Carbon Brush

Good warning from Merkhet. I seem to remember something from school chemistry lessons about the acetylene being dissolved in acetone. If so, that would provide Mrs Freff and all her friends with a lifetime supply of nail polish remover!

Watching with interest. As an owner of the (once unique) vixen model.

Further to Dave's comment. Yes there is plenty of power in reserve. However, an external distribution and protection network is required. If there is a short circuit in the wiring, or your kit, what happens? Well the shortform data on the web page doesn't actually state the output will withstand short circuit without damage. If it won't stand a short, it could well fail. I would establish first if the power supply is short circuit proof. I wouldn't bother asking Maplin. Their technical advisors are, in my experience, less than useless. Find out the direct way. Stick a reasonable load on the output. Say a car brake light, or headlight. See that the supply is 12V (or whatever is set) and providing a little under 2amps for a brake light, or 5amps or so for a headlight. Now the exciting part. Put a piece of heavy wire straight across the output terminals. Something the thyickness of cooker or shower cable. The bulb will be off. Voltage will show near enough zero. Depending on the type of overload protection, you might see 30 amps and more on the meter, or it might shut down to zero. If there is 30+amps, hang your nose over the case and sniff for burning. Leave it like this for a minute or two. Unless smoke issues forth! Remove the wire short circuit and check the bulb comes back on. If not, turn the power off/on and see that the supply recovers. If you have broken the supply, send it back for refund. If it is OK, you can proceed further. This involves thinking about a distribution network with small value overloads/circuit breakers/fuses for each item of kit. Why distributed? Suppose the power supply happily provides 30amps and more into your load. That is the sort of current that can be used when welding thin sheet metal. The thin wires on things like mount power cables become effective heaters to the point of melting plastic insulation. If there is a fault within a mount, you could well end up with cooked components that render the drive a toasted write off, rather than repairable. If you had protection that trips at a couple of amps for a mount, you won't get the red light of burning circuits if there is a fault! One example is the grotty plastic DC plugs used by many mount manufacturers. Leave one of these passing 30 amps and more for a minute and it will melt, or catch fire. A power distribution and circuit protection network is not difficult to build with only basic soldering skills. HTH David.

Wow. This runner arrangement makes my construction look like something from Messrs Heath & Robinson. I used decent size nylon fixed castors on the roof. These run in a half round PVC channel. This is a posh term for PVC waste pipe cut in half lengthways and screwed to timber. 9 years on, still working well. There are many ways to keep the roof from blowing away. I worked on the basis that if a gale is blowing, I'm not going to be opening the roof. It therefore only needs to be held down when closed. Long bolts are fixed to the 'moving away' end of the roof. These point back towards the shed, fitting into holes in the top of the shed frame. When the roof is closed, the bolts prevent any roof lift. At the end of the roof that moves from one side of the shed to the other, I have some L shape brackets pointing down. When the roof is closed, holes in the brackets engage with bolts fitted through the top of the shed wall. This course pevents roof lift. A benefit is the L brackets provide travel stops so the roof can't move too far if the motor drive loses datum. Adding a couple of washers and wing nuts to the bolts prevents roof slide and gives security. HTH David.

I have been away from this topic for a while. I do like the idea of a polycarb panel roof. That means you just need a strong frame around the edge. I used some (low cost from Wickes) panels on a garden shed roof recently. In this case It was in the form of a clear panel leaving a reasonable amount of original wood around. They were easy to work with and very light. Should my observatory require serious roof repairs in the future, I would definitely think polycarb. We have all seen them used for conservatory roofing. The only potential downside of polycarb, that I can see, is security. Using low cost/low weight panels, it would be easy to break in. But there are ways around this. HTH David.

Is there any chance of you having a scope on a semi permanent fixing? Obviously an observatory is the ideal. But putting a big scope on a wheeled trolley is a half way house. Store in a shed, then wheel out when required and use jacking screws to keep it firm. Another option is to make an OTA easier to carry. I used to have an 8" newt that travelled a lot. I fastened a large alumuinium bar handle to the rings for easy carrying. The at prevented many potential OTA drops when fastening the dovetail to a mount. Just a few thoughts. HTH. David.

What brilliant simple idea. Leaving a couple of fingers permanently covered. My best astro gloves were a Christmas present from my son. They are thick and warm 'greengrocer' fingerless. But with a mitten style finger cover stitched on at the knuckles. This has velcro and folds back towards a velcro pad on the wrist to allow twiddling, then can be pulled over your fingers to keep warm.

As Astronymonkey says. Why clean? Mirrors can be really awful to look at but it hardly affects the view. Mirrors do not have the hard coating you are used to finding on lenses. It is extremely easy to cause more damage than you think. I would need a lot of persuasion to do anything beyond a clean air blower. Whether a hand operated lens blower, or a can of clean compressed air for computer parts. Hope this helps. David.

