Re: [William Optics] Re: Megrez 110ED Focuser Align. Do I need it?
This comment doesn't help me. I know that Megrez is not at the level of well known out performer n x 1000 $ OTAs.
It is not possible to send it back because warranty has expired and it is not possible to buy a more expensive scope because budget.
Star test is ok (many diffraction rings, intra and extra focal image is round), so lens are well collimated and I know that the issue is only concerning the focuser.
I would like to know if anyone has attempted any kind of fine tuning of the focuser and the procedure he followed in order to avoid any breaks (my version is the last one, with the white focuser, I think the same of the last Megrez 90).
Is there anyone that have any idea on my issue?
Help is really appreciated.
--- On Fri, 7/30/10, Perry Holcomb <hpholcomb@...> wrote:
From: Perry Holcomb <hpholcomb@...>
Subject: Re: [William Optics] Re: Megrez 110ED Focuser Align. Do I need it?
Date: Friday, July 30, 2010, 5:04 PM
I had a M110. Stock focuser was poor. For AP, I would have had to upgrade. For an ED, it wasn't worth the investment. Finally sold the scope.
It's been stated several times on this group that the WO stock focuser, upgrades not included, is the poorest element in an otherwise fine instrument.
--- On Fri, 7/30/10, DianeBWorth <dianesails@sbcgloba l.net> wrote:
From: DianeBWorth <dianesails@sbcgloba l.net>
Subject: [William Optics] Re: Megrez 110ED Focuser Align. Do I need it?
To: William-Optics@ yahoogroups. com
Date: Friday, July 30, 2010, 12:26 PM
Call first then return to the WO dealer - WO 2-yr warranty
What happens when you rotate the camera to different positions? It is my understanding that even if everything else is perfect, ccd cameras can still have ADU counts varying by several hundred around the frame. I never noticed any focuser related problems with my M110. The main problem was CA which I eliminated with a IR-UV cut filter and some post processing. The other problem was elongated stars and vignetting in the corners which since I had a large formate camera, I could easily crop out. I consider the scope a great value for the money, but it does have a learning curve.
--- In William-Optics@yahoogroups.com, "DianeBWorth" <dianesails@...> wrote:
> Call first then return to the WO dealer - WO 2-yr warranty
> --- In William-Optics@yahoogroups.com, "gmst83" <gmst83@> wrote:
> > Hi all,
> > I spent many days looking for information about the focuser of my William Optics Megrez 110ED, but none reply to my question.
> > I noticed things listed below.
> > 1. When I put a laser collimation tool on the focuser and rotate it, the dot light that I projected on a squared panel in front of the tube describes "circles" around what should be the geometric center of the lens. This circles has a diameter of ca 2 cm when the the panel is at the distance (from the lens surface) almost equal of the dew shield fully extracted (ca 20 cm).
> > 2. The master flat field (obtained by CCDSoft and using my CCD SBIG ST8300M) is, we can say, really not cylindrically symmetric. What I means is that ADU I can measure on the down right corner (average of 11000 ADU) is very different on what i can measure on the top left corner (10600 ADU). Other corners ADU is in the middle. Further more, if I analyse the ADU along the vertical axis of the image (passing in the center, so where most light it should be) I found that at the centre I found the top of ADU then walking to a side of the image, ADU decrease to a minimum the increase again close to the side. I tried with another sensor (Canon EoS 400D) and obtain the same behavior.
> > 3. The master flat field have the max of ADU shifted on the right of the geometrical center of the image by 200/300 pixels.
> > 4. It seams to me that the radial elongation of the stars appear different on each corner of the image.
> > So, now my questions to the group.
> > Is it possible the light coming from the lens is not squared to the CCD, due to (for example) to a misaligned focuser?
> > If yes, how can I fix this?
> > Or, am I too severe expecting too much "cylindrical symmetry" from my OTA?
> > I hope someone could help me.
> > Clear skies.
> > Giorgio
- Perhaps when you insert the camera and move the lock-screw, the retaining ring inside the focuser can't maintain the sensor on-axis. You will find a hole near the border of the focuser, just opposite the lock-screw; there's a screw inside, perhaps it's too loose and the ring has some play around the camera adapter. Lock it a bit.
P.s.: do it at your own risk...