Gamma Cygni

Sharpness Control for Philips Webcams and Derivatives

Introduction

One of the advantages of Linux for astro-webcammers is that the fullest range of camera control are accessible to the user, through the PWC camera driver. Crucially this includes control of image sharpness. The benefits are obvious, especially for deepsky imaging. Until now webcammers who use MS Windows have had to put up with image artifacts around bright objects. These are widely referred to as ears, due to their characteristic patterning on either side of the bright object. The only way to get rid of them has been to either process them out using a neat little Windows application, Loreal, or to move to Linux. Qastrocam allows you to set the sharpness control to zero, which removes all traces of the dreaded ears. The images are soft, but that can be sorted out once the images have been calibrated, aligned and stacked. By the way reducing the sharpness also removes the nasty artifacts around hot pixels, which makes dark subtraction far more effective.

Linux does have an excellent image capture program called Qastrocam, but there are not many image processing applications or scope control programs available for amateurs. This is being addressed by the Lin4Astro team, but most folks want to work with their favourite tools in Windows.

Discovery

Because of my particular interest in deepsky imaging I had converted to Linux for capturing raw images. I still did all image selection, calibration and post processing in WIndows. In November 2003, I was checking the periodic error on my mount. For this I reverted to K3CCDTools and RXPEC as I wanted the added functionality provided by these Windows applications. I wasn't interested in the image quality until I realised that the star I was using to test the tracking looked remarkably earless, just like Qastrocam's stars. Somehow the zero sharpening had been saved to the camera.

The Solution

I knew that the save setting functionality in Qastrocam was not functional, so I tried all sorts of things to try and replicate the zero sharpening, to no avail. While surfing through the PWC driver website for inspiration I found a link to a little program, SETPWC which looked promising. It is basically command line program that lets you interrogate the internal control registers and NVRAM of Philips Vesta and ToUcam webcams.

After downloading the program and compiling it I found it allowed me to set, verify and save the settings for the camera. What is more when I connected the camera to my Windows PC and ran K3CCDTools I got the reassuringly blurry images of a camera with its sharpness set to zero - Result!!!

The next test was to see what would happen if I saved these settings as User Settings from within K3CCDTools. Fortunately, the image remained blurry, even when I changed some of the other settings such as white balance and B/W. This is important as it would not be much good if you needed to set the camera up in Linux each time you wanted to change a setting.

So what happens when you reset the camera to its Factory Settings? Well, not surprisingly the image sharpness is reset to its standard setting. What is interesting is that if you load the user settings, sharpening is switch off again. This is good news as it means that potentially you only need to configure the camera once under Linux to have both normal and zero sharpness. However you need to be careful, because if you revert to Factory Settings and then save them as User Setting you will need to use Linux to get access to zero sharpening again.

SInce this First Light I have developed a more robust mechanical and electrical design, which will be star tested at the earliest opportunity.

Step by Step

Install SETPWC on a Linux machine. PWC should already been installed in recent versions of Linux.

Connect the camera to Linux PC.

Navigate to the executable and type:

setpwc -h

This gives you all the command line options.

With the camera connected you can configure it to your liking.

Type:

setpwc -p

This should return the current setting of the camera. If you get no response from the camera, type modprobe pwc at the command line and try again. This should find it up if Linux has lost it.

To switch off sharpening type:

setpwc -m 0

You can set other levels, 0 - 65,000 to suit your needs.

Now check that the setting has changed by retyping:

setpwc -p

You may also want to set the Noise reduction to OFF by typing:

setpwc -q 0

When you are happy with the settings type:

setpwc -b

This will write the settings to the NVRAM in the camera.

Now you can disconnect the camera and reconnect it to Windows. Go to your favourite capture application and verify that the settings have taken effect - deep joy!

Benefits

Windows Users can capture their images in the applications that they have become familiar with. The mod works with K3CCDTools and Astrosnap so it should work with anything that uses the Windows WDM driver.

Users can run Windows scripting, mapping and scope control applications on the same PC.

The image production process can be carried out in a single operating system.

Personally, I think that the windows driver produces better output at Video frame rates. This might be subjective. I'd like to hear others opinions on this point.

The Noise Reduction control can be set to zero also, which increases the apparent gain of the camera.

No need to get the soldering iron out.

Oh Yeah - No Ears!

