Page Turner Mk II

Using an LCD monitor + computer for sheet music display along with the first version of Page Turner has turned out to be a much nicer experience than struggling to page turn manually. However, the iPad lacks a serial port yet it makes for a great portable sheet music display.

Enter Page Turner Mk II, a USB device that plugs into the iPad's camera connection kit and identifies itself as a USB keyboard device. It sends a page forward/backward keypress depending on which foot pedal is pressed.

The USB port shown in the photos is used to connect a standard USB cable to the iPad via the camera connection kit, as far as the iPad is concerned this is a normal USB keyboard. The two jack sockets on the opposite side of the box accept 3/4" foot pedal jacks to allowing both forward and reverse page turns.

Holding the "forward" pedal down and plugging the device into a a PC will cause the bootloader to enter flashing mode, allowing new firmware to be downloaded to the device.

Internally the device makes use of a PIC 18F4550 which includes a USB module and corresponding stack which avoids interfacing with a separate FTDI chip. A lower pin count PIC could have been used, but I had the 18F4550 spare at the time. Hardware wise, the device is pretty simple with just a few decoupling capacitors, a crystal to drive the PIC and interface connections for the two switches plus USB socket.

Since making this, the AirTurn bluetooth model is now on sale in the EU, I had planned to buy one when they became available, however I'm now tempted to make Page Turner Mk III with bluetooth instead :)

MX716/7C and SXV 64 Bit CCD Drivers

Last year I switched over to a 64bit operating system and realised there were no 64bit drivers available for the MX716 CCD camera I use for astrophotography. Unable to pass up the opportunity to learn about windows driver programming I spent a bit of spare time creating two drivers for the camera (firmware loader and blockIO driver).

The Windows 7 64bit MX716/7C driver (v1.0.3.1) can be downloaded here, installation instructions are included.

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 Windows 7 64bit.

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

Page Turner

Its about a year and a half since I bought a Digital Piano and finally started practicing daily. In that time I've progressed quite well and the pieces I'm able to play (albeit still at the late-elementary / early intermediate level) are finally starting to increase in length to a few pages.

This has brought about a problem I'd not really considered up to this point that I'm sure plagues all pianists. How to turn the page without interrupting your playing. Given time I'm sure I could get used to reaching up and turning the page and make do with copying a few measures from the next page to get me to a suitable place to turn the page, but I'd rather not :)

A product called the AirTurn provides a solution to this problem. However, as a hardware hobbiest I decided to roll my own. Using a Laptop or LCD monitor to display the scores in either Adobe Reader or Music Reader and a serial connected foot pedal to fire off a PG Down event.

Above is a picture of the final device and a screen shots of the pedal turner .NET application which monitors the serial port and sends out PAGE DOWN keyboard events to the activate application whenever the pedal is pushed down.

The application and documentation, which also includes brief instructions on how to build your own serial connector (it's pretty simple!) can be downloaded here

As a side benefit to going digital, there's no more printing out digital music from the various on-line stores and no more hunting around for a specific score amongst the thousands of downloadable public domain scores.

With PDF Annotator or MusicReader, it's also possible to annotate the scores, adding fingering information and highlighting practice sections. Plus re-ordering pages so they're out of sequence is great for handling all those jumps back and forth in a piece. [Shortly after writing this blog I purchased MusicReader and have not regreted it.]

I've demo'd several other apps, but mostly they're related to music notation rather than playing from a score. Theres some pretty cool OCR software available for music that'll scan a score, convert it to various formats including MusicXML and allow you to play it back. Unfortunately, all the apps that include that kind of feature do not seem to offer any kind of library management nor are they as suited to playing from and annotating scores as MusicReader is.

From what little I've used of MusicReader so far, one feature I'd like to see added is a layer option. Having the ability to erase all annotations on a given layer whilst keeping marks made on other layers rather than having to be careful what you erase. Plus an option to toggle the visible layers.

