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  #41  
Old 20-11-2011, 06:23 AM
astrospotter (Mark)
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On learning about your own eyes

Some years back in doing some reading on averted vision and following a few links on the web I became aware of the veins we all have on the back of our eyes naturally lead to 'sweet spots' that may vary in each individual to some extent. For averted of course the rods are great for low level light and are the most dense away from the central vision as we know.

So to better understand where my averted vision sweet spots were I found that in the eyepiece go to some starfield that is not very populated (not in the milky way for example) and find an area that has a star or two that are at the very limits of your perception in averted vision.

Now move your eyes relative to that tiny dot and you will fine that the star disappears and re-appears. Try to note the fraction of the field of view and if you are for example looking 'up and to the right 1/6 fov' for example for the very best and widest sweet spot. (I am a right-eyed observer).

You will find sweet spots in different places. It is well worth the time and from time to time I refresh my memory as to where they are. I tend to favor about 3 of them (sometimes below object as well so try all over the place but of course away from the object just a bit)

Too far away and of course averted looses it's ability to form an image, too close and you loose it entirely (The star starts to image on your central eye which means the image is on higher and higher density of cones that are lousy for dim light)

One really nice and detailed discussion of the effect of cones/rods is here
http://www.telescope-optics.net/eye_...l_response.htm

So learn about your observing eye(s). It will pay off to be sure.

For extreme challange objects I first identify the field and set my big dob to track. (if you cannot track then just sit near your scope and take a few seconds a couple times a minute to push your scope to the field while doing the next bit. Next I cover my entire head in a dark blanket for 10 minutes and hope nobody comes by to make fun of me ...
Then I find you will have that extra edge that is sometimes required for extremely dim objects. While viewing I wrap the light/dark blanket that is over my head already around the eyepiece so that my mouth has an open area and I don't breath into this tiny cone I have formed to see the eyepiece.

This may sound very funny but I can assure you it works and is sometimes even required for extremely dim objects.
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  #42  
Old 25-05-2012, 01:43 PM
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mental4astro (Alexander)
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Blinking for planetaries

Hi all,

I had a marvelous experience a month ago to do with "blinking".

Blinking is a technique where you look for an object by switching between a neat image through the EP and then switch to a view with a filter, and back and forth, and so one. This technique is useful for finding very tiny DSO's that on their own are drowned out by the surrounding stars or background skyglow. Planetary nebulae respond very well to Blinking using an OIII filter.

Our mate erick showed me his DIY Blinking paddle. It is a $1 plastic paint spatula with a hole drilled in it and an OIII filter threaded into it. The spatula is also painted matt black. Such a marvelously simple and effective tool! Blinking is such an easy task as you hold the paddle in one hand and flick the filter between your eye and the eyepiece as needed.

I'm hoping to make a little paddle for myself now after a clumsy but successful blinking session to find one of the three planetary nebulae that lie within the boundaries of the giant open cluster M7 three nights ago. Clumsy as I had to hold the OIII filter between my fat fingers making the blinking process rather trying. Still, I managed to track down on of them.

Eric, thanks for showing me the paddle! Great and effective tool that is sooooo simple to make, . As soon as I make mine I'll post a picture of it, unless eric beats me to it.

By the way, Blinking was the method used to discover Pluto back in 1930. Then, the blinking process was done by switching between two photos taken a few days apart of the same patch of sky time and time again to spot a tiny 'dot' that had moved between each of the exposures.
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  #43  
Old 27-05-2012, 04:55 PM
gary
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Go to larger aprture, then go back to smaller aperture

If observing with a group and the object you are trying to locate is proving challenging,
if a friend in the group has a larger aperture scope, offer them a Tim Tam and
ask them when they have a moment if they could please dial up the object and point their scope to it.

Once you see it in a larger aperture, sometimes when you go back to a more
modest aperture, it suddenly "pops out" and becomes self evident.

I have sometimes been flabbergasted that an object that requires a reasonably
experienced eye in say a 20" may suddenly also become observable in an 8"
simply because you now know what to look for.

We have all done this from time to time. It is such an obvious tip and for that
reason was probably overlooked on this thread.

If you are observing alone or if you have the biggest scope on the field, then Plan B
is to use the other valuable tips that appear on this thread.
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  #44  
Old 08-06-2012, 08:28 PM
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Varangian (John)
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Might be stating the obvious here but my biggest lesson was learning to use my non-preferred eye. My natural sighter is my right eye, I use it to wink, site a rifle, it is my primary seeing eye when I'm talking to someone and it was my natural ep eye when I first started observational viewing, but it's not my best eye. I have been told it's 18/20 due to some metal that got lodged in it when I was 21, the metal had to be scraped out with a scalpel and it has never been the same. My left eye is 20/20 and I use this eye for all my viewing, even if it doesn't come naturally and still feels uncomfortable after extended viewing. The problem with using my secondary eye is that while it might provide clearer vision it was much weaker than my primary eye, so I needed to train it and develop it. My first reaction is still to look in any ep with my right eye, but it's important to know your best eye, or pick your best eye for the best results.

Strange but true.
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  #45  
Old 09-06-2012, 12:56 PM
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Use a dark hood

When observing galaxies, I find using a dark hood draped over my head works wonders. It eliminates all stray light that may be reflecting off the eyepiece lens and removes the need to cup your face with your hands in an attempt to shield your eyes from surrounding light pollution. It does really enhance the visibility of faint objects. Only issue I've found is that the eyepiece tends to fog up easily, as your body heat is sort of "trapped" under the hood.
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  #46  
Old 10-06-2012, 05:45 PM
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mental4astro (Alexander)
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Gary, so true about seeing as much with a smaller aperture as with a larger. I've notice that in switching between my own scopes. Sometimes the only difference is just subtle texture.