Conclusion

I hope you find this modification useful. I hope that this inspires more people to consider webcams as a entry into the amazing hobby of astro-imaging.

I'd like to thank the following people:
Franck Sicard for writing Qastrocam, I would not have discovered this modification without his software and Linux.
Folkert Van Heusden for writing SETPWC, which allows the Philips cameras to be configured
Nemosoft for developing the PWC Linux driver.
Steve Chambers for ideas bouncing.
Gene Chimahusky for testing the mod, and proving that I was not dreaming.

If you find this of use, let me know; and Perhaps you would like to make a donation to Cancer Research UK
That would make me feel good.

The instructions are provides 'as is' with no guarantees of being correct, accurate or even working. You agree to be responsible for any injury, damage or loss that results.

Further Developments

Martin Burri developed a port of SETPWC named SETWC that allows the features of SETPWC to be accessed through Windows. This proved quite successful though some user had difficulties getting the USB interface to recognize the camera correctly.

Jack Reed had also been looking into ways of accessing the 'secret' functions of the Philips-based webcams. He had developed a link with the camera using the I2C interface. that is used to pre-program the webcam during manufacture. Jack's software and interface design can be used to interrogate and modify the contents of the camera's EEPROM, which holds all the SETPWC setting and a lot more besides. Jack's website can be found here

A Yahoo Group called TWIRG, which stands for Tweak Webcam I2C Research Group has been established as a forum for those interested unraveling the secrets of the Philips-based webcams. Already, great strides have been made.

Martin Burri has developed a program for accessing the EEPROM settings via the USB. It is hoped that this software can be developed for general use, once a solution has been found for resurrecting cameras that have been 'scrambled' by over-ambitious probing. At present it is only possible to bring these cameras back to life using Jack's I2C interface - BE WARNED!!!

Members of the TWIRG Group have developed revised EEPROM code that can access the raw pixel data from the output of the analogue to digital converter. This means that the full resolution of black and white sensors can recorded, just like conventional imagers. The so called 'RAW mod' has been adapted to colour sensors, so that alternative bayer interpolations can be used as part of the post processing, with improved luminance resolution.

ICX414AL Amp-Off Modification

Introduction

Soon after building the SC4 camera, I decided to work on an Amp-Off design for it. In the end I settled for a Burri- Behrens modification. I have used this with some success, but have never managed to rid the camera of a annoying levels of read-out noise and the dreaded diagonal banding. What was particularly annoying was the way the noise varied - sometimes it was acceptable, whist at other times it would ruin an whole imaging session. I tried to adjust the layout of the CCD PCB and cable routeing, but to no avail. With the amp-off circuit 'in circuit' there was noise.

I discovered the following modification during investigation of Vesta Pro EEPROM tweaks. The Vesta Pro and ToUCam EEPROMs are used to store settings for the cameras on-board power supplies. I was looking to see if these settings could be adjusted during image capture to reduce the voltages applied to the CCD. The idea was that this could give us a 'software only Amp-Off' modification controlled through the USB port. I guessed that the power supply circuits were similar to those shown in the Philips Application Note AN00065.

The power supply works as follows:

The CCD circuitry requires regulated +15V and -5.5V. These need to be generated from the +5V dc USB supply. They are produced using a single switching-mode power supply controlled by the SAA8112 (Vesta) or SAA8116 (ToUcam). The output from the switching transistor feeds a boost circuit to give a raw +18V unregulated supply and a buck circuit to produce the unregulated negative supply. The raw boost and buck supplies feed individual fixed voltage regulators that produce the steady +15V and -5.5V supplies needed by the CCD front end.

Unfortunately this means that adjusting the SMP output cannot readily be used as a way of independently reducing the +15V during exposure, to reduce ampglow. However, the investigation got me thinking about how the regulator could be modified to reduce the output voltage.

The Modification

Both regulators use Zener diode references to produce the regulating drive. The modification works by lowering this reference voltage during the exposure to a level that prevents amplifier glow.

Q1 acts as an inverter, to ensure that the when the parallel port is disconnected the regulator output is kept at +15V. With the parallel port connected and in the initiation state Q1 will be on, causing its collector to be LOW. Q2 will be turned off. The voltage regulator will operate in its normal mode with ZR1 regulating the output voltage through Q4.

