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Carbon Brush

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Everything posted by Carbon Brush

  1. OK, you are happy using the battery as it stands. How do you use it and what reasonable operation will it give? Given Shark, I think you can trust them to include a proper BMS (battery management system) within the module. Is the jack the charge & power out? If so, life is easier. Sometimes batteries have different charge and load connectors. You will need to take careful measurements of the 'standard' power jack. These are generally known as 'DC connectors' when you are buying. Once you depart from the 2.1mm pin connectors used on many lower cost mounts, the idea of a standard goes out of the window. I would use a caliper gauge to measure the barrel diameter and small twist drills into the socket to gauge pin diameter. That will allow you to locate a suitable connector. First of all you need to think about the DC/DC switcher convertor to derive 12V for a mount. Are you designing yourself? Relying on a £4.99 PCB type? Buying in a convertor module with known name from a reputable supplier? Your best bet is to buy in a known name. A cheapie PCB may well have high ripple. Or may have a poor design resulting in a toasted mount electronics. Take note some convertors require a minimum load for good operation - the voltage rising on low load. Whatever I used, I would add a 15V 5W or similar zener diode to limit the output in the event of a fault. A fried zener costs much less to fix than a fried mount. Having done all this, you need to think about a suitable mount fixing. Where does the battery sit? Secured to a tripod leg? Then an enclosure for the DC/DC convertor and something to fix it to the tripod. Probably a flying lead to the battery. Either a socket on the convertor box, or another flying lead. Next, what energy will it give? Lithium cells are almost always rated optimistically. The manufacturer gives a power delivery based on a certain discharge current at a certain temperature. When you deviate from these, the capacity is reduced. Check cell manufacturer data for details. The performance hit is similar between good manufacturers. They all use similar chemistry. What I'm saying is that in the cold, delivering low current, you may not obtain 59Wh. What is the efficiency of your DC/DC convertor? Assuming you buy in a named module, the manufacturer will provide data. The efficiency depends on the load for any convertor. As a general rule if you choose one with a limited input voltage range, it will be a little better. 80% efficiency is a reasonable assumption. 90% if you are lucky. Taking the above losses into account, Your 59Wh battery is probably going to deliver 40-something watt hours. Or nearly the equivalent of using a 12V 4Ah lead acid. To me it seems a lot of bother for a basic result. If doing this, I would start out with a larger capacity battery. The housing, protection and fixing issues are similar for a larger battery and a 4 cell stack avoids the DC/DC convertor. Yes if you go really big on cells the design changes. When everything is considered, the standard mains supplies and power tanks start to look reasonably priced. But as a bit of construction fun, why not. HTH, David.
  2. Danger. Do not take apart a lithium battery stack unless you know what you are doing. This is a serious warning, not one of those 'no user serviceable parts' or 'ask a grown up' warnings from the safety elves. I have taken lithium packs apart, and put them together. But I work with this sort of thing for a living so hopefully stand a better chance of survival. If you inadvertently short circuit a cell or battery pack, the fault current is often high enough to melt the connecting wires, after the insulation has caught fire. Explosions with lithium fires are not far away. Do you know for certain the battery pack has a good internal battery management system? If not, stay clear. Here are two examples..... Considering first a 'quality' pack. It was from a Dyson hand held. Showing the 'buy a new one' light. So I had to go and take a look out of interest. One cell was iffy. This pack contained an extensive management circuit, on a cell by cell basis. So there are no worries about individual cells getting over charged, or over discharged. Just connect a charger (or vacuum cleaner) and the pack looks after itself. Even if the vacuum motor stalls and pulls too much current, the pack just shuts down and restarts when the problem is cleared. With something like this, you are reasonably safe to re-purpose for astronomy. Now at the opposite end of the spectrum. A huge lithium pack from a chinese copy of a Segway. I forget now the size. But it made ebike packs look small. About the size/weight of a small car battery, which puts it about 3x the energy content. The UK buyer could not get it to charge properly and it was replaced after some argument. I offered to dismantle the pack to save the owner the hassle of safely delivering this for recycling. Around 60% of the cells were serviceable. You try recycling big faulty lithium at the local tip. If they realise what it is, they won't let you through the gate - you are carrying a bomb. There was minimal cell balancing circuitry, meaning normal charge or discharge could damage cells. No temperature monitoring - which is vital both for safety, and for setting charge voltage. Lithium cells are very touchy about overcharge, or over discharge. They are easily wrecked. Over current protection was a crude piece of flat copper to make a fuse. If in doubt. Buy a 12V Tracer pack, or one of the astro branded lithium packs. It is possible to repurpose a 12V car jump start pack. But there is significant effort in proving correct charge and you have to add your own discharge protection. HTH, David.
