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Observing >> Deep Sky Observing

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Almagne
member


Reged: 02/25/08

Intermediate Deep Sky advice?
      #5875039 - 05/21/13 12:27 AM

Is it possible to get some good advice as to "how to best observe" certain classes of objects? Perhaps something more than just the standard advice of taking a well collimated dob to a dark site during a new moon. The idea is the get some advice on how to best use the equipment one has, rather than recommend some specific eyepeice, etc.

Lets assume an intermediate sized, well figured dob (12 to 18 inches). It is well collimated with a decent selection of quality eyepieces ( let's not get bogged down into the merits of one eyepiece over another.) Given that what are your techniques?

1. How best it observe galaxies? Its been said that 150 to 225 power is best; others say 2- 3mm exit pupil. What is your rule of thumb on this? Any other advice as to how to maximize the quality of the view (other than getting a better eyepiece.)

2. Any techniques on getting the views for nebulas? Emission, reflection, dark, and planetary - these are all very different objects. Do you do anything different for each class of these objects?

3. Globs? Any special techniques?

4. Finally open clusters. Maybe these would not all be considered deep sky objects, but any techniques?


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Tony Flanders
Postmaster
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Reged: 05/18/06

Loc: Cambridge, MA, USA
Re: Intermediate Deep Sky advice? new [Re: Almagne]
      #5875168 - 05/21/13 05:37 AM

Quote:

Is it possible to get some good advice as to "how to best observe" certain classes of objects? Perhaps something more than just the standard advice of taking a well collimated dob to a dark site during a new moon. The idea is the get some advice on how to best use the equipment one has, rather than recommend some specific eyepeice, etc.




The first five pieces of advice are:

Use averted vision.
Experiment with different magnifications.
Use averted vision.
Practice, practice, practice.
Use averted vision.

That kind of sums up deep-sky observing. It's also extremely helpful to compare your observing against what other people see (numerous examples in print and online) and against photographs.

Quote:

How best it observe galaxies? Its been said that 150 to 225 power is best; others say 2- 3mm exit pupil. What is your rule of thumb on this?




Personally, I find that a 1.5-mm exit pupil is usually best overall. But you should definitely try different magnifications for yourself. Often different magnifications show different aspects of an object.

The other big piece of advice is: when looking for spiral arms, concentrate first on the dark areas between them. In time, the spiral arms will swim into view.

Quote:

Any techniques on getting the views for nebulas?




Always experiment with different filters; you never know what you'll find until you try. Don't be afraid to use high magnifications, especially for planetary nebulae.

Quote:

Globs? Any special techniques?




Averted vision and plenty of magnification. It's hard to go too high.

Quote:

Finally open clusters.




To my mind, this is the most challenging class of objects because open clusters are extremely varied. And when looking through an eyepiece, it's impossible to tell for sure which stars are true cluster members, or even if the thing you're looking at is a true cluster. Truth be told, the pros with all their photographs and spectroscopes often don't know either.

Here, there's no substitute for observing many different clusters to get a sense of their diversity. And experimenting with different magnifications can be particularly helpful.


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galaxyman
Vendor - Have a Stellar Birthday
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Reged: 04/04/05

Loc: Limerick, Pa
Re: Intermediate Deep Sky advice? new [Re: Tony Flanders]
      #5875454 - 05/21/13 10:26 AM

Tony certainly nailed it, and I'll add patience.

Meaning waiting for moments of good seeing or sky conditions to optimize.

He also mentions trying different magnifications, which is correct since many of these objects are best seen with a particular telescope using or trying varied magnifications. This is because of the variance of magnitude, surface brightness, shape, size of the object, and the particular sky conditions that night. Galaxies for instance can be extremely variable, plus even large galaxies the use of very high power can bring out small details within the galaxy.

Planetary nebula can also be terrific using very high magnifications, bringing out photographic detail.


Karl
E.O.H.


