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ES AR152 Spikes/Flaring at Low Power

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#1 Mike4242

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Posted 15 June 2013 - 08:52 AM

When using my 24mm ES 82° and 38mm Orion Q70 eyepieces with my AR152 brighter stars and planets have kind of a flaring affect. It looks like spikes coming off of one side of the star or planet. Actually, last night Saturn seemed to have kind of a stretched out ghost image extending from one side in the 24mm. The problem is worse in the 38mm than the 24mm. My 18mm ES 82 doesn't show this, nor do any other shorter focal length eyepieces -- only my 2 lowest power ones. The spikes/flaring seems to be sensitive to where I have my eye placed. If I move my head around it moves to different sides. Also, adjusting the focuser makes the spikes/flairing longer or shorter. I haven't really noticed this so much in my Dob -- maybe a little with the 38mm, but I just assumed it was coma. I was wondering if anybody here has ever seen this before? Is my scope exhibiting some sort of aberration or is it the eyepieces? It doesn't seem likely that 2 different eyepiece brands and designs would exhibit the exact same aberration. Being that it moves around if I move my head suggests it could be my eye. Not sure. The scope's collimation seems to be good when doing a star test.

#2 Kon Dealer

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Posted 15 June 2013 - 08:55 AM

I have the same problem at low powers. It's a real bummer.
Anything under x20 in any scope. I think it is my eyes too.

#3 Mentor

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Posted 15 June 2013 - 09:14 AM

The exit pupil in the 24mm is about 3.7mm, and the 38mm is 5.8mm.

It is possible that these larger exit pupils are bringing your own eye's aberrations into play. Our eyes tend to have lots of issues in the outer limits of the dilated pupil. A 3.7mm exit pupil is rather small for this, but I do agree that if it is sensitive to your eye position and orientation then this is the most likely cause.

Do you notice this when using similar exit pupils in your other scopes? Low power, wide field eyepieces will also expose your scope's inherent optical issues.

#4 Cotts

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Posted 15 June 2013 - 10:08 AM

Sounds to me like your eye's astigmatism comes into play when there is a larger exit pupil. This is common - everyone has at least a bit of astigmatism. You may wish to look for the results of your most recent eye exam to find out the level of astigmatism that you have - check with your optometrist.... You'll need the diopter number for your astigmatism. The cylinder angle is unimportant as is your near/farsightedness diopter.

Because there may be a cure for your problem. It depends on your eyepieces.

Dioptrix by Televue

I have the same problem with my 16" dob when using the 31mm Nagler - severe spiking of stars across the field. Attach the Dioptrix, rotate it and, magically, pinpoint stars! And they're only about $100. I leave it on there all the time. They are sold in specific diopter strengths which you match to your diopter.

The Dioptrix only fits on certain eyepieces outside of the Televue line so you'd best contact Televue to see if yours 'qualify'.

You will be very happy with the results...

Dave

#5 Jon Isaacs

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Posted 15 June 2013 - 10:14 AM

It does sound like astigmatism in your eye. The test is to rotate your head and see if the spikes rotate. If they do, its your eye.

I just live with, it goes away at smaller exit pupils.

Jon

#6 Binojunky

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Posted 15 June 2013 - 11:02 AM

Not a bad idea to get an eye check, I had similar issues a few years back, also large floaters, my annual check up discovered a tear in my left retina, a very small one in my right eye,and the early symptons of glaucoma.
At the risk of sounding a bore, it never ceases to amaze me what some people will spend on star gazing gear yet gag at the thought of paying for an eye exam, DA.

#7 Mike4242

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Posted 15 June 2013 - 12:06 PM

Thanks for the responses. I have my eyes checked once per year and I do have an astigmatism which is why I can see better with glasses than contact lens. I still wear contact lenses most of the time, but my optometrist says the contacts don't correct for the astigmatism like glasses. Also, my astigmatism isn't severe enough to justify the cost of the special contact lenses.

Dave, Thanks for the link! I may look into one of those.

I'm going to take out my Omni 102 and Dob tonight and see if I get the same results. It's kind of hard to tell in the Dob because I only have the problem on bright stars and they have diffraction spikes.

#8 kew

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Posted 15 June 2013 - 10:27 PM

I also see flaring on bright stars at low mag. The aberrations I see do change with eye placement. I have been considering Televue's Dioptrix....

#9 PowellAstro

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Posted 16 June 2013 - 01:30 PM

I had issues like that in mine at first. Found the optics had rotated during shipping and was causing a small amount of wedge effect between the elements. I spent some time correcting this as well as corrected the SA I saw in the lens while I had it out. This scope really performs great now. See attached image I shot last night.

High Res Image At: http://www.digitalp....ry2/ar152_1.htm

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#10 meteorite

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Posted 16 June 2013 - 02:21 PM

I see this as well at higher exit pupils on brighter stars. It is astigmatism in my eyes. Lower exit pupil and/or dimmer stars = pinpoints.

Does any one know if the dioptrix works with any of the Explore Scientific 82 degree eyepieces?

#11 SteveG

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Posted 16 June 2013 - 02:58 PM

I see this as well at higher exit pupils on brighter stars. It is astigmatism in my eyes. Lower exit pupil and/or dimmer stars = pinpoints.

Does any one know if the dioptrix works with any of the Explore Scientific 82 degree eyepieces?


I can't speak to the 82's, but it will fit the 28 mm 68 deg. I'm doubtful it will work with the 82's because you need extra eye relief to use the Dioptrx. Televue sells an adaptor to use the Dioptrx with their type 6's, but you won't be able to see the entire f.o.v.