When the parallel port goes low as a result of an AMPOFF signal from the software, Q1 will switch off, causing its collector to be HIGH. Q2 will start to conduct, effectively applying VR1 across ZD1 and D1. This lowers the voltage reference causing the regu

lator output to be reduced.

At the end of the exposure cycle, the parallel port is restored to 5V causing the regulator output to return to +15V ready for the readout of the CCD.

I'm sure that it is possible to improve on the circuit, but I wanted to minimize the modifications to the circuit I had already build for the Burri-Behrens Mod.

A single connection needs to be made to the 15V Zener reference at the point shown below. The positioning of VR1 is not critical. I made the connection to the Zener with a 6-8mm length of wire-wrap without any additional noise burden.

The output voltage of the regulator should be adjusted as a compromise between glow reduction and sensitivity reduction. I suggest starting with a voltage of about 14V and monitoring the ampglow reduction in 60 second dark frames. When you are happy, check that sensitivity is not significantly reduced by comparing AMP ON and AMP OFF light frames at 60 second exposures. You will need to take account of the natural increase in levels on the AMP ON frames caused by the glow, so test the levels in the bottom centre of the frame. The approach is necessarily iterative as the adjustment is a trade-off. You can monitor the regulator output voltage to earth on the large circular gold pad below the first 'n' in 'Connect Here', shown in the photo above.

The benefit of this approach is that there are no additional components added into the power supply chain. This minimizes the risk of noise entering the system.

The main disadvantage compared to other modifications is that it is not possible to reduce just Vdd. The 15V supply to the NEC uPD16510 and the O/P preamplifier are also affected. In practice this is not an issue as long as the voltage is not reduced by more than about 5V. If the voltage is reduced much further, sensitivity is reduced. I found by experimentation that a voltage drop of between 3 and 5 volts gives acceptable reduction in ampglow in 60 second frames, without reducing sensitivity.

I have tested this modification on my Vesta Pro Sc4 (ICX414AL) camera. I would imagine that the modification could also be applied to the ToUcam, though I have not had an opportunity to investigate this yet.

I hope that you find these instructions of interest and use. If you do attempt this modification, please let me know how you get on. All I ask that you agree to the following terms and conditions.

1. You will not distribute these instructions.
2. You will not place information derived from these instructions into the public domain. If you have any improvements or tips you would like to give others I will be happy to add these to these instructions, and acknowledge your input.
3. You will not sell a camera modified in the way described for any more than the value of the parts, unless all extra money is passed to MSF or Cancer Research UK
4. You will not sell a camera modified as described as part of a larger deal.
5. The instructions are provides 'as is' with no guarantees of being correct, accurate or even working. You agree to be responsible for any injury or damage that results.
   

1. ry or damage that results.
   

ICX414 - based Webcam

Introduction

In February 2003 Steve Chambers made another major breakthrough with the introduction of the SC3 Webcam modification. This involved the grafting of a Sony ICX424 onto the front end of a standard SC1 modified webcam. Amazingly, this was achieved with minimal modification to the webcam circuitry. An excellent and informative introduction to the SC3 mod can be viewed on Steve's website here. The page also describes how you can obtain details of the design for your own non-commercial use.

The Camera

When Steve first published images of the SC3 I was impressed with the quality and ultimate potential of the camera, but I had only just replaced the standard CCD in my ToUCam Pro with the monochrome equivalent of the ICX098. I had also studied the data sheets for the ICX4X4 series of chips. The ICX414 looked to have similar characteristics and basic configuration to the ICX424, but the CCD size was 0.5", with 9.9 micron, square pixels. This puts it in the same league as the CCDs used in the middle to high end SBIG and Starlight Xpress cameras, and we all know what can be achieved with these.

Procrastination on my part led to my missing Steve's bulk order for the ICX424, so I investigated the possibility of trading up to the untried ICX414. I obtained a quote from Framos UK, discussed my intentions with Steve.. We were both unsure of the sensitivity of the ICX414. Theory told us that it should be more sensitive than the ICX424, but this was not borne out by the information available within the datasheets. I decided to take the plunge anyway, as the image scale was a good match for my LX200.

Initial tests with the modified camera have been very promising. The camera is very sensitive and the dark current is extremely low at ambient temperatures. The following first light image was taken with 135 mm lens at f/2.5. The donor camera is a Philips Vesta Pro, which has a lower pre-amplifier gain than the TouCam. Even so it was possible to pick up a number of galaxies with only 2 second exposures!

