Burgess/TMB 3.2mm performance

I would like to hear other folks' results using the new 3.2mm Burgess/TMB planetary series eyepiece.

I finally got a chance to test mine last night in my 6" f/4.5 and I was quite disappointed. It has a lot of off-axis astigmatism. Only about the middle quarter or third of the FOV is what I would call sharp. Keep in mind I was using an f/4.5 scope, which puts extreme demands on eyepieces. But for example none of my Radians (I own three) exhibit this and are sharp all the way to the edge. Yes I know that Radians are more expensive but sharp is sharp.

So I'd like to hear others' experience using this eyepiece in either fast or slow scopes. My expectation is that it works much better at slower focal ratios.

Thanks,
Doug

Hi Doug,
I cannot say that I have seen this, but I will check on Friday night and post the results, like you I just got the 3.2mm and have not used it. Perhaps I did not look well enough? I will check it on my f/4.3.
While I am at it I will look at the 2.5mm as well and see how they compare. Hopefully the 3.2mm is as good as the others that I have.

Last Saturday was the first night with seeing conditions good enough to use the 2.5 on Saturn, and I also checked out the 3.2.

In refractors with a focal length of F7 and F8, we didn't notice any problems with either eyepiece.

Were you using it with a Paracor?

It might be that your scope is "too fast" for the design - but you might also have gotten a dud.

I notice you have some slower scopes - you might set up this scope and a slower one next time and see how it compares from one to the other. That would help isolate the problem.

Well, yesterday I sent an email to where I purchased it to tell them my experience with it and to ask if any bad ones had gotten out. They didn't say one way or the other but they voluntarily decided to send me a new one no questions asked. It's on its way as I type. Which tells me the answer was yes. Hopefully I just got a bad one - sounds like everyone else's experience with them is quite good.

I'll keep y'all posted.

Doug

Doug I have only used the 3.2 one morning on jupiter and the moon in a 80 ed. f7.5. It is very clean and sharp right to the edge. On the Moon it was fantastic no off-axis glare issues at all .Without testing on my main scope 10 f6 I would have to say this is the best of the bunch. It will take further testing to determine.

I also have the 4 5 6 7 9. I have considered the 4 the best previously. but I consider them all very good.
I have not done a direct comparison with the 3.2 to a radian so I can not say.
I have done a direct with the 6 and my eyes prefer the cooler color of the tmb bo. Otherwise I would say they have equal edge performance. Testing was done on a 10 f5.6 and a 12 dba I dont know the f ratio
Joe

I do not have the 3.2 yet. But my impression of the
2.5 and 4 are that the edge performance is best
in refractors (>F7) where the speed is not too fast, and
there is some cancellation of eyepiece and OTA aberrations.
I was less impressed in fast Newts (edge aberrations of the eyepiece added to the OTA
aberrations (e.g. coma at field edge).

I had some old post with images:
http://www.astromart.com/forums/viewpost.asp?forum_post_id=484157

Hi Doug,
Well, seeing was not good enough to support 500x with the 3.2mm. I tried several times, but the stars were just too bloated to get a real feel for the EP. It did seem to show some coma at the edges with the f/4.3, but really it was not a good test.
I will try again soon.

Well, my replacement 3.2mm BO/TMB eyepiece arrived yesterday, and a miracle occurred - it was clear last night! I set up my 13.1" and 6" Newts (both f/4.5) on my driveway to do some serious testing.

I first spent a lot of time on both scopes getting the collimation as good as I could get it. Which was good because it gave both of them ample time to cool down. Steadiness was pretty good - I would say about 7/10.

Essentially, I got the same results with the replacement as I did with the first one. Very noticeable coma (I mis-classified it as astigmatism in my first post) in the outer half of the field. Saturn showed an annoying flare away from the center of the field when the planet was positioned from about halfway from the center and getting worse to the edge. Detail in the planet and rings suffered too. Stars exhibited coma, again first becoming objectionable about halfway to the edge. No amount of refocusing would help.

I compared it against a 5mm Radian by itself, the 5mm with a 2x TeleVue Barlow (effectively 2.5mm), and an 8mm Radian w/Barlow (4mm). In all cases everything was extremely sharp across the entire field (except for maybe the most extreme edge). Saturn's appearance was virtually unchanged as it swept across the field, even at 596x. Same thing with stars.

Apparently this eyepiece cannot handle the fast f/4.5 light cone. I do have a ParaCorr on its way so I'll report what difference that will make. My third scope is an 8-inch f/8, but I did not make the effort to set it up also. Others have said good things about this eyepiece at slow focal ratios plus over 500x in an eight inch I'm not sure would have been valid, so I didn't bother.

Thanks for all your replies and comments.

Doug

I prefer a Siebert Star Splitter to a TMB.