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Artemis 285 CCD camera
Carsten A. Arnholm, October 2005.
Until August 2005, my experience with astro imaging was exclusively webcam/digicam based, learning the techniques and tricks from the QCUIAG group. I started with imaging the planets in 2001 and progressed slowly towards deep sky using first a simple SC1 long exposure modified camera and then a peltier cooled SC3 bw camera. At that stage I was asked if I wanted to try the new Artemis camera. Being always interested in trying new things I was happy to look into it and write a review.
Here, you will find some of my facts and experiences in trying to put this camera to good use. If you came here to find highly technical information about dark currents, "shot noise" and such low level technical issues you may be disappointed, but maybe my general impressions and imaging results will give you an idea of what the potential of this camera is, as seen through the eyes of a user, not a camera builder. If you want to comment on this review, please use the contact information found via the link on the top of this page.
Perhaps it is also worth noting that I am a Norwegian, the language mistakes in this text is not due to the camera :-)
Basic facts
The Artemis CCD camera is a cooled 16bit CCD camera designed and marketed by
Artemis Astronomical, a UK company run by Steve Chambers,
Jon Grove and Arthur Edwards. All of these people are well known from the Yahoo group
QCUIAG, and especially Steve Chambers is
widely recognised for the long exposure webcam modifications that carry his "SC" initials.
The Artemis camera is the much talked about and long anticipated follow up to the modified webcams,
but unlike the SC webcams, the Artemis has been designed "ground up" for astronomical use and can
therefore be considered an alternative also to other "professional" CCD cameras.
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All the cameras in the Artemis series look the same (except for colour), they have a very unique shape. The housing is made
of solid aluminium which also serves as a big heat sink. The camera uses a USB1 connection to transfer images
to the computer.
The only difference between the Artemis models are the CCDs. On the left is
the largest option, the ICX285AL.
This black and white 2/3 inch Sony CCD
has 1392x1040 pixels and 6.45x6.45 micron pixel size. It also features
"vertical anti blooming" and a very low dark noise. There are several other
CCDs options. These vary in size, resolution, colour vs. monochrome, and of
course, price.
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At the time of writing, the Artemis is supplied from Artemis Astronomical only as a kit for the buyer to assemble himself, but
a ready made version is available under the name ATK-16 from sources such as
Perseu.
One of the biggest advantages of the Artemis over webcams is the 16 bit analog to digital converter.
In theory it means you have 65536 levels of grey. However, such things as pre-charge and so forth
reduce the actually number of levels of grey left for your image. Still, compared with the maximum of
256 levels
of grey in 8bit webcams, it means that a much wider range of brightness values can be captured, which is very important for most deep sky objects.
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Camera parts
When in use, the camera is connected to the telescope and has two cables attached, one USB cable for image download to a computer, and one power cable for the camera with fan and peltier cooler. Unlike the review camera shown here, the standard for the Artemis camera housing is to be
anodised in blue or red.
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The camera arrived assembled for review in a box containing the following parts
- 1 Artemis 285 camera with 1.25" adapter installed
- 1 battery power cable with DIN socket in one end, cigarette & small other plug in the other end
- 1 240V AC power supply (minus cable for AC)
- 1 black plastic camera front cover (same thread as 1.25" adapter)
There were some missing items that I simply supplied myself with from a drawer:
- 240V AC cable for power supply (standard PC power cable)
- USB cable for image download (standard 3m USB1 cable)
The power is supplied via the DIN socket on the back side, and the USB cable attaches to the "narrow" end of the camera house. At left you can see the fan at the far left and the special Artemis guideport above the USB port.
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I have not used the Artemis guideport, but I am told that it can be used to control the shutter on a long exposure webcam - support for this is expected to come soon in webcam autoguiding software such as Guidedog. With such a feature it will then be possible to image with the Artemis and autoguide with a long exposure modified webcam without needing a printer port on the laptop.
The 1.25" nose-piece adapter can be unscrewed and reveals standard M42 threads to which old style SLR lenses can be attached for wide field imaging. This is quite attractive as I have several such lenses. Also, by removing
the nose-piece and replacing it with a telescope adapter ring, the big 285 CCD is less susceptible to vignetting,
i.e. image darkening towards the edges of the CCD.
