Denk D21 How good?

[skies2clear]

Hi all,
Would anyone here have any thoughts how the D21's perform? I'm thinking of getting a pair for Binoviewing. The other option is another Pentax 20XW. Wonder how these 2 compare?

I realise the Denks are lighter and smaller than the XW's so would suit Binoviewing, but I'm more interested how they compare optically.

Thanks in advance,
Nick

[wavelandscott (Scott)]

I have not compared the 2 types side by side...

I do have a pair of the Denks (14 mm and 21 mm) and would stack them up positively versus many other eyepieces.

Another consideration might be the 24 Pans...which are also pretty spiffy.

[rmcconachy]

Like Scott I have not compared the Denk 21mm and Pentax XW 20mm with each other. In fact I have never looked through an XW 20mm. However, I do have a pair of Denk 21mm oculars and some different focal length XW eyepieces (<=10mm and 30mm) and I like both. The apparent field of view of the XW is a tiny bit larger (70° versus ~65°). Both series of oculars offer plenty of eye relief, even for those of us who wear spectacles. I guess the best I can offer is that there is probably no bad choice between the two. As Scott points out there are other options you might want to check out, e.g., the Panoptic 24mm (vignettes a little in the Denk II with a PowerSwitch, check your binoviewer's clear aperture) and the Vixen LVW 22mm to name just two.

Clear skies and happy binoviewing with whatever you choose!

[skies2clear]

Thanks for the comments so far.

The Pan 24's weren't something I thought of previously to be honest. I'm also going to use whatever I decide on with Denk II and Power Switch (and 2" OCA for Newtonian) by the way.

I have heard a lot of really good things about the D14's, but not as much about the D21's.

Also, I have been under the impression, perhaps wrongly, that the Pans are slightly inferior optically to the Denks or XW's, but I guess as usual, the differences between premium oculars is small indeed.

Thanks again

[wavelandscott (Scott)]

I do also have a 24 Pan and think the D21 compares very well with it.

They are both fine eyepieces...

I only have one 24 Pan so I've not Binoviewed with it in comparison. I don't think you can wrong either way and I do like the D21s in the Binoviewer (and the D14s too).

[skies2clear]

Thanks Scott, appreciate your comments. They are all great eyepieces by the LOOKS of it

[ausastronomer (John Bambury)]

Hi Nick,

I haven't been able to compare them side by side. I have used the D21 and own the XW20. If I was starting again I would probably opt for the D21 as it definately has a flatter field than the XW20. If you use a paracorr the XW20 is flattened very nicely and may be the eyepiece of choice. In the absence of a paracorr I think the D21 definately has a nicer EOF.

Cheers,
John B

[skies2clear]

Hi John,

thanks for replying. Apart from the EOF performance, weight and AFOV, do you think the Denk is equal to the XW for transmission and overall optical quality? I know (usually) differences between premium optics in contrast/scatter etc is small,

Regards
Nick

[ausastronomer (John Bambury)]

Originally Posted by skies2clear

Hi John,

Do you think the Denk is equal to the XW for transmission and overall optical quality?

Regards
Nick

Hi Nick,

It's right up there. As I mentioned I haven't A/B'ed them, only used them individually. When using them on different nights in different scopes it's hard to get a handle on a direct comparison, when they are so close, but I can tell you the 21mm Denk is a very high quality eyepiece in terms of its optical performance. It's EOF is very good, not perfect, but it's better than the 20mm XW. A paracorr would likely flatten it out like it does with the 20mm XW.

I have A/B'ed the 14mm XW and 14mm Denk and the Denk is every bit the equal of the XW, if not a touch better in a couple of criteria. It's a pity they are not available in more focal lengths.

Cheers,
John B

[mercedes_sl1970]

Hi Nick

I have the Denk 21s and there is a little degradation at the edge in my F6 100mm binos. In an F13 100mm refractor, it just doesn't exist (to my less than discerning eyes)... For me they are excellent eyepieces. The light throughput is very good and they have very good contrast and a fairly neutral colour rendition.

Just out of curiosity - can anyone comment on edge performance with the Panoptic 24s?

Andrew

[skies2clear]

Thanks John and Andrew,

If the Denk 14's compare very well with XW14, then that is promising indeed. I already have a pair of XW14's so will hang onto them at this stage and tempted to get a pair of D21's. While I can bino XW's Ok, they are reasonably bulky and heavy, so I see the Denks having an advantage there.

Mind you, I'm not exclusively a Binoviewer user and do like single-eyed viewing very much too, and for this reason I don't want to overspend for the privilege of 2 eyed views. So considering cost into the decision, the asking price of a pair of Denks seems reasonable for premium optics.

Cheers
Nick

[ausastronomer (John Bambury)]

Originally Posted by mercedes_sl1970

Hi Nick

Just out of curiosity - can anyone comment on edge performance with the Panoptic 24s?

Andrew

Hi Andrew,

The 24mm Panoptic is an excellent eyepiece. It does have a couple of shortcomings in the criteria which are important to me. They aren't the important criteria to some, who place edge performance as the single most important criteria. Edge performance with the 24mm Pano is exceptional. It also has a lovely flat field from edge to edge. It is also very sharp. Where it comes up short for mine is that eye relief is too short to use with eye glasses on and due to a combination of light transmission and contrast it doesn't go as deep as my 20mm XW, which has almost the same TFOV. It also has noticeable rectilinear distortion which is evident when using it in the daytime, or when paning the sky with a dob. It is one of the best eyepieces at this focal length.

Cheers,
John B

[mercedes_sl1970]

John - thank you. That's very helpful.

Regards

Andrew