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Observing >> Deep Sky Observing

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Tony Flanders
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Re: Mallincam Xtreme vs large dobs new [Re: Ira]
      #5581955 - 12/21/12 07:08 AM

Quote:

M51, the Whirlpool Galaxy. In my C8 under dark desert skies this barely shows as two bright smudges at the core of the Whirlpool and its companion.




You need to work on it more. M51's spiral arms are definitely visible through an 8-inch scope under dark skies. Not even difficult once you understand what they look like. The key is to concentrate on the dark areas inside what at first looks like a uniform circle of light.


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Astrojensen
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Re: Mallincam Xtreme vs large dobs new [Re: Tony Flanders]
      #5582036 - 12/21/12 08:28 AM

Quote:

M51's spiral arms are definitely visible through an 8-inch scope under dark skies. Not even difficult once you understand what they look like. The key is to concentrate on the dark areas inside what at first looks like a uniform circle of light.




Yup. Like this:



Observed with my 150mm f/8 Sky-Watcher achro. Baader Maxbright bino, magnifications 30x, 60x, 80x and 120x. SQM 21.4. Somewhat hazy. NELM about 6. Image best at 60x.


Clear skies!
Thomas, Denmark


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jgraham
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Re: Mallincam Xtreme vs large dobs new [Re: Astrojensen]
      #5582099 - 12/21/12 09:07 AM

“I am trying to compare what is visible in my Mallincam Vs. what size scope I would need to experience the same thing in an eyepiece…”

Hmmm, I’ve been using my cameras to observe with for the past 10 years and I came to the conclusion that you can never see through the eyepiece what you ‘see’ with a camera, particularly a camera like the Mallincam. The specific issue with the Mallincam is that there is so much in-camera processing that it can never match the natural appearance of an object. At best, the view provided by the Mallincam can provide some guidance as to what to look for through the eyepiece, and sometimes you’ll see new detail visually simply because you didn’t know that it was there. The closest that I’ve come to having a camera that approximately (very roughly) the visual experience is a monochrome camera where the only adjustments you make to the live image is brightness, no non-linear operations like curves, gamma, or contrast. Of course it’s fun to make those changes live to bring up faint detail, but that blows any equivalence to what you could see visually through any size telescope.

In the big picture, I used to consider my little Orion StarBlast (4.5” f/4) fitted with a live view camera (any of the Meade DSI/DSI Pro series cameras running Envisage) to be roughly equivalent to my 16.5” f/6.5 or my 16” f/4, but that’s not quite accurate. I can easily see far fainter with my StarBlast, but the view can never, ever, ever, ever, ever match what I see visually, the techniques are simply too different. The two methods of observing can complement each other very nicely, but I don’t think that you can ever compare them on an equal basis.

Enjoy your camera.


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IVM
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Re: Mallincam Xtreme vs large dobs new [Re: jgraham]
      #5582269 - 12/21/12 10:51 AM

I agree with Tony and Thomas regarding the arms in M51 (note though that the Mallincam image in the OP is very detailed). That's a great drawing, Thomas, and reminds me of the view I had ONCE with my 7" (minus the "bridge").

Since I already answered the real question in the OP as I could, and since the discussion has turned to theoretical matters, I may add that the way I see it, visual observing, traditional astrophotography (excruciatingly long exposures and lengthy off-line processing), and live or quasi-live photography (digital or analog short-exposure CCD, displayed as video or stacked in real time) are three different hobbies. I have done a little bit of each, and so far settled on visual for its especial tranquility, its especially human challenge, and to make the most of my access to good dark locations. In all three hobbies, however, the main attraction (besides the technology per se and the elements of personal challenge and even competition) is to make the cosmic wonders materialize before your eyes through your own observational efforts. (Professional observational astronomy was defined as visual and is now defined as CCDing.) Thus all three hobbies are instrumented observation and are similar in the most fundamental way and different from the (also worthwhile) hobby of “armchair astronomy”, where one browses through images made by others or watches live observational broadcasts set up by others.


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bobhen
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Re: Mallincam Xtreme vs large dobs new [Re: IVM]
      #5582402 - 12/21/12 12:22 PM

There’s an excellent article about video astronomy in the February issue of S&T (I get the digital issue so I already have February). The article is written by Rod Mollise. All the virtues, the whys, and the advantages that video observing offers, are explained in-depth. Rod’s blog also has a few articles on video astronomy that are also well written.

Bob


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starrancher
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Re: Mallincam Xtreme vs large dobs new [Re: Tony Flanders]
      #5582761 - 12/21/12 04:23 PM

All the detail in the images posted above , aside from any color , I have achieved through Plossl eyepieces in an 8 inch under a pristine sky , without having the overexposed galactic cores etc ruining the true view . M51 and it's spiral arms show every bit as good as this camera image in this situation . If one refuses to get out from under the light done , then I guess it increases what can be seen , but the over bloated cores don't do the image any justice . I'll take the color free image through the eyepiece and leave the abominated images behind with a bit of money for the fuel tank if needed .

