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What size aperture for galaxies?

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#1 ICE Q

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Posted 21 April 2010 - 10:29 PM

I went to an astronomy club meeting last week and had a chance to look through several telescopes, the largest being a 12" Orion Dob. The viewing conditions were good, but not great, as there was some haze and a little light pollution. We looked at several galaxies, the Orion nebula, Saturn, Venus and Mercury. I was surprised to find the galaxies looked like fuzzy patches, even in the xt12. This has me wondering - what size aperture would I need to see the spiral arms in galaxies? What aperture is needed to see color in emission nebulea?

Although I cannot afford to buy or transport a huge scope, I probably could afford a tank of gas or two to drive somewhere that does have a large scope.

If you have experience with big scopes, at what size do you think DSOs become spectacular?

Gary

#2 kev721

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Posted 21 April 2010 - 10:35 PM

CAAS?

#3 lymorkiew45

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Posted 21 April 2010 - 10:36 PM

With a 12" scope, you should beable to see spiral structure in the brighter galaxies, and a myriad of fainter galaxies under dark skies. M51 really shows it's stuff with such an aperture under dark skies, so you were using the right scope. You could use a 20", or bigger scope and as an inexperienced observer, not see any detail in M51, or other galaxies. Regardless of aperture, you still need experience to glimpse such intricate detail. It takes some experience, patience, and time to see detail as subtle as this, so the minumum aperture to see spiral structure in galaxies would be around 8" and up, and dark skies...clear skies... :rainbow:

#4 Hrundi

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Posted 21 April 2010 - 11:30 PM

They're fuzzy patches regardless of aperture. Spiral detail should start showing up at around 8" for a few galaxies, but it's not easy. Spirals are faint, very low contrast, and require practice to see.

However, they become spectacular rather quickly :lol: I like galaxies in 6-8" and up, though.

#5 HiggsBoson

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Posted 21 April 2010 - 11:44 PM

On my first trip to as star party I was shown M57, the ring nebula, in an 8” scope. I told the scope owner that the scope had moved and that there was nothing in the field of view. He corrected me. I thought this is hopeless. There is almost nothing there. Seeing things in the dark is a skill. The ring is one of the few DSOs that I can find without help. The LP in my area is oppressive. To date I have not found a galaxy with my 6” scope. There are simply to many lights to allow dark adaptation. I can find M31 with binoculars but it is only a smudge.

Dark skies and developed skill are the key to galaxies. My schedule rarely allows for trips to such skies. To date I have not taken such a trip. I have chosen 12.5” for my deep sky scope and it is designed to be more transportable than my current 6”. With this I will seek dark skies and the galaxies I have waited so long to see.

#6 Darenwh

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Posted 22 April 2010 - 06:01 AM

As stated, dark skies and practice are needed to see much with galaxy's. A little haze plus some light pollution likely washed out the galaxy's for the most part. Personally, though details can sometimes be seen in scopes as small as six inches in perfect conditions, I believe that twelve inches is the minimum size for good views of galaxy's. From twelve inches up they can get very interesting once your observing skills are up to the task.

Color in nebula is all ways going to be very limited. Some people see color in the Orion nebula but even it is usually very subdued and mostly green for most people. Most other diffuse nebula will be colorless. Some planetary nebula's will show a little color, usally blue or green, in larger scopes but even then it is quite limited.

For color in the sky through a scope you really are mostly limited to the planets and stars or star clusters. Star colors can sometimes be striking, especially when you have a large color contrast between different stars in the field of view.

Remember, details in galaxy's, and sometimes seeing the galaxy's at all, requires good dark skies. No haze, very little light polution, that is what is needed to see details in Galaxy's. If you are observing through poor conditions then you will see very little. I think you would have seen much more had the night been better, but then again, that would also depend on the particular galaxy you are looking at.

I will finish up with a little of my own experience with my 12.5" dob. The first time I used it on the Virgo cluster was from a good dark site in Kentucky. Using the scope from there was a revalation. As I scanned the area using a 40mm Konig eyepiece I saw numerous galaxy's and could start to see details in many of them. Edge on spirals were very evident and I could easily see the obscuring dust lanes splitting these galaxy's in two. The Sombrero galaxy was particularly striking but the whole region was alive with galaxy's. It is to this day one of my fondest memories from all my nights of observing. So don't give up. You just need to have a few aces up your sleave. One, Good Dark Skies, two, Experience, three, a little apperature, and four, a little patience. Combine those and you will have a winning hand at observing galaxy's.