Since this First Light I have developed a more robust mechanical and electrical design, the results of which can be seen in the gallery pages of this site.

In March 2004 I decided to re-house my camera in order to reduce its weight and size. I also took the opportunity to implement an advanced form of my Amp-Off design, which completely separates the CCD power supply from the supplies to the pre-amplifier, substrate bias etc. The following is a brief description of the camera, which I hope will give you some ideas for your own camera, should you decide to make one.

I wanted the camera to be reasonably compact to be suitable for use with my Borg 76ED and LX200 scopes. For the latter it was important that it would not be too deep, in order that views towards the Zenith would not be restricted (I have an NGF-S focuser). I also set myself the challenge of making the height and width of the camera less than 60mm x 60mm. My ultimate intention is to build it into a turned aluminium case similar to that used by the Starlight Xpress cameras. As an interim I have built the camera into a Maplin project box (Type MB1).

The image above shows the camera, filter pocket and focal reducer along with the various adapters needed to join up the imaging train.The camera is fitted with a PK T Mount adapter. Any T Mount would do as the bayonet or male screw has to be removed. I did this by carefully filing it off with a belt sander, so that it is flush with the case. The flange allows you to fix the cut down T Mount to the plastic box with screws. The filter pocket is made by True Technology. It has a flitter ring on the rear upon which I fit a 1.25" IRB filter. This cuts out infra-red (below Hydrogen Alpha) and also protects the CCD from dust. Note that I have combined the USB and parallel cables into a single multicore. I got fed up with tangled trailing leads. It seems to work OK.

Here is an image of the ICX414 and the T Mount ring. The CCD is mounted in 0.05" DIP headers that protrude through slots cut in the plastic box. I'm still sweeping the motes of case filings off the CCD window! The shiny case plastic within the T Mount could probably do with a coat of matt black paint at some stage. Note that I was able to re-use the USB cable strain relief on the new cable. Once it has been prised off the old cable it can be slid onto the new cable an hot-melt glued in place

Here is a view of the inside of the case. As you can see the design is based on a ToUcam, but it should be possible to use other donor cameras with different cases. Nothing is mounted in the body of the case, which acts as the lid. This gives good access. I may add a cooling fan in the lid at some stage, but as the ICX414 is blessed with low dark noise, so it is not essential. The single sided PCB was designed using PCB Express software. It supports the female headers for the ICX414 and male headers to join the pcb to the ToUcam PCB. Male Headers are soldered to the ToUcam PCB to allow the PCBs to be separated. The PCB also carries the basic 4066 Steve Chambers (SC) mod plus a complete Vdd supply circuit, with Zener Diode voltage control, fed from the ToUcam's regulated 15V supply. All the components apart from the SIL resistor array are SMT. I bought the 4066, zeners and transistors from RS Components. The rest I cut of old PCBs I had lying around. I used Julian Palmers excellent site for tips on how to best make connections to the ToUcam board.The PCB and case are screwed down to the adapted T Mount with 3mm set screws. This proves very robust in practice.

If you would like to make a PCB it can be done without special tools and a little patience. I used screen prints of the PCB Express design, Press-n-Peel PCB Transfer System (from Maplin), Solder paste (Thanks Ian), ready mix ferric chloride solution and a set of Hobbycraft type drills. If you don't fancy making the board yourself, PCB Express can make them for you, at a price.

Obtaining Details of the ICX414 based camera

The ICX414 based camera is related to Steve's SC3 design, and as such I will share details of it on the same basis. Steve has kindly offered the use his Sky Survey Emailer service to distribute this design.

In order to obtain the instructions to make this modification for yourself I ask that you agree to the following terms and conditions.

1. You will not distribute these instructions.
2. You will not place information derived from these instructions into the public domain. If you have any improvements or tips you would like to give others I will be happy to add these to the instructions distributed, and acknowledge your input.
3. You will not sell a camera modified in the way described for any more than the value of the parts, unless all extra money is passed to MSF or Cancer Research UK
4. You will not sell a camera modified as described as part of a larger deal.
5. The instructions are provides 'as is' with no guarantees of being correct, accurate or even working. You agree to be responsible for any injury or damage that results.

If you can not agree to these terms I quite understand.

