87 replies to this topic

[HellsKitchen]

In keeping with my intended theme of big eye lenses, immersive viewing and reasonably wide FOVs, this is the last piece of the puzzle. I have a 12.5 , 17.5 Morpheus, and will be getting the rest except the 14, and I need a 3.5mm  extension to the regime. 

 

How does the Delos compare to the XW? My scopes are a 12" F/4.4, and 8" F/6, both dobs. I was considering a 3.5 Nagler, but scratched that as research has told me that the Delos has better transmission and may be sharper. And ofcourse, there is the immersion factor. Big eye lens. The XW, has 2* smaller FOV (yes, that bothers me),  is about 90g lighter, and significantly cheaper. How does it compare to the Delos in terms of transmission, edge performance, and all round comfort? Never used either. For reference, I use Delites, the two aforementioned Morpheus focal lengths, and a 26T5 Nagler. At this F/L, my main targets would be Lunar, globulars, planetary nebulae, and small faint galaxies. How would either of these fit in with a set of Morpheus, 2.5 and 5x Powemates, and a possible 3x barlow (which I am also considering, to fill in some gaps). 

 

So, basically, at the end of the day, shall I get the turkey leg, or get the slightly less plump turkey leg?

Edited by HellsKitchen, 01 May 2024 - 08:24 AM.

[Starman1]

model lab measurements

(no 3.5 Delos tested)    FL        AF          f/4         f/4       f/4        f/10      f/10      f/10             aberrations in order of importance, distortion

Pentax XW                   3.5       68.5       Diffr      Diffr      12       Diffr      Diffr      8                CA 10%

Tele Vue Delos             4.5       73          Diffr        6        10        Diffr      Dif?      Dif??         Ast.,FC,CA +16%

 

Rankings are Center of field/Mid way to edge/edge of field.

numbers of 10 or less are essentially perfect.

 

In my experience, the Delos has a bit more effective eye relief for glasses use.

Otherwise, both would be pretty decent eyepieces.

 

3.5mm is a very high (522x) magnification in my 12.5" scope, and both require a night of superb seeing, so I compared them,

and a few others, in my 4" f/7 apo, where the 204x/0.5mm exit pupil was used on double stars.

At least for close doubles, the Delos 3.5 was a bit sharper at the edge of the field at f/7, and the field stop size was small enough that field curvature in the scope

shouldn't matter.  The 3mm Delite was sharper than both the XW or Delos at the edge, but its smaller field was probably the reason.  At the 60° point, the wider eyepieces

were pretty much the equal of the Delite.

 

I saw perfect star images in the center in 3.5 XW, 3.5 Delos, 3mm Delite, 3.5mm XWA, 3.7mm Ethos, with a slight edge to the Ethos 3.7mm.  I've seen its sharpness in the 12.5", too, so I don't think it was simply a magnification difference.

On the Moon, all had very good contrast, but the XWA had a very soft image near the edge of the field (whether FC or Astig., I couldn't tell, but it wasn't from the scope since the 3.7 Ethos was sharp at the edge).

I didn't have a 3.5mm Nagler at the time, so I did not compare it.  Jon Isaacs has some experience with that eyepiece, so perhaps he could comment.

 

All in all, whether 3.5mm XW or 3.5mm Delos, I think you'd be happy when the seeing was good enough to use a 3.5mm eyepiece.

[RAKing]

The only differences I can point out are that the Pentax XW3.5 is parfocal with the other small XW eyepieces, and the Delos is parfocal with the shorter Delos.  So if you were moving down the progression, it would be easier to stick with the same brand to avoid re-focusing.

 

But since you are planning on a Morpheus line, I don't know how much re-focusing you will have to do from the Morpheus 4.5mm to either company's 3.5mm.  I have owned both, used both, and like both!  I still have my full set of Pentaxes, so I still have the XW3.5.

 

Cheers,

 

Ron

[HellsKitchen]

The only differences I can point out are that the Pentax XW3.5 is parfocal with the other small XW eyepieces, and the Delos is parfocal with the shorter Delos.  So if you were moving down the progression, it would be easier to stick with the same brand to avoid re-focusing.

 

But since you are planning on a Morpheus line, I don't know how much re-focusing you will have to do from the Morpheus 4.5mm to either company's 3.5mm.  I have owned both, used both, and like both!  I still have my full set of Pentaxes, so I still have the XW3.5.

 

Cheers,

 

Ron

 

I don't mind refocusing, some people get **** if they have to refocus 1mm between their eyepieces, that's not me, as long as the focal range falls within the range of the 1.5" travel of a Moonlite and Feathertouch I am good

[csrlice12]

Don't fear the twirly knobs.