#7 Tony Flanders

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Posted 22 April 2010 - 06:08 AM

If you have experience with big scopes, at what size do you think DSOs become spectacular?


About 2 inches. Yes, seriously. Just to name a few DSOs that are at or near their best in that size: the Pleiades, the Hyades, the Coma Star Cluster, the Milky Way. That last one is a big one!

In my 7-inch Dob, huge numbers of DSOs are spectacular. To name a few: M35, NGC 7789, M42, M8, M17, M5, M13, M31, M33, M81/M82.

In my 12.5-inch Dob, the dozen brightest globular clusters are utterly amazing, and the next one or two dozen after that are mighty impressive, too. Hundreds of open clusters, dozens of nebulae.

As for galaxies, M31's dust lanes are very impressive through my 12.5-inch scope even in yellow-zone skies. M33's spiral arms are magnificent, and I can see at least a dozen emission areas and star clouds within them. M101 reveals a comparable number of emission areas.

M51 is breathtaking -- not only the spiral arms but also the weird kinks in them are apparent.

There are three things required to make galaxies spectacular: dark skies, skill, and the proper attitude. Galaxies are never easy -- and who would want them to be? That would be no fun!

Galaxies are inherently faint and fuzzy, but if you work at them, you can tease out a huge amount of detail.

This does require reasonably dark skies, though -- the kind where the summer Milky Way is instantly obvious and grand. At this time of year, the Milky Way is hard to see, so that's a tougher test to make. Certainly, M44 should be bold and eye-catching without optical aid.

#8 Hrundi

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Posted 22 April 2010 - 06:11 AM

I disagree on milky way at 2 inches. I find that 6-7 millimeters of eye pupil does just fine :lol:

#9 Joe Aguiar

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Posted 22 April 2010 - 06:18 AM

for galaxies i would say 8" min & bigger but the key thing you said you were looking & there "a little LP" you need to get to dark skies green zone or better,or blue even thet grey zone. You will really start to see structures on galaxies.
So its size & if galaxies are your thing its said serious galaxy obsevering starts at the 16" & more & get dark skies.

PS I am selling my obsevering land with a cabin, with picnic table & BBQ & umbrella in the grey zone for $19k:P :p

#10 Midnight Dan

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Posted 22 April 2010 - 06:35 AM

at what size do you think DSOs become spectacular?


Problem is, the term DSO covers a HUGE range of objects from big brilliant open clusters and small dim globulars, to very large spread out nebulae, and tiny planetary nebulae, to Galaxies both big and incredibly tiny.

Some of these are spectacular in a very small scope. If you're referring specifically to Galaxies and Nebulae, there are some that are pretty spectacular in a 6-8" scope ... like the Orion Nebula, Andromeda, Swan, etc. Most of the "stunners" are available to reasonable sized scopes. As you get to larger apertures, you'll find that dim smudges become brighter smudges. You'll find that some galaxies and nebulae start to pick up a little more detail. But, in the normal range of amateur scopes, you won't find a point where you start getting new stunners showing up.

The two most important factors in seeing these objects is dark skies and experience. The dark skies is obvious - these are dim objects. The experience part is not so obvious. After all, when you see something new during the daytime, how much experience does it take to see it?

The night sky is very different and the eye-brain system is not used to working in this unfamiliar territory. Much of what you see is at the limits of our eyes abilities. The brain is good at sorting through visual noise and eliminating the unimportant. Those extremely faint details in galaxies and nebulae are dismissed as noise in the system, and you actually CANNOT see them when starting out. As mentioned above, an experienced astronomer can see things in a scope that are just plain invisible to a newbie.

Over time, you'll come back to the same objects again and again and spend time studying them. The brain begins to notice very subtle details that are in the same place in the object each time you look at it. Over time, you begin to recognize these as parts of the image you're seeing, not visual noise that needs to be eliminated.

I've only been doing this a few years, but I'm amazed at the things I can see now which I know I could not when I started.

