Mar 21 2015 11:54 AM by Gil V
Review: Starlight Instruments Direct Drive System
Mar 21 2015 11:31 AM by Maz929
Innovations Foresight On-Axis Guide and Starlig...
Mar 17 2015 08:25 AM by GazingSkyward
The Celestron C80 ‘ Regal’ Spotting scope. And...
Mar 21 2015 07:54 AM by waxinggibbous
Categories See All →
- CN Reports
- User Reviews
- How to . . .
- Observing Skills
- Astronomical History
- Optical Theory
- Vision and Related Experiments
- How to Gain the Support of your Family for your Astronomical Pursuits
- Evaluation Tips
- Special Events
- The Elements
- New Articles in [!monthname!]
- Telescope Articles
- Submit a Review / Article
- Monthly Guides
- Behind the Scenes
- About Us
- Copyright ©
- Terms & Conditions
- Tiny Eyes on the Skies
- From the Editor's Desk
- What's Up . . .
- The Light Cup Journals
- Who is this Super Light Cup?
- Cloudy Nights T-Shirts
- Imaging Contest
- Small Wonders
- Previous Imaging Contest Winners
- This Month's Skies
- Mike's Corner
- The Cloudy Nights Friends and Family Discount
- Uncle Rod's Astro Blog
- Fishing for Photons
- Binocular Universe
- Article Submissions
Collins I3 "System"
Voice your opinion about this subject in our forums
I would like to present for your consideration a departure in the way we look at nebula. I am hesitant to suggest that I have discovered anything as I would imagine that there are some others who have tried this concept in the past-.My only wish is to share the information with anyone interested in the hope that it may advance the way you visually enjoy nebulas, which, in most cases are limited to just a small handful with what is currently available to the amateur astronomer. I think that I can honestly say that with the proposed system described below, you will be able to see a 1000% improvement in your ability to view nebulas.
I am going to refer to the concept as the "system" for the purposes of this article. The system consists of two principal blocks, with an additional third block which is an enhancement to the system. The two essential items in the system are a high-gain image intensifier, the only one I know of that is currently being marketed is the Collins I3, the second essential item is a narrow-band Hydrogen-Alpha filter. There are a number of suppliers of this type of filter, the main criteria is that its pass-band be less than 15 nm wide. In case you have no experience with this type of filter, this is a filter that is used exclusively for astrophotography. These filters, until now, were completely useless for real-time observations. The filter I use is a Schuler 9 nm Hydrogen-Alpha filter. I also have a 6 nm Astronomics filter which works very well with a very slight reduction in brightness. The third element of the system, which is optional, is a focal-reducer/field flattener. There are a number of manufacturers who supply these as well. I use a Denkmeier Star-sweeper. What this accomplishes in the over-all scheme is a reduction in the focal ratio on my scope from an f4 to about an f3. For normal visual use, this would be meaningless because of how your eye adapts to light, but with the I3, which acts like a real-time camera, it makes a noticeable improvement. The system works well without the focal reducer, but if the object is to see as much as you can-then push the envelope.
The Methodology of the "System"
The system is basically tow elements which function very well together, which by themselves either perform poorly on nebula or not at all. Let's look at the system components. The Collins I3 is a real-time image intensifier, using technology which was developed for the armed services for the purposes of night vision. The latest technology in this field is an amplification system capable of amplifying light by as much as 50,000 times. Like most amplification systems, reality is much less, mostly due to various losses in the transformation of energy from one state to another. There is also the factors raised by the amplification of the light you want as opposed to the amplification of the light that you don't want. This is generally described in terms of signal-to-noise ratio. This is usually expressed in dB. In the case of the latest thin-film I3 technology, we are talking about signal-to-noise ratios on the order of 25 dB. That is essentially a two and a half magnitude increase. I don't know exactly how that would correlate to the visual intensity of the object you were trying to observe. If it were a direct 1 to 1 correlation, you would be able to see objects 2.5 magnitudes lower than before. Which would be greater than the doubling of the aperture of the instrument you were viewing with. Not a bad return on your investment. But-there are many factors involved in this system and the actual return for your effort could far outweigh the simple doubling of aperture. My experience has lead me to believe that in some instances, you will see images with the "system" that simply could not be visually observed with 100 inches of aperture, let alone a doubling or tripling. Later on in this piece, I will describe things that I can see with the "system" that are totally imperceptible with out it.