The female M42 threads are found on the inside of a ring that is held in place using 4 set screws. This ring also
serves to hold an optical window in front of the CCD. By removing the ring, it is possible to get access directly to the
CCD should it become necessary.
Artemis Software
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The Artemis is always used with a computer. This is not a stand alone camera like a digicam or a DSLR. The camera is always remote controlled from a PC using an image capture application. Drivers for capturing images via applications like AstroArt or MaximDL exist, but for users who don't own any of these, the "Artemis Capture" program can be used, and that is what I have done.
The image at left shows a screenshot of Artemis Capture. For illustration purposes I have overlayed the
program screenshot with one of my IC1805 images, but notice the IC1805 image is not a 'live' screenshot. To see an
actual live screenshot, click here.
Image download can take up to 11 seconds when imaging with the large ICX285AL CCD, shorter with the smaller CCDs.
When binning is used, download times are reduced dramatically. Also, when imaging in sub-frame mode download times are reduced with the size of thesub frame. One might think 11 seconds is prohibitively long, but with exposure times of 5 minutes or so, 11 seconds is really not a big issue. In focus mode, the update is almost real time.
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Imaging with the Artemis is in many ways dead simple. There are no gain settings or anything like we are used to with the modified webcams. Other than varying the exposure length, you can however use binning to
combine 2x2 or 3x3 pixels before analog to digital conversion to achieve higher sensitivity. To put it simply, the Artemis just counts the incoming photons during the exposure and saves the result as 16 bit FITS files to be processed and tweaked later. The fact that no image processing is going on at capture time is one of the secrets to achieving good results.
Software support
For Artemis a dedicated support forum exists in the
ArtemisCCD Yahoo group. There you will be able
to meet the designers and software developers directly, plus share experiences with other Artemis users. I have
followed the group for some time, and the support provided is excellent. There is also a fast turn-around for bugs
and wishes. New versions of the computer software and camera firmware are downloadable from the Artemis website
as they become available.
Experiences using the Artemis software
After using Artemis 2.08 and 2.09 Capture for a while, I can say it is a stable and fairly intuitive program to use. I prefer "to-the-point" programs without too many "bells and whistles" and this program fits the bill quite nicely. I really don't see a need for much else, but there are some minor things that perhaps could be improved:
- There are 2 sets of buttons in the toolbar that you need to use properly. At first I used
the "Loop" button to capture images, but only after some time I discovered I had not saved
any image files! It felt like shooting images with a film SLR camera without having loaded
any film. The thing is that you also need to tell the program that the incoming files are
to be saved to disk, using the "Autosave" button. This is logical in many ways, but it
seems that many novice users fall into this trap. Perhaps some of the free toolbar space
could be used to flash a "Warning: Not saving images!", or something of that nature.
- The second thing I noticed was how the live histogram stretching worked. As this is a 16 bit camera, and
most objects are very dim, the images have to be histogram stretched so you can see anything (the histogram
stretching only affects the live preview, not the captured files). The automatic stretching did a fair job in
most cases, but the
manual stretching was a bit difficult to use, the slider tended to move too fast. Perhaps a spin control
would be a helpful supplement here, the spin control could be used for fine adjustments.
- I discovered a memory leak at one stage (the software was using up the computer's memory while
running in loop mode), but this issue had already been corrected before I could report it, a simple download
and install fixed it immediately. I have not found other issues like this after using the program for many hours.
As I am a software developer myself it indicates that this program is stable and well written.
- The sub-frame buttons occasionally behaved oddly. I would prefer the sub-frame button to appear pressed
at all times when the sub-frame feature was active, and similar for the full frame button. These buttons would then
be a true radio button pair, pressing one should release the other. Somehow I kept fiddling with this without always
being sure what state the program was in. And finally I could not get into my head that the icon on the full frame
button actually means "full frame" and not "sub-frame", it gives me the wrong association! I would suggest to keep a small red rectangle on the sub-frame button (as today) and simply a larger red rectangle for the full frame button.
- There could be easier ways to access the FITS header editing dialog than having to go via the File menu.
I tend to forget it and end up with lots of frames with the wrong object specification in the FITS header.
