format. Some flexibility is provided for the fits header – the user can input “Object”, “Telescope”, Observer” text. Artemis Capture automatically puts exposure time, date, pixel size and binning data in the header. Finally there is a “Night Vision” check box to redden the screen and a “Correct Aspect” check box (to show correct aspect on non-square binning such as 2x1) There is a sequential auto-save for sub-frame sequences. It is a basic tool with all the necessities; it does not have controls for scripting, auto-focus, filter wheel control etc.
There were no difficulties with a straightforward installation. Operation of the Artemis Capture program is intuitive and one feels comfortable with it from the first launch. This application seems to follow the same design concept of the camera – keep things simple and functional. With my minimal PC system there was smooth operation even with multiple programs running while operating the camera in capture mode. Two instances of Excel, The Sky, two instances of K3CCDTools2 (one operating an LE guiding camera), one instance of Word and Artemis Capture all operating at once was not an issue. However, if the camera lost power after Artemis Capture was started, it needed to be restarted (so don’t unplug the camera power). Since Artemis Capture boots up in a second or two this is not a problem.
Judging a Camera by its Pictures:
I had the opportunity to make several images with the Artemis285 camera and Capture and loved the experience. My background and experience was with Long Exposure webcams. I found that while these webcams can be very effective observing and imaging tools, I was getting about all I could from them and was not going to get any more. The Artemis285 appears to be a pleasant and effective step up.
I mostly do remote observing and imaging; my equipment is small and portable (C8 and Megrez II on a GEM). I am battery powered for my observing and imaging. The Artemis285 works well from a 12V Lead Acid battery. However, it does require 5 Vdc for the Peltier cooler and any prospective user must take this into account. My battery systems also includes a variable regulated output that I could set for 5 Vdc so this was not a problem for me – it might be a challenge for other remote astronomers not so equipped, but easily overcome with a purchase of a small DC to Dc 5 Vdc regulator. Beware though; running this camera without the Peltier cooling operating is not an option, the resulting dark frames are significantly degraded.
Here are some of the images obtained. Click on each image for a full resolution version (150 to 200 KBytes). More of my images as well as more detailed description of the telescopic equipment used can be fount by navigating the appropriate links on http://jthommes.com/Astro/:
M13 Hercules Cluster (Click Image for Hi Res)
M101 Pinwheel Galaxy (Click Image for Hi Res)
M8 Lagoon Nebula (Click Image for Hi Res)
M27 Dumbell Nebula (Click Image for Hi Res)
As a prospective buyer of a camera, I would be interested to know some of the details of what to expect from the camera output prior to the processing into a final image. What do the dark frames look like, what do the raw frames look like and so on. The camera output ranges from 0 to about 56,000. So note that the image does not saturate at the 65,535 level you would normally expect from a 16 bit readout but instead at about 56,000.. The readout noise level for a short 0.5 sec dark exposure ranged from 222 to 566 with an image background average of 284. Ambient Temp was about 12C (CCD with cooling was expected to be at –8C). So these two pieces of information give you the range over which useful data is presented ( roughly 284 to 56,000).
Here is a dark frame and a raw H-Alpha exposure frame from the M8 image. The exposure time was 240 seconds. The actual image is linearly stretched to display 0 to 3010 range of the 65,535 16 bit range. Of course, the raw data image is blown out in the object core, but the raws are presented for comparative purposes. Finally presented is the dark frame stretched to display 0 to 1003 of the 65,535 16 bit range. The images are jpg compressed and are not suitable for data manipulation, however, the do give a reasonable visual impression of the results to be expected. Please take into consideration the extreme stretch used to illustrate these dark frames.
This information should give the reader a reasonably good idea of what to expect from the Artemis285 Camera Driver and Capture application.
240 sec Dark 0-3000 stretch (Click Image for Hi Res)
|240 sec Dark 0-1000 stretch (Click Image for Hi Res)|
240 sec M8 Raw 0-3000 stretch (Click Image for Hi Res)
Other Items and Summary
The Artemis camera at the time of this review is availableas a complete camera and in in kit form. In the kit you get assembled, tested circuit boards, case components, CCD etc. What you need to provide is some wire some solder and some labor to assemble the various parts. You will need to perform a camera set up which will also require a multi-meter. At the time of this review, the Artemis285 was priced at £765 pounds. More information is available from the Artemis site at http://www.artemisccd.co.uk/Artemis_Cameras.htm
If the idea of assembling your camera from a kit is a bit intimidating for you there is another option of buying this camera in a complete ready to go form from ATiK Instruments. The ATK-16HR is available for 1,700 Euros. More information is available at the ATiK site at http://www.perseu.pt/en-us/dept_186.html. Additionally, the ATiK camera comes with a high quality Pelican Case.
Either way one chooses these prices are at attractive levels for this midrange 1.5 Megapixel cooled monochrome astronomical camera.
Now for a summary…
What I Like:
There is a lot to like about this camera and many functions and features are attractive. I was not able to explore all of the functions, but these are the highlights that struck me the most.
1. Rugged and simple camera body that appears that it would take some unintended abuse.
2. Simple, intuitive Capture application with a minimum of overhead imposed on the PC.
3. Nice short stand off distance from CCD to mounting interface. This leaves maximum flexibility to employ focal reducers at different speeds.
4. Excellent data results at low pixel intensities – responds well to stretching and curving.
5. Excellent consistent results on dark frames with very low dark and readout noise.
6. Full flexibility on binning and camera exposure controls. Full flexibility on visualization controls of the downloaded image.
7. Full flexibility with sub-frame sizes for focusing or object centering.
8. Balanced mid range features on CCD size, resolution and sensitivity. This is a logical step up for a former Long Exposure Webcam, SAC, or ATiK camera user.
9. Upgradeable camera firmware and expansion port and control port for future feature enhancement.
10. These and other features for an attractive, affordable price.
What I don’t like:
There is not much to not like about this camera, but in the interest of a balanced review, here are some of the items that while certainly not showstoppers, are still notable.
1. Long download time. One should understand that this was traded off for image quality. Still one notices it and wishes it was shorter.
2. Camera weight at 620 grams is noticeably heavier than a former webcam, SAC or ATiK user would be used to. Again one realizes this weight is a consequence of the ruggedness of the camera and effective cooling of the CCD.
3. The Camera requires two supplies - 12 Vdc and 5 Vdc.
Bottom line for this camera is that it is a winner and should be particularly attractive to the mid level imaging astronomer who is stepping up from 8 bit cameras or the more experienced astronomer looking to move into CCD imaging. Its hard to imagine a user who could not be very happy with this camera.