Burgess/TMB Planetary + Pentax XW 7mm comparoo

[janoskiss]

I received a 7mm Burgess/TMB Planetary eyepiece today. :) What I really would have liked is a 6mm but they are still not ready, and through circumstances which I will not go into here, I had the opportunity to acquire a 7mm, so I did for the purposes of evaluation. I have been comparing it with the 7mm Pentax XW tonight in the 8" f/6 Dob. The XW costs over 3 times as much as the Burgess so this is hardly a fair contest, but don't let that stop me.

This is not a thorough review, just what I gathered from a few hours of viewing in average seeing under light polluted skies.

What you get for around $US99 ($US110 with postage from Burgess) is amazing.

Photos show (from left to right): 7mm XW, 7mm Burgess/TMB, 8.5mm XF, 19mm Panoptic, 9mm HD ortho.

Coatings look excellent, something between Televue and Pentax coatings, but more like Televue.

Both eyepieces were as sharp as seeing allowed. I noticed nothing between the XW and Burgess ito on-axis sharpness.

The Burgess/TMB showed excellent colour correction. Less lateral colour at the edge of field than in the Pentax (at the edge of its larger field). If you put the Burgess' smaller field stop on the XW (to make its FOV the same) then the colour correction would be comparable. There is just a hint of colour around Jupiter at the edge of the FOV. The Burgess is better in this regard than what I remember of the 5mm Radian in the same scope.

Neutral colour rendition. Similar to XW.

Sharp to the edge. Not a hint of field curvature or astigmatism. This is in an f/6 scope but I have no doubt she'll go faster. :) The XW shows a bit of blue flairing from bright stars (e.g. alpha centauri) at the very edge of the field. The Burgess has virtually none of that. Again, the Burgess gives a similar view to stopping down the field of the XW.

Plenty of eye relief but considerably less than the XW. The EP is very comfortable regardless. Adjustable eyeguard extends a lot more than it needs to for me. I suppose that would come in handy when barlowing the EP which would extend the eye relief.

The EP is very well baffled. There are no reflections or glare when bright objects are in or near the FOV. I tried moving Jupiter here there, just outside the FOV, on the edge, etc, then repeated the same exercise with the Moon. I could not get any light flares, reflections or obtrusive stray light happening despite my best efforts.

The XW shows slightly less scattered light on bright objects, Jupiter and the Moon in particular, but the Burgess is very good in this regard. Certainly better than the Stratus or Nagler T6 (but the T6 is a strange design with a highly uneven distribution of scattered light across the FOV).

Perhaps related to the above, the contrast and/or transmission of the XW seemed a smidgen better on open and globular star clusters. But I could not satisfy myself that this was indeed the case, or if it was just the impression I got from the larger, more immersive FOV of the XW. I could not find any stars visible in one EP and not the other. Neverhteless, I fairly consistently got the impression that it is just a little bit easier to see things in the Pentax.

The magnification of the Burgess also seemed perhaps a little higher than the XW, maybe up to about 5% higher. I could not ascertain this though. The difference in magnification could also be responsible to the perceived better contrast/transmission of the XW. 7mm is fairly high power for an f/6 scope and DSOs start getting too dim at higher powers. Edit: Now that I think about it, there is no differences in views through the two EPs that cannot be explained by the smaller-than 60 degree FOV of the Burgess (see below).

FOV is specified as 60 degrees. On comparison with the 60 degree 8.5mm Pentax XF, the Burgess' FOV is slightly less, probably 56-58 degrees. It feels noticeably less immersive than the XF or the Meade 5000 Plossl (also has 60 degree FOV).

The adjustable eyeguard works well, but the mechanics feels a little rough compared with the XW and there is grease/oil on the threads, like the Meade 5000s have. I had to wipe the barrel clean when I first extended the eyeguard. After that the grease did not return with repeated adjustments of the eyeguard (unlike the my 5000 plossl).

I think that's about it. I have seen enough of this EP to know I will be ordering its 6mm brother when it's finally ready. The XW still rocks my observing world so I'll be putting the Burgess up for sale soon.

