6mm Televue Delos and 6mm TV Radian comparison

[ausastronomer (John Bambury)]

Hi all,

I have taken advantage of the Televue sale and a new Televue 6mm Delos is now winging its way to beautiful Kiama on the NSW South Coast. I am sure it will be very good.

The 6mm focal length is one a have a need for, particularly in my 10" and 14" scopes, where it gives 214X and 267X respectively.

I have been asked by the retailer to submit a review to IIS and Cloudy Nights and also for uploading to their website, which I am very happy to do. I will compare it to the 6mm Televue ETHOS and the 6mm UO HD ortho, both of which are high quality performers.

What I would like to do is get hold of a 6mm TV Radian so that I can throw that into the review for comparison purposes as another high quality 6mm eyepiece, with 20mm of eye relief. If anyone has a 6mm TV Radian they would be prepared to loan me for up to about a month, for the purpose of the review I am happy to cover the registered postage cost both ways. You can be rest assured it will be treated with kid gloves, like I treat all my equipment; and returned in exactly the same condition I receive it in. Of course the provider of the 6mm Radian would be credited in the review.

Cheers,
John B

[wavelandscott (Scott)]

I am hopeful that you get fine weather to complete this comparison. What scopes will you use? Can you throw a high quality refractor into the mix?

[PlanetMan]

For my own two cents worth (and assuming this isn't already on the cards) is there any chance of putting in a Pentax XW 5 or Pentax XW 7 into the mix - or is this likely to cause too many problems.

I personally think this is the clincher a lot of people would like to know about in terms of the Delos and how it compares with the venerable Pentax XW's.

[ausastronomer (John Bambury)]

Originally Posted by wavelandscott

scopes will you use? Can you throw a high quality refractor into the mix?

Hi Scott,

The 2 main scopes I will be using are my 10"/F5.3 newtonian with Suchting mirror and my 14"/F4.5 newtonian, with Zambuto mirror.

Both of those scopes are excellent optically. I will also use the 18"/F4.5 Obsession when seeing conditions permit. The 6mm Delos will give 350X in that scope, so it won't be useable all the time. I will do the evaluation with and without a paracorr in all the scopes. The 14" and 18" scopes have servocat tracking so they do give you the opportunity for critical high power evaluation.

I don't usually use refractors, except as finderscopes, as I am not an imager. However, I am hoping to gain acccess to an ED80, which is owned by a friend, for a night or two.

Originally Posted by PlanetMan

For my own two cents worth (and assuming this isn't already on the cards) is there any chance of putting in a Pentax XW 5 or Pentax XW 7 into the mix - or is this likely to cause too many problems.

I personally think this is the clincher a lot of people would like to know about in terms of the Delos and how it compares with the venerable Pentax XW's.

Unfortunately at these short focal lengths a 1mm difference in eyepiece focal length makes a fairly big difference in magnification and it is impossible to directly compare and critically evaluate a 6mm eyepiece with a 5mm or 7mm eyepiece. For instance in my 10" scope those 3 eyepieces give 185X, 217X and 260X which is just too big a gap IMO. In the larger scopes the gap is even wider. In the 18" scope those 3 eyepieces give 300X, 350X and 420X respectively.

I do have a 1.8X TV barlow, a 2.5X TV powermate and a 2" 1.6X Antares barlow. I can put the 14mm Pentax XW into the 2.5X powermate for 5.6mm. The 10mm Pentax XW into the 1.8X TV barlow for 5.6mm and the 10mm Pentax XW into the 1.6X Anatares for 6.25mm, which is as close as I can get. I will certainly do that evaluation but it will be ever so slightly inherently slanted due to the fact that whichever barlow I use, it introduces additional glass into the light path.

Cheers,
John B

[anj026]

John is there any chance of comparing the 3-6mm zoom also (at the 6mm setting)?

[ausastronomer (John Bambury)]

Hi Andy,

I don' have a TV 3-6 zoom, nor do I know anyone that has one. It would be interesting to throw it into the mix.

Cheers,
John B

[ausastronomer (John Bambury)]

Good afternoon all,

The 6mm Delos arrived this morning. I knew it was coming because clouds engulfed the Illawarra/Shoalhaven Shires in the early hours of this morning

I have to say out of the box I am really impressed with it’s physical looks. Build quality is very good and the eye lens is really wide and immersive. The adjustable eye guard is a dramatic improvement over the “instadjust” system on the Nagler T4’s and the Radians. The adjustable eye guard is all metal and in two halves, it slides up and down and the top part is basically a lock ring which you activate by twisting about a ¼ turn. Very impressive that adjustable eye guard in fact. It is a similar physical size to the 5mm Pentax XW but somewhat heavier than that eyepiece. It is heavy enough that it may cause balance issues in some small dobs with small bearings, that experience balance issues with heavier eyepieces.

