Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.


  • Content Count

  • Joined

  • Last visited

Everything posted by Alan64

  1. Hi Neil, In case you didn't notice it within your other thread... https://www.harrisontelescopes.co.uk/acatalog/revelation-dovetail-mount.html#SID=1718
  2. Hi Neil, Your new mount is an EQ-3, and appears to have the same old-style mounting-interface as that of your "PowerSeeker" CG-2. I have a CG-2 as well, and I had replaced that interface with a Vixen-type. My Celestron CG-4 is an EQ-3, but with tubular-steel legs instead of those of aluminum. I don't care for the steel legs myself. It came with a Vixen-type interface... https://www.harrisontelescopes.co.uk/acatalog/revelation-dovetail-mount.html#SID=1718 Wilcox-rings... http://www.andysshotglass.com/wilcox_rotating_rings.html You can also use a spare tube-ring to effect that. You would have to add Teflon to it, and to slide against one of the rings holding the telescope. Congratulations on your find. Keep looking up, and clear skies to you always.
  3. A Herschel-wedge can be used with a refractor only, preferably a doublet. Also, the focusser, including the draw-tube, and the objective-cell retaining the doublet-lens at the front of the tube, and perhaps the dew-shield even, should all be of metal. All of the entry-level refractors coming out of China nowadays come with plastic objective-cells, and quite a few come with plastic focussers and draw-tubes. For those who disagree, do so at the telescope's risk.
  4. What type of telescope would you be using on the mount?
  5. https://www.firstlightoptics.com/alt-azimuth/sky-watcher-az-pronto-alt-azimuth-mount-tripod.html
  6. The Moon, at 33x through the 12mm Konig... Now, it was at freezing, I was using the original mount, with my old(2002) Minolta point-and-shoot, and with the shutter at 1/30th or 1/45th of a second. I did have to brighten the image to match what I saw during the live view. I never enhance these afocal-shots otherwise, never have, as that would be dishonest. During the live view I saw Earth-shine on the left side, but this old camera couldn't pick it up.
  7. I do know now that the telescope is collimated quite well. Sirius, extra-focally, and through a 12mm 60° Konig(33x)... I then observed the star with this, my SR4mm(100x) from my Celestron 127mm f/8 "Bird Jones" kit... The star was tight, yet as expected somewhat colourful due to the type of eyepiece. Afterwards, I used the 12mm to zero in on the Trapezium within Orion, then popped in the 4mm. I could just see the main stars, and sharply as well. It was difficult however to find the sweet-spot of sharpness as I racked back and forth.
  8. A variable-polariser is only good for what was discussed; specific, and of limited use. I would go with the 1.25".
  9. For better, or for worse, and through a collimation-cap... All I need now is a clear, night sky, and that will come in a day or two, but it's going to cold, cold, cold outdoors. But I won't need to be out there long. I hope the Moon will be out. I tried to use my Cheshire initially, but I don't think that it likes the visual-back of this telescope. I'll need to investigate that further, for it seemed to work well enough when I took this shot three years ago... Then this, the view through the collimation-cap three years ago... I did tweak the off-setting of the secondary-mirror in relation to its stalk during the renovation. Oh well, time will tell.
  10. That, sir, is an excellent question. I am impressed. You wouldn't want a Lumicon? https://www.robtics.nl/product_info.php?products_id=4993&pID=4993&language=en That one is regarded as the finest on the planet. My Orion(of California) v-p was made in Japan, too, many years ago. But there are economical alternatives. House/Generic brands... https://www.firstlightoptics.com/moon-neutral-density-filters/astro-essentials-variable-polarising-moon-filter.html https://www.365astronomy.com/365astronomy-variable-polarising-filter-1.25-inch.html https://www.rothervalleyoptics.co.uk/ovl-variable-polarising-filters.html Name-brands... https://www.rothervalleyoptics.co.uk/antares-variable-polarising-filter-125.html https://www.rothervalleyoptics.co.uk/celestron-variable-polarizing-filter-125.html ...new product Two of the these GSO filters to purchase and to screw together for a v-p... https://www.365astronomy.com/Polarisation-filter-with-30-transmission-level-1.25-inch-M28-5X0.6.html Orion(of California) still offers a v-p, but it's not made in Japan as my Orion was many years ago. Per your question as to the performance of a cheaper one, I cannot say.
  11. I'm afraid that the importance of a spot-on collimation cannot be over-emphasised. Do you know what a drill-sergeant is? This, my own variable-polariser... It simply dims down the light collected by the objective of the telescope. You still get the resolution of an 8", but there are times when you need to dim it down a bit. With my 6" f/5, the v-p eliminates the diffraction-effects of the secondary spider-vanes... Mars through my 6", during its last opposition, before and after... It also helps to detect the Moon-like phases of Venus. I don't think that Saturn would benefit from it, however.
  12. I had this 70mm f/13 achromat... ...up to 225x one night, aimed at Polaris, the north star. I could still make out the star's Airy disc, and its first and subsequent diffraction-rings; not quite as sharply as at 150x, but it was certainly not so-called "empty magnification", not at all. It can be the atmosphere, and the state of the telescope's collimation, in keeping you from making good, practical use of the 5.5mm(218x). We are at the mercy of the atmosphere, but we don't have to be at the mercy of a telescope's level of collimation.
