shams42
Pooh-Bah
Reged: 01/05/09
Loc: Kingsport, TN
|
what is causing this glare in my view?
#3330863 - 09/13/09 01:23 AM Attachment (180 downloads)
|
Edit
|
Reply
|
Quote |
Quick Reply
|
|
|
Lately, while viewing Jupiter with my 6" SCT, I've been seeing this strange circular / elliptical glare in the eyepiece. The glare intersects Jupiter and goes off to the side. I've attached a very crude pic to illustrate what I'm talking about. The gray part is the glare. As I slew the scope, moving Jupiter through the AFOV, the radius of the glare changes. By placing Jupiter in a certain part of the field of view (near the center, but not exactly), I can make the glare go away.
I have confirmed that it is not caused by the dew shield or the diagonal. The glare shows up in all of my eyepieces. I collimated the scope last night, which seemed to make the glare go away. Tonight the glare was back, though a star test indicated that the scope was still very close to perfect collimation.
What is the cause of this? Anything I can do about it?
Edited by shams42 (09/13/09 01:25 AM)
|
Eddgie
Postmaster
Reged: 02/01/06
|
Re: what is causing this glare in my view?
[Re: shams42]
#3331262 - 09/13/09 10:27 AM
|
|
Edit
|
Reply
|
Quote |
Quick Reply
|
|
|
Have not seen this before, but since it is circular and is happening with all of your eyepieces, then my best guess would be that there is a reflection off of a bright surface somewhere.
Check to see that there are no bright rings inside the central baffle. There have been some cases where people have said that they had an SCT where the inside of the baffle was not painted properly.
When you say that you illiminated the diagonal, did you do this by going straight through (eyepiece inserted directly into visual back)?
Next, do a star test. Defocus both inside and outside of focus to the point that about 15 rings are visible between the bright inner and outer ring. Check to see if all of the internal rings seem to be evenly spaced and equal in brigtness. If you see a dark or bright set of rings, this is a zone. Zones usually do NOT give this kind of symptom, but it is the only thing I can think of that would be wrong with the optics themselves that could even conceivably cause your symptom.
Also, if you have cleaned the corrector, check it with a flashlight to see if there is a residue.
And finally this. I know it might sound silly, but you never know with such a strange symptom... Try your other eye. Sometimes your eye can do funny things. I am surprised by how many people overlook this. It took me years to realize that while I am right handed and right eye dominant, my left eye actually seems to have better visual aquity and seems to be free from more serious defects.
Good luck, and be sure to let the forum know what you discover.
|
Midnight Dan
Postmaster
Reged: 01/23/08
Loc: Hilton, NY, Yellow Zone (Bortl...
|
Re: what is causing this glare in my view?
[Re: Eddgie]
#3331284 - 09/13/09 10:43 AM
|
|
Edit
|
Reply
|
Quote |
Quick Reply
|
|
|
Definitely seems like an internal reflection to me. How did you confirm it's not the diagonal? Did you try using an eyepiece directly in the visual back without the diagonal? Also, what's the history of this? Is it a new effect? Is the scope new/used? How long have you owned it? Did you add any new components to it like a new visual back?
-Dan
|
shams42
Pooh-Bah
Reged: 01/05/09
Loc: Kingsport, TN
|
Re: what is causing this glare in my view?
[Re: Midnight Dan]
#3331403 - 09/13/09 11:53 AM Attachment (101 downloads)
|
|
Edit
|
Reply
|
Quote |
Quick Reply
|
|
|
It's a used scope, I've had it for about 2 months. I do have a new 2" visual back and 2" to 1.25" adapter. The inside of the visual back is glossy black - I wonder if this is the cause? I will try looking tonight with the old visual back if we are fortunate enough to have a third clear night in a row.
Yes, I removed the diagonal and placed the eyepiece directly in the (new) visual back. Actually I placed the eyepiece and the adapter in the visual back to rule out the diagonal.
I haven't seen any sign of zones in the star test. I'm no expert, but the optics seem excellent on this scope. Once it is cooled down and collimated I am able to see extraordinary detail on Jupiter. I've attached a pic I made two nights ago. The view at the eyepiece was nearly this detailed during moments of still air.
Edited by shams42 (09/13/09 11:54 AM)
|
Mert
Post Laureate
Reged: 08/31/05
Loc: Spain, Pamplona
|
Re: what is causing this glare in my view?
[Re: shams42]
#3331451 - 09/13/09 12:22 PM
|
|
Edit
|
Reply
|
Quote |
Quick Reply
|
|
|
Might even be the inside of the tube that holds
the primary mirror!
