Jump to content

Banner.jpg.39bf5bb2e6bf87794d3e2a4b88f26f1b.jpg

Alan64

Members
  • Posts

    2,329
  • Joined

  • Last visited

Everything posted by Alan64

  1. Yes, during these troubling times, what little is available is flying off the shelves. I'm oft frustrated by that myself; not just for myself, but for many others as well.
  2. Yes, I've seen that one many times before. It's identical to my own, other than the colour and the position of the focusser. I got my own specifically for observing the galaxy in Andromeda, and at 13x with a 32mm Plossl. Here's the Moon through my own, and at 13x... I would suggest a telescope with a bit more focal-length than 400mm. It's difficult to reach the higher powers with one that short. The planets become interesting at 150x and higher... 400mm ÷ 150x = a 2.7mm eyepiece, or an 8mm eyepiece combined with a 3x-barlow The sweet-spot among entry-level telescopes is a 900mm focal-length... 900mm ÷ 150x = a 6mm eyepiece With 900mm, you have the lowest power of 28x, and with a 32mm Plossl. By that, you can see how better balanced a 900mm focal-length can be. Look at the secondary-obstruction of our 4"/400mm Newtonians, then that of my 4.5"/900mm Newtonian... Secondary-obstructions cause a loss of contrast and sharpness. It's akin to a cataract of the human eye. The smaller the "cataract", the better the image quality. Needless to say, the unobstructed, albeit smaller, apertures of refractors exhibit the best-quality images.
  3. I'm curious as to mysterious nature of the 4" reflector. 4" reflectors are a bit rare. I have this one... There are also the 4.5" Newtonians. I have this long-focus one... This is a 4.5" Newtonian-Dobson, sold only by Orion... https://www.telescope.com/Orion/Orion-SkyQuest-XT45-Classic-Dobsonian-Telescope/rc/2160/p/102009.uts There are also short ones, like that 4"... https://www.telescope.com/Orion/Orion-StarBlast-45-Astro-Reflector-Telescope/rc/2160/p/102010.uts ...and... https://www.telescope.com/Orion/Orion-StarBlast-II-45-EQ-Reflector-amp-AstroTrack-Motor-Drive/rc/2160/p/116990.uts However, the shorter ones are not as optically performance-driven as the longer ones are. A 5"/127mm Maksutov is "thinking out of the box" among the still-affordable kits. Maksutovs have rather long focal-lengths, and perform best when mounted on go-to mounts. They can be used on manual mounts, but a Maksutov needs a capable and reliable finder to help it find its way round the sky. As examples, to illustrate, in the U.S., there are the Orion and Sky-Watcher models... https://www.telescope.com/Orion/Orion-Apex-127mm-Maksutov-Cassegrain-Telescope/rc/2160/p/9825.uts https://www.highpointscientific.com/skywatcher-127mm-maksutov-cassegrain-telescope-ota-s11520?utm_source=google&utm_medium=cse&utm_term=SKY-S11520&gclid=CjwKCAjw5c6LBhBdEiwAP9ejG5Dkk5nFEzIWDmiNtQrPh1yusEMgOF91B3kHsTZS6t--fKm8nefuFxoC6uYQAvD_BwE Curiously, of all the astronomical-equipment vendors throughout the world, Orion, of California, seems to be the least affected by shortages, I've noticed. You then find a suitable mount for the telescope, for example... https://www.bhphotovideo.com/c/product/1046130-REG/explore_scientific_maz01_00_twilight_i_adjustable_head.html/?ap=y&ap=y&smp=y&smp=y&lsft=BI%3A514&gclid=CjwKCAjw5c6LBhBdEiwAP9ejG7DGvBgT8XI8EgdY5zliGqxbXVkI8J7qhtXNSPXisIFn5OEADS6XohoC8PMQAvD_BwE Or, there is the option of a go-to kit... https://www.highpointscientific.com/celestron-nexstar-127-slt-computerized-telescope-22097?utm_source=google&utm_medium=cse&utm_term=CEL-22097&gclid=CjwKCAjw5c6LBhBdEiwAP9ejG8O_RyZ2FuYyZCixfqgsYU3Y634G0TkDjvhyQFcFPeCk1yIveY59GxoCTKQQAvD_BwE Then, my own 127mm Maksutov is even longer than those three, and blind as a bat. I can't use a go-to mount, as I have too many trees... Instead, I'm in the process of readying this 70mm f/4.3 refractor, and to help the Maksutov "see", to find its way round the sky... Others make do with a red-dot finder or other. Among the more economical kits, the manufacturers throw in a mount, and oft unsuitable for supporting the telescope that comes with it, like that long-focus 4.5" Newtonian above, within the second image. Here, I have that same telescope on a sturdier, alt-azimuth mount... Then, the Orion 4.5" Newtonian-Dobson comes with just that, a simple, Dobson alt-azimuth base. There is this Celestron 6SE... https://www.bhphotovideo.com/c/product/440825-REG/Celestron_11068_NexStar_6_SE_6_0_150mm.html/?ap=y&ap=y&smp=y&smp=y&lsft=BI%3A514&gclid=CjwKCAjw5c6LBhBdEiwAP9ejGyfC1cB93lojF5t5hVipu2eoytMpCnM-DuYyQd4sF4dHhkiZ7InnFxoC2SwQAvD_BwE That being a Schmidt-Cassegrain, and a relation of the classical and Maksutov Cassegrains.