Chesmont Astronomical Society - www.chesmontastro.org
Galaxy Log - http://www.youtube.com/user/GalaxyLog4565?feature=mhee
Galaxy Log Blog - http://galaxylog.blogspot.com/
HASB - http://www.haveastellarbirthday.com
Telekit (Swayze optics) 22" F/4.5 Dob
Homemade (Parks Optics) 12.5" F/4.8 Dob
TMB/APM 8" f/9 Refractor”The Beast”. One great DEEP SKY achro
ES 6" f/6.5 achro. Good one
Celestron Omni XLT 102 refractor.
Celestron 10x60mm Binos


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Astrojensen
Post Laureate
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Reged: 10/05/08

Loc: Bornholm, Denmark
Re: Intermediate Deep Sky advice? new [Re: galaxyman]
      #5875553 - 05/21/13 11:08 AM

Quote:

Planetary nebula can also be terrific using very high magnifications, bringing out photographic detail.




I'll second (or third) this. I have used extremely high magnifications on planetaries, around 200x per inch, and seen amazing detail. You can only do this with the brightest ones, those with very high surface brightness. Don't try it on the Ring, M57, or M27, they'll just disappear. DO try it on NGC 6210, NGC 6543, NGC 7662, IC 2149, NGC 2392, J900, PK64+5.1, NGC 6826...

It does require an extremely stable mount. An EQ-6 is barely adequate, even for a very small instrument. You really need a rock-solid mount. Also, wide-field eyepieces with good eye ergonomics and good eye relief, such as Radians, Naglers or ES82s are a godsend. You'll also need a very strong barlow, 3x - 5x, depending on your scope and eyepiece collection.

You will also want very good seeing...

What you DON'T need is a large scope. A high-quality 4" refractor or maksutov on a stable mount is more than enough to begin to show some truly fascinating details in the bright planetaries listed above, using magnifications in the 600x - 800x range. A 6" can be taken to well over 1000x, provided it has a stable enough mount. My 63mm Zeiss Telemator shows detail in some planetaries, using 381x (I don't have a strong enough eyepiece/barlow combination for this scope to take it any higher), details usually though to require a substantially bigger telescope.

But all things equal, a bigger scope will of course be better, just remember, it needs to track and be stable at those ultra-high magnifications. These are no easy requirements to fulfill for a large scope.


Clear skies!
Thomas, Denmark


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BillFerris
Post Laureate
*****

Reged: 07/17/04

Loc: Flagstaff, Arizona, USA
Re: Intermediate Deep Sky advice? new [Re: Almagne]
      #5875839 - 05/21/13 12:59 PM

I'll offer a couple of observing strategies. One, is to focus your observing on objects near the celestial meridian. This is when objects are highest above the horizon and, as a general rule, best placed for observing. Two, observe the most challenging objects after midnight. This is the time of night when the contribution to local light pollution from nearby communities is at its lowest. Depending on where you live, you may pick up a few tenths of a magnitude in sky darkness, which could mean the difference between a positive or negative detection.

As for good general observing techniques, I'll echo the recommendations to use high (~2mm exit pupil) magnification. Studying an object at high power for at least 5-10 minutes will darken the surrounding sky enough to allow your eye to further dark adapt. The more complete your dark adaptation, the more sensitive you will be to faint light sources. High magnification will also make fine details large enough to be discernible as having dimension. Personally, I like to spend a minimum of 15 minutes on each object and have often devoted 30 minutes to an hour to studying complex, detailed or otherwise interesting objects. The more time you invest, the more you will be able to see.

Averted vision is a valuable technique. You can also maximize your ability to detect a faint, extended object by gently tapping the eyepiece or watching as the object drifts through the field of view. When fully dark adapted, an object in motion is easier to detect than a stationary one. These techniques introduce motion and can aid in your detection of objects at the threshold of visibility.

Above all, remember that deep-sky observing is primarily an exercise in contrast detection. Anything you can do to improve object contrast vs the surrounding sky will allow you to see fainter objects and details. When all else fails, find the largest aperture on the field and ask the owner if they wouldn't mind taking a brief look at your object. The reduced threshold contrast of the larger aperture may allow you to make the observation. Armed with that beta, return to your scope and have another go.

