Dark Spot in Pentax XO 5mm
Posted 20 November 2012 - 07:16 PM
I tried my new Pentax XO 5mm today on the sun. I was comparing it with my Pentax XW 5mm. I noticed in the XO only that there was a soft round dark spot directly in the middle about half the diameter of the field of view though my eye wasn't close enough to get the entire field. I didn't notice it in the XW. I am using a Tec 160FL refractor so it isn't a central obstruction. I tried many other EP's and didn't notice the same. Does anyone know what this is. I looked at the moon yesterday and don't recall seeing it and I may try again tonight. I was using a Baader Herschel Wedge for the sun. Thanks, Kent
Posted 20 November 2012 - 09:51 PM
Posted 20 November 2012 - 10:01 PM
Posted 20 November 2012 - 10:02 PM
Posted 21 November 2012 - 11:34 PM
Posted 22 November 2012 - 01:34 PM
Diagram of the lens third item in Bill P's write-up on the 5mm XO:
Bill P on the 5mm XO
Posted 22 November 2012 - 03:21 PM
Take a look at this thread, then perform the same test and see if you see a darker area in the middle. FYI, I do not with my XO.
If you look into the eyepiece and do not see any spots on any of the lenses, then another thing to check is if there is any spot or grain of grit anyplace within your diagonal/wedge. Maybe there is a small grain of dirt just in the wrong spot. Since many eyepieces, when placed in a focuser, do not always align precisely the same, it is easy enough for one eyepiece not to have a small piece of grit on the diagonal show, and another to have it show. It's a long shot, but gotta check everything.
Also, as George pointed out, rotate the eyepiece in the focuser. If it is eyepiece related then the spot will rotate around also.
Posted 23 November 2012 - 12:52 AM
George: I wish I could get some good seeing. I have dark skies but Jupiter is above my house and I think the seeing is not so good right now.
Posted 02 December 2012 - 11:52 PM
What I did notice however was some hazing inside the wedge below the top piece of glass. So I do not have access to it. I had a thread in the solar forum about my wedge producing smoke when I tried it for the 1st time. It no longer smokes. I guess something was burned off but I wonder if this hazing is a result of the smoke. I will try to find out on the solar forum if anyone sees a haze in their wedge. It doesn't look like I could clean it myself so I will have to decide what to do if the haze is a problem.
Posted 03 December 2012 - 12:37 AM