Edited by starrancher (12/21/12 04:35 PM)


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GlennLeDrew
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Re: Mallincam Xtreme vs large dobs new [Re: starrancher]
      #5582849 - 12/21/12 05:06 PM

The gains afforded by a low-resolution video camera apply more to extended objects. And the lower the object surface brightness, the greater the disparity between what is imaged and what can be seen. A target like the brighter, inner parts of M42 can be just about as well seen visually through the same scope as when imaged. But the outermost bits are definitely more readily discerned via the camera. And really dim stuff, like the notorius Cave nebula, will require for a visual equivalence an aperture *at least* 5X larger.

The awfully poor resolution of the eye at low brightness and contrast levels is the limiter. In this comparison aspect, detection alone is not enough. Glimpsing a mostly formless haze with something approaching averted imagination is not in the same league as easily discerning details well more than 10X finer than the eye could possibly make out.

And in that vein, the aforementioned comparison between the image and drawing of M51 (a not extremely dim object at all) still puts the image well ahead in terms of fineness of detail easily seen vs that which pushes the eye to its limit.

Part of the equation must include the *ease* with which the details are seen. The briefest glance at a screen, or prolonged scrutiny of a view in which visual system noise is striving to subsume what there is to see. That difference has got to count for something.


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Dwight J
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Re: Mallincam Xtreme vs large dobs new [Re: GlennLeDrew]
      #5582984 - 12/21/12 06:21 PM

The advantage the eye has over the Mallincam is in viewing a wider range of brightness ie: the Orion nebula. The camera burns out the centre of the nebula when you attempt to catch the fainter outer portions. Visually I have seen the core and the faint outer regions simultaneously, not possible with a Mallincam. M31 is another example. Viewing the HorseHead, on the other hand, is child's play in virtually any sized scope with a Mallincam. I strained to see it visually using a H-beta filter and a 16" Newtonian. M51 was great in the 16 (just had had the mirror recoated and a smaller 96% secondary installed at the time). This was after hauling it out to a pristine dark sky site and high elevation and much younger eyes. Where the Mallincam really shines is showing deep sky objects using a relatively small scope from my light polluted back yard while I enjoy the view from my heated shed during -20C nights.

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george golitzin
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Re: Mallincam Xtreme vs large dobs new [Re: Dwight J]
      #5583500 - 12/22/12 01:38 AM

Very true what Dwight said about dynamic range--I was thinking the same as I looked at the OP's mallincam images. The detail on M51 and the arms on M81 were comparable in those images to what I saw in my 16-inch, and close to what I see in my 18-inch--but I like the view much more in my dobs, because of the greater dynamic range my eye enjoys.

But for showing someone--a school group, for example--details in DSOs from an LP site, the Mallincam seems a very valuable tool.

-George


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bobhen
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Re: Mallincam Xtreme vs large dobs new [Re: george golitzin]
      #5583816 - 12/22/12 10:15 AM

The images presented here are in NO way indicative of what is seen on the screen. Read Rod’s article in S&T and take a look at the accompanying images – they are very CCD-like.

There is no way that you will see anything even remotely close to the detail in a video image of M51 that you will see in ANY amateur scope – even the largest under the darkest sky – not even close. And you can see this CCD-like detail in 20 to 45 seconds. The horse head nebula, the dust lane in 891 with its feathery edges, the outer shell of the bubble nebula, the pillars of creation in M16, are all easy targets that show tremendous CCD-like detail without using averted imagination and with an 11-inch SCT and a 45-second exposure. And these can all be seen in the most horrendous light pollution that you can imagine. There’s no need to travel anywhere or limit your deep-sky observing because of travel or time limitations or even because of the full moon.

Yes it is true that the core of M42 will be blown out if you want to see CCD-like detail in the outer nebulas regions BUT if you want to see the core just take a 5-second exposure and you will see sharp detail in the core of M42 that no amateur scope of any size will show. So for M42 it does take 2 exposures – just like you would need 2 different eyepieces to get different views of the same object.

Question: I presume people buy large telescopes so that they can see fainter objects and see more detail in brighter objects. If that’s why you bought a telescope, then you would be better served with an 8-inch SCT and a video camera than you would be using any large Dobsonian. If your goal is to somehow commune with nature or the night sky or some other esoteric activity then you can certainly get that same “feeling” by just standing out under the Milky Way in a dark sky BUT, of course, you don’t need a telescope at all for that.

If finding these objects is fun for you then give up the GOTO and stick with visual. BUT finding is not seeing detail and seeing detail is what we are talking about.

