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Peter Drew

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Peter Drew last won the day on February 24

Peter Drew had the most liked content!

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About Peter Drew

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    Sub Giant

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  • Location
    Astronomy Centre Todmorden U.K.
  1. Those "lumps" are about the size of Australia!
  2. Hello again Mike. Pleased to hear that the seeing had gone off. Why?, because when I started my session at 11 pm it was as much as I could do to see the Alpine Valley never mind the rille! I'm glad it was the seeing and not the telescope. I did have a quick look at Vega and that looked like a ball of fuzz despite being nearly overhead.
  3. Good news Mike, I'm planning to give it a go with the 8.5" refractor later tonight. Unfortunately I don't have your keen eyesight.
  4. Yes, a sad case. As a long term friend I loaned him a very nice 10" OOUK Dobsonian, normally a cure, but despite an encouraging short period of remission, the problem has resurfaced. Sigh!
  5. Just reported my observation of this event, glad someone else saw it!
  6. Did nobody else witness the spectacular outburst on the Sun today? I thought it would be all over the solar section! I turned my Ha scope on to the Sun at my first opportunity at about 12.15 and was immediately confronted by an intensely bright eruption which rapidly evolved into an enormous column full of fast moving globs of material. The whole appearance changed practically in real time. It seemed to be coming from just over the approaching limb so hopefully it signalled the arrival of an active area. The sequence lasted about 20 minutes and I think I caught it shortly after it started. Rather exciting after a long period of fairly low activity. Reprising it on GONG showed that it was indeed short lived.
  7. Somethings not right, there was a very obvious prominence on display yesterday which should have shown up well. Was this visual or via the camera? The pressured tuned Lunts do seem to have a bit of a tuning issue now and again despite the claimed superiority over the tilt tuned versions. Whatever the problem I'm sure it can be sorted even if it's a trip back to the supplier.
  8. I have no experience with making large thin mirrors but I do have a 750mm F4.1 professionally made mirror which I have built into a traditional style truss tube Dobsonian. The mirror is plate glass, flat backed, 35mm thick at the edge and with a 75mm perforation. The mirror cell is a composite of 6mm aluminium discs separated by a radial arrangement of square tubing, the edges are closed off with a peripheral band of aluminium. The mirror is supported by a 75mm central spigot with a retaining disc to stop the mirror riding forwards. There is no conventional mirror support system, interspaced between the mirror and the backplate is a disc of heavy duty bubble pack type material providing 750 points of support. The inventor of "PLOP" would have a fit, but it works. Initially there was clearance between the central spigot and the perforation in the mirror, this was to allow an edge supporting strap to take the weight of the mirror. This actually introduced astigmatism at low angles due to the mirror "potato chipping", it was cured by wrapping tape round the spigot until it was a good fit in the mirror perforation and then dispensing with the strap. Seeing conditions and mirror cooling are the main influences on its performance.
  9. Many years ago, Es Reid would avail himself of my workshop and optical testing facilities to work on some of his "special" projects. Occasionally he would do a few things for me. One such thing was refiguring the corrector plate for one of the 8" F20 Schmidt-Cassegrains I used to build. When he eventually finished it he left it set up on the collimator for me to have a look at next day when I arrived. It was indeed a fine result. I took it off the optical bench, turned round to put it elsewhere and the corrector plate flew out of the tube and smashed into countless pieces, I didn't realise it was just propped in.. I wasn't looking forward to telling him!
  10. Just noticed that they are actually 15x but the question still remains.
  11. I think they must have been adding the eyepiece field of view together as well, I can't see 30x providing a field of 7.2 degrees as stated on the body.
  12. I would love to try them out, who wouldn't!
  13. I already have a 300mm aperture apochromatic binoscope. Mine uses mirrors though, lighter, cheaper and takes up less room. At F3.5 it probably has a wider field of view than the one posted. Envious? not me.
  14. At least you knew who I was referring to.
  15. Unlikely I think but the similarity is there.
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