Carbon Brush

Now sold. Thanks Ade.

Yes unused big things have to be moved on. To me, the biggest problem with a dob like the SW200 is the finder. I just cannot get on with a straight finder on any scope that has the eyepiece sticking out of the side. Would adding a few ££ to the new price for a right angle finder really lose sales? David.

Recently my improving(?) skills with a 3D printer have allowed me to make a handset holder and a 10" dust cap. I have seen members talking about making other astro bits and pieces. Is it worth collating astro related designs somewhere on SGL? Assuming of course we are all prepared to share our designs. My thinking is that it avoids searching through all the fantasy figures, toy boats and mug holders posted on thingiverse and the like. The possible issue for SGL is that every design involves posting files to the site. Would this be too much? Comments please.... David.

I had to take a look on Amazon. £30.55 hardback and more money for used paperback editions. Strange. Has anyone on SGL read this book? Comments on content? Is it really complicated and full of maths that looks like a musical score? David.

About 14 years back I bought an Orion Optics 200mm reflector. It came with a tripod very similar to yours. Yes the modern steel pipe tripod is better, but my ali tripod didn't fail. Have you used the kit and found problems? Hope this helps, David.

May I throw another item into the discussion? When you look at a 12V lead acid battery, you are given figures for voltage and capacity (amp hours). For example 12V and 20Ah. The total energy available is 12V x 20Ah = 240Wh (watt hours). When you buy a Tracer (or similar) pack you are told the power delivery in the same way. So a 12V 22Ah pack will deliver 12V X 22Ah = 264Wh. However, the chinese sellers on Amazon and ebay sometimes play specmanship, or cheat, or omit detail. Take your choice on the interpretation. You will have seen power packs to provide 5V for phone charging, etc. These use a 3.7V single lithium cell and a circuit to stup up the voltage to 5V. The advert states it gives 5V and is (for example) 10Ah capacity. You might then expect it to provide 5V x 10Ah = 50Wh. But they are referring to the capacity of the 3.7V cell. This means in reality you have 3.7V x 10Ah = 37Wh available, less the step up convertor efficiency. The actual power from the pack is going to be more like 30Wh. If you don't follow the maths, don't worry. Just send me £50 and I will send you £30 in return. A similar trick is played with the 12V output packs used for car jump starting. A pack comprising 4 cells each 10Ah is described as 40Ah. You actually have a 12V 10Ah battery pack as the cells are series connected for use! Check the specification carefully. The bargain battery may not be as good as it seems. Especially when you consider the risk of the chinese stuff not being properly constructed in the first place. If a manufacturer is going to lie about the specification, can you trust anything else about the product? Yes I have a few horror stories about lithium batteries. Including a 'Segway' copy battery pack (approx 720Wh) failing and replacements that were not UN38 certified being sent by air freight. Fortunately no aircraft caught fire and crashed, this time.

My first choice is Baader Wonder Fluid for lens cleaning. It copes with all sorts of deposits. From pollen on objectives to spit on an eyepiece (yes really but that is another story). My simple philosophy is that if Baader fluid wrecked anything, especially glass with their name on it, and word got out, they could be in big trouble. So would quickly put things right. The simplest method being prevention. Ensuring the fluid does no harm. As I own some Baader Hyperions, a Baader zoom and some Baader filters I am in a good position to say I have never had any issues! I also use the lens cloth available (at cost) with the fluid. Lenses are generally very hard coated - unlike mirrors - so can tolerate quite a bit of abuse. But you did not hear that from me. A bottle of decent cleaner and a cloth of known quality are very cheap compared to most scopes. Hope this helps. David.

A thumbs up for the Steppenwolf cleaning technique and tips. I have used deionised water without problem. My final rinse being a mixture of water and isopropanol. This reduces surface tension (gives a uniform wet coverage) and dries without marks. But of course, is the mirror really really really dirty? Can you leave it for another day? David.

Sorry but I have to argue. At work I have been using (and throwing away) lead acid gel cells for 40+ years in a wide range of equipment. Regardless of how well you look after them, they degrade on a daily basis. There is a cumulative loss of capacity and increase in internal resistance that is a consequence of the construction. I first learned this from a manufacturer of high quality cells and battery packs. This is a temperature dependent factor. If you want the cells to last longer, keep them in the fridge until they are needed. Any cell that is several years old will have suffered significant capacity loss. It is just that if you only use a fraction of cell capacity in a session you don't notice the degradation. As an example, our work burglar alarm has lead acid backup. In the annual test, the battery is swapped out if it is measured at 2/3 original capacity, or at 5 years, whichever comes first. In practice, these batteries (stored and used at reasonable temperature and kept properly charged) are thrown out well before 5 years. At work in new equipment design I no longer specify lead acid. NiMH/NiCd sometimes, but increasingly Lion. At home, as my old battery packs in torches, scope kit or anything else require renewal I am tending towards lithium. For astro work lithium gives far less performance fall off at freezing type temperatures. Lithium has typically 3x the power to weight or power to volume ratio of lead acid. Less to carry into the field. When you buy a lithium battery pack, it often has included circuits to prevent over charge, over discharge and charge at too high temperature. This is going to ensure you have a product with long life. My experience has been that the quoted cycle life is often exceeeded. Don't forget the cycle life is often quoted to 65% or 80% of original capacity. It depends on the manufacturer. As battery does not suddenly stop working at 1000 cycles or whatever is quoted. Further if you buy a pack tht has UN38 transport approval - like the Tracer packs in the UK - you are assured that you have a pack that has been subject very rigorous testing. It is not going fail catastophically like some (or is that a lot) of the chinese imported stuff. Hope this helps, David.

