42 replies to this topic

[ausastronomer]

Good afternoon all,

As I indicated in another thread I went ahead and ordered the 6mm Delos last week, as this is a focal length I have a need for in my 10" and 14" scopes.

The retailer asked me to write a review on the 6mm Delos for their website and an Australian based online astronomy forum. I suggested I could do better than that and would do a comparison with several other premium 6mm eyepieces and also post the comparison on Cloudy Nights.

I have available for the comparison the following contenders.

6mm Televue Delos
6mm Televue Radian
6mm UO HD orthoscopic
3mm to 6mm Televue Nagler Zoom.

These 6mm eyepieces will give me 225X in my 10"/F5.3 scope and 267X in my 14"/F4.5 scope. The mirrors in both scopes are exceptional. The 10" SDM has a Mark Suchting mirror and the 14" SDM has a Zambuto mirror.

I will conduct the comparison over the next few weeks on solar system targets, which at the moment are limited to the Moon and Jupiter. I will also do a detailed comparison with these eyepieces using DSO's including galaxies, planetary nebula, extra galactic globulars and open clusters in the LMC and SMC, double stars and multiple star systems. I will also use targets like the homunculus in the Eta Carina Nebula. I will choose targets that contain testing detail on the threshold limit for the respective telescope I am using at the time. I am heading to Coonabarabran for 4 days over the November New Moon to entertain 22 visiting Canadian Astronomers. I am sure this will give me some times to test all the eyepieces on some testing DSO's.

I will continue to post my respective "preliminary" impressions on all the eyepieces in this thread. I will post a detailed review once properly completed for uploading to this website.

I will also compare these 6mm eyepieces to my barlowed Pentax XW's, but I will not include this comparison in my final review, as the focal lengths will be slightly different to 6mm. I can get to 5.6mm by barlowing the 14mm and 10mm Pentax XW's and to 6.25mm barlowing the 10mm Pentax XW. In addition, once you introduce a barlow into the equation (no matter how good) it is not necessarily a fair fight as the barlow has to introduce some very minor light loss. Whilst this would not be detectable in many cases, I don't believe it is comparing "apples with apples". I will also do a comparison with the Nagler zoom set to 5mm and directly compare this to the 5mm Pentax XW and the 5mm UO HD ortho. This may enable me to draw some parallels there to the 6mm Delos. Similarly, I will not post this comparison in my final review as again we are not comparing "apples and apples". Any conclusions would be resulting from an A V B and B V C comparison, drawing a conclusion about A V C, not directly comparing A V C. Further, there may be very slight performance differences between the Nagler zoom set at 5mm and 6mm. Similarly, there may be very slight performance differences between the 5mm and 6mm UO HD orthos. I will post all of my findings in regard to the 5mm eyepiece performance and the barlowed XW performance in this thread. I may also write up a separate review with the 5mm Pentax XW, 5mm UO HD ortho and the 3mm to 6mm zoom set to 5mm.

Stay tuned, I will be out there looking at the Moon and Jupiter as soon as the clouds part.

I have to say I am quite impressed with the looks of the 6mm Delos. I really like the way Televue have done the adjustable eyeguard in two halves with the lock ring. I am really impressed with this adjustable eye guard system and have to say it is IMO a monumental improvement over the instadjust system found on the Radians and Type 4 Naglers.

PS: I was also hoping to have a 6mm ETHOS to throw into the mix, as I thought we had a 6mm ETHOS in our 3RF Australia arsenal of eyepieces. Unfortunately the eyepiece I thought was a 6mm is in fact an 8mm ETHOS and not suitable for using in this comparison.

Cheers,

[Damo636]

I'll be watching this one with interest John, as I have owned all but the zoom in your line up. I found the 6mm Delos to be exceptional & will be replacing it at the earliest opportunity.

[ausastronomer]

Update

Courtesy of another generous Aussie observer I now have a 6mm Carl Zeiss Jena orthoscopic on its way to me for inclusion in the comparison.

Cheers,

[dcoyle]

How interesting. Thanks for taking the time to post.

Dan

[dvb]

Looking forward to your review - I have the 3-6 zoom, and a 6mm Baader Genuine Ortho, so I am looking forward to your comparison with the 6mm Delos.

[Sarkikos]

I found the 6mm Delos to be exceptional & will be replacing it at the earliest opportunity.

If the 6mm Delos is so exceptional, why are you replacing it?

Mike

[ibase]

I found the 6mm Delos to be exceptional & will be replacing it at the earliest opportunity.

If the 6mm Delos is so exceptional, why are you replacing it?

My Delos 6mm isn't going anywhere and will stay put in the stall.

Best,

[Damo636]

I found the 6mm Delos to be exceptional & will be replacing it at the earliest opportunity.