Back to the methodology. The I3 has gain, we have established that. In all of your conventional viewing systems, you really are simply trying to minimize losses. You do have gain of sorts, although it is passive, by the concentration of light from a large aperture being focused into the much smaller pupil of your eye. But-in most portions of a conventional system you are trying to minimize the amount of lost light and stray light and trying to maintain the same concentration of a wide bandwidth of light all focusing on a single small point, hopefully, exactly the same. With a conventional telescope and eyepiece, the corrective coatings, the amount of reflectivity of the mirror, the amount of baffling, even the different kinds of glass used in the lenses, all play a big part in reducing the loss of light as well as the integrity of the color that arrives at your pupil. Since light bends differently at different frequencies, this is not as easy to do as it sounds. It requires many corrections both reflectively and optically in order to get an image that we would refer to as "color free". Fortunately with the "system", the issue of color free is not even on the table. We have narrowed the bandwidth by a factor of 50 or more. We have concentrated on a very tiny portion of the visual spectrum which, interestingly, gives us two great advantages, first, the tiny portion of spectrum which is Hydrogen-Alpha carries the vast majority of detail information in the luminance portion of an astrophotograph. Most of your expert astro-photogropher's use narrow Hydrogen-Alpha filters to bring out the detail in their nebula pictures. Look at almost any nebula shot by Russell Corman, Robert Gendler, or Ken Crawford, just to mention a few-they all use narrow Hydrogen-Alpha filters to capture the luminance detail in the image. The wispy, cloudy detail in virtually all nebula are principally in the Hydrogen-Alpha region. Putting this filter in front of a 25 dB gain block gives you amazing detail, as well as allowing you to see portions of the nebula you've never seen before. Then there is the improved signal-to-noise factor that you benefit from simply by reducing the bandwidth. Signal-to-noise is inversely proportional to bandwidth. It takes a much larger signal to give you the same signal-to-noise ratio in a wideband reception situation as it does in a narrowband situation. It would require the slide-rule-types to figure out exactly what that improvement equates to, but-there are several dB to be gained simply by narrowing the band pass of light. There is also a small price to pay in that your intensifier tube is starting out with a lower level of protons to work with, and is thus working closer to the noise floor than it was before. One more factor comes into play here, and this one is one that you would not ordinarily think of. The I3 has an automatic gain control, or as the tekies call it, an AGC. What this means is that when a strong signal enters the band pass of the I3, such as a bright star, the gain automatically throttles down to keep it from being over driven. What this does is reduces the amount of gain available for all of the information within the eyepiece, therefore, the much lower level information is also reduced by the same amount. Lower gain, less wanted information. The Hydrogen-Alpha filter has an enormous roll to play here, if you recall, the people among us that like to look at the sun use a very narrow Hydrogen-Alpha filter system to observe the sun directly, in most cases a small fraction of a nm in width, sometimes as little as 0.05 nm or less. The sun puts out almost no energy in the Hydrogen-Alpha region of the spectrum. That is why these very narrow Hydrogen-Alpha filters are used for solar observation allowing you to use fairly large aperture telescopes to look directly at the sun. which viewed without the filter would damage your eye and even damage the scope. What does this have to do with the system? I'll tell you. First off, when you look at a nebula through the system, the stars (suns, if you will) are attenuated by as much as 20 dB or more and thus the gain of the I3 is ramped up, compensating for the lack of bright stars in the field to the point that the nebulosity comes booming through. If you have ever looked at the black and white Hydrogen-Alpha photographs on the web or in magazines, you will notice something else you may not have paid attention to before. The number and size of the stars in the image are dramatically reduced. The reason should now be obvious, they are not there as bright or in as large a number because they have been attenuated by the Hydrogen-Alpha filter. This unique combination of light gain, filtering and manipulating of the AGC all working together to give you an image that simply cannot be replicated in any other way, with the exception of long exposure photography.
