Carbon Brush

Ref John. The propellors were probably a Be/Cu alloy. No hazard until ground up and inhaled! Be/Cu alloy is often used in electronics to make springs with excellent electrical conductivity. For James Webb. I think the $$$$ per Kg of payload launch cost would justify thinking of materials other than glass. The effort of lifting a big dob into the garden is a bit different.😁 David.

A few years back I found myself having to dispose of a hundred or so computer CDs. I idly wondered about making cheap simple brackets and fastening the discs to my gutters, fence tops and other places. Send the light back to the source. Basically if it is a neighbours light, blast everything at their door - at eye level! My argument is that I am not generating light trespass or pollution. I am simply returning a neighbours waste. A bit like giving him the tree clippings back. David.

If your prescription is only a focal length correction, without astigmatism, then you don't need bother. You will just have the focus tube in a different place to when you are using glasses. Observing without glasses means one less piece of (sometimes poor) glass in the way. You can use eyepieces with short eye relief. That is your eyeball has to be close to the eyepiece. For a given quality, these can cost less than long eye relief eyepieces. HTH, David.

Slightly away from topic. In the UK contact lenses can only be prescribed by an optician are subject to on going checks. I have always (15 years) found the prescribing opticians to be very good at explaining risks, and warning signs to prevent serious problems. HTH David

Good link from Geoff Barnes. Somewhere on SGL there is a very good cleaning video by member Steppenwolf. Essentially the same techniques (from memory) but with the benefit of moving pictures to follow. I have used the washing up bowl, mild detergent followed by deionised water method with success and improtantly, no discernible damage. The worst mirror I cleaned had been left facing up and uncovered in a shed for a year or two. It came up really well. To finish rinsing, I have used a mix of deionised water and IPA (isopropanol or isopropyl alcohol). This has the benefit of reducing surface tesnion, to discourage droplet formation, and making a lower than water boiling point mixture that will easily evporate using a a hair dryer. Just take care. Don't rush and get all your cleaning stuff to hand before starting. If there is a bit of stubborn muck, leave it. You won't notice it in the views. HTH. David.

I'm no expert on this but here is my limited understanding.... At any magnification, astigmatism is an issue. But, as exit pupil size reduces, the problems caused by astigmatism reduce. Unfortunately a tiny exit pupil introduces other problems. If high magnification planetary views are really what you want, then go for a longer focal length scope of a similar diameter. If you are happy with a newt, that will give you most light gather & magnification for your ££ spent. Having said that, CA in a long FL scope is less of an issue. This will give you higher magnification and allow you to consider the need for other eyepieces. Another thought is dealing with astigmatism either by a contact lens, or a TV dioprix, or simlar approach. The dioptrix will only fit certain eyepieces so can be a big cost of ownership! Not exactly the answer you asked for. But a different approach. David.

Hello Annie. Where to start? You have some good equipment there. 2nd hand prices tend to be up to 2/3 of new price, assuming things are in good working order. It would make sense to bundle certain items for sale. An obvious example being the Canon camera and the accessories. I hope that a member near to Chesterfield will come along and offer to help you to sort things out. That would raise maximum funds for you. Alternatively, was your father in law a member of a local astronomy society? Someone from there who knew him might be a good idea. A person who deals in used astronomy kit may come along and make an offer for the lot. This is the minimum effort/hassle route. But not necessarily raising much money. I'm sure an SGL member local to you will be along soon. Hope this helps, David.

Sorry I can't find the source right now. But I remember reading that almost 50% of house break ins were during the day. In other words daylight, security lights or dark make little difference!

I considered (a long time back) an eyepiece/adapter that deals with astigmatism. But never bought one. To me having to keep the EP aligned to your eye may be a bit of bother when the scope moves around the sky. Then what if (like me) you have different astig in left/right eyes and you swap eyes while viewing? The solution I opted for was contact lenses. They sort the differing astigmatism in both eyes and can be used away from the scope. They are for distance & astig correction, which means cheap reading specs for small fiddly things around the scope. Following the thread with interest. David.

A once only spend of £100 on grass mats or........ £20 on shoe polish. £20 on grass seed. £20 on ear defenders - required PPE after treading mud into the house. £20 on carpet cleaning. Same again a week later.... A word of encouragement. I have had no regrets about the spend on the garden and workshop matting. Fit, problems solved, then forget. David.

