Burgess 24mm Modified Erfle & 10mm Ultra Mono

[BillP]

Have been assessing these two relatively new eyepieces for the past few months.  Attached is article I put together with my impressions.

Burgess 24 Modified Erfle and 10mm UltraMono.pdf

[John]

Thanks Bill. Interesting read. It's been a while since I've seen something new with the Burgess name on it. Their original planetary eyepieces were pretty good I seem to recall.

I had the TMB 5mm Supermono for a while and that was probably the finest planetary eyepiece that I've used in terms of pure optical performance. The ergonomics of short eye relief, tiny eye lens and ~30 degree AFoV made it a challenging eyepiece to use - I had to be in the right mood for it !

Interesting to see another manufacturer trying the monocentric design.

 

[Ruud]

Wonderful, Bill, we always enjoy your reviews!

The word DRAFT is printed across every page. Is that intentional?

I'm going to read it anyway  ?

[BillP]

I am so sorry!  Uploaded an older version.  Just corrected it.  If anyone already downloaded please delete that and get the new version now attached at the top of this thread.

[Ruud]

Thanks, I'm downloading again.

[BillP]

FYI, I just updated the article in the 1st post yet again.  Sorry for the inconvenience.  I carried out one more test and the results were quite interesting so I decided it was worth adding.  Basically the new version has the addition below.  I changed the version date in the updated article to October 12, 2018 so it is not confused with the earlier version.

Finally, the rectilinear distortion in the Modified Erfle is extremely low.  When placed in a daytime spotter scope straight lines in the off-axis, even right up to the field stop, stayed straight.  I then wondered how the true field of view (TFOV) might differ in this eyepiece compared to something like an Explore Scientific 24mm 68° or a Tele Vue 24mm Panoptic, both of which have a significant amount of rectilinear distortion.  Having an Explore Scientific 24mm 68° on hand I compared it to the Burgess 24mm Modified Erfle and discovered that the TFOV of both the 61° Modified Erfle and the 68° Explore Scientific were almost exactly identical!  So although the Modified Erfle visually shows a smaller AFOV, its TFOV is almost exactly the same as the wider Explore Scientific 68° with its added rectilinear distortion to maintain more controlled off-axis star points.

[Orac]

Good review BillP (again).

How would you rate the 10mm money wise? Is it worth the price? As far I am aware this is only the second manufacturer which sells a mono. 

[BillP]

If you are a planetary enthusiast, have a fairly refined and critically maintained optical train (scope and diagonal), use more comfortable focal ratios (not f/5 and faster), and use it with a Barlow to increased the FOV that is sharp.  Yes, a lot of conditions.  But this holds true for monocentrics in general.  They are a specialized eyepiece for specialized circumstances.  I'm now retired and on a fixed income so $100 purchase I need to sit and think about.  For me though worth it as I really need something good in the 4mm range (using with my 2.5x Powermate) to tease out planetary details from my smaller bore scopes.  This eyepiece did all that quite well so am adding it to my stall and finally putting to rest my 4mm search (which has been many years).

IMO the "planetary" eyepiece is very specialized and not something everyone should quest after.  Many wide fields put up excellent views of planets, like the Morpheus or the DeLites.  I would not use planetary niche eyepieces in my Dob either because fast focal ratio they generally do not handle well and I do not clean my mirrors but once a year so dust build up on mirror adds enough scatter that overwhelms any advantage from the planetary eyepiece can add.  But my 81mm, 102mm, and 152 Apos I keep in top operating condition and given their smaller bore for planets every ounce of extra contrast is a welcomed thing for planetary, particularly Jupiter and Mars.  So if the circumstances match then worth getting a planetary niche eyepiece, and $100 is sure a lot less than $600 for a ZAO or $300 for an XO, especially when the on-axis results are competitive.

[Orac]

Thank you for the extra explanation and context. I never realised that a monocentric was such an specialised  eyepiece. I have several Orthoscopics for planetary and I think they will serve me fine for years to come. 

[AndyH]

Thanks for another detailed review, Bill. Most appreciated

I noticed months ago, the Burgess website mentioned the soon arrival of this new Ultra Mono and am delighted that you've shared the 'eye hours' you've had with it.

 

Cheers, Andy