  3. I realise I am raising an old and well discussed thread. But found the content very interesting. Maybe my post bringing the thread to the top will provoke renewed interest? I was actually looking to see if nitrogen or argon offered any optical advantage over air. Prompted by seeing Explore Scientific eyepieces with N2 or Ar stickers that didn't seem age related. The ES site proudly proclaims argon. FLO are apparently selling new eyepieces with nitrogen. Go figure! The consensus seems here to be that as long as you put a dry and reasonably non-reactive gas in there it doesn't matter. Perhaps there is more argon available (lower price?) now we are no longer filling light bulbs? Thank you to all who contributed to the earlier posts. Hoping you all have non-fogged eyepieces whether N2 or Ar purged, or plain moist air. David.
  4. Hi and welcome to SGL. I have had a quick scan through the thread and see you are considering buying used. A good choice. However, I would avoid ebay like the plague. There is a lot of rubbish on sale and if you don't know what you are looking for, you can buy landfill. If you buy from SGL classified, you can easily see the sellers posting history, content and the like. Also, I know from experience that items sold on SGL tend to be honestly described. Just read about scratches and dents being mentioned! Having said that. Usually kit sold by seasoned astronomy enthusiasts tends to be well looked after. By that I mean the shiny metal may have tarnished with age. But lenses and mirrors haven't been cleaned using bleach. If you get my drift. Scopes sold on ebay may well have been bought on a whim, stored incorrectly for a couple of years then cosmetically polished for sale. Yes there are honest good scopes there. But only for the wary. Enjoy the journey, David.
  5. Hi. An extract from the sale rules.... Links to an item placed at other selling sites are not allowed. If the item advertised at SGL is also advertised at another site, please make this clear in your advert. Having said that. The link doesn't work. Unless you choose to give everyone your UKABS username & password Good luck with the sale. David.
  6. Which part is the hassle? Mount storage? Mount assembly? Mount setup/balance? Scope storage? Having owned and used more than one EQ5 type and 8" newt, I have thoroughly enjoyed using them. The hassles of handling and storage were easily overcome. For my first EQ5 & 8" newt, when I had limited storage I modified a wooden bookshelf. A low cost uncoated pine thing from Argos if I remember correctly. Bit of saw work, then some screws and glue and it was repurposed. The tripod with mount attached were stored vertical, with a bungy cord to stop the tripod falling out. The counterweight was on a shelf. The OTA was upright, with the finder left attached. Spare shelves held eyepieces and the like. A handle added to the OTA made carrying and mounting much easier. Carry out and setup time was minimal. Much helped by everything being left part assembled. HTH, David.
  7. I used to own a PST several years ago and could not reach focus with anything but an eyepiece. I believe the focus issues depended on when/where the scope was made, but others will know more. Certainly at the time nobody seemed to presenting good solutions. The best solution I found at the time is shown in the pic. Baader Hyperion eyepiece + Baader camera adapter + T to camera adapter + DSLR. Hopefully you will find an easier solution. Clear Skies, David.
