3mm Radian or 3.5mm Delos

[alan potts]

Power!!!

Some members of the power family from Televue

3mm Radian and the 3.5mm Delos .

This was always going to be a difficult comparison to make, I did not buy them with that in mind though, for me they were two steps beyond on my APO refractor and lunacy in the Mak/Newt 190, or so I thought.

By the very nature of the focal lengths of these two they are never going to be of any use to many people, if I only had a scope like the LX then the magnification that even the Delos delivers would almost make it possible to see the little green men on the Moon, something my Son claimed only yesterday with 8X25 binoculars. These two fine oculars clearly would appeal to anyone with a scope that has a focal length in the sub one meter region and would be a must if the scope has a short focal length around half of that.

The observations for this were taken from 10 nights and 15 hours at the eyepieces and all scopes were cooled and collimated and in one case re-glued, but more that later.

3mm Radian.

I have three radians now (3mm 4mm & 5mm) and have parted with another two ( 6mm &  10mm), in general I find them excellent eyepieces that I feel have been somewhat overlooked by many as the monster field offerings have become more readily available. After all some people do not want a massive field of view especially when looking at the Moon or Planets, I feel I fall into that category but am still drawn towards the lower end Ethos duo like a magnet.

The one thing I am not over keen on the Radian is the adjustable eye-guard, I feel they could have done better on this aspect. The latest Radian almost clicks itself into the highest position under its own weight if you pick it up by the top part of the eyepiece which for me is not good enough, the 10mm that I had was almost the same but the others are and were noticeably better. I can only conclude that there is little in the way of consistency with regards to this part of the eyepieces design but to be fair this is not what an eyepiece is about, it is only the icing on the cake. The eyepiece comes deliver in the older style thick plastic bag and sturdy box with the normal Televue sticker and a pupil guide, something I personally have never found a need for but I can understand with the very large eye lens it could be useful.

3.5mm Delos.

I am building a reasonable collection of these now and have used or owned the lions share of them, they are without doubt a fine range of eye pieces offering mainly higher magnifications with the range finishing at 17.3mm which is still a high power in some of my scopes. Credit where credit is due, Televue went away with the eye-guard system offered on the Radians and Nagler T4’s and threw a double six with the design they fitted to the Delos, this is a superb eye-guard system that works brilliantly once you know it is there. I bought my first Delos shortly after they hit the market and like a man did not read the instructions and found it fairly hard to use, black-out or kidney beaning being the problem with the very large eye lenses they all have. Once however the penny drops the views are simply quite stunning with the extra 12 degrees of field on offer and sharpness you could shave with. The full range are delivered in something of a bomb proof box with high impact foam padding, I would never suggest you put it to the test but I am sure this could be dropped without issue, how I wish my 6mm Delos was in its box when it fell from the mount on the APO. I guess it is only natural but I now check the two tightening bolts on the mount 5-6 times a night now.

Telescopes.

As I said at the top there are many scopes these two cannot really be used on, I don’t see that X900 is going to show me much even on the Moon if I were using the 180mm Maksutov. I do however have three scopes that I could use these two on.

The scope will be; 190mm F 5.26  Maksutov/ Newtonian. 115mm  F 7 Apo and a newcomer to the reviews the 70mm F 6 ED. The latter being one where the 3mm focal length delivers just about the maximum magnification for the size of the objective lens, though on a very good night and on some targets it could be pushed a little higher.

Targets,

I have to say I am a bit short circuited here with most of the planets either in the morning sky or not getting high enough until I am sound asleep. Though I am no stranger to getting out of bed early I have many things to do now early doors, with a wood burning heating system being somewhat prehistoric. I will do a better and extensive planetary test later in the year or early next year, by then I may have been tempted buy the 4.7mm Ethos.