-Dan

#11 sailor70623

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Posted 22 April 2010 - 07:10 AM

Out west, in areas where the sky chart shows "black" skies, there are many Galaxies that I can see bare eye. Except for Andomeda which looks like a fuzzy foot ball, the others only look like fuzzy stars. Out there, a 6" would show structure in galaxies.
Last night, where I unloaded (Indianapolis area), It looked like it was going to be a good night to observe, but when I got parked, the LP, poor transperency, and who knows how the seeing was, as I could not make out half the stars in the Big Dipper. My guess here is that even with a 16" scope, seeing galaxies was out of the question.
At my place in Mi. I have had nights where bagging galaxies was as simple as just scanning the sky. It is a "gray" sky area there.
I had a "gray" sky area in Ok., BUT they just opened a casino about 19 miles south of where I just finished my observatory there, and now my southern view is ruined with skyglow. And the lights are on all night. This will mean that observing galaxies to the south here is gone, period. I'm sure the "gray" area may have been turned into a red or blue area now too.
SOOOO the most important thing when looking to realy observe galaxies, is a DARK sky, then good transparency, and good seeing helps too. Along with dark skies YOU need to be well night adapted. No white lights, minimal dim red light. Aperture helps, but even binos will show you a number of galaxies. Now if you want to pump the magnification to galaxies, then you need aperture, as when you up the magnification, you dim what you are looking at. That and galaxies are already small (angle of view wise) and the details in them, much smaller. And since you are trying to decern between light gray and dark gray, good contrast is a BIG plus. The only filter I have ever used that helped while observing galaxies was a Baader Moon and Sky Glow. Maybe a little help, but at least it didn't make the view worse was a UV filter. I had forgotten it in one of my Hyperions one night.
When you find that great observing site for hunting galaxies, it will also become one of your favorite observing sites for all the dim fuzzies. DSOs become a joy from a dark observing site. Watching the Mily Way set in the west and rise in the east makes all nighters worth while. Everything IMO just looks better. To me, there is nothing more relaxing than spending 2 days in the middle of no where, where not one electric light can be seen no matter what direction you look. Unless I didn't have a scope with me.

#12 bigbeck

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Posted 22 April 2010 - 07:18 AM

An 8" scope and dark skies is all you need. If you've never been to dark skies before,be prepared for an assault on the senses. Hopefully,you'll remember to actually look through the scope. Naked eye sights are jaw dropping! :bigshock:

#13 ICE Q

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Posted 22 April 2010 - 07:29 AM

Thanks, everyone who replied. The astronomy club meeting I went to was CAAS.

I am pretty encouraged by the replies. I just ordered an Orion xt8 and am looking forward seeing the detail several of you described as I gain more observing experience.

Gary

#14 bigbeck

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Posted 22 April 2010 - 08:02 AM

I have both an 8" and 12" Dob. The 8" shows much more detail in galaxies at a dark site (blue zone) than my 12" does in moderate to high LP.

#15 hfjacinto

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Posted 22 April 2010 - 09:09 AM

Gary,

With my 80MM at a dark site I can see galaxies. M81 and M82 are awesome as is Virgo, put in a wide field and I can see over 10 galaxies in the Virgo cluster (by M84). Don't expect details but they are faint and fuzzy but seeable. In my white skies, I can barely see M81 and M82 in my 9.25.

#16 kev721

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Posted 22 April 2010 - 09:26 AM

The astronomy club meeting I went to was CAAS.


Good. I joined CAAS in February. At that February meeting: overcast. At the March meeting: overcast. At the April meeting: okay seeing -- or at least that's what I hear because I missed it! %#$*!!!!

I bought an XT8 in January from a guy in Mountain Home. I have yet to look through it at CAAS. I'm keeping my fingers crossed for the May meeting. I've seen a couple galaxies from my deck in WLR, but they aren't much to observe. I think the dark skies will help a lot (if I ever get to see them).

#17 JayKSC

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Posted 22 April 2010 - 12:50 PM

Gary,

I've been able to nab the spiral arms in several galaxies (including non-Messiers) with a 150mm refractor. I've enjoyed some fine, subtle, details with galaxies and nebulae with a 77mm refractor and even have seen distinct hints of color in planetary nebulae and globular clusters with the same telescope.

Truly large telescopes (I'd say 20-inches aperture and up) can provide fantastic views, but you can detect awesome detail with nearly any aperture. The most critical factor is to patiently observe an object for around an hour rather than just glancing and moving on.

- Jay
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#18 ICE Q

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Posted 22 April 2010 - 01:15 PM

I'm getting the sense from all these replies that I will need dark skies and long, repeated viewing times to get the spectacular views I am searching for.

Is there a way to train the eye and brain for viewing? Is the trick to seeing details in galaxies and nebulae simply to spend a lot of time watching them, or are there specific viewing techniques that help either in seeing or in speeding up the training process?

