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Alan64

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Everything posted by Alan64

  1. Mirrored telescopes, even advanced ones like the modified-Cassegrains, are not what I think of for advanced solar-observations. Still, I'm thinking that you're wanting the ability to use the telescopes you have on hand, and perhaps for their ease in reaching the higher magnifications. The prices are utterly out of reach for myself, else I would have a specialised refractor, like one from the Meade Coronado series.
  2. I use Super Lube for all of my mounts. It's not particularly light, nor heavy. It's PTFE, or Teflon, based, and what might be better than that. The old grease must be removed completely, utterly. I use charcoal-lighter fluid for that, the kind for grilling food outdoors, which works a charm.
  3. In that..."neither of us have any experience in setting up or calibrating viewing equipment"...I would think that a refractor, an achromat, would suit you best. Unfortunately, in so far as compactness combined with performance and versatility, the Sky-Watcher "Startravel" offerings are too short, and those of the "Evostar" line are a bit too long. Meade offers this 90mm f/6.7 achromat on an AZ-3 alt-azimuth mount... https://www.picstop.co.uk/meade/meade-infinity-90mm-altazimuth-refractor-telescope.html?wgu=217_109047_1574904376426_d25af2eaa8&wgexpiry=1577496376&source=webgains&siteid=109047 Here are over 600 user-reviews of the Meade "Infinity" line in general... https://www.amazon.com/Meade-Instruments-Infinity-Refractor-Telescope/dp/B00LY8JWB0 Refractors require virtually no maintenance, and are ready to use once taken outdoors.
  4. It appears that I will be able to retain the aperture-stop after all. The dust-plug for the dust-cap... The plug is not of hard-plastic as the cap, but rubbery, yet stiff in its own right. Aluminum bonds to rubber quite well, with epoxy...
  5. The cap now fits to where I want it. It's neither snug nor loose. Part of the flange will be flocked, and to serve as cushioning as the cap is removed and replaced... A section of the flange was cut out to accommodate the secondary-stalk and the thicker aluminum used to bolster it. The center-plug, for the 60mm aperture-stop, cannot be used, as it's too thick and will not fit due to the secondary-hub's adjustment screws sticking out too far; and no, I am not going to revert back to the set-screws, absolutely not. Instead, I will fill the hole with aluminum sheet backed with black-plastic sheet or other, and add a knob. Oh dear, if I do that, I won't be able to use, per the diameter of the secondary-mirror, the 60mm f/1 or f/2 aperture... It looks like I'll just have to do without that grossly-obstructed aperture; and a dim, 60mm one at that.
  6. Presently, I'm working on the dust-cap for the telescope's front opening... It snap-fitted originally, but with the addition of the aluminum veneer to the inside rim of the cowling, I'm having to reduce the diameter of the cap's flange.
  7. I'll need to matte-blacken the heads of the screws next. The acorn-nuts lend a bit of panache and style, eh?
  8. Nonetheless you did forecast the solution for the cowling. Had you not made merry mention of that, I probably would've gone ahead and used those jack-nuts and lock-washers on the inside. Thank you again. I now have to remove 4mm from the ends of each screw. I may grind down the heads a bit, for an even lower profile, but only as long as I'm able to retain enough depth for a hex-key to grab still.
  9. Yes, but then I'd have to notch out that side for the finders' alignment-tabs... ...which I can do, easily, but then the thumbscrew would be forward, and would not batten down at the stalks entry-point, if that matters really, I do not know. In any event, for me, it's more of an aesthetic concern rather than one of practicality. I have relatively small hands, so it's of no real consequence. I do have this finder-base... ...but that one is for my Maksutov. It's not notched, however I just may notch it out before its installation.
  10. I had gone to all of this trouble... ...and for naught, as the combined jack-nuts and lock-washers are just a bit too thick, and would intrude into the incoming light-path towards the primary-mirror. I then thought I might get by with the original screws... ...but two of the plastic, threaded holes of the cowling; one is totally stripped-out, and the other nigh to that, so there went that idea. Good thing too, as I really didn't want to use them after all. I went out earlier today to my local hardware, and got just the thing, or things rather... The black-oiled screws, with their shallow heads, will be inserted from the inside of the tube, and with the stainless-steel hardware on the outside. The lock-washers will be sandwiched in between the acorn-nuts and the flat-washers. Oh Julian; yoo hoo! You were prophetic, sir. A prophet in your own right... Even though I did not utilise your method for the finder-base, I am to employ it for securing the cowling. Thank you for mentioning it, as it undoubtedly influenced the outcome.