If you can agree, and would like the instructions then please send a email to

greg_at_cosmicshed_dot_com

Subject: PMDO>SC4

Message must contain the exact sentence (including full stop):

I agree to the terms and conditions for the SC4 instructions.

The instruction will be send to you by email. This is an automated process. If you would like to send me an email please use the Email Me Link on the home page.

Webcam Modifications 3

Introduction

One of the side effects of the Amp-off Mod is increased image noise. Discussions on the QCUIAG group led me to experiment with noise reduction techniques. This ultimately led to a complete reduction in CCD noise. Unfortunately this was coupled with a permanent loss of signal from the CCD. That is what happens when one shorts pin 8 to pin 9 on an ICX098 CCD......

Desperate for replacement, and with no ready supply of 680s, I modified a ToUcam Pro. I wont go into the details here, but overall this is an easier camera to modify and is more sensitive than the Vestas. Ashley Roecklein's website gives a good explanation of how to carry out this modification. Although I constructed an SC2 daughterboard I did do the mainboard mod for the ToUcam; once bitten twice shy.

I used the Peltier arrangement from my prototype 680, to cool the airspace within the ToUcam's case, a plastic Maplin project box. The results were very disappointing, with hardly any reduction in thermal noise. I noticed, however that the main chip on the rear of the main PCB got really hot after a few minutes of operation. I figured that this was either due to heat transmission from the CCD, or was internally generated. Either way it must directly or indirectly contribute to thermal noise in the result images. I tested the hypothesis by extending the Peltier's cold finger so that it was in contact with the chip. Bingo, immediate and dramatic reduction in thermal noise levels. This arrangement was not practical, but served as a prototype for a new Cooled ToUcam Pro, described below.

ToUcam Pro Cooled SC2

Outline Specification

Rugged, yet light weight construction to suit operation either at prime focus of an ETX90, or with 35mm camera lenses on a barndoor tracker. Also scalable as a first CCD camera on an 8" scope, which I hope to be my next step up the ladder.

Capable of low noise operation at 75% gain for exposure times of up to 120 seconds. (I plan to standardise on 1 minute exposures, when I have the scope to match)

Buildable, at home without any specialist tools.

Design Concept

I started from the point of my Vesta 680 prototype. In this design I sandwiched the CCD between the front and rear of a alloy case. In this way there was no need to fix the CCD to the coldfinger. I also wanted the minimise the back focus distance, so that the camera could be used with a Newtonian scope (keeping my options open). The case was to have the minimum n

umber of openings in order to reduce the likelihood of dewing/frosting within the camera.

Here is an external view of the front of the completed camera. The alloy case is available from Maplin. It has just sufficient room to hold all the electronics. A larger case would have allowed silica gel drying. The PK bayonet mount is the front of an old tele-converter. The IR Cut filter is salvaged from one of my Vestas. (All lenses were removed). The mount for the IR filter is cut from the front of the original ToUcam egg, and glued to the alloy box lid in front of the CCD. The mini-Din socket is the connection to the parallel port.

And here is the rear of the camera. The cooler is a Golden Orb unit, available from Maplin. The small white project box, also from Maplin houses the connections to the Peltier and fan. There is no fancy control circuit yet, just a full-on 5V supply.

Here is the inside of the box showing the peltier and coldfinger elements. The Peltier is a 5V Greenweld unit. It is 30mm square, which fits nicely between the two piece of aluminium cut from a 30mm wide strip, available from most DIY superstores. The cold finger is a 10mm square off-cut from the same strip material. This is stuck together with heatsink compound and mounted on the round base of the golden orb. I used the original fixings of the Orb to fix it to the

box. It protrudes through a 32mm hole in the case. The spring in the Orb's fixing pushes the cooler assembly onto the PCB, when the box lid is screwed in place. Note the Vesta tripod bush to the left of the Peltier. This is used for Mounting on the Barndoor tracker, or piggybacking the camera onto a .scope.

The electronics are mounted on the back of the lid. This gives good access during construction and testing. Note the white patch where the cold finger rests on the large chip on the PCB. The PCB is connected to the case using the original ToUcam screws. The PCB is held square to the lid using an insulated aperture made from a nylon (?) off-cut. This is approximately 20mm square and 3 mm thick. A rectangular hole is cut in its centre, that is exactly the size of the CCD's glass window. This isolates the front of the CCD

from the cold interior, thus minimising frosting and dewing, and provides a stable mount for the PCB.