John, I have a preference for my right eye, but some nights I find I'm using my left. Not a conscience decision either. Just happens . And it's difficult to swap mid-session too.

Sab, I've tried the cloak too, but the problem of fogging killed that. Heating the eyepiece is an option, but the density of H20 in our breath overcomes this too. I can only cup my observing eye, trying to keep my nose out of the cocoon to reduce the amount of exhaled breath that enters.

Well, I've finished this PN Blinking Paddle. I used a piece of MDF I had left over from making a couple of bullroarers for my son, hence its shape. Turns out to be just fine for my purposes - long enough to just need a small flick of the wrist to move it into and out of place, and its ovoid shape good to accomodate the shape of one's face. Its thin profile will help deal with eyerelief distance. I'm not sure if to paint it or not. At most I may just give it a once over with some acrylic paint as I don't want paint fumes in my eyepiece case.
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  #47  
Old 12-06-2012, 09:42 PM
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Paddy (Patrick)
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Very interesting John. I also use the eye that I am less likely to use for other purposes, but still find switching from eye to eye useful at the eyepiece. Like you Alex at present I find a cloak makes my ep fog up so I cup my hands around the ep. I found Sab'a suggestion does make quite a difference. Maybe a mini-cloak just over the ep and not my nose might work. Like the blinking paddle too.
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  #48  
Old 06-07-2012, 05:19 PM
astrospotter (Mark)
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Observing cloak and breathing vapor

I am sold on use of the cloak for limit objects. I allow the cloak to cover head but keep my mouth and noise exposed to air by careful adjustment of cloak all about the eye but allowing the mouth to be breathing if not to open air at least to an area of the cloak that is not going to leak much into the eyepiece area. Have to hold the cloak for this sort of approach. I think you could make some odd cyborg sort of full head hat that covers one eye like the borg in Star Trek but perhaps that is taking things a bit far ...

I also use a heated eyepiece in 'dew season' as I find just the heat off of the face/eye can fog an eyepiece when it's real cold.
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  #49  
Old 16-11-2014, 08:28 PM
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mental4astro (Alexander)
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Thought I'd share some of my thoughts, experiences and new practical techniques I've adopted in the last couple of years. Some I've adopted from fellow astro nuts, others I've modified with experience, others have come about just from trial and error.

Observing from light polluted areas
While aperture is King, under urban skies this is not necessarily the case. In many instances it can actually be counterproductive. I've found that using big apertures also increases the effects of light pollution. These days, when I observe from my home in Sydney, I opt for smaller apertures, 4" to 12". I just don't bother with my 17.5" dob from home as the sky glow just overwhelms everything else. If anything, I tend to prefer my smallest of apertures and enjoy low power wide field viewing - light pollution has significant less affects. The comet Lovejoy inparticular showed me the 'power' of smaller apertures over large from urban areas. My 11X70 binos do well from home too. Otherwise I mainly focuse my home-based viewing to the Moon and planets.

Eyepieces and dew
Little ruins a good night's viewing like dew. My original counter-measure to dew was to attach a heating strip around the eyepiece at the focuser. In the end this really did not work for several reasons: a, focuser was very cold, so any heat the dew heater could put into the EP, the metal focuser sucked out straight away, and dew wasn't challenged, b, the sheer bulk of some EPs, like my 1kg 30mm toe crusher, there is no way a dew heating strip could do to deliver any substantial heat into a cold EP to prevent dewing.

The solution I read about by chance one day - heated eyepiece case. If the heat is in the eyepiece from the start, the heating strip is then effective in maintaining a warmer situation for the EP, rather than a futile attempt to introduce heat.

MY solution however is a take on the heated eyepiece case - a hot water bottle in a cosy! I put the hot water bottle inside my eyepiece case, and a couple of towels (that I already have in the car from protecting some gear during transport) over the lot for insulation. This gives me at least 6 hours of heat during very cold nights. A thermos of hot water for a midnight exchange sees me through to dawn.

You might prefer to make an electrically heated eyepiece case. The thing is to have the heat in the eyepiece from the start.

Patience, persistence and adaptability
Our opportunity to use a scope, leaving life and work aside, is pretty much determined by the weather. Even if the sky is clear, conditions can range from poor (all too often) to cracker-jack good (not nearly often enough). Transparency if poor ruins our ability to see galaxies. Poor seeing limits how high in magnification we can pump things to. But, even with difficult conditions, changing our aims for the night, or limiting magnification, we can still make a poor night a memorable one. Taking a couple of scopes or packing your binos with your scope, will allow more versatility in observing capacity as each scope has its own set of strengths and weaknesses.

These are some thoughts that hopefully go to inspire some ideas for you. I'll try to add some more soon.

Mental.
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  #50  
Old 20-08-2017, 02:04 PM
gregw (Greg)
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This is a very interesting article. I have spent the last twelve years visually observing from a very light polluted area about 4ks from the centre of Brisbane. Using an ED80 and William Optics FLT132 with good Nagler eyepieces, double stars and solar system objects can prove rewarding, galaxies and low surface light objects are a total frustration, particularly when you compare the results from a dark site.

I absolutely agree with the comment about patience. Every now and then the neighbourhood is totally quiet all the lights are off and you can get lost in your observation and begin to see the subtle variations afforded by variations in seeing, time just passes while you remain fixed on an object. It can be an otherworldly experience.
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