If the 6mm Delos is so exceptional, why are you replacing it?

Mike

I sacrificed the Delos along with my 26 Nagler to fund the 21 Ethos. I figured I could temporarily recreate the 6mm focal length with the 10mm XW/Antares 1.6X. I will be replacing it at some point, hopefully in the not too distant future, as well as adding a 5mm XW to top out my high power line up.

[GeneT]

Let 'er rip!

[johnnyha]

I found the 6mm Delos to be exceptional & will be replacing it at the earliest opportunity.

If the 6mm Delos is so exceptional, why are you replacing it?

Mike

I sacrificed the Delos along with my 26 Nagler to fund the 21 Ethos. I figured I could temporarily recreate the 6mm focal length with the 10mm XW/Antares 1.6X. I will be replacing it at some point, hopefully in the not too distant future, as well as adding a 5mm XW to top out my high power line up.

Strange and interesting. So what are you replacing it with?

[Damo636]

I found the 6mm Delos to be exceptional & will be replacing it at the earliest opportunity.

If the 6mm Delos is so exceptional, why are you replacing it?

Mike

I sacrificed the Delos along with my 26 Nagler to fund the 21 Ethos. I figured I could temporarily recreate the 6mm focal length with the 10mm XW/Antares 1.6X. I will be replacing it at some point, hopefully in the not too distant future, as well as adding a 5mm XW to top out my high power line up.

Strange and interesting. So what are you replacing it with?

The wording of my original post could have been better, I will be "reacquiring", not replacing the 6mm Delos

[Mr. Marbles]

Looking forward to this report.

[ausastronomer]

Good evening all,

I was able to get some of these eyepieces out under the stars for the first time tonight. I have not previously used the 3mm to 6mm Nagler Zoom or the 6mm TV Delos. The 6mm CZJ ortho should arrive tomorrow. As I didnt have all the eyepieces I didnt want to do anything too serious, but wanted to at least give the eyepieces I hadn't used before a fly.

I used the 10" and 14" scopes. The 18" er stayed in bed.

Seeing wasn't good enough for a 6mm eyepiece to really hold up well in either telescope and as time went on it started to deteriorate, so all scopes are now sleeping.

The four 6mm eyepieces I tried tonight were the 6mm Radian, 6mm Delos, 3mm -6mm Nagler Zoom and the 6mm UO HD ortho. Seeing wasnt good enough for any super critical evaluation at this magnification but I did spend some time studying the terraced wall craters in Mare Imbrium, as these have good reflection angles at this moon phase. I mainly worked on craters Aristillus, Timocharus and Archimedes. I also spent time on Copernicus.

Some preliminary observations.

All four eyepieces are very good. There are no lemons amongst them.
It was very difficult under tonights variable seeing conditions to separate them optically on any of the targets. To split them is going to take good conditions and a good telescope. Even then the differences are going to be fairly subtle in any case.

The Delos and the Radian are easily the most comfortable to use, followed by the Nagler zoom which was also pretty good and the UO HD ortho brought up the rear here, with its tight eye relief and tiny eye lens.

The Delos and the UO HD ortho had a nice cool colour tone, the Nagler zoom and the Radian were a bit warmer.

I found the DELOS a touch more difficult to use than my Pentax XW's, although it's still very good in this regard. It's just a bit easier to create blackouts in the DELOS trying to take in the full FOV, than it is in the XW's. This could also stem from the fact that I have been using my XW's for 10 years and the DELOS for 10 minutes. That having been said I really didnt have any trouble with the DELOS you just have to focus on getting your eye placement right, a bit more than you do with the XW's or the Radians for that matter.

What I can tell you at this point in time is that I like the DELOS a lot and it is a keeper.

Stay tuned. Hopefully I will get some more stable seeing over the weekend.

Cheers,

[george tatsis]

Hope the weather clears up and you get the optimum seeing conditions for this very interesting shoot-out.Keep your reports coming John !

[ausastronomer]

Good Afternoon All,

I was able to spend about 2.5 hours last night with these eyepieces in my 10"/F5.3 scope. I haven't had this scope all that long and it was a good opportunity to further evaluate the scope also.

Unfortunately the 6mm Carl Zeiss Jena orthoscopic would not come to focus in this scope. It needed about another 6mm or 7mm of focuser intravel to reach focus. As this scope only has 2 collimation bolts on the primary mirror cell (as opposed to the normal 3) I can't push the mirror any further up the cell to adjust the focus point. I am pretty sure this eyepiece will reach focus in my 14"/F4.5 SDM and my 18"/F4.5 Obsession as these scopes are optimised for use with a paracorr which requires more inward travel than a normal eyepiece. However it may not be so easy to get seeing conditions good enough to support the power these eyepieces give in those scopes.

