Explore Scientific - 4.7mm or 6.7mm

[Orange Haze]

Last night was my first night out in 18 months. Some nice moon views and M42, but otherwise a moonshine and cloud washout. But now I am active again I am keen to add to my eyepiece set. 

I bought the Explore Scientific 28mm Maxvision a few years back and have been supremely impressed by it. As such I am happy to stick with ES but wanted more quality at the lower end. I am tempted by the 4.7mm (82 degree) as I love planetary viewing, but am concerned that my use of it will be limited as I am pushing the magnification a little too far. The 6.7mm may therefore be a safer option and get more use. I've so far found my 6mm BST to be rather substandard.

Has anyone got experience of these eyepieces and much use of the 4.7mm in particular?

Thanks All!

[Victor Boesen]

I have the same dob as you and the 4,7mm 82 degree, and I can rarely use it on planets because of the conditions, so I would go for the 6,7. However it is still a great eyepiece when the conditions allow it to be used.

[rwilkey]

Hi Orange Haze, I have used them both and my advice is also to go for the safe option of 6.7mm.  I find the 4.7mm does not get used very often but is particularly suited to lunar viewing rather than planets.  Both have fairly tight eye relief but great clear views when conditions allow.  My best planetary ep though is the William Optics SPL 6mm, not found anything to improve on that.  Good luck with your choices, I am sure you will not be disappointed. 

[David Smith]

I would third that. I have the ES6.7 and a TMB PII 4mm with my Revelation 10. Rarely use the 4mm especially with Jupiter and Saturn so low at the moment.

[Ruud]

Hi Lee,

250x from the  4.7 mm is a bit high. 175x from the 6.7 mm might be a bit low.

Fortunately there is also the 5.5 Meade series 5K ultrawide. That gets a really good press and would give you 214x. 

[laowhoo]

I remember the 14mm being the only weak link in the series. We have their 24mm68*/8.8mm82*/and 4.7mm82* and we Barlow 1.5x for our 12.5" f/6. We haven't been able to use the 4.7mm yet. It's waiting for great conditions, as is our 36mm. Here's a decent review

https://www.cloudynights.com/topic/509496-review-explore-scientific-82-degree-eyepieces/

We got the 4.7mm to fill out our range. Some day.

[Orange Haze]

Thanks all for your responses, really appreciate it. I think I will go for the 6.7mm and if the viewing is exceptional I can always add the Talx2, although that would be extremely rare! Am hoping to take a trip to the Brecon Beacons in April so if I am lucky, I can put it through its paces up there....

 

[Louis D]

I rarely view planets like Jupiter above 125x just because contrast tends to fall off rapidly above that for me (except in my 15" Dob, but that's another story).  However, I regularly view globular clusters at over 200x using my 5.2mm Pentax XL in my 8" Dob.  It's the difference between high contrast and low contrast targets.

[Ben the Ignorant]

I don't know about the 6.7 but the 4.7 increases chromatism in achromats and semi-apos. It's super-sharp (might show more microdetails than the TS 4mm sometimes) and excellent in all respects except for that surprising ability to make chromatic fringes subtly brighter and broader.

Doesn't make any difference in my 80mm triplet because it has no chromatism at all, but the 80mm achromat and the 80mm semi-apo are affected. The effect is really not dramatic but it's one more small factor to know to make a choice.

[Charic]

The 4.7mm would suitably match the 250mm f/4.7 scope giving 250x mag, but how often you would use this under UK skies, is something  only you can decide.

[Charic]

3 hours ago, Ruud said:

250x from the  4.7 mm is a bit high.

I would have thought that a 250mm scope should be able to easily provide 250x if the seeing is good.

[Louis D]

1 hour ago, Charic said:

I would have thought that a 250mm scope should be able to easily provide 250x if the seeing is good.

It depends on the seeing, quality of the mirror's figure, accuracy of collimation, and object choice.  For instance, the moon would certainly be a good target at 250x due to its high contrast, but Jupiter would probably be a poor choice due to its low contrast unless everything is spot-on perfect that night.

[Orange Haze]

I did once manage to resolve Mars quite well at 240x, but only briefly and the night in question was absolutely ideal seeing. Maybe with a better eyepiece it could have been clearer, but that kind of night is pretty rare and I've come to conclusion that I am better off seeing at 180x more often than 250x rarely. The feedback on this site is always superb and as an amateur I really value the advice..... thanks!

[JG777]

I have the 6.7mm and it's a very good EP but it needs good seeing conditions to really excel. A better choice than 4.7 but sometimes I wished I had nabbed the 8mm instead.