Battle of the Heavy Weights -- Night time
January 21, 1998
7:00 P.M. Mountain standard time
Scope: 10 inch f/4.5 left out earlier to cool down to the relatively warm 35 degree temperatures outside.
Seeing was above average. I was able to cleanly split the four main stars of the Trapezium of the Orion Nebula with every 30mm to 40mm widefield that I used. The weakness in the seeing was that I live in the Salt Lake valley, and I had some relatively serious skyglow to deal with from the city. With 7mm and 10.5mm Pentax XL's, I was able to sense Saturn's Cassini division, and clouds or bands on Saturn; but, I had diffraction spikes to the max due to the secondary's spiders. The main targets were the Orion Nebula and the Pleiades, favorite objects for wide field eyepieces. Note that due to sky glow, the wispiness of the nebulosity of the Orion Nebula was not a factor I could use for comparison. The wispiness was there among the light in some of the eyepieces, at times; but, nowhere near as dramatic as some of my visits to a dark sight. Nor was the nebulosity anywhere near as bright as it could have been out in the desert. The test was basically for the sharpness of the stars across the field of view, and to test for the most pleasant view in general.
A couple of general observations. First, these eyepieces almost all performed better at night than during the day giving me the general feeling that wide field low power eyepieces are probably designed for night time use. The Orion Nebula was my first target of observation. While splitting the Trapezium, it became somewhat clear that the 30mm eyepieces magnified more than the 40mm eyepieces (of course), which made it rather clear that the 30's should be compared with the 30's while the 40's should be compared with the 40's, at least on the Orion Nebula. I have become rather sensitive to shadows and light loss in the field of view. None of these eyepieces were perfect; they all had problems with shadows or light loss in the field of view, which was easily seen due to the sky glow from the city. There might not be as much to say about these eyepieces in the night time review because they almost all performed quite well in the dark. My initial gut impression was that there was no difference between the eyepieces; it took awhile to start seeing the differences in the eyepieces through the 10 inch scope on the star fields. In other words, eyepiece reviews can make the difference in eyepieces sound huge. But in actual practice, the differences were actually very subtle, especially at night on star fields. Differences were more noticable during the day and on the moon. In a pinch, on the star fields, most of the eyepieces can easily be used to get the job done -- just my opinion.
I compared the 40mm UO 7/70 with the 40mm Baader Erfle. The Baader had slightly sharper or pinpoint stars across the field of view. However, the scope's central obstruction was clearly visible in the field of view of the Baader as a huge floating central shadow or dimness to the center of the image. The ever present shadow in the 40mm Baader was severely annoying in comparison to the random shadows that sometimes appeared in the field of the 40mm UO 7/70. With my 10 inch scope, I would have to declare the 7/70 the winner despite the slightly sharper star field in the Baader. While viewing the Pleiades, it became somewhat noticable that the UO 7/70 had a wider field of view thus partially explaining why the stars would not be as pinpoint across the field of view. The UO 7/70 just showed more for those wanting a wider field.
I then compared the 38 Rini Modified Plossl to the 40mm eyepieces. The light loss that I experienced during the day just was not noticable during the night on the Orion Nebula, probably due to the sky glow of the city. Shadows were there, but not annoying. However, the 38 Rini just was not that sharp across the field while viewing the Pleiades. A lot of flare or bloating from the stars on the edge of the field.
For fun, I stuck in the UO 55mm Plossl. The central obstruction caused serious darkening in the center of the image making the eyepiece unusable as predicted from previous observations.
I stuck in the 85mm Rini Modified Plossl on the Orion Nebula. This eyepiece was a surprise. Yes, the central obstruction is visible. However, the range of focus is so huge that you can move the eyepiece far enough out of prime focus to make the central obstruction shadow literally disappear, but still have pinpoint stars; really interesting. Sky glow was a problem as far as giving any nice contrasty views to the huge image of the neighborhood around the Orion Nebula.
