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- iStar Optical’s Phantom FCL 140-6.5 review
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- FIELD TEST: THE NOH CT-20 ALT-AZ MOUNT
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Collins I3 Eyepiece (old and new)
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I have read previous reviews on the Collins I3 and have been quit frustrated with what the reviewers have said. I think the issue I have with the reviews I’ve seen is that they have not lived with the eyepiece. They only get one on loan for a few days. It is pretty hard to do an adequate review on a device as complex as the I3 with a few hours viewing. I have owned a Collins I3 for two years. I have slipped this eyepiece into a number of telescopes over that period of time as well as my own two Dob’s a Cassegrain and an FSQ. I have looked at many objects in a number of locations, and although I am a rank amateur astronomer, I know when I can see something and when I can’t. I should further qualify myself by saying that I am not a purest. I would much rather see an object…I mean really see an object, even though it has a slight greenish cast than to pretend to see it with “averted imagination”. I‘m aware that many have much more sensitive vision than I do.
Four years ago I picked up an Astronomy magazine and saw the beautiful pictures, bought an LX200 10” and put it in the back yard and then wondered where all the DSO’s were. Nothing looked like the pictures, actually most objects I pointed at didn’t look like anything except light polluted sky, nothing, zero, zilch. I know that I am not the only one to have this reaction. I’ve heard it many times.
Then the quest to actually see something began. I went to a large gathering on Mt. Pinos, north of Los Angeles, where there were between 50 and 100 scopes. I looked through as many as I could, one was a 20” f4 Dob…and the next day I got on Astromart looking for a 20” Dob. The owner of the one I found also just happened to have an I3. I had read the reviews, but hadn’t been impressed. After looking through it I bought the 20” and ordered an I3. The only way to get them away from me now would be to pry either the 20” or the I3 out of my cold dead hands. I am usually the only one at Mt. Pinos with an I3 and I’m easy to find… just look for the line behind the scope. To some, that might be a negative.
Both the older
I3 and the new Thin Film I3 have some common issues. I’ll go over them:
There is a greenish cast to the image. This is because of the light that is generated on the phosphor screen gives off a greenish cast. The thin film I3 has less noticeable coloration than the older unit. Is this a big deal? If you are a real purest, probably…but after a few minuets of viewing you never even notice it. The fact that you can now actually see that 13th magnitude galaxy might go a long way in helping you to overcome that green.
There is some scintillation (little sparkles in the background). The brighter the background sky, the more noticeable the sparkles. A really dark sky makes this almost a non-issue. The improvement between the original I3 and the Thin Film I3 is dramatic in this area. The signal-to-noise improvement in the I3-TF is about 5 dB on average, a major step in reducing the scintillation noise and also increasing the contrast. This is the principal difference between the older and the newer I3. Is the scintillation a big deal? Once again, if you are a real purest, probably…but after a few minuets of viewing, you won’t notice it either.
Some reviewers have reported that there are DSO’s you can’t see. This is true, and if you only read their reviews you may get the impression that there were are whole bunch of things you would be missing. This is not true. I haven’t gone through the whole IC and NGC catalogues but I can only come up with about a dozen things that can be seen with glass that can’t be seen with an I3. I’ll list the most notable ones, the horsehead, the veil, the running man, the packman. That’s about all that I can recall. All globular clusters are fantastic. Most planetary nebula are great, some of them are very small. Adding increasing power with a barlow has it’s disadvantages, I will discuss that in a moment. Virtually all galaxies are much better with the I3 than without it and most emission nebula are spectacular, except the ones that are almost totally in the blue region. Of course you don’t use the I3 on most planets although Uranus, Neptune and Pluto are ok. You have to be careful with any object that is much brighter than a 1.0, it won’t hurt the eyepiece for just a second or two, but you don’t want to leave it on something that bright or you will have a burn spot on your tube. The I3 shines in the red and inferred region and works best from the mid 500nms way out into inferred.
Some reviewers have mentioned a finite tube life for the I3. My 2 year old I3 is as bright as the day I bought it and the original battery is still in it and it has had plenty of use.
Some reviews have mentioned about the problem bringing the I3 into focus on some scopes. This can be a problem. On most Dobs, the mirror can simply be moved up a bit. There are corrective adapters that are used with bino-viewers which will help on both Dobs and refractors. I have one of those corrector lenses that I use with my FSQ and it solves most of the problems. Most Cassegrains don’t have issues with coming to focus with this eyepiece.
I have read a review that said the I3 is not for light polluted skies…andhave read a review that said this is where it really performs well. Who’s right? Neither. Most I3 owners have probably not even tried this, but put a H-Alpha filter on the I3 and you are now set for viewing in the city. It isn’t perfect, but it is absolutely 1000 times better than without the filter. I have not tried a real narrow H-Alpha filter. That is my next test. I purchased a Lumicon H-Alpha filter which is very wideband, which also works in a dark sky situation right after sunset. You will get at least 45 minuets more early viewing time with this combination than without it. Remove the filter after the sky gets nice and dark. I have a house in the suburbs and the H-Alpha filter is used almost all the time.
