great_bear

Just by checking out astrobuysell UK twice a day, and immediately expressing interest the moment something comes up. Sellers might be slow at updating to ‘sold’ or often don’t seem to bother doing so at all, so it’s quite common to think something is available but discover it was already sold the day before - it can be frustrating. I think at least one on the list came from here on Stargazers Lounge.

I started collecting these a few years back after noticing that Bill Paulini liked them. It didn’t take long to build up a full set: I didn’t get the 40mm as it does not appeal to me.

When I look at this assembly video for the Vixen, the centre section doesn’t fill me with confidence. It doesn’t look designed to withstand the twisting/flapping that a long-length scope might place upon it.

Indeed - I probably should explain that to my kids, who I think left Selfridges a bit depressed and thinking they’d never be able to afford any nice things in life. https://www.astroshop.eu/instruments/fujinon-binoculars-lb-25x150-mt-sx/p,23647 (although note that the above doesn’t include the mount and tripod, which Selfridges does in their price)

Ah OK - I was referring to balancing between lightest and heaviest loads. But I do see how you’ve reached the absolute limit. Looking at mine there’s only about 15mm of adjustment left, which wouldn’t allow much more than the load I’ve got. Easy to fix by counterbalancing but it is indeed surprising that they didn’t provide for a at least a bit more travel on that adjuster.

Unfortunately a little out of my price range for my Christmas present:

Do you mean that you’ve reached the end of travel for the adjustment? - or that the difference between your lightest and heaviest loads is too great?

Anyone used that Vixen at all?

Oh, one other thing for those who decide to use magnets, if you don’t want to stick anything on the scope, you could wrap a magnet in sticky-backed foam, as I did with this one I use on my 150PL (note also the thick red rubber-band as a handgrip) This is the size of a large bar of soap, and I have used it for many years now:

Yes, I have the Telescope House one, under their Revelation brand. I found that when the correct balance position and tension is dialled in, no magnets are required for balancing, regardless of what eyepiece is used (note that Delos are the heaviest that I use). I did upgrade to the (now standard) RACI finder but went back to the straight-through finder. I operate this scope sat next to it and in this position straight-through is much more intuitive to use and doesn’t seem to cause me any neck strain. The only extra thing I bought was a (very expensive) shoulder bag (Orion USA) for the OTA. I agree a handle would be a better (and cheaper!) option, although I suspect the shoulder bag could help avoid condensation when bringing into the house but proving that, would be a Schrödinger’s Cat exercise 🙂 I bought the scope for use at the Baker Street Irregular Astronomers’ meetings because I discovered only Dobs can withstand the breeze at The Hub in Regent’s Park and give rock-steady views. Experienced and new stargazers alike never fail to be taken aback at how startlingly good the views are through this scope - it has a fine mirror.

Does anyone have thoughts on the relative merits of these three mounts (it will be for a 150PL scope): Berlebach Castor II Sky-Watcher SkyTee 2 Vixen Advanced Polaris Altazimuth APZ Which is best? (it will sit on a Berlebach Planet) - Is there much difference in smoothness/stability? - Do any fall into the “avoid” category? My 150PL is a heavy scope (maybe 7Kg) so minor differences in smoothness will probably make little difference. (I am currently using a Sky-Watcher AZ4 head and it has too much backlash and wobble with this long, heavy scope) Happy to hear alternative suggestions too.

Mirror now moved - hoping this doesn’t cause a problem reaching focus in the opposite direction 🙂 Looks like it’ll be a couple of nights before it’s clear enough outside for me to try…

The downside is it’s pricey, and that the design necessitates an Allen key rather than a thumbscrew to secure the eyepiece (great suggestion nonetheless!): (probably worth noting that it’s only parfocal when used with a paracorr, but is nonetheless still useful for reaching focus with eyepieces like the 17.3mm and 14mm Delos which some scopes can struggle with)

Unfortunately not - it’s that pesky non-parfocal 17.3mm Delos and the extra infocus that it requires! In light of the comment from @AstroKeith I guess I’ll just move the primary forward instead; it’s easy enough to do.

D’Oh! Of course! That makes sense now - thank-you.

The new mirror in my scope seems to have a slightly different focal length than the previous one. This means I need to get a 25mm extension tube for the 2" focusser. 35mm seems common, as does 50mm - but I need a 25mm one. Anyone know where I can get one?

