Experiences With 127mm Refractor

As promised yesterday, I'm going to tell you a little about my experience with the 127mm homebrew refractor.  The first item I went to look at was a semi-bright star.  Not certain which one, I think it was one of the belt stars in Orion.  As I recall, it was a yellowish star.  I noticed right away that if the star was focused in the center of the eyepiece, as it drifted, it got progressively blurrier as it went off center.

Then I went after M42, as its easy to find and I was in the neighborhood anyway.  It was quite bright, compared to the 70mm and 114mm scopes I have.  Of course, M42 is much brighter in the 8 inch Dob, which is to be expected.  A quick peek at Sirius showed a blue star, pinpoint and bright  when focused.  From there, I attempted M51, Canes Venatici, but couldnt locate it.    After spending some time searching, I proceeded to Saturn which was higher in the sky.  There was thin cloud cover, more like a haze, the moon, low on the horizon illuminated the haze, and could be why I was unable to locate M51.

The home made focuser has no side to side slop that I could see.  However, it was not square with the tube, which I corrected today.  This is probably the cause of the focusing issue I was seeing.  I was not able to focus on Saturn as well as I have experienced with the 70mm refractor, but at the time I attributed it to the hazy sky.

Knowing that the telescope needed some more work and some fine tuning, I brought it back in after looking at Saturn.  Today, I re-seated the objective and squared up the focuser as best I could.  I used a laser flashlight and found the laser was off to one side of the objective.  I rotated the laser to make sure it was aiming straight, which it wasnt, but as I rotated it in the eyepiece holder, I saw the dot on the lens, rotate in a circle.  I then adjusted the focuser so that the circle was centered approximately equal from the outer rim of the objective as I rotated it around inside the holder. (the laser flashlight fit fairly well in the 1 1/4 inch focuser with very little slop).  I believe I have the focuser much closer to being true.

Now we need clear skies again to test the scope again.