Requirements for CCD Imaging Equipment

John A McCubbin

Introduction

I am sure that this article will get a lot of feedback (can you say flamed ;-) and I'm sure that some will disagree with what I say. The aim of this article is to tell you (sometimes painfully) what you will need to produce quality CCD images with amateur equipment. Since it can be accomplished in a variety of ways, there will obviously be a range of equipment setups that will work. At the bottom end would be a wobbly mount, telescope with bad optics, and the low end web-cam conversion with an uncooled CCD camera. At the high end would be a custom mount, megapixel scientific grade CCD camera mounted into the focuser of a super high end scope costing tens of thousands of dollars. There's a lot of territory in between. The painful reality is that better equipment gets the better images, imaging skills being equal. I want to focus on what I think is the minimum needed for good images, and what will improve on that minimum. That should give those only interested in imaging idea of the feasability of getting in to CCD use. Those past the beginning stages may get ideas for upgrading equipment (if things are going wrong).

If you are really frustrated while reading this article jump to the One Last Note, read it, then return to where you were.

Elements of a solid CCD imaging setup (click on a topic to jump right to it)

• Telescope
• Mount
• Camera
• Computers
• Software

Telescopes and Their Suitability for CCD Imaging

So what kinds of telescopes are best for CCD imaging? Before I answer that, let me say that I am constantly amazed at the images that come from all kinds of setups. Ingenuity can turn almost any scope into an imaging scope, but certain scopes are easier and more flexible. I will also concentrate on popularly available designs, although some are in short supply.

Issues like fast or slow focal length apply only to the type of object you wish to image. Planetary work is usually best accomplished with long focal length instruments with slow optics (larger focal ratios). However, with the proper barlow lens or eyepiece projection setup can turn a fast telescope with a shorter focal length into an instrument capable of imaging planets. The same lenses can extend the focal length of the longer focal length instrument even further, so the longer instrument remains the more suitable instrument for planetary work. Better optics also play a key role in planetary imaging. If planetary imaging is your intended purpose then look for long focal length and slower optics and extend the scopes capability with a barlow or eyepiece projection.

Scopes with faster focal ratios, f/6 and below, will dramatically shorten the exposure time required for deep sky imaging. This range of focal ratio can often be obtained in slower systems via focal reducers, so the option for the usage of one of these is a big plus in the choice of a telescope with slower optical design.

So far the factors I have mentioned come down to personal choice. We're looking for the minimum requirements of scope that will declare it suitable for CCD imaging. Certain telescopes have definite shortcomings in their design or construction that will seriously limit their suitability for CCD work. What are the problems that can arise?

The first problem is backfocus. Most telescopes are intended for visual use. To be suitable for visual use, a telescope must place the focal point of it's optics on the focal point of the observer's eyepiece in order to reach focus. The focal point of the eyepiece is in front of the compound elements contained in the barrel of the eyepiece. In other words, it's at the open end of the barrel that goes down into the focuser. With any camera, the focal point of the telescope must fall squarely on the film plane or the CCD chip, which is back inside the camera, generally the opposite direction of the focal plane of the eyepiece. So for a telescope to work well in CCD imaging, it must be able to focus onto the CCD chip plane. This can be accomplished two ways. First, you can produce a scope so that the focuser has plenty of travel then place the focal point well behind the innermost point of travel of the focuser. Second, you can use lower profile focusers, which work in some cases, but provide much less flexibility in imaging setups.

So which scopes have the better backfocus? Two basic designs have inherently better imaging flexibility, the refractor, and the Cassegrain type scopes (SCT's, Ritchey-Cretian, Maksutov-Cassegrain, etc). Both of these designs typically have a wide range of backfocus. They work well with accessories like color wheels, focal reducers (like having two telescopes in one), and eyepiece projection setups. Newtonian type scopes rely on close placement of the eyepiece to the scope tube to minimize the size of the secondary mirror, consequently they have inherently poor backfocus. That is why you typically see low profile helical focusers offered for newtonian type scopes. In some extreme cases the mirror must be physically moved forward and the secondary enlarged to accomdate the movement of the focal plane away from the secondary mirror, thus adding backfocus to the system. So newtonian telescopes almost have to be specifically designed for photography with a larger secondary to accomdate the backfocus required for a CCD camera and even more if you intend to use a color wheel. All in all refractors and cassegrain type scopes are by design more flexible imaging instruments, but newtonian designs can be made to work.

