loosening filter retaining ring
Posted 31 January 2013 - 10:00 AM
Seems the retaining ring is a bit tight and I would like to loosen it and see if things improve. But it doesn't want to move and I don't have a filter ring removal tool.
Any ideas on how to loosen this?
on the other hand maybe even if loosened it would still be astigmatic. now I regret not getting a Baader or Astrodon or something....
Posted 31 January 2013 - 10:27 AM
Also check your kitchen; I have a tool that is plastic-coated that is used to open jars, etc. This works very well with filters!
Posted 31 January 2013 - 10:31 AM
In any event, if you have an extra pair if hands available, one could support the filter cell while the other rotates the retaining ring using a pair of jeweler's screwdriver tips. Use the largest ones which will fit in the slots. The cell supporter should strive to not pinch or otherwise asymmetrically squeeze; try to exert uniform force.
It goes without saying that care is required!
Posted 31 January 2013 - 10:36 AM
Use a piece of the "rubberized" shelf liner to grab hold of the filter. This will give you a better grip on it. Also check your kitchen; I have a tool that is plastic-coated that is used to open jars, etc. This works very well with filters!
It's not that he can't get the filter off whatever it's attached to, he wants to remove the retaining ring that holds the filter element in the filter cell. The only safe way to do this is with a spanner wrench. I had the same problem last year and wound up getting a set of these Adjustable-Arm Spanner Wrenches. Problem solved. I've since used them for a lot of other optical projects that would have otherwise been impossible. Here's another set from Edmund Optics. Please notice that the company is EDMUND and not EDMUNDS as is a common mistake on CN. Edmunds is, in fact, a company, but it has absolutely nothing to do with optics!
Posted 31 January 2013 - 10:43 AM
Hey, some good came out of my booboo; your link to the spanning wrenches.
Posted 31 January 2013 - 01:49 PM
Posted 31 January 2013 - 03:19 PM
Sigapore is the camera captial. Go to any camera shop with a service department and I'm sure they will help you (most likely for free). They usually have a ton of spanner wrenches to fix lens (if you liked one buy it).
Posted 01 February 2013 - 07:40 AM
I got sick of ruining things so I bought a jewlers Spanner wrench, best $40.00 I ever spent, i use it all the time, no more ripped up retaining rings or scratched/ruined lenses.
Posted 01 February 2013 - 10:42 AM
Loosened it nicely. Hope the astigmatism goes away. Otherwise its a hundred bucks down the toilet. Even at best focus the stars weren't round that DeepSkyStacker had trouble registering the subs.
EDIT: well, the filter retaining ring is nice and loose. Still got astigmatism.
since I bought it used... (I knew there was something wrong if a 2" 10nm H-A filter was going for a hundred bucks) i don't have much recourse. the seller said it worked fine on his SCT... but then SCT's have so much coma and field curvature it's likely these would have masked the astigmatism.
that, or imperfect tracking. that would also embiggen the stars and conceal the astigmatism.
oh well. should not have cheaped out. These deals always get me in the end.....
Posted 02 February 2013 - 12:43 PM
Another test; place it in front of a bino or small refractor, and examine any suitable land or sky target. If the aperture is larger than the filter's aperture, simply mask of the outer annulus of unfiltered objective. This is a sensitive test, for it uses the full aperture. The magnification need not be high.
For me this poses a fascinating problem, for which I would strive to divine the fault.