[janoskiss]

Amending my late night post above, I should perhaps point out that the fact that I will be putting the EP up for sale soon has not influenced my assessment of its performance in any way, and I have given my honest impression of the EP and held nothing back. There are no dislikes or quirks that I left out.

[casstony]

Nice to see a positive review on the Planetary since I have 3 of them on the way. The 3 for 2 deal on these finishes in the next day or so for anyone interested in buying them.

Tony

[iceman]

Is there a 5mm version?

I was going to get a 5mm UO HD Ortho - but this could be an alternative.

Anyone have any comments on a UO HD Ortho vs the TMB?

[janoskiss]

You'll like them Tony. Is the 3 for 2 deal on from anywhere other than HPS? I ordered goods from them before, but they charged a fortune for shipping, a lot more than other O/S dealers.

[casstony]

One review will say the ortho is better while another will prefer the TMB. My interpretation of the reviews is that the ortho provides marginally better views but the TMB is more comfortable to use. http://www.brayebrookobservatory.org/BrayObsWebSite/HOMEPAGE/BO-TMB-review.html provides the most negative review I have seen on these eyepieces, but there are plenty of positive reviews around.

Tony

[casstony]

AFAIK the 3 for 2 deal is offered at Astronomics and High point scientific, but I imagine you could get the same deal directly through Burgess. I used HPS but the eyepieces are going to a US relative then on to me to avoid the high shipping costs.

Tony

[Starkler]

Excellent report Steve :thumbsup:

I recall seeing Mike Hosea over on CN saying that these work great at f6, but off axis sharpness is degraded at f5. Apologies to Mike if I got this wrong.

I might get a 4mm for my travel scope as an alternative to vixen lv.

This eyepiece appears to be a direct competitor to the TV Radian and also the pentax XF. Steve how would you characterise the B/TMB comparing to the XF ?

[square_peg114GT]

Mike, I recently sold my 5mm UO volcano-top in favor of a 5mm B/TMB. I have the 4, 5, 7 & 9mms in route. This decision was based on both the comfort and the views I've had thru my 6mm (garage sale version). Surrounded by orthos (the recently sold 5mm & a 7mm HD) the 6mm B/TMB is getting the most focuser time. What really tipped the scale was the view I had of M13 from the Table Mountain Star Party. The view was noticeably brighter in the 6mm B/TMB then it was in the 7 HD, despite the increased magnification. I'll give the 7mm HD another chance, head-to-head with the new 7mm B/TMB before I make my final decision. Who knows, maybe I'll keep them both. I'm an eyepiece junkie. :lol:

[iceman]

Thanks Pegster, appreciate those comments.

How much is a 5mm TMB, and where is the best place to get them from?

[janoskiss]

Geoff, the XF is very much like the 10 and 7mm XW ito optical performance, but with a 60 degree FOV. The most obvious difference you will see between the XF and the Burgess is the FOV. Burgess feels a bit cramped on DSOs by comparison. The XF is wider by I'm guessing about 3-4 degrees.

I might have another look at it in the f/5 then.

Mike, HDs are on par with XWs for on-axis performance IMO. I think the Burgess is just a tad behind these two. But the short eye relief and pinhole lens would be the deal breaker for me with a 5mm ortho. The Burgess fixes all that. I think the comfort level of the Burgess would mean you'd see more with that EP. All the planetaries are $US99. I'd try ordering it directly from Burgess Optical.

Pegster, for a 6mm EP to be appear brighter than a 7mm you'd need severe deficiencies, e.g., < 74% transmission in the 7mm, and that is assuming 100% transmission in the 6mm.

btw. I corrected my comments about magnification being little higher than the XW (i.e. FL shorter). I thought about it and the diffs can all be explained by the smaller than advertised FOV.

[square_peg114GT]

Normally $99/each. High Point and Astronomics have a sale on the B/TMBs going on right now, but 2 get a 3rd eyepiece free. I ordered 3 for myself and went in with a friend on a 4th. The sale ends Aug. 31st! Some FLs are back-ordered right now (I bet they've been flying out the door) but if you order in time I think they'll still give you the deal when more come in.

Oh, I think you can get the same deal directly from Burgess, too.