The third element of the system is simply increasing the signal to noise ratio further by reducing the f ratio of the telescope. Any focal reducer should accomplish this to one degree or another. It is very common to use a reducer on a refractor or a catadoptic reflector, but quite uncommon to use a reducer on a Newtonian. It usually isn't even necessary for most Newtonians because their f ratio is usually below f6 or f7 and the eye, which is very adaptable, has a way of making the view an f6 Newtonian, look the same as an f4. The only difference is the f6 image is magnified a bit more and the object is larger in the eyepiece. The eye compensates for the focal length difference in light levels. The I3 does not-just like a camera, the f ratio of the scope is critical to the brightness of the image, either on the CCD screen or a photograph or in this case a phosphorus screen. If you change a camera from f4 to f5.6, one f-stop, you must double the amount of exposure time in order to get the same image on film. Sounds pretty brutal but the I3 is no different, since you are working in real-time, you don't have the luxury of increasing the exposure time, which simply means you take a loss in brightness equivalent to what would amount to a doubling of the exposure time if this were film. Just think, going from f4 at 1 hour would require 2 hours at f5.6. Therefore, when you use any scope with the system, be it a SCT, RC, Newtonian, Refractor or any variation of the above, you will want to reduce the focal ratio if you can. In some cases you may have issues with back-focus and vignetting as well as other problems, those will need to be dealt with on a case by case basis. The system is not dependent on the Denkmeyer Star-sweeper or any particular focal reducer, the object of this part of the system is simply to reduce the focal ratio anyway you can without suffering anymore field curvature, vignetting, or color distortion than is absolutely necessary. In the case of the Denkmeyer Star-sweeper, I was pleasantly surprised to see a considerable improvement of the field with respect to flatness, very comparable to what I get with my paracorr.
I just recently tried something out of curiosity. I plugged in a standard 25 mm eyepiece and screwed on the narrow Hydrogen-Alpha filter as I pointed the 20" scope toward M42. With the 20" scope M42 is very bright. It literally jumps out of the eyepiece. With the Hydrogen-Alpha filter in place I could see absolutely nothing. It was pitch dark. I thought I would be able to see at least a very faint image peek through-but absolutely nothing. Then I screwed the same filter on the I3 and put it in the focuser-what an amazing difference. There was a bright nebula with all the wispy detail of a Hydrogen-Alpha long exposure photograph. I am talking about the whole M42 image where the cloudy structure comes down to a point at the far end, along with the beautiful detail of M43 and the dark areas as well as the trapezium, with it' molten detail. This view of M42 is something no standard eyepiece can come close to.
So What Can You See?
I have been working with the "system" for almost 9 months now, and have had a chance to see virtually all of the different nebula that passed overhead in a full years time.
The answer to this question is really very close to "everything". There are a few objects that simply defy any visual observation but the list is very small. We have taken "The Sky 6" and scrounged for nebula that no one ever really talks about seeing and when you plug in the NGC or IC number or even the Able catalogue or some of the other exotic catalogues that you probably never even thought of looking at because you had trouble with half of the Messier objects, let alone delving into some of the really faint objects at magnitudes of 12, 13, ore even 14th and 15th. We've seen them. The I3 with out the filter will bring some of the brighter nebula to view, but to a very limited extent. It also seems to have a lot to do with the number of bright stars in the field. Don't forget the AGC, which is pushing down the gain and thus leaving most of the nebulosity completely out of the eyepiece.
I started using the system in April 2006. The first thing that I looked at is the first thing anyone looks at in the spring just after sunset, M42. There is was. With the "system" it seemed almost as bright as it does without the filter, but the degree of detail in the nebulosity was indescribable. No comparison between the conventional eyepiece and the system. The detail in M43 was also indescribable-I could even see the running-man. I have never visually seen that before. Then in almost a dared action I moved up to the flame, a nebula that I have enjoyed on many occasions without the "system". But where was the horse-head which had eluded me up until that moment. I had tried a 31 mm Nagler lens with a Hydrogen-beta visual filter, while trying to optimize my dark vision and did my best to use what I later began to call my "averted imagination" to try and see this elusive site, with absolutely no success. I had other more experienced astronomers looking in my eyepiece on my scope and saying to me-"there it is right there in the center of the eyepiece-can't you see it?" And, try as I may, it simply was not there. I really think I gave it as good a try as anyone could without any success-so needless to say I was quite apprehensive about what to expect with this brand new "system". I moved down from the flame and to my surprise, not only could I see it, I could see the wispy clouds behind it that illuminated it from the back-it looked just like the photos where it looks like vapors that were rising behind the horse head. It was so unbelievable that I ran into the house to get my wife, who cares about these things about as much as she cares about drag-racing or a good football game. I first showed her a picture in a magazine of the horse-head and then I took her to the eyepiece and had her look, she saw it as plain as day-a two year old could have seen it, it was that clear and although you would not call it "bright" you would neither describe it as dim or faint-it was there.