Perhaps the current Object name and instrument could be displayed as a reminder in either the status bar
at bottom or even in the program title bar? A button in the toolbar to access the dialog more easily in the
dark is also an idea to consider.
After listing these areas of suggested improvement, it is also fair to mention some of the really nice features
- The live image zooming is excellent. If you have a mouse wheel, you can really zoom in and out quickly and with
the large 285 CCD this is really required, because the CCD resolution is higher than my laptop LCD resolution!
- When you learn to use the sub-frame capture, it is a very nice way to frame the object you are interested in (although using sub-frames for that purpose might complicate the use of flat fields). Using sub-frames reduces
image download times significantly from 11 seconds for an unbinned 285 CCD, down to fractions of a second, depending on sub-frame size.
- There is an essential focus assist feature which is typically used in sub-frame mode. To use it, one performs
a rough focus and capture a frame. Then mark a sub-frame around a star, and set the program in fast loop mode
(without saving frames typically). Open the focus assist dialog and double click the star. The program then
measures the width and brightness of the star as you tweak the focus. Using this tool, one can reach good focus
in reasonable time.
- The "Quick" menu contains shortcuts to common exposure settings and binning options. These are really helpful
when trying to locate a target. Using any of the 2x2 binning options increases the camera sensitivity by a factor 4 and at the same time reduces download times similarly. The price you pay for this is reduced resolution.
My experience with the Artemis software so far is limited to Artemis Capture, but I am looking forward to using it
much more.
Autoguiding required
Coming from a background of using modified webcams, I think it is fair to say that this camera is more demanding of its user, it is more difficult to use than webcams, and autoguiding is a must unless very short focal lengths are employed. This is due to the fact that the camera is a 16bit camera that can take exposures for many minutes (certainly longer than 5 minutes) without saturating. To exploit the camera potential you therefore end up taking much fewer, much longer single exposures than you do with a modified webcam. You should plan for taking at least 3-5 minute exposures and that requires better tracking than most amateur equipment can deliver, hence the need for autoguiding. I found that using my trusted SC3 webcam as autoguider was an ideal solution, and it made me work on my guiding capabilities, with good results. This way, the Artemis
pushed me to become a better imager!
Power and mechanical observations
The "cable with DIN socket" turned out to be a power cable Arthur Edwards had prepared so I could supply power
to the camera from my 7Ah PowerCube battery. This was very nice for portable use. The cigarette plug draws 12V for the camera and fan while the smaller plug draws 5V (but 6V is also ok for the peltier cooler). I could use the camera for about
3 hours before the battery ran out, but more practical is to replace the battery cable and use the 240V AC power supply, which will provide all the needed power. This is of course preferable in a permanent setup like mine.
One thing that struck me immediately when I saw this camera and held it in my hand, was that it was bigger and heavier
than I had thought it would be. The camera dimensions are approximately 145x78mm (x50mm thick), not counting protruding
cables or telescope adapter. The camera without cables weighed approximately 600g on a simple kitchen scale. So using the
camera will have an effect on the weight distribution of a small to medium size telescope. You could say that in this regard
it is quite similar to a digital SLR camera body.
The 240v power cable works just fine, but the cable itself is quite stiff (especially under cold conditions), and the cable between the camera and the AC/DC converter box is quite short, so it could end up hanging from the camera as it did from one of the scopes I used (C14+Paramount). A longer, more flexible cable would be a good thing.
Another area of slight concern for small telescopes is the asymmetric body shape of the camera housing. This introduces torsional bending into the telescope adapter. If a nose-piece is used, there might be some torsional slippage over time if you don't take care to avoid it. The short power cable can add to this issue as it connects to the part of the camera that is furthest from the optical (and mechanical) axis. But given that you are aware of and understand this issue it is not a big problem to handle it.
Some imaging results
The images provided here were captured early in my Artemis learning curve, using different telescope and mounting equipment and under different sky conditions. For example, the August sky in Norway (60N) does not reach astronomical
darkness. I think the results are fairly representative of what an amateur
can expect to achieve given similar equipment. To me the results are evidence
that this camera succeeds with the goal to be a high quality camera for the serious amateur.
