Finding deep space objects

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Finding deep space objects

Postby joelpeyton » Sat Mar 26, 2011 9:56 am

Hi I am currntly viewing from my garden in a sleepy Cotswold village, so light pollution is mininmal. However I am really struggling to find deep space objects. Since buying my first scope for Christmas I have managed to get views of Jupiter and Saturn, which I have to say are impressive. Also Orions Nebula is great to see, although I must admit I was expecting some colour to the clouds (I'm sure one of you can tell me why?). But bar these three objects I am really struggling to find anything else. I have purchased 'Turn Left at Orion' and yes that helps point you in the right direction, but I'll be darned if I can see any of the galaxies that are mentioned in the book. Open clusters and double stars not a problem.

Any tips?
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RE: Finding deep space objects

Postby arthur dent » Sat Mar 26, 2011 12:26 pm


Seriously Joel,

DSO's aren't called "faint fuzzies" for nothing. You will have some degree of success using averted vision but even then, most DSO's are faint grey smudges.

To "see" anything like the photos in books requires astrophotography and either long-exposures or the stacking of multiple exposures to bring out both the detail and the colour in these objects.

Using the Mk.1 eyeball, you are not going to see very much.

Art
Meade ETX-105EC
Celestron NexStar 6SE, 9x50 RACI finder, MRF, powertank & wing thing
Hyperion 8-24mm Zoom + various other EPs
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RE: Finding deep space objects

Postby ronin » Sat Mar 26, 2011 9:03 pm

Only read 1 ost where the person was definite that they had seen colour in Orion, they had a 16" scope.

Can get away with less but you need it to be dark. One person in Canada has mentioned colour in Orion with a 6" scope (and imagination) but you are talking about no lights at all for hundreds of mile there. Been out there in the middle of nowhere, you are literally afraid to take a step, you can see nothing it is so dark. Skies are good though, don't need a scope, eyes are perfectly fine when it is that dark.

As to books I use the Monthly Sky Guide, it picks a constellation each month and gives details of it and what is in and around it. So all the DSO's are identified and shown where in the constellation they are. Go out, locate the constellation, locate where the DSO should be and aim the scope. I find it easier to use the TLAO.

Go take a look at Wikipedia, enter Messier Object List in the search and you get a list of all Messiers. Think the "Green" ones are Galaxies, actually not that many.

Try the Virgo cluster, LOTS of galaxies in one wide group.

But they are all grey.
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RE: Finding deep space objects

Postby ok0510@126.com » Tue Mar 29, 2011 1:33 am

ON my first astro holiday, I climbed the steps required to reach the eyepiece of the 1/2 metre(20") dobsonian with great excitement. My hosts had obligingly centred the Orion Nebula, and as this telescope seemed such an enormous beast, I really thought I was in for a magnificent and colourful view. Seeing a small patch of pale blue/greyish light in the eyepiece was quite a disappointment :( There were a number of factors at play here(eyes not fully dark adapted, glasses wearer etc!), but the main one was that my expectation(imagination) had exceeded the reality. At the time I was really quite disappointed indeed, and it is only now that I've tried viewing many times with my own equipment that I can think how good those first views actually were, even though I didn't realise it at the time.

From the 1/2 metre, we then moved onto the 7" Maksutov Newtonian, where I attached my dslr, and once again targeted the Orion Nebula. On the EQ6 mount, after a quick P.E.C., I was able to get 4 minute unguided exposures without star trailing. After viewing the result of my first image, I could hardly control my excitement. The nebula was captured in amazing detail, with vibrant colour throughout. Having had the initial disappointment with the 1/2 metre first, it made these images even more thrilling for me, and I'm so pleased it happened in this order [:)]

To get the best from any equipment you use visually for DSO's, you need to have dark skies, good clear seeing and ensure that your eyes are fully dark adjusted. There's probably many other things(equipment down at ambient temperature, steering clear of building giving off heat, filters etc!) that the more experienced observers on here can suggest, but these few basics should start you off in the right direction. All I would say is that when you do start getting blown away by what you visually observe, just wait until you start imaging them, as it's another exciting step along this great hobby of ours!

Regarding finding DSO's, other than getting a decent goto setup and learning how to operate it correctly, you just need to study the areas of sky that have objects of interest for you. Turn Left At Orion is an excellent help with this, so make sure you make good use of it and don't forget about free programs such as Stellarium which will show you exactly what's in the sky on any particular night. I'm a lazy blighter, so I just wait for my Sky At Night Magazine to arrive to tell me what I'm going to be clouded out for each month[:@][:D]

Clear skies [:)]
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RE: Finding deep space objects

Postby philip pugh » Tue Mar 29, 2011 3:26 pm

I'd start off on the brighter open star clusters first before tackling galaxies. The Beehive (M44) is well placed for observation at the moment.