Jupiter is a target that calls out for this focal length eyepiece on the two refractors though some would say, me included that X230 is a little high on the larger one and the Radian will of course be even higher. The problem I have with Jupiter is this is rising where I have a sizeable hill, albeit a couple of miles away, at the foot of which is a wide shallow river, the seeing in this direction always seem to be poor. Whether this is to do with the hill or water vapour rising from the river heated but the sun during the day, I simply do not know, but seeing difference there most certainly is.

In the end I selected.

Moon,

Venus,

Messier 15,

Messier 2,

Sigma Cassiopeia

The Pole star

Vega

Epsilon Lyre

The first scope to mount up was the 115mm or 4 ½ inch in old money, APO refractor, many site members have similar sized instruments and can relate well to this type of telescope. The 3.5mm Delos gives a magnification of X230 and a AFOV of .31 which is not very much. The Radian is going to win this one though with the power hitting X268 and the AFOV down to a lowly .22 of a degree. Apart from the two very bright objects on the list I was not expecting very much, but how wrong I was.

Venus,

Now I know Venus has nothing to offer in the way of surface details and you need a fairly large telescope to see even any cloud detail but it is always nice to see the phase of Venus especially when it gets below half and starts to look like a little new Moon. It is rather difficult to miss in the evening sky at a magnitude of -4.5 and I am always surprised how few know what it is. The phase was just below 40% when I was using the planet for the first time on this review and nearer 35% last night. The main reason for this choice of target is light scatter, this is something mainly seen on very bright subjects which can be distracting. Both Radian and Delos performed very well here as I could detect very little in the way of scatter which is the type of result was expecting from them. Both also showed about the same degree of atmospheric aberration which is a little red and blue colour fringing cause when viewing something very bright which is very low in the sky. I have viewed Venus when it was higher with absolutely no false colour what so ever with the same scope, you can get the same effect on Jupiter as well but I cannot say I have ever seen it on the Moon. With both eyepieces, even though one was offering almost an extra X40, sharpness was the same no matter where you placed them in the field of view. It has to be said that seeing was drifting in and out but there were still moments where one could see this and my observations were based on seven nights in total. When you consider that Venus has not been best placed this time around this an excellent result from both eyepieces and I would not call one better than the other here, though I was very impressed with the Radian with the power being that much higher.

Moon.

I think is goes without saying that the Moon is a subject where you can push the envelope somewhat as long as the local conditions permit there is little to stop you going above X300 even on this moderate instrument.

For my first night on this scope using the Moon it was 3 days old and time was short before it went behind one of the walnut trees . I was using my old friends from the other reviews, Geminus, Cleomedes ‘B’ and a new one for me Burckhardt ‘F’. I also had a good long look at the area with crater Wrottesley, don’t for one moment think I know these names, I am using virtual Moon atlas on an old laptop.

Later in the week I revisited the Moon when it was in my least favourite part of the sky and it was fairly close to full. I spent most of the time looking at craters Riccioli and Grimaldi which were very close to the limb of the Moon. I was trying my very best to see any sharpness or contrast differences and I could not see any, in fact the only difference I could see was the size of the field of view, even the magnification was not that obvious to me. It must be said though that the Radian is delivering more power and it is doing it remarkably well, many members on site love the Delos range, and it is difficult not to but this 3mm Radian was pushing hard to be noticed.

The fifth night on the Moon was the most amusing as I had to view it over the river and hill that I was talking about earlier, seeing was not as bad as I have seen it and these powers were usable but not advisable, I was also teated to a lovely moon rise with its light reflecting off some high cloud turning them light blue, very nice. The Moon was past full and I was back to the same set of edge craters as I was using the week before plus many more I do not know the names of. At first I though I could see a double star that had been occulted by the Moon then realized that was not possible because of where it was, and then I thought it was moving, it looked just like a man bent over with a heavy pack. Then I saw it for what it really was, the sun lighting the higher rim of a crater in shadow, this brought home to me the importance of quality seeing.

Messier 15 Globular Cluster.

This is a lovely cluster in the LX with its extra mirror size but not something I can recall looking at through this scope. It was largely on the back of something site moderator Swampthing had posted, it was along the lines of “globular clusters take magnification very well”, this was something to try out.

