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Everything posted by Alan64

  1. If, I say if, as it is now 2020, the primary-cell uses rubber-grommets for the springs, three of them at least, then you might want to replace those with heavy-duty, metal springs. The rubber will fail over time, and then you'll have to replace them anyway... The tension is then much improved, and makes collimating that much easier.
  2. The odd thing about it all is that we must assume that the back of the tube was cut precisely and perpendicularly to the length of same at the factory... ...and square to one another. Then, the plastic cell is practically perfectly flat, we hope; as is the mirror, and again we hope. Then, we assume that the three pieces of double-sided foam-tape used to install the mirror into the cell are of the same thickness. Lastly, as long as the cell seats fully onto the end of the tube, then there should be no need to adjust it. Does the cell fully seat onto the rim of the tube, in fact? There is one other thing. Elsewhere it had been opined that there's no need to center-spot a spherical primary-mirror. If the mirror is off-center, no matter, according to those individuals. The reason being is that the surface of the mirror conforms to a perfectly round sphere, and no matter where you place it round the sphere... Spherical-mirrors cannot focus all of the rays of incoming light from an object in the sky to a single focal-point, and as a result of its simple shape. But a parabolic-mirror can. The narrow end of an egg, a parabola... You cannot move the mirror round and about in that event, as its surface would not conform to the odd and uneven curvature of the egg. Therefore, you must center-spot a primary-mirror, and for a precise collimation. Again, a parabolic mirror can focus all of the incoming rays of light to a single focal-point, via its exotic curvature, which then results in the sharpest and most pleasing images possible. Still, I don't think that it's good practice in suggesting that a spherical primary-mirror does not need to be center-spotted, as that can lead to a beginner in not center-spotting their mirror at all, regardless of its curvature. A spherical-mirror is round, it has a center, therefore center-spot it... https://garyseronik.com/centre-dotting-your-scopes-primary-mirror/ This primary-mirror, from my "Bird Jones", is a spherical, therefore I center-spotted it... The telescope was then collimated, and I saw glory. Incidentally, all primary-mirrors are first figured into a spherical there at the factory, and then some of those are parabolised for other, larger, and more costly Newtonians. I can't help but wonder, if the optician is having a good day, if some mirrors that are destined to be shipped out as spherical are parabolised after all. Stranger things have happened, and all the more reason to center-spot a spherical primary-mirror.
  3. You won in that, then. Congratulations.
  4. Betelgeuse is 642 light-years(estimated) distant. If it exploded today, we wouldn't see the light from that until 642 years from now. Then, it would most likely be visible during the day, at least at dawn or dusk. On the other hand, if it had exploded 641 years ago, then we would see it in the sky next year. Betelgeuse, and courtesy of my 150mm f/5 Newtonian... By the way, books are most unlike monthly magazines. I get great entertainment from some of Patrick Moore's books from as far back as the 1960s.
  5. I imagine that the telescope has gained a bit of weight over the last three years, but for kicks and giggles I placed it onto its original mount... Before... After... I will probably use that mount when collimating the telescope. I may also give it another whirl round and under the night sky, at least once.
  6. Thanks Stu. The next step will be to collimate it, then to take it outdoors for an afocal photo-shoot, through this eyepiece and that. Although, this winter has been wetter than usual, but I'm still hopeful for a clear, dry night soon.
  7. After the matte-blackening, the dust-plug became a bit tighter-fitting, but no matter as now the entire cap can be removed with the dust-plug's single knob, and both the cap and plug as one. To cushion the dust-cap as it's inserted, shimming with felt or other could occur only here at these two areas, and between the aluminum-braces... Through trial-and-error over the course of a day or more, I finally arrived at the ideal combination of materials: one 5mm-wide strip of double-layered aluminum-foil tape, then one 9mm-wide strip of flocking, and for each side of the flange... Perfect fit... The altered dust-plug now allows ample clearance for the secondary-hub's thumbscrews... Other than the collimation yet to be performed, the telescope is completed.
  8. I have the same eyepieces and 2x-barlow that you have, and that came with my Meade kit... Those eyepieces and the barlow are not very good. The telescope itself should be, however. These are the same as those of the BST "Starguider" line... https://agenaastro.com/eyepieces/1-25-eyepieces/shopby/agena_dual_ed.html Plossls... https://agenaastro.com/eyepieces/1-25-eyepieces/shopby/gso-gso_plossl-gso_superview.html Plossls shorter than 9mm have small eye-lenses through which to see, and short eye-relief. The BST flat-field and planetary eyepieces... https://agenaastro.com/eyepieces/1-25-eyepieces/shopby/bst.html To reach the higher powers, I would suggest a 3x-barlow and a 12mm Plossl... https://agenaastro.com/meade-128-3x-barlow-07278.html
  9. You do want to exhaust the possibilities and solutions before any modifications.
  10. The slotting occurs on the optical-tube... Don't go up to and beyond the edge of the tube with the slot... I eventually took that further with my own...
