5mm 'Mavis Laven' Eyepiece

[Shorty Barlow]

This 5mm 'Mavis Laven' eyepiece had cost me the princely sum of £13.85 (16.02 USD/15.95 euro) from Amazon. Normally these retail at twice or even four times this amount of money. It makes me wonder how much the manufacturing cost per unit is. Under a tenner I’d wager.



These ‘TMB Planetary II’ eyepieces, under various brand names, are very probably manufactured in the same factory. I’ve heard rumours that it is possibly Jiaxing Zihan Trading Co.,LTD in Zhejiang province, China. As usual the ‘Mavis’ rattled slightly when I unpackaged it. This is relatively normal with these ‘TMB’ clones.



The rattle was easily and quickly remedied by tightening the lens group retaining collar under the rubber eyeguard. A process many aficionados of these eyepieces know well.



I set the ‘grab and go’ modified ST80 on its AZ5 mount up at about fifteen minutes before midnight. I managed about an hour of observing before the sky inevitably clouded over. The seeing was well above average at about Antoniadi I~II I’d estimate. However the transparency was not so good and at least 40% of the sky was cloud. With the ST80 the 5mm ‘TMB’ gave me 80x for a 1mm exit pupil and around three quarters of an arc degree field of view.



I found it identical in performance to my 5mm TS Optics Planetary HR and visually sharp, effectively contrasted, and with well defined colour separation. The housings of the two 5mm eyepieces have slight cosmetic differences. They have different end caps. The TS Optics has a slightly stiffer, but smoother eyeguard rotation. It also has a gloss finish as opposed to the ‘Planetary II’ matte paint. Another difference is that the ‘TMB’ has a flared barrel as opposed to an undercut. I have no idea if their respective lens groups differ.



First up was ε Bootis. The white class A2 main sequence secondary was easily and clearly seen even though it is only a 2.9” separation. I was definitely impressed as it can sometimes take at least 130x in these humid conditions to really see the companion star distinctly. I proceeded to split a lot of doubles including ε1 and ε2 Lyrae. Again, depending on conditions, it can sometimes take around 120x~150x to split both pairs. I could plainly see all four stars at 80x. I found M57 pretty easily and also the other ‘Double Double’ (Struve 2470/74).



Cassiopeia cleared for a while and η Cass (Achird) was separated easily. Its primary yellow main sequence star (very similar to the Sun) is separated from the secondary orange dwarf star by 13.5”. I had to concentrate a bit with splitting ι Cass (Struve 262) but managed it seeing all three components. The secondary component is only around 2.2 arc seconds away from the primary. This impressed me the most as only a couple of nights earlier it took at least 140x with my Altair 60 EDF. I’m not sure if it was the above average seeing or the ST80’s extra 20mm of aperture that helped.



Above: 3.2mm 'Mavis Laven' TMB clone. I think this one cost me all of 25 quid. As with most of them I'd fixed the rattle in the main group when I initially received it.



Once when I was out with my 72ED DS Pro I noticed the Smyth Barrel lens was rattling. The lens group retainer itself was secure but the collar holding it into the barrel was loose. I thought I'd fixed this originally by tightening it with my fingers. Eventually I had to get the pliers out! I was using the eyepiece mainly to split doubles but I got a good 131x on Saturn with it. The Cassini Division and some surface detail were well defined and compared very well with the 4mm Takahashi orthoscopic I was also using.



There is an old adage that you only get what you pay for. This isn't always the case.