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Old 22-09-2011, 10:17 PM
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How to hone observing sensitivity and accuracy

In responding to one of my recent observation reports, some very experienced observers - Rob_K, madbadgalaxyman and pgc hunter have put in some very good tips about how to be sure that some faint features seen are real and also how to see faint features more clearly. I learned heaps from what they had to say.

As many people may miss that thread and there are clearly a lot more people out there with valuable tips for how to enhance visual observing, some of us thought that it would be good to start a thread on the topic.

So all ideas, questions and tips are welcome on how to see more clearly. There is a lot to share and learn from each other.

For those who've not read the original thread, http://www.iceinspace.com.au/forum/s...ad.php?t=80800 is the link - there are many gems to be mined!

If there is enough interest, maybe it could be a sticky
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Old 22-09-2011, 11:43 PM
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mental4astro (Alexander)
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A very good idea on a sticky for observational techniques and tips, Paddy. I'd be happy to contribute a few words too. It all helps.
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Old 22-09-2011, 11:46 PM
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Top idea Paddy, no doubt it'll help many other observers aswell

Some tips for getting the best out of limit-of-vision objects as requested:

- if possible, seek out your targets in the early morning hours.... not only because light pollution will be at a minimum as business are closed, vehicle traffic is at a minimum and most people are long asleep, but you'll have been dark adapted for several hours already (if you started observing in the evening).

-use a dark shroud over your head and keep both eyes open, covering the unused eye with your hand. You'll avoid the discomfort which occurs from unnaturally squeezing one eye closed for long periods and the associated eyestrain which will result. Works wonders and really helps with visibility of faint objects. I live by this.

-Jiggling the scope may help spotting faint low surface brightness objects.

-take a break every couple of hours and have a snack/drink.. keeps you alert and full so you won't have distracting thoughts of a midnight maccas run Taking regular snack breaks helps you relax and relieve any eyestrain etc and allows you to hit the next object refreshed and invigorated.

-use magnification...if seeing is good, high power is your friend. It darkens background sky so increases contrast of faint galaxies and stellar objects. Recently, my best views of Neptune's moon Triton and Uranus's moons was at 600x with an 8" scope. Ofcourse, experiment and find out what works best for you.

-Study the FOV for several minutes...if something is really at the limit of vision and popping in and out of sight, verify that it is not "averted imagination" by observing the field intensely, noting each time the object "pops" into view it is in the same location using nearby stars/objects. If you get that dust mote sighted 5-10 times and each time it correlates to its correct position relative to nearby objects.... that to me is a hit.

-no booze! I'm normally the last person on earth to knock back grog....but it stuffs with your night vision, body temperature, makes you tired and lose concentration and you just won't be at 100% if you're a bit tipsy

Last edited by pgc hunter; 23-09-2011 at 12:05 PM.
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Old 23-09-2011, 10:21 AM
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In a forthcoming post, I shall try to summarize the many good suggestions that have been made so far, as to how to improve our ability to see faint objects in the telescope.

I am glad the active observers are chipping in, with many suggestions.
We have got a lot of worthwile techiques together, in a short period of time!

Of course, moving to a binocular telescope is another good way to see more. In a side by side comparison, for example, I found that an 8 inch binocular telescope was about equivalent to a 10 inch "monocular" telescope, and there were types of objects where the binocular improvement over a standard 8 inch monocular telescope was even greater:
- angular resolution significantly improved
- Dark nebula observing becomes a really major event, for people with binocular telescopes!

I have not done any detailed assessment of how binocular vision deals with very low surface brightness light at the edge of detectability, as compared to monocular vision.
But I did have a period when I used only 10by50s , and my impression was that there are times when you see low surface brightness nebulosity in binos that would be too hard to see in a monocular telescope of the same design and aperture.

Last edited by madbadgalaxyman; 23-09-2011 at 10:28 AM. Reason: correction
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Old 23-09-2011, 12:18 PM
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I have found that billberry's seem to work quite well to improve your night vision and faint object viewing.

They were used in the second world war by the British bomber pilots to enhance their night vision. Taking them as a dried fruit, jam or tablet seem to have the same effect.

I tried it as an experiment and observed faint PN's without taking billberry tablets and then tried the same PN's again after taking Billberry tablets for about six weeks. I was happy to see that I was actually observing fainter details but the effect does drop off very quickly if you stop taking them.

