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pmlogg

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About pmlogg

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    Star Forming
  1. A really nice looking solution but my concern would be the internal diameter of 1.94m (6ft 4in). It could limit ambitions should you want a longish refractor. When racked out with an imager attached you could be pressed for space. Even my Pulsar 2.7m was an issue when I upgraded last. I use a dehumidifier linked with a device that switches it on and off depending on the humidity level. No condensation issues.
  2. Rather than buying yet another telescope have you thought of first trying a focal reducer on the C11 and/or a powermate/good quality barlow with the WO123. The Celestron .63 focal reducer would bring the focal length down to 1764 and also reduce exposure times. You do need to get the right spacing but I think it is more forgiving than most reducers for refractors. A x2 powermate would bring the WO123 to a focal length of 1440. The pair would close the gap.
  3. I don't know whether this would work with your Tak but the CAA for the FS60 has an internal 52mm thread. I don't have the telescope any more but I used a step ring 52mm to 48mm then the filter. At the time I edited from one of the Tak systems diagrams to show the set up. From memory, the wide ring provides a 52mm thread which matches up with the FS60's flatter or reducer/flattener. CAAfiltr.bmp
  4. pmlogg

    Dome Slaving

    I think that the slaving would have to be via a computer. If you are in the dome and not using a computer then aligning the dome by the buttons on the rotation drive won't be much of an effort. Celestron has a downloadable computer control programme CPWI that connects via the handset and there appear to be ASCOM drivers for that. ASCOM lists Celestron drivers and Pulsar says "The supplied Pulsar Observatories software package allows full control of the observatory from a computer, and includes an ASCOM driver for use with third party software, i.e. Maxim DL, to allow full synchronisation with your telescope." I presume they mean 'e.g.' rather than "i.e." so that you wouldn't have to have MaximDL. If so then POTH in conjunction with CPWI and the ASCOM drivers should allow slaving of Dome to Mount. POTH is part of the ASCOM platform. I don't use SharpCap but I can't see that it has a GoTo feature anyway; the guiding feature wouldn't in itself need slaving. I would imagine that you could simultaneously use SharpCap as now. Certainly worth a try once you have the dome up and running.
  5. pmlogg

    Pier help and advice

    I found a local welder who made a pier for me from steel pipe which he welded shut and mounted on a flat plate. The plate was drilled to match the bolts in the concrete pier base; the top drilled to accept an off-the-shelf mount adapter. I had it powder coated to prevent rust. Eight year later I do have a few specks of rust that I am going to just touch up with Hammerite paint.
  6. pmlogg

