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Equipment Discussions >> Reflectors

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gatorengineer
Carpal Tunnel
*****

Reged: 02/28/05

Loc: Hellertown, PA
Re: Big dob for objects with structure and detail? new [Re: acochran]
      #5910937 - 06/09/13 07:11 AM

A couple of recommendations.

I really like the night sky observers guides by will bell... Also Deep Sky wonders by Sue French (a little more on the widefield side but there are goodies in their for dobs)

I would also strongly recommend getting sky safair if you have an apple or android device and download their lists.... They have the texas star party observing lists etc...

To get the most out of your scope you have to get the most out of your eyes, I love my dark skies apparel hooded observing vest (but I am pretty light polluted here)...

Lastly if you dont already have one, a loaded astrocrub filter slide, with a DGM NPB, a Lumicon Oxygen, and a good HBeta would be a recommendation.....

For a big dob under dark skies the veil is hard to beat...


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Vic Menard
Post Laureate
*****

Reged: 07/21/04

Loc: Bradenton, FL
Re: Big dob for objects with structure and detail? new [Re: gatorengineer]
      #5911075 - 06/09/13 09:58 AM

I created this list some years ago. You'll need dark skies for some, steady seeing for others, good filters and eyepieces will help, and finally, the patience to spend time at the eyepiece really observing--not just hit-and-run target shooting--and the willingness to go back again and revisit these objects, because there's often something more to see when you thought you had already seen it all--I just recently proved this to myself (and to Stephen O'Meara).

I've been observing for many years. I'm sure I've looked at M42 a thousand times and I still enjoy each opportunity I revisit this amazing object, it's like owning a Van Gogh. These objects make up my gallery, regularly open for a pleasant stroll, an occasion to share with others, or an opportunity for intense scrutiny with all I can throw at it.

By all means--have fun!


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robininni
scholastic sledgehammer


Reged: 04/18/11

Loc: Stephenville, TX
Re: Big dob for objects with structure and detail? new [Re: Vic Menard]
      #5911101 - 06/09/13 10:25 AM

GatorEngineer:

I do have Sky Safari on my iPhone and iPad. I also have a filter slide and the only filter I don't have is H-beta as I have been waiting for months for the 1000 Oaks 2" to be in stock.

Vic:

Thanks for sharing! That's perfect. I'll print it and put it to use.

Rob


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demiles
professor emeritus
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Reged: 11/07/06

Re: Big dob for objects with structure and detail? new [Re: robininni]
      #5911249 - 06/09/13 12:36 PM

Sky conditions will vary night to night and so will the detail you see. I highly recommend getting to the darkest skies that's practical for you, spend time with the bright Messier objects and don't be afraid to really crank up the power. Tracking on a large scope can really take your observing to a higher level.

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Mike Lockwood
Vendor, Lockwood Custom Optics
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Reged: 10/01/07

Loc: Usually in my optical shop
Re: Big dob for objects with structure and detail? new [Re: gatorengineer]
      #5911620 - 06/09/13 04:29 PM

Quote:

For a big dob under dark skies the veil is hard to beat...



Amen, +1, can't agree more. Both sides. And the middle part. And some other parts. It's perfectly placed high in the sky.

M51 and M81 are also favorites, when high up.


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astrokwang2
sage


Reged: 05/06/04

Loc: Arizona
Re: Big dob for objects with structure and detail? new [Re: robininni]
      #5911622 - 06/09/13 04:32 PM

If you aren't wowed by objects in the 25, then it's an issue of experience. You can have all the cool observing guides/lists and the darkest skies on the planet, but if the granulated dust lane in NGC 891 or the hint of spiral structure in NGC 1003 doesn't impress, then more time needs to be spent getting to know the night sky.

I was thinking of the many experienced folks I've observed with. The common point of experience seems to be that at one time, we all owned smaller scopes (4,6, or 8 inch) which we used to observe the brightest targets (usually the Messiers). When you observe M51 a couple hundred times in a 8 inch, you notice a lot of variance. On some nights, there'll be distinct spiral structure seen in the main galaxy with a hint of a bridge to its companion. On other nights, it will seem like a barely visible oval smudge. Over time, you develop a definite visual memory of M51. So, on great nights of seeing, you can really appreciate the increased detail and notice tantalizing hints of other
structural details visible in larger scopes.

And when you get to observe in a significantly larger scope, those "hints" in the smaller scope (like H2 regions in the spiral arms) become visible. This is usually a wow moment! Or you may be lucky to see the "trihorn" structure flaring off the companion galaxy. The impressiveness of these details come after logging hours of NOT seeing these details in a smaller instrument or under poor skies.

