John

Can any doublet be a "full apo" ? Thats the subject of many long threads on another forum I can think of !

There have been a few newtonians where the secondary mirror was positioned away from the optical axis of the primary mirror, on the side of the tube. Off-axis newtonians. No secondary support vanes of course. Here is a review of a DGM 5.5 inch off-axis dob by Ed Ting: Telescope Reviews, Page 7 It impressed the reviewer but there are a number of drawbacks with the design (cost being one of them). Orion (USA) even had one in their catalogue for a while but the design was not popular so it didn't last. I imagine that collimation is an interesting process 🤔

Yes, the packaging was improved substantially by Skywatcher. In the USA the Skywatcher rep on CN also claimed that the objective lens retaining ring was made more substantial which makes sense because that ring (which did seem rather thin) had shifted in the 2nd example that I was sent, allowing the objective elements to get out of alignment. I've never been able to get any confirmation on whether a similar change was implemented on scopes destined for the UK / EU. Despite my 2 unfortunate experiences I always felt that the ED150 had a lot of potential and from reading reports since from those who now own and use them, that optimism seems to have been borne out 🙂

We saw a Space-X launch from Kennedy Space Centre back in 2017. We were positioned a couple of miles away from the pad and had a good view. The whole thing seemed quite calm and uneventful really. The rocket just moved smoothly upwards from the pad eventually disappearing into the cloud base. The sound took a surprising amount of time to reach us and that crackle (like tearing calico as it has been described !) was very noticeable. A few minutes later we heard a sonic boom as the bottom part of the rocket came back down to earth - it was the first time that the lower section had landed on terra firma I recall and from later footage that was successful. I wish I had seen a shuttle go up but maybe I'll get a chance to see one of the heavy lifters go up one day.

Well, many are not convinced by it and that's fine as well of course. I have owned newtonians with conventional secondary support vanes and been happy with those as well, despite the diffraction spikes. Orion Optics obviously stopped doing the curved ones for a reason and I guess lack of demand was a part of that. There was a US company called Destiny I think - don't know if they are still in business ?: 1800 Destiny On Line Store for Curved Vane Spiders (destinycomp.com) Another approach is to use an optical glass window to support a minimal size secondary, rather like the meniscus that the maksutov-newtonian design uses. Now those things really do perform well on the planets, double stars and other high-res targets 🙂

I'm glad that you have shared some experience with the Pentax Dave. Thats a zoom that I have not had the pleasure of trying out 🙂

My OO 12" F/5.3 had these secondary vanes: I didn't see diffraction spikes with this scope. The diffraction was still there but spread evenly across the image and, to my eye, did not degrade it. The CO in this case was 21% the diameter of the aperture. Personally I was very happy with this arrangement. Orion Optics stopped offering it many years ago though so I guess uptake was low amongst customers. I didn't specify this - the scope had 2 owners before me. The scope showed excellent planetary and lunar details, conditions allowing, and was the first scope that I managed to split Sirius with. Martin Mobberley went for a similar approach with his OO 10 inch F/6.3: At some point in the future I would consider a scope such as the above with OO's top quality mirror in it. I'd try and find one pre-owned though, to avoid having to deal with OO 🙄 Other folks have different opinions of course - I can only relate my experience 🙂

Maybe you should tell us a little more about what you are looking for Mark and what your criteria are ? For example, in terms of portability, an ED150 is not going to be preferrable to a Tak 100 or an ED120 even if it's ultimate performance on a wide range of targets does exceed the smaller aperture scopes. Do you see what I'm getting at ? 🙂

This will be interesting - I have owned a Tak 100 (a DL) for 7 years now and an ED120 for over a decade. I have briefly used a couple of the ED150's (loaned to me) but neither was in good shape optically due to shipping issues (early examples - Skywatcher improved the packaging soon after) so I can't judge those. I'll give some thought to my views on the 100 - 120 comparison, rather than give a knee jerk reaction so I'll post again in due course.