Think about the tracks and wheels. In your drawing you show round profile wheels running in rectangular section tracks. For my roof, I added a semicircular plastic track to keep the wheels aligned and ensure the roof slid correctly. Being miserly, I used plastic waste pipe fed through a band saw. Then a few countersunk screws to hold the plastic track to the wood. A weakness of this design is that in cold weather, the exposed part of the track gets iced up after snow melting. So when you get a clear sky after (the wrong sort of) snow, you can't open the roof! Fortunately this has not happened often enough to force me to spend on, or think about, a solution. David.

Hi Lewis. You are getting lots of good advice from everyone. On the ROR idea - give it some thought. My obsy has the appearance of a garden shed with a pergola alongside to hold the roof when in use. So it is acceptable in a garden. I had been told that the idea of a 'bottle recycling container' in the garden was not really acceptable. Why ROR? When you finish a session. Whether it be bedtime, too cold, or cloudy, the ROR is very quick to abandon. I just park the scope, slide the roof on and everything is closed up. Next time out, slide back the roof, tell the mount to go and you are back where you started. No algnment, no cables to connect, etc. If you are really lazy (like me) then you can motor drive the roof using an auto garage door mechanism! I went over the top on pier foundation. Well over half a cubic metre of concrete as a not very rectangular lump. But concrete is cheap and in my view, if you are not sure, put in more than you need. Rather than using ready mix bags, I bought the materials from a local builders merchant. When you calculate the approximate volume of the job, they will advise how many tons(?) of material you need. By using a portable dement mixer, you can shift a lot of cement without too much effort. I found someone with a mixer who was happy to mix and pour for a few quid. Session 1 was pouring for the pier. Then a few days after, pouring for the shed base. Did I go over the top on the pier? Perhaps not. At the design stage and while building, I was using an EQ5 & 8" newt. But had a bit of an idea I might get something a bit bigger in a few years. Then the Alter D6 with Intes Micro MN78 came up 2nd hand at a good pricce. The D6 mount is around 35Kg. The scope comes in around 20Kg, depending on add-ons. Definietly not a package for a minimally built pier. The only downside of the ROR is that you cannot use an 'off the shelf' shed. Invariably sheds rely on the roof for rigidity. So you end up with additional timber in the walls. The standard shed roof stays flat because it is fully supported on 4 sides. So work is needed here. The door only needs to be large enough to get you in/out. You don't need to fit wide/tall items. Reducing door size helps with strength and security. There is a lot elsewhere on SGL about shed building. I would recommend using butyl rubber pond liner for any shed roof, rather than ordinary felt. It remains flexible and waterproof for years (9 and still going strong for mine) and weighs less than decent roof felt. Hope this helps, David.

My first comment is on cabling. For mains from the house, you need either armoured cable, so you can't put a spade through it, or a good quality cable duct/trunking. don't forget the RDC (residual current device), also known as an 'earth leakage breaker'. If you plug into an existing 13A socket, you avoid the electricial approvals headaches. Provided you are confident of your work. When running 12V power from shed to pier, use heavy cables. You are going to need to run motor, dew heaters and goodness knows what else. Flexible stranded wires are good and easy to work with. Go to a car accessory shop that specialises in loud audio. They need heavy cables. Alternatively a few metres of twin and earth mains cable is an easy low cost method. Minimum 2.5mmsq (ring main) or even 6mmsq (cooker). Though not so flexible. At each end terminate into a box with large and good quality terminals. Not nylon 'chocolate strip'. Why not throw a few extra low power/signal cables in there? A good quality USB lead. Some 4 core phone/alarm cable for unforseen additions. After all this, leave a piece of strong nylon cord in there to pull through anything else you haven't thouht of. Cable is cheap and can make the installation future proof. Finally on cable. Bury round drainpipe as a shed to pier cable duct. If you leave lots of space in the duct, you can add or replace cables as required. Now the pier. If you want a metal pier, why not run up a crude sketch and present it to a local fabricator? Use stainless steel so you can forget painting. I have a stainless steel pier made by a fabricator that is sitting around unused. It is heavy enough for your setup. But I had other ideas. My pier is concrete. Simply an extension of the underground bit. I scrounged a length of round (galvanised steel) ventilation duct. When the concrete got up to ground level, I planted the duct on top, then started filling the duct. Obviously continually checking for vertical as I worked. At the pier top, I have a paving slabthat I had made round. then drilled 8 holes through and fixed stainless steel studs about 20cm into the wet concrete and 10cm above the slab. Walk away for a few days until the concrete cures and you have a very solid pier that doesn't ring like some metal piers. As I wanted flexiblity on mount type, I took an old car brake disc, drilled 8 holes to line up with the protruding studs and fastened the mount to the centre hole, as if it was on a tripod. The brake disc is actually the most flexible part of the assembly. But it came in really handy when playing around with different mounts. Hope this helps, David.