The argument goes, at that particular exit pupil, why not just haul out a smaller telescope If that’s the only eyepiece you’ll be using for the night, that’s a perfectly good argument for choosing a smaller, lighter scope to take that evening. Similarly it’s a reasonable argument to say that I’ve “wasted money” on this eyepiece (for my 8” Dob) when I can get an almost identical view in my wife’s 130P with the Meade 24mm SWA that I already have. I do think that unnecessary cost is something that owners of multiple scopes should consider at low magnifications. In my case, I felt the hassle of setting up a second scope was worth eliminating by purchasing this relatively inexpensive eyepiece (in practice the central obstruction issue is easily avoided by off-centre eye-placement) In the case of refractors however, it’s important to point out that there is precisely nothing to be gained by changing scopes - the view is identical in both cases - that’s why “wasted light” as a concept is a nonsense idea - there are no optical efficiencies to be gained.

I know - it isn’t wasted light - that’s the myth (albeit a common one). It’s not “wasted” any more than the sunlight on the ground when you go out for a walk during the day. That’s because there is no optical configuration for that magnification that could “squeeze” that light into your eyeball. Your eye is already fully illuminated - no waste.

No such thing as “wasted light” - at least not as far as refractors are concerned. It just means that you’ve reached the maximum light-gathering capability that’s physically possible (with any scope) for that specific power of magnification (and perhaps could achieve that same view with a smaller scope - not that there’d be any benefit in doing so, unless you’re planning on spending the entire evening in that view). On the aberration front yes, the outer edge of the eye’s lens will - for some people - be not-so-good in terms of focusing the light bundle, so it’s entirely possible that optical quality might drop off for some individuals when you reach that point.

I think the key point is that ED is not a 'better' kind of glass - it's just glass with a different refractive index. The balancing of glasses of different indexes is a key tool to make sure the different wavelengths of light converge as closely as possible. There may be other emerging techniques in the optical designers toolbox that Sky-Watcher and others might not necessarily want to divulge. The main thing the customer cares about is the performance of the scope overall. Agreeing on industry-standard, unambiguous ways of measuring, reporting and comparing scope performance is probably the thing to focus on (no pun intended).

Interesting. I have next to me the chunk of sponge that I used to paint the Mak tube. Although the sponge is very stiff, I can squash it around and the dried paint shows no signs of shedding, which is good, and the paint hasn’t changed the visible appearance of the sponge (other than making it very black!). In a way, it’s behaving almost like ink, which is why I can see that painting the flocking paper might - under the right conditions - be beneficial. I’m just a bit worried about flattening the fibres in a way that spoils the flocking. I guess I could take two small test samples of flocking side-by-side, paint one of them and then test the result.

I’ve got the older, gold-tube version which out-of-the-box only handles 1.25” eyepieces. I upgraded the diagonal to a Revelation 1/20th Wave 2” one but only for the rigidity and optical improvement (which was significant). So in my case, I’m not worried about 2” EPs because I never expect them to work anyway (although I do have a GSO Superview 30mm, which works well with no significant vignetting).

You’ll only need to paint the area directly opposite the focuser and just the small length of the tube base that is visible from its reflection in the secondary mirror.

I have recently painted the inside of the baffle tube for my Mak 180 Pro with the paint mentioned in the original post. I was pleased at the very neat job that I did, but to be honest it has made absolutely no difference (thankfully it didn’t make it worse!). So it seems that at the very oblique angles that light strikes a Mak baffle tube, this paint offers no benefit. So don’t bother doing this on a Mak. I may have an attempt at flocking instead at some point in the future - there is just about enough room in the Mak 180 if the flocking material isn’t too thick and will stay stuck down.

But I note with interest it’s normally stated by people with vast eyepiece collections! 🙂 If you quiz those wise only sages that say “you only need three powers - high, medium and low” it unravels pretty quickly: What do you use for your low-power eyepiece? “Oh… Well… I split that across two eyepieces actually” What do you use for high-power? “I have just one high-power eyepiece… Plus a special extra-high-power one for truly exceptional nights, but that’s not really in the collection” - and medium-power? “I only use my 12.5mm wide field… Although I do have a 12.5mm ortho on standby if I need to pick out fine details… - and a 9mm one…” - and so on 😁