When considering different telescopes, realize that many newtonian telescopes won't focus far enough back for photography, and almost none of them will accomodate a color wheel and a CCD camera. Test the scope first if you can. Some Cassegrain variants, like some of the Russian Mak-Newts don't have a moving mirror and rely only on a rear mounted focuser with limited travel. These don't always reach focus on a CCD camera, and virtually never with a color wheel.

Another consideration is mirror shift during imaging sessions. With refractors this isn't a problem, since there is no mirror. With SCT's, in particular, it can be a big problem during focusing and when repositioning the scope to very different points in the sky between images. Image shift during the focusing phase can be eliminated by mouting a crayford type focuser on the rear cell of the SCT. These focusers are made by JMI (has one with a digital readout), Starlight Instruments, and Apogee. These three companies make high quality rear mount focusers capable of handling the load required during imaging. Mirror shifting as the scope is moved can't be avoided and when using an SCT, the scope should be refocused in between large scope movements. This is a minor problem, but often frustrating and time consuming. I have seen modifications that seek to solve this problem. One approach that seems to work well is to drill and tap holes in the back of the SCT for epoxy tipped bolts that stabilize the mirror. Gross focusing is done first, the mirror is then stabilized, then final focusing is done with a rear mounted crayford type focuser.

Mechanically the scope needs a solid focuser to be able to handle the load of the CCD camera, cords, and filter wheels. CCD cameras are somtimes heavy. An ST-7/8 with a filter wheel is no lightweight piece of equipment. Add this to the end of an eyepiece projection setup and it's quite a strain on the focuser mechanism. So the scope must have a solid focuser unless the camera is very light.

Then comes the other critical factor that inevitably creeps in - optics. Good CCD images are a result of a steady atomshphere, which you can't control, and good optics, which you can control. Cassegrain type telescopes that are popularly produced offer adequate to good optics and thier cost is very affordable. High end refractors offer optical superiority, in general, but are more costly and often difficult to obtain. In the optics department, you generally get what you pay for and it shows in your images. One often overlooked fact is that when autoguiding (with for example an SBIB ST-7/8/10) superior optics result in superior autoguiding. It's more difficult for the autoguider to track on a poorly focused star.

One more thought on this note. An excellent scope to start imaging with is a high quality refractor (almost any focal length will work). Most beginners overlook this option. There are lots of objects that are suited to this type of scope and if the CCD camera is well matched to the scope, then it will find use even when you upgrade. In CCD imaging aperture is less important that high quality optics and solid mechanical function.

I will finally say, that to get started, it's much more desirable to have a flexible scope than an optically superior, but inflexible scope (poor backfocus, can't use color wheels, etc).

My analysis:

Minimum Requirments: Any scope that will focus on your particular CCD that gives you satisfactory images

Intermediate: A flexible imaging instrument like a high quality SCT with more backfocus - extra points for aperture - extra points for color wheel and focal reducers, both of which add to the flexibility of the setup - Extra extra points for a rear cell focuser (on SCT) to aid in focusing the scope

High End: High end refractor (even if the aperture is small), custom made Ritchey-Cretian or or other Cassegrain variant (Maksutov-Cassegrain scopes are dynamite for planetary work), with focal reducers and proven high quality optics, or newtonian custom made for photographic purposes - Extra points for aperture and better optics (getting very expensive at this point ;-)

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Mounts suitable for CCD imaging

So you just found out that your scope may not have made the High End list? Well, don't put that hanky away just yet. Mounts are probably more important that the scope you use. The expensive truth is that while most telescopes will work, most mounts are poorly suited for imaging. Will they work? Sure, but to get poinpoint stars requires a solid, oversized, well made mount that tracks accurately, guides preciesly, and is critically polar aligned. Tracking error ruins more CCD images than does the optical quality of the scope. (Focus kills even more, but that's human error and can be avoided.)