I guess I can't discuss paperless playing without mentioning Hugh Sung, who's blog and youtube videos put me onto MusicReader and the pedal page turning idea in the first place. His company produce the AirTurn, which is a USB device that allows you to connect a set of pedals to your PC without wires. His site is also responsible for the expensive notion of buying a table PC that I now have stuck in my head, hopefully the idea will remain there and not make it to my credit card ;)

RA Clutch Slippage

Back in 2002 when I purchased my first telescope, an 8" LX90, the first month or so of usage brought up a very frustrating problem. When slewing the scope to a new target it would suddenly stop mid-slew, yet the motors continued to whir. The cause, the RA clutch had loosened and was no longer engaged, gotos were now ruined and after tightening the RA knob to engage the clutch I had to start the alignment process over again. Very frustrating.

I solved the problem after receiving some useful suggestions from the LX90 yahoo group, not a single clutch slip in nearly 7 years usage :) Earlier today I received an email asking about how I fixed the issue so I thought I may as well type it up.

The cause of the clutch slippage is pretty simple, as is the fix. The knob that you tighten on the base of the LX90 to engage the clutch is pushing against not only the clutch but the top of the LX90 base too. As the scope slews, the friction between the base and knob is sufficient to slowly unscrew and disengage the clutch. So the fix is simply to raise the knob off of the base of the LX90.

To do so, use an Allen key to loosen the small screw on the side of the RA clutch knob. Then turn the knob anti-clockwise until it catches and starts to unscrew. It should eventually come fully off as the photo below shows.

Notice the circular scratch marks from the RA knob contacting the base.

Inserting a nylon or fibre washer (not metal) over the bolt that protrudes from the base, one that is small enough to fit inside the hole, will raise the RA knob just enough to prevent contact occuring with the telescope base when the clutch is engaged.

If you look at the base of the bolt, you should be able to make out the washer I've added. Here's a close up

Re-assembly is straight forward, just be sure the clutch is fully engaged before you tighten the tiny screw on the RA knob.

With this simple fix, you only need to apply a little pressure when tightening the RA knob and engaging the clutch. Also, no matter how much you slew the scope, the knob should no longer contact the base and cause the clutch to slip.

More recently, I've taken apart the DEC axis to fix a significant (when viewed through eyepiece) amount of slop of 5-10 degrees. When I get a spare moment, I'll upload photos of the disassembly. They show the amount of excess grease inside the dec axis and the cause of the slop, an over tightened screw on the worm gear!

CCD Image Processing

Its been a while since I've made an astronomy post, not because I haven't had the scope out imaging, but because I haven't been all that happy with recent results. My images have been showing a nasty central brightening that prevents fainter details been brought out in post processing.

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 YouTube

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: 30x120s Avg
• Date: 2009-03-05 03:06 UTC
• CCD: Starlight XPress MX716
• Scope: LX90 8"
• Dark Frames: 10x120s Avg
• Flat Frames: 10x0.8s 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 2x0.4 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 :)

Orion Nebula

Winter is usually a great time for astronomy with longer nights and the sun setting at a reasonable hour, with the forecast for last Friday as clear until 12am I thought I'd put in a few more hours imaging. I hadn't realised it was a waxing gibbous moon until after I'd lugging all the gear outside and started setting up.

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: 15x81s Avg
• Date: 2007-11-23 23:47:55 UTC
• CCD: Starlight XPress MX716
• Scope: LX90 8"
• Dark Frames: 15x15s Median
• Apparent Dimension: 85x60 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.

"My God, it's full of stars!"

The usual clouds that seem to be permanently situated above the UK parted for a few days, which finally coincided with a few evenings I had spare. The LX90 hasn't seen the night sky since way back in March, when I last had it pointing skyward for my first real attempts at collimation.

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: 6x60s Avg
• Date: 2007-09-08 02:44:37 UTC
• CCD: Starlight XPress MX716
• Scope: LX90 8"
• Dark Frames: 7x60s 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: 15x60s Avg
• Date: 2007-09-08 02:12:17 UTC
• CCD: Starlight XPress MX716
• Scope: LX90 8"
• Dark Frames: 7x60s Avg
• Apparent Dimension: 70x45 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: 15x60s Avg
• Date: 2007-09-10 23:48:16 UTC
• CCD: Starlight XPress MX716
• Scope: LX90 8"
• Dark Frames: 15x60s Avg
• Apparent Dimension: 18 arc min
• Visual Brightness: 6.2 mag