I then compared the 30 Leitz, 32 UO WideScan and the 32 UO Koenig in the 10 inch scope. Right from the start I must declare the 30 Leitz the clear winner; it just gives the best overall pleasing view on star fields. The worst during the day is the best during the night. Despite the random shadows in the field of view of the Leitz, the stars were the sharpest across the field, and the 88 degree field was huge and very pleasing while looking at star fields. The 32 UO Wide Scan was OK on the Orion Nebula, but on the Pleiades it became obvious that it had the least sharpness across the field of view of any eyepiece; it was even worse than the 38 Rini for sharpness across the field of view. Imagine a folding fan that can be opened a full 180 degrees. Take the fan and open it up a little over half way, say 100 degrees. The shape of the fan opened 100 degrees is what the stars around the edge or circumference look like in the 32 UO Wide Scan when the stars in the center are perfectly focused -- using the 32 WS eyepiece in my 10 inch f/4.5 The 32 UO Koenig was probably the sharpest across the field of view of the three eyepieces; but, it was wanting to fall apart around the edges (stars starting to bloat), something that took the Leitz huge distances from the center to do the same. I would have to give the 32 Koenig just average marks for star field performance, due to its narrow field of view; if the field were wider it would be horrible at the edges. Shadow problems of some form or another were visible in each 30mm eyepiece, but not really enough to be annoying on the star fields I tested. The 32 UO Koenig had smaller stars than the 30 Leitz or the 32 Wide Scan, an interesting effect. The stars in the 32 Koenig were small like in the 40mm eyepieces. The 32 UO Koenig also required that I rack the focuser 1.5 to 2 inches farther out in order to focus in comparison to all the other 30mm and 40mm eyepieces. On page 163 of "Telescope Optics" by Rutten and Van Venrooij the discussion of distortion aberration indicates that wide field eyepieces can in general be designed for daytime use or night time use, but not optimized for both daytime and night time use at the same time. I am now of the belief or guesstimate that the 32 Wide Scan was designed more for optimum daytime use at the expense of quality night time use; the 32 WS also had the least amount of annoying shadows during the day.
Conclusions on star fields. Of the bunch, the Leitz at $1000 is the best wide field eyepiece for night time viewing in my 10 inch scope. However, the overall view and sharpness were well approximated by the University Optics 40mm 7/70. Let's put this another way. The 40mm eyepieces tend to pinpoint stars due to lower magnification. Thus the sharpness across the field of the Leitz is well approximated by the 40mm eyepieces. For wideness of field, the 30 Leitz is well approximated by the UO 7/70 and the UO 32 Wide Scan. Of the 32 Wide Scan, 40mm Baader, and the 40mm 7/70, I had the least complaints during the night with the UO 7/70; so, I would declare the 40mm 7/70 as a good second place replacement for the 30mm Leitz in my 10 inch scope. It is interesting that the worst eyepieces during the day in my other scopes were the best eyepieces during the night in my 10 inch scope. Of course, this is somewhat predicted by Rutten and Van Venrooij on page 163 of their book. The worst ones at night for sharpness across the field were the 32mm UO Wide Scan and the 38mm Rini. The Rini was better than the Wide Scan only due to the lower magnification and narrower field of view of the Rini. The 38 Rini is also more of a daytime eyepiece. The shadows, visibility of the central obstruction, kidney beaning, and such that were present in the 30mm and 40mm eyepieces were not much of a problem at night with the exception of the 40mm Baader, which was seriously hampered by the shadow caused by the central obstruction. The 55 UO Plossl was horrible, the 85 Rini was surprisingly good and flexible; and, the 32 UO Koenig and the 40 Baader were just okay at night on star fields.
Now for my usual disclaimer. I am under the very strong belief that eyepieces perform differently in different scopes. The best eyepieces for my 10 inch reflector will not necessarily be the best eyepieces for another scope, or your scope. As a point of example, I selected the 30 Leitz and the 40mm UO 7/70 as the best night time eyepieces for my 10 inch scope based upon tonight's test; and, I chose the 32mm UO Wide Scan as the worst. It should be interesting to note that the person who sold me the 7/70 five years ago had a choice between selling the 7/70 or a 32mm UO Wide Scan. He chose to keep the 32 Wide Scan because he considered it slightly better in his 20 inch f/4 scope than the 7/70; and at the time, I considered the 40mm 7/70 better in my 10 incher than his 32 Wide Scan. So, we both got the best eyepiece for our scopes when all was said and done. The 32 Wide Scan does not match up well with my 10 inch f/4.5; but, I have proven to my satisfaction that it can and does match up very well with some other scopes, or under different conditions.