So what works and what doesn't. The first requirement of your mount is that is hold your scope solidly, without wobble or vibration. Certain mount types are inherently more solid, and vibration free. Fork mounts are prone to vibration, but certainly can work if you don't bump them or if the wind isn't blowing to hard. Tripods coupled with a fork mount make the problem worse. Anti-vibration pads help this some, but will not eliminate the problem. If appropriate measures are taken to avoid vibration problems, fork mounts can work very well and serve as a solid imaging platform.

German equatorial mounts are not nearly as subject to vibration and are better suited to the task of supporting a scope for CCD work. German equatorial mounts made by Astro-Physics, Losmandy, and Mountain instruments have become very popular among CCD imagers. In general, oversized mounts are preferred. This is for two reasons. First, they provide a more solid base upon which to guide. Second, larger mounts tend to have larger tracking gears. A 12 inch gear will track more precisely than a 6 inch drive gear, all other aspects of quality being equal. Counterbalancing is also critical to tracking, so the mount must have the ability to couter balance the scope you mount on it. So don't overdo the mount. A 4 inch Astro-Physics Traveler will barely counterbalance the couterweight shaft on an Astro-Physics 1200 mount (I tried it ;-) and is not a good match. Under the circumstances it's WAY to oversized. On the other hand, a C-14 on a Celestron Polaris GEM would be grossly undersupported and may even break the mount. So match the scope to the mount, and err a little on the oversized direction if you can. You should also think it terms of focal length. The longer the focal length of the instrument you image with, the more accurate your tracking must be. Periodic error or problems with mount orthogonality (axes not perfectly perpendicular) are simply magnified by a longer focal length.

So the second requirement, if long exposure imaging is to be accomplished, is that the mount must track accuarately. Fork mounted SCT's and German equatorial mounts are both capable of tracking very accurately when polar aligned. Larger drive gears in general track more accurately. High end larger gears (Byers' gears are an example of extremely high quality drive gears) provide very accurate tracking for the focal lengths employed by amateur imagers. Current popularly available SCT's come with good gearing in the majority of cases. Watch out for equtorial mounts with small gears and lots of play in the gearing, they won't do. Electronic periodic error correction (PEC) when used intelligently can improve the tracking of any mount and is an added bonus. Mounts that work in the alt-az mode will suffer from field rotation. Fortunately most of these mounts allow the scope to be mounted with a wedge in a true equatorial fashion. This generally should be the setup if imaging is attempted. (Some amateurs are using field derotators, but it is my feeling that equatorial mounting is easier.)

No mount can track well if it can't be polar aligned. So the third requirement of the mount is that it have fine adjustments for polar alignment. This can be time consuming, so the more functional the mount in this regard the more time saved. A polar alignment scope is a HUGE timesaver, so if your mount doesn't have one, a retrofit or upgrade is a very good idea. That will only get you started. Learning to drift align your mount is a must. This can be accomplished very efficiently with experience. If your camera has autoguiding capability, it lets you off of the hook a little bit, but you need to be as close as possible.

Assuming that your mount is solid and well made then the electronic controls must also be considered. Can your mount electronics be integrated with an autoguider? This is a real plus. Can you set variable correction rates (or guiding rates) on the electronic controls. This makes a mount much more flexible with different focal length instruments. My Astro-Physics 1200 mount will implement guiding corrections as 0.25x, 0.5x, and 1x. I use 0.25x when doing barlow or eyepiece projection imaing, and 0.5x for prime focus imaging, and 1x when imaging at prime focus on the piggybacked 4 inch f/5 refractor. These guide rates provide speeds appropriate for the focal length of the instrument being used.