These results may not be the same for everyone, but at the very least you are getting a nice dose of antioxidants into your system.
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Old 23-09-2011, 08:23 PM
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great thread guy's,it's been awhile since iv'e posted a report.i should have my replacement scope on wednesday so i'm very very keen to get back in the pod it's been quite a few months.like some of your tips so far especially the hand over the eye..stops that squinting.

most of my observing is done after midnight darker skies,no cars and i feel better after a few hours sleep (especially after laying bricks all day in the summer sun) i feel refreshed...also that evening cloud has disappeared...
heading on a boat cruise in about 10 days and heading to noumea so i'm going to take my bino's and do some seeing to the north let's hope the seas not to big try and see some objects not visable from home..
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Old 23-09-2011, 10:12 PM
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This is a repeat of my last post in the "Observation Reports" forum, which had to be put there because it follows on from mental4astro's post regarding Observing techniques. However, it now belongs to this forum on how best to observe faint deep sky objects.
__________________________________

In visually observing a faint galaxy or faint HII region, or observing a faint feature within a galaxy or HII region, I would probably do a combination of the following things:

- looking fixedly, just to one side of the target object, while concentrating on the object itself, for 5-10 seconds, thereby allowing the exposure time of the rods to be used, and thereby allowing an image to build up.
- moving my eyes randomly and rapidly around the field, in order to relax or reset them
- looking fixedly just to one side of the target object again (but looking at the opposite side of the object to the side I looked at first), while still concentrating on the object itself. (again, for 5-10 seconds)
- looking straight at the object, for comparison with the views that I get using averted vision
- moving the telescope, just a very little, from time to time (as mentioned in mental4astro's post), which can make the object more obvious.

I repeat all of these steps when I observe a vanishingly faint Diffuse object, often repeating them many times, and I find that I do gradually build up a better idea about the morphology of the "very very faint object" in the eyepiece. This seems to be an additive process, and the various glimpses that I get of the object (or of features within the object) can be used to build up a better picture of it.
I have been known to persist for up to one hour on a single object, at which point my eyes are thoroughly fatigued.

If I am not sure whether or not I have seen something, I resort to some of the stratagems in my previous post within this thread ("When the eye+brain sees an intermittent feature - is it real?).
___________________________________ ___

There have been some studies done of how far away from the object, in degrees, your gaze should be centred, in order to put the light from the object onto the most sensitive part of the retina. But there is some individual variation, and this is something that is worth studying!

An important point, as per my above description of observing technique, is that both staring fixedly and (at other times) moving the telescope a tiny bit, are probably necessary to see all that we can see in a very faint object.
__________________________________
___________________________________ _______

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Old 26-09-2011, 10:34 AM
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Sab, a question about your shroud technique. When I've tried this, my breath increases the humidity under the shroud and the eyepiece fogs up. How do you avoid this?
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Old 26-09-2011, 10:37 AM
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Conversely, Robert, I reckon an layman's understanding of how our eyes work, then how to exploit this, is important too:

One thing I've read so far that is being hinted at is what I call "light saturation" of our eyes. We typically sit on an object, and as the observation time elapses we begin to actually see less in the object than we noticed at the start of the observation. We are not imagining this. What is needed here is to restimulate our eyes. This is somewhat akin to how our nose looses its sensitivity to a particular odor when exposed to an odor for an extended period of time.

Another part to this is how our eyes are made to detect motion. Here's an example: You're looking across a peaceful valley. We see nothing moving, other than a few leaves on the trees (due to the breeze). Unconsciously our eyes begin to dart around, looking for movement (from a possible threat). We spot something out of the corner of our eye, a rabbit shooting off from a stand-still - we didn't see it at first even though it was in plain sight, as it wasn't moving, and the sudden change in light conditions, small as they were, was instantly picked up by our eyes when the bunny moved.

Where I'm heading to here is that a still, unmoving telescope is our biggest impediment. Our eye (or eyes if you're using a bino viewer), darts over the image the eyepiece presents. Low light quickly saturates the rods in our eyes, and we no longer see as much detail.
Solution: give the scope a little tap to set off a vibration, and all of a sudden our eyes begin to see detail! The induced movement restimulates the natural reactivation mechanism in our eyes.

This is something that I had noticed for many years, but wasn't aware that it was of the physiological reason behind it until it was explained to me. I had struggled on occasions to spot very faint objects at times, even though the charts said the object SHOULD be there. Yet, I only noticed it when there was a brisk movement or vibration induced in the scope, otherwise the object seemed to be totally invisible.

This is one reason why I've decided not to motorise my dobs. The constant shifting of the scope I actually now find is most benificial to my productivity.

Robert, your observing method is most thorough! Uncanny too how my own method has developed similar to yours. BUT what I hadn't done was attempt to exploit more of the rod-rich areas of my eye. I've settled into my own pattern, but you've inspired me to attempt a new stratergy.

Having an observing stratergy that is based on understanding the physiology of how our eyes work is probably the best way of making the most of our obseving time. The flexability in developing your own stratergy is the key here too. What I hadn't mentioned was the crucial importance of averted vision in the physiology. It will be a most interesting thread if Paddy succeeds in getting a sticky on this going. Most interesting.

Mental.
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Old 26-09-2011, 10:58 AM
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Thanks for your comments, Mr mental4astro,

It is hard to know what is the very best technique to adopt, when using the eye+brain+telescope system.

I hope that some of the other very experienced observers will make a serious attempt to clearly codify (hopefully in English, and not in Klingon) "what they do" at the eyepiece, and then write up the results in this thread.

It would be really nice to compare techniques between a large number of experienced observers.