I have seen the Horsehead Nebula visually a couple of times when I had my 12 inch dobsonian. I made this report on SGL the first time I did it - I was rather chuffed 🙂 Barnard 33: The Horsehead Nebula - At last ! - Observing - Deep Sky - Stargazers Lounge

When it's at it's best here I get about 30 minutes to observe it as it passes from behind my neighbours house to hiding behind the branches of a large chestnut tree. When I used to use the dob to get a glimpse it was practically horizontal !

A "wanted" advert in the SGL classifieds and on UK Astro Buy & Sell can throw up some interesting offers. It's worth a try.

Ditto with Antares.

I've not seen Mars as a white disk as far as I'm aware. Even when a long way off and very tiny or when viewed with my ancient Tasco 60mm refractor, the disk has always had a pink / pale orange / pale rust tone. When it's far away making out any surface details, ie: the darker areas can be very challenging. Syrtis Major is the most obvious one but even that can be difficult to spot when the martian disk is very small.

That is a chinese made one IMHO. Probably one of the later Celestron ones. The lens cell design is the give away for me as well as the focuser and smaller diameter tube. It's a pretty decent 4 inch refractor of course, but IMHO, made by Synta in China rather than by Vixen in Japan. Just my opinion of course.

I'm a suspicious so and so and I am wondering that sticker has been applied to a chinese made Celestron 102 F/9.8 ? The focuser (or at least what I can see of it) does not look quite right for a Japan / Vixen made 102 either - it looks like the chinese one that the 102 F/9.8's branded Helios, Skywatcher, Konus, Saxon etc used. Hope I'm wrong of course 😕 If it is a chinese made Celestron 102 the tube rings from the Skywatcher Evostar 102 should fit it. Sorry to spread more confusion

I probably would put something in between the two but I prefer to have more options rather than less. It might not get as much use as the 32 or the 13 though 🙄

I assume that your Celestron C-102 F/9.8 is one of the more recent, chinese made ones ? Back in the 1980's / 1990's Vixen used to make them for Celestron and they were exactly the same as the 102M Vixen's, apart from the gloss black colour scheme.

I've used the 3 that Don lists above. I still have a Baader Hyperion 8-24mm. Their prices vary considerably as do their specifications - between £200 (Baader) and £750 (Leica). Their performance is more or less in line with their pricing. The Baader (IMHO) gets close to good fixed focal length eyepieces in performance but looses out in terms of FoV at the long focal length end. The APM performed pretty much as well as Pentax XW's I felt but, in my scopes, had to be used as a 2 inch eyepiece due to the inwards focuser travel needed in 1.25 inch mode. The Leica is really good optically, a touch better than most fixed focal length eyepieces and is often combined with the Baader VIP barlow to give shorter focal lengths. I find the Baader useful to have in the eyepiece case and it's good for travel and outreach. The APM I had on loan and the Leica I tried for a few months but for some reason I didn't take to it in the long term Others find it essential though. That's my short and sweet summary of those from my contact with them. Others may well have a lot more to say on them 🙂

Visually, it's tough: "....Really, it's like trying to see a little bit of nothing with a little bit of less than nothing resting over it....." Jeremy Perez, 2006 Edit: Unless you are using EAA of course 🙂

I'm sorry that I'm a bit late to this. I had a 40mm Aero ED for a while and thought it a very good eyepiece. Best corrected of the Aero ED's that I've used. I have not compared it with a Vixen LVW 42mm though. Although the exit pupil is rather over-sized in the scope, I was pleasantly surprised how well corrected across the FoV the Aero ED 40mm was when I tried it in my F/5.3 12 inch dobsonian. I would probably want to "try before I buy" in my scopes, especially the faster ones, before jumping ship to the Vixen, just to see that there are some actual benefits. If you decide to move the 40mm Aero ED on, I'd certainly be interested in owning another one 🙂

For all but the larger DSO's it may well be all you need in a 102mm F/7 refractor. A true field of around 1.8 degrees will fit most things in 🙂

Not at all. Probably very sensible. Most of these very tough observing challenges result in a very marginal glimpse of something exceedingly indistinct. You do sometimes wonder why you bother 🙄

I've replied to your PM Paul. For the eyepieces I think what you need is a 36.4mm - 31.7mm push fit adapter, like this:

Personally I find it satisfying to see that thin dark line between the airy disks. I'm not doing "science" though - it's just for fun 😁