[SeattleScott]

I don't mind refocusing, some people get **** if they have to refocus 1mm between their eyepieces, that's not me, as long as the focal range falls within the range of the 1.5" travel of a Moonlite and Feathertouch I am good

Well with TV it is more like 6mm. And at such high powers, where focus is so sensitive, parfocal eyepieces are convenient. I don’t really care much at medium or low power.

[Starman1]

The only differences I can point out are that the Pentax XW3.5 is parfocal with the other small XW eyepieces, and the Delos is parfocal with the shorter Delos.  So if you were moving down the progression, it would be easier to stick with the same brand to avoid re-focusing.

 

But since you are planning on a Morpheus line, I don't know how much re-focusing you will have to do from the Morpheus 4.5mm to either company's 3.5mm.  I have owned both, used both, and like both!  I still have my full set of Pentaxes, so I still have the XW3.5.

 

Cheers,

 

Ron

Pentax and Morpheus are parfocal.  Delos requires 6.35mm of out-travel.

Edited by Starman1, 01 May 2024 - 02:55 PM.

[HellsKitchen]

That makes me lean more towards the Pentax then...

[HellsKitchen]

However, Don's post suggests that the XW has a 68.3* fov and the Delos 73*? If so, then there is only one choice.. the Delos...

 

68* is not gonna cut the mustard. I'll go ahead and focus the 6mm.

Edited by HellsKitchen, 01 May 2024 - 07:25 PM.

[ausastronomer]

Hi Sab,

 

Caveat: I've never compared these 2 eyepieces directly.

 

I have all of the 1.25" Pentax XW's, including the 3.5mm and I have the 6mm Delos jammed in between the 5mm and 7mm Pentax XW's.  I've had all of these for a long time.

 

The 3.5mm Pentax XW is an outstanding eyepiece.  Not one thing anyone could complain about with it.

 

I've spent quite a bit of time comparing the 6mm Delos with the 5mm and 7mm Pentax XW's.  While a direct comparison is difficult due to the focal length differences in the short focal lengths, all 3 of them are excellent eyepieces.

My preference is for the XW's over the Delos, by a very small margin.  Optically they are very similar, in terms of sharpness, contrast & transmission, but I see less lateral color in the Pentax XW's than the Delos.  Put Sirius, Jupiter or the Moon, right at the EOF and you will see more lateral colour in the Delos than the XW's.  The XW's are also shorter and lighter for a similar focal length and IMO a bit more comfortable to use. I also prefer the twist up eye cup system on the XW over the Delos adjustment system.   The XW's are also Waterproof to 1 metre.  While you won't be taking either swimming, it gives you comfort in regard to dew protection, or a little bit of rain.

 

On the basis that the XW's are significantly cheaper, it's a bit of a no brainer for mine.

 

Cheers

Edited by ausastronomer, 01 May 2024 - 07:28 PM.

[Starman1]

However, Don's post suggests that the XW has a 68.3* fov and the Delos 73*? If so, then there is only one choice.. the Delos...

 

68* is not gonna cut the mustard.

We don't know exactly what the 3.5mm Delos' apparent field is.

It might be 72°.

 

Field stops are indicative:

XW 3.5---4.2mm field stop

Delos 3.5--4.4mm field stop

So just a hair more true field in the Delos.

If the focal lengths are accurate, that means the Delos has just a hair more apparent field as well.

[ausastronomer]

Field stops are indicative:

XW 3.5---4.2mm field stop

Delos 3.5--4.4mm field stop

So just a hair more true field in the Delos.

If the focal lengths are accurate, that means the Delos has just a hair more apparent field as well.

 

That's less than 5% difference. At the high magnification and small TFOV with this focal length, I would consider that to be inconsequential, in the field.

 

Cheers

[ausastronomer]

$aud 750-00 for the TV Delos when it's eventually in stock and available again in Australia Vs about $aud 450 for the 3.5mm Pentax XW, which is currently available in Australia.

 

Knowing what I know, there isn't even a decision to be made there.  At equal prices I'd take the Pentax.  At $300 cheaper it's not a hard decision.

 

You could of course source a 3.5mm Delos from overseas but that comes with it's own issues.  Something else to consider is that if you ever have a problem with a TV eyepiece it goes back to Televue in the USA and comes back several months later, if it's within the warranty period.

The Pentax XW's have a Lifetime Warranty and are serviced by C R Kennedy in Australia.

 

Cheers

[HellsKitchen]

$aud 750-00 for the TV Delos when it's eventually in stock and available again in Australia Vs about $aud 450 for the 3.5mm Pentax XW, which is currently available in Australia.

 

Knowing what I know, there isn't even a decision to be made there.  At equal prices I'd take the Pentax.  At $300 cheaper it's not a hard decision.

 

You could of course source a 3.5mm Delos from overseas but that comes with it's own issues.  Something else to consider is that if you ever have a problem with a TV eyepiece it goes back to Televue in the USA and comes back several months later, if it's within the warranty period.

