The 64bit Vista driver (also works with Windows 7 64bit) for the MX716/7C can be downloaded here along with installation instructions

The driver supports both the original StarlightXpress software, AstroArt and MaximDL. In addition, the MaximDL universal firmware may be used (see installation instructions for details).

I’ve also created 64bit drivers for the newer Lodestar guiding camera and SXV USB2 range of CCDs, these are now available for download direct from the Starlight Xpress site and are for Windows7 64bit.

My thanks to Terry from StarlightXpress for his assistance and openness on the SX hardware.

Why is this a problem? Take a look at the image below of M51. I’ve stretched the data a little to emphasise the brightening. The problem is that in order to bring out fainter details in the galaxy or the lower magnitude stars around the edges of the image, the data levels need adjusting. However, long before those stars are visible, the bright centre has spread across the entire image and ruined it.

Vignetting

After doing some research, it turns out this is known as vignetting and is a problem caused by the telescope optics. MAPUG-Astronomy describes this in great detail, but the important part is

The image is brightest on axis, at the center of the field of view, and dimmer off axis. This is a classical case of vignetting. Note that this is not a sharp cut off of the image, but a gradual dimming of it. Unfortunately, it is a feature of folded telescope optics which cannot be avoided.

Flat Frames

Although nothing can be done to prevent vignetting, it turns out there’s a way to account for the dimming and in turn remove it from the images. Enter the Light Box. By taking a photo of an evenly lit area, the dimming of pixels from vignetting can be isolated and then in turn removed from the light frame.

I’ve built a light box using foamboard to construct the box and holders for the diffusers. Two sheets of opal perspex slot into the holders to diffuse the light (from four LEDs) and present a flatly lit front pane. The box is loosly based on the many designs posted throughout the net. It won’t win any awards for construction, but it was cheap About £25 in materials which can likely be sourced for cheaper than that.

Here’s an avi showing the light box image captured by the CCD in various rotated positions to ensure the field is evenly lit and that the dimming is due to vignetting and not shoddy light box construction

Flat Field AVI

Calibration

After calibrating the images with the flat field frames, here’s the result.

The bright gradient has now been eliminated. All that remains is a bit of signal noise which can be handled by stacking multiple short exposures. Below is the first stacked and calibrated image. I’m still working on alternative ways to process the fits data to improve the image, but a quick processing shows promising results.

After a closer inspection of the combined frames, there is still a slight gradient from the bottom of the image moving upwards towards the centre. Whether this is due to the light box not providing a totally flat field frame or simply light pollution, I’m not yet certain.

A Trio of Galaxies

• Exposure Time: 30×120s Avg
• Date: 2009-03-05 03:06 UTC
• CCD: Starlight XPress MX716
• Scope: LX90 8″
• Dark Frames: 10×120s Avg
• Flat Frames: 10×0.8s Avg
• Apparent Dimension: 11 x 7 arc min
• Visual Brightness: 8.4 mag

The centre of the image shows two galaxies, the first and larger NGC 5194 and just above it NGC 5195. The two colliding galaxies are better known as M51 the Whirlpool Galaxy.

During processing I noticed a faint object in the lower right corner. According to the reference of bright galaxies, this is IC 4263, a magnitude 15 galaxy measuring only 2×0.4 arc minutes in size.

The image to the right has had a high pass filter applied as an attempt to sharpen the image a little. I’m still not sure which of the two I prefer most.

I’ve glossed over all the details of calibrating images, but if you’re interested in knowing more there’s a few sites with more detailed descriptions. Such as AAVSO

There’s still a lot of room for improvement. Still, compared to my previous attempts at M51, I think the light box was worth every penny

A nearly full moon, combined with a slightly hazy sky limited the choice of objects severely. The moon was out of the question, as I’ve yet to buy a moon filter, even on the lowest exposure setting of 0.001 seconds the ccd chip was becoming fully saturated. So I turned instead to the Orion Nebula, M42.

At magnitude 4.0 the nebula is visible as a fuzzy gray blob to the naked eye, just below the belt of Orion. I took a total of 90 exposures (81 usable) at 15 seconds each in an attempt to not burn out the central core on the 15 second exposures, whilst bringing out the fainter detail.

• Exposure Time: 15×81s Avg
• Date: 2007-11-23 23:47:55 UTC
• CCD: Starlight XPress MX716
• Scope: LX90 8″
• Dark Frames: 15×15s Median
• Apparent Dimension: 85×60 arc min
• Visual Brightness: 4.0 mag

Since it looked neat, I’ve uploaded a pseudo colour version, this isn’t in anyway the true colour of the Orion Nebula, I don’t have any colour filters yet

I believe this is my best image to date. Although it’s still not quite in focus, the exposure was perhaps too long resulting in a burnt out core. Not to mention the moon/haze made post processing a nightmare with a bright central light gradient to remove.

Collimation of the scope is still slightly out. I spent an hour before taking this image to improve it a little, but it’s going to take stabler skies before I can collimate at a reasonable magnification. I think the sky stability and lack of good collimation is partly to blame for the difficulty in achieving a good focus.

I’m looking forward to re-imaging this object on a moonless night to see how big an improvement I can achieve.

The seeing over the last few nights, has still been poor, with stars twinkling away making achieving critical focus very difficult. The collimation adjustments from March do seem to have improved things, although I still think finer adjustments will be needed on a night with better seeing.

