John

Actually a lot of that goes on even with some of the big names. If the design is a good one then the brand name that is on it does not matter too much. For example, these are all the same eyepiece: https://www.rothervalleyoptics.co.uk/ovl-hyperflex-7e1-72mm-215mm-high-performance-zoom-eyepiece-125.html https://www.rothervalleyoptics.co.uk/lunt-ls7-21ze-zoom-eyepiece-72mm-215mm.html https://www.astroshop.eu/eyepieces/orion-7-2mm-21-5mm-1-25-zoom-eyepiece/p,17113 http://www.opticstar.com/Run/Astronomy/Astro-Accessories-Telescopes-Opticstar.asp?p=0_10_5_1_8_330 Big range of prices though !

Tell us about your sky quality: Right now, quality thick clouds and quality drizzle

The focal ratio of the scope does affect how well corrected the outer 50% of field of view of an eyepiece is. Practically all eyepieces are sharp in the central part of their field of view these days.

You can get excellent eyepieces in your price range if you are happy to have a standard 50 degree field of view. The Baader Classic orthoscopic 10mm and 18mm eyepieces, for example, are £49.00 each but rival some of the best deep sky eyepieces available at any price. They just don't have a wide or ultra wide field of view: https://www.firstlightoptics.com/baader-planetarium/baader-classic-ortho-bco-eyepiece.html

The Vixen SLV is very good. If you would like a slightly wider field of view, the William Optics SPL also gets a lot of praise: https://www.firstlightoptics.com/william-optics-eyepieces/william-optics-spl-eyepiece.html

I've been reading a few reports on the ES 24 / 82 and it seems to be the weakest of the ES 82 range. Its not a bad eyepiece by any means but if it was my TSA 120 I'm pretty sure that I would spring for a 22mm T4 Nagler.

I've done sessions at my local primary during their science week. I take along a solar scope and do sessions a class at a time generally on the Sun and the solar system and, if clear, a bit of solar observing. I'm generally there for a morning or an afternoon. I don't charge and nor would I consider doing so. It's very enjoyable

SVBONY re-brand eyepieces so they are probably better known under other brand names. If you link to a particular eyepiece or range then we can give an opinion.

I thought the T5 20 and 26 had been discontinued now ?

I've owned the Nagler T4 22 and the T5 20 - both really nice. The T4 is somewhat larger, a bit heavier and has more eye relief and a larger eye lens. The T5 20 is really compact for a 2 inch eyepiece, a touch sharper (maybe ? - its debatable) than the T4 22 and has 12mm of eye relief and a smaller eye lens. The 26mm T5 has a great reputation as well but I've not owned one. I still have a T5 31mm (holy hand grenade !). The T4's T5's and T6's are all current ranges but slightly differing optical designs. At F/7.5 maybe the ES 24 / 82 would do the trick ?. It will be less expensive than a Tele Vue alternative of course. A little lighter as well I think.

A barlow lens can reduce the field of view of very wide angle eyepieces, ie: those with the widest field stops that the barrel size can accommodate, eg: in the 1.25 inch format a 32mm 52 degrees, 24mm 68 degrees etc. A 1.25 inch eyepiece 25mm with a 60 degree field might be affected as the field stop size is quite large.

Interesting Mike. I have found that when comparing really good optics, you need the best seeing conditions and very challenging targets to separate them in performance terms. And even then the differences are usually very subtle !

I'm sure that is true.

I've not really changed my observing approach. I tend to cycle round the scopes that I own giving each a session. The 12 inch dob has had more use than the others over the past 2 weeks because the skies were dark and the Virgo / Coma galaxy fields were presented well. Alt-azimith mounts without attached technology are my usual preference and I've not changed that either. So no difference other than more clear nights than I would normally hope for during March and April

Sounds very nice Doug Clouds here though

Hi Andrew, Very nice to hear from you and I'm glad you still have some involvement with astronomy. Hope the family is keeping safe and well too. Best regards, John

True - last year we had both a major dust storm on Mars and it was so low it was bouncing along the rooftops here.

In Pisces I think. So not really near the zenith. Better than last years opposition though.

Tracking more challenging with a dob when pointing towards the zenith but it is possible to observe there. M51 is up there currently and I've observed that quite a few times with my 12 inch dob over the past few weeks.

Will Mars actually be anywhere near the zenith this year ? - I thought it would still be pretty low down. As you near the horizon you get both additional disturbance from looking though more atmosphere and also a thing called atmospheric extinction - a dimming effect. The higher up in the sky the better, especially when trying for stuff that is challenging.

Nice sketch Ade. Just a bit too cloudy here to make observing worthwhile unfortunately.

Where does the objective sit within that apparently long dew shield Mike ? Is it at the bottom end or somewhat up it like the DL is ?

Very, very very fine scope I think Mike - many congratulations Takahashi triple layer packaging is the business as well - other brands should take note !

The use of an ED glass element (you only need one element to be ED) in the objective, if done well, corrects much of the CA and that correction is then in the optical system and will benefit optical elements further down the optical chain eg: eyepieces, whether they use ED glass or not. There are circumstances where an eyepiece will add a little CA of it's own eg: at the edges of a very wide field of view or if a non-achromatic eyepiece such as a Huygens is used in a reasonably fast scope. It is the combination of an ED glass with other glass types in the objective of the scope, rather than the ED glass itself which is important. The optical figure, coatings, objective cell, lens spacing all make a difference to the final result as well. The different types of ED glass have different Abbe numbers and refractive indexes which indicate the potential they have, when combined with suitable mating elements (very important that last bit) to produce a corrected image for the eyepiece optics to handle. Some brands now are choosing not to disclose the glass types used saying that their products should be judged by their actual performance. Many quality eyepieces have used ED glass types for many years without promoting the fact. Some brands have chosen to make this a selling point though. This whole topic is the subject of long and sometimes heated discussion on other forums !

Hi Ken, I don't recall that there is any objective tilt adjustment on the ED80. Or the ED100 an ED120 for that matter. When I had ED80's (a while ago) I had to shim the end of the scope tube with insulation tape or similar to impart tilt to the objective / objective cell as needed. The focuser alignment with the optical axis is adjusted in the same way. It is crude I'm afraid. In fairness I found that the ED100 I owned and my current ED120 have not needed any collimation adjustment but for some reason the ED80's (I have had 2 of them) both did