I also have some problem with this but only on
bright ( very ) objects.
|
Midnight Dan
Postmaster
Reged: 01/23/08
Loc: Hilton, NY, Yellow Zone (Bortl...
|
Re: what is causing this glare in my view?
[Re: Mert]
#3331541 - 09/13/09 01:30 PM
|
|
Edit
|
Reply
|
Quote |
Quick Reply
|
|
|
The glossy black interior of the visual back is a good possibility. Seems odd that it should be glossy.
-Dan
|
MitchAlsup
Pooh-Bah
Reged: 08/31/09
|
Re: what is causing this glare in my view?
[Re: Midnight Dan]
#3331674 - 09/13/09 03:01 PM
|
|
Edit
|
Reply
|
Quote |
Quick Reply
|
|
|
A: try taking out the diagonal and using the scope the hard way. This will isolate the diagonal from the optical train in question.
B: with the eyepiece out; center your eye on the optical axis and then pan your eye around in the FoV (image plane). Anything that you can see that is neither a mirror nor blackened can cause a reflection such as the one you are describing.
|
mclewis1
Thread Killer
Reged: 02/25/06
Loc: New Brunswick, Canada
|
Re: what is causing this glare in my view?
[Re: Midnight Dan]
#3331677 - 09/13/09 03:05 PM
|
|
Edit
|
Reply
|
Quote |
Quick Reply
|
|
|
Matt, that image of Jupiter is exceptional so I think you're correct in your assessment that your scope has good optics.
The inside of the visual back is usually completely covered by the barrel of the diagonal or eyepiece or whatever is inserted in there. There may be a small area very deep on the visual back not covered but that's about it. You should be able to see this if it's present with your eye pressed up to the opening in the visual back.
You might also take a look at the inside of the baffle tube in daylight and notice the "flocking" used at the far end of it. On my C6 it appears to be a thin adhesive material applied down about 1" or so of the baffle tube. The rest of my baffle tube is flat black but this area at the top of it is indeed darker. On my scope the ends of the adhesive don't come together, there is about a 1/16" gap which believe it or not shows up in star tests as a slight bump on the outer Fresnel rings.
|
charles genovese
sage
Reged: 02/04/06
Loc: Madisonville Louisiana
|
Re: what is causing this glare in my view?
[Re: mclewis1]
#3331776 - 09/13/09 04:18 PM
|
|
Edit
|
Reply
|
Quote |
Quick Reply
|
|
|
It is a reflection from the inside of the diagonal or eyepiece or Barlow. Inside, in daylight, point the scope at a window while your in a relatively dark room and the reflection will be obvious. Flock it
|
mclewis1
Thread Killer
Reged: 02/25/06
Loc: New Brunswick, Canada
|
Re: what is causing this glare in my view?
[Re: charles genovese]
#3331799 - 09/13/09 04:39 PM
|
|
Edit
|
Reply
|
Quote |
Quick Reply
|
|
|
Considering Matt has changed eyepieces, didn't use a barlow and removed the diagonal from the scope I don't think that it's anyone of those things.
It's generally accepted that flocking a modern SCT brings very limited if any value.
|
shams42
Pooh-Bah
Reged: 01/05/09
Loc: Kingsport, TN
|
Re: what is causing this glare in my view?
[Re: mclewis1]
#3331824 - 09/13/09 04:57 PM Attachment (107 downloads)
|
|
Edit
|
Reply
|
Quote |
Quick Reply
|
|
|
Here are two pictures I took. It looks like there is a shiny area on the tube that the primary mirror rides on. I think it is shiny due to smeared grease. I would think that this would be well within the shadow of the secondary mirror though. Also, the edge of this tube (closest to the secondary) has a glossy ring around the edge -- I'm not sure why.
I really, really hope it's the 2" visual back or the 2" to 1.25" adapter.
|
shams42
Pooh-Bah
Reged: 01/05/09
Loc: Kingsport, TN
|
Re: what is causing this glare in my view?
[Re: shams42]
#3331828 - 09/13/09 04:58 PM Attachment (109 downloads)
|
|
Edit
|
Reply
|
Quote |
Quick Reply
|
|
|
Second pic:
|
mclewis1
Thread Killer
Reged: 02/25/06
Loc: New Brunswick, Canada
|
Re: what is causing this glare in my view?
[Re: shams42]
#3331856 - 09/13/09 05:11 PM
|
|
Edit
|
Reply
|
Quote |
Quick Reply
|
|
|
Matt, in your second shot you can see the "flocking" inside the baffle tube I was talking about in my earlier post. With the flash it actually appears a bit lighter than the rest of the inside of the baffle tube (this change is just one of the problems with the use of a flash inside a scope).