Eyepieces and telescopes are tools for seeing faint and distant objects - nothing more. And the video camera (with a simple 6-11-inch telescope) with its near real-time views is a better tool for achieving that goal than is the large-mirror Dobsonian. Besides, if you get tired of seeing all that detail you can always take the video camera out. BUT if you are looking for a cure for aperture fever (which is really just the quest to see more and deeper by gathering more light) then that cure is spelled VIDEO.

Bob


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nytecam
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Re: Mallincam Xtreme vs large dobs new [Re: Ira]
      #5583838 - 12/22/12 10:37 AM Attachment (32 downloads)

Thanks to our DSO visual observer friends hosting this topic and excellent images Ira from, I presume, from near perfect desert skies. With >8M neighbours here in London I don't have the luxury of dark skies but my SX Lodestar-C can match your Mallincam any day - M43 below in 20s exp for comparison. For DSOs some visual-assist is essential hereabouts

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Astrojensen
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Re: Mallincam Xtreme vs large dobs new [Re: bobhen]
      #5583844 - 12/22/12 10:42 AM

Quote:

I presume people buy large telescopes so that they can see fainter objects and see more detail in brighter objects. If that’s why you bought a telescope, then you would be better served with an 8-inch SCT and a video camera than you would be using any large Dobsonian. If your goal is to somehow commune with nature or the night sky or some other esoteric activity then you can certainly get that same “feeling” by just standing out under the Milky Way in a dark sky BUT, of course, you don’t need a telescope at all for that.




That is an oversimplification if there ever was one. It's partly true, in some cases, but there is MUCH more to visual astronomy than what meets the eye, so to speak.

Quote:

BUT if you are looking for a cure for aperture fever (which is really just the quest to see more and deeper by gathering more light) then that cure is spelled VIDEO.




Sorry, but no. The more deep images I see, the more I am hit by aperture fever, because I want to see these objects through a telescope, directly, not through a camera. There is a dynamic range in the real, live view through an eyepiece, that the camera and screen can't match. Some day it can, perhaps, but not yet.

Quote:

BUT finding is not seeing detail and seeing detail is what we are talking about.




That is precisely why we need a bigger scope! To see details with our own eyes. But again, it is an oversimplification. Seeing the maximum amount of detail is not always the most important thing. Best framing and best contrast for the prettiest view, for example, can make visual observing a real pleasure. I don't always hunt for maximum details.

Bottom line: Visual observing and astroimaging are so very different that they almost can't be compared. They also seem to cater to very different personalities. Visual for the poets and romantics, imaging for the analytical and logic minds.

None is more important than the other. We need both art and science.


Clear skies!
Thomas, Denmark


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IVM
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Reged: 01/07/08

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Re: Mallincam Xtreme vs large dobs new [Re: nytecam]
      #5583872 - 12/22/12 11:05 AM

Two problems with today's fast CCD/video technology are thick stars and the narrow dynamic range. The lack of "seamlessness" compared with pure optical setup could probably be disregarded; after all a truss Dob is not "seamless" at all to set up.

But blown stars spoil it all for me; even most heavily post-processed images have them. Also, the narrow dynamic range. The latter in practice is more often a function of the monitor device (LCD nowadays) than the camera. Regardless, it is the simultaneous presence of sharp (stars) and diffuse (nebulosity), and of a broad range of brightnesses that make the views through the eyepiece seem "out of this world". In truth the broad range of brightness is present in common daylight views, but in our terrestrial views it is hugely spread out spatially and we never focus on it.

As I had to remark with regret earlier on this forum, it seems to me that quantum mechanics teaches us that no observation can be "immediate" (i.e. that it cannot be said that the discrete photons we perceive were once certain discrete photons emitted by the object). So it is just the current limitations of CCD/video technology and attachment to certain unique aspects of the view through the eyepiece that do not permit me at this time to leave visual observing. More detail does not for me compensate for the low quality of the image. I use good photographs to guide my visual observations and help me see more than just the obvious.

EDIT: Having read Thomas's post above I feel compelled to add that I have thought of myself as an "analytical and logic mind"


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David Knisely
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Re: Mallincam Xtreme vs large dobs new [Re: nytecam]
      #5584113 - 12/22/12 01:35 PM

Nothing against using a camera to catch deep-sky objects, but by definition, it isn't really visual observing (anymore than taking out one of my large coffee table books of professional astro-images and looking at them). To get these images requires time exposures, as they are not exactly real-time video-like images, although the exposure times have gone down considerably from what they once were. I am kind of spoiled in terms of CCD imaging, as I have a friend who does them from a dark-sky site with his own observatory using some of the finest CCD cameras, mounts, and equipment available to the amateur today. He spends hours and hours capturing multiple images and stacking/processing them to obtain pictures which rival or exceed those produced by professionals. Those shown here with the Mallincam, while interesting, do not come even close to what my friend produces. I think that if I were to go the electronic route, I might be tempted to follow his example rather than go with a single-shot camera system. I don't like the hassle, but I do like the results. Clear skies to you.

