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Aperture for planetaries ?

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#1 curiosidad

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Posted 13 October 2013 - 11:16 AM

Hello,
I have a 127mm MAK, and for planets and moon it's fabulous, also for double stars, but for deep sky objects ... weak weakens enough, in my opinion is "dark".
I've always liked the observation of planetary nebulae and I would like to give me your opinion on the minimum aperture to observe these objects with some structure and color, as the Mak shows these planetary as fuzzy stars without color.
I know that more aperture always is better , but want to know with diameter begins to appreciate this.
Regards and thanks in advance.

#2 David Knisely

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Posted 13 October 2013 - 12:54 PM

Hello,
I have a 127mm MAK, and for planets and moon it's fabulous, also for double stars, but for deep sky objects ... weak weakens enough, in my opinion is "dark".
I've always liked the observation of planetary nebulae and I would like to give me your opinion on the minimum aperture to observe these objects with some structure and color, as the Mak shows these planetary as fuzzy stars without color.
I know that more aperture always is better , but want to know with diameter begins to appreciate this.
Regards and thanks in advance.


You can observe many planetaries with your 127mm aperture. A good nebula filter can help a little in identifying them and bringing out detail in the larger ones, but many can still be seen without filtration. I do like eight to 10 inches of aperture when looking for detail, but there is no hard and fast lower limit for picking up and viewing these interesting objects. Clear skies to you.

#3 Astrojensen

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Posted 13 October 2013 - 02:57 PM

Hi David

Well, he mentions he has already seen a few, as fuzzy stars, and wants to know where they begin to show color and such. I've observed dozens in my 63mm Zeiss, but the brighter ones only really begin to show color to me in my 12". My eyes are fairly insensitive to color, though.

Now details, however, is a much more complex question and a potential HUGE can of worms, as I have repeatedly mentioned that it's possible to observe much detail in small, bright planetary nebulae in a small telescope, as long as it has tracking and very high magnification is used. I've seen more detail in planetary nebulae in my 94mm achromat than in any other telescope I own, including my 12" dobsonian. That is because I have been able to use extreme magnification, up to 740x, to magnify the tiny details enough that I could see them. A 5" mak should be able to perform similarly.


Clear skies!
Thomas, Denmark

#4 azure1961p

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Posted 13 October 2013 - 08:04 PM

Well congratulations on a fine Mak and a nice aperture for planetary.

Color in any planetary is slim to nil . Not saying its not there but to really see it - something like Thomas' 12" or more is much better as it gives the scale needed at the brightness required to begin to see colors. The predominant color is grey blue or grey blue-green. Some folks report pinks.

What you SHOULD know - and I learned this very late in the game - these objects can stand absurdly high magnification and sometimes show best this way. One observer with a 127mm refractor has used essentially 1000x on brighter planetary to good effect. The unusually high surface brightness of some planetary like NGC 6543 or 6210, 7027 for example keep looking better the more you enlarge them - seeing willing. I've still not done the 1000x thing on planetaries but going up to 200x with your Mak could very well show them best.

What have you got for oculars?

Pete

#5 stevecoe

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Posted 13 October 2013 - 09:58 PM

You did not provide where you live, so my answer will assume that you have access to very good skies. My opinion is that 10 inches of aperture is the minimum to see color and detail in a variety of planetary nebulae. More is better. Use 250 to 400X so that the detail will show. I saw lots in two telescopes I have owned over the years. My Celestron nexstar 11 inch SCT and a 13 inch Newtonian showed plenty of detail and some color in about 150 to 200 PN's. I had a friend who is unfortunately passed on, but all the famous PN's were excellent in his 32 inch, in case you have lots of money in the bank;-)

Hope that helps;
Steve Coe

#6 David Knisely

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Posted 14 October 2013 - 01:33 AM

Hi David

Well, he mentions he has already seen a few, as fuzzy stars, and wants to know where they begin to show color and such. I've observed dozens in my 63mm Zeiss, but the brighter ones only really begin to show color to me in my 12". My eyes are fairly insensitive to color, though.

Now details, however, is a much more complex question and a potential HUGE can of worms, as I have repeatedly mentioned that it's possible to observe much detail in small, bright planetary nebulae in a small telescope, as long as it has tracking and very high magnification is used. I've seen more detail in planetary nebulae in my 94mm achromat than in any other telescope I own, including my 12" dobsonian. That is because I have been able to use extreme magnification, up to 740x, to magnify the tiny details enough that I could see them. A 5" mak should be able to perform similarly.


Clear skies!
Thomas, Denmark


I can only provide what I personally have seen. I can see the ring form of M57 barely in my 2.4 inch refractor, and in my 80mm f/5 refractor, it is fairly obvious. I can see the Eskimo's inner and outer shells plus the central star fairly easily in my 100mm f/6 refractor, and see the oval form of many other planetaries in that scope (you just have to crank up the power a little and use averted vision). The Dumbell shape of M27 is visible in a good pair of 15x binoculars, and the peanut shape of M76 also is visible in a relatively small aperture. The Helix's main shell is also visible as a fuzzy dim doughnut in a good pair of binoculars as well (7x35's for example). Thus, a 127mm (five inch) scope should be able to see a number planetary nebulae as more than just "fuzzy stars". As for color, well, that will depend on the sensitivity of the eye of the observer, although for some like NGC 7009, NGC 6543, and a few other of the very brightest ones, even small scopes may show the faint bluish-green coloration. Once you get to eight inches however, many more show that color. Larger scopes also allow a lot more "push" in the power to reveal detail in some of the brighter planetaries by partially compensating for the lower resolution of the human eye using averted vision. Indeed, I have used over 800x this way, although again, having the aperture behind you is definitely a great help here. Clear skies to you.

#7 Sasa

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Posted 14 October 2013 - 03:34 AM

As Thomas and Pete were saying, you do not need too much of aperture to see at least some details in many planetaries. The key is to learn how to hunt for them - using ridiculously high magnifications and picking nights with good seeing are the basic tricks. Good mount capable of relaxed tracking at 300-500x range is a must. You should be also sitting comfortably during the observation. Also patience is another one, at least in case of small telescopes. It is the same as when you are trying to observe planets, many features will just pop in for few seconds and you need several minutes of focused concentration to confirm this observation.

Here are few sketches of mine of some details seen in planetaries with small telescopes from 63mm up to 110mm:

NGC6543, NGC6572, NGC6905, PK80-6.1, NGC7009, NGC7662

Of course, with large scope you could see much more. But even with 127mm Mak of yours you should be able to see much more than just fuzzy stars.

#8 curiosidad

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Posted 14 October 2013 - 08:16 AM

ummmmm! gold´s informations !!






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