  4. There is the aspect of collimation associated with Newtonians, and Newtonian-Dobsons, the latter which you are considering. The process entails a learning-curve, which your relation seems to be already set, and in learning how to collimate. The 8" is at f/6, and easier to collimate than an f/5. There is also this 6" f/8 Newtonian-Dobson... https://www.bhphotovideo.com/c/product/1141699-REG/sky_watcher_s11600_6_traditional_dobsonian.html/?ap=y&ap=y&smp=y&smp=y&lsft=BI%3A514&gclid=CjwKCAjw_L6LBhBbEiwA4c46ukmDqcOTAPO8ENdTeJPsw_j22hiZU_dWwrTCo1cQa_Io2YSeP2lKDRoCEkMQAvD_BwE At f/8, the 6" is even easier to collimate. It's the same length as the 8", yet slimmer due to its 6" aperture. A 6" f/8 Newtonian has been a classic choice for decades... http://www.company7.com/library/criterion_rv6.html That one would be the closest in ease of collimation in relation to a refractor which requires virtually no collimation at all. The construction of a refractor is tighter, rigid, with virtually no maintenance. Collimating a Newtonian has been compared to the fine-tuning of a stringed instrument, and in the playing of one perhaps. You might also consider a refractor, a 4" for example... https://www.highpointscientific.com/celestron-starsense-explorer-dx-102-mm-refractor-22460?utm_source=google&utm_medium=cse&utm_term=CEL-22460&gclid=CjwKCAjw_L6LBhBbEiwA4c46ulrpsjg4GNBOFIJ8jgu6xbzI5ca6hdXN3xmzvucJMxr5QMcpQxxg3RoC8dsQAvD_BwE That kit comes with a computerised push-to system, and for use with a "smartphone" app. That might be just the thing. I got one these last month, and I'm very excited as to the prospects... https://telescope-warehouse.com/shop/ols/products/meade-708010-s102-102mm-refracting-telescope-complete-kit-excellent-condition The kit is second-hand but in very good condition. They won't be available for too much longer. The seller is a liquidator for Meade products, and has been in business for decades. But the refractor is permanently tethered to that mount, I'm afraid. You can remove the telescope from its mount, for storage, travelling, but it can't be used with other mounts. I'm in the process of enabling that aspect at present. It requires removal of the fittings from the optical-tube, then to add tube-rings and a Vixen-type dovetail-bar. At that price, you could get that refractor alongside a "Dobsonian", but be forewarned, as your relation might come to prefer the former over the latter. The refractor can also be used during the day, as a spotting-scope, for birds in trees, ships at sea, that sort of thing; and in my case, for surveillance, day and night. A Newtonian cannot be used for such. Whatever you choose in the end, I know that your relations will be beyond thrilled.
  5. Indeed there are. Recently, I received a totally unexpected windfall, an insurance rebate-check. Just prior, for quite some time, I had been toying with the idea of getting a 76/700 Newtonian on a yoke-style alt-azimuth, an AZ1-class... Just a li'l grab 'n' go kit to kick, knock round and about the lay of the land. But once that rebate arrived, and combined with a bit of birthday-cash, my horizons expanded, albeit only somewhat. I then ran across this, a 102mm f/6 achromat, and it, too, on a yoke-style mount... It was offered by a Meade liquidator out in Arizona. The seller still has them in stock, as of this writing... https://telescope-warehouse.com/shop/ols/products/meade-708010-s102-102mm-refracting-telescope-complete-kit-excellent-condition O, the possibilities with that one, as a daytime spotter, for leisure(birds and ships); and surveillance even(the delinquent and nefarious), at night as well. An unobstructed 102mm aperture is simply luxurious, and bright... You can't use a Newtonian for that sort of thing, not easily in any event. Its short tube a pleasure to handle and stow away... At present, I'm about to place it into tube-rings, but first I must fill, seal, the six holes left behind... Once that's done, I may then attach the refractor onto any of my other mounts, at last. Indeed, that has been my goal all along, as I knew that the mount included was just to get the telescope up off of the ground, and little else. At night, what a fine sweeper of the skies it will be, and with the odd higher-powered view on occasion. Now, just imagine how much more exciting, and riveting, a 120mm or 127mm would be.
