Imaging Equipment

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Starlight Xpress MX516 Monochrome CCD Camera

mx5.JPG (105134 bytes)The Starlight Xpress MX516 Monochrome CCD camera was the first CCD camera that I owned.  For its cost its performance was very good.  

The MX516 is extremely compact.  In fact it has been called the 'eyepiece camera' because it can be placed directly into a 2 inch eyepiece holder.   It uses the Sony ICX055AL chip which provides a reasonable 500x290 pixels (4.9x3.6mm) or a FOV of 8x6 arcminutes on a LX10.  It attaches to the PC's parallel port by means of a single cable.  There are no intervening electronics.  The camera comes with software that not only controls the operation of the MX516 but can perform most of the basic image processing tasks.  The camera has very low dark current.  I have taken images well in excess of 1 minute without the need to subtract a dark frame. The camera also has extremely good 'blue' response which makes it very suitable for color imaging. For me, the MX516 worked first time right out of the box.

SBIG ST-7E CCD Camera 

SBIGST7E.jpg (22301 bytes)The SBIG ST-7E CCD Camera is much more expensive than the Starlight Xpress MX516 but has more capabilities.  It uses the Kodak KAF-400E chip which has 764x510 9 micron square pixels (6.9x4.6mm).  This gives the ST-7E a larger FOV than the MX516.  However, the real differences between the ST-7E and the MX516 are self-guiding,  image binning and programmable cooling capabilities.  

First, let's discuss self-guiding.  The ST-7E has a second CCD chip mounted underneath the KAF-400E.  This second chip, a Texas Instruments TC-211 with 192x164 13.75x16 micron pixels (2.64x2.64 mm), can be used to autoguide the telescope while the KAF-400E is imaging.   You can buy add on hardware for the MX516, called STAR2000 which lets the MX516 selfguide but this works in a different way.  The MX516 uses the same chip to guide and image.  This allows you to guide on a star within the same FOV as your image but has the disadvantage that exposure durations are doubled because half the time of the CCD chip is spent guiding instead of collecting those all important photons for your image.  

Now lets look at image binning.  Binning is the ability of the camera to combine several pixels on the CCD chip to create one big pixel.  The ST-7E allows you to create an 18 micron square pixel from four 9 micron square pixels (known as 2x2 binning) or a 27 micron square pixel from nine 9 micron square pixels (known as 3x3 binning).  Clearly the resolution of the chip is reduced to 382x255 with 2x2 binning and to 255x170 with 3x3 binning.  Why would you want to trade resolution for pixel size?   The simple answer is exposure duration.  An 18 micron square pixel has four times the area of a 9 micron square pixel and consequently will collect 4 times as many photons in the same amount of time.  This means that exposure durations are cut by a factor of 4 with 2x2 binning and by 9 with 3x3 binning.  This feature can be particularly useful when producing color images using the LRGB technique.  With this technique, only the L or Luminance image needs to be taken at full resolution.  The R, G and B images can be taken at a much lower resolution without sacrificing the resolution of the final color image.  By taking the R, G and B images using 2x2 or 3x3 binning you can reduce the total exposure duration significantly compared to taking these images at full resolution.

Finally, lets look at programmable cooling.  The ST-7E has a cooler that can cool the CCD chip to 30 degrees C below the ambient temperature.  This is essential to reduce the dark current produced in the CCD chip which shows up as noise on your CCD image.  However, even cooling the chip to 30 degrees C below ambient will not stop dark current noise building up in your image during a long exposure.  Fortunately,  the dark current produced is always the same for a given chip temperature and exposure duration.  This means that we can take an image of the dark current,  known as a dark frame, and remove the noise from the original image simply by subtracting the dark frame.  The dark frame is created by taking an image with the camera shutter closed.  To ensure the same dark current is produced as in the original image the dark frame must be of the same length and be taken at the same temperature as the original image.   The ST-7E can be programmed to cool the CCD chip to a given temperature and then keep it there as long as the chosen temperature is not less than 30 degrees below ambient.  Why is this useful?  With the MX516, the dark frame must be taken soon after the image to ensure it has been taken at the same temperature.  With the ST-7E you can take the dark frames any time you want to as long as you program the camera to cool the CCD chip to the temperature at which the original image was taken.  This means you can take the dark frames the next day and not waste valuable imaging time imaging the back of your camera shutter!  You can even build up a  library of dark frames with different durations and temperatures.   I have noticed that the ST-7E produces a higher level of dark current than the MX516 for a given temperature.    However, this is not a significant disadvantage as the dark current is easily removed using dark frames and the design of the ST-7E makes it very easy to produce them. 