Steve, I know it sounds unlikely but I'm reporting what I saw. I had to do a double take myself, I was so surprised. There are times when increased magnification can bring out faint objects that weren't visible at lower power, so maybe this had something to do with it. Also, focal lengths can be approximations. The 6mm could be 6+ and the 7mm could be 7- ?????
:shrug:

[ausastronomer]

Hmmm, thats pretty interesting because I rate the 7mm Pentax XW as about the best general purpose 7mm eyepiece money can buy at the moment.

For the Burgess/TMB to get that close is an amazing effort considering its price level. My concerns with the Burgess are that being produced in the far east, quality control may be a little variable and a few lemons may slip through the net.

Still at that price it's worth taking the risk for those on a budget.

CS-John B

[janoskiss]

I tried the 7mm in the 12" at f/5. Seeing was not up to it at all, but as far as I could tell it does very well at f/5. Just a bit of colour on Jupiter very close to the edge of field. Similar to f/6 from memory.

The thing that is by far the biggest letdown with the EP IMO is the FOV. It feels more like a Plossl than a widefield and excludes it from being a DSO EP for me. The 60 degree FOV of XF and Radian feel nice and wide enough for very enjoyable DSO observing (10 degrees extra from the XW is a nice bonus but I don't miss it terribly when it's gone). But the Burgess definitely gives a more cramped feeling on DSOs. I suppose it's an individual thing. My threshold for what I call widefield seems to be at around one radian = 57 degrees.

Looking through the EPs at a white wall I compared the FOV with the Antares Elite 15mm (spec 52 degrees) and the Pentax XF. The Burgess seems to be between these two, but a bit closer to the XF, I guess maybe 56 or 57 degrees.

Another thing I noticed (looking at the white wall) is that with Pentaxes and the Elite, the view past the field stop is pitch black. In the Burgess you can see the inside of the barrel somewhat. I suppose that accounts for the extra scatter I saw last night on Jupiter and the Moon.

[janoskiss]

I split discussion about group purchase to new thread:
http://www.iceinspace.com.au/forum/showthread.php?t=12935

[Starkler]

As the new owner of Steves 7mm TMB/Burgess I gave it a bit of a test tonight in my 130mm f5 newt looking at luna through sucker holes in the clouds.

Comparing it to a 7mm circle-T ortho I noticed that the B/TMB is sharp, just as sharp as the ortho given that the seeing isnt exactly flash tonight.
There was a little more scattered light as one would expect considering the extra elements in the B/TMB.
As a secondary test, I focused on a streetlight( :mad2: ) in the next street looking for specs of dirt on the lights lens. Its seems to be a good test subject when looking at sharpness and resolution at higher powers. The B/TMB again was every bit as sharp as the ortho :thumbsup:

There is one aspect of this eyepiece that gets a thumbsdown from me.
I find it quite hard to hold the exit pupil while standing and looking into the scope. Eye placement seems to be quite sensitive and adjusting the eyecup up and down I could not find a position that helped much.

Steve mentioned that he thought the fov seemed small and cramped and percieved it to be less than 60 degrees. I didn't think so myself, in fact during my attempts to examine sharpness at the edge of field, I would move my eye to look to the side and immediately suffer blackout at the edge of field :doh:

In this scope, standing up and viewing the moon, I can only see the entire field if looking near the centre of fov.
Hopefully I will learn how to view through this eyepiece properly and find that it works better in my 10 incher.

It goes to show that peoples eyes are different to others and that eyepieces that work for some, might not work for others.

[janoskiss]

Geoff, it sounds to me like you have the eyecup adjusted too high. I found that the eyecup needs to come up less than half way out from the lens, otherwise I'd get the sort of blackout and eyeplacement problems you are describing.

[CoombellKid]

Steve,

I tend to disagree here, or wouldn't quite go that far. I own several of each
of the HD's and XW's and use them both quite regularly they both perform
diferently optical. Firstly the coatings are completely different. The light
transmission of the Ortho I would say is slightly greater, and due the it's
coatings (or lack of) and less optical elements the image appears slightly
overexposed (IMHO) compared with the XW, especially on planetary surface
detail. Which in turn makes on axis sharpness NOT on par with the XW.