The first thing I have to say with this as a target was the goto was next to useless so locating the object was a case of longer eyepiece then work your way up. The other thing was that focusing on these highly magnified and rather dim stars was very tedious work indeed, there is not much of a sweet spot like with the 41mm Panoptic where half a turn made little difference, even the smallest movement made all the difference. When the focus was there, my, oh my, yes the seeing was making the cluster drift a little but when you had a moment of absolute still the result was mesmerizing. Both eyepiece gave a remarkable view of the globular with even the outer stars showing as star and not just a fuzzy blob, it was a shock to me at just how much a 4 ½ in telescope could show from a dark site. It was on this one though that I preferred the Radian, for me it gave just that slightly better view when the air allowed and just made the cluster that bit less compact and dare I say easier to see, showing the outer stars better. With a magnification of X260ish with a 115mm scope, who would have thought? I would like to point out this was my notes from a night of a 4 day old Moon and the cluster stood out all the more when the Moon was out of the way a few nights back. It was remarkable that such a good result was obtained from this night but that was how I saw it.

                                

Messier 2,

This is a little lower in the sky than the other cluster but still fairly bright and well enough placed for me to use. This really was a repeat performance of M15 with the Radian showing it for my eyes better than the Delos. Again I was in the hands of the atmospheric Gods and I had to wait my chance using such powers. There was little or nothing wrong with the Delos’s rendition of the cluster and you could even say it was easier to view with the extra field and lower magnification but I just liked the Radians extra power though the waits to see it were a little infuriating at times. I do feel that with almost X40 between the eyepieces on this scope at least we are not really comparing apples with apples.

Skywatcher 190mm Mak/Newt, collimation checked.

The first thing I have to say that with the planets out of the way at the moment the only target that is worth comment on here is the Moon and Venus, I did view the other targets but the power was in my view, too much. It was interesting though looking at Polaris, not a tight double but at X333 it looks like you could drive a bus between the two components.

Venus,

Light scatter was very well controlled in both eyepieces and again I could not see anything between them. The planet can take magnification as long as conditions permit and this night was one of those. I was my best view of the planet so far this year though I did take time out to reduce the power a little down the 4.5mm Delos for my best and sharpest image. There did not seem to be so much atmosphere interference this night and the only interference was coming from the wife. If it was possible to make a rhyme in the old song “I am the Music Man”,  my wife would have played the kitchen lighting system. Of course setting up close to the house is always going to have drawbacks and these are not so bad when looking at Venus and the Moon, but a different story when it is M15 at the power I was using.

With the Delos giving X285 and the radian X333 there is some gap between there two, enough for another eyepiece almost. What I am beginning to see here is there is not very much if anything between these two, or if there is I can’t see it.

Moon.

This is in my opinion the best time to look at the moon when it is at first quarter, viewing craters such as Herschel, Bode and many others, this is the time when one can turn up the wick and really get in close, you should never turn your back on the seeing though and a smaller sharper image will always win me over. For fear of getting repetitive there was no difference between the quality of either eyepiece and if anything the tighter view of the radian was in many ways nicer though the Delos was hardly showing a wide vista. I found an interesting game to play, cheap sunglasses, use one eye to view the Moon for a while and then come away from the eyepiece, then look up at the stars open and close each eye, it is like you are wearing a sunglass monical

70mm ED.

This is a Chinese scope from Teleskop Services in Germany and I have two of them, one is mounted on the LX and this one is not. When I received this telescope it was bent and the star quality was appalling, at the edges looking a little like the big screen when the Starship Enterprise goes to warp factor 2, lines radiating outwards. Anyway I took it apart and played with it putting it back together in a better but not good alignment.

I had a nice new and clean mirror laying in the basement, it was then I had an idea. Taking it as read the objective lens was in the correct place and an equal distance from the front edge of the scope; I stood the tube on the mirror and put my Hotech laser in the focuser, thinking if it was correct it would reflect right back along the same path. I tried this half baked method and it was some way out, I made adjustment with little pieces of paper to hold it tight, star tested it and found it was rather good, then glued it in place with 10 minute epoxy. Job done.

