John

I find that applying magnification reduces the brightness of the moon. I don't use a moon filter even with my 12 inch scope. I do have one though in case anyone else wants to use it when I do outreach sessions. They don't cost much to have in the bottom of the eyepiece case after all.

A bit more magnification is what I find works well at teasing faint DSO's out of my moderately light polluted sky. If I can get that AND have a large true field, well that just seems ideal to me

If you can find a copy of the S&T Pocket Sky Atlas I highly recommend it. I use it all the time during my sessions with my 12 inch dob. I have the more detailed Interstellarium for further reference but the Pocket Sky Atlas is with me as I observe.

I was loaned the ES 2x Tele-extender for a while. It was very impressive for it's price. Practically the same performance as the Tele Vue Powermate but at a somewhat lower price. I've owned and used quite a lot of barlows and tele / focal extenders. The only one I have now is the Baader Q-Turret 2.25x barlow which is pretty good optically though rather plain and simple in build / finish terms.

The 16mm Nirvana would work well at F/5.9 I think. The extreme edges of the field of view might not be 100% perfect but the majority of the field of view will be very nice. They are very good value currently for an 82 degree eyepiece.

Here is a Tasco model that I had not come across before - it is a rebranding of the wonderful Vixen 102mm Fluorite refractor. Not sure how many came out with Tasco branding on them but there were one or two other Tasco scopes that were made by Vixen so at some time the two companies much have had an agreement of some sort.

To be fair, Maxvision branded eyepieces have been well known on here for a few years now and have a great reputation for good performance and excellent value.

I had a choice of 64x, 133x or 200x Stu. Simple Huygenian type - 2 elements in 2 groups ! Mind you, F/13.3 fracs are not too fussy. A cloud free night, a stable mount and a modern eyepiece / diagonal and the results may well be different Edit: my earlier post should have read thin cloud cover rather than tin cloud cover. Doh !

You need good seeing for these to be clear: In broader terms, scopes that have a reasonable degree of under or over correction seem not to be able to support higher magnifications.

I could not do it last night with my old 60mm refractor. I could see it was a double star - a sort of peanut shape. Each end of the "peanut" had a different tint to it. Just no dark line separating the two. The conditions were not great (tin cloud cover) and the scope 50+ years old with the old .965 inch eyepieces used being of the same vintage. It did give me nice splits of Gamma Leonis and Gamma Virginis though.

When I've owned achromats I've not been that bothered by the CA that they produce - its one of the characteristics that you would expect from the design. I've been more bothered by the levels of SA (spherical aberration) that are often possessed by these scopes. IMHO that constrains the performance more than CA levels and can't be filtered out.

Last time I collimated a bird-jones scope I used an artificial star and the view of it at the eyepiece about 30 metres away. That seemed to work quite well when we came to use the scope under the real stars.

I go by what has worked best for me under my skies over the years I've been observing. My 21mm Ethos gets a lot more use in my F/5.3 12 inch dob than my 31mm Nagler does. Whether that matches the theory I really don't know

I find this table useful. From my experience with achromats I would say that it is borne out in the real world:

Don Pensack's Eyepiece Buyers Guide may be useful: https://www.cloudynights.com/topic/700069-2020-eyepieces-buyers-guide/?p=10080606

People have been moaning about stock focusers for practically all brands for the 15 years that I have been on this forum. Moonlite, Feathertouch and Baader have done very well supplying replacements Even Astro Physics focusers are often replaced. Happy to say that my TMB/LZOS refractor came with a Feathertouch as standard though

He has already done it:

The optical tube assembly (OTA) dates from 2006. Originally it was used on a huge equatorial mount by and imager. I bought it used about 5-6 years ago (I think ???). An SGL friend made the dobsonian mount along the same lines as the Orion Optics mounts but using Baltic plywood. If the mirror does not need washing, I don't touch it. You can have quite a bit of dirt / debris on the mirror without it affecting the image. The reflectivity of mirror coatings does gradually reduce over time. I have seen a % figure somewhere but I can't recall what it is

5mm orthos do have very small eye lenses. The Supermonos are even smaller !. Great performers but very challenging to find the exit pupil in the dark.

Quite possibly Stu. My DL is the only Tak that I have ever used so that is all I have to go on

Skywatcher 1.25 inch eyepiece adapters are not usually threaded for filters, unfortunately.

My Orion Optics 12 inch dobs mirror was re-coated by Orion Optics in 2010. The coatings still look very bright. I wash the mirror about once per year. Storage can be an issue if you have lots of scopes. I have 6 currently in my dining room including the 12 inch dobsonian. Luckily we don't entertain much ...

Thanks Alan

Yep - that does look excellent. Good mirror as well if that strehl figure is accurate.

Well done Neil - good spot and an interesting report I have often read that good quality orthos are favourite for observing faint objects with big scopes under dark skies. The Baader Classic 10mm and 18mm are really good for this. I felt the 18mm was even a touch better than the Baader GO 18mm in terms of faint DSO spotting when I compared them a few years back. Tele Vue plossls are pretty good as well - their light throughput is as good as anything else out there. The Delos eyepieces get very close to the ortho performance in this respect as well.