I've have using U/O HD's & XW's now for 2+ years

And to hear this statement "HDs are on par with XWs for on-axis performance" :confuse3: very dogdy, I'd say this statement is about 80% correct.


Interesting to note these days the XW seems to be the ep everyone wants
to benchmark ep against.


regards,CS sunny days

Rob

[janoskiss]

Fair enough Rob. It's just that I cannot pick the brightness difference between them and I've given up trying. I don't own any matching focal lengths so that also makes comparison more difficult. (I used to have a 7mm HD and now the 7mm XW but never both at the same time.)

Do I understand correctly you correctly that the XWs are sharper because they are dimmer? Would that mean in practice that HDs do slightly better on faint fuzzies while XWs do better on planets?

Would be curious to get John B's take on how these two very different lines of fine EPs compare. John, if you're reading this, would you care to comment?

[CoombellKid]

A) ummmmm errrrr nope! just better glass/coatings I would say. Being brighter
doesn't really mean better if that extra light isn't bring anything better to
the image, just my opinion.

B) I never use HD's on dso's no matter how faint they are, just XW's and now
Nagler these simply function better in that roll. I use HD's for double stars,
sometimes planets under certain conditions (prolly about 10% of the time)
and primarily in the PST. Which is where I have found they come into
their own. But even then the XW's have a more pleasing image. I just
dont like leaving an XW sitting in the sun for extended periods I guess.

regards,CS sunny days

Rob

[Starkler]

I have just been outside with the 10" and viewing jupiter in average seeing in the twilight.

My perceptions are still the same:

This eyepiece is sharp, no problems there :thumbsup:
Eye placement is tricky, especially if your eye moves to look to the field edge . This is not a public viewing eyepiece and takes some getting used to.:sadeyes:
field appears to be sharp edge to edge at f5 . More testing needed to confirm.
Its not a premium top shelf offering , but its not far behind it and is EXCELLENT value for money :thumbsup:



I would really love to do a side by side with a televue radian as this ep strikes me as being the poor mans radian and would be the closest competitor.
This range is currently top selling in the US and its easy to see why.

[davidpretorius]

thanks geoff

[janoskiss]

From memory, my impression of the Radian 5mm was better. It has less scattered light than the Burgess (virtually none of that sort of scatter...), a full 60-degree FOV, and more generous eye relief: very comfy. Feels like a premium EP too. The Burgess is a bit rough around the edges, esp with the twist-up eyegard action. Burgess maybe has less false colour off-axis. Given the choice I would opt for the Radian but next to the Burgess the TV offering certainly looks way overpriced.

I did not notice the eye placement issue with either EP but settled in quicker with the Radian. Geoff, I experienced the sort of thing you are describing with the 17mm T4.

[janoskiss]

I should add that if anyone is looking for a similar EP near the 12mm or 8.5mm mark the Pentax XFs are absolutely brilliant! 60-degree FOV and 18mm eye relief. They are priced between Burgess and Radians and worth every cent and then some. My 8.5mm performs as good as the 7 and 10mm XWs, right down to f/4. I have not tried the 12mm but I hope to be getting one soon.

[Starkler]

I gave the 7mm a bit of workout tonight at my favourite semi dark sky haunt.
My intention for this eyepiece was for high power dso viewing and it performs quite well for this. 47Tuc was awesome, as was the closeup view of the ring nebula.
With the uhc filter viewing the saturn neb I could see the faint whispy wings in averted vision which gives it its name.

Regarding edge correction, I detected a small amount of star bloat (field curvature?) away from centre (f5 scope). Its certainly much less than I get from the 14mm XL so its not a deal killer for me. I didnt detect any astigmatism (seagulling).

Now for the bad bit. If you use Baader or Celestron filters you might strike a bit of trouble. THe Baader OIII filter doesnt have a very long threaded section and it seems that the TMB/Burgess might have a taper to the thread start at the end of the barrel.
The upshot is that i couldnt get the OIII filter to hang on which for me was something of a dissapointment. However my Lumicon UHC with its longer threaded section hung on fine.

[janoskiss]

Geoff, maybe buy a cheap 1.25" colour filter, remove the glass/plastic and use as an adapter for your OIII.

[davidpretorius]

thanks geoff