Pentax 5mm XW and Delos 4.5mm

[alan potts]

Can you tell Stork from butter?

Now I knew this one was never going to be easy, both eyepieces coming for the cream of the manufacturers, both with an outstanding past. Both eyepieces are fairly tall, especially if you are going to use an orthoscopic for the next power step, fair weight difference too. If you disregard the colour they look much the same as well, both in similar sized boxes and very well packed. On this though the Pentax has the edge for me coming as it does in a very nice bullet case, always a nice touch, not everyone has a Peli eyepiece case. Though not to be out gunned I do prefer the lockable eye guard of the Delos, this is a very personal thing and many will disagree though.

I used a fair array of scopes to try and split these to high power gladiators and probably as a result of too much sun ( or beer) used them with a Powermate, giving mind blowing magnification.

The scopes that these will be used on the most are short focal length ones, so they were not going to get a airing in the 12 inch with its 3048mm focal length or the newly acquired Maksutov at 2700mm.

Around here I would normally insert a couple of photos of the eyepieces but sadly my son gave the card reader a drink of milk and it didn’t agree with it one bit.

The scopes used were the 115mm APO with its F/L of 805mm, the 190mm M/N at a meter and the GSO RC with a longer F/L of 1370mm. The time spent doing this may well be considered as somewhat excessive at 18 hours on the scopes but this was not a walk in the park, one has to ensure that focus it just right and with swapping one for the other so many times I just got carried away. I did not over egg the pudding with targets this time choosing just a few, I think the magnification played a large part in this as well.

Targets.

Saturn.

Antares.

M65, M66 triplet with NGC 3628

NGC3593 (just for good measure)

Gamma Leo.

The Moon (it was there so why not)

APM 115mm. The Pentax giving X161 and the Delos X178

First night out and it was first light for the Pentax XW 5mm, well for me anyway, a site member very kindly sold me it while I was in England. I started out with Saturn on a night of iffy seeing, it’s a subject that can be viewed long before it gets dark and that seem to take ages at this time of year, even here. In England I sometimes wonder if in northerm parts it ever gets totally dark around now.

The first thing that struck me was even though it was still light enough to read a paper, well if I had my glasses on that is, I was taken aback by how easy it was to see Titan which has a magnitude of about 8.5. The Cassini division was clear to see as well Switching back and fore between to two combatants taking care to focus every time it suddenly dawned on me this is a job for a bino-viewer, then open an close one eye then the other. Sadly I do not have one so it became something of a labour of love swapping them about. It was not long before I could make out Rhea and then Tethys, though the sky was still not as dark as it would get. Both eyepieces showed as far as I could see the same image, bright, sharp and very well controlled all around, pretty much the sort of result that one would expect for a top quality eyepiece scope combination.

I switched across to Gamma Leo which is a fairly tight double at 3.7 (not sure of exact figure), this is a nice double and I was not expecting it to be a problem with the scope or either eyepiece, and it was not. Though clearly split there was no hint of colour that I could see, this was mainly due to the magnification I am sure, at lower power I can normally see a yellowish tinge to the pair. Not wishing to sound boring but I could not see any difference between to the two here either.

Going back to Saturn ( another night of better seeing), The slightly fainter Dione came to see me at a Mag of 10.8, well that was what the laptop top told me it was, to me, though nice to see thay are just very faint and small specs of light. I would have thought that an articulated lorry Dobsonian would be needed to show them as much more than this. I tried to hunt down Enceladus which at a magnitude of 12 was probably a waste of time this being at around the scopes top limit and it is always close to the main body of Saturn itself.

The Moon.

As this has taken over a month to collect the observations there was always going to be a night where the Moon put in an appearance, I have never been a big fan of the moon, I really don’t know why as you can see so much detail with even a small telescope. This night the moon was 6 days old and showing the classic children’s story book crescent. The view was very nice indeed with both eyepieces and there was nothing between them, I had began the see a pattern emerging long before this night with other objects. It was this night I had a rush of brains to the head and played my joker, out came the Powermate, this was to give a very high, X322 from the Pentax and X356 from the Delos. The seeing was not that wonderful and it wasn’t even that dark but I was shocked at just how good the Moon appeared at powers that I would never use, well not on such a small scope.

Though a great deal of the time was spent with this scope and I did view all the objects that were on the list of targets at no point could I see any difference between these two fine eyepieces with this telescope.