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IVM
Pooh-Bah


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Re: Mallincam Xtreme vs large dobs new [Re: David Knisely]
      #5584210 - 12/22/12 02:40 PM

Not to pile on (and assuming that the original question has indeed been answered), one should mention specifically the issue of noise.

If I remember correctly, the intrinsic quantum efficiency of human receptor cells is around 60%, i.e. on the level of back-illuminated CCDs and 2-fold higher than in simple ones we amateurs use. The visual processing also allows effective integration on the scale of a few seconds. The reason we don't see like a video camera is heavy noise suppression that we humans cannot turn off. If you filter the under-1-min exposures so heavily as to match the unnoticeable levels of noise in the visual image, the contrast on the scale of typical galaxy arms will be suppressed almost to invisibility and details within the arms will be wiped out. To bring them back, stacking or multi-minute exposures will be necessary.

This is all imprecise and based on my rather limited experience, but I wanted to mention noise in addition to the bloated stars and dynamic range as the reasons I have not been doing much "real-time" imaging. But all this talk paradoxically makes me want to do it again soon


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nytecam
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Re: Mallincam Xtreme vs large dobs new [Re: David Knisely]
      #5584228 - 12/22/12 02:55 PM

Quote:

... I am kind of spoiled in terms of CCD imaging, as I have a friend who does them from a dark-sky site with his own observatory using some of the finest CCD cameras, mounts, and equipment available to the amateur today.... I think that if I were to go the electronic route, I might be tempted to follow his example rather than go with a single-shot camera system.


David - when [or more probably - if] you do, I guarantee you'll get an immense satisfaction from your own efforts however modest which beats pro pictures books any day. I'm sure this applies to your visual observations. Some presume astronomy is an elite hobby reserved for those under perfect skies - I don't

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Lorence
scholastic sledgehammer


Reged: 09/15/08

Re: Mallincam Xtreme vs large dobs new [Re: george golitzin]
      #5584292 - 12/22/12 03:42 PM

Quote:

Very true what Dwight said about dynamic range--I was thinking the same as I looked at the OP's mallincam images.
-George




I haven't seen much talk about the dynamic range of our eyes. When I was twenty one I could see objects halfway to the edge of the universe.

I've been twenty one three times now. Every time those objects get further away and fainter. The last time I looked through an eyepiece all I could think was, "Sorry Mr. Bowman, it's not full of stars."

If I last long enough to be twenty one another time I'll still be seeing more than I was ever able to see at any of those previous twenty ones thanks to Mr. Mallin. I wonder how long it will be before he gets the credit he deserves for breathing some life back into this hobby.

It will be interesting to see what Rock will be building next. I've got Universe serial # 001. You can bet I'll be at the front of the line for the next one.


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Ira
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Re: Mallincam Xtreme vs large dobs new [Re: GlennLeDrew]
      #5584584 - 12/22/12 07:38 PM

Quote:

For nebulous objects of low surface brightness, the Mallincam makes visible details which would require for visual work an aperture at least five times larger.




Glenn,
This is my impression, too. Alot of the drawings don't show the arm detail that I was able to observe with my Mallincam. That makes my little C8 the equivalent of a 40" observatory instrument!

/Ira


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Ira
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Re: Mallincam Xtreme vs large dobs new [Re: starrancher]
      #5584589 - 12/22/12 07:40 PM

Quote:

I'll take my eyepiece view under pristine skies over the camera view all night long and twice on Sunday night .
There is something special about the eyepiece view that cannot be substituted by any other means .
The intimacy and tranquility of it all cannot be recreated with a camera .
Awestruck through the ocular . That's astronomy .




Starrancher,
Have you ever personally used a video camera for astronomy?

/Ira


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Ira
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Re: Mallincam Xtreme vs large dobs new [Re: mattflastro]
      #5584593 - 12/22/12 07:43 PM

Quote:

Perhaps your queston needs a bit of rephrasing . Instead of asking how much bigger needs the scope to be in order to see the same details visually as in the smaller scope using a Mallincam, the simpler question would be how much bigger needs the scope be in order to see anything at all . Compare minimum scope sizes that allow seeing certain objects visually and with the Mallincam. Forget about whether they look the same or different and if the subjective impression gives the same feeling etc. Just the plain and simple see vs. not see .




I would say that if I were to rephrase my question it would be, "How does what you SEE in your big dob compare to what I SEE with my C8/Mallincam combo." The experience is obviously not the same, but that's not what I was asking about. I realize that the wording my original post was fuzzy and could leave itself open to different interpretations.

/Ira


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