Polaris

This I feel is a little overlooked as a double and with the small scope giving X120 and X140 with the two eyepieces thought it was going to be a test, how wrong I was, the double was split very easily and could been seen long before it was astronomically dark. It sort of cast my mind back to when I started with my 3 inch refractor all those years ago when scopes were sold to the unknowing based purely on power and yes I did try X600 on my 1200mm F/L scope with a 4mm orthoscopic and a Barlow, all of questionable quality. I think that the Delos gave a slightly better view of this double but I am sure this was only due to the small power making the star disc that bit sharper, both looked really nice though and much more like a serious telescope than it once was .

Vega,

I picked Vega just to see how good my new found talent as a telescope repair was fairing and I have to say I was rather surprised with the quality of the airy disc, both eyepieces showing some diffraction rings on what was a very clear and steady night. There was a deterioration of the image towards the very edges of the field but this was the scope and nothing to do with either eyepiece.

Sigma Cas,

This was a target that I thought I would need about the power the two Televues provided to show me the split pair and the star did indeed show a clear split. This little scope is a bit better than I gave it credit for whilst it is not of the same quality as the APM, it also was not with the same price tag. It shows to me that you do not have to spend a fortune on the hobby to get enjoyment out of it. Neither eyepiece had an edge over the other here and both gave clear and clean views.

The Double Double.

Thinking this was going to be the straw that broke the camels back I decided to give this well viewed target a look in. I was wondering if the power was enough to see a split with the scope only being a mere 70mm as most seem to like X150 and greater to see this, though I have split this below x100 albeit with a better instrument.

This is very much a of case of good news and bad news, the good news being I split both doubles, the bad being I only saw a split of one double with the Delos. This I feel was only a case of the extra X20 helping the cause and I could see it was clearly a double star though could not see a gap at the lower power.

Moon.

I used this scope on the Moon I found it rather nice to see the whole Moon at X120 with the Delos 3.5mm. Again this underlined that anyone just starting can see a lot of interesting features on the Moon and no doubt belts on Jupiter as well as splitting double stars without breaking the bank. On this night and the night after the Moon was just over first quarter and the line of crater running up the middle was an awesome sight with the wonderful monster crater Copernicus coming into view, even with 70mm of objective you could see a lot of detail.

Conclusion.

Let me start the conclusion by firstly apologizing for not including Mars and Jupiter and yesterday morning Mercury, it is just too much for me this time of year. I will put a report together when they become more Alan friendly.

Now I know that many will not find a slot in their eyepiece cases for either of these as they would just be too much on their given telescopes, even in an F 5, 10 inch Dobsonian both are really on the very top limit of what could ever be useable even on the Moon. More to the point how many would want to spend this amount on a rare visitor to the focuser.

If however you are in the market for a very high quality high power eyepiece neither will disappoint.

It was told to me by a highly respected site member that to see many of the subtle differences between quality eyepieces you need aperture, this is one instance where this cannot be the case as much above a meter of focal length renders them next to useless. If I could only select one of these now I own both of them it would be the 3mm Radian, if I had a Dobsonian scope it may well be the Delos for extra field of view that it offers, that is how much alike these two are. For me though the Radian frames things at high power very well, is as sharp as a sharp thing and a good few quid less than the Delos and if you don’t need the extra width why not go for the Radian. The Delos did give a slightly whiter image of the Moon but I feel the famous Radian colour cast is grossly exaggerated or there is something wrong with my eyes, I found it hard to see a difference and I was really looking for it. However at this level it could be another factor that makes the choice, the focal length of the scope you own.

Clear skies.

Alan.        

[John]

What a great read Alan and another very fine contribution to the forum - thanks for taking the trouble to compile this report

I do feel that Radian's represent excellent value at the used prices we are currently seeing them at. Of course reports like this could drive their prices up a bit !