On the first nights outing, Polar alignment was woeful and gotos were constantly 1/4 fov in the finder off. Still, I managed to image a few objects, the two most notable been a double star cluster in Persei and M33 a spiral Galaxy in Triangulum.

h Persei Open Cluster

• Exposure Time: 6×60s Avg
• Date: 2007-09-08 02:44:37 UTC
• CCD: Starlight XPress MX716
• Scope: LX90 8″
• Dark Frames: 7×60s Avg
• Apparent Dimension: 30 arc min
• Visual Brightness: 4.3 mag

The image above is h Persei (NGC 869), which along with Chi Persei (NGC 884) forms a double cluster. The full double cluster was a little too large to fit into the tiny fov of my CCD camera, I’ve not calculated the exact fov yet, but it’s somewhere around 30 to 60 arc minutes.

Open clusters are interesting objects as they contain hundreds, sometimes thousands of stars, all of which were born around the same time and are still gravitationally bound (however loosely) to each other. This is in contrast to Globular Clusters (such as M15 which I imaged on Monday and will upload later) which are strongly bound and often contain millions of stars in a tightly packed ball, making them stunning visual objects.

M33 Spiral Galaxy in Triangulm

• Exposure Time: 15×60s Avg
• Date: 2007-09-08 02:12:17 UTC
• CCD: Starlight XPress MX716
• Scope: LX90 8″
• Dark Frames: 7×60s Avg
• Apparent Dimension: 70×45 arc min
• Visual Brightness: 5.7 mag

I’m quite pleased with the M33 image, the stars are reasonably well focused and the spiral arms are fairly visible. It’s far from a perfect image, with a good proportion of the outer arms not visible, but considering the skies were a little hazy and how blurry my previous images have turned out, I think this is a huge improvement.

Also just about visible on the edges of M33 is NGC 604 a diffuse nebula.

I also imaged M31 the great Andromeda Galaxy, however after underestimating the sheer size of it, the image ended up containing only the bright core and a few dust lanes.

At the start of this week I also managed a third night imaging several objects, M15, M101, NGC7780, NGC 281 (Pacman Nebula as well as a poor image of M42 taking during early dawn. I should have these processed and the best uploaded to this post later this week.

M15 Globular Cluster in Pegasus

• Exposure Time: 15×60s Avg
• Date: 2007-09-10 23:48:16 UTC
• CCD: Starlight XPress MX716
• Scope: LX90 8″
• Dark Frames: 15×60s Avg
• Apparent Dimension: 18 arc min
• Visual Brightness: 6.2 mag

Despite using the fastest exposure time my ccd camera was capable of 0.001s, the moon was still over exposed. Really a filter will be needed to reduce the light gathered by the scope for future attempts. Still with a bit of post processing I’ve managed to isolate the overexposure to a smaller area.

• Exposure Time: 1 x 0.001s
• Date: 2007-03-27 00:42:07 UTC
• CCD: Starlight XPress MX716
• Scope: LX90 8″
• Dark Frames: 2×0.001s averaged

The second image was taken through the first wave of fog and suffered for it, especially with it been a 1/2 moon and limited to 5 second exposure times If I’d noticed the fog coming in, I’d have packed up before the corrector plate became saturated, the dew heater didn’t stand a chance

Still, you can just about make out the spiral arms of M51 and the companion galaxy above as well as the effects of the moon and fog despite post processing attempts to clean it up I plan to reimage this pair of galaxies on a fogless night with more suitable exposure times to really bring out the detail.

• Exposure Time: 20 x 5s aligned and stacked
• Date: 2007-03-27 01:26:36 UTC
• CCD: Starlight XPress MX716
• Scope: LX90 8″
• Dark Frames: 1×5s

Tuesday was again a clear night, but yet again fog rolled in early. Knowing the nights imaging would be short, I decided against setting up for photography and instead spend the time collimating the scope to get the mirrors aligned correctly, which after allowing 90 minutes cooldown didn’t leave all that long.

Seeing was only good enough to collimate with a 12mm eyepiece, still I felt it improved views of Saturn and the moon considerably unless it was a placebo effect, guess I’ll find out next time I the ccd camera is setup. I’m sure given a night with better seeing allowing a 6mm eyepiece to be used, I could improve on the collimating further, which I’m hoping will improve the problems I’ve been having achieving a good focus whilst imaging.

With a good clear night on Monday, I took the opportunity to take a photograph of the comet. Yes I know, its not quite up to hubble standards

Considering how little experience I have imaging, I’m quite happy with how this image turned out. I’m sure someone with more experience (read – any experience) at image reduction could improve on this.

In hindsight, I should have taken a lot more exposures for stacking and perhaps used a longer exposures time to help cut down on light pollution.

For anyone that cares, here are the image details:

• Exposure Time: 5 x 1.0s stacked
• Date: 2006-05-10 02:19:44 UTC
• CCD: Starlight XPress MX716
• Scope: LX90 8″
• Dark Frames: 5 x 1s median combined

I also managed to get an image of M57. 10×10s exposures stacked with 4 median combined dark frames. Comparing the image to my star charts, I’ve accounted for most of the brighter and dimmer stars but there’s one star that shows quite brightly that isn’t listed on my star chart, if anyone knows what it is please let me know.

The biggest problem I’m currently facing is the lack of accurate focus. I’m probably going to invest in a zero image shift microfocuser to help improve on that. I also think my scopes collimation is off, something to double check next time I get a clear sky. Fingers crossed I don’t spend all night on it only to make it worse

Hopefully with more practice I’ll get a little closer to getting the most out of the scope. In the hands of an experienced user, the LX90 and MX716 are capable of much much better images.