  8. I think the important thing being missed is SGL classified rules. Here is an extract.... The SGL classified area is for personal non-commercial use only. If we suspect you are a trader or retailer, or are operating on behalf of one, your access will be withdrawn. Note that the rules extract above does not specify buying or selling, therefore covers both - in my opinion. Suppose I place a sale ad on SGL for a scope. I receive a message from 'StarryFred' or any other SGL user and he buys. Then a week later, I see 'my' scope on sale by 'The Extremely Nice 2nd Hand Scope Company'. That means there is an SGL user who is using classifieds for commercial use. In my view, he should be completely banned from the site. But that is a moderator decision. On the other side. Maybe I place a 'wanted particular scope' ad on SGL. StarryFred may respond and say he has seen one on the Extremely Nice 2nd Hand Scope Company site. That is reasonable and helpful. We have to remember that some astro businesses are run by people in the hobby, so have a foot in both camps. However, if I receive a message directly from said company that is in my view, commercial access to classifieds. On the question of selling something (outside of SGL controlled advert space) and it appearing a week later for double the price. That is just the commercial world and maybe I should have asked for more money.
  9. I haven't worked out who the dealer is. But, if he buys from SGL, as dealer, he is in clear violation of the rules. As for buying from other sites, that is up to the site owners/operators. For what it is worth (no pun intended) I think the SGL mods ought to restrict some of the buy/sell section access. Or they need to make new statements about its use. This week I have seen two instances of a new member first post being kit for sale. Anyone (without post history) can contact a member to buy kit. I thought the buy/sell section was for (established by post count) members. OK rant over.
  10. On used kit, mentioned by @7170. I think we are seeing this already. In the past weeks/months there been a few people with low post counrs offering full setups on the SGL sale section. In fact the sale item was the first post on a couple I saw this week.....
  11. I try to leave spiders, unless they are in awkward places like an OTA or other parts of the light path. A few big spiders eat most of anything else that passes by
  12. Hello and welcome to SGL. Looking forward to you posting in other parts of the forum. I was wondering if you still have any of the dob parts available to sell? Thanks, David.
  13. Hello Bill. Welcome to SGL. Hope to see you post in other parts of the forum. A few photos, mentioned by @callisto would help you.
  14. Well done spotting those with an 80mm scope. FYI Tuesday here was rain, rain and more rain. Spent the evening checking my scuba kit and looking at ark building techniques
  15. Quite honestly, months is optimistic. In my work I hear about unexpected shortages of all sorts of materials. I am being quoted 12 months on semiconductor items and have heard 2023 mentioned. To buy a scope & mount you need glass (obviously) then steel and ali for the rigid parts. Chemicals to make the rubber O rings, eyepiece cups, etc. Chemicals again to make plastic knobs and brackets. A goto mount requires plastics, motors (steel parts & copper wire), then electronics. Displays use all sorts of exotic materials. So in reality I don't expect supply issues to be resolved when the next container ships. Or even the one after. Sorry to be the bearer of doom and gloom.
  16. In round figures, a lithium battery is around 1/3 the size and weight of a similar power lead acid. Lead acid degrades with time regardless of how nice you are to it. The clock starts ticking the day it is assembled. Lithium cells tend to last for a number of charge/discharge cycles, rather than degrade on the calendar. For (intermittent between cloudy nights) astro use, lithium can be expected to easily outlive lead acid. At first sight, it appears to be a no brainer to go for lithium. However, this kit contains a lot more than just lithium cells. It contains a charger, and invertor, and more. Just how well built are these items? Do you know the manufacturer? Lithium cells are potentially very dangerous if not used and applied correctly. I know from experience that a lot of the consumer products coming out of China have fake safety and/or electrical compliance certifications. I have seen unsuitable chargers, incorrect mains leads for the application and even fake mains fuses. Yes FAKE FUSES! One of the 'best' I saw was a Segway scooter copy shipped air freight. Dodgy batteries on arrival and the seller recommending a dangerous charge technique to 'kick them to life'. There was no sign of any UN38 transport approval for the HUGE battery pack. The seller shipped then a replacement battery pack - again by air. If I was interested in this (unknown name) product, I would buy one and take it apart. After an assessment I would either use it with a smile, or take advantage of Amazon's returns policy. Ah but just a minute. This is a non returnable item! That has to tell you something. Advising someone who does not have the know how to carry out a technical assessment, I say, stick with a known brand. HTH, David.