Somewhat more objective could be the results of an experiment, in which we line up 10 experienced observers, behind 10 identical optical/mechanical systems, and then we get them to do several different and defined sequences of things with their "eye and mind and telescope";
in order to compare and contrast what can be seen with each sequence of activities.
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Old 26-09-2011, 01:35 PM
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Quote:
Originally Posted by Paddy View Post
Sab, a question about your shroud technique. When I've tried this, my breath increases the humidity under the shroud and the eyepiece fogs up. How do you avoid this?
That's a good point you raise.... the shroud is simply a black sheet of fabric draped over my head, rather than a tight fitting hood or anything like that so there is still ample room for body heat to escape. I still get fogging, but tends to be a problem only on really cold dewy nights. With the shroud, the problem is no worse than if I simply cup my face with my hands (infact the latter tends to create more fog problems).
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Old 26-09-2011, 10:10 PM
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That's a good point you raise.... the shroud is simply a black sheet of fabric draped over my head, rather than a tight fitting hood or anything like that so there is still ample room for body heat to escape. I still get fogging, but tends to be a problem only on really cold dewy nights. With the shroud, the problem is no worse than if I simply cup my face with my hands (infact the latter tends to create more fog problems).
I think I must be trying too vigorously to exclude light and holding the shroud too close around my ugly mug. I'll keep trying. Not breathing did not seem to be a sustainable option.
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Old 28-09-2011, 07:34 AM
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Hi guys,

A very interesting thread and great tips.

I have a question though not deep sky related I hope this is okay.

In a lot of observing reports I see mentions of Apparant size of an object and was just wondering how to do this myself is it plainly estimations on your knowledge of your Eps TFOV or is it more complicated than that.

Thanks in advance
reagrds Orestis
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Old 28-09-2011, 08:19 AM
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Hi guys,

A very interesting thread and great tips.

I have a question though not deep sky related I hope this is okay.

In a lot of observing reports I see mentions of Apparant size of an object and was just wondering how to do this myself is it plainly estimations on your knowledge of your Eps TFOV or is it more complicated than that.

Thanks in advance
reagrds Orestis
same here! I think they probably use the eyepiece TFOV as a reference like you say. Still, it would be just dead reckoning. The only other way I can think of is using an astrometric / reticle eyepiece.
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Old 28-09-2011, 09:14 AM
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Hi guys,

A very interesting thread and great tips.

I have a question though not deep sky related I hope this is okay.

In a lot of observing reports I see mentions of Apparant size of an object and was just wondering how to do this myself is it plainly estimations on your knowledge of your Eps TFOV or is it more complicated than that.

Thanks in advance
reagrds Orestis
Don't know about everyone else, but I use a few methods:

- First, knowing the FOV. If you've got a 1-deg FOV and a big object spans a third of it, then it's about 20' across.
- Sometimes in generating charts for small, faint objects, I obtain the distance between an obvious, reasonably tight pair of stars that will be close to the object in the field (many planetarium programs like Starry Night have this 'ruler' function).
- Also, having done that many times, you can get a fair gauge on distances between close star pairs in the field at a certain magnification and use that to estimate size.

Now finding north to add 'directions' to an observation is a different problem, using a reflector & an alt-az mount!

Cheers -
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Old 28-09-2011, 09:52 AM
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Originally Posted by orestis View Post
Hi guys,

A very interesting thread and great tips.

I have a question though not deep sky related I hope this is okay.

In a lot of observing reports I see mentions of Apparant size of an object and was just wondering how to do this myself is it plainly estimations on your knowledge of your Eps TFOV or is it more complicated than that.

Thanks in advance
reagrds Orestis
The way I mostly do it is mentally divide the FOV. So my 13mm Nagler gives me a TFOV of 28', I find the centre of the field to get 14' to the edge, then half way from there to the edge is 7' etc. It's a bit hit and miss - sometimes I'm close to what's recorded in my books and sometimes a long way off. I did buy an illuminated reticle eyepiece, but find that the red light is so bright even on lowest setting that it blots out whatever I'm trying to see. I cope with this by shining a faint red light on the secondary (benefit of a truss scope) to faintly illuminate the reticle. But it's so much mucking around that I mostly just go back to my mental reticle method with my usual eps. I like Rob's idea of comparing size to distances between close stars.

I'd love to hear Steve Gottlieb's approach...
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Old 28-09-2011, 01:23 PM
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This is a great thread Paddy!

I will go and ask Steve Gotlieb and Ray Cash for some input into this thread. They are friends of mine on facebook, and have to say, they are amongst the nicest people out there, & so helpful. I was in fact going to ask Steve before you mentioned his name anyway.

Orestis, you've asked the same question that has been plaguing me- thank you!
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Old 28-09-2011, 02:20 PM
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Okay, done- sent messages to both Steve G and Ray Cash, so we'll wait and see if they are able to help us.
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Old 28-09-2011, 07:51 PM
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Thanks Suzy!
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Old 28-09-2011, 08:03 PM
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Might I also add, "practice makes perfect"? Persistent years of observing seems to have improved my night vision over the years (or is it I am a persistent astronomer due to my night vision? *ponders*). I was a below average marksman during my time in the RAAF, but achieved perfect scores on night shoots while those around me failed to even hit the target once.
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