Last night I spend quite a while using Achernar and testing for things like On Axis Star Image Sharpness, Off Axis Star Image Sharpness, Lateral Colour, Internal Reflections and Light Scatter. I also spend some time on the full Moon. As you all know the full moon isn't the ideal time to observe it and do critical evaluation, but I thought I would see if these conditions showed any glaring differences between the eyepieces. The lunar targets I used were around Mare Fecunditatus. I used some craters which had some mountains and internal craterlets, including craters Goclenius and Langrenus. I also spent some time on Dorsa Geike which is a ridge about 250km in length.

As I indicated previously these are all very good high quality eyepieces with excellent on axis performance and the differences between them are going to be fairly subtle. I went into this evaluation very open minded and wanted to evaluate everything 100% objectively. However, I did feel that with the advantage of 15 years of technological advancement the DELOS would be a slightly superior performer to the TV Radian. Well I can tell you the Radian is in this fight right up to it's ears. Whilst I have only compared all the eyepieces on bright high contrast targets up to this time, whatever I have been able to see in the DELOS, I have been able to see in the Radian. In a couple of tests using Achernar the Radian outdid the DELOS. Maybe things will change when we get to dimmer threshhold targets where the expected gains from contrast/light throughput advances in technology, will be more evident and favour the DELOS. On axis sharpness and observable detail with the Nagler Zoom and the UO HD Ortho have also been the equal of the DELOS and Radian, but they have fallen slightly short of the others in a couple of other criteria like scatter control etc when tested on Achernar just outside the EOF. In some of the testing I did on Achernar, the Radian outpointed the DELOS, notably scatter control when Achernar was pushed just outside the FOV (slight advantage to the Radian) and in EOF performance as Achernar was allowed to drift from the centre of the FOV to the EOF. In the Radian the Star image stayed tight for 90% of the FOV and was still very good and useable right to the field stop. The DELOS was not as good, with the star image deteriorating from 70% of the way off axis and being essentially unuseable in the outer 10% of the FOV. Granted the DELOS has a 20% larger FOV but the Radian was clearly better in this regard for mine. I will do further critical evaluation on the EOF performance of these eyepieces using some testing double stars over the coming weeks. This testing was also conducted without a paracorr and when seeing permits I will also conduct these tests with a paracorr in the 14"/F4.5 scope.

If you own any of the eyepieces in this review you can take comfort from the fact they are all very good ones with minimal differences between them on bright high contrast targets.

As an aside, whilst I didn't compare the 7mm Pentax XW to any of the 6mm eyepieces on the Moon, as the magnification difference was too great, I did include it in my evaluation on Achernar in terms of its on axis and off axis sharpness of star image, EOF lateral colour on Achernar and internal reflection and scatter control with Achernar just outside the EOF. What I can tell you is that I will not be selling any of my XW's in a hurry.

Stay tuned. Lot's more to follow as we get to some varied and more testing targets. Hopefully these will start to sort out the men from the boys.

I like the new DELOS a lot but I can tell you the 6mm Radian is also impressing me on these bright high contrast targets.

Cheers,

[Jacques]

new DELOS a lot but I can tell you the 6mm Radian is also impressing me on these bright high contrast targets.

Cheers,

Great report, cheers. Eagerly awaiting a comparison on dim threshhold targets between the Delos, the Radian and the UO HD6 ortho. The latter is my reference for (very) dim DSO in that magnification range, so I'm pretty curious.

[jrbarnett]

"To split them is going to take good conditions and a good telescope. Even then the differences are going to be fairly subtle in any case."

Well said, John, and also almost always the case.

I too just obtained a 6mm Delos. Haven't first lighted it yet, though. My stable is a bit thin at 6mm too, consisting of the Delos, a 6mm University Plossl, a 6mm Brandon, a 6mm Pentax SMC Ortho, a 6mm UO Abbe Ortho and a 6mm TMB Supermono.

Perhaps if it quits raining I'll have a chance with the Delos this coming weekend. Very much looking forward to your further updates.

Regards,

Jim

[Sarkikos]

Jim,

You have six 6mm eyepieces and you say your "stable is a bit thin"?

I thought you had thoroughly culled the herd? There is no redundancy among those six? I've never sold an eyepiece until the past two weeks, but even I let my BGO 5mm go after I got an XO 5.1.

By the way, when can we expect that article or thread about the Cleaning of the Eyepiece Hooligan's Stables? A Herculean effort it was, I'm sure.


Mike

[jrbarnett]

I've finished the first bank of stalls. More to come. I sold about 40 and bought just two. That's progress.