Andrew Lockwood (alocky) has kindly agreed to loan me a 6mm Televue Radian and Andy Jackson (anj026) has kindly agreed to loan me a Televue Nagler 3-6mm Zoom, for the purposes of the review. Hopefully throwing the zoom into the review might also allow me to draw some conclusions regarding the 6mm Delos compared to the 5mm Pentax XW. I can then draw parallels through the zoom at 5mm and 6mm and also through using my 5mm and 6mm UO HD orthos.

Over the coming weeks I will use all of the eyepieces on the available solar system targets, which at the moment are really limited to The Moon and Jupiter. I will also use them on a large number of testing DSO's including double/multiple stars, galaxies and planetary nebula. I will be at Coonababrabran next new moon for the 3RF Post Eclipse Star Safari and that will give me a good opportunity to run them through their paces on DSO's.

Stay tuned for some preliminary reports on the 6mm Delos under the stars when the weather clears.

Cheers,
John B

[ausastronomer (John Bambury)]

Good evening all,

Courtesy of another very generous IIS forum member, Glenn Dewes (Glnn_23), I have been able to add a 6mm Carl Zeiss Jena orthoscopic into the comparison also. This is a .965" eyepiece which sits in a .965"/1.25" adaptor.

I have used a couple of these over the years and on axis they are very good, as is anything with Zeiss in its name. This is the first time however that I have had the opportunity to do a direct comparison.

Cheers,
John B

[bobson (Bob)]

John,

I think a lot of people have or are likely to buy 6 mm TMB planetary. It would be interesting to see how this eyepiece performs as well?

cheers

[ausastronomer (John Bambury)]

Hi Bob,

I don't have one of those but if someone wants to send me one post haste I am happy to include it.

That would really be about the limit of what I could include and get through on a timely basis, so as to return peoples eyepieces when I indicated I would return them.

Quite a few people would probably also like to see lots of other eyepieces in the mix also. For instance, the 6mm Orion Edge On Planetary eyepiece, or one of its clones, compared to the higher end eyepieces as well, but unfortunately I don't have one of those and I can't include everything due to time constraints.

Cheers,
John B

[ausastronomer (John Bambury)]

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,
John B

[mercedes_sl1970]

John - thanks for the initial impressions. Look forward to reading more.

Andrew

[ausastronomer (John Bambury)]

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,
John B

[davewaldo]

Thanks John, looking forward to hearing more

I'm looking to upgrade some of my EPs and I'm specifically looking at the Delos / pentax or whatever else might be good.

Thanks for your efforts so far

Dave.

[anj026]

Thanks John,

I like these side by side comparisons, best way to get an understanding of the pro's and con's of each eyepiece.

Keep up the good work.

[alocky (Andrew lockwood)]

Thanks John - looks like I'll be keeping the Radian then! It always worked well in my 10", but I'll be interested to see your impressions at higher magnification. I rarely get seeing conditions that let me use it in the 25".
Cheers,
Andrew.

[Rodstar (Rod)]

Great reading so far John. Looking forward to hearing further comments, especially if you can get good enough conditions to observe at this focal length with the 14" SDM.

I had hoped I might be able to accept your kind invitation to join you with my ED80 to do some testing, but it is going to be a good month or so before I can get down to visit you. I suspect you will be completely done by then!

[Phoenix (Steve)]

Thanks John for the review so far - very interesting read. John, you mentioned in your original post that you would be comparing a 6mm TV Ethos - I assume you were not able to add the ethos to the mix in the end???

Cheers
Steve

[ausastronomer (John Bambury)]

Originally Posted by Phoenix

John, you mentioned in your original post that you would be comparing a 6mm TV Ethos - I assume you were not able to add the ethos to the mix in the end???

Cheers
Steve

Hi Steve,

That was my mistake. I thought we had a 6mm and an 8mm ETHOS as part of our stable of 3RF eyepieces, but in fact we have 2 x 8mm ETHOI as well as some of the longer focal lengths. This unfortunately meant I didn't have access to the 6mm ETHOS that I thought I had.

I actually don't use the ETHOS eyepieces as they don't have enough eye relief for me, so I was running on memory, which obviously isn't what it used to be.

Cheers,
John B

[ausastronomer (John Bambury)]

Originally Posted by Rodstar

I had hoped I might be able to accept your kind invitation to join you with my ED80 to do some testing, but it is going to be a good month or so before I can get down to visit you. I suspect you will be completely done by then!

Hi Rod,

Well a couple of the guys who have loaned me the eyepieces are happy for me to have them until the end of November, which is very kind of them.

I am returning from a few days at Coonabarabran on Wednesday 21st November. If you could do the Friday night (23rd) or Saturday night (24th) immediately after I return from Coonabarabran that would work well because the moon will be 8/9 days old then and offers good views of some very testing targets in an 80mm scope. eg The craterlets in Plato and the Alpine Valley.

Work on it and see if it can happen.

Cheers,
John B