The overall quantum efficiency (sensitivity) of the ST-7E seems to be higher than the MX516.  This leads to shorter exposure durations.  However, the  sensitivity of the ST-7E to blue light is about half its sensitivity to red and green light.  For color imaging, this means images taken through the blue filter need to be twice as long as the the images taken through the red and green filters.  In contrast, the MX516 has a much more uniform sensitivity across red, green and blue wavelengths leading to roughly equal exposure durations through each filter.

One other difference between the MX516 and the ST7E is the shutter.  The MX516 has an electronic shutter whereas the ST-7E has a mechanical shutter.  The mechanical shutter of the ST-7E enables dark frames to be taken very easily as you simply close the shutter and take an image.  With the MX516 you have to cover the telescope OTA or close the mirror in the flip mirror.  However,  the mechanical shutter does mean that the shortest possible exposure is 0.1s compared with 0.01s for the MX516.

SBIG ST-2000XM CCD Camera 

SBIGST7E.jpg (22301 bytes)I purchased the SBIG ST-2000XM CCD Camera in November 2005. It has similar functionality to the ST-7E but has a larger, higher resolution chip.  The ST-2000XM uses the Kodak KAI-2020M CCD chip.  This is 11.8 x 8.9 mm and has 1600 x 1200 7.4 micron pixels.  It also features a TC-237H chip as the tracking CCD which has 2.7 times the area of the tracking CCD used in the ST-7E.  This increases the chance of finding a suitable guide star without having to adjust the position of the camera on the telescope.  The ST-2000XM also has a USB connection to the PC which makes image download a lot faster than the parallel cable connection on the ST-7E.  I chose the ST-2000XM over the ST-8XME because I wanted an ABG camera with a large, high resolution chip.  The ST-2000XM's ABG chip has a higher sensitivity than the ABG version of the ST-8E and is higher resolution with only a slightly smaller chip. It also costs $1000 less!

SBIG STL-11000M CCD Camera 

In 2008 I purchased the SBIG STL-11000M CCD Camera . It has similar functionality to the ST-2000XM but has a much larger chip.  The STL-11000 has a 35mm chip with 4008x2672 9 micron pixels.  The Kodak chip used is similar in sensitivity to the ST-2000XM but its 9 micron pixels mean that overall it is approximately 50% more sensitive.  This camera also has a built in filter wheel that will accept 5 50mm filters.  In all other respects the camera is very similar in features and operation on the ST-2000XM.

CFW8 Filter Wheel

SBIGST7E.jpg (22301 bytes)The SBIG CFW8 filter wheel can be attached directly in front of the ST-7E (as shown) or to the MX516 via a T-ring connector.  It is a motorised filter wheel that holds up to 5 1.25 inch filters and comes complete with a set of clear, red, green and blue filters for colour imaging.  The red, green and blue filters have an infra-red (IR) blocking coating which means you don't need an additional IR filter placed permanently in the optical path.  This has an added advantage when using the LRGB colour imaging technique.  With this technique, the L or Luminance image is a CCD image taken through a clear filter.  It should be the longest duration image as it is the one that will provide the detail in the final colour image.  Unike the R, G and B images it does not have to be taken with an IR filter in place.  An RGB filter set that relies on a separate IR blocking filter in the optical path will result in the L image being taken through a clear filter/IR filter combination.  This will lead to a longer exposure on the L image as the IR light is blocked.  The CFW8 filter does not require a separate IR filter and so the L image duration is lower.

The CFW8 comes with its own DOS based control software but I have used MaximDL to control it. When attached to the ST-7E, the wheel is controlled through the ST-7E parallel cable attached to the PC.  When it is attached to another camera it is controlled via the serial port of the PC.  With the CFW8 and MaximDL you can set up an RGB exposure sequence and leave it to run unattended.  Once each image is completed MaximDL instructs the filter wheel to move the next filter into position and then starts the next image.  Being able to set up an automatic sequence like this, with a very small delay between each filter change, is valuable for colour imaging of Jupiter where the fast rotation of the planet means you only have a few minutes to take all three RGB images to avoid blurring due to the planet's rotation.