Dobsonian mounts deserve mention here. I've seen them used effectively. The new drive platforms, while not as accurate as an equatorial setup, can work. There are now tracking systems that improve the image quality dramatically. They will provide a solid platform for short exposure planetary or lunar imaging. I've seen beautiful mosiacs of the moon taken with quickcams and a dobsonian telescope. The problem is keeping the image on the chip at high power. This can be very difficult. Adding an equatorial platform improves this quite a bit. For longer exposures this is a must. Anything over 30 seconds or so will show obvious elongation of stars if a totally stationary mount is used. Exposures over 15-20 minutes will start to show field rotation making very long exposure shots impractical without very specialized equipment. My summation of dob mounts is that imaging can be done, if you are really determined, but other mounts are much simpler and much more versatile.

My analysis:

Minimum: Any mount that solidly holds your scope, will accurately track the sky, and that can be polar aligned.

Intermediate: Higher end, very solid fork mounts with larger drive gears and PEC electronics. Solid equatorial mounts like the Losmandy series mounts, Asro-Phyics 400 or 600 mounts (providing the scopes are not to large), and other similar equatorial mounts. Gear size is the determining factor here, not necessarily the quality of construction. Extra points for pier mounting options (better than tripod mounts). Polar alignment scope is a serious benefit for portable imaging setups.

High End: Oversized equatorial mount, such as an Astro-Physics 900 or 1200 mounts, Byers equatorial mounts (larger sizes), Mountain Instruments 250 mount, or Software Bisque's Paramount Robotic mount (not a complete list). Variable guide rates should be a given and the tracking accuracy should be very precise and PEC electronics should be built into the electronic controls. Custom mounts can raise the bar on the criteria for this category even further, but only if you're independently wealthy.

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CCD Cameras

The CCD camera you chose is partially determined by the type of imaging you intend to do and the scope you intend to use it on. Much has been said and written about matching your camera to your scope. Most of these recommendations come from a concern that you match the focal length of your scope to the pixel size in your camera, rarely is the field of view of the camera considered. I feel that this is like buying a 35mm camera without considering the type of lens it has on it. You need to fundamentally understand the field of view you are going to get from the camera you buy. This is, in my opinion, one of the more important considerations you should make. Before you buy a camera you should read and understand the article on field of view calculation. I'll discuss this more later in the article.

With regard to matching your scope to the pixels in your camera, it is largely recommended that a good starting point for deep sky imaging is have your camera sample around 2 arcseconds of sky per pixel. For planetary imaging a sampling rate of 0.5 arcseconds per pixel is recommended.

The 2 arcseconds/pixel recommendation is based on the Nyquist sampling criterion, which states that an original signal can be recovered without any loss if the samples are no larger than half the size of the finest detail in the signal. (Harry Nyquist was a mathematician with American Telephone and Telegraph Company.) Assumptions regarding average seeing conditions, star size, and telescope optics to produce the recommended starting point of 2 arcseconds per pixel. Realize that this is an average ideal matching. It is not exact, and I personally break these rules often ;-) You have to decide what you give up when you do.

When I oversample (more pixels per star), it is in an effort to image a brighter object in more detail or to created a framing of the object that I find pleasing. Planetary nebulae like the Blue Snowball and the Saturn nebula are examples where this is necessary. When I want to make my CCD camera perform much like film in it's scale, I image widefield at mid resolution through a small instrument and grossly undersample for deep sky work. True I image fewer stars, but how many do you need? I get the image I want on the chip and if it looks okay, well, I'm set. I would use the sampling criterion for a good starting point, but don't base your whole decision on it. If your intention is scientific measurement of stars, then you'd better follow this recommendation closely.