In addition, these impressive details are often low-contrast. Appreciating low-contrast detail seems to be a "skill". I sometimes observe with a friend who has an engineering background. He appreciates all the scientific contexts of a nebula or galaxy's size, distance, composition, etc. But oftentimes, he doesn't see low-contrast detail. We were observing the Leo Trio (M65,M66,N3628) in his 8 inch recently, and he and another gentleman only barely saw "something" where NGC 3628 was located. Had I not pointed it out, they would have missed it. The central dust lane was not visible, but you could barely detect how one edge was flaring out. He was relatively new to amateur astronomy and had only used the scope a handful of times for night time observing.
I'm sure if he keeps observing on a regular basis, objects like NGC 3628 (aka "the Hamburger") will be routine.

As far as observing guides for visual observers, I believe guides that include sketches to be very useful. I think sketches better recreate the view through an eyepiece compared to a fancy processed CCD image. The Night Sky Observer's Guides are really useful in this regard as they often include a mixture of sketches and photos. The descriptions are certainly geared toward the visual observer.

On a personal note, I would say that I got into hunting down galaxies because I COULDN'T SEE 95% of the little ovals from the Peterson Guide's star charts. It was frustrating at first, but it became a challenge for me.
I remember stupidly questioning the accuracy of the charts, doubting my *BLEEP* SCT, blaming the cloudy skies of Seattle. Fast-forward 25 years and one night in Chiefland, FL, when I was working on my Herschel observing list, I decided to track down as many galaxies as were listed on chart 1 of the SkyAtlas 2000. I found I could see about 90% of the listed galaxies in my home-built 10" f/4.5 reflector. What had changed? I had a slightly larger scope and better skies. And I was also better prepared for what I would see: small, faint fuzzy shapes -- sometimes circular, sometimes oval -- distant light which had travelled millions of light years to reach my eye.


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bunyon
Post Laureate
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Reged: 10/23/10

Loc: Winston-Salem, NC
Re: Big dob for objects with structure and detail? new [Re: acochran]
      #5912053 - 06/09/13 09:08 PM

5128 rocks if you have a good, clear, non-light-domed southern sky. It's getting a little late in the year for North America but I've seen this from TSP a few times and it never fails. Fairly easy to find as it's plainly obvious in a 50mm finder. Well worth the look.

Quote:

I'm a little the same way, wanting to see more than faint fuzzies. When I look at M51 I wish I had a brightness knob on my scope I could turn up, like on an old TV. All I can do is look for darker skies.
Google "galaxies" on the Internet, you'll find a list of the ten brightest. Plus other lists of galaxies. Look for the ones with the highest surface brightness.
There's one I want to see, low in the south about 9PM here right now, just above the giant globular cluster Omega Centauri. I think it's NGC 5128 a mag. 7 galaxy. Those are rare.
Check out all the nebulas in Sagittarius, they are magnificent!
Andy




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BillFerris
Post Laureate
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Reged: 07/17/04

Loc: Flagstaff, Arizona, USA
Re: Big dob for objects with structure and detail? new [Re: robininni]
      #5912418 - 06/10/13 03:14 AM

The "Wow!" factor isn't nearly so much about the object as it is about the observer. Many deep-sky enthusiasts get genuinely excited about detecting an object at the threshold of visibility--not because it shows magnificent detail--because they enjoy pushing their equipment and themselves to the limit. For some, it's chasing extremely distant objects that gives a thrill. For others, it's observing obscure objects which may have been visually observed only by a handful of people on the planet. Some deep-sky hounds enjoy hunting specific types of objects; just planetaries or globulars or galaxy clusters. There are as many reasons to enjoy deep-sky observing as there are deep-sky observers. The trick is to understand what excites you. Then, equip yourself to pursue it.

Bill in Flag


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auriga
Pooh-Bah


Reged: 03/02/06

Re: Big dob for objects with structure and detail? new [Re: BillFerris]
      #5912621 - 06/10/13 09:07 AM

Quote:

The "Wow!" factor isn't nearly so much about the object as it is about the observer. Many deep-sky enthusiasts get genuinely excited about detecting an object at the threshold of visibility--not because it shows magnificent detail--because they enjoy pushing their equipment and themselves to the limit. For some, it's chasing extremely distant objects that gives a thrill. For others, it's observing obscure objects which may have been visually observed only by a handful of people on the planet. Some deep-sky hounds enjoy hunting specific types of objects; just planetaries or globulars or galaxy clusters. There are as many reasons to enjoy deep-sky observing as there are deep-sky observers. The trick is to understand what excites you. Then, equip yourself to pursue it.