The only things of note really was most likely an optical illusion in one case as the Delos seemed to give me a more in your face view with an appearance of a wider field of view. This seemed to be further forward in the eyepiece where as the Pentax seemed to be further back in the eyepiece, almost like you were looking down a tube at the targets. I don’t know any other way of putting it but if you ever get a chance to compare the two side by side, see if it appear the same to you.

The other small point was I saw a small amount of chromatic aberration from the Pentax when you put the limb of the Moon at the very edge of the FOV, something I could not repeat with the Delos and I do mean the very edge. This is not really a criticism as some eyepieces are not even sharp at the point something you could not level at either of these. The aberation was also visble on the other scopes.

Sky-watcher 190mm M/N.

I spent 3 nights using this telescope and made sure it was collimated to as good as I could achieve with my laser. I have now worked out a way of doing this using the slotted Sky-watcher 2-1.25 reducer, it seems to work too.

Saturn was absolutely stunning with a good deal of belt detail visible and a colour difference on display in the rings. It was also the best I have seen Cassini , the larger aperture no doubt accounting for this. I could also clearly see the polar cap but was unable to see it anything other than circular. Dione, Tethys and Rhea were easy to see but again Enceladus and Mimas eluded me, I can normally pick these up in the 12 inch but it may well be a case of selecting a night when they are better placed with the smaller scope. I don’t know if it was due to the magnification of X200 against X222 of the Delos but I could see a very slight brightness difference between the two with the Pentax just having an edge.

Leo Triplet.

This I always find easy enough to see in the 190mm but I normally look at it with a much longer focal length eyepiece, my 35mm Panoptic being favourite. As I could not be bothered to set-up the Goto system, out came the Panoptic, I normally manage to find this with the main scope as I know where it is in relation to other stars but was not going to try this with a 5mm eyepiece. By the time it was dark enough to look for these galaxies, Leo was not best placed but this night the seeing was very good indeed so I was hopeful

Messier 66 is clear enough to see, as is M 65 both having magnitudes of around 9, they are also very close together in the FOV in the Panoptic but not so in the 5mm. It is simple enough to find the one from the other though with just a nudge of the scope dobsonian style ( reminds me of a silly song). The galaxy NGC 3628 though is a different kettle of fish and I had a hard time finding it with only the 5mm Pentaxs FOV, sure enough though I could see the what many consider difficult target. I have to say I could again see no difference in the fussy cigar like wisps but was drawn as I often am to wonder if anyone out there was looking at our galaxy. I think at this point it would have been nice to have a lesser eyepiece to evaluate against to see if light transmission was better and how noticeable any differences were, but sadly i don't have one.

Now with a hunger for DSO I tried to hunt down NGC 3593 which with a surface brightness of 11.0 thought would be food and drink for the Mak/Newt, but was shocked when I could not find it. This was a galaxy I had seen before with the larger 12 inch and found it with ease, those extra 4 and a bit inches coming into play and a very good Goto system all playing a part.

Antares.

Now I know that this is a very low object in the sky from any part of the United Kingdom and I would think from Scotland was not far above the horizon. I however have about an 11 degree advantage over everyone in England and it is still low for me. This is the time where I could see a difference between the Pentax XW and the Delos. I saw the double star of Antares with the 5mm at a magnification of X200.

Well after doing a lap of the garden and tripping over the hose I came back to the scope to see if I was dreaming, I wasn’t. Quickly changing to the Delos I could not see the double, bear in mind there is a magnification difference here and Antares is never well placed to look at and most times seems more difficult than Sirius for scintillation. Then I could just glimpse it then it was gone. I change back and forth and I have to say the Pentax here had a edge over the 4.5mm Delos. While I was doing this I though I had discovered a new phenomena, lighting on Antares. I was well let down when I found it was a vain firefly looking at himself in the mirror of the scope, just as well he was clever enough to understand it was not a mate.

The GSO RC 150 only backed up everything the other two scopes showed. I viewed the Moon at 7 days with it and I have to say two better eyepieces will be hard to come by for this target, both delivering over x274 magnification and the Moon was a sharp as a razor when the air settled. It was very much a night of steady periods of seeing interspersed with air turbulence. Saturn was also very nice but for me there was just a little too much power with the Delos but I could just stomach the Pentax. That said many would be happy with the power and image quality from both.

I could write a whole lot more about these two with the notes I have written and I could just as well sum them up in one word, ‘quality’. If you are about to buy one of these two, there is no better time to buy a Delos with the recent discounts. it really will not matter which you get for the type of scope with a F/L of around 800-1000mm the difference in the magnification is not significant many will choose the 5mm just because it will always be just that bit more seeing friendly. People with short scopes will most likely go for the shorter Delos or the two very fine 3.5mm eyepieces that these two companies make. Some may even just buy on brand alone.