You may find this rather useful:

http://philippugh.fortunecity.com/DeepSkyDescription.html
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RE: Finding deep space objects

Postby david morris » Fri Apr 01, 2011 8:06 pm

One thing not yet mentioned is that the light sensitive parts of the eye [rods or cones, I'm never sure] will stay 'turned on' longer than the colour sensitive parts in dark conditions, so they will pick up all photons as white light.

So much for a naked eye Horsehead :(
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RE: Finding deep space objects

Postby sftonkin » Sat Apr 02, 2011 10:50 am


[quote]ORIGINAL: David Morris

One thing not yet mentioned is that the light sensitive parts of the eye [rods or cones, I'm never sure] will stay 'turned on' longer than the colour sensitive parts in dark conditions, so they will pick up all photons as white light.
[/quote]

Both rods and cones are light-sensitive. Cones are involved in colour perception (3 different types of cone are each responsive to 3 different wavelengths), but the rods have a lower activation threshold, possibly as low as single photons. It's not a matter of anything staying "turned on longer" -- they are always "on" at low light levels.
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RE: Finding deep space objects

Postby david morris » Sun Apr 10, 2011 6:53 am

[quote]ORIGINAL: sftonkin


[quote]ORIGINAL: David Morris

One thing not yet mentioned is that the light sensitive parts of the eye [rods or cones, I'm never sure] will stay 'turned on' longer than the colour sensitive parts in dark conditions, so they will pick up all photons as white light.
[/quote]

Both rods and cones are light-sensitive. Cones are involved in colour perception (3 different types of cone are each responsive to 3 different wavelengths), but the rods have a lower activation threshold, possibly as low as single photons. It's not a matter of anything staying "turned on longer" -- they are always "on" at low light levels.
[/quote]

I miss out one [important] word... :(

I did mean the coloured light sensitive parts, and 'turned on' was just short hand. I seem to recall there is a biochemical changes after around 30 min in dark conditions that make the rods more sensetive as well aiding in night vision.

It would be useful if a "certain astronomy magazine" could print a chart comparing half a dozen sights through scopes of 3-10" so people could get a realistic expectation of what they would see.
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RE: Finding deep space objects

Postby brianb » Sun Apr 10, 2011 9:40 am

[quote]I seem to recall there is a biochemical changes after around 30 min in dark conditions that make the rods more sensetive as well aiding in night vision.
[/quote]
In the dark adapted retina, the rods are linked to rhodopsin molecules, photons hitting these can unlink the rhodopsin with an electron exchange which will fire the attached neuron. It takes the rhodopsin a while to relink itself & the rod will not fire again until it has done. In bright light, almost all the rods are regenerating; in very dim light, they're almost all ready to fire therefore the eye is at its most sensitive to light.

The variety of rhodopsin used by the rods is not unlinked by light at the extreme red end of the spectrum, which is why dim red light is useful for preserving night vision.
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RE: Finding deep space objects

Postby arthur dent » Sun Apr 10, 2011 2:23 pm

Reading your post there Brian I think your initial sentence has rods & cones mixed up in parts. Should the first part of your first sentence read: "In the dark adapted retina, the [color="#ffcc00"][b][i]cones[/i][/b][/color] are linked to rhodopsin molecules, photons hitting these can unlink ..."

There are, I believe, some 120 million rods in the retina and only about 6-7 million cones.

Rods are more sensitive to light/dark and are found surrounding the macula (yellow spot) in the retina, whilst cones are sensitive to different wavelengths of light (ie colour) and are most active in bright-light conditions. The cones (plus some rods) are found in the macula (or yellow spot) which is more or less directly in line with the front of the eyeball (the iris) when looking directly forward. In the central 0.3mm of the macula is the [b][color="#ffcc00"][i]fovea centralis[/i][/color][/b] where there are densely-packed cones and no rods at all.

This would account for the astronomer's trick of [color="#ffcc00"][b][i]averted vision[/i][/b][/color] when observing dim objects. Looking at a dim object, the light is falling on the fovea centralis and, being dim and there being no rods, nothing much is percieved. Glancing slightly to one side allows the light to impinge on an area of the retina that has rods in it and the object magically appears out of the darkness - albeit not in any great detail and generally in monochrome.

The cones come in three different types sensitive to Red (approx 64%), Green (approx 32%) and Blue (approx 2%) - which accounts for our rather poor perception of blue light.

Art
Meade ETX-105EC
Celestron NexStar 6SE, 9x50 RACI finder, MRF, powertank & wing thing
Hyperion 8-24mm Zoom + various other EPs
Canon 550D + T-ring, Philips NC880C and 900C webcams for AP (all un-modded)
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