  6. "...without costing too much...", would be just how much exactly? For the last twenty years or less, we have been living in the heyday of inexpensive telescopes, and manufactured by a small handful of companies in China. These companies have come a long way since their respective beginnings, and in producing above-average and even fine optics these days, of lenses and mirrors both, of refractors and Newtonians both. With Newtonians, Newtonian-Dobsons("Dobsonians") in this case, you get a larger aperture over that of a refractor, per pound spent. With a refractor or a Newtonian, what you see is what you get. If either has a long tube, it will have a long focal-length; if a short tube, a short focal-length. The lower powers are less demanding on a telescope, and are the forte of the shorter telescopes. The lower powers also reveal the largest, the widest views of the night sky, and binocular-like. Objects in the night sky are easier to find with those shorter. Views at the higher powers are possible, to about 100x or so. Hence, I would recommend a shorter example of either of the two designs, and for a balanced, well-rounded experience. If you choose a Newtonian, there will be maintenance of the optical-system, collimation, to perform on occasion; like the fine-tuning of a stringed musical instrument. The more often the "violin" is "played", a "bass-violin" even, the more often the tuning required. If you choose a refractor, like a 90/660 achromat as previously suggested, there would be virtually no maintenance required. Although the aperture would be smaller, again, per pound spent. But under darker skies, a 90mm unobstructed aperture would show a great deal. With chairs, and a few tables of somewhat varying heights arrayed about and round the viewing area, a tabletop Newtonian-Dobson would serve; for example... https://www.firstlightoptics.com/bresser-telescopes/bresser-messier-6-tabletop-dobsonian.html There are the collapsible tabletop Newtonian-Dobsons, which are easier to put away upon the Sun rising... https://www.firstlightoptics.com/dobsonians/skywatcher-heritage-130p-flextube.html https://www.firstlightoptics.com/dobsonians/sky-watcher-heritage-150p-flextube-dobsonian-telescope.html However, I can't help but think about the mechanics of those, the pulling-apart and the collapsing, and how they might become damaged more easily over time; wonky in their motions. A 130mm or 150mm aperture would be quite the eye-opening experience for your guests. Then, for whichever you choose, a 7-21mm or 8-24mm zoom-ocular is an absolute must.
  7. The Exos-2 is an EQ5-class equatorial mount. The Exos-1 smacks of an EQ3-class, similar in appearance, but it's actually in between an EQ-2 and an EQ-3 in so far as load-capacity, an EQ-2.5 if you will. This is an EQ-1, on the left, which is the smallest equatorial mount on the planet... On the right is a Bresser "Twilight Nano" alt-azimuth mount, an AZ1-class mount. Both are supporting a 70mm f/12.9 achromat which is actually a bit too large for either one of those mounts. This is an EQ-2, and a bit more supportive than an EQ-1... Although that Meade 114/900 Newtonian is too large for it, as well. But in both cases, that's how the industry pairs an entry-level mount and telescope together, and oft ill-fittingly. My Celestron CG-4(EQ3-class) and Meade LX70(EQ5-class) mount-heads... Incidentally, the Vixen Porta II alt-azimuth is in between an AZ2 and an AZ3, an AZ2.5 rather, but not the AZ3 of "renown" which is actually an AZ2-class alt-azimuth, and the alt-azimuthal equivalent to an EQ-2. I do hope that that clears things up a bit. Know that refractors differ from all other types of telescopes in different ways. One of those is that a refractor requires a sturdier mount, per inch of aperture, over the rest. You can cheat a little with a somewhat shorter tube, but in the end you cannot escape the inevitable. Then, nor can a sensible and serious refractor be placed onto, within, a Dobson alt-azimuth base.
  8. My bad; I have since edited my original post. It was with an 80/480(f/6) achromat, and a Vixen 6mm "NPL" Plossl, at 80x. My 70/300 is disassembled still, and before the diagonal had arrived. I will be testing the diagonal further, and then decide if I want to keep it, or chuck it back to SVBONY. Not surprisingly, my Celestron star-prism diagonal, the third contender, handily beat the two star-mirror diagonals. Indeed, there was an almost 3D quality with the star-prism, which left the star-mirrors in the star-dust.