If the mirror is slightly dusty, ignore it. Mirrors have to be very dirty to affect image quality. Any cleaning carries risk.

Glass lenses. That is eypieces and 'the front bit' on a refractor or compound scope have good coatings that will withstand mild chemical cleaning and abrasion. Like Baader Wonder fluid and the cloth. As a comparison on lens cleaning, I know that spectacle lens coatings fragment and peel after multiple cleaning operations with neat isopropanol. Which is a fairly mild solvent that is used in many cleaning applications. The canned air products are a bit of a risk. Some are clean and dry gas. With a pure propellant. Others are not so good. It depends on the manufacturer. If particles are so small they don't block the nozzle, does that pass the quality test? If the gas and propellant don't contain too many oil droplets from the compressor used to charge the canisters, that is OK. Before spraying canned air at a (soft) mirror coating or lens I would refer to the manufacturers data on product purity. NOT the sellers data. If you can't get the information from source, look for something else. Products for sale in the EU from reputable distributors have the manufacturers safety data sheet available and sometimes a purity statement. Examples of products from just one UK supplier are in this link. https://www.rapidonline.com/air-dusters You will see that product data and safety information is included. Though a quick glance did nothing to assure me there was not going to be oil spray or grit blasting. On your diagonal, I would be very tempted to ignore the problem. If it really is a problem then squirt with Baader fluid. When it dribbles off, it won't harm painted or finsh on the diagonal metalwork or plastic. Hope this helps, David.

Fully agree with the above post. Optics have to be really really dirty before you consider dismantling for cleaning. The loss of image quality is minimal even with really mucky mirrors and lenses. Deposits on outer faces of lenses can be easily cleaned. I use Baader Wonder fluid. I know it sounds like a well marketed kitchen surface cleaner. It is an excellent lens cleaner. FLO sell a package of fluid and good quality lens cloth. Some consider it expensive and have their own recipes. But compared to a scrap scope? A 100mL bottle lasts ages. Mirrors are a different matter. They are best untouched if possible. Nothing more than agaitated liquid. If the marks are fungus rather than dirt, they need to be addressed as they will slowly grow and wreck coatings. But there is no need to rush out today and do something today. It is slow growing. Take advice and consider professional cleaning. Hope this helpsw, David.

If you are outside, and you do not anticipate exceeding EQ5/6 weight limits, then there is a good argument for putting the SW pillar on a concrete slab. You can buy bigger/better steel pillars with larger price tags. A 10" or thereabouts concrete pillar wil lnot ring like a steel pillar and if you get fed up of stargazing, you can put a car on it! This comes back to foundation & pillar pouring. In practice you getting a barrow full of concrete, then there is a pause while more is mixed. From what I remember (about 11 years back) a combination the pauses in pour, and having decent ballast, meant that the pipe did not empty. Concrete was tipped into the foundation and when we got to the top, I bedded the steel tube onto the wet concrete and arranged the 'keep vertical' bits of wood. I don't remember any issues with the steel tube emptying. Hope this helps, David.

Hi. my two pennorth.... 1/ Pier diameter. Put your scope on the mount you intend to use, on a tripod. Tilt to the zenith and measure the distance from tripod centre to scope tube. That will give you an idea of what restrictions a fat pier or big brake disc will give. 2/ Pier height. Is the pier outside? Will a shed follow? The higher the pier, the nearer you can view to the horizon over nearby hedges, shrubs,etc. Assuming you are bothered about a low angle view. But you are more exposed to wind, street lights, etc. Taken to an extreme, you then need a step ladder to use the scope. My pier is in a shed. Maximum pier height was dictated by the mount, topped by a level 10" newt OTA and roof still sliding. That was the biggest (fattest) scope I could forsee getting. 3/ My pier was made in one pour. I got everything ready. The man with the cement mixer mixed and barrowed. That left me free to check heights, levelling, etc. Hope this helps, David.

Compatibility is the bane of technology. Unfortunately we all demand connectivity with the latest phone/tablet devices that invariably have a short life. A year or two. Fashions change in the consumer world. There is a long list of obsolete/forgotten interface methods. IEEE488, parallel, firewire to name a few. Then we buy astro kit that we hope will last for years. I use an AWR motor drive & handset on my mount. This uses RS232 comms to the computer. The kit is 10+ years old and nowhere near end of life - thanks to good design and construction by AWR. I fully expect to be using this kit for quite a few years. In my work, I use machine to machine, and machine to computer comms. Nobody in their right mind is going to spend five & six figure money on machinery that cannot talk in a year or two. Laboratory instruments and test equipment have a long life. It is expected that they will continue to communicate with new computers. At work we use (high quality) instruments designed and built in the 90s. With a bit of effort they will speak Windows 10. Then of of course there is the question of whether the communications link is being used in it's intended application. RS232 is fine to 10M cable run and runs slow data - unless you spend on additional hardware circuits. USB was only ever intended for short runs between 'technology' items. Computer to printer, memory stick, etc. 5M is the maximum maximum cable length if you are lucky. Watch for electrical interference issues if you skimp on cable. Consumer grade USB circuits and hardware are OK at room temperature and in the dry. Sub zero or covered in dew is a very different situation. Long may the annual fashion changes on consumer equipment continue. Solving these issues is part of my work and helps to get me through the supermarket checkout. A few years ago at work we gave out USB memory sticks as a freebie. One customer said thank you, quickly followed by the question what is it? Only a couple of years later when we asked customers for backup data from old machines using floppy drive they said it could not be done as none of their office computers could read a floppy. There is a saying somewhere about keeping some of the people happy for some of the time? David.