I have looked at the horse-head with a 16" Dob and a 13" Dob from my driveway in Simi Valley with bright street lights only about 30 degrees off axis. Another benefit of the system, it almost eliminates light pollution from local lights, although bright background sky's does attenuate performance to some degree. Then I took out a 10" LX200 and the f6.3 reducer and the "system"-the horse-head was still quite a view. I have looked at the horse-head and the flame together, although much smaller in a 4" FSQ 106. I did not use the focal reducer as there isn't enough back-focus in the FSQ. But with the straight I3 and Hydrogen-Alpha filter it was spectacular. The next dark of the moon, I brought up a 3 inch Orion refractor to see if I could still see it. There is was, just slightly dimmer and smaller but completely visible. How many of you reading this have ever seen the Horse-head with a 3" refractor? I doubt that there are many shaking their heads yes to that one. In each of these viewings I tried to see anything with a conventional eyepiece and in no instances could I see anything-not even the flame except with the 20" the flame came through very dim but discernable, but absolutely no horse-head. My viewing partner had the identical experience in every case. I consider the horse-head the true test of the system-but I will now go through some of the other nebulas in the sky.
I will describe what I have since done with the system over the past 9 months. I moved over to the Rosette. There it was with the dark details, but I could only see a portion of it at a time with the 20", later I would see the entire donut with the FSQ. The detail was somewhat reduced with the FSQ but looked exactly like the photographs. Then I moved the scope over to the cone. I could pull the cone out of the nebulous patch of clouds. The actual cone came through as a dark arrow shaped void in the nebulosity with a bright spot at the tip of the point. You could also see the cloudy "foxy" details in the remainder of the nebula. I missed the witch-head in the spring of 2006 but tried to catch it that winter. No luck-this is the only nebula that I have found will not pop through, even though you can see some nebulosity in the area, you can not make out the shape of a witch-head. I also tried it with the FSQ since it is so large-but it just wasn't there.
Thor's Helmet was absolutely stunning, and much larger than I had expected, but for that matter, so was the Horse-head. It was now June 2006 and I was anxious to see Sagittarius come up because it has so many interesting nebula, but the one everyone wants to see is the eagle. I pulled up the eagle on June 24th and almost fell off my chair. The detail in the eagle is absolutely unbelievable. You can see the three pillars very well defined and with almost the same contrast as you see them in a black-and-white Hydrogen-Alpha photograph. It was breathtaking. The next dark of the moon I took the system to Mt. Pinos where I spent the evening with Steve Kennedy and his 28" Dob. Many of you know who Steve is, He is one of the foremost mirror makers in the world. And his personal 28" scope is a masterpiece. He is somewhat of a purest like a few others that were on the mountain that night, a number of which liked the conventional view through their lenses better than the "system", but when it came to M16, even Steve was impressed and spent a very long time looking at the pillars and commenting how he had never seen them that good before. With 28" of light gathering and the "system" the eagle just jumps out at you, plus you move in closer so the actual pillars are bigger and you can see even more detail. The brightness with his 28" and my 20" were about the same, but that may be because we could not use the star sweeper to bring the focal ratio down another f stop because we ran out of back focus. Back focus with the system is, at times, a real problem, and in many cases, adjustments need to be made so that you can accommodate the system and still come to focus, much like a pair of bino-viewers. We also looked at a whole list of objects including M8, absolutely stunning, much more detail than with conventional eyepieces and three or four times as wide, literally two or three eyepieces wide. M17 was stunning, much much more detailed than with any conventional eyepiece. M20 was breathtaking but you could just faintly see some of the nebulosity in the blue region. The red portion was as pronounced as the best photograph you've ever seen of the object. The dark lanes in M20 were as crisp and detailed as any photograph, unlike conventional views. About this time Cygnus cleared the trees and the first thing we looked at was the Crescent. It was absolutely stunning, as detailed as any photograph. The North American Nebula was so