Canon 10D SLR

The Canon 10D Digital SLR camera is quite capable of producing good quality images of the brighter deep sky objects and is very good for Solar, Lunar and Planetary imaging.  With it's big CMOS chip (23x15mm) and high resolution (3072x2048 7.4 micron pixels) it is an excellent camera for wide field imaging and for capturing the entire Lunar or Solar disk in one image even at relatively long focal lengths (1575mm).   The fact that it can take exposures as short as 1/4000th of a second allows Lunar and Solar images to be taken without the need to stop down the LX200 10" SCT.  With the TRC80-N3 timer you can take the long duration exposures required for deepsky imaging.  As the camera is not cooled, exposure duration is limited to around 5 minutes.  Much longer than that and the dark noise becomes unacceptably high.  However, by stacking multiple 5 minute exposures together very deep images can be taken.  An excellent review of the Canon 10D SLR can be found on Johannes Schedler's website

Canon 40D SLR

The Canon 40D Digital SLR camera is very similar to the Canon 10D.  The main differences are:

  •  It has smaller pixels (5.7 microns) in the same size chip giving a higher resolution of 3888x2592. 

  • Power efficiency is greatly improved over the 10D.  It's possible to take over 1 hour of 10 minute sub frames with the 40D with the internal battery pack. 

  • The LCD screen is much larger

  • It has a live view mode which can show you the real time image of a star on the LCD screen.  This makes getting a good focus much easier than with the 10D.

ToUcam Pro II Webcam

The ToUCam Pro II Webcam is ideally suited for high resolution planetary, lunar and solar imaging.  It has a sensitive 640x480 CCD detector with 5.6 micron pixels and can capture a large number of images very quickly in an AVI file.  This makes it very straightforward to collect a large number of short exposures of a planet.  A small percentage of these images (say 10%) will have captured the best moments of seeing and so show the most detail.  As a large number of images will have been taken in the AVI (say 2000), a fairly large number of good images will be left (say 200) which can be added together to produce an image with a very high signal to noise ratio compared to the original image.  If the 200 best images are added together, the resulting image will have a signal to noise ratio 14 times higher than a single image.   This image can then be processed with Unsharp Masking and Deconvolution software to yield high amounts of detail.  To attach the webcam to the telescope you will need to unscrew the lens that comes with the webcam and replace it with a T-ring adapter that lets you attach it to your telescope accessories. You will also need to use an infra-red filter with the webcam to get the correct colour balance when imaging.  I obtained my webcam, T-ring adapter and 1.25" infra-red filter from True Technology.  The 1.25" filter screws into the T-ring adapter.  

When taking images with the webcam it is important that you set the frame rate low enough (5-10 frames per second) so that the camera does not have to compress the image data as it is sent to the computer.  Compressing the image stream would mean you lose some of the fine detail you wanted to capture!

To control the webcam you can use the software that comes bundled with the camera. However I use Astrosnap to control the camera as it has a number of useful features such as focus aids and the ability to use the webcam to help collimate your telescope.

A good review of the ToUCam Pro II and suggestions for exposure and gain settings can be found here.

Takahashi FS-60C 60mm Apochromatic Refractor

The Takahashi FS-60C is an f/5.9 60mm Apochromatic Refractor.  It has a focal length of 355mm, which makes it a very good telescope for wide field imaging.  The focal length can be reduced to 270mm and the f-ratio decreased to f/4.5 by adding a Takahashi Sky 90 focal reducer.  This increases the field of view still further, produces a flat star field even on large format CCD chips and lowers the exposure times required.  Apochromatic refractors make excellent telescopes for colour imaging as they do not suffer from the chromatic aberration inherent in chromatic refractors.  Chromatic aberration is where the telescope brings different wavelengths of light to a focus at slightly different points resulting in colour fringing around objects. I obtained my Takahashi FS-60C from True Technology.  I have used it mounted piggyback on the LX200 and RCX400 using mounting rings and rails made by BC&F.


True Technology Flip Mirror Finder and Filter holder

flipmirror.JPG (90210 bytes)The True Technology Flip Mirror Finder and Filter Holder serves two purposes.  The first is to act as an aid in centering and focussing an object for a CCD camera.  It does this by putting a movable mirror in the light path from the telescope to the CCD camera.  When the mirror is down, the light passes through to the CCD camera as normal. When the mirror is inclined at 45 degrees, the light is diverted away from the CCD camera and into an eyepiece.  This allows the observer to see exactly what the CCD camera is looking at without removing the camera.  It is possible to adjust the position of the eyepiece so that it is parfocal with the CCD camera.  This means that an approximate focus for the camera can be found very quickly by first focussing the object in the eyepiece.   This has dramatically reduced the time it takes me to focus the camera.  Once the object is focussed in the eyepiece, taking a small series of images with slight focus adjustments in between each one will bring the camera to perfect focus.  A side benefit of the moveable mirror is the ability to take CCD dark frames very easily. Simply move the mirror to the 45 degree position and all light is cut off from the CCD enabling a dark frame exposure to be taken.