The I3 is like a camera and TV screen. You are not actually looking through the eyepiece. You are looking at a phosphor screen. First, the image is inverted. This is no big deal. Second, the f stop on a camera makes a mammoth difference in the brightness of the picture, so the f (focal length) of the telescope makes a mammoth difference in the brightness of the image on your I3. For instance, the difference between a 10” f4 and f11 scope will be quite pronounced. The f4 view will be noticeably brighter and you will see at least a magnitude deeper. This may break the hearts of the Cassegrain owners, but there are ways to improve on that too. Since the I3 acts like a camera and not like your eye, use the same techniques that astrophotogrophers use. A focal reducer brings that f11 scope down to f6 or so. Your field of view will be larger but you have now improved your signal to noise several dB and made the image quite a bit brighter. This also holds true in reverse, remember I said that using a Barlow is not always best. Obviously when you use a 2X Barlow you have doubled your f stop. A barlow still works but too much power will get to a point where the I3 is starved for protons and you may have very strange noise in the background. It is because the signal-to-noise ratio has taken a real beating. Remember this eyepiece has a gain of around 50,000. Starving the input means lots of little sparkles. Needless to say the new thin film I3 has less of all of these problems than the older model because it starts out with a 5 dB signal-to-noise improvement.
I have also read a review saying that the I3 works good on small scopes but when you get a big scope you are better off with a conventional eyepiece. WRONG, just plain wrong. The bigger the scope, and the faster the scope, the better the I3 performs. The difference between my 13” Dob and my 20” Dob with the I3 are quite impressive. I have plugged the I3 into a 28” f4 and looked at M17. It looked as good as a H-Alpha long exposure CCD image. Yes bigger is better and the I3 is no exception.
There is one other issue. Blooming of bright stars. If you have a star that is a mag. 2 or brighter, it will look larger on the screen that it should. It is relatively unimportant as you probably should not leave it on a star that bright anyway. The new I3-TF has less blooming than the older I3, but it is still happens.
Now to the comparison between the old I3 and the new Thin-Film I3.
The I3-TF’s main improvement is contrast. Spending about an hour on M42 going back and forth between the old and the new, you notice a dramatic improvement in the detail of the TF and you see a bit more of the cloud structure out to the far end of M42. The reason is the substantial reduction in the scintillation noise (sparkles). It looks like a good H-Alpha photograph. I tried this in the 4” FSQ, the 13” Dob and the 20” Dob. In all cases the signal to noise ratio of the TF was very noticeable in improved contrast. It isn’t that the old I3 lacked the detail, but when you improve the signal-to-noise by removing a lot of the scintillation noise you simply can see more detail. It, once again using the camera analogy, simply looked more detailed because even though this is real-time viewing, the image looked like you had doubled or tripled the exposure time, thus giving considerably more detail. I noticed this even more on faint nebula like the flame, which was quite dramatically enhanced in detail by the improved signal-to-noise of the I3-TF. Interestingly, the brightness of the object was the same in both eyepieces but the background was several shades darker in the TF with much less scintillation. It was like going from a magnitude 4 viewing sky to a magnitude 5 viewing sky. Not a bad improvement.
I haven’t seen many of my favorite DSO’s through the new TF I3 because it came to me after M8, M13,M16,M17,M20,M27, M57,M104, NGC4565, NGC253 and a whole bunch of others are gone for the season. After looking at M42 and NGC891 and a few other December objects, I have no doubt that the TF I3 will be even more spectacular than the older I3 on all of the above objects. The old I3 is breathtaking on all of them. Almost all globulars resolve to the core. M8 really looks like a black ’n white photo, On M16 you can see the three pillars very distinctly. M17 is unreal. M20 is stunning but you don’t see much of the blue portion. M27 is much like a good B&W photo and M57 is outstanding you can see the inner and outer edge of the ring and some of the spiral tails. M51 is absolutely wonderful. The arms are distinct in a dark sky, but don’t try this in your light polluted city lot, it takes a dark sky even with an H-Alpha filter. M82 is fantastic even in a light polluted sky with the H-Alpha filter and M104 looks like the photograph. The dust-lane and the detail are spectacular. NGC4565 and NGC253 are enough to give you goose-bumps. They look like the photos we’ve all seen in Sky & Telescope.
If I hadn’t found the I3 I think I would have given up the hobby. I wanted to see the pictures I had seen in magazines, and even with the 20” and a good Naglar I wasn’t seeing enough. Now, I can hardly wait for the dark of the moon so that I can drag this big contraption up to Mt. Pinos.
Would I buy the I3 again? That’s obvious. I now own the old one and the new one. I think the I3 is the best investment I’ve made in astronomy. It makes such a difference in my enjoyment of the hobby that I can’t imagine being without it. Don’t ask the question “will this eyepiece work well with my scope?” Instead, consider the I3 the central piece of equipment and then buy a scope that will work well with it along with the necessary additions like a good set of filters, including a deep sky, at least one good H-Alpha filter, a wide and a narrow if you can afford it, I haven’t tried an infrared filter but you could actually view in infrared visually if you wanted.
Obviously this is a big investment. For many it may even be out of reach. If I had the choice right now to buy a 12” Dob and the I3 or my 20”Dob and no I3, I would take the 12” in a heartbeat. And now you don’t have to choose between the old I3 and the new Thin Film I3. The new TF I3 is about the same price as I paid for my old I3.
What are you waiting for?
Simi Valley, CA