  9. If we match the numerals, EQ-5 vs AZ5, the Sky-Watcher AZ5 is not actually the alt-azimuthal equivalent of an EQ-5; more like to that of an EQ-3 rather. My own alt-azimuth, previously illustrated, is the alt-azimuthal equivalent of an EQ-4, but not quite to that of an EQ-5. The SkyTee-2 is fully the alt-azimuthal equivalent to an EQ-5, but not an EQ-6. The Chinese numeric codes for these mounts can be a bit perplexing, I'm afraid. Then, this is the Bresser "Twilight I", and fully the alt-azimuthal equivalent of an EQ-3. It seems to have been available at some point in the UK, but no longer. I don't know if that has to do with the pandemic, or customs/marketing hiccoughs... https://www.bresseruk.com/Astronomy/BRESSER-Twilight-I-telescope-mount-with-tripod.html Now we come to this comparison, and from Australia... That's the Saxon "Twilight I", same as the Bresser, and the Explore Scientific "Twilight I" sold in America I might add. Note that the Saxon is described as an AZ5 as well. But both of those are by no means alt-azimuthal equivalents of an EQ-5. My own alt-azimuth is more supportive than both of those, and it's not the alt-azimuthal equivalent of an EQ-5 either. It has been said, "Buy once, cry once".
  10. I made certain many years ago that I was to have an alt-azimuth mount, large enough to support a wide range of telescopes, and up to a 150mm aperture in my case... That mount is the same as this one, but my own came with a pier-extension and an integrated eyepiece-tray as options... https://www.teleskop-express.de/shop/product_info.php/info/p1753_TS-Optics-Altazimuth-Mount-GSAZ-with-fine-adjustment-and-tripod.html Said options are no longer available for that mount. I'm of the belief that most should have at least one tripod-type alt-azimuth, one that will, again, support a wide range of telescopes, for you never know what you might acquire over the years, and decades. I have over twelve telescopes myself. In addition, it is imperative that the mount comes with slow-motion controls, as objects fly through the field-of-view of most eyepieces rather quickly. Said controls allow you to "capture" an object, then to keep it in view for as long as you'd like. This is especially important at the higher powers. On the side, for more serious pursuits, you might then get an equatorial. Granted, this does not take into account go-to mounts or excessive light-pollution.
  11. Your telescope is at f/5(f/4.8, close enough), therefore use a 5mm(240x) eyepiece, or the equivalent with a barlow, for collimation/star-testing.
  12. I finally got myself a 1.25" star dielectric-mirror diagonal... https://www.amazon.co.uk/Dielectric-Diagonal-Reflectivity-Coatings-Compression/dp/B08QRY4V97/ref=sr_1_1?dchild=1&keywords=svbony+sv188p&qid=1634233841&s=electronics&sr=1-1 I've tried it out once thus far. I pitted that one against this star-mirror diagonal, from an ES/Bresser kit, not a dielectric of course, and I did not notice any improvement whatsoever... As a matter of fact, the ES diagonal was seemingly better than the SVBONY dielectric, but only by a slight margin. But I will have to test them further in future, and before a definite conclusion. I tested the diagonals with this 80mm f/6 achromat... Therefore, at this point, I would not select a dielectric-mirror diagonal. For now, select one with a standard mirror rather, for example... https://www.amazon.co.uk/Diagonal-Adapter-Refracting-Telescope-Eyepiece/dp/B07GPMX7BN/ref=sr_1_22?dchild=1&keywords=astromania%2Bstar%2Bmirror%2Bdiagonal&qid=1634234686&sr=8-22&th=1 There are those cheaper, so consider those as well.
  13. The Sky-Watcher "Heritage" 130P and 150P Dobson kits come with shorter, thereby ergonomic, f/5 Newtonians(reflectors). All reflectors require maintenance, collimation, optical-alignment, often initially, and regularly thereafter on occasion. One or both of the parents will need to learn and master the process... https://garyseronik.com/a-beginners-guide-to-collimation/ Refractors, on the other hand, require virtually no maintenance, and are ready when you are... https://www.firstlightoptics.com/evostar/sky-watcher-evostar-90-660-az-pronto.html The refractor may also be used during the day, for birds in trees, ships at sea, that sort of thing; a Newtonian cannot. But a child must supervised, during the day particularly, and to be taught to never point any telescope towards the Sun.