That brighter ring at the front edge of the baffle tube concerns me a bit. I'm going to take a peak at my C6 tonight and compare it to your images.
|
shams42
Pooh-Bah
Reged: 01/05/09
Loc: Kingsport, TN
|
Re: what is causing this glare in my view?
[Re: mclewis1]
#3331861 - 09/13/09 05:16 PM
|
|
Edit
|
Reply
|
Quote |
Quick Reply
|
|
|
Thanks Mark. Please do let me know if your C6 also has the "glossy ring."
In the meantime, we're forecast to have excellent sky conditions tonight. I've installed the old visual back. *crosses fingers*
|
shams42
Pooh-Bah
Reged: 01/05/09
Loc: Kingsport, TN
|
Re: what is causing this glare in my view?
[Re: shams42]
#3332384 - 09/13/09 10:39 PM
|
|
Edit
|
Reply
|
Quote |
Quick Reply
|
|
|
Okay, I'm just back in from observing Jupiter. The reflection is definitely coming from inside the tube. With all accessories removed, looking through the aperture in the rear cell, I could plainly see a crescent-shaped bright reflection. It was impossible to tell where exactly it was coming from, but it looked like it might have been coming from the opening of the tube.
Where do I go from here? How do I fix this?
|
Robo-bob
sage
Reged: 05/02/05
Loc: Central Alberta
|
Re: what is causing this glare in my view?
[Re: shams42]
#3332422 - 09/13/09 11:06 PM
|
|
Edit
|
Reply
|
Quote |
Quick Reply
|
|
|
I am thinking this is the reflection of something bright, in this case Jupiter, off or your eyeball and back into the eyepiece. Try rotating your head while keeping your pupil inside the exit pupil of the eyepiece. I see the same effect and have isolated it using this technique. It works well and may be a simple solution to your problem.
Good luck - Rob
|
meade8r
member
Reged: 08/24/07
Loc: Finger Lakes
|
Re: what is causing this glare in my view?
[Re: shams42]
#3333150 - 09/14/09 11:21 AM
|
|
Edit
|
Reply
|
Quote |
Quick Reply
|
|
|
This problem has been cited a number of times in the past. At least, you seem to have received more suggestions this time.
Having the same problem myself, I tested my C6 in all the configurations, including the use of various eyepieces with and without diagonals. I even tried bypassing the visual back using a diagonal adapter. I finally sent it back to Celestron. It was returned in 4 weeks. Celestron cleaned the exterior of the corrector, collimated it, and replaced the visual back.
None of this helped. I have a feeling that those of us with these scopes just "live with it" since it only seems to happen on bright objects.
If you can solve this, you will be a hero.
Charlie
|
EdKiefer
sage
Reged: 04/09/07
Loc: NY, LI, USA
|
Re: what is causing this glare in my view?
[Re: meade8r]
#3333531 - 09/14/09 03:00 PM
|
|
Edit
|
Reply
|
Quote |
Quick Reply
|
|
|
you sure its not the tip of baffle tube not being flocked to its tip, from the pic it looks real shinny at very tip where Celestron has flocked but seems its not to edge very good (its hard to say with flash as it exaggerates lighting).
Edited by EdKiefer (09/14/09 03:01 PM)
|
shams42
Pooh-Bah
Reged: 01/05/09
Loc: Kingsport, TN
|
Re: what is causing this glare in my view?
[Re: EdKiefer]
#3333566 - 09/14/09 03:23 PM
|
|
Edit
|
Reply
|
Quote |
Quick Reply
|
|
|
Yes, that tip (particularly the inside) is very shiny. It isn't just an artifact of the flash. I might try applying a small ring of flocking paper there and see what happens.
|
PHampson
sage
Reged: 10/25/05
Loc: Nashville, TN
|
Re: what is causing this glare in my view?
[Re: shams42]
#3334858 - 09/15/09 09:39 AM
|
|
Edit
|
Reply
|
Quote |
Quick Reply
|
|
|
My C6 had the same thing. I believe it is a reflection off of the inside of the primary baffle tube. Someone already mentioned the insert they put into the end of the baffle nearest the secondary mirror. It's effective in stopping reflections from the extreme end of that tube but the problem is that it's too short. That leaves a small portion just underneath it that's still 'glossy' when viewed from an angle. I repainted that small 'ring' flat black and roughed it up a bit. It didn't eliminate the problem but it did help. I now only see the reflections on extremely bright objects in the periphery of the field of view. Someday I may open the OTA up and try to eliminate it altogether but, for now, I'm OK with it. Good luck.
Paul
|
Previous
Index
Next
Threaded