The second purpose served by this device is that of a filter holder suitable for color imaging.  The unit comes with four rectangular metal plates.  You can screw a standard 1.25 inch filter into each plate.  A plate/filter assembly can then be inserted into a slot in the filter unit which is just in front of the adjustable mirror.  You can remove and insert plate/filter assemblies without changing the position of the camera or focus of the telescope.  As well as the slot for filters, the unit also allows a 1.25 inch IR filter to be permanently mounted in front of the CCD camera.  True Technology sells a set of 1.25 inch RGB and IR filters suitable for color imaging with this unit.  The set comes with a clear glass filter which has the same thickness as the color filters so that you can focus the camera before inserting the color filters.

Meade 2 inch Flip Mirror

The Meade 2 inch Flip Mirror is similar in functionality to the True technology flip mirror above.  It does not have the filter holder but has a wider 2 inch aperture which it makes it suitable for attaching CCD cameras and DSLRs with larger imaging chips without causing vignetting.  It also allows you to adjust the flip mirror so that the image is dead centre in the eyepiece when it is centered on the CCD chip.  The flip mirror comes with a number of different adapters for attaching CCD cameras. This allows you to choose the adapter which puts the camera it at the right distance from the flip mirror so that the eyepiece can be made parfocal.  A cylindrical focusser is provided to help you focus the parfocal eyepiece.  All the CCD camera adapters have thumbscrews that allow you to loosen the adapter and rotate the camera should you need to do so to frame an image or find a guidestar.  This is much easier than the True Technology flip mirror where the adapter is attached via screws that need to be loosened and tightened with a screwdriver.


Celestron f/6.3 Focal Reducer

focalred.JPG (100064 bytes)Attaching the Celestron f/6.3 focal reducer to the f/10 LX10 or LX200 reduces its focal length by 37%.   This gives an increased field of view both for visual observations and CCD imaging (see What Focal Length Should You Use?). Also, the shorter focal length reduces the exposure times needed for CCD images by approximately 60%.

The exact reduction in the focal length depends on the distance of the CCD chip from the focal reducer.  The reduction is governed by the formula R=1-(D/F) where R is the focal reduction, D is the distance of the chip from the reducer and F is the focal length of the reducer.  In other words, the further away the CCD chip is from the focal reducer the larger the focal reduction will be.  In reality, the focal reducer is only designed to work well when the chip is close to the distance that yields f/6.3.  At distances greater than the point which yields f/6.3 the image is likely to suffer from vignetting.  Vignetting is seen as darkening around the edges of CCD image.  It is caused when the field of illumination of the telescope has been reduced to the point where it is smaller than the CCD chip. 

Looking at the separation of stars in my images I have calculated the focal length of the reducer to be 298mm.  This means f/6.3 is achieved when the chip is 110mm from the reducer.  I have taken images with the MX516, True Technology Flip Mirror and Celestron OAG connected to the reducer.  This setup places the CCD chip approximately 150mm behind the reducer which results in a focal reduction of R=0.5 or f/5.  The SBIG ST-7E, CFW8 and True Technology Flip Mirror combination also places the CCD chip approximately 150mm behind the reducer.   I got away without any vignetting on  the MX516 setup even though the chip was 40mm away from the f/6.3 distance.  However, the SBIG ST-7E has a bigger CCD chip and that shows distinct signs of vignetting 150mm from the reducer. You can see the effect on my Horsehead Nebula image.   To remove the vignetting I will move the SBIG ST-7E clsoer to the focal reducer by changing the adapter combination used with the flip mirror.  The effect of vignetting can also be significantly reduced by the use of flat fields.

Meade f/3.3 Focal Reducer

Attaching the Meade f/3.3 focal reducer to the f/10 LX10 or LX200 reduces its focal length by 67% and exposure durations by 90%.  This gives an increased field of view for CCD imaging (see What Focal Length Should You Use?).  The field illuminated by the f/3.3 image is so small that it can only be used for CCD imaging.  Using it for photographic or visual observation will result in severe vignetting.

