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Old 16-06-2014, 08:28 PM
samgibbs (Sam)
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The Eyes Have it All?

Greetings to fellow forum members......my first post here.

I am a specialist in organizing science and astronomy outreach programs. I frequently conduct sessions under the stars using a comprehensive suite of telescopes and imaging systems.
Recently i have discovered that my 50ish eyesight has been adversely affecting my ability to focus the eyepieces i use for my astronomy sessions. Previously this was never a problem but now I have this constant nagging concern about finding best focus for my participants....... To add to my woe i have tried to encourage the participants, most of whom have never used a telescope in their lives, to focus for their own best perception. This has often ended in strange results and wildly out of focus images.
I am curious to know if there are any solutions out there for a person in my predicament. One thing i have found is that taking pics with my smart phone using eyepiece projection has helped with lunar observations. But for planets its no good to me at all. ALso i have noticed that the effect seems to be less with higher powered eyepieces.
Input and suggestions appreciated.
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Old 16-06-2014, 09:02 PM
brian nordstrom (As avatar)
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Sam , it's so great to hear you are out there teaching people the joy of the night sky , really good stuff .
On the focusing thing yes you have to giggle when someone new is enjoying a look at an out of focus Jupiter or Saturn and the wonder when they see it in focus for the first time makes it all worth while , I love it .

On the eyes , cant help there , but keep at it Sam and welcome again old mate .

Brian.
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Old 16-06-2014, 11:05 PM
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Asterix2020 (Paul)
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Sam,
You need to wear your distance prescription. Even if you think you don't need it for day to day two eyed vision, you are probably slightly longsighted (don't confuse this with presbyopia, needing reading glasses due to the eye's loss of focussing ability). You need to get a set of distance glasses made up and the focus through them. The telescope will now be focused for someone that doesn't need glasses. You are compensating for your eye's refractive error with the telescope focuser, which is fine if you're the only one using it
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Old 17-06-2014, 04:18 AM
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JB80 (Jarrod)
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Hi Sam,

I echo the sentiment that it's great you are out spreading the joy of astronomy with others. Keep up the good work.

The only thing I can think of that may help with focus is to maybe look into getting a Bahtinov mask. They can be either brought commercially or there are a number of websites that can generate a template to make one yourself out of some card or other material.

They are in general designed for focussing on a star but once you have the correct focus on a star once you swing to a planet they are generally pretty close to the same focus.
I think it would be acceptable for visual observing anyway.

http://astrojargon.net/maskgen.aspx?...ookieSupport=1

http://en.wikipedia.org/wiki/Bahtinov_mask

I hope that is of some help to you
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Old 17-06-2014, 06:56 AM
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Hmmm, the way i see it, each individual has their own focusing needs and therefore one person focusing so another can look is not really going to work that great.

Sam, in regard to your self focusing on any object, moving the focusing control to suit your needs is what it is all about.

If your eyes are not as good as they used to be, (like mine) then one would move the focusing control to suit those old eyes.

I am half blind too, but still can get a clear image suited to my eye condition, when i used to do imaging, i used to take off my glasses, focus to as sharp as possible and all would be fine, but when i looked down that tube with my glasses on it would be very blurry.

Leon
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Old 17-06-2014, 12:39 PM
PeterHA (Peter)
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Not alone but uncle Al helped us

Sam,
You are not alone, many of us with astigmatism end up not being able to focus with EPs whenever the exit pupil is above a certain size, in my case 0.8 mm.
But there is help, Al Nagler gave us the DELOS range of eyepieces and they work with glasses and the Explore Scientific 24mm 68 degree does as well.
So from 24 down to 3.5mm there are EPs available which all allow full fiew of the field with spectacles.
You could change to seese, focus with you glasses and it would be in focus for you clients.
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Old 18-06-2014, 02:15 PM
samgibbs (Sam)
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Hello to all the members who have kindly contributed to this thread.. Thanks Brian for you welcome. I was delighted to find this "nebula of astronomy" recently.
My thanks to all those who have contributed suggestions. I like the idea of the mask and will give this a try to begin. I actually saw one at a colleagues astronomy store recently. It piqued my interest immediately. From my side i have learnt to defocus easy targets like the moon to a certain extent but the technique lacks precision. I look forward to following up with my experiments with masking.
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Old 18-06-2014, 02:24 PM
samgibbs (Sam)
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Uncle Al

