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    Default Re: Improving observation of deep sky objects



    Quote Originally Posted by Davesellars View Post
    While perusing the inter-web I came across this (old) article from Sky and Telescope. Quite an interesting read and learnt a few things!

    Secrets of Deep-Sky Observing - Sky & Telescope
    I've not seen this article! Thanks this should be helpful for my backyard!!!
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  2. #12
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    Default Re: Improving observation of deep sky objects

    Quote Originally Posted by omeek View Post
    Thanks for posting the link Dave! Great article!

    One thing they stated, I do all the time and I can tell a difference....

    "some studies indicate that the eye can actually build up an image over time almost like photographic film — if the image is held perfectly still"

    I've noticed that looking directly at some GC's for about 10 seconds straight, I am able to resolve a LOT more detail. Works pretty well.

    What's funny is, like John, my 'telescope viewing eye' is the opposite of my dominant hand. I am right handed but always view with my left eye. The strange thing is, anything else that requires looking with one eye, I always use my right eye. Just thought that was kind of a strange subconscious thing.
    I've found that too! Averted vision doesn't really work for me at all with GCs unless it's only to see those fainter ones of which I'm not going to resolve anyway. Staring right at the brighter ones generally works at resolving a good amount of the cluster.

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    Default Re: Improving observation of deep sky objects

    great article ..thanks
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    Default Re: Improving observation of deep sky objects

    Quote Originally Posted by kingclinton View Post
    Great article.

    Kinda adds to much of the good advice we receive here on the forum too.
    Thanks for the link.

    Cheers
    Definitely some excellent articles and posts written by Alan (KT4HX) and J Gardavsky - anyone with a remote interest in Deep Sky Object observations would do very well reading them.
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    Default Re: Improving observation of deep sky objects

    Quote Originally Posted by omeek View Post
    What's funny is, like John, my 'telescope viewing eye' is the opposite of my dominant hand. I am right handed but always view with my left eye. The strange thing is, anything else that requires looking with one eye, I always use my right eye. Just thought that was kind of a strange subconscious thing.
    See? I knew you were screwed up too.

    I shoot pistols right-handed because of that goofy dominant eye thing.
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    Default Re: Improving observation of deep sky objects

    This is the reason why everybody should have a good pair of Binos:

    "a small instrument in the country will show faint nebulae and galaxies better than a large telescope in a city"

    Great article, thanks for sharing!!!
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    Default Re: Improving observation of deep sky objects

    Great article Dave, thanks for sharing it!! It seemed to better explain in detail some of the common deep sky observing practices than a lot of other sources, which is great for a beginner. I have heard about averted vision a lot, but have never heard about specific positions around the retina, like a certain side of it to be positioned on or not be positioned on, to get the best views possible. Bookmarked for future reference, and highly recommended reading for any new DSO observers.
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    Default Re: Improving observation of deep sky objects

    Glad you linked that article Dave. I have read it various times over the years (after having forgotten that I'd read it previously - that old man forgetfulness thing!). Those that have observed for many years of course have learned by trial and error the majority of things contained in the article. But it provides in one place a good description of some very key issues for the DSO observer, and I feel it is an excellent resource for those beginning and those with experience maybe trying to pick up their game just a little bit more.

    One thing about averted vision I have found is that I have a distinct sweet spot. By testing the results of averted vision at all eye positions, I found that my biggest gain is when I am looking slightly above the object, where its light strikes my eye slightly below center. That is the position where I pick up the largest increase in object brightness and size. I recommend everyone also do this check to see if they can pin down one eye position that is just a little better.

    As has been discussed, the issue of light blocking is paramount for the majority of observers since they have some form of light problem. Whether it takes the form of ground lighting intrusion (glare) or the overall sky glow associated with artificial lighting (LP). Using a tarp to block glare from nearby or even distant lights can be very helpful, and something I use at home often. Also, draping a dark cloth over the head and focuser while at the eyepiece, or using an eyepatch like Captain Bryan (arrrrrrrr!) when your eye is away from the focuser can really give you an edge. They all serve the purpose of keeping your observing eye in a darker environment in order to maintain and deepen dark adaptation.