  13. Per the old measurements, your 200P is capable of at least 50x per inch. Your telescope is an 8"... 8" x 50x = 400x That's the standard for Newtonians, 50x per inch before image-breakdown. But that is only possible under ideal atmospheric seeing conditions. Also, the collimation must be spot-on. Any telescope has to work harder at the higher and highest powers, therefore everything must be in order. Fine refractors, however, are known to reach 100x per inch. Under ideal atmospheric seeing conditions, my 4" refractor can reach 400x, but it would need to be on a motorised mount for a good look-see at whichever object I'd be observing at the time; most likely the Trapezium within the Orion nebula, at this time of year. The eyepieces and barlows also need to be of better quality. If you want to see what few people have ever seen, you're going to have to embrace, love, collimating; obsess over it even. When the planets come round again in a couple of years or so, you're going to want to see those at the higher powers. I guarantee it, and for that you may want a variable-polariser...
  14. One thing that I've learned over time is that if you don't push the magnification up then you will never know how truly capable a telescope may be in fact, and in showing the user that which few people have ever seen. Never say never. That applies to all telescopes, including your 200P. I recently got this refractive equivalent to your nephew's reflector... ...a 70mm f4.3 achromat, also with a 300mm focal-length. I haven't pushed it to its limits quite yet, as I've got to blacken and flock it first, but I do have high hopes, high-powered hopes, and when I insert the eyepiece/barlow equivalent of a 1.5mm(200x) into it.
  15. I would think that you might want to get him at least a 2x-barlow of his own to putter round, with the original kit-eyepieces... https://www.ebay.co.uk/itm/SVBONY1-25Barlow-2X-Lens-Multi-Coated-M42x0-75Thread-Camera-Connect-Interface/361950654736?hash=item5445f0b110:g:3hEAAOSwSKtaauef ...or... https://www.ebay.co.uk/itm/SVBONY-1-25-Achromatic-Barlow-Lens-2X-Metal-two-element-for-Telescope-Eyepiece/323934195326?hash=item4b6bfb8e7e:g:Q9EAAOSwaQ9dID84 Dedicated eyepieces at 5mm and, gracious, 3mm, among the inexpensive, standard ones anyway, have tiny eye-lenses through which to see, and poor eye-relief where you'd have to almost if not actually touch your eyeball to the eye-lens of the eyepiece to see the full field-of-view. Rather, a wider-angle 6mm with a larger eye-lens, and combined with a 2x-barlow would realise a wide-angle 3mm... https://www.ebay.co.uk/sch/m.html?_odkw=&_ssn=retekessofficialstore&_armrs=1&_osacat=0&_from=R40&_trksid=p2046732.m570.l1313.TR12.TRC2.A0.H0.X6mm.TRS0&_nkw=6mm&_sacat=0
  16. Yes, that slight point is due to the secondary-stalk. Hopefully, once you get it as precisely collimated as you might, the images should be sharper than they were before. Resolution, the level of detail, is dependent upon aperture; the more the merrier. Do keep in mind that that's the smallest Newtonian on the planet, yet larger than what Newton himself had at his disposal. The general, static range of eyepieces, from 4mm to 40mm, works differently with this telescope and that. A 10mm can be a high-power eyepiece for one telescope, and a low-power for another. In this case it's a low-power somewhat, 30x. In theory, that being a 3" aperture, it is capable of up to 150x, and a bit more even when aimed at the Moon. Let's see what 100x would take... 300mm ÷ 100x = a 3mm eyepiece. 3mm eyepieces aren't particularly plentiful. I would combine a 9mm eyepiece with a 3x-barlow, and for a effective, simulated 3mm. A 3x-barlow for that one, if you want to max it out. A 2x can be useful as well.
  17. When you look down into the empty focusser you should see that the secondary-mirror is centered directly underneath the focusser, and that it appears as a perfect circle... I could tell within one of your images that the secondary-mirror appears rotated off to one side. The mirror is actually oval in shape, yet tilted at a 45° angle... This is true for all Newtonians. It therefore appears as a circle, as you see it through the focusser, and as the primary-mirror "sees" it from the back... Be careful when rotating the secondary-mirror, as we do not yet know how that is effected. You will probably need to loosen the three tilting-screws round the hub in order to free it up in order to rotate it.
  18. You want to level the mount, align its RA-axis to Polaris(NCP), then attach the telescope and balance it.
  19. Refractors have always, usually, been the only telescopes with rigid dew-shields pre-installed... ...but then, the colour is not always matched to that of the telescope's tube... Then, you have the rigid dew-shields provided with this iOptron Maksutov-Cassegrain, and this Explore Scientific Maksutov-Newtonian... https://i.imgur.com/aRJPoIj.jpg Those match the tube. You rarely if ever remove a dew-shield from a refractor however. Then, Astrozap offers rigid dew-shields in Meade and Celestron colours... A rigid dew-shield can be made easily enough, with aluminum-sheet and pop-rivets, lined with a black absorptive material, then painted whatever and whichever colour or colours you'd like.
  20. Hmm... I have a black Farpoint dew-shield for my white Maksutov... ...meh. What about chartreuse, and fuchsia... Then, there's burnt-orange and avocado... Mustn't forget burnt-orange and avocado.
  21. Oh, that new dew-shield will not only block stray-light sources, but it will also help prevent the secondary-mirror, and the primary-mirror, from dewing or frosting over.
  22. That's okay, as I didn't understand it when I first came across it, and several weeks ago. It sounds to me that that mirror is parabolic, if the mirror is directing the laser-beam when tilting the mirror.
  23. The grommets, and the springs, go over the adjustment-screws, not the locking-screws. I had forgotten to mention that. Just shine a light between the components of the cell...
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.