Note that I have isolated the PCB from the lid. I used shrink wrap tubing. The earth loop between the PCB screen and the lid was a source of electrical noise, manifesting itself as the dreaded 'diagonal patterning' or 'herringbones'. Isolating the screws removed all traces of noise.

Above the PCB is the SC2 circuit. To the right if the stripboard is the Amp-off relay. I have used the Burri-Behrens pin 8 mod, which uses a Zener to reduce voltage to the on chip amplifier during exposure. Instead of the PNP trainsistor I have used a relay in an attempt to improve noise immunity. I still need to work on this part of the camera. I think that the Zener, a 6.2V type could be raised in value, as there is still some glow in 100% gain, 120 second exposures.

Possible Enhancements

A machined coldfinger may improve thermal efficiency, though 120 second darks are acceptable.

A larger case would allow Silica Gel drying.

Webcam Modifications 2

I used the prototype for approximately 3 months with some degree of success. In the end I decided that a Peltier cooled camera was a bit over-the-top when used in conjunction with an ETX90. The tracking ability of the ETX drive could really do justice to the long exposure capabilities of the camera. With a 135 mm lens mounted on the camera, piggybacked on the ETX, it was possible to track objects, without trailing, for no more than about 40 seconds. At these exposure times it is debatable whether Peltier cooling is worthwhile. It was also a chore to set up the power supply each time. Also, the weight of the camera was taking its toll on the ETX drive.

Two Tune-Ups later, enough was enough. I decided to take a soldering iron to my trusty Vesta 675, with the intention of building a more practical long exposure webcam.

Vesta 675 SC2, Fan Cooled

I got rid of the egg case and mounted the CCD, still in its metal enclosure, and the circuit boards in a Maplin Project Box. The box is long enough to mount a 12V CPU fan in the base. The fan is mounted to suck hot air out of the box. I drilled holes around the front of the box where the CCD is mounted. In this way the cool air first hits the CCD and is then drawn over the electronics and into the fan. The fan is powered straight off the USB 5V supply. The daughterboard with the 4066 circuit is mounted underneath the main board.

Using an extract fan allows you to control the flow better. Cold air is drawn in by the fan, where you want it to be. In my case the cold air hits the CCD area first. It is then drawn over the circuit boards. In this way I get maximum possible cooling of the CCD, and the hot air rising off the PCBs is drawn away from the CCD, through the fan. This arrangement cools the area around the CCD to within a degree of room temperature. With the fan disconnected the temperature inside the case rises by 8 degrees Celsius.

The CCD enclosure and circuit board are fixed to the box with the threaded body
of the original lens unit. The original lens is removed, through the front of the holder, after breaking off the bezel in front of the IR filter. Keep the IR filter. This can be remounted as shown in the next photo.

The parallel port connector is on the LHS of the box. It is a 5 pin mini-DIN socket. I use a lead from a trashed mouse for the connection to the parallel port. I mounted the tripod socket in the base, insulated with tape, to prevent shorting of the daughterboard circuit tracks. The Box is a Maplin YU53.

The fan is a JAMICON Model JF051SIM. Its rating is 12VDC 0.08A. Diameter is 47mm. I salvaged it from an old 486 PC. You should be able to get a similar model from your local pc dealer. Make sure that the fan turns very easily by hand. Some fans are quite jerky as you turn them. Those ones are unlikely to work off the 5V USB supply (I know, bought one).

Here is an exterior shot of the completed camera.

Note, I've now replaced the original lens mount with the PK bayonet from my 680 prototype. I found that the plastic lens rear protector was not secure enough to hold my 200mm telephoto lens.

With this camera, I have been able to produce my best images to date. It is light weight, provides adequate cooling to allow 40+ second exposures without saturated hot pixels, and it also looks the business, in my opinion.

Even more modifications.

Webcam Modifications 1

The first camera that I bought was back in June 2001, a Philips Vesta Pro 680. This was recommended as a good camera for planetary imaging, being sensitive and easily adaptable for prime focus work, with a Mogg Adapter. This is a 1.25" tube that screws into the body in place of the original lens. These adapter are available at reasonable prices from Steven Mogg's Website.