  11. The entry-level Newtonian-Dobsons. like your nephew's, and this 100mm f/4 of my own... ...both have a primary-cell that cannot be collimated, as it arrives... It's simply a plastic tray with the mirror installed with three pieces of double-sided foam-tape... My own is the same as the "Heritage" 100P. Your nephew's is not a 76P, rather a 76mm with a spherical primary-mirror. A 76mm f/4 like that one should have a parabolic primary-mirror, but it doesn't. Some enlarge the three holes to allow some adjustment. Some even slot the holes somewhat to allow for even more adjustment. But that's about it, as it comes. The secondary-assembly, however, is collimatable, but I'm unsure as to the extent. It may certainly be tilted, at least. I would concentrate on adjusting that aspect. Is your laser-collimator tool collimated itself? Many do arrive mis-collimated, particularly the entry-level units. I have one myself, but I prefer to use passive-tools to collimate my Newtonians: a collimation-cap, and a Cheshire with cross-hairs; tried and true.
  12. Did you get this eyepiece with the kit? This one is from my Celestron "PowerSeeker" 172EQ kit... If so, then you can use it for daytime/terrestrial observations; birds in trees, ships at sea, that sort of thing. The eyepiece contains an Amici, erect-image prism at the bottom of the barrel which effects the correctly-oriented view. No other eyepiece will contains such, to my knowledge. Meade has offered one, too, in the past at least. There are image-erectors. They look like a barlow, into which you insert an eyepiece, but it's awfully long, and would jut out of your focusser like a tower... https://images-na.ssl-images-amazon.com/images/I/31w5%2BbvEodL.jpg Newtonians, however, are not configured and designed for such. Amici, erect-image diagonals can be used with refractors and Cassegrains(Maksutov and Schmidt), but not with Newtonians. If terrestrial observations are important to you, I would suggest getting a refractor, an inexpensive achromat.
  13. What you may want, in so far as a reliable source of power, is a marine, deep-cycle battery-box. They can have USB-ports and 12V DC connections. It would require a marine, deep-cycle battery, and a box to hold the battery, also to fit on the power-connections. They can be had ready-made, for trolling-motors, or you can make one just the way you'd want it fitted out to your specifications. Here's an example of a ready-made... https://www.amazon.co.uk/Minn-Kota-Trolling-Motor-Center/dp/B001PTHKMG That's just the box; no battery. Here's where someone customised a box, using that particular one... https://www.offgridweb.com/transportation/last-man-projects-200-diy-emergency-power-pack/ Now that's not so much configured for our purposes, but as a general purpose power-box. Research DIY battery-boxes online, for astronomy, and ones that make use of a marine, deep-cycle battery.
  14. If I purchased a kit or mount that required bog-standard batteries, I would not use those, as there are single, 12V, Lithium powerpacks to be had instead. After all, it is 2020 A.D.
  15. The dust-cap was masked-off where needed... ...then painted matte-black(chalkboard-black, as usual)... The recessed rim round the stopped-down aperture was blackened(left), and the reverse was blackened utterly. I will not be fitting the plug until after a day or so, and to allow the paint to dry/cure completely.
  16. And there I was thinking, all along, that Japan had handed over the blueprints; no, not really. The heart of any telescope kit is the objective. You can re-figure the primary-mirror of a Newtonian, at the home-level, but not the doublet-lens of an achromat. I've acquired a few entry-level telescopes, and the mirrors and lenses have been very good, if not excellent, and that determination made whilst simply observing with them. You will get your money's worth, and more besides, in so far as the objective. I feel that the manufacturers must provide at least that. Else, sales would drop dramatically. Incidentally, I'm not through with the mount yet. I had gotten a spare mount-head from Meade, under warranty, and for a wonky DEC shaft-assembly. For, in addition, I may have to replace this... ...as that hole for the RA-shaft results in slop. I've thought about a partial bronze-bushing of sorts, to tighten it up, but first I'll need to test the hole of the spare, to see if it would be worth the while in replacing it.
  17. The plug is not too loose, nor too tight, just right rather. Yes, you guessed right, and a final application of... ...felt; hard, red felt. For this type of shimming, you want the hardest self-adhesive felt you can find; none of that down-soft stuff, no, but it would be better than nothing at all.
  18. Aluminum-foil tape was applied round and over the plug's glossed flange, for a smoother substrate for the final application, and of...whoops, mustn't spoil it... I haven't even collimated the telescope yet. That will have to wait until the dust-cap and its plug are completed; although, it doesn't have to, but is going to rather.
  19. These mounts were designed and manufactured in Japan. The Chinese then cloned them, yet something was lost in the translation.
  20. Shhh, you're going to spoil the surprise.
  21. A 32mm Plossl serves two purposes: for the widest view of the sky possible, in helping you to find objects in the sky, and in tandem with the finder; then, for the widest views of the Milky Way, the Pleiades, and the galaxy in Andromeda.
  22. For the secondary-mirror, the hub, I take one of the recessed set-screws(for sizing up) to my local hardware and get socket-cap screws(thumb-screws essentially)... The white-arrow points to a white-nylon washer that I epoxy on the back of the secondary-mirror's stalk. That gives the set-screws something to dig into besides the soft metal of the stalk. Without it, the set-screws make dimples in the metal, making it difficult to create new, slight re-positionings of the mirror. The screws will simply want to slip back into the dimples of an older collimation position; a simulation...
  23. The next step was to apply clear-gloss enamel onto the flange all round... On top of that, something else will be applied. Then on top of that, something else again; but nothing else after that.
  24. The satin-black enamel I use is obviously oil-based, as it hasn't cured quite yet. Still, I attached the knob, permanently, and in order to handle it for the next step; glamour-shot...
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