The f/3.3 reducer comes with a variable T-adapter for attaching the CCD camera to the reducer.  The variable T-adapter comes in three sections.  The first attaches to the focal reducer and provides a T-thread connection 7mm from the reducer lens.  There is then a 15mm extension tube and a 30mm extension tube that can be screwed on.  This allows the CCD camera to be attached either 7mm, 22mm, 37mm, or 52mm from the reducer lens.

The reducer only yields f/3.3 images when the image is a focused at a specific distance from the reducer (see Celestron f/6.3 Focal Reducer).  Looking at the separation of stars in my images I have calculated the focal length of the reducer to be 85mm.  This means f/3.3 is achieved when the chip is 57mm from the reducer.  I have taken images with the CFW8 directly coupled to the SBIG ST-7E and attached to the reducer via the 7mm adapter.  This setup places the CCD chip 49mm behind the reducer which results in a focal reduction of R=0.42 or f/4.2.  The image of M42 that I obtained at f/4.2 shows no sign of vignetting.  As the CCD chip should not be placed more than 57mm from the focal reducer it is not possible to use a flip mirror between the reducer and the CCD camera.  Fortunately, the reducer provides the CCD chip with a large FOV so it is relatively easy to find images with the LX200 GOTO in high precision mode.

There is an excellent review of the Meade f/3.3 focal reducer, together with the Optec f/3.3 reducer on Chris Vedeler's site.  

Meade 2x Apochromatic Telenegative

The Meade 2x Telenegative is inserted into the eyepiece holder of the LX10 or LX200.  Eyepieces or CCD cameras can then be inserted into the telenegative.  The telenegative increases the focal length of the telescope which is extremely useful for imaging planets where a long focal length is required to increase the size of the planet on the CCD chip and spread the light out so that minimum duration exposures are not saturated.  The increase in focal length depends on the distance of the CCD chip from the telenegtive lens.  The increase is governed by the formula M = 1 + (D/F) where M magnifcation factor of the focal length, D is the distance of the CCD chip from the telenegative lens and F is the focal length of the telenegative. This implies the further the CCD chip is from the telenegative the greater the increase in focal length.  In reality the telenegative is designed to work best when the CCD chip is close to the distance that yields a magnification factor of 2.  However, how close the chip is to this distance does not seem to be so critical as for a focal redcuer.  

When I attach an MX516 and True Technology Flip Mirror to the telenegative I get a magnifcation factor of 3 giving an f-ratio of f/30.  When I attach the SBIG ST-7E, CFW8 and True Technology flip mirror I get a magnification of 4 because the CCD chip is further away from the telenegative lens.  This yields an f-ratio of f/40.  The f/40 setup seems to yield very acceptable images.  Take a look at my f/40 image of Jupiter.

Robofocus Focuser

The Robofocus is the electric focuser I use on my Takahashi TOA-130.  It is capable of very accurate focusing (to within less than 0.001 of an inch).  It can be manually operated from the supplied hand controller but it can also be attached directly to a PC via a serial port which enables software controlled automated focusing.  I use the freeware FocusMax software on my PC to perform automated focusing with Robfocus.  This has worked extremely well for me providing reliable and accurate focusing in my automated imaging sessions. 

TAKometer Rotator

The TAKometer Rotator from Astrodon fits Takahashi refractors with a 4 inch focus tube and enables automatic rotation of the CCD camera from your PC during an imaging session.  This accessory makes it really straightforward to rotate the CCD camera to the required angle to find a guide star.  It is an essential piece of equipment for automated imaging sessions where you may be imaging several different targets at different position angles and also have a meridian flip where the camera needs to be rotated 180 degrees after the flip to maintain the same position angle and reacquire the original guide star. 

Flip Flat for taking artificial flats

The Flip Flat from Alnitak Astrosystems is a circular paddle that contains an evenly illuminated light panel which covers the OTA opening of a refractor in place of the dust cover.  It is motorized and so can be opened for imaging and closed for flat fielding under the control of automated imaging software.  This makes taking flat field images as part of an automated imaging session very easy.

JMI Motofocus Electric Focuser

motofoc.jpg (105132 bytes)An electric focuser allows you to adjust the focus of your telescope without touching the manual focusing knob.  This means you can look at an object through the eyepiece and focus the telescope without the vibration caused when you turn the manual knob.   This makes it much easier to achieve the correct focus.  An electric focuser also allows very fine focussing adjustments which it makes it particularly useful for CCD imaging where the telescope has to be focussed very accurately.

