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Louis D

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Posts posted by Louis D

  1. 1 hour ago, russ said:

    If it was me, definitely the ED120 if the price is similar. I'm sure the optics are very nice in the Starfield 102 but I know for a fact they are great in the 120 as I use one as my main scope. Detail on Jupiter this past season, when conditions allow, has been superb. Doubles are extremely nice. 

    Have they improved the focuser on it recently?  5 years ago, I was looking at buying a used one that had been upgraded to a MoonLite focuser because the stock focuser was not so great.

  2. On 10/01/2024 at 04:33, mikeDnight said:

    Telescopes using an English fork design can travel straight past the meridian without the need to flip the scope.

    Same goes for harmonic mounts without counterweights.  Not only that, they can track backwards just as accurately as forwards without backlash:

    Watch for when totality begins and it starts scanning around the solar/lunar limb.  A direct drive could probably do the same thing as well.

    • Like 1
  3. On 03/01/2024 at 07:26, malc-c said:

    In fact, where a scope uses any goto feature the clamps should remain locked once the alignment has been completed.  If the clutches / locks are released and the scope is free to rotate even the slightest amount, any further gotos will be off.

    I thought the Sky Watcher Freedom Find mounts use encoders to keep track of alignment regardless of the clutches.

  4. In the case of GSO 2" to 1.25" adapters, it maintains parfocality between 2" and 1.25" eyepieces if both have their focal plane at the same distance relative to their shoulders.  Notice below how the 1.25" adapter's opening is recessed exactly as much as the thickness of its lip so the shoulder of the 1.25" eyepiece will be at the same level as a 2" eyepiece's shoulder in the absence of the adapter:

    spacer.png

    It actually works quite well to avoid lots of refocusing if your eyepiece collection is parfocal between 2" and 1.25" eyepieces.

    • Like 1
  5. To be clear, when using 2" eyepieces, just insert them into the big opening without the adapter.  When using 1.25" eyepieces, insert the adapter into the big opening, and tighten the big opening's screw to hold the adapter firmly. Next, insert the 1.25" eyepiece into the adapter's smaller opening and tighten its screw to firmly hold the eyepiece.  I hope that makes sense.

    • Thanks 1
  6. For straight through correct image viewing, there used to be erecting porro prism units sold by Celestron in particular.  Technically, you could substitute high reflectivity mirrors for each prism reflecting surface.

    spacer.png

    IIRC, if you have enough back focus, you can use two right angle mirror diagonals in sequence and then view looking in from the side of the scope.  Perhaps if you adjust the angles as with the Matsumoto unit, you could view from behind the scope.

    I haven't played with this concept in years, so my memory might be a bit faulty.  About 25 years ago, I was trying to make a correct image, compact viewfinder scope using 2" clear aperture, surplus right angle prisms bonded at right angles to each other.  It worked rather well, but it was insanely heavy due to all the glass.

    • Like 1
  7. Sounds like a new thread in the making.  Ugly or Not Ugly for various eyepiece lines.  The Delos have been likened to chicken drumsticks.  Whether that is ugly or not could go either way depending on how you like the looks of drumsticks. 😁

    • Haha 1
  8. @DaveG64 Are you asking about a field derotator?  They're normally used with alt-az mounted scopes.  If you're using a RA-Dec aligned mount, you shouldn't need one.

    The built-in rotator is there for framing purposes.  If you're alt-az mounted, it could still be used for this purpose, with the derotator following it somewhere in the rest of the focuser chain.

    • Like 1
  9. 14 hours ago, Highburymark said:

    From my inexpert calculations, Paul, the XWA 20mm will vignette slightly with the Baader T2 amici prism, but not by much. The prism has an aperture of 32/33mm and the APM 20mm has a field stop of 34.8mm (according to Don Pensack) despite an advertised 37mm, which should mean you’ll barely notice the difference. I stand to be corrected on this - but it’s amazing how few eyepieces vignette with the Baader T2 diagonals (I also have the standard Zeiss prism and BBHS mirror). However, it does mean you’ll need a 2”/T2 clicklock ep holder for 2” eyepieces to attach to the prism.
     

    You could probably only detect the vignetting of that combination by taking a photograph of an evenly lit sky or light colored wall through it and comparing it to one taken through a full 46mm or larger clear aperture diagonal.

    • Like 2
  10. Have you used the time to make a shroud and align the RDF?  How about checking collimation?  What about wrapping the focuser threads in Teflon tape?  Just throwing out ways to constructively pass the time while waiting for clear skies.

    • Like 3
  11. Here's a composite image of the image through various telescopes of mine taken on the same night:

    ST152150Newt90APOvs72ED1.thumb.jpg.4cc813f71cfa3360a8864b6e9d2de3c1.jpg

    They are all shown at the same resolution from my smartphone camera.  I didn't both to 2x the ST152 achromat because the 1x image was so mushy.  Ignore the brown coloration.  It's an artifact of the eyepiece I was imaging with.

    Here's a composite showing various filters applied ahead of the camera when using the ST152:

    ST152Filtering1.thumb.jpg.3cc9cde858763d15c56db5604724d314.jpg

    You can improve sharpness by filtering out more and more poorly focused wavelengths of light.  Green is the sweet spot for achromats.

    Longer f-ratio achromats will have fewer issues, but then you'll have to deal with a really long tube.  Think f/15 to f/25 to get closer to ED and APO performance out of an achromat.

    • Like 5
  12. 3 hours ago, Mark at Beaufort said:

    Although I have seen so many objects from the various lists I decided to buy the book recommended by kev100. It really is an excellent book and we'll worth the cost of buying it from FLO.

    I know that the original poster RJC recommended 10 objects but this book covers so much more. I recommend it to anybody.

    I took a look at the list of the 50 objects in that book, and it's odd that its missing some obvious (or at least easy) crowd pleasers like M27 (Dumbbell Nebula), M17 (Omega Nebula), Epsilon Lyrae (Double Double), and any of the M34/M35/M36/M37/M38 open clusters.  Many of the objects listed also require dark skies to make out, so not very good choices for the average suburban observer.

    If you really want endless observing possibilities, look for volumes 1 and 2 of The Night Sky Observer's Guide by Kepple and Sanner.  Sky & Telescope's store has new copies of volume 2.

  13. To see the aberrations, you really need darkness.  That means either testing at night or in a dark or near dark room of sufficient length.

    I would recommend a black nickel ball bearing.  The chrome ones seem to reflect too much stray light from the light source, making it difficult to see aberrations.

    I've yet to perfect an indoor technique after trying clear Christmas tree light filaments, chrome and black ball bearings illuminated by a tactical LED flashlight (torch), or a backlit foil pinhole using various light sources.

    Good luck and let us know what works for you.

    • Like 1
  14. The other day I was trying to look at the moon while the sky was still bright in my 6" f/5 GSO Newt using a 40mm eyepiece to center it.  Man, was I fighting the secondary obstruction.  A quick calculation in my head of 40/5 = 8mm and my likely 2mm entrance pupil explained to myself why.  After dark, even with the 40mm, I wasn't noticing the issue partly because of the dark background making it easy to shift the shadow to the side of the moon's image by not keeping it centered.

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