January 22, 1998 3:00 A.M. Moonrise, Quantum 6 Maksutov and Wide field eyepieces. I felt that no review would be complete without getting the eyepieces onto the moon. Sad to say I only had the moon in the murk soon after moonrise; but, I had to take what I could get as the clouds were coming in fast. Thankfully, I was able to test everything before the clouds covered the moon. Despite the f/15 of the Maksutov, the moon fit within the field of view of all the eyepieces. In short, the Koenigs were a touch superior on the moon compared to the other eyepieces in the Q6. The 30 Leitz and the 32 WS suffered from a mushier image, with the Leitz showing the dust on the eyepiece. Lots of blackout and shadows with the Leitz, not as much with the 32 WS. It should be noted that the brightness of the moon causes the human pupil to get smaller. As the pupil gets smaller, kidney beaning becomes more of a problem in any eyepiece that suffers from that aberration. Also, the brightness of the moon makes shadows and blackout effects much more noticable. See page 164 and page 175 of "Telescope Optics" for an explanation of spherical aberration of the exit pupil, or night time kidney beaning due to a bright moon and a small pupil. The 40 Baader had a sharp image, but suffered more from shadows and black out for some reason; I think the central obstruction shadow was visible again. I expected this eyepiece to do as well as the Koenigs on the moon because it barely out performed the Koenigs during the day; but, the Koenigs were better on the moon for some unexplained reason. The 38 Rini was there, but nothing special; the view of the moon being more similar to that of the 30 Leitz, but narrower field of view, of course. If I remember right, there was some stray light with 38 Rini on the moon. I just remember quickly eliminating the 38 Rini for the moon and moving on. The 55 UO Plossl and 85 Rini were horrible with severe ghosting and flare. The stray light was like a cloud in front of the moon, almost like the moon had exploded its light into the universe.
Since the Koenigs were the best in the Q6 on the moon, I thought I would mention a few things about them. The 2 inch 32mm UO Koenig produced the sharpest and most contrasty image of the moon; just a slight faint small almost imperceptible ghost dead center. The Q6 has a built in 1.75 barlow. The 2 inch 32 Koenig barlowed up very well, producing a nice image also. A close second place was the 1.25 inch UO 32mm Koenig. The 1.25 Koenig suffered from blackout around the edges, probably vignetting; and, it had a touch brighter ghost dead center. For third place, the 40mm UO 7/70 was as sharp and contrasty as the others; but, it produced shadows in the field of view if the eye was not in the right spot. But, I was able to find and hold a sweet spot. Overall, a pleasing view of the moon, and it too barlowed up quite well. It had a noticably wider field of view. The moon was being attacked by clouds when I finished up.
January 22, 1998 13:00 Testing eye relief with my 80mm refractor. There was a question regarding eye relief, so to complete my reviews I decided to force myself to keep my glasses on and test the eye relief of each eyepiece in question. Also note, all of my 80 mm refractor reviews were done straight through with no star diagonal in place. Just the scope and the eyepiece for the optics. The 10 inch Newtonian reflector was used straight through, so to speak. The Quantum 6 Maksutov has a built in mirror star diagonal that was used as a matter of course. With some of the eyepieces like the 40 Baader and 32 Wide Scan the barrel rises above the glass for protection of the lense, but the barrel ends up chewing up nearly half an inch of eye relief in the case of the 40 Baader Erfle. The 32 Wide Scan: Cannot see the full field of view with glasses, only about half. However, you cannot really see the full field of view without glasses either, at least not all at once due to the 80 plus degrees of the eyepiece. The 30 Leitz: Can almost see the full field of view with glasses, and you can almost see the full field without glasses. It was a quite a bit better with glasses than the 32 WS was; but, the glass of the Leitz is basically flat with the barrel top. The 32mm 2inch UO Koenig: Can see the full field with glasses. The 1.25 32mm Koenig: Can easily see the full field with glasses. 38 Rini: There is no field stop in the eyepiece, but you basically can see the full field with glasses. This eyepiece is quite good during the daytime if no comparisons are made with any other eyepiece. 40 Baader: You cannot see the full field of view with glasses, only about half of it. 40 7/70 UO Koenig: Can almost see the full field with glasses. However, once full field of view is achieved severe kidney beaning takes place during the daytime. The gem acquired from this eye relief test is that I found out that I can use glasses with the 7/70 during the day to find and hold the sweet spot. With glasses on, most of the field of view of the 7/70 is visible, and it is all good stuff. 55 UO Plossl: Plenty of eye relief. At prime focus and largest field of view the eyepiece is about 1 inch away from my glasses. 85 Rini Plossl: Huge eye relief. At prime focus and largest field of view the eyepiece is about 2 inches away from my glasses.
In summary, of the bunch there were three temptations. The 32 Wide Scan because it performed so well in my 80mm UO refractor during the day; however, I don't do much daytime viewing. The 30 Leitz because if performed so well on star fields at night in my 10 incher; but, it would cost $1000 for me to get this eyepiece, which is beyond my price range. The 2 inch 32mm UO Koenig because it performed well with my Quantum 6 Maksutov on the moon; I will probably get this eyepiece if I can find one used for the $75 price that it has been selling for on Astromart. Honorable mention. I intend to keep my UO 7/70 for the time being because it does really well with my 10 incher on star fields at night; and, with glasses on to protect me from the kidney beaning, it does OK during the day. I had fun, which is probably the purpose for the hobby. And, thanks for reading if you have gotten this far.
Darwin Bagley