    Levesdome, Encoders and Shutter Motors

    Thank you for all those good points. I hadn't found the Levesdome Yahoo group and having now done so I see that there is a lot of material to look through. I've spotted on of the conversations on encoders but not yet found the spreadsheet. It looks as if most/all of the off the shelf optical encoders, seen on the internet complete with housings and mountings at quite low prices, have much higher pulse rates - as do the encoders on digital setting circles, e.g. US Digital. I have one that probably works from a drive motor that failed but it will be a higher pulse rate than 8 or 16. The Bourne ones seem very reasonable in price and the example circuits pretty easy to make. On the shutter, the motors in the setup I was minded to copy are inline gearmotors whereas most (all?) wiper motors look as if they are right angle with relatively high rpm. A different mounting I suppose is just something to work out and I have now seen some postings on the use of Pulse Width Modulation Control to reduce rpm as required. The electronics in all this is where I am very weak. The same for programming - despite having done some many, many moons ago at school. I do have one contact who might be able to help with a bit of machining for the motor coupling - or at least point me in the right direction. When in the past I contacted local machining companies the cost made it cheaper to buy ready-made instead. I've read a couple of interesting posts on home made acorn drives and trackway although those are far and away the cheapest bits to buy from Exploradome or Opt. I'll get on with reading at the Levesdome group and have a think about mountings for wiper motors.
  7. The mechanicals for rotating my Pulsar dome are finally working OK - not really DIY but a 2nd hand system from an old model 2.2m dome adapted to fit an old 2.7m version. The aim, as mentioned in other posts is to move on to automation and I've begun gathering the parts but haven't got too far yet. In parallel I'm looking towards motorising the shutter. My first question is about encoders for the rotation system. I have used these before as part of Digital Setting Circles but not starting from scratch. I think that I read about a limitation with Levesdome on how many pulses/tics it can cope with so I don't want to try to use an encoder that it wouldn't work with. Could anyone advise me as to what the limit might be? My second question is about the gearmotor for the upper shutter; my dome having the old two-part one. My thought is to copy the method used by another SGL member. For the upper shutter he uses parts from Explora-dome rotation system. He has fitted a gearmotor with 8 inch diameter Acorn type sprocket at the top of the dome which interfaces with a strip of the Explora-dome track mounted centrally along the length of the upper shutter to raise and lower it. Apparently that is working very well for him. I've asked Explora-dome for a quote for the bits but have a horrible feeling I won't like the price of the gearmotors. So finding a cheaper, but still good quality motor might be necessary. The Explora-dome gearmotor specifications appears to be: 25rpm, continuous torque 79 lb-in, 443 in-lbs peak torque, IP54. I think the Explora-dome is of heavier construction than the Pulsar so perhaps my shutter would need less torque to move. A complication with using a different motor is that the one that mates with the sprocket has a 12mm diameter shaft with a protruding 4mmx4mm key. The motors I've been finding online either have flats or internal keyways and the shaft adapters all seem to be too big. Suggestions regarding the gearmotor, including required torque and adaption of the shaft, would be much appreciated.
  8. I would have to do the opposite - dis-connect when using the battery as it will be dome mounted. But that is the sort of mains charger that I meant as an alternative to using any solar panel.
  9. Thanks for that link. I had looked at similar (same factory?) ones but eventually found a description clarifying that the connection on the back is not waterproof, although the panel it self is claimed to be. So I didn't have much confidence in that. Also I was uncertain how easy it would be to mount that type. The one I listed is described as IP67 - the only panel I could find with an IP rating. The reviews on Amazon seem good. The draw from the vintage Pulsar rotation system is intermittent as the dome indexes periodically, not continuously. It of course draws more power during slews. I don't have a feel for how many watts might be used during a session as there are no specifications for the rotation kit and Pulsar seems not to have any corporate memory. I assume that even an extensive night of imaging would probably use less than if dotting about observing multiple objects. Pulsar did intend for just a single 1.5W panel to be enough to re-charge during the day and trickle maintain but how users found that in practice I don't know. The standard battery was a 7.2Ah. The one that came with the used system was a bit old and as access is very difficult when fitted to the dome I decided to buy a fresh 9Ah and fit it first. That's the stage I'm at now.
  10. There is a US company that specialises in making astronomy adapters. Here's the link: https://www.preciseparts.com/ppmain//index.html It allows you to build to order on line and gives a price. And Astroparts in the UK: https://www.astroparts.co.uk/index.htm
  11. As the BBC promised, some late sun. Voltage bouncing about but 18-21V and 20mA. So, more than an order of magnitude better but still under 0.4W rather than the theoretical 3.0W. Definitely not enough to even maintain the battery let alone do any re-charging after a night's imaging. The search for an alternative has started. I noted some properly waterproof models - NOCO BLSOLAR5 5W and BLSOLAR2 2.5W but they cost more than a mains trickle charger and would need re-jigging of the mounting on the dome. I'm struggling to think of reasons not to use the available (and reliable) mains power rather than a panel, other than a reluctance to leave a charger on all the time.
  12. Looks like we are due some sunshine Friday and Saturday so I'll check again then. But in the real astronomy season the number of hours of good sunshine each day can be pretty limited so not a dependable supply - mind you, the number of good nights when the dome is used can be quite few too!
  13. Well, not sure if I can recommend them. Today I measured voltage then current across the terminals. One gave a stable voltage of 9.3V, the other averaging that, but jumping around. Not sure if I am reading the scale wrong but set at max. 300 DCmA I only got a reading of 1.4 on each and 2.2 when connected in parallel. Wouldn't that be just 20mW? It was quite overcast, after rain but nowhere near dark. Peter
  14. A while back I did put my multimeter on the panel outputs and did get a voltage but I didn't check the current, just the volts. I will test V and A tomorrow if it's dry when I get home from work. The LEDs are blinkers. Thanks Peter
  15. Thank you for all those replies. One of the panels came with the dome, accidentally included as I hadn't bought the motor drive -it was Pulsar's demonstrator. The other panel came with the 2nd hand system I bought - so both have lived outside and have been again for a few months, although not connected to a load. The LEDs are blinking so the panels aren't dead but what amps they are producing I'm not sure. As the dome was already drilled and fitted with grommets for the cables, and I already had them, I thought I might as well give them a try. I just had to make a bit of bracket to hold the pair, using the existing bolt holes. I do have mains power in the dome though so I could use a normal charger instead. If they don't perform I'll just disconnect and do that - remembering to unplug before rotating! I think I will try without a controller first - given the panels are so low powered, and have the diodes - really to avoid having to find extra space for the controllers and a means to secure them. I take the point about the LEDs but the panels are sealed so I don't want to open them up to get at the LEDs. I'll report back when everything else is fitted and I've had a chance to let them do their thing.
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