You can't be there for everyone all of the time! We (customers) have to be realistic about order handling during holidays and out of normal hours. At work we have had angry emails from middle east customers demanding to know why we were not answering the phone on Sundays We had adverse comments from a USA (Nevada) customer demanding to know why we were leaving so early in the day. Time zones did not occur to him! A Scotland customer thought we were offering a rather slow delivery on an urgent item. It was 7 hours (9am ship, 4pm delivery) for 300 miles. Could we offer anything quicker? Something about keeping all of the people happy for all of the time? Will there be a free Christmas cake included with every December purchase FLO? To help you, I will make an offer. Send me a selection of your finest scopes and accessories. I will ensure they are kept in tip top condition by regular use. Should you have a buyer local to me (50 mile radius?) then I will offer to deliver it, including out of hours if requested. You regularly replenish my stock allowing this service to continue. Hoi! I thought of it first. Anyone else - Form a queue! FLO have had the lions share of my new astro purchases for about 9 years and I have recommended them to others. There never been anything to make me reconsider this. Keep up the good work and happy new year to the team.

If you have half decent soldering skills, then you can easily enough make your own leads. That way you get to choose the type and quality of connectors. And of course cable length/type. A deliberate weak point in a trailing cable can prevent equipment connector damage. Or even pulling over the mount. On power pack choice for holidays. Airlines are getting understandably fussy. The Tracer packs have 'UN38' approval for air transport. You can wave this at security/baggage people in the event of argument. Looking on the FLO site, there is no mention of UN38 for the Celestron power unit. Hope this helps. David.

Marginally off topic. But here goes. In my work, I have designed in, and used lead acid, NiCd, NiMH, lithium both rechargeable and primary. The lithium work has ranged very low discharge primary with several years life. Through to equipment running at 150C. Yes oven temperature. The big benefits of lithium are.... Very good power to weight ration. Easily 3x lead acid. Very good power to volume ration. similar gains. Very good performance when cold. Lead acid and NiCd/NiMH bother suffer the cold. Very good life expectancy. The disadvantages are..... Cost. Perceived risk from self destruction. Don't trust this new fangled technology. So what does this mean to us? Compared to lead acid, If your battery pack is light, you can keep the hand cart for your scope and more. If you don't keep your lead acid topped up regulalry, it will fail in a non-recoverable manner. Lithium self discharges at only a few percent annually. If you want to deep discharge a lead acid to the point of damage, that is your choice. Again if you want to boil it dry with the wrong charger, you can. If you want to wreck it by short circuit, you can. Additional circuits (rarely implemented) are necessary to protect against the above. Why fit them? It is an extra burden on a cost conscious item. If you have to pay someone to do this, then you start to approach NiMH and lithium costings. Lithium packs usually have internal circuits to prevent over discharge, or over heating, and short circuit protection. They are therefore self protecting. A lead acid battery degrades daily, even if not used, stored well charged and not subject to temperature extremes. Lithium is much less susceptible to degradation in storage. If you want a bettery that performs well and looks after itself in a dark cold field, choose lithium. If you want the battery to look after itself between clear nights, choose lithium. If you want minimum cost, protection circuit construction difficulties, degraded performance on a cold night, regular top up between uses, choose lead acid. I have an infrequently used 'Sunday' car that uses an AGM battery. It needs more attention (trickle charge etc) than conventional lead acid. To me, if you have the budget for the inital outlay. The choice is obvious. Hope this helps. David.

Sheds are good for storage. I agree very much with the earlier comments. They don't stand out from the crowd. The casual thief will think your shed contains much the same as any other shed. Lawn mower, spade, wheelbarrow, etc. You do not single yourself out from the neighbours for attention. I have kept my astro kit in a (much modified) shed from a local shed builder for about 9 years now, without any big issues with security, damp, livestock, etc. I have applied various security measures. Both physical and electronics based. The physical measures are very difficult to see from the outside. Huge locks, bars and fortress grade hinges are a bit of a hint of valuables inside. As a general rule, if the 'normal' break in technique hits obstacles caused by the hidden physical measures, the villain will move on to another target. They generally want to get in and out again quickly. For 'technology based' protection. A thin wire running around the walls to pick up on a board being removed (as mentioned in an earlier post) is just one measure. Control using an after market vehicle alarm with key fob control is a good idea. If chosen correctly, these are designed to withstand the condensation and wide temperature range encountered in a car/shed. Many non professional indoor alarms can't cope below zero or over 30C. Vehicle alarms readily accept multiple inputs with an indication or log of the trigger source. Switch inputs for car bonnet, boot or door opening. Now the shed door or removeable roof. Ultrasonic sensors for movement inside the car. Now inside the shed. Shock sensor for car park nudge. Now hammering off the door lock, or prying off hinges. I won't go into too much detail in open forum. But you get the idea. HTH David.