John

I'd advise trying them before buying if you can. I've tried a few pairs of binoviewers out over the years with different scopes and have a set of the William Optics ones on loan from FLO at the moment but I just don't get on with the things. I can see a merged image OK the the views look nice enough but for some reason I prefer viewing through a single eyepiece I know that for others these devices are really enjoyable so I think personal preference plays a big part in this.

An H-Beta filter doesn't provide amplification though - it just removes the wavelengths that are less relevent. As I understand it, NV is sensitive to a broader range of wavelengths than the unaided eye ? I believe that the impact that NV can have is (easily) similar to doubling the aperture of a scope. No simple glass filter can achieve that, as far as I know.

Is the Questar much better, in terms of the views, than, say, a Meade 90mm mak though ? I'm sure I read a very experienced user here had compared the views between the two and found very little difference. I'm sure the build and overall quality of the Questar are superb though.

But NV is EAA isn't it ? It involves electricity, provides an assist and, here, is used for astronomy. It seems to me to be like racing push bikes vs powered bikes - both go around a track but the powered ones will have much faster lap times so the two forms can't be directly compared in terms of results. Both are enjoyable though

Thanks to this thread and the reports / charts posted I've been able to spot PG 1634+706 with my 12 dob tonight. Thanks very much folks It's very, very faint indeed. I've found around 400x magnification and a combination of slightly averted vision and the "1000 yard stare" has helped this dim point of light show against the background sky. 8.6 billion light years - wow !!! Those photons have been travelling for nearly 2/3rds of the age of the universe .....

Using high or very high power definitely helps to tease out faint point sources.

Of the scopes that I have got, I guess the ED120 refractor is a pretty good "all rounder". 3 true degrees with the 40mm Aero ED eyepiece and up to 300x when target / conditions allow at the other end. The showpiece DSO's look nice under dark skies with the aperture as well.

I've used a 30mm XW (long ago) and thought it very nice but I slightly preferred the Nagler 31 too. I've passed on the 14mm and 20mm XW's in favour of the Delos equivilents mainly because of reports of noticable field curvature in the XW's. Maybe this is overblown though ? - I've not actually tried the 14 and 20 XW's myself to be fair to them.

I agree with this. I could see Saturns rings quite clearly when I used to use a 60mm refractor which was about as powerful as your 76mm newtonian. Saturn will look small in the eyepiece but you should be able to see it's rings unmistakably. It should look a bit like this:

Wow - a 5 year old thread ! I have the 3.5mm Pentax XW but I have not owned or used a Delos 3.5mm. All the reports I've read indicate that the two are likely to be very, very similar in performance so I guess the choice would be over the ergonomics (which are also similar) and the price - bought new the XW 3.5mm costs around £60 less than the Delos. I did compare my XW 3.5mm with an Ethos SX 3.7mm over a few months and concluded that, despite the massive field of view of the Ethos, the XW was a touch sharper so I eventually let the Ethos SX go to a new home. I have the XW's in 10, 7, and 5mm focal lengths so it makes sense to have the 3.5mm as well for high power observing. I have the Delos in 17.3 and 14mm focal lengths and like those a lot. The shorter focal length Delos's have a different focal point than the longer two which might be a little inconvenient if mixed with my XW's which reach focus close to where the 17.3 and 14mm Delos do.

I know that David Hinds was a good mirror maker but I did not realise that he also did refractor objectives ?

Lovely setup Gavin Meanwhile, back with something that will fit happily on an AZ-4 - My Vixen ED102SS doing a little white light solar today. My reward was just one teeny, weeny sunspot. Nice afternoon to be out anyway

I think the 28 inch might still be at Greenwich Chris ?: https://collections.rmg.co.uk/collections/objects/11094.html I visited the site around 20 years ago and it was certainly there and in use - I have the photos somewhere to prove it ! Maybe it's mothballed currently ?

I tend to agree Ian. I find my 21mm Ethos (exit pupil with my 12 inch dob is 3.96mm) to be a noticeably more effecitve galaxy / faint target tool than my 31mm Nagler with it's 5.85mm exit pupil with the same scope. If I observed from a really dark site, the Nagler 31 might get more use ?

That looks great My only question is, if they can double box that one, why not the 1st one ?

You don't see many reports on the ES 25mm / 100. Good to know that there are some out there

Just as an additional note, I also have the 30mm Aero ED, bought for outreach, and thats decent but not as well corrected as the 40mm.

I have the Nagler 31 and the Ethos 21 and love them both. The N31 shows a bit more sky of course. Recently I acquired an Aero ED 40mm (actually a clone of it) which provides a 68 degree AFoV and has surprised me by being really sharp and pretty flat across it's field even with my F/5.3 12 inch dobsonian. The 40mm / 68 shows a wee bit more sky than the Nagler 31 and is much lighter - nearly half the weight. The optics in the Aero ED's (and clones) are reputed to be the same used in the now out of production TMB Paragons. At F/8 I would think these 40mm / 68's are worthy of consideration as alternatives to the 41mm Panoptic. The field stop is sharply defined as well !

There is still the Wall 30 inch refractor (pictured below) at the Hanwell Observatory I think. They have a 30 inch reflector there as well, for public outreach:

The longer stalk on the 30mm affects it's positioning as well - it stands a little higher off the scope tube.

I use 6x30 RACI finders on my 100mm and 120mm refractors and a 9x50 RACI on my 12 inch dobsonian. Here is a quick pic of both sizes which might help:

Once the pinion shaft is bent, even slightly, neither a crayford or a rack and pinion will work nicely.

I think these chinese crayford focusers are very sensitive things. When they leave the factory they are well adjusted and work nicely. If you dare to adjust them yourself though, or if they get a bash, they are never quite the same again. Don't know why it is but thats what I've found

There are a number of terms used in some older books that deserve to be questioned, for example "useful planetary work". Perhaps today you need a launch vehicle, a robotic spacecraft, a team of engineers and scientists and a few million $'s to do useful planetary work ?

Thanks Jeremy - I'm flattered