Bill in Flag




Bill,
This is a truly perceptive post and reflects your impressive experience as an observer. It really does describe the various aspects of deep sky observing that appeal to different observers.

For me, faint objects that I can barely see don't appeal to me as much as showpiece objects, very distant objects, and globular clusters of all kinds.

I have friends who take delight in seeing objects or features that I can barely see and which I wonder if I am really seeing. I like to be sure I am really seeing the object, not just imagining it. But everyone is different.

It must be thrilling to be one of only a handful of people on the planet who have seen a specific object.

The meaning of what I am seeing is important to me also. Looking through
Baade's Window at 6522 and 6528 close to the center of our galaxy is inspiring.

Bill


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csrlice12
Postmaster
*****

Reged: 05/22/12

Loc: Denver, CO
Re: Big dob for objects with structure and detail? new [Re: auriga]
      #5912652 - 06/10/13 09:28 AM

M8, "Lagoon Nebula" is a really nice view, especailly with an OIII filter....

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bobhen
professor emeritus


Reged: 06/25/05

Re: Big dob for objects with structure and detail? new [Re: robininni]
      #5912675 - 06/10/13 09:44 AM

All I care about is seeing more detail in already detailed structures like m51. So I'm wondering if 25" of aperture is overkill for me because I'm just not hardcore and like looking a 'pretty things'?







Rob

You show a Mallincam Video Camera in your signature. Any reason you are not using the Mallincam with, say, a C8 or C11 to see the fine detail in deep sky objects that you crave but canít see visually with even a 25-inch scope?

If the object isnít showing enough detail for you in the Mallincam after 15-50 seconds, your next step is acquiring time on the Hubble.

Bob


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RAKing
Postmaster
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Reged: 12/28/07

Loc: West of the D.C. Nebula
Re: Big dob for objects with structure and detail? new [Re: astrokwang2]
      #5912703 - 06/10/13 10:02 AM

For me, it hasn't been the equipment as much as it has been the experience. I have owned everything from 15 inches down to 3 inches and even though my equipment has improved over the years, my eyes and expectations have improved even more.

Every object looks different every night - and that's one reason I keep going out.

Cheers,

Ron


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robininni
scholastic sledgehammer


Reged: 04/18/11

Loc: Stephenville, TX
Re: Big dob for objects with structure and detail? new [Re: bobhen]
      #5912705 - 06/10/13 10:04 AM

Quote:

All I care about is seeing more detail in already detailed structures like m51. So I'm wondering if 25" of aperture is overkill for me because I'm just not hardcore and like looking a 'pretty things'?







Rob

You show a Mallincam Video Camera in your signature. Any reason you are not using the Mallincam with, say, a C8 or C11 to see the fine detail in deep sky objects that you crave but canít see visually with even a 25-inch scope?

If the object isnít showing enough detail for you in the Mallincam after 15-50 seconds, your next step is acquiring time on the Hubble.

Bob




Bob,

Yes the reason I don't use my Mallincam currently is I have my c-11 setup for astrophotography and, more importantly, I have found that each time I have used the Mallincam, it is luke warm---giving a somewhat bland performance compared to astrophotography or visual alone. Let me explain:

In my mind, astrophotography with even minimal processing blows away the Mallincam in clarity, color, detail, etc. At the other end of the spectrum, visual has a very special 'oneness' associated with it that when removed from the eyepiece I lose. It also is especially clear and crisp, just not at the detail level I would like usually. So with a Mallincam, I get something in the middle of both which is unappealing to me. I'll probably sell the Mallincam, I just haven't gotten around to doing so.

Rob


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alexvh
sage


Reged: 07/29/07

Loc: South Africa
Re: Big dob for objects with structure and detail? new [Re: GlennLeDrew]
      #5913326 - 06/10/13 03:11 PM

Quote:

Much of what facilitates the detection of detail in extended objects is surface brightness. For example, compare 0.7 arcminute Jupiter with a common 10 arcminute galaxy. Even though the latter has 200 times the surface area of the former, it presents but a *fraction* of the detail. In spite of the fact that the galaxy has much detail to similar contrast and scale. If we could magically bring the galaxy up to the surface brightness of Jupiter, the detail seen would be simply staggering!

It's our lousy resolving power at low light levels which is the hindrance. And no telescope can present an image having surface brightness higher than delivered by a smaller scope--and even the unaided eye. The bigger scope merely allows to magnify detail while preserving surface brightness.




So at the same magnification M31 will look the same regardless of aperture?