Click images for large versions
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NGC 6992 (Veil nebula)
At August 19 2005, Heggedal, Norway.
I put the Artemis 285 to test under the full moon, but for once
my high latitude came to my benefit (very low moon).
Exposure: 3x180s + 7x240s (Astronomik H-alpha)
Takahashi FS60c with Artemis 285 at prime focus and
guiding with C8 @ f3 with Vesta SC3 bw
Mount: Vixen GPDX & Boxdörfer MTS-3SDi controller
Software:
Imaging: Artemis Capture
Guiding: K3CCDTools2 drift explorer (file interface) => MTSca Pro
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IC1805 in Cassiopeia
August 31, 2005, Heggedal, Norway.
Exposure: 9x300sec H-alpha
Takahashi FS60c with Artemis 285 at prime focus and
guiding with C8 @ f3 with Vesta SC3 bw
Mount: Vixen GPDX & Boxdörfer MTS-3SDi controller
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NGC 7635 (Bubble nebula)
September 4, 2005, Persbuhaugen (~850m above sea level), Norway.
Exposure: 10x300s unguided (PEC only), H-alpha, 2x2 binning
Celestron C14 (~4000mm focal length, f/11) on
a Paramount ME
Telescope owner and co-imager: Ståle Kildahl
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IC 5070 (Pelican nebula)
September 6, 2005, Heggedal, Norway.
Exposure: 7x300 sec, Astronomik H-alpha
Takahashi FS60c with Artemis 285 at prime focus and
guiding with C8 @ f3 with Vesta SC3 bw
Mount: Vixen GPDX & Boxdörfer MTS-3SDi controller
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The Sun with active region 10808 in H-alpha
September 10, 2005, Harestua, Norway.
Scope: Takahashi Sky-90IISV
Mount: Vixen GPDX with SS2K
Filter: H-alpha Coronado 60mm BF30
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The Sun with active region 10808 in H-alpha
September 10, 2005, Harestua, Norway.
Scope: Takahashi Sky-90IISV, 2x Powermate
Mount: Vixen GPDX with SS2K
Filter: H-alpha Coronado 60mm BF30
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Update 29. Oct 2005: There is now an Artemis image gallery
with images taken by different imagers using different Artemis models.
Other interesting use of Artemis
The Artemis was made for serious deep sky imaging, but can also be used for other interesting things like for example live webcasts of deep sky objects or solar eclipses. I have done such things on two occasions using software I wrote for quickly processing Artemis FITS files into JPG files for immediate publishing, see my FitsCast program .
On September 20, 2005 I arranged a experimental live deep sky webcast, where I used the Artemis to show images of various deep sky objects live over the internet.
The solar eclipse October 3, 2005 managed to get some Artemis webcast images into the Norwegian national news:
Afternposten
Dagbladet
TV2 Nettavisen
Budstikka (local paper)
Prices and availability
The following are places where the cameras can be bought, either as kits or as complete cameras ready for use. Notice
that this list may be incomplete, but it should give a good impression of the costs involved.
More information
The following sites contain very useful technical information for the Artemis camera, something that especially
self-builders will appreciate.
Review of Artemis 492 by Tom How.
Artemis Beta camera by Martin Burri.
Oct 29. 2005 update: Cloudy Nights review of Artemis 285 by Jim Thommes
Conclusion
The Artemis camera is a very interesting camera with high potential for the serious astronomer, at a very competitive price. It excels as a deep sky camera, but is also excellent for Solar imaging in H-alpha. New owners should be prepared to invest some time in learning to use it, as it isn't quite as easy to use as a modified webcam. It takes some time getting used to focusing with the camera, plus learning how to get the mount to track accurately enough to exploit all the 16 bits. Also, one wonders if the camera could have been made a little lighter, for easier use on smaller scopes (but as I complete this review, it is said that the newest batch of cases are thinner, i.e. lighter).
But the upside of all this is that if you invest some time in it, it pays back with interest in the form of much better images than what you can produce with webcams. If you want, you can build the camera from a kit and save lots of money while also learning to know the camera intimately. Or alternatively, you can buy the camera ready made if this suits you best.
The final words are that I liked this camera so much that I bought it :-) What more is there to say?