  17. My MN78 might as well be welded to the mount. It never gets swapped out for anything else. I bought it used over 10 years ago and never regretted the decision. Built like a tank (as all Intes owners know) and optically excellent.
  18. Not at all. You are presumably talking about lead acid batteries. The amp hour (Ah) rating is specified at a given discharge current, and temperature. Often a 20 hour rate is specified. So your hypothetical 200Ah battery will run 10 amps for 20 hours to an agreed discharge level. However, if you run at a higher current, there is less Ah available. The actual loss of capacity varies with battery type. But think in term of 50% of 'on the tin capacity' if you discharge in 2 hours. Put the battery in a cold place, and it doesn't do so well. HTH, David.
  19. Sorry to hijack the thread. I was put off astronomy for a long time by using a 1" refractor on a table top tripod. Some years ago I gave a 76mm Seben reflector (don't laugh) to a large secondary school, it became their only scope. I could name and shame. I could name and shame a school science teacher who handed out homework to make a sundial - with a 12 hours face!! Yes schools do need our help. A very generous offer by Skyline. Thank you.
  20. Sorry. no clear answers to 'will it work'. A directional aerial will give you much better signal strengths. This goes for both ends of the link - if you have control over the house end. The usual (sit by the phone socket) modem/router has inbuilt aerials so you are stuck. However, if you buy a wireless router that uses an external aerial, you are in luck. Connect this to your house network, with a directional aerial, preferably outside. Alternatively you can set up a scope-to-computer network that does not involve anything else. There are lots of options on networking. It goes well beyond simple yes/no answers. You need to look at all aspects of your installation and address the weaknesses. One thing I didn't mention is radio signals from other networks. Download a wifi analyser/monitor app for a phone or tablet. Wandering around your garden you can see what other signals are competing with you for access. If you see a dozen other signals on the go, your best bet is to look for a different communications method. If there are a couple of weak signals, you don't need worry. HTH, David.
  21. My observatory (in the garden) gave marginal wifi connections until I invested in a directional aerial. A simple £20/£30 move. Another thing that helped was a decent coax cable from wifi adapter/router to aerial. The really thin coax is like a leaky hosepipe. Awful signal loss over short distance. Anything more than 10cm - forget it. Finally Keep quiet!! No not whispering. Every piece of microprocessor/computer electronics radiates unwanted radio signals. These noises compete with the wanted signal. The noise needs quietening where possible. Always used screened USB and network cables. Where practical, put your kit into metal, rather than plastic boxes. Install decoupling capacitors or small line chokes at all DC in/out points between items. Just a few suggestions. David.
  22. For distance correction - near or far - the scope focus will handle the correction. You can buy whatever eyepieces you like. If you share the scope, a second viewer needs to tweak the focus. For astigmatism correction, the scope won't handle it. Whether you need to consider this depends on your prescription. Refer to the chart posted by @globular If it is significant you need to correct for it. This gives you 3 options. 1/ Wear specs, which means choosing eyepieces with long eye relief. But anyone can use the scope without re-focussing. 2/ Wear contact lenses - my preferred solution having significant astigmatism. Anyone can use the scope without refocussing. 3/ Buy Televue dioptrix eyepieces (or similar) and the astig correction rings. £££ spent. You can't easily share the scope. HTH, David.
  23. Thanks for the heads up. There appear to be two amazon listings for wipes offered by Zeiss. First the more expensive that I have bought in the past. This link is from a previous order and the item is still available. https://www.amazon.co.uk/gp/product/B0030E4UIQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 Then todays bargain offer. https://www.amazon.co.uk/gp/product/B00IKGH2TI/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&psc=1 I can't tell the difference between them!
  24. I have one of these setups. The doublet objective gives very good views with modern eyepieces. Good luck with the sale. David.
  25. No worries. I am getting free post bumps Nichrome wire (whether bare or encapsulated) is not temperature self limiting. It will happily glow red if you give it enough current! Also if you buy it without termination, it cannot be soldered using conventional soldering methods. You need to crimp, or use high temperature terminal blocks. Both are bulky components. Self regulating tapes (and other constructions) do what is implied in the name. Albeit 60C/65C.
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