Bill in Flag


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Tyranthrax
sage


Reged: 04/22/13

Loc: Tampa, FL
Re: Intermediate Deep Sky advice? new [Re: BillFerris]
      #5875987 - 05/21/13 01:56 PM

My biggest advice I've gotten off of here is patience and persistance. One day you see the objects that take your breath away and marvel at the complexity the next you are scratching your head wondering if the tracking is off, then realise its just not a good night to see it. The rest of thier advice here is pretty sound.

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Sasa
professor emeritus


Reged: 11/03/10

Loc: Ricany, Czech Republic
Re: Intermediate Deep Sky advice? new [Re: Tony Flanders]
      #5876264 - 05/21/13 04:00 PM

Tony, I would also add to your excellent suggestions:

Try to sketch what you see.

This goes with your recommendation of comparing the observations with others. Sketching forces me to really think about what I see. I need to answer questions like, is this tiny brightening real or just my imagination? Next time my brain has have more intuition what is real and it will react more quickly. This helped me a lot on my way to becoming more experienced observer.


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Nick Anderson
super member


Reged: 04/21/13

Loc: Virginia, USA
Re: Intermediate Deep Sky advice? new [Re: Tyranthrax]
      #5877092 - 05/21/13 10:42 PM

Quote:

My biggest advice I've gotten off of here is patience and persistance.




I was going to say exactly that: "patience and persistence". I've had numerous people say "that object is impossible for an 8-inch scope!" and later on I prove them wrong. It's all about putting your time in.

-Nick Anderson


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kfiscus
Carpal Tunnel
*****

Reged: 07/09/12

Loc: Albert Lea, MN, USA
Re: Intermediate Deep Sky advice? new [Re: Nick Anderson]
      #5877256 - 05/22/13 12:56 AM

Great advice above. I'd add the use of a hood to block extraneous light.

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galaxyman
Vendor - Have a Stellar Birthday
*****

Reged: 04/04/05

Loc: Limerick, Pa
Re: Intermediate Deep Sky advice? new [Re: kfiscus]
      #5877781 - 05/22/13 11:10 AM

Quote:

Great advice above. I'd add the use of a hood to block extraneous light.




Yes, I mention much of these in the video series, particularly the GL an Intro video.

DSO observing is a skill as many above have suggested, and getting to or observing under the darkest sky you can get to, will make a HUGE difference.


Karl
E.O.H.


Chesmont Astronomical Society - www.chesmontastro.org
Galaxy Log - http://www.youtube.com/user/GalaxyLog4565?feature=mhee
Galaxy Log Blog - http://galaxylog.blogspot.com/
HASB - http://www.haveastellarbirthday.com
Telekit (Swayze optics) 22" F/4.5 Dob
Homemade (Parks Optics) 12.5" F/4.8 Dob
TMB/APM 8" f/9 Refractor”The Beast”. One great DEEP SKY achro
ES 6" f/6.5 achro. Good one
Celestron Omni XLT 102 refractor.
Celestron 10x60mm Binos


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Kraus
Pooh-Bah


Reged: 03/10/12

Loc: Georgia.
Re: Intermediate Deep Sky advice? new [Re: galaxyman]
      #5878122 - 05/22/13 02:01 PM

Don't expect to see images resemble magazine photographs in the eyepiece. I think that's why many little scopes are on e-Bay.

Patience cannot be over-emphasized.

I do like Herr Ferris. The air is thinest overhead. No need to look low to the east. The object will rise overhead, eventually.

Oh and did I say patience cannot be over-emphasized?


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Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Nyctophobia, Maryland, USA
Re: Intermediate Deep Sky advice? new [Re: Almagne]
      #5882178 - 05/24/13 12:20 PM

All the advice given so far is very good. I'll try to think of some tips that have not been given already.

Quote:

1. How best it observe galaxies? Its been said that 150 to 225 power is best; others say 2- 3mm exit pupil. What is your rule of thumb on this? Any other advice as to how to maximize the quality of the view (other than getting a better eyepiece.)