In October, Steve Chambers developed a long exposure modification to the Vesta and ToUCam webcams. This coincided with Philips discontinuing the Vesta 675 and 680 camera range. For a very short time it was possible to pick up a Vest 675 for just 25 GBP. I bought one as a backup in case my 680 mod failed. With hindsight I wish I'd bought a few more! The mod to the 680 went according to plan, firstly confined to its egg case, and latterly as a Peltier cooled prototype.

Please take heed of the copyright condition associated with this modification which Steve Chambers has generously made available for persoanl use. The notice is viewable here

Peltier Cooled Prototype

Here is a brief description of my Peltier Cooled SC prototype:

Tne concept was to re-case my Vesta Pro SC in a larger case that would allow cooling of the CCD. I had an aluminium Eddystone Box, which was about the right size, and one of the QCUIAG members had found a cheap source of Peltier coolers at Greenweld . I ordered two Peltiers and after a couple of trips to Maplin Electronics, I was ready to construct a Vesta Pro SC2.

The chassis is the lid of the Eddystone box. The heatsink and fan module is a Socket 7 CPU cooler, the face of which protrudes through a slot cut in the lid. Self tappers fix the fins to the lid. The 6V Peltier is sandwiched between the heatsink and the coldfinger. The coldfinger is made from 25 mm square section aluminium, cut and bolted together. The clamp bolts are isolated from the heatsink and coldfinger using insulating sleeves. The fan and Peltier are wired out to a standard 'co-axial' power connector. The fan is permanently on, but the Peltier is switched.

Removing the CCD from its PCB was fun...two evenings worth (magnifier, soldermop and 15W fine tipped iron). Here it is shown clamped to the top of the coldfinger with self-tappers. The clamp/window was made from an off-cut from a CD case. The CCD PCB was drilled and screwed to the lid. The main PCB (not shown) is also supported from this, on its connector. I tried to keep the leads to the CCD as short as possible (~ 6 cm).

I dismantled an old Pentax fit 2x teleconverter, to give me a sound means of mounting either 35mm camera lenses or a range of T Mount telescope accessories in front of the CCD.

This picture shows the completed camera. In front of the Pentax PK bayonet mount is my home made focal reducer, made from a 8 x 35 binocular objective mounted in a 20mm M42 extension ring.

Note also, that I have adapted the tripod socket from the Vesta, for use in the modified camera.

Testing

After a cursory inspection, I plugged into the PC. All I got was a garbled noisy mess. I wasn't surprised, considering the heat I'd applied to the CCD trying to extract it! On closer inspection (of the CCD and its datasheet) I found that I'd got pins 1 - 7 of the CCD wired backwards.

After re-wiring I gave it another go and amazingly the camera worked perfectly, with no noticable patterning/dead pixels etc. The Sony CCD appears to be pretty bullet-proof.

For the tests, the Peltier PSU was a plug-in battery eliminator rated at 1A. I measured current to Peltier at 2.1 A. I later built a high capacity (25 A max) power supply, using a standard 250W Desktop PC switch mode power supply.

Under Pelteir cooling a thin layer of ice formed on the coldfinger. In use exposures in excess of 1 minute were free of hot pixels, at maximum gain.

Removing the CCD is harder than doing the basic SC Mod, but the unit can take quite a bit of abuse, as I have demonstrated.

I later added the standard Amp-Off Mod, to cut out electro-luminescence caused by the CCD's on-chip pre-amplifier. This significantly improves the performance of the camera for exposures of more than about 30 seconds, at maximum gain.

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Total Solar Eclipse - Turkey 2006

This is a record of my personal experience of the Total Eclipse on Wednesday 29 March 2006. Like many others I failed to witness the eclipse that crossed the South West of England in 1999. That had been a great disappointment for my Wife and I. She had been especially looking forward to it as she had spent her childhood in Devon and had been looking forward to it since then.

I read the advert in Sky at Night magazine and decided to book us both on the trip the next day. It was something to look forward to over the Winter. It hadn’t dawned on me until a couple of weeks before the trip that there was a real possibility of cloud ruining the even. We looked at forecasts and weather records, and these seemed to confirm our fears. Three days before the eclipse most of the forecasts were for a good weather window on the Tuesday and Wednesday, but bad weather moving in on Thursday. I know it’s irrational, but we decided not to take any sunhats, sunglasses or sunscreen, in case that put the mockers on us.