Binning the CCD chip can also change this criterion. My ST-8 has 9 micron pixels, which are near optimal to image with my Astro-Physics Traveler (4 inchf/5.6) or my Takahashi FSQ106 (4 inchf/5). I can then bin the chip 2x2 to effectively change the chip size to 18 microns nicely matching the Astro-Physics 180EDT with it's focal length of 1620mm and even the C-11 matches the 18 micron pixel size fairly closely. Planetary imaging with a 1.8x barlow at full resolution produces the 0.5 arcsecond per pixel resolution desired for planetary imaging. So binning can make a camera more versatile in its usage among different telescopes.

One other consideration is that total pixel determines the size that the image appears on your computer screen. My ST-8 has a chip that is 1530 x 1020 pixels. At full resolution, the image looks quite large and extends beyond the limits of most older computer monitors. Binned 2x2 the image is 765 x 510, an image size pleasantly displayed on virtually any monitor. My goal is most often to post my images on the internet (the premier medium for CCD image display) so I sometimes bin the chip if this is my only goal. My software also allows me to select the central half of the chip at full resolution producing a 765 x 510 image sampled at 9 micron pixel size. So software can change the size of the image and this flexibility is made possible by small pixels that can be binned. Chips with larger pixel sizes lose this flexibility.

The second consideration is the area of the sky covered by your chip. This is very important, especially with long focal length instruments. It is very informative prior to plunking down money for a camera to find out it's chip dimensions and then to calculate the exact amount of sky that it will cover. You should then look up the size of certain objects (pick a few globulars, a few galaxies, and a nebula or two) and see what will fit on your chip. The formulas for calculating this are in the article Field of View Calculation for CCD Imaging in the CCD techniqes section of this website.

An example of this exercise is to find out what will fit on the chip of my ST-8 with my Astro-Physics 180EDT refractor. The field of view coverage is 29.33 x 19.44 arcminutes of sky. Will M51 fit is this? How about M-13. Well, if my The Sky software from Software Bisque is correct, then M51 at 11.1 x 6.9 arcmintues will be nicely framed with a clear field of surrounding stars. M13 at 16.6 arcminutes will also be framed nicely. M8 at 90 arcminutes in width will only be imaged partially and be a better match for the Takahashi FSQ106 with it's field of view of 93.02 x 61.88. Images in the gallery section will clearly show how important this is in planning your camera to scope match.

The last issue is autoguiding capabililty. Santa Barbara Instruments Group reigns supreme in this area (it has something to do with a patent on the technology ;-) with it's ST-7, ST-8, and ST-9, and ST-10 cameras. These cameras have a second chip built into the camera used for autoguiding. Starlight Express has developed the ability to guide off of the imaging chip, and I have seen some great images using this system. The new LiSSA autoguider is now on the market. Almost any camera can be autoguided using this second camera. Guiding with a guide scope can be used as a last resort, but be warned, flexure will be a problem. CCD cameras are very sensitive and any flexure in the system will be noticed unless the scopes are mated very rigidly.

Autopguiding is important because long exposure imaging will almost always produce a superior signal to noise ratio over a track and accumulate integration. If you want your pictures to look good, you have to expose for a longer period of time, especially through longer focal length systems (like mine). To accomplish this high signal to noise ratio in your images, you must guide your telescope with an autoguider. If that autoguider is built into your CCD camera, it acts like an off axis guider and guides at the same focal length as the imaging instrument. If a guide scope is used, and the focal length of the guiding instrument is less than the imaging instrument then the guiding can't be as precise, consequently the star images will not be as round nor the image as sharp. You can use a guide scope of longer focal length than the imaging camera very successfully. I image through the Takahashi FSQ106 for the wide field and guide with an ST-4 through the AP180EDT. This acutally improves the guiding of the images and produces VERY round stars. So don't be afraid to use a guide scope, make sure it's at a long focal length.

Unguided images will directly reflect the periodic error in your gear and any mistakes in polar alignment you have made, often with surprising (and disappointing) accuracy!

Outside of these factors, there are many CCD cameras out there and I don't pretend to be an expert in any of them. The principles I have laid out above will apply, so check those camera specs and see how they match your scope and what you intend to image.