There is no rule of thumb, since galaxies can vary so much in apparent size, angle to the observer (face-on, edgewise or something in between), and surface brightness. Try different magnifications for each galaxy. One of the best ways to accomplish this is to use a good zoom eyepiece. My Baader Hyperion Zoom 8-24mm is in the focuser about 80% of the time when I'm at a dark site. A zoom can dial in the optimum image scale and perceived contrast for each object.

I know the OP requested no specific recommendations on eyepieces, but a zoom is such an underutilized and unappreciated accessory for deep sky, I felt compelled to mention it. I really do not understand why more DSO observers don't use them. If you want more power, put the zoom in a Barlow. If you want better outer-field correction, but the zoom in a Paracorr. eh...

Quote:

2. Any techniques on getting the views for nebulas? Emission, reflection, dark, and planetary - these are all very different objects. Do you do anything different for each class of these objects?




Try DSO filters for emission and planetary nebulae. If a dark nebula is in front of an emission nebula, DSO filters can help (for instance, an H-Beta for the Horsehead - B33). They are not so helpful for reflection nebulae. Better to keep the view natural and as bright as possible for them. Consult David Knisely's excellent summation of best DSO filters for different objects.

FILTER PERFORMANCE COMPARISONS FOR SOME COMMON NEBULAE by David Knisely

Quote:

3. Globs? Any special techniques?
4. Finally open clusters. Maybe these would not all be considered deep sky objects, but any techniques?




Again, use a good zoom eyepiece. It is very instructive and entertaining to see how radically the appearance of a star cluster can change as you increase the magnification. The lower power setting will give you a wider context to help determine exactly which stars contitute the specific open cluster you want to locate and observe. DSO filters will not help much for these, except maybe open clusters that are associated with a bright nebula.

Of course, for really big DSO, you need to put in a low-power wide-field eyepiece. And for very faint fuzzies, an eyepiece with high light-transmission is nice.

Mike


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Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Nyctophobia, Maryland, USA
Re: Intermediate Deep Sky advice? new [Re: Sarkikos]
      #5882223 - 05/24/13 12:37 PM

Another tip:

Avoid all white light at the dark site! This will degrade your deep dark adaptation for an hour or more after each exposure. In fact, avoid any light except for dim red light. If you use red light for your tablet, notebook, or flashlight, dim them as much as you can and still retain ability to see. Use Velcro to attach red filters over any lights inside your vehicle.

If you are serious about observing DSO at a dark site, don't view bright planets except for when you first arrive and immediately before you leave. A look at Jupiter will degrade your dark adaption.

But here's something that many observers don't seem to understand: It's also important not to mix observation of the faintest galaxies and other dim objects with any brighter objects, not just planets. After locating and viewing faint galaxies for a couple hours, I've noticed serious damage to my level of dark adaptation after a quick look at a bright globular or even a moderately bright star.

Mike


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David Knisely
Postmaster
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Reged: 04/19/04

Loc: southeastern Nebraska
Re: Intermediate Deep Sky advice? new [Re: Sarkikos]
      #5882398 - 05/24/13 02:02 PM

Sarkikos wrote:

Quote:

Try DSO filters for emission and planetary nebulae. If a dark nebula is in front of an emission nebula, DSO filters can help (for instance, an OIII for the Horsehead - B33).




No, the OIII should *never* be used on the Horsehead. That nebula emits mainly light in the hydrogen lines, so an OIII filter completely kills it. The H-Beta filter is best for the Horsehead, although a narrow-band nebula filter like the DGM NPB or Lumicon UHC will help it as well, since those filters generally pass the H-Beta line. Clear skies to you.


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Sarkikos
Postmaster
*****

Reged: 12/18/07

Loc: Nyctophobia, Maryland, USA
Re: Intermediate Deep Sky advice? new [Re: David Knisely]
      #5882432 - 05/24/13 02:26 PM

You are correct, David. That was a mistype. I should have put in "H-Beta," not "O-III." In fact, a couple months ago I saw the Horsehead for the first time. I had a Lumicon H-Beta in my 10" Dob, NOT an O-III. I'm glad you caught this so I could change my original post while it can still be edited. (But I wish I'd seen the mistake and changed it before you alerted me. You do teach, correct?)


