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.

More Modifications

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.

The North America and Pelican Nebulae in Cygnus

VC200L Setup

I finally got all the parts I need for my VC200L high resolution imaging rig. The tube us equatorially mounted using R200SS rings (232mm ID) and a Losmandy style plate.

The guidescope is a Borg 60ED refractor with front focuser option. This is mounted rigidly to the Vixen rings using the new Borg mini rings and an aluminium plate. It time I will replace this with another Losmandy plate so that I can break the rig down without using a hex key and move the guidescope to my other imaging scopes.

An initial tests last night showed no flexure or mis-tracking evident in 500s sub exposures with the VC200L operating at ~f/18.

The Borg 60ED may seem a bit over the top, but I will also use it as a 'grab and go' scope. the optics are excellent and the Borg system is very adaptable, if somewhat confusing!