Gary

#19 hfjacinto

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Posted 22 April 2010 - 01:19 PM

Gary,

The more time you spend looking at galaxies the more you see. Dark skies really help also.

#20 sailor70623

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Posted 22 April 2010 - 01:50 PM

Sure. Look at a painted wall. Do you just see a white wall. OK, that's what you are seeing now when you look at the faint fuzzies. Now, really look at the wall. You should see brush strokes, patterns in the paint. That's the kind of observing you need when you look at galaxies.

#21 Midnight Dan

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Posted 22 April 2010 - 01:57 PM

I'm getting the sense from all these replies that I will need dark skies and long, repeated viewing times to get the spectacular views I am searching for.

Is there a way to train the eye and brain for viewing? Is the trick to seeing details in galaxies and nebulae simply to spend a lot of time watching them, or are there specific viewing techniques that help either in seeing or in speeding up the training process?

Gary


Hi Gary:

There are a couple of techniques you should learn:

One is called averted vision. During the day, your eyes use cone cells which are sensitive to all colors, but not very sensitive to dim light. But because we see mostly during the day, these cells are concentrated in the middle of your eye's field of view. The rod cells are very sensitive to dim light, but only see in black and white. That's why the faint fuzzies don't show any color. But in addition, they are concentrated away from the central field of view of the eye. So, for many of the dimmest objects, when you look directly at them, they seem to disappear. You can only see them if you look slightly off to one side.

This is part of the "training" of the eye-brain system as well. If you think you see something out of the corner of your eye, but when you look there it's gone, the brain decides it wasn't really there and attempts to ignore it. Being aware of averted vision and looking for things that you're not looking at :smirk: will help develop this ability.

Another technique is scanning. Eyeglass wearers are familiar with this. The dust on your glasses is not very noticeable until you start moving your head around. Suddenly you realize how dirty they are. The brain is designed to pick up things that move in your field of vision better than those that don't. I would image that all the light receptors in your eye are not equally sensitive. So the brain "calibrates" the field of vision by compensating for areas that are slightly darker or lighter than the rest. However, if that slightly different thing moves across the FOV, then the brain decides it's really there.

I've been able to eke out some spiral arm detail on some galaxies from my backyard with an 8" scope using this technique. You can move your eyes around in the scope's FOV to get some of this benefit. But for some reason, it seems to work better if you slowly move the scope around in the vicinity of the object. This techniques is best used along with averted vision. Again your eyes are more sensitive to dim things slightly off center so it helps with scanning as well. It takes a while to notice any improvement with this method since it is much more subtle than averted vision.

But, even with these techniques, you will see more the more you look at objects. There really is no substitute for time behind the eyepiece. When you find an object, take your time with it. Look at it for a long time and try to note as many details as you can. Try different eyepieces and see if you can find one that shows more details than the others. Experiment with any filters you might have. Then move on to the next object.

Come back to your favorite objects from time to time and you'll be amazed how much more you can see after a while! Another advantage of repeated viewings is that nights differ in what you can see due to seeing and transparency differences. Once you see details on a really good night, you'll be much more able to detect them on other nights.

-Dan

#22 Skip

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Posted 22 April 2010 - 02:22 PM

Dan and the others have given you some great techniques. One I use that I haven't noticed mentioned is to tap the scope enough to make it vibrate while looking at a faint fuzzy. This seems to help make the object sort of jump out at you. Similar to Dan's technique of moving the scope a bit (well the same really).

Good hunting! :grin:

#23 coutleef

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Posted 22 April 2010 - 02:49 PM

Aperture is never the best substitute for dark skies.

From a green zone, i can see M51 in my finderscope but that galaxy is invisible in my 8" from the city.

A 12" from a dark site will be a galaxy hunter tool for real.

It is my next step!

#24 rustynailz911

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Posted 22 April 2010 - 03:29 PM

"Sure. Look at a painted wall. Do you just see a white wall. OK, that's what you are seeing now when you look at the faint fuzzies. Now, really look at the wall. You should see brush strokes, patterns in the paint. That's the kind of observing you need when you look at galaxies."

Very well said that explains learning to see as easy as it can be explained!!!i have hunted a few galaxies in my 4.5" scope one of my most jaw dropping views is m31,m32 and m110 in the same fov in my 26mm plossl.At 2.3 million light years away (and closing)m31 is one far away brush stroke.

Russ

#25 mountain monk

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Posted 22 April 2010 - 03:33 PM

Sailor: White wall--what a great example. Distills a chapter into a couple of sentences.

mm






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