My Analysis:

Minimum: Any CCD camera that will produce an image. A converted Quickcam (lots of websites on this out there). An ST-4 that is primarily intended for autoguiding, but will produce an image. Converted security cameras from electronics warehouses.

Intermediate: Small to medium sized chip cameras without autoguiding capabilities. Don't cover as much sky, but provide excellent images

High End: Autoguiding camera like the SBIG ST-7/8/9/10. Extra points for the more sensitive chipsets, Large format cameras with big chips, even if they don't atuoguide. Extra points for Apogee (and other companies) front illuminated cameras (SiTE chip cameras - usually very expensive). Best buy for the money (my opinion only) - SBIG cameras. Dedicated planteary cameras with small pixels specialized for planetary imaging probably apply here - Starlight Express cameras with smaller pixels are especially nice.

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Computers for CCD imaging

Computers should be considered from two perspectives. First is the computer required for image acquisition. The second is the computer requirements for image processing.

For image acqusition, almost any computer will work. I've used everything from a low end laptops, to the computer I currently use that is networked via fast ethernet to the base computer in the control room. All the computer has to be able to do is display the image in at least a crude fashion for centering and display the numbers for focusing the camera. It needs enough hard drive storage for the nights images and some method of transferring those images to the processing computer. My current image acqusition computer is a Athlon XP 2.8 GHz with a 120 GB hard drive, 512MB Ram, Nvidia GeForce 4 video card, DVD/CD-RW combo drive, and an ethernet card. My monitor is an old Princeton 17 inch analog monitor. I prefer an CRT display over an LCD screen because it has a wider range of brighntess. The final decision in focusing (for me at least) is how the stars actually look! Consequently, the CRT monitor is important.

The processing computer is another story. I would go for as high end as I could afford. Here, most computers will work, but will they work as efficiently and handle the memory load of processing multiple large images without crashing. I would also recommend the best monitor you can afford, then calibrate it using something like Photoshp's gamma adjustment program.

Specs here are almost irrelevant as the standard changes almost every three or four months. Just to satisfy your tecchies out there, I currently use an AMD 64, 1 GB RAM, Nvidia GeForce 6800 256 MB video card, twin 300 GB hard drives, gigabit networking, and a 16x DVD-RW. My monitor is a Samsung SyncMaster 213T monitor. It's a 21 inch flat panel monitor that has excellent brightness scale and just about the right contrast for processing.

The important factors here are the processor speed (I'm impatient), hard drive capacity (I keep copies of the images on two different hard drive partitions), CD-RW capacity for archiving images, and the ethernet card for file transfer and networking. The video card does allow fast image processing. Leser hardware only makes the process slower. It's not a fatal flaw.

My analysis:

Minimum: Any thing that'll run your image processing and capture software (you don't have to have two computers).

Intermediate: Separate image acqusition and processing computers. A laptop and a desktop work well for this. Ability to transfer images via zip drive or ethernet and an archiving method (DVD-RW or CD-RW). Suitable monitor for image processing and a CRT for image aquisition.

High End: Separate image acquisition and processing computers one with CRT based monitors and ethernet for control of the imageing computer and image transfer. Lots of ram, fast large hard drive, and a nice DVD-RW for image archiving. Remote control software to allow control of the imaging computer from the processing computer (more on that in a later article) is a handy touch. I also run a linux raid fileserver to archive everything that's critically important, these are cheap and extremely handy. You just have to know how to build one.

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Software

Here again types of software fall into two categories - image acqusition software and image processing software. There are some packages that do both (MaxIm, CCDOPS, CCDSoft), but others, like Photoshop are for processing only. Even the software packages that will process and capture images don't satisfy all of my processing needs, so I find I almost always use the different packages for different purposes.

I do not claim to be an expert on all of the software packages available, but I will describe the ones I use and how I use them and what I feel the minimum needed requirements for software should be.