big you could wander around it for hours looking at detail. The veil was as good as any photo you have ever seen. Interestingly, the veil comes through my 20" very nicely with a conventional eyepiece and an OIII filter, but the "system" view was equally impressive although it did look different. I would have to say that Steve Kennedy's 28" with a conventional eyepiece with an OIII filter was a breath taking experience and I think, in this case, I preferred the conventional view better than the "system" view but it wasn't because you could see more with one than the other, it was simply what looked more exciting in the eyepiece and the contrast with the totally black background of the conventional view simply was more impressive than the system, which by it's nature amplified the background light more and though it was much brighter, the contrast wasn't quit as good. Then we moved over to M27, The dumbbell was indescribable with the "system". You could see more detail than most of the long exposure photographs. It was very defined and a great deal of contrast. It almost seemed iridescent. It seemed to glow. One of the all time best views with the system is M27. Between the horse-head, M16 and M27, the three alone make the "system" worth having.
At this point is became time to push this a bit harder. We were all looking for a challenge. How about NGC 7193, a small planetary nebula at about 13.5 magnitude. A galaxy at 13th magnitude is hard, a nebula at 13th magnitude is simply not going to be there, but it was. It popped right into the eyepiece and showed all the detail that it had. I think it was better than the photographs I found on a number of different web sites. Then we tried NGC281, the Pac-Man. Never had been able to see the Pac-Man before with either the I3 by itself or with conventional lenses. It was not very bright but it was also low in the sky. I remember trying it later in the evening when it was higher and the brightness and contrast had improved quit a lot. How often have you observed the elephant's trunk in IC1396? If your honest, most of you probably have never seen it. It is difficult even with a 20" scope. But with the "system" I could follow the dark nebula right up to the eye opening at the top. It was stunning. You could see the nebulosity which seemed to go on forever surrounding this dark nebula. Then the Bubble, it was there in all it's glory, but by this time I had become overly confident and began to expect that anything I pointed to would be visible. So far there was only one no-show and that was the witch-head. I pointed at another 13th magnitude planetary nebula NGC 6445, you could see the box shaped nebula showing enough detail to make out it's character. In the next two or three months of dark moons I logged what must have been dozens of nebula, most of which were small planetary nebula. Including the cat's eye, the eye, the ant, even one nebula that according to the computer on my setting circles was NS354, which I could see but could never find much information on. I saw the California nebula well in the FSQ and pieces of it in the 20" as I panned over the whole thing. Late in the fall of 2006 I looked at M1 with the "system". This was very interesting since the previous views were before I had the Hydrogen-Alpha filter and it was simply a gray smudge, now with the system it had veins in it, much like the photographs. I found very few nebula that I couldn't see. By this time, the Horse-head had come up again and it is 9 months since I started with the system. I must confess that I have spent almost no time looking at globular clusters or galaxies for the past 9 months. The system does not work on anything but nebula and there are usually enough of them at any time of the year to simply fill the whole viewing night.
I know there are those who would look through the eyepiece of the "system" and then walk away complaining that it had ruined their night vision or complain about the greenish cast of the image or the sparkles (scintillation noise) and that they liked their tried and true conventional view of these objects. This is not for everyone, but, I have not found anyone who was not impressed with the Horse-head. You can never please everyone. If you already have an I3 and you have not tried a narrow Hydrogen-Alpha filter-you are missing out on the experience of you life. For less than $200 you can buy a good narrow Hydrogen-Alpha filter and I can promise, just the Horse-head alone is worth the $200. If you don't have an I3, it will be a more expensive experience for you-but still well worth it.
I hope each of you gets a chance at some point in your viewing life to look through an I3 with a narrow Hydrogen-Alpha filter (THE SYSTEM). It could very well change your way of looking at nebula forever.