- Jim

[dscarpa]

Using my 17.3 Delos alone or barlowed in my IM-715, C-9.25 and WO ZS-110 stars are sharp to the edge of the FOV with the exception of a little coma with the SCT just like with the Radians I used to have. I like it better than the Radians. It's not so much that it's sharper but I prefer the Delos's cooler tone, better light transmission and clarity. I've never used it or the Radians in a newt. David

[ausastronomer]

I too just obtained a 6mm Delos. Haven't first lighted it yet, though.
Regards,

Jim

In some of the testing I did on Achernar, the Radian outpointed the DELOS, notably scatter control when Achernar was pushed just outside the FOV (slight advantage to the Radian) and in EOF performance as Achernar was allowed to drift from the centre of the FOV to the EOF. In the Radian the Star image stayed tight for 90% of the FOV and was still very good and useable right to the field stop. The DELOS was not as good, with the star image deteriorating from 70% of the way off axis and being essentially unuseable in the outer 10% of the FOV. Granted the DELOS has a 20% larger FOV but the Radian was clearly better in this regard for mine.

Hi Jim,

I know you own a few scopes. I am not sure if you have a mid aperture F5 to F6 newtonian. I was using a 10"/F5.3. Also not sure if you have a 7mm Pentax XW, I know you have some XW's as well.

I would be interested to see if you see the same thing I found with the DELOS when I let a bright first mag star (Achernar = Mag .45) drift to the EOF.

In this regard I found the 6mm DELOS to be slightly inferior to the 6mm Radian and the 7mm Pentax XW.

Overall I really enjoy the DELOS viewing experience, I was just a bit surprised it was behind the Radian and the XW on this test (they were both excellent), having regard to its design origins and breeding. I am going to repeat these tests again and also use some testing double stars at the EOF to properly evaluate this aspect of performance.

Cheers,

[jrbarnett]

Right now I have a 7mm and 10mm XWs, 4mm and 10mm Radians, 8mm LVW, and 5mm XO, so nothing really close enough that is similar to the Delos. Still, for light control and lateral color testing purposes, differences in focal length might not be such a big deal.

The best I can do is a 5.5" f/7 refractor on the not too small and slower end. My Dob is an f/5.1, alas.

Regards,

Jim

[dscarpa]

I was using my 17.3 Delos with a 5X Powermate in my WO ZS-110 for 230X-240X on the Moon and Jupiter. What can I say but yes it is all that. The combo was pulling in a lot of fine detail in Jupiter's belts and was excellent on the Moon as well. When viewing the Moon there is a ring of fire around the FOV similar to but less than my 13 Ethos. I don't find it to be an issue with either eyepiece both of which have a 3D quality for lunar. The 13 Ethos slots in nicely in my 5X Powermate line up giving me 300X-310X with the ZS. The 12 Delos I'm going to get will give me 320X-330X in it. David

[BillP]

John,

Great reports. Keep'em coming!! Question on your scatter test. Why the decision for this test to place the star just outside the field stop? I am curious because this is not a traditional approach for the common scatter most folks wonder about, which is the halo of brightness extending around a bright star or planet that is within the FOV. I am wondering if the test as you are conducting it might not also be evaluating, in addition to the traditional halo scatter, also internal baffling. So it would be a mixed scatter test if this supposition of mine is true (not sure it is...just thinking out loud). So if a star is just outside the field stop, then theoretically all those light rays should be baffled out of the light path. So if seeing some residual glow coming in then this could, it seems to me, also be the result of poorer baffling. Your thoughts?

-Bill

[ausastronomer]

John,

Question on your scatter test. Why the decision for this test to place the star just outside the field stop? I am curious because this is not a traditional approach for the common scatter most folks wonder about, which is the halo of brightness extending around a bright star or planet that is within the FOV. I am wondering if the test as you are conducting it might not also be evaluating, in addition to the traditional halo scatter, also internal baffling. So it would be a mixed scatter test if this supposition of mine is true (not sure it is...just thinking out loud). So if a star is just outside the field stop, then theoretically all those light rays should be baffled out of the light path. So if seeing some residual glow coming in then this could, it seems to me, also be the result of poorer baffling. Your thoughts?

-Bill

Hi Bill,

This test was only one of several I intend to carry out on scatter/baffling/light control. Unfortunately some cloud rolled through and interrupted my testing session the other night and I didn't get anywhere near as far as I had hoped.

I believe this test is more a test of internal baffling than anything else. However, if anyone can throw some more light on what factors are at play here, I am more than happy to take that on board. I noticed some years ago when I was playing around switching eyepieces in and out that some performed noticeably differently in this situation, than others, so it is a test I have always conducted.

The other tests I will conduct are the more tradional scatter/baffling/light control tests

eg. I will use the bright star "halo" test and I will also use some testing double stars in Orion when time and conditions permit. I will also use the multiple star HN40 in the middle of M20 when I get conditions to suit.

Cheers,