Mike


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Dhellis59
member
*****

Reged: 08/31/12

Loc: Georgia, USA
Re: Intermediate Deep Sky advice? new [Re: Sarkikos]
      #6128594 - 10/10/13 09:15 AM

This has been an extremely helpful post. Thanks to all the contributors and the OP.

Clearr skies.


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aatt
sage


Reged: 07/26/12

Loc: CT
Re: Intermediate Deep Sky advice? new [Re: Dhellis59]
      #6132006 - 10/11/13 09:22 PM

All of the above sounds great. I would also recommend extended/prolonged viewing of each object.Don't jump around quickly. A long hard look at an object will bring out details.

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ADW
member


Reged: 07/26/13

Loc: Penticton, BC, Canada
Re: Intermediate Deep Sky advice? new [Re: Sarkikos]
      #6132573 - 10/12/13 08:09 AM

Quote:

Another tip:

Avoid all white light at the dark site! This will degrade your deep dark adaptation for an hour or more after each exposure. In fact, avoid any light except for dim red light. If you use red light for your tablet, notebook, or flashlight, dim them as much as you can and still retain ability to see. Use Velcro to attach red filters over any lights inside your vehicle.

If you are serious about observing DSO at a dark site, don't view bright planets except for when you first arrive and immediately before you leave. A look at Jupiter will degrade your dark adaption.

But here's something that many observers don't seem to understand: It's also important not to mix observation of the faintest galaxies and other dim objects with any brighter objects, not just planets. After locating and viewing faint galaxies for a couple hours, I've noticed serious damage to my level of dark adaptation after a quick look at a bright globular or even a moderately bright star.

Mike




That is excellent advice.

When you first wake up you are very well dark-adapted. When I have plans to attempt a challenge object I will avoid using any light at all between the time that I wake up and my eye goes to the eyepiece (I figure that since the blind can operate without lights, so can I). Before I go to bed, I open up the observatory, uncover my telescope, and lay out my clothes in the order that they will be put on. That means that I don't degrade the excellent dark adaption that one has when they awake (I almost always sleep for several hours before deep-sky observing).

Almost all red flashlights that you see at star parties are FAR too bright -- mine only allows me to see a small circle on the chart from a few inches away. Any brighter red light is only for working around the scope or double star and planetary observing, not for serious deep-sky observing.

Best,

Alan Whitman


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mwedel
Works with Sauropods
*****

Reged: 12/16/07

Loc: Claremont, CA
Re: Intermediate Deep Sky advice? new [Re: ADW]
      #6142130 - 10/17/13 12:29 AM

Quote:

Almost all red flashlights that you see at star parties are FAR too bright -- mine only allows me to see a small circle on the chart from a few inches away. Any brighter red light is only for working around the scope or double star and planetary observing, not for serious deep-sky observing.




Strongly agreed. I taped a coin over the business end of my red flashlight so only a dim glow leaks around the edges. Someone more technically inclined would go in and yank all but one of the LEDs, but hey, my solution only cost me $0.10, and that only temporarily.

Here's something I haven't seen mentioned: breathe deep, all the time, and for the very hairiest detections, try hyperventilating for a few seconds. I got this from one of Jay Reynolds Freeman's essays, and at first it sounded like, um, hooey. But I have tried it and gotten good results.

I should say that this only works on top of (a) fanatical dark-adaptation, (b) fanatical use of averted vision, and (c) fanatical patience.

Why all the fanaticism? Because when that edge-of-what's-possible object finally swims into view, it will be so worth it.


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aatt
sage


Reged: 07/26/12

Loc: CT
Re: Intermediate Deep Sky advice? new [Re: mwedel]
      #6143781 - 10/17/13 09:24 PM

Continual deep breathing? Well that one is new to me. Thanks for the tip!

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