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.


Louis D

Advanced Members
  • Content Count

  • Joined

  • Last visited

Community Reputation

1,659 Excellent


About Louis D

  • Rank
    Brown Dwarf

Profile Information

  • Location
    Texas, USA
  1. Louis D

    Eyepiece repurpose

    They make great tube plugs for focusers and diagonals to keep out dust.
  2. Louis D

    Wider FOV eyepiece for Mak

    I've used my 40mm Meade 5000 SWA to good effect in my 127 Mak for widest field views of about 1.7 degrees by adding a Mak-to-SCT thread adapter, a 2" visual back, and a 2" diagonal. I do get some some odd artifacts in the FOV when bright stars pass the edge of the Mak's rear port, but the wide views are fantastic. I really don't notice the vignetting that must be present.
  3. You might want to convert it to an alt-az mount to see if you get on better with the motions. You can do this by tipping the latitude adjuster all the way back so the polar axis points at zenith and locking it down in that position (if it moves that far back). Now, the two axes will move up-down (altitude) and left-right (azimuth) as if you were at the north pole (90 degrees latitude). You'll lose single axis tracking and will have to nudge both axes to track objects. If you don't like this mode any better, you can always switch back later to EQ mode. You might also want to loosen the slow motion clutches slightly, so you don't always have to use the slow motion controls to track.
  4. @mckinnell Did you buy the scope new? If so, it should have come with a 2" to 1.25" adapter. If not, contact your retailer about getting an OEM replacement sent out to you.
  5. I was going off of what Ernest measured in this CN post. He's quite accurate in his lens testing measurements on his optics test bench. His number agrees very closely with my measured number for my 27mm Panoptic, upon which the 28mm ES-68 was based.
  6. Usable eye relief is 14mm, very similar to the 27mm TV Panoptic which I mentioned above. I find it a bit too tight to be comfortable, thus the move to the 30mm APM UFF recently with 16mm of usable ER. Otherwise, it is reportedly a very fine performer falling off just slightly in sharpness at the edges.
  7. I really like the new 30mm APM UFF. It's a bit lower in power than you were thinking of, but it's a really sweet eyepiece for wide, low power views with good eye relief and moderate weight and size.
  8. Louis D

    New eyepiece??

    Take the money for another eyepiece and save up for a larger aperture telescope. I liked the views through my 8" Dob, but I wanted greater planetary detail, so I bought a 15" Dob a couple of years later. The difference is dramatic. However, I'm not sure UK skies are agreeable with large apertures like Texas skies. That, and the planets are 20+ degrees lower in the sky making it more difficult to see them through so much more atmosphere.
  9. Louis D

    Motion of telescope on a wedge

    There's nothing inherently bad about wedge mounted SCTs. The older SCTs from the 70s/80s/90s used well machined drives similar to GEMs and had very smooth tracking with low PE. The move to sloppy, lower cost goto mounts with stepper motors changed all that.
  10. If the refractor was an APO, it would easily win the horse race on an aperture for aperture basis, but it's an achromat, so it loses out to a reflector in terms of sharpness, contrast, and lack of false color. It does win as far as ease of setup since collimation and cool-down time is not an issue for most refractors and you won't need a coma corrector for it for good edge correction. That fast mirror in the reflector will need a coma corrector, but good luck finding a 1.25" one. The long discontinued 1.25" TV Paracorr is the only one I'm aware of. If the reflector had a spherical instead of a parabolic mirror, the contest would be much closer. It's all about trade-offs.
  11. Using a yard stick and a cell phone camera, I measured the increased magnification at the edge of my 27mm Panoptic to be over 25% more than in the center. It is quite noticeable compared to a similar photo through a Pentax XL which shows very little magnification (I didn't measure it, though). Working backwards from the measured TFOV, it has a 65 degree effective AFOV if you want to calculate the TFOV from magnification and eAFOV. Its actual AFOV is 69 degrees when measured with the flashlight projection method. By comparison, the 14mm Pentax XL I was using has a measured 65 degree AFOV and a 66 degree eAFOV for TFOV calculation purposes, so it must actually be shrinking the edges rather than expanding them as in the Panoptic. I'll have to check that Pentax photo's edges to see if that is indeed the case.
  12. Louis D

    Televue Dioptrx

    Unfortunately, I haven't heard of any method to remove it. If it could be done, someone would have decloaked it by now and posted pictures and instructions.
  13. Louis D

    Televue Dioptrx

    Right, astigmatism has both a diopter strength and an axis in degrees. It is that axis that has to be "tuned" by rotation. It's interesting that most eyes have multiple axes of astigmatism, each with their own strength, and opticians try to find the best compromise of strength and orientation to correct out as many of them as possible. Actual laser surgery on the eye can remove all of the various imperfections of the eye at once that no prescription lens could ever do.
  14. The APM 24mm UFF has about 17mm to 18mm of usable eye relief, so good enough to use with eyeglasses. It isn't actually flat of field or sharp to the edge like its 30mm bretheren, but it's pretty good if you can pick one up used for much less than the new price. The various 22mm 70 degree eyepieces marketed as Redline, Olivon, AF70, Astromania, Ultima LX, etc. are very well corrected to with 10% of the edge, sharp and contrasty, flat of field, and easy to use with eyeglasses without breaking the bank. The 9mm Morpheus is quite well corrected and easy to use with eyeglasses as Bill P. says above. If 60 degrees is enough field for you, the Meade HD-60s in 4.5mm, 6.5mm, and 9mm focal lengths are also extremely well corrected and easy to use with eyeglasses. The UWANs and their bretheren under other marketing names are supposedly quite good for the money, but they don't have nearly enough eye relief for eyeglass users. If you have strong astigmatism in your observing eye, you'll want to wear eyeglasses when observing, especially at lower powers (larger exit pupils). At higher powers (smaller exit pupils), you may find you don't need your eyeglasses to get a sharp image.

Important Information

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