Nagler Delos
I am interested in this as part of the problem also remains that many of the people i have at my outreach and stargazing sessions wear glasses too. Maybe some other forum members could also back up there experiences with Delos eyepieces before i throw cash at the problem.
Thanks Peter for your suggestion here. Already this thread has been very helpful.
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Old 18-06-2014, 02:38 PM
casstony
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Delos are very high quality eyepieces and excellent for observing with or without glasses.

For personal use you might consider binoviewing. I've just hit 50 too and I find binoviewers make it easier to pick out fine details. They take a little getting familiar with at first, but I find observing both eyes substantially compensates for problems of ageing.
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Old 18-06-2014, 04:10 PM
Wavytone
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Quote:
Originally Posted by samgibbs View Post
Recently i have discovered that my 50ish eyesight has been adversely affecting my ability to focus the eyepieces i use for my astronomy sessions.
Sam, you have passed the age where you need either contact lenses, or specs. The lens in your eye continues to grow, and after about age 45 the lens is so thick and stiff your eye muscles can no longer focus it. If you have slight myopia or hypermetropia (short or long sightedness) this won't trouble you during the day when your pupil is small (1-2 mm in bright light, means your eye is working at f/10-f/15 which is very tolerant of small optics defects), but at night your pupil opens up to 5 mm or more and at f/3, any defocus due to myopia or hypermetropia will be very evident. When you focus a scope, the eyepiece position that suits you clearly doesn't suit most others.

Alternatively, if both eyes are good, you could have laser surgery to correct one eye for long distance (i.e. infinity) and use that for focussing telescopes.

FWIW I am 57 and have always been quite long-sighted, and wear specs to correct this - I will won't switch to contacts let alone resort to laser surgery for various reasons.

If you are at the telescope where you will share with others the trick is (a) buy long eye-relief eyepieces (20mm or more is needed) so you can wear your specs and see through the eyepiece, and (b) while wearing your specs, set the focus. This will be the correct "infinity" focus for other people.

As for long-eye-relief eyepieces there are several series that offer 20mm or so across the whole range from short to long focal lengths. Ultra wide eyepieces (>68 degrees aFoV) are useless in this situation so settle for around 65 degree fields of view.

Premium: Televue Delos or Panoptics above 27mm;
Mid range: Vixen LVW, Baader Hyperion (inferior to LVW);
Cheap: Vixen LV (obsolete but superb if you can find a set), Vixen NLV, SLV (not plossl), Orion Stratus or Edge-On.

The extreme wide-angle designs like the Ethos or the ES eyepieces all have very short eye relief and are not suited to wearing specs.

FWIW I have a set of Vixen LVW's for the above reason, and some time ago sold a set of Vixen LV's (regrettably) as IMHO the LV's were superb.

Last edited by Wavytone; 18-06-2014 at 04:22 PM.
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Old 18-06-2014, 04:55 PM
N1 (Mirko)
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Totally agree with leon. I've done a bit of observing with people who were completely unfamiliar with telescopes, and none of them had trouble using the focuser after an introduction that took, what, 5 seconds? "Everybody is different. Turn here to focus. You'll see when it's sharp". I make sure I use the word "sharp". The hard part is usually finding the EP in the dark. Using the focuser gives a better feel for the instrument, plus it illustrates why it's best not touched once observing is underway. Also I never assume my focus settings will suit any other person. FAIK, they, or I, may need glasses but don't know it yet.
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