With the Delos, Tele Vue have clearly incorporated some meaningful ergonomic improvements and obviously have listened to feedback on the older "Instajust" system and produced one which is arguably the best of it's type currently.

Thanks again Alan   

[YKSE]

Thanks for another extensive report of hour's testing on fields, Alan.  Very well organized and detailed descriptions.

[alan potts]

John,

I didn't think of it that way. Something makes me think that even if the prices do go up a little we will not be selling ours. I will put something together on the planets even if it is much the same story, I will be doing something similar on the 4mm R and 4.5mm D as well It will be interesting to see if they are the same.

Alan.

[John]

John,

I didn't think of it that way. Something makes me think that even if the prices do go up a little we will not be selling ours. I will put something together on the planets even if it is much the same story, I will be doing something similar on the 4mm R and 4.5mm D as well It will be interesting to see if they are the same.

Alan.

I was joking about prices Alan

I guess well written reports like this can have an impact on the market for a product though, negative or positive. What a responsibility ! 

[Stu]

Very nice review again Alan. I certainly agree that the Radian is under-rated, and the whole colour cast thing totally over-emphasized. I think these short focal length eps suit mid to fast apo refractors very well. I have a few in my case covering between x170 and x230 in my 106 apo and they all get used depending on the seeing conditions.

Cheers,

Stu

[alan potts]

I'm with you on this one Stu, they all get used, I was surprised at how good the views were at these magnifcations but focusing them was a real pain. I did forget in hurry to write this, this afternoon the two eyepieces were parfocal with each other, believe me you have no idea what a blessing that was. The saying " good things come to those who wait" is very true in this little test but if it was not from a good dark site all would be lost. Sadly from many parts now within any town this is not possible and these true joys in astronomy are in danger of being lost to most people. I think I am becoming a magnification addict.

Alan.

[swamp thing]

Great read Alan, very nice review.

Here is two eyepieces I know I'll never need or use but it sure is fun to read about them. Thanks for sharing

[RikM]

Another great review Alan. I often use 4mm, 3.5mm and once or twice even 2.8mm (equivalent) with the Pronto (450mm FL). It is remarkable just what can be seen with a nice small telescope. When there are planets to view and the sky is a bit murky, I will sometimes just go up to the highest power suitable for the seeing and spend an hour or so on just the one target. It really is the best stress relief I know.

I am certainly going to be getting a nice 5mm in the next few weeks, who knows, maybe a 3.5mm upgrade to go with it?

[AlexB67]

Very nice report Alan. I've had my eyes on these Radian eps second hand.  If  I have the money at the time and one turns up in it is mine, at least If I can snap one up  at the price I do see them go at     but often I think the shorter focal lengths are the ones that do come up, and it is not worth it for me at this time to invest in a < 5mm radian at that cost level, since I would not use it that often. Now something like the 8mm and above different story :0).  Though I did spot a 5mm  here or somewhere recently, very tempting, nonetheless  ..at this time,  a no for me 

[Rustysplit]

Fantastic report Alan, the one I have been waiting for with bated breath. I can relax now, the fear was that you were gonna conclude that the Delos blew the Rad out of the water . I fully agree with your sentiments re the Radian colour cast, be darned if I can see it. The Instajust eyegaurd takes a bit of getting used to, but like eye placement, soon becomes 2nd nature.  I have regularly used my 5mm Rad in my 1800fl scope giving 360x, needs a fair bit of nudging of the scope to track, but Oh! what views.  If I can just find that elusive 8mm to complete my set, I will have all the ep's I need for some considerable time to come.

[Rickstar]

This just goes to show how advanced an eyepiece the Radian was for its time.

[alan potts]

Alex,

I take your point about the 5mm which is also a fine eyepiece and in my view every bit as good as the XW Pentax, there really is so little between these players at this level. On FOV sharpness I don't see a thing between any and I am talking in different scopes, I know they are not all in the same class as the APM. If you could find the spare cash at a later date and a 5mm I would strongly advise you take the step, it will reward you for years to come with some stunning but difficult to come by high power views. It really was a great way of winding down, sitting at the scope waiting for the air to steady, even found myself talking to the scope at one point, I am not sure if that is winding down or going mad.