If you were to put a gun to my head and ask me to pick one, then I would go for the Pentax only because of the bullet case and the fact that it showed me the double star of Antares for the first time ever. In truth which ever you choose there is no bad decision they are both absolutely superb eyepieces.

I would like to end by saying something that I was doing last week standing in The Black Sea with my son Daniel. Making a comparison between these two was very much like trying to see a difference between two sides of a clams shell and that is not easy.

Clear skies one and all.

Alan

[michael.h.f.wilkinson]

Very nice detailed report, thanks a lot. I think I will stick to the XW path for a while (the 14mm is beckoning as mid-power solar EP, and is parfocal with the XW10 and XW7 I have). An XW 5 would be over the top for the C8, but is just the ticket in the 80mm F/6

[Damo636]

Great report Alan, really enjoyed reading it. Your findings are much as mine, and I think anyone torn between which of these two to buy could literally flip a coin! Another comparison I would be interested in is the 14 XW and the 14 Delos. As you know I thought the 14 Delos was superb but have never tried the 14 XW. I would love to complete a set of the 1.25" XW's, but have always been wary due to the reports of field curvature in the 14 & 20mm.

[alan potts]

Damo,

I am still doing a bit of work on the 14mm Delos and Pentax. I will write it up maybe next week. The delay is with using them on different scopes 14mm is the area where the LX 200 comes out to play and now the Mak 180mm, so different set of optics.

Alan

[Damo636]

Nice one Alan, I'll be looking forward to that report.

[rowan46]

Thank you and I am looking forward to the next report

[faulksy]

very nice report alan, I could see triping over the hose in my mind lol. so the pentax was better on 1 object but equal on the rest, hard choices

[alan potts]

Faulksy

Put your way it would have saved me an hour and a half but yes that about sums it up. If there were differences then all I can say it will take a better man than me to see them, believe me I tried. I know John said he had read that difeerences were more noticeable in larger scopes, like 24 inches plus scopes, I can see a divorce on the cards.

Alan.

[John]

Excellent report Alan

Fascinating to think that the Pentax XW has been around for years, rarely seems to be advertised in astro circles and was not even designed as an astro eyepiece, as far as I'm aware.

I wonder what the Pentax folks could produce for astro use if they really put their minds to it ?

Hats off to Tele Vue too though for producing another world class eyepiece in the Delos.

Thanks for taking the trouble to compile the report and post it - a most enjoyable read

[alan potts]

John,

In truth it gives me something to do as well as observe. I have never been one for keeping a log and doing stuff like this adds a different dimention to the hobby that I sort of get a kick out of, some seem to like them as well.

When did the Pentax XW range hit the market because was there not an XL range before them.? I have to agree what could they do if comitted to astronomy.

It was worth the 18 hours just to bag Antares, I am hoping for a second sighting to-night.

Alan.

[John]

Yes the XL range preceded the XW's. Both designed with spotting scopes in mind I believe. The XL's seem to have been excellent as well.

I find comparing eyepieces does cause you to observe objects more critically, rather in the way you do when you are trying to sketch them. It's usually features / objects that are right at the edge of the capabilities of scope / observer / conditions that show up differences between them, if there are any.

Antares is a non-starter for me at my current location, sadly. Many congratulations on bagging it though

[alan potts]

Over the last month or so I have played with a vast expense of glass from 14mm down to 4.5mm with the Delos range and the Pentax XW. I can't recall who it was but he had his head screwed on the right way in his choice but wallet emptied at the same time. He went for 8mm Delos 7mm XW 6mm Delos and 5mm Xw

What a line up these make from two of the best eyepiece manufacturers, I have not used all of them, but most.

14mm, either TV or Pentax XW, 12mm Delos, 10mm either, 8mm Delos, 7mm Pentax XW, 6mm Delos, 5mm Pentax XW 4.5mm Delos and at 3.5mm either. I would say anyone that would not be happy with a full spread from that little lot must be a very hard person to please.

Alan

[John]

...14mm, either TV or Pentax XW, 12mm Delos, 10mm either, 8mm Delos, 7mm Pentax XW, 6mm Delos, 5mm Pentax XW 4.5mm Delos and at 3.5mm either. I would say anyone that would not be happy with a full spread from that little lot must be a very hard person to please.

Alan

I must be hard to please - I always want a 4mm in my set. I have the Radian now in that spot and very good it's proving

[alan potts]

Yes John,

I have that too but I think you got my over all point.