  14. There is absolutely no rush whatsoever in picking out one's definitive refractor; the longer the wait, the better actually. Play with the mirrors, first. However, in the meantime, I feel that you, also, might work up to one? A little taste of what might come... https://www.firstlightoptics.com/evostar/sky-watcher-capricorn-70-eq1-refractor.html ...a 70mm f/12.9 achromat. I have one of those myself. I got it just this past summer... Although, that kit is a combination from three others, one from early 1980s, 39 years ago... We go about our daily lives seeing with our eyes, which employ lenses. Then, there are lensing-galaxies in space, which act as refractors in revealing older objects behind them, and magnified... https://www.youtube.com/watch?v=51YYnaIWzsU Are you not in the least bit curious as to what a refractor might offer?
  15. Among refractors, a 102mm, or 4", is the "sweet spot" among the varying apertures of the design; not too large, nor too small, just right rather. I had to work up to one myself. At the age the 8 or 9, I got my very first telescope, a Sears(Towa) 60mm/2.4" f/11 achromat... It needs restoring, as it is almost fifty years old. It had also gone through a conflagration, yet survived. I intend to keep it as original as possible, tripod and all. It was through that telescope that I observed my very first object ever: Saturn, and with my late father who had first found the planet, and then called me out from the house to look. Saturn was sharp, small, yet sharp as a tack, with an eerie fluorescent-green colouration, and likely due to the planet's lower position, somewhat above the horizon. That was my only telescope until I was 27. I then got a Parks Optical(Towa) 80mm/3.1" f/11... That second was quite an upgrade from the first. Eventually, I gave that one to a relation, and after its upgrade. My first upgrade from that one was a Vixen 102mm/4" f/9.8 achromat... But I returned that one after having it for only a few days. I had simply and quickly decided that for my definitive 4" refractor, I wanted something else, something special. That was in 2003, and the same year I acquired a 102mm/4" f/8 fluorite-apochromat... I knew, even back then, that it would be most unlikely that I would ever get one larger than that, and for the rest of my life. To this day, that still holds true, more than ever. Then, we have this, the modern incarnation of that one... https://www.firstlightoptics.com/takahashi-fc-100-series-refractor-telescopes/tak_tfk10310.html
  16. Well <tweaks dastardly moustache>, Celestron had treated the subject... https://www.celestron.com/blogs/knowledgebase/i-accidentally-took-apart-my-celestron-20mm-erect-image-eyepiece-how-do-i-put-it-back-together I don't like my own. The view is too narrow for a 20mm, although you do get an erect, corrected image with the telescope. Otherwise, it's hard as dried beans to find an alternative; shame, that.
  17. Oh, don't set that 4mm(250x) aside, or throw it away. I snapped this shot of the Moon through it and the 127mm telescope... The live view was much sharper than that, and riveting!
  18. I have a Celestron "PowerSeeker" 127EQ. It also came with a 20mm erecting eyepiece, and both just like your own... This is the order of the lenses... At the bottom of the eyepiece, there resides the Amici erect-image prism...
  19. Also, don't have any regrets whatsoever in having gotten that one, instead of the "Starbase" 9mm "orthoscopic", as the "Starbase" is not a traditional, tried-and-true, Abbe orthoscopic.
  20. You don't want liquid seeping round and into the lenses. I use a cotton-swab very lightly moistened with 91% isopropyl-alcohol. You shake the swab after dampening it, or tap it against a hard edge of a table or other. You can also press the tip into an absorbent towel or other. Then, wipe the lens gently. It won't harm the coatings.
  21. I got this 80mm f/11 achromat, with an EQ2-class mount, all made in Japan, and for US$699 in 1992... Today: $1363 Nowadays, the kits are made in China, much less in outlay, and in many cases every bit as good, the OTAs in particular.
  22. At this point, I don't think a 12" "Dob" is going to do it for you. How about this rather... https://www.firstlightoptics.com/dobsonians/skywatcher-skyliner-400p-flextube-dobsonian.html
  23. There are some qualitative aspects of Newtonians, therefore a bleeding over I admit, but in the end it's all about quantity rather. There's simply no cure for aperture-fever, I'm afraid.
  24. It's not surprising that the mirrors are done in-house, as mirrors are easier to produce. But then, we all know how superb Takahashi mirrors are, and to where one might wonder as to why not lenses as well, of crown and flint at least.
  25. Filters for the planets are coloured... The only one that I would suggest, and with reservations still, is the light-blue, #82A. For example... https://www.firstlightoptics.com/visual-oberving-rgb-filter-sets/astro-essentials-125-wratten-82a-light-blue-filter.html The rest are only to look pretty, whilst simply standing over them arranged like that.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.