The standard JMI Motofocus is very easy to install.  It is basically an electric motor that sits on top of the manual knob and turns it when you operate the Motofocus handcontroller.   The handcontroller is attached to the electric motor by means of short cable.   This allows you to change focus without touching the telescope and causing vibration.  The handcontroller has two buttons which allow you to turn the manual knob clockwise or anticlockwise.  It also has a speed control which allows you to alter the speed with which which the manual knob is turned.  By selecting a slow speed you can achieve the fine focussing of the telescope that is required for CCD imaging.

In 1998 I purchased a JMI Digital Motofocus.  It works on exactly the same principle as the standard Motofocus described above but adds a digital counter that goes from 0-999.  The counter lets you know exactly how far you have turned the manual focus knob each time you use the handcontroller. From 000 to 999 on the counter represents 10 turns of the manual focus knob.  The distance between each digit on the least significant counter wheel is marked off in fifths giving a total of 5000 different counter readouts for 10 turns.  This means you know the position of the focus knob to an accuracy greater than 1/100th of one complete turn.    If you record the readout at various focus positions (e.g. for each eyepiece, CCD camera etc...) you can get back to that focus position quickly and accurately on subsequent nights.  This proves really useful for the CCD camera which can take some time to focus accurately using other methods.  With the Digital Motofocus you just need to accurately focus the CCD camera once using normal methods, record the readout on the counter and from then on focussing the camera is as simple as pressing a button on the handcontroller until the counter shows the correct focus position.  A great timesaver.

There are  two main drawbacks that I have noticed with both the standard and digital models of the JMI Motofocus:

  1. When finding an accurate focus for a CCD camera you have to take a picture, look at the image displayed on the PC, alter the focus slightly, take another picture, and so on until you get an image that is correctly focussed.  Unfortunately, the PC is often several feet away from the telescope and the handcontroller cable is only a few inches long.   This means walking back and forward between the PC and telescope while focussing.   This makes focussing much more difficult and time consuming than it needs to be.   I have solved this by extending the cable to the handcontroller so that I can sit by the PC and operate the handcontroller at the same time.  Focussing is now easy!   The Motofocus cable plugs in to the handcontroller using a small headphone jack.   Extending this cable is simply a matter of attaching a headphone extension lead which supports the small jack plug.  These cables are readily available in most electrical stores.  This problem is also solved by the Digital Motofocus as it greatly reduces the time necessary to focus the CCD camera (see above).

  2. Once the Motofocus is attached you can no longer turn the manual knob yourself.   This may not sound like a problem, but with CCD imaging you have to make a big focus shift when you first attach the camera.  This involves several turns of the manual knob.  Even at its highest speed it can take the Motofocus a long time to accomplish this.  Fortunately, removing the motofocus is similar to removing an eyepiece.  You simply undo its retaining screw (which can be done by hand) and pull it off.  This allows you to operate the manual knob as normal.  This workaround cannot easily be used  with the Digital Motofocus.  If you have recorded the counter readout at various focus positions and then remove the Motofocus to turn the manual knob, you will have to work out new counter values for the focus positions when you replace the Motofocus.  This is because the Motofocus has no idea how far you turned the knob yourself.  You should never remove the Digital Motofocus unless you absolutely have to.  The time taken to perform a large focus shift using the Motofocus is much less than having to work out those focal positions again!

The JMI Digital Motofocus can also be attached to the LX200.  In fact you can plug it directly into the focuser port on the LX200 control panel.  This allows it to be controlled via the LX200 handcontroller instead of using the separate JMI handcontroller.

JMI NGFS Crayford Focusser

The JMI NGFS Crayford Focusser attaches to the SCT threads on the visual back of the LX200.  It can very precisely move an eyepiece/camera a small number of centimetres towards or away from the telescope,  This means that you can achieve a rough focus using the manual focus knob and then use the NGFS to achieve a critical focus.  The advantage of using the NGFS to reach critical focus is that it can be more precisely controlled than the focus knob.  This lets you make smaller changes to the focus than would otherwise be possible.  Also, as the mirror is not moved to achieve critical focus, the image will not shift in the eyepiece or CCD chip while making the final adjustments.  This makes it much easier to detect when critical focus has been achieved.