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About Dave1

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    Proto Star

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    Astronomy, Motorcycles, Theology, Philosophy , Music.
  • Location
    Dorset, UK
  1. I think where the confusion comes is the mix up between angular airy disc size and linear airy disc size. Like in the link John posted. If you compare the linear airy disc size of F7.5 to a telescope of F15. The F15 linear airy disc size will be double the size airy disc. That's according to Sedgwick. But don't ask me to do the math! David
  2. I've read a few different websites on this subject. That has to be one of the best well written easy to understand explanations I've ever read. Great share John, thumbs up from me. From my understanding. Comparing like for like aperture, at the same magnification the slower telescope has a bigger airy disc. Which is definitely an advantage for planetary viewing. David
  3. Still for sale, if anyone is interested?
  4. If you click on this link https://stargazerslounge.com/topic/341473-takahashi-starbase-80/?do=findComment&comment=3832402 you can see all the tests that have been done by Wellenform, which is who APM Markus Ludes in Germany use to test there telescopes. And Wolfi at Wellenform really knows his optics. This test was done on behalf of the French astronomers. It has a Foucault test, Diffraction test, Wellenform report technical conclusion, Strehl ratio achieved in specific light rays F, E, D, C. Going off of the tests the French had done by Wellenform, these are not cheap entry level optics, they are high quality optics made in the best time honoured Japanese tradition. David
  5. It means to draw/sketch to paper what you can see at the eyepiece. Can be just a normal HB pencil, charcoal pencils, or colour pencils. Easier to start of basic though. You tend to see more details on the disc as you sketch. Sketch doesn't have to be fancy. The below is an example when the seeing was very good, even though Jupiter was below 30 degrees. Note north and south are up the written in the wrong places. That was drawn using a 80mm F15 telescope. In this photo of the sketch you can see north temperate belt, north equatorial belt, festoons coming off the north temperate belt, dark concentrations in the north temperate belt, south equatorial belt, with a dark belt within the south equatorial belt, south temperate belt, and if you look closely two white belts toward the south pole ( remember north and south are marked wrong ) David
  6. Yes I'd like to buy this telescope, but not at the moment. Bank account needs to recover. I really like the Scopetech 80mm F15. The Foucault test, strehl ratios for different wave lengths, and spot diagrams are very good to excellent. Agreed a 4" F15 needs a serious mount, and any bigger must definately have a big mount. I might have a John Owen 6" F12 doublet coming my way. Thankfully I have the mount for it ! David
  7. A good 3-4" telescope can show a good amount of detail, if you practice and get your eye in. The more practice you get, the better. The more details you will see. One way to increase your observation skills is to sketch at the eyepiece. David
  8. Well some more eyepieces arrived today, to add to my collection of 0.965" eyepieces. From left to right. Takahashi Ortho MC 7mm, Pentax Ortho 6mm, Takahashi Ortho MC 5mm. Have to say they all look impressive build quality. And I can't wait to test them on Jupiter along side my CZJ O-10 which I haven't used yet. David
  9. So guys, I've done some more work on my Fullerscopes mount today. I've put the worm gears and worm drive on. See the attached photo. In the photo what you can see is a worm gear, worm drive, combination of bearings, springs, and a screw device to vary the pressure asserted on the spring. Quite a clever bit of engineering, as it allows the worm gear to turn the DEC axis with out the worm gear being directly attached to the Dec shaft. So if for some unforeseen reason the telescope got caught on something, or big amount of force got put onto that axis. The worm gear would just spin around the Dec axis, which would prevent damaging the worm gear teeth, and probably the telescope and any other associated part. There was a somewhat similar set up on the RA axis but minus the screw device to vary the pressure applied in the system, a minus a bearing. The reason for the screw device being omitted, is simple the RA axis isn't long enough to accommodate one. Which is a shame. Because of the different set up, it doesn't really work. So I've had to bolt the RA worm gear directly to the RA shaft. So no fail safe here. Which is a shame as the RA shaft will need far more energy and power to turn as its moving a lot more weight. The solution would be to get a longer shaft, and copy the set up on the DEC axis. I will probably do this one day.
  10. My number one interest in astronomy is the planets, my kit is all orientated toward planetary observation. When it comes to viewing planets, it is a skill that needs practicing. The details may not jump out at you now, but if you keep preserving. You will develop the skill. There is a saying " many look, not many observe ". Like any skill it needs to be developed. Only use the maximum magnification that the seeing conditions will support, going above that magnification will be pointless and offer you no more detail. Yes a 2x barlow is a good way to go. Although I prefer dedicated eyepieces to Barlow's, experiment, until you get to know what you like. I've slowly built my collection up over the years. The planets are poorly placed at the moment, they are pretty low in the sky, when they get above 30 degrees, things will improve. The attached picture, is what is possible with an 80mm F15 refractor on Jupiter. Although I made a mistake with the North and South orientation. Best Regards David
  11. So guys, An update, the mount arrived today, see here https://stargazerslounge.com/topic/305552-what-did-the-postman-bring/?do=findComment&comment=3859130 I haven't had much of a chance to measure yet. But I have a rough idea how I will mount the stepper motors. There is also a slight difference from the description. Even though I was told the worm gear and drives were 360:1. They are in fact 287:1. Which means the resolution achieved with 3:1 reduction is slightly less. A way around that and regaining that resolution is to goto a 4:1 reduction. But I'm not sure if that might be a bit slow. Maybe I should by both. Here is an idea of off the shelf pully systems from China, https://www.aliexpress.com/item/32855945814.html?spm=a2g0o.detail.1000023.42.6895323fPx97QP David
  12. My 4" F15 Skylight. With the idea of future proofing myself in case I intend to go upto 6" F15 or 16 " Newtonian. David
  13. Here it is, my new to me Fullerscope MKIV mount. looking forward to getting this working!
  14. Beacon Hill, do mirror blank kits, for very reasonable prices of between £29-£39 with everything you need. To quote them " Complete Mirror Kits (NB Glass disks extra) Containing sufficient quantity of the following, 80, 120, 220, 320 Aluminium Oxide. 225, 175, 125, 95 Optical powder, Cerium Oxide and Optical Quality Pitch For 6" mirror ........ £27.00 For 8" mirror ........ £29.00 For 10" mirror ...... £39.00 " The also offer bigger and higher quality glass mirror blanks for a bit more money. Best phone them with what specification you want, they will sort you out. They only do business over the phone (0)1507 363 381. Here is there website http://beaconhilltelescopes.org.uk/
  15. Yes it is, these don't really come up for sale very often.
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