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Jarad
Postmaster
*****

Reged: 04/28/03

Loc: Atlanta, GA
Re: Big dob for objects with structure and detail? new [Re: alexvh]
      #5913362 - 06/10/13 03:24 PM

No, it will look brighter at the same mag. But it will probably look better by increasing the mag and keeping the brightness about the same.

Jarad


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Thomas Karpf
Carpal Tunnel


Reged: 02/09/09

Loc: Newington, CT
Re: Big dob for objects with structure and detail? new [Re: alexvh]
      #5913403 - 06/10/13 03:42 PM

Quote:

So at the same magnification M31 will look the same regardless of aperture?




No. At BRIGHTEST (i.e. using an eyepiece that gives you a 7mm exit pupil), M31 will be the same brightness per square degree as your naked eye view. The difference is, naked-eye, M31 covers perhaps six square degrees. At 10x, it covers six HUNDRED square degrees. At 20x, it covers twenty four HUNDRED square degrees and fills your field of view.

Using a bigger scope allows you to create a larger image at the same surface brightness. The bigger the scope, the bigger the image can be at your eye.


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csrlice12
Postmaster
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Reged: 05/22/12

Loc: Denver, CO
Re: Big dob for objects with structure and detail? new [Re: Thomas Karpf]
      #5913505 - 06/10/13 04:22 PM

Just realize that at a certain point, the FOV of a dob might be too small to "see" the entire object. Like M31, a fast short wide-field refractor(i.e. f5 like the ST80) with a low power eyepiece would be better then a big powerful dob. Sometimes raw power isn't enough......and I'm a real dob fan....

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Thomas Karpf
Carpal Tunnel


Reged: 02/09/09

Loc: Newington, CT
Re: Big dob for objects with structure and detail? new [Re: csrlice12]
      #5913564 - 06/10/13 04:48 PM

The maximum field of view can be visualized by imagining a long skinny triangle with it's base as the clear aperture of the focuser and the length as the focal length of the scope.

With a 2" focyser, if the scope's focal length > 920mm (about 36", or a 6" f/6), then M31 will not fit in the field of view.


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GlennLeDrew
Postmaster
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Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: Big dob for objects with structure and detail? new [Re: Thomas Karpf]
      #5913761 - 06/10/13 06:45 PM

To amplify on the visual aspect of an extended object (M31 was specified) at *constant magnification* while changing aperture...

As we decrease aperture from that which provides the largest useable exit pupil, the view decreases in surface brightness. Our visual system's resolving power decreases, and its noise increases. Details formerly visible (such as the pair of prominent dust lanes on the NW side) become progressively more difficult to distinguish. Then the fainter outer portions of the galaxy become lost in the noise. Then the moderately bright intermediate regions of the disk fade out. Continuing to reduce aperture (and hence exit pupil diameter) will continue to diminish the visible extent of the bright central bulge, until only the tiny core is all that remains.

This illustrates the fact that small apertures cannot do at high power what a large aperture can do at what for it is low power. This aspect of optical performance is most pronounced in the low brightness regime, where the eye's own resolving power is dictated very strongly by scene surface brightness and contrast.

Let's explore matters at constant aperture.

Where objects are bright enough for our eyes to work in the photopic regime at even small exit pupils, the detail we see scales pretty much linearly with magnification (until diffraction becomes resolved.)

But for most extended DSOs, detail perceived does not scale linearly with magnification. As power is increased, the dimmer view causes a loss in our eye's resolving power. And so detail improves at a smaller rate than expected. As the exit pupil continues to shrink, the rate of improvement in detail perceived ever more rapidly worsens. Eventually a turnover point is reached where the amount of detail actually *decreases* with increasing magnification. At just what point this occurs depends critically on the scene contrast. A very low contrast object such as the Cave nebula does not bear magnification well. But high surface brightness planetary nebula NGC 6543 in Draco can withstand 'crazy high' magnification by comparison.


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aatt
sage


Reged: 07/26/12

Loc: CT
Re: Big dob for objects with structure and detail? new [Re: GlennLeDrew]
      #5914171 - 06/10/13 10:18 PM

I have had a 15' for about a year now and although it was a little anticlimatic at first, I am now really appreciating the benefits of increased aperture.It is great to see so many galaxies that my 6" could not even capture-the celestial smorgasbord is now there for the taking. Teasing out those galaxy details is definitely a work in progress. I am much better now than I was a year ago and I have found that prolonged study of a single object is the best way to hone those detail skills, rather than hopping from one faint puff to another.I just got the scope out to a green zone for the first time last week and although the seeing was poor, the visual transformation of some of the brighter galaxies was tremendous.Patient study and darker skies are part of the ticket. The rest is passion and perseverance-and all the little techniques folks here talk about. The payoffs keep coming if you keep at it.

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