I have to say this is something I never really thought I would ever say, only a few months back X200ish was tops for me, for ages the 4mm was my shortest eyepiece (X202 in the APM and X250 in the M/N), I never really went beyond these.

Alan.   

[alan potts]

Alan,

I think the 8mm will be a little like the bus, two or three will come together. I almost bought one from a site member that I don't see on site any more, I bought a Televue from him, I think it was the 35mm Panoptic. The odd thing was he was trying to sell it at a good price for a long time and in the end gave up.

I have my Meade dealer friend in Sofia looking for you as well all he has managed so far is a 3.5mm Pentax for himself, a good catch indeed.

As for the moving of the Dobsonian, this is where the wider FOV is a God send. I don't mention it but I often have the drives off just so I can see it from the Dob owners perspective, well sort of I know the mount is still EQ.

Alan.

[Pig]

Great review Alan with lots of interesting detail and a very good selection of objects thus making a very good read indeed 

Its not something I will be able to use due to my scopes 2.35mtr focal length

Just to add a little more work for you it would be nice to see how they both compare to the 3-6mm Nagler zoom set at around 4mm

[SimonfromSussex]

Really great report Alan and a very interesting read.

Like Steve these focal lengths are way too much for my 1829F/L but non the less it's been good to hear how you can push the mag at times on certain objects and I will certainly be giving that a try next clear night with maybe a 6 or even 5mm in my scope. M15 sounds like a good target to crank the power up on!!?

If Rusty (other Alan) can get hold of this elusive 8mm Radian then we might be able to do some side by side comparisons with my 8mm Delos and also possible the 12mms too to see how the two compare in longer F/L.

[Luke]

Great write-up, Alan.    Thanks for your time to compare these two great eyepieces and to do a write-up.

I agree that the Radian is underrated. At around £100, a second-hand one looks a very good buy to me. I nearly sold mine as I find the Delos a touch better in my dob, but couldn't let them go at that low a price for their performance. Glad I kept them as they work great for solar hydrogen alpha as well, even better than the Delos in my view, so they will be keepers now.

I do notice the warm colour cast, but it's mild, just a slight tint really, and pleasant enough anyway in my view. I think of it as a charming characteristic of the Radian rather than as something negative. It would be boring if all eyepieces felt the same.

In my 16 inch dob, the 8mm Delos at 225x mag does nudge ahead of my 8mm Radian, but I have lost count of the number of spectacular views with the Radian before I got the Delos, so I am wondering if I ended up "improving" for improvement's sake. Both EP's have been an absolute joy to own.

[Rustysplit]

You are probably right Alan, I bet a few turn up at once. Thanks for keeping an eye out for one for me.  Strangely I don't find the fov in the dob much of an issue. I quite like starting an object right on the edge one side, and letting it drift across right to the other edge. With the supreme sharpness across the whole fov, not a problem in the Rads.

[alan potts]

Luke,

At 8mm you many well have a different result, I can't believe they are all going to be the same, any difference is only going to be subtle though. With a large aperture you are always going to be having more light to see a difference, it was pointed out to me as I said really large scopes show the differences more, he was talking 20 inch plus, sadly I do not have one of those. In any case unless there is a 24 inch F 1.5 on the market the magnification it going to be totally off the scale when talking about these eyepieces. It may well account for the fact that I found so little between them, even in the 190mm, which is nowhere near the size of yours, we were up to X300 plus which is fairly difficult to use.

I did also do some viewing with the 3-6mm zoom at the same time and a 6mm and 7mm BGO with powermate. I didn't see a difference on the latter two BGO's but I could see differences with the zoom but not serious by any means. I will do some follow up work in this area though I am not sure the BGO Powermate is a fair test.  At the moment we have 8 inches of snow so it is snow stop play.

Alan.