  11. The telescopes attached onto these Dobson-type alt-azimuth mounts are Newtonians. Newtonians afford the largest aperture per pound spent. But there's a catch: Newtonians require routine collimation, more so than any other design of telescope. The procedure can be difficult at first, but then becomes easier; learning by doing, keeping at it. The shorter the Newtonian, the more difficult it is to collimate; the more exacting, the more precise the collimation needs to be, and for sharp and pleasing images, particularly at the higher powers. Note the focal-ratio when selecting a Newtonian or Newtonian-Dobson, and generally from f/4 to f/8. An f/4 is more difficult than an f/8. An f/5 is the shortest that I recommend and suggest. An f/4 Newtonian is configured primarily for photographic applications, although they are used visually, with eyepieces, as well. The longer the Newtonian, the easier it is to reach the higher powers, and where "Wow!" and "Look at that!" exist. But an object zips out of the field-of-view of the eyepiece faster at the higher powers; with a manual mount, without motorised tracking. The shorter the Newtonian, the higher the degree of coma is made manifest. At the edges of the views round stars become streaks, lines, particularly at the lower powers. No doubt the shorter Newtonians are most attractive, as they are more compact, ergonomic; easier to carry, handle and stow away. A 130mm or 150mm f/5 Newtonian is a compromise, and an acceptable one. You get a shorter tube, being more difficult to collimate, and more difficult in reaching the higher powers, but 2x and 3x barlows are available to ramp up the magnification. Never consider any Newtonian shorter than f/5, for visual use. After all, telescopes are all about seeing faraway objects up close. Else, use your eyes or a pair of binoculars. At a 1200mm focal-length, a 150mm f/8 Newtonian-Dobson is a bit long. My 150mm f/5 Newtonian, with a focal-length of 750mm, is a bit short... ...with the 650mm focal-length of a 130mm f/5, even shorter. Yet both, again, are an acceptable compromise between ergonomics and optical performance. A 150mm f/10, with a 1500mm focal-length, is a bit too long... A focal-length of 900mm is seemingly the ideal, the sweet-spot, and that exists within this one... https://www.amazon.co.uk/TS-Optics-150mm-Newtonian-Telescope-Gsn1509ota/dp/B00IN7EBFW With that being the ideal compromise, albeit without a mount.
  12. Next up, the installation of the cowling with its secondary-stalk and -mirror...
  13. The hardware has been filed and sanded, roughened, for the paint...
  14. I had gotten a Thousand Oaks solar-film filter many years ago, and for my 102mm refractor only... The image is yellow-orange. The Baader solar-film is said to be superior, and the image bluish-white. In any event, that TO filter is quite dated. I'd be reluctant to use it again. I've had this sheet of the Baader film for a few years, but I haven't made a filter with it yet... When making and observing with a solar-filter, observe all precautions. Research others' experiences with the film online, thoroughly, and prior to making your own. You cannot be too safe in that regard. When installing the film into a home-made frame, the film must not be stretched in the least. It must be allowed to lay onto the glue or double-sided tape, used to secure it, under its own weight. It will have a wrinkled appearance, which is normal... https://www.firstlightoptics.com/solar-filters/astrozap-baader-solar-filter.html ...but the wrinkling will not affect the view in the slightest. You don't want it doubled over itself, nor stretched taut. A stretched film will distort the view. Avoid black-polymer filters and materials.
  15. Oh Julian; yoo hoo... ...and both assemblies at 4mm in thickness; therefore no intrusion into the light-path. It turned out that the shorter-length screws that I had bypassed initially, there at the left, were the perfect length after all. Oh well, all's well that ends well.
  16. In this instance, the spacing between the inner wall of the tube and the edge of the primary-mirror is at least 5mm, all round. Not a great deal, but enough to conceal the hardware that I'm utilising, and at a total thickness of 4mm.
  17. With longer-focus doublets, it can be difficult to tell which convex side is steeper. All one has to do is to install the crown, take it out to test, then flip the crown and test again. The correct side will make itself known, even that of an f/15, I've found. However, the correct side of an f/8.3 should be a good bit easier to identify, and to where there would be no need to flip the crown; an f6 or f/5 being most easily determined.
  18. Be certain to note the order of the doublet... The crown lens is convex on both sides. The side with the steeper curve faces the concave surface of the flint.
  19. I could probably get those locally in zinc-plated steel, but not in stainless. Then, the undersides of the heads of these screws do conform to the shape of the slots' wells, although not perfectly as though the two were one. I did go out the next afternoon; glamour shot... Ever so lovely they are. Would that I had had them right after that one had flown into space. I'd be done with it already.
  20. I have one like that. It's a just a bit shorter, yet a 70mm like that one. It just arrived, last week... It doesn't have a finder, but then it doesn't really need one, as it's a finder in its own right. You may wish to get a star-diagonal to use with it at night. The included diagonal is for use during the day, for terrestrial targets. https://www.amazon.co.uk/Diagonal-Adapter-Refracting-Telescope-Eyepiece/dp/B07GPMX7BN/ref=sr_1_2?keywords=svbony+diagonal&qid=1574104670&sr=8-2 An extra eyepiece or two will enhance the experience. You might even want a barlow... https://www.amazon.co.uk/Svbony-Multi-coated-M42X0-75mm-interface-Astronomy-green/dp/B01ET5BNHA/ref=sr_1_1_sspa?keywords=1.25"+2x+barlow&qid=1574104839&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyWFFWMzJaRkM5R05OJmVuY3J5cHRlZElkPUEwODQzNDMyMktNMjZYMlJTWExJSyZlbmNyeXB0ZWRBZElkPUEwNDU1MTAzMjBKUFRUVjNNUThVRyZ3aWRnZXROYW1lPXNwX2F0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU= Those are just examples of what's out there, and to make the most of it. eBay is another source.
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