Amazing image. Two thoughts come to my mind. First, a mag 14 object is going to defy discovery by accident. The search by Clyde Tombaugh was looking in a (mathematically) predicted location. Second. Less than a hundred years after Pluto's discovery, after less than half an orbit around the sun, things have moved on so far that an amateur astronomer can see the object.

Hi Jake and welcome to SGL. The best astronomy forum in the world. M31 can be difficult. I remember spending ages trying to find it without success. Then one night it literally jumped out. After that I could easily point binos straight there and, depending on the sky, sometimes get the visual 'smudge'. Keep trying and the more you look, the more you will see. HTH David.

If you post a photo of the mains inlet, ideally with a rule alongside, I may be able to give a pointer. David.

There is no solution to unexpected clouds. But having viewing options as advised in earlier replies is a big help. Also experience counts. A bit like going camping or on holiday. After a few outings, you get used to what you need to take and can have everything ready to go in a short time. The same aplies to the on site setup time. After a few outings, you get to be able to assemble the kit with your eyes closed - or a on a dark site! Hope the replies help to keep you enthusiastic. David.

I have used the grassmats type of product with success at home and at work. Some are rubbery. Some are a semi rigid plastic, rather like wire mesh in appearance. Some are rigid and interlock like lego bricks. All of them allow drainage, and allow the grass to grow and give you a harder surface to walk on. In some cases it has been a heavy duty mesh to prevent vehicle damage. In another a light duty mesh to bind soil over a rubber pond liner, around the pond edge. The rubber mats are in use at home to provide grip on slippery concrete, and at work to provide a floor in a messy workshop. A set of rigid tiles make a path to my observatory. At first they just sat on the surface. They are gradually sinking as the rain softens the soil. After less than a year they are virtually invisible. The rubbery or semi rigid are best for uneven ground. The rigid types are great on level ground. Hope this helps, David.

Before rushing out to buy the bargain, I would have a think. In all probability the weak £ has limited sales into the UK. Coming at a time of little solar activity. If Lunt have a huge number of tilted tuned 60s on the shelf, does this mean users much prefer a pressure tuned version? Are you happy with amount of light passing through a 400 or 600 version of filter? I'm not saying avoid these models. But it would be worth asking around other users to obtain their views. For what its worth. I have a Lunt 60 with pressure tune and bf1200. The choice was in effect made for me because this package came up hardly used and very local. At the time, other scopes with different configuration were a long way to travel. So I spent on the scope rather than petrol. The combination I have works well. But not having tried other variants I am not in a position to give an informed opinion on any reduction in usability or performance from the other options. Hope this helps, David.

Hi Dan. Eyepeices are as much about what you are comfortable using, as they are about performance. I use Hyperion eyepieces. To me they are very useful. I like the long eye relief if using specs. If you want to change the eyepeice FL, you can add a tuning ring or remove the bottom section. The 68deg FOV is a good wide viewing experience. Though that is to some extent a personal choice. The downside is an F5 scope is at the bottom end of the tolerance for a Hyperion. A bit soft at the edges as Robin pointed out. They are also 'jam jar' size and weight, which can be an issue with certain small scope/mount combination. But on balance I think they are good. My Hyperions aren't going anywhere anytime soon. I like them. Hope this helps, David.

Take note of the 'specmanship' used by the seller, and read the small print. In other words he is misleading you about the battery power storage. You have a battery comprising 7 cells in series. Each cell is about 3.7V and 3.2Ah. To obtain 12V, he is most likely using the series connected cells into a switched mode power supply. Assuming 80% conversion efficiency, then you have something that looks like a 12V 9Ah battery pack. But how it will handle inrush on a tablet/laptop supply, or a mount slewing is a guess. If it was me buying, I would buy something from a reputable manufacturer. Tracer for example. Poorly designed or incorrectly assembled lithium power packs are a big fire risk. If the switched mode supply plays up, you may end up with expensive mount or laptop damage. Hope this helps, David.

Yes camera tripod thread. 1/4" UNC. A good source is ebay. Nice stainless bolts for Harley bikes etc. Available in small quantity and various lengths / head types. David.

