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Rusted last won the day on March 5

Rusted had the most liked content!

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3,208 Excellent


About Rusted

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    Brown Dwarf

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    ATM, imaging, solar, Solar system, photography, blogging, cycling, walking, birdwatching, digiscoping, audio, DIY, clocks.
  • Location
    Exiled to sunniest and darkest, rural Denmark!
  1. Enjoy! This is [usually] only the beginning!
  2. I have only one dome shutter open but the telescopes ar still being shaken about. 53F and it feels freezing! There's a gorgeous multiple spot with radiating detail but my images are very poor. The AR is easily seen in white light in my old 90mm Vixen + Lunt wedge. I'd better close up before the dome takes off!
  3. Thanks. I should at least try to pack out the etalon sides to better match its cell. Teflon/PTFE plumbing tape makes most sense. It is very thin and easily adjusted for thickness. Electrical tape was far too thick for this job. One small tab and the etalon no longer rattled but was off centre.
  4. I've just been over to the observatory [in the rain and the wind] to dismantle my PST etalon for science. It seems I have been fooling myself about tilting the inner, tuning ring. The undersized implements, I have used to tune, have fooled me into believing I was tilting. The etalon glass sandwich is held firmly in its cell, albeit with some freedom. Not even enough for electrical tape tape to close the gap. I would have needed PTFE plumbing tape. The etalon element is under pressure from a PTFE ring lying very close to the etalon's rim. So it is difficult to see how one can externally apply any useful tilting. The pressure is perpendicular, applied at the rim and therefore [probably] self-aligning. Regarding the sponge ring. This sits squarely in the bottom of the etalon cell. If it is certainly being compressed, over a long period of time, but so what? Assuming the sponge took on a memory of being compressed then why would it matter? One merely adds a slight extra turn on the tuning band to take up any "memory" displacement. There is no change in the pressure required because the extra space is simply taken up manually. The centre tuning point might be displaced, but again, is unimportant. The acid test requires a good dollop of sunshine. I shall find a rod which fits snugly in an inner ring screw hole. Then attempt to tilt the etalon's inner, tuning ring while the image is centred on the well-focused sun.
  5. Thanks Peter. The truth is out there. It is a matter finding it by means of simple search terms. Which even Google can understand.. without trying to sell me solar panels..
  6. An update: Mark Townley's piece on the PST etalon: I'd forgotten about his blog as an excellent solar resource. Brierley Hill Solar: Equipment Mark suffered from a floppy etalon. Just as I do. I use the freedom to manually tune and re-collimate my etalon but it is not at all stable. Mark used an acrylic ring to restrain the base of his etalon. Plus some PTFE plumber's tape on the threads. I have a lathe and measuring equipment so I'll try turning a base, restraining ring first. Clear polycarbonate, or even black HDPE, would probably suit this exercise. I may even have a suitable O-ring.
  7. Thanks. Give up? Never. I am fascinated by your suggestions for improvement. What are you suggesting precisely? That I shim the outside of the etalon glass block to stop it rocking sideways in its cell? BTW: I use the rod to deliberately tilt the etalon to find the most even illumination as I simultaneously rotate the etalon inner band. The rod is not remotely a tight fit in the screw holes and I often use anything to hand which will fit easily in one of the numerous, tuning, screw holes. I presume, from what you say, that I am manually centring the sweet spot by tilting? That makes sense. There is also the matter of the freedom of movement of the etalon sandwich itself. The glass must be quite loose in its cell if it allows such tilting. Presumably due to years of heavy, foam ring compression causing it to flatten. It seems unlikely that it would revert to its original state and dimensions, in a relatively short time, simply through unloading the pressure.
  8. Thanks. My etalon is already, half exposed. i.e. Without its usual metal or rubber band. I adjust the etalon tuning and tilt frequently with a rod in one of the usual screw holes. But I have always suffered the same off axis "illumination." There is one setting where the entire field darkens and becomes more even. That is my preferred setting but it is not very stable. I have previously removed the etalon element, examined it and its sponge support ring. Sadly I was none the wiser over what could actually be done to improve matters. There is no separate packing piece. Which is mentioned occasionally in solar circles. Just a plain, sponge rubber ring. Any specific advice would be very welcome.
  9. Brief glimpse of the sun, moon and Mars today. Emphasis on "brief!" Ya wanna see today's harvest after several days of drought?
  10. A brief glimpse of the sun fooled me into setting up. One quick "snap" and the overcast returned. Not so much a work of art as a humble record of the event. The spot had left quite a trail of destruction in its wake!
  11. Blowing a gale here with cloud until it was too late to matter.
  12. The new dangerous sport for 2020? Extreme observing spot landscaping under duress. Mine likes my two storey, 10' green dome on top of a 15' tall octagon [with veranda]. So there!
  13. I'll see your damp Cheshire and raise you Wales and Cumbria.
  14. All good points but I find excessive eye relief a nuisance. Preferring the gentle, head locating effect, of the twin eye cups, for relaxed, extended comfort. I bought pair of 40mm Plossls for achieving lower powers with GPCs and have never used them again after the first trial. Oddly enough I found my head could not remain steady at the precise position required without any physical clues. 26mm followed by 32mm are my usual "weapons of choice."
  15. I gave up the idea of a Pulsar dome after reading about the condensation problem. I also passed up a secondhand 2.7m GRP dome at pocket money price. Hopefully this absence of condensation will continue for you. Keep an eye out for white mould on the painted, inside surfaces. My plywood dome is deliberately well ventilated at the base ring, bi-parting shutters and is wide open below floor level. I even spaced the floorboards to let it breathe. The insides of the matt black water based paint on plywood dome and walls have all been covered in white mould since the first cool weather from first being built. It hasn't got any worse and is more cosmetic than a structural problem. The worry is that mould can cause allergies and severe bronchial problems.
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