I've tried several low-power eyepieces for use with Dioptrx. The 27 or higher Panoptics are perfect due to their long eye relief. The 24 Pan eye relief is too short and not usable in my opinion. The 22 Pan is also great with Dioptrx. I've recently settled in with a 22 T4 Nagler, which is fantastic when used with a Paracorr in fast newtonians. I hated the Instadjust, so I figured out a way to defeat it and have it locked in a lowered position.

#12 T1R2

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Posted 16 June 2013 - 04:07 PM

Hi, can you tell me if the retaining ring that holds the lens in place is in the front or back of the cell, I had the same prob. and sent mine in to have it adj., but I would like to be able do it myself if ever needed, I have the tools, but the ring that I thought it was is the one on the front of the cell, I could see the threads, but was so tight I could not get it to come off. just wanted to make sure I trying to take off the right one.

#13 Jon Isaacs

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Posted 16 June 2013 - 05:50 PM

Thanks for the responses. I have my eyes checked once per year and I do have an astigmatism which is why I can see better with glasses than contact lens. I still wear contact lenses most of the time, but my optometrist says the contacts don't correct for the astigmatism like glasses. Also, my astigmatism isn't severe enough to justify the cost of the special contact lenses.



An eye check is unlikely to catch this because a viewing star at exit pupils is probably as severe a test as there is for astigmatism. Your eye is open wide working at a focal ratio of about F/2.4 (17mm focal length, 7mm aperture) so there is very little depth of focus and you are using the entire lens.

The fact that you have some uncorrected astigmatism is a good sign that this is the issue.

Rotating your head and observing whether the spikes rotate or stay fixed is the traditional test that amateur astronomers use to determine the aberration is in the system or in the observer's eye.

Typically, if it's in telescope, it gets worse at small exit pupils/higher magnifications and is not visible at large exit pupils/low magnifications. If it's your eye, it is most apparent at large exit pupils and it lessens at the magnification is increased.

Jon

#14 PowellAstro

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Posted 16 June 2013 - 09:16 PM

I would think they are all the same and mine was in the front. There is a large black rubber o-ring under the retaining ring which grabs the ring very tight as well as the top lens with only very little pressure on the retainer. I had my cell out and on the bench before I loosened the retaining ring. NOTE: there are also three allen set screws around the lens holder that must be unscrewed before you can turn the retaining ring. These are there to lock the ring once it is in place.

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#15 T1R2

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Posted 17 June 2013 - 03:57 AM

Mike, I would check to see if your lenses edges are lined up, use a toilet paper roll and lower the whole lens cell down,be sure to cover the cardboard roll with a few layers of tpaper and use a rubber band to hold it down the paper roll will lift the lenses out, jiggle it a little you don't have to do anything but look around the edges to see if the chalk lines are lined up, then after you make the adj. raise the cell back up the roll onto the lenses and all the way off, set it on the table and rubber ring and retaining rind back on, If you haven't done this before do some research, or have some one who have assist you. I checked mine just now and they were off by about 1.5 in, even after I sent it to ES to have it adj. next clear night I'll know if it worked.

#16 Mike4242

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Posted 17 June 2013 - 03:24 PM

Thanks again for the responses. Unfortunately I haven't had a chance to get back out with my other scopes yet to see if I can replicate the issue. If I can reproduce the same result at similar exit pupils in different scopes, then I guess I'll chalk it up to eye astigmatism which seems to be the most likely culprit.

I'm not super comfortable disassembling the lens cell myself since I've never done it before, so I may contact ES and see what they recommend if I determine that it's a problem with the scope.

#17 PowellAstro

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Posted 17 June 2013 - 04:35 PM

@ Mike,

How are your views of Saturn in the AR152 around 150x? Are they razor sharp in the AR? Do you get any color or haze around the planet?

#18 Mike4242

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Posted 17 June 2013 - 06:47 PM

I've been getting fairly sharp views of Saturn all the way up to 250x lately -- Cassini division is sharp and distinct. If I remove the Baader Fringe killer, there is a little bit of purple haze at higher magnifications.

#19 Mike4242

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Posted 17 June 2013 - 07:13 PM

I'm no artist, but this is a general representation of what I'm seeing -- much smaller of course and only on bright stars. Notice there are generally 3 spikes with the middle one being longer than the outer 2 spikes.

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#20 PowellAstro

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Posted 17 June 2013 - 07:30 PM

That is strange because it would seem your eye would show only one direction. If it was your scope Saturn would not look sharp at 150. Can you make the flare move around the star by changing your eye position?

#21 Mike4242

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Posted 17 June 2013 - 07:32 PM

Can you make the flare move around the star by changing your eye position?


Yes. If I move my head around the spikes will move around to different sides.

#22 Mentor

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Posted 17 June 2013 - 07:50 PM

Try your other eye. Often our eye aberrations have bilateral symmetry, so you may see the same effect oriented in the other direction in your other eye. The magnitude of the aberrations may be different in each eye.

#23 Mike4242

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Posted 17 June 2013 - 08:40 PM

Thanks for the tip Ian. I'll try that...if the clouds will ever clear out. :cloudy:

#24 PowellAstro

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Posted 17 June 2013 - 08:48 PM

@ T1R2

Did you happen to check the thickness of your lens shims when you had it apart? I would like to know their thickness if you happened to check them.

Thanks

#25 T1R2

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Posted 17 June 2013 - 09:04 PM

No sorry, I did look at them but they seemed to look normal, I was more concerned with the index marks and I can only hope they are right, I've read that sometimes there wrong also I have no way to measure them, probably be getting some calipers soon






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