I sometimes wonder why there are so few eyepieces at this end of the range, I mean Pentax drop from 5mm to 3.5mm, same with the Naglers. WO go from 7mm to 4mm. I know others are available but I am left wondering why there isn't someone that goes from 2.5mm to 6mm in .5mm jumps, maybe it's the cost of development against sales.

I still keep looking at the 3mm Radian wilth a should I buy ine face on.

Alan

[Stu]

I agree with you John. I've got a 4.5mm Delos and 3.5mm t6 Nagler but do need something in the middle. In my 106mm they give x153 and x197 respectively, 4mm would be lovely at x172. I fill the gap with the Nag Zoom at the moment which is not too much of a hardship.

That said, the 3.7 Ethos would be lovelier but that really will have to wait for a while :-)

Stu

[GavStar]

I wanted a 4mm in the end decided that using a 2x televue barlow on the Delos 8mm was the right solution for me.

[Stu]

Yep, that would work. Haven't tried mine with the power mate yet but should work well. Thanks for the reminder

Stu

[John]

I was using a Tele Vue Powermate 2x with my 8mm Ethos and an 8mm Tele Vue Plossl to get my 4mm for a while. The optical performance was 1st class of course but I did find the Ethos / Powermate combination rather bulky so I was happy to pick up a bargain on a 4mm Radian in the end. Marvellous though the Powermates and their like are, I think I prefer not to use one if possible.

@ Alan: I've recently picked up a similar bargain on a 3mm Radian to complete (really this time !) my high powered set. For around £100 I reckon the Radians are excellent buys

@ Stu: I've thought about the 4.7 and 3.7 SX Ethos a few times but resisted so far

I just need another eyepiece case now for the < 6mm ones

[Stu]

@ Stu: I've thought about the 4.7 and 3.7 SX Ethos a few times but resisted so far

I just need another eyepiece case now for the < 6mm ones

I think I will get a 3.7 eventually. It would give x186 if I remember correctly which would be an excellent power very useable on most reasonable nights.

I know what you mean about EP cases, mine are brimming now!!

I picked up a 6mm Radian recently for a very reasonable price. It's silly isn't it, a few negative comments on CloudyNights about the colour caste (which I don't really notice, certainly don't find a problem) and they seem to have gone out of fashion. I might try and find 4mm too as I think they are great eps

Stu

[alan potts]

I just don't know where you keep finding all these radians, I have sort of been on the lookout for a 3mm for ages and apart from in the States never seen one S/H. It is an eyepiece that will only get limited use giving about 268 on my APO, which was what I was intending using it on, being a limited eyepiece it is a dear do new. The funny thing since I have the Nagler zoom I have just wanted one all the more, there is nothing wrong with the zoom but, if a Radian came up.

On the other hand maybe I am being a bit hard on my APO, I got the 41mm Panoptic really for one scope and that don't see light very often.

I keep thinking long and hard about the 4.7mm Ethos, maybe if they have a promotion I will go for one, like 50% discount would be nice.

Alan.

[Dunkster]

Well Alan, if your not putting your 41 Pan to good use, you're welcome to send it to me to test under a proper sky I bet that would make for an interesting shoot out with the XW40...

[John]

....I keep thinking long and hard about the 4.7mm Ethos, maybe if they have a promotion I will go for one, like 50% discount would be nice....

I'll let you know if and when they run a 50% off promotion on the Ethos range Alan - immediately after I've completed my collection

[alan potts]

John,

Something makes me think there is more chance of the Prime Minister popping in for a beer. The 4.7mm I have not seen anyone on site that was saying they have one, something makes me think it's quite rare, though i have seen a couple of the 3.7mm on Ast B&S in the last year. It seem to me few are into the ultra wide FOV at high magnification, mine stop at 6mm like yours, I like the 6mm a great deal and I know it is not a very sound method but from memory would say it's as good as the Delos.

Dunk,

If you were closer I would be happy to loan you it, I keep thinking of doing a write on the Meade 40 SWA and it, I have a couple of scope I could use it in, sadly they vignette on the 180mm Mak.

Alan

[John]

I like the 6mm Ethos a lot too Alan but I have a nagging desire to try a 6mm Delos and see how it compares. Maybe I'll get a chance at the SGL star party next year, if I can wait that long !

[Stu]

I've never been in a position to compare the same focal length of Delos vs Ethos but have always assumed they are same quality with just the fov/eye relief differentiating them. Is there a view that the Delos may be better?

Stu