First you have to be able to acquire the image. The camera you buy probably has the image acquisition software included with it, so you may not have much choice. At a minimum you must be able to get the image from your camera to the computer. At the high end you will like the automated capture routines built into the better software packages and focusing aids that make reading that brightest star a little easier.

MaxIm has an optional CCD control module that allows you to control almost any CCD camera made. It is quite capable and has handy sequencing routines that work well when taking multiple exposures. It has nice focusing aids and can control the guiding chip in the SBIG cameras and most features of all the higher end cameras.

CCDSoft (Software Bisque) will work similarly, but currently has fewer cameras supported. Plus the version I have I really don't like very much - nothing personal SB. I understand it is being totally rewritten and will become SBIG's official software to replace CCDOPS (my old favorite). This will help.

For the SBIG cameras CCDOPS is my hands down favorite. MaxIm has fancier routines in it, but CCDOPS works like I think, especially when my hands are cold ;-) I may keep it over the newer software unless the improvements are significant. It's autoguiding setup and implementation routines are what sells it to me. I get the pictures I want with it and that's what makes me happy. It doesn't do sequences as easy, but otherwise is logically laid out and a very capable software.

Processing software is needed to calibrate and manipulate the image to be more visually appealing, and extract detail from the image you've taken. Since a monitor only displays around 64 levels of gray and your 16 bit camera stores 64,000 levels of gray, there is a lot of open territory for image manipulation. You, and you alone, decide which of those 64,000 levels of gray are represented in the 64 levels of gray you see.

At a minmum you need a processing software capable of dark subtracting, flat framing, and bias frame subtracting your image. Even most of the camera control softwares do this. Basic screen stretching is also well within the capabilities of the capture softwares. Things like pixel math (addition and subtraction of images) is also included.

Image alignment usually isn't included in the image capture software packages. Neither are the fancy manipulation routines like Gamma Stretching, Digital Development and Maximum Entropy Deconvolution.

Hands down my favorite for intial dark subtracting, flat framing, and compositing is MaxIm DL from Cyanogen productions. It goes well beyond just the simple capabilities of stretching and calibrating the image. It has built in alignment routines (best I've seen) that allow alignment of multiple images to the neares 0.1 pixels. It has all the usual filters (low and high pass - and in different levels of intensity) with options to base them on different mathematical routines. It has a nice gamma adjustment routine, very customizable Maximum Entropy Deconvolution routine, and a very nice Digital Development routine. All in all, I think it's tops.

Final processing software is highly personal. I personally think Adobe Photoshop is the standard in general image manipulation software. I use it to finally process the image by making fine level adjustments, occasionally removing the blooming from a star, calibrating the color of an image, and a long list of final adjustments to the image. It just adds a final polish to the Image. It now can work directly with 16 bit color images, which is a nice touch when considering ccd astrophotography processing software.

I also use it to LRGB combine images. For this purpose, it's perfect and the preferred software. In fact, I'm not sure how to do it with any other package.

So.....

My analysis:

Minimum: basic image capture software that comes with the camera as long as it perform the basics of image processing like image calibration (dark subtraction and flat framing) and stretching.

Intermediate: add to the basic capture software a higher end software like MaxIm for fancier image processing.

High End: Add to the basic software and MaxIm, a finishing software like Photoshop.

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One last note: I am constantly amazed at how some amateurs possess an ingenuity factor that far surpasses mine. They seem to get high quality images from equipment that doesn't seem to be able to produce the results they achieve. In the final analysis there is no substitute for understanding of the equipment you have and the ingenuity to make it work. Great equipment in the hands of those who don't understand it is useless. The old saying "It's a poor craftsman who blames his tools" does apply somewhat. So if you don't think your equipment is up to speed, don't let it stop you. Image with it anyway and learn all you can from it. Then upgrade as you can.

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I consider your heavens, the work of your fingers, the moon and the stars, which you have set in place ... Psalms 8:3