We flew out from a damp and cloudy Birmingham early on Tuesday morning with a like-minded group of eclipse chasers. I think the hold must have been empty, what with everyone entrusting their kit to the overhead lockers. We were greeted at Antalya by hazy sunshine – looking good so far. After an hour and a quarter coach trip we arrived at the hotel. We were about 1,000th in a queue of 1,500. Whilst slowly shuffling forward I heard a voice, “Hello Greg”. I turned round to be greeted by Nick King, who had just arrived on one of the last coaches. That was a nice surprise. Eventually the tour organisers got there act together and we collapsed into our room. After a quick recce of the hotel and beach we were served dinner – more queuing, but worth it. Then followed a very interesting and entertaining presentation on what we hoped to see on the next day, by Pete Lawrence and Chris Lintott. Later on I went down to the beach, where some other astronomers were viewing the heavens across a calm sea. Orion was just starting to set as I returned to our room. The expectation was almost unbearable.

After a restless night I got up at about 5.30. I stumbled out onto the balcony to confirm that, yes, I could see stars. The sky was totally clear. Promising, but there was still around eight hours to go. At breakfast you could sense the excitement and expectation, but there was still a chance of disappointment as small wispy clouds were forming over the mountains behind the hotel. I kept telling myself that there was an onshore breeze – stay positive.

At about ten o’clock I went down to the amphi-theatre where I could see a number of scopes set up. Nick was there with his Dad, all ready to go, and looking cool in his shades. After admiring his set up I turned round and there was Eddie Gusgott, complete with his G11 and two scopes. He assured me that this was his lightweight portable set up; very impressive. We had a good chat and I had a chance to look through double-stacked SM40, which showed sunspots and prominences with remarkable clarity. By now I was thinking it was time to stake my claim to a spot on the beach.

We got organised with a couple of sun loungers and I set up my camera and tripod ready for First Contact. I took shots at 20 min intervals to capture the partial phase. This period seemed to pass agonisingly slowly, but with about twenty minutes to go things started to change. It became increasingly difficult to focus through the viewfinder and strange fuzzy shadows were cast around us. It was fun to project the sun through pinholes in my note book, throwing crescent shaped ‘suns’ across the sun lounger. A few wispy clouds were forming to the North and West, but didn’t threaten to spoil the show. It was clear that we were going to be in for a treat. By now it was getting pretty cold, and the light was weird; very low contrast, and a yellowy-brown hue; like the sunlight you sometimes get after a storm, but rather subdued. The horizon across the sea to the South West started to darken and take on the colour of a subtle sunset. Venus could be clearly seen, bright, low down to the South West.

Then it happened, as if a switch had been thrown it went dark, not dark-dark, but like twilight. I looked up and there it was, a hole where the sun should have been, surrounded by a steadily growing corona, as our eyes became dark-adapted. All around us people were gasping a whooping with joy and excitement. I just stared, transfixed by the sight. I then looked around to the West, North and East. The high whispy clouds had been painted with deep reds, oranges and purples, against the backdrop of a deep blue sky – a 360 degree sunset. I did manage to grab a few images, but all time I was being drawn back to the live event developing in front of us and enveloping us.

Suddenly there was a bright flash as the sun reappeared from behind the Moon, hanging in the sky like a bright magnesium flare. The sea and sky brightened as the shadow proceeded on its journey northwards, and it was over. We all looked around at one another, sharing our experiences and emotions. I tried to continue with systematically taking images of the partial phase, but lost all track of what I was really doing. It was a time for sharing with my Wife and relaxing.

On the way back to the hotel I met up with Nick and Eddie who were packing up. We shared our experiences and said our goodbyes, as it would not be long before we would have to be on our way, back to a different reality. The eclipse had touched us in different ways. For my Wife it had ful-filled a childhood dream that had been dashed seven years earlier. Serious health problems had all but dashed here chance of a second seeing an eclipse. She wants to see another one. I was impressed by the experience, but felt that once would be enough - closure. As we packed up I felt uneasy, as if I had missed something. It was only when I was travelling back on the plane, reliving the experience of Totality that it dawned on me, just what I had witnessed. Something that cannot be seen from anywhere else in the solar system; the Sun’s corona, its affect on us and how we see our own planet. It still brings a lump to my throat when I think of it as a write this. The chance to share this with others is the reason that I hope to make at least one more eclipse trip in the future.