The Pentax XW's have a Lifetime Warranty and are serviced by C R Kennedy in Australia.

 

Cheers

 

Can get a Delos landed at my door for $664 AUD from FLO. A solid $100 cheaper than the local suppliers. And they have several in stock too. They say "shop local, support local". Nope.  My money is going overseas, as it had for my last several purchases. Cheaper and actually in stock. Saved hundred of $$$ in doing so. Bought a few items in the past from EyepiecesEtc aswell, great prices and service. No regrets. Same with the Morpheus, $367 shipped from FLO, vs $449 plus shipping locally. I know what I'm doing....

 

The Pentax is about the same price as from FLO at one local online shop, so if I go that route, I may buy that one locally. About $200 cheaper and 90g lighter than a Delos.  Don says they are parfocal with the Morpheus. And reading your review, it sounds like a winner. 

Edited by HellsKitchen, 01 May 2024 - 08:45 PM.

[SeattleScott]

At such high power, I would care more about parfocal than a few % wider view.

[HellsKitchen]

According to Don's Eyepiece guide, the Pentax is a full 70*. Is that correct? Not 68.3*?

[areyoukiddingme]

70 will be the manufacturer spec, where as the latter is presumably Ernest's measurement. I'd go with the measurement. 

[HellsKitchen]

70 will be the manufacturer spec, where as the latter is presumably Ernest's measurement. I'd go with the measurement. 

 

In that case, I don't think I'd accept 68.3*, it places it halfway between the Delos and Delite, and my goal here is to expand the FOV on the Delites. I know for a fact I would notice the FOV difference. 

Edited by HellsKitchen, 02 May 2024 - 12:39 AM.

[areyoukiddingme]

I personally find the apparent field on the 3.5 XW to be tight. In comparison, despite being essentially the same apparent field, the others feel more expansive. Evidently apparent field and magnification combine to have a perceptual effect on apparent field, at least for me.

[HellsKitchen]

I personally find the apparent field on the 3.5 XW to be tight. In comparison, despite being essentially the same apparent field, the others feel more expansive. Evidently apparent field and magnification combine to have a perceptual effect on apparent field, at least for me.

 

Would you say that the 3.5 Delos feels more expansive?

[areyoukiddingme]

No clue, haven't compared. I'd think they will feel very similar being only ~4 degrees different. Probably only noticeable on back-to-back testing.

[SeattleScott]

My max power eyepiece is a 3.4mm with 42 AFOV. It doesn’t feel cramped to me because of the targets I use it on. My other focal lengths are 72-82 AFOV (ok a 42LVW in there at 65). At 3.4 mm I am either looking at something small like a planet or double star, where all my focus is on this small object, or looking at the Moon, which is feature rich and the narrow AFOV helps cut down the glare.

You are concerned you would notice a few degrees less AFOV. I can guarantee you will notice having to refocus 6mm.

[Kutno]

How does the Delos compare to the XW? ... in terms of transmission, edge performance, and all round comfort? ... my main targets would be Lunar, ...

 

Both are excellent instruments.  I have no issues with either regarding the three measures for which you are seeking comment.  What I can share, perhaps of relevance to you, is that the 3.5mm Delos has been used by me in a 10" Dob, possessing a Zambuto mirror, at 363x on the Moon.  Images of the outer slopes of Crater Rutherfurd, Rima Birt, the Pico mountains, and other features, were spectacular!     

Edited by Kutno, 02 May 2024 - 12:29 PM.

[TayM57]

Would you say that the 3.5 Delos feels more expansive?

Yes. I've had both, and the Delos felt more immersive.

 

There was a discussion about this a year or so ago. Don commented on this, and the consensus was this was down to how the exit pupil was shaped + size of eye lens. I can't remember exactly but yes, certain EPs feel more immersive than others of similar FL and AFOV. 

 

The Delos + Pentaxes are good examples of this. The Delos to me, feels more immersive than the Pentaxes do. 

 

Richard likes to call the UFF 30MM a honorary Morpheus but I'm more of the thinking that the UFF 30 is more like a Pentax than a Morpheus. 

[areyoukiddingme]

Yes. I've had both, and the Delos felt more immersive.

 

There was a discussion about this a year or so ago. Don commented on this, and the consensus was this was down to how the exit pupil was shaped + size of eye lens. I can't remember exactly but yes, certain EPs feel more immersive than others of similar FL and AFOV. 

 

The Delos + Pentaxes are good examples of this. The Delos to me, feels more immersive than the Pentaxes do. 

 

Richard likes to call the UFF 30MM a honorary Morpheus but I'm more of the thinking that the UFF 30 is more like a Pentax than a Morpheus. 

 

When I compared the 30 XW with the 30 UF, the XW seemed like it had a bigger apparent field, but the opposite is true.