A suggestion before spending on an extension tube. In daylight, point your scope to the horizon. Offer the DSLR camera + barlow up to the focus tube and move the camera by hand. Use live view or a separate screen. If you see that to obtain focus the camera is in mid air, you have demonstrated that you need an extension tube and you have an idea of the length. If you only need a millimetre or two. Is there enough space to pull the main mirror back a little? I have had the opposite problem (on different scopes) and had to lift the main mirror or swap to a low profile focusser. Hope this helps, David.

Thinking here about thermal conductivity of the various materials in most Maks. A metal tube, being a good thermal conductor, will transfer heat to the outside quickly. This means the air in the tube will cool quickly without the tube being left open. Thick glass will hold a lot of heat. It has lower specific heat than aluminium. But is an awful conductor and can be in thick slabs. Well thick compared to the metal tube. The front glass has one face to the outside to help cooling. But the mirror can only lose heat to the air in the tube. I have not done actual trials, but my gut feeling is that a plastic (poor heat conductor) front lens cap will slow cooling. If you can swap for a thin metal cap, that will help. Could this be why, for example, the ETX90 (a budget scope) had an aluminium front cap? In the numbers these were made, surely a mould plastic cap cost a lot less. Just a thought, or two. David.

Any society or group involves a long journey for me. They are all an hour or more driving each way. So any I attend are on the basis there is something special going on and I pay for the event. I was a member of a local society a long time ago. But they decided they didn't want me. Being a bit busy at membership renewal, I forgot about my subs. They did not send a reminder either. I was at the end of a long and unstable chain trying to sell my house. Looking for another to buy, and helping someone with theirs for sale. I thought that under the circumstances sending in my cheque 2 months late with an apology was not unreasonable. But no. They sent the cheque back. Limited seating the lecture room so they had put a cap on membership and it was full. I was told I was on the waiting list and they would contact me when there was a vacancy. That was in 2007 and I have yet to hear from them. Then again. Did I want to join a society that had elected a chairman who did not even own a telescope. They do a lot of public evenings with a significant admission charge. Apart from that, it appears to be a secretive group. Not exactly 'you can't join unless you are already a member' but not far off! The exact opposite was my experience with East Midlands Stargazers. A fantastic friendly crowd who get their scopes out at a dark site. Can't say enough good words about them. But at 70 miles round trip when I have reasonable skies at home.... So if you have a local society who are friendly and welcoming, do join in. David.

At home I have enjoyed pointing out the nebula (unaided) to visitors from areas with more polluted skies. Just going into that part of Orion with binos or a low power eyepiece gets you lost among the stars. I always look forward to Orion showing over trees as winter approaches.

I think for anyone thinking about meteor or comet impacts, this report about the Tunguska event is interesting. https://en.wikipedia.org/wiki/Tunguska_event Long distance 'instant' communication by telegraph was established - in a few places. Individual institutions and researchers in Europe and further afield noted changes to the sky, etc. But presumably did not receive reports from those local to the event. Those 'local' to the event. By that I mean Russian scientists, who did not investigate for years. OK they may have been sidetracked by WW1 and a revolution. Had the impact been over somewhere densely populated, like Europe, the casualty count would have been huge. Had this been over open water, there would have been extensive coastal flooding - and casualties. I'm sure the earth has suffered impacts that nowadays would flatten a city, or small country, many times in human history. But it is only recently, and some parts of the world that they are documented. In my lifetime, comets have been binocular or telescope objects. There have been daylight visible comets in the past few hundred years. So just because I have seen nothing more than dim fuzzy blobs, or the odd metoer streak, it does not mean there is nothing bigger out there. Am I right in thinking Barringer crater is only about 50K years old? An instant in evolutionary timescales. Now here is the really worrying part. What if Tunguska had happened at the height of the cold war? 1950s or 60s. Would this have triggered a man made mass extinction from those with fingers on the missile buttons?

For what it is worth, here are my thoughts. It costs a lot of money for solar panels, wind turbines, charge controllers and batteries. The real world implementation of these is not as well established as the salesmen with their glossy flyers would have you believe. Batteries have a limited life (particulalry lead acid) and high capital outlay (particularly lithium). A mains cable is well established technology, not expensive and can outlive the owner. The only sound arguments for a solar/wind/battery powered observatory are: 1/ A very low power requirement. In other words a simple goto mount. No dew heaters or anything else. 2/ The observatory is hundreds of metres away from a mains supply, making the cable run expensive. 3/ Being prepared for extensive mains power cuts that will remove light pollution at a stroke. Just my thoughts... David.