    But even if you don't have a ground based light that needs blocking, I am sure most of you still have to deal with artificial sky glow. In such cases you can dispense with the tarps, but the dark cloth drape method and eyepatch are most certainly something that can be useful. That wretched sky glow reduces the depth to which your dark adaptation can reach. Since one of the first things we learn is that contrast is everything with DSOs, particularly galaxies and emission/reflection nebulae, being able to keep your observing eye in a darker environment can pay real dividends. Plus the eyepatch is great if you need to go into the house at some point. While your opposite eye may lose its dark adaptation, your covered eye will be blissfully in the dark while you attend to whatever you need to do inside.

    Another thing the article touched on that is of more importance than many may realize is the fact that our eyes are more sensitive to moving dim objects than stationary ones. The tube tapping and drift methods are excellent ways to confirm the presence of suspected dim, extended objects. More times than I can remember, I have verified the presence of a suspected object at the very limits of seeing by tapping the tube. If that faint suspected glow moves with the jiggling stars, it is in fact really there and not just an aberration. Also, by moving the suspected object just out of the FOV and letting it drift back into view and across the FOV with the normal motion of the stars is a good way to detect sublte shading variations against the background sky. A good example of this is when looking for the connecting bridge between M51 and NGC 5195. This gentle, natural movement across the FOV can allow your eye to pick up the delicate variation between light and dark associated with this feature.

    Given the environment most of us have to observe in now, finding creative little "tricks of the trade" is critical. As one can clearly see there are various methods that can be employed to try and give us at least a little bit of an edge in our increasingly difficult observing conditions.
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    Default Re: Improving observation of deep sky objects

    In addition to tapping and FOV, I've found focusing in and out can help resolve faint objects. When I focus I also shake the mount, so I get some benefit from that but really I think even if it was done without contact (electronically say) I think going in and out of focus helps.
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    Default Re: Improving observation of deep sky objects

    Quote Originally Posted by ramdom View Post
    In addition to tapping and FOV, I've found focusing in and out can help resolve faint objects. When I focus I also shake the mount, so I get some benefit from that but really I think even if it was done without contact (electronically say) I think going in and out of focus helps.
    I am glad that seems to work for you. I can't say that it dovetails with my experience, but I know each of us are different optically. In my case, I find defocusing tends to be counter-productive, particularly in the case of dim diffuse DSOs with low surface brightness. When we defocus we stretch or smear an object's light, which lowers its surface brightness. That is somewhat similar to what happens when we experience edge of field (EOF) breakdown due to coma in a newtonian or field curvature in some eyepieces and/or scopes. The light from the defocused stars/objects in the outer portion of the FOV is stretched, lowering their surface brightness as well as distorting their general appearance. In the case of some extended DSOs with already low surface brightness, they may simply disappear from view, even though they are within the FOV. That is why often times those that use a coma corrector with newtonians find their limiting magnitude improving as the outer portion of the field is brought to focus.

    In my case, being a manual star hopper, I prefer to have my entire FOV as close to focused as possible. When I am star hopping it is not unusual to pick up other objects I was not targeting, or even interesting patterns in very dim field stars near the EOF that I may wish to investigate. These things may not even be seen, or at least seen easily, if the outer portion of the FOV were out of focus. I have also found that during my sweeps, if my EOF performance is poor due to some aberration, that I was constantly distracted by pseudo-objects in the outer part of the field that turned out to be nothing more than a star's smeared light once centered in the FOV for a visual check. If my EOF performance is tight, then I will already know there is no need to stop for further investigation. I simply got tired of all the wild goose chases I was being sent on, and I took steps to alleviate it. This has saved me some time during my DSO hunting sessions. But again, that is what is important to me personally - perhaps not so much to the next person.

    I do find it interesting what seems to work for various observers. Of course there are old standards that work for everyone, but sometimes we do hit on something that just seems to work well for us as individuals also.
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