badhex

Yes agreed Peter, the fit is what you are buying and most manufacturers don't make claims to the clear aperture, excepting maybe a handful. I guess though there's also perhaps an unspoken expectation that the aperture you are getting is not unnecessarily and significantly stopped down. Obviously we know that a cat or a newt loses some aperture due to central obstructions, but unless they are designed badly that loss of aperture is unavoidable. On the other hand the EP barrel stop lip inside the SW diagonals really only needs to be at most a couple of mm to be functional and minimise aperture loss instead of a pretty significant 5mm meaning 10mm total aperture loss. Although it's not as bad, the inner threaded sleeve on the telescope side also seems completely perplexing - what is it even there for? Once I started to think about the whole thing it just seems pretty unnecessary to have these 'features'. Obviously these are just my musings and I don't have the technical and manufacturing knowledge or rationale behind the decisions, and maybe they are all for very good reasons!

Lovely, thanks for the images too, looks like a nice piece of kit as you say. Good to know that there is max aperture option that doesn't cost €400! RE the William Optics one (if you mean the non-rotolock one), many years ago when I bought the Revelation above, I came to the conclusion that the WO was a branded version of the same thing. It certainly looks pretty much identical. Given the 41mm aperture it would explain the vignetting!

Have you been in contact with Hutech? Might be worth it to see if spares are available.

This is essentially the same as the SW ones then - stopped down by the EP barrel stop. I guess you will always have to lose at least a few mm due to the telescope side which has to be 2" outer diameter by necessity, but 41mm seems like quite a step down.

Interesting @Mr Spock - which Revelation is it? Does it have an EP barrel stop lip on the EP side near where the tube joins the mirror housing? The black one I posted above is also Revelation, but it has the inner sleeve a few mm into the telescope side and EP barrel stop. Would be great if there is an affordable Revelation option which maximises clear aperture!

Ah, yeah I guessed it was an EP barrel stop, hadn't refreshed to see your post. So the Baader still wins at the moment then. I suspect it's perhaps quite difficult mechanically (and in fact pointless if largest field stop is 46.5mm) to go any larger.

I had the same issue on the EP side. I tried to unscrew the housing but didn't want to force it, so I cut a piece a stiff paper in tiny 0.5mm increments until it fit through the bottom lip part, then measured the paper. It looks like the Altair also has the same lip at the bottom on the EP side, I guess maybe the intention is to stop EPs with a long barrel from crashing into the mirror? If so, they could achieve the same with a much narrower lip (at least on the SW ones).

Oh @HollyHound I forgot to tag you, in case you were interested in the aftermath of our conversation the other day 🙂

Hello all, after a brief discussion on the postie thread about the clear aperture of 2" diagonals, specifically the Baader 2" BBHS, I remembered my own two have features which probably reduce the somewhat aperture more than is ideal. I did a bit of digging for measurements on the two I own but was unable to find any answers, so I decided to buy a digital caliper (or pair of calipers, if you like the plurale tantum 🙂) and measure them myself, sadly with somewhat disappointing results. Standard Skywatcher 2" diagonal as supplied with the Evostar and other series Inner threaded sleeve on the telescope side measuring 43.3mm Lip quite far inside on the eyepiece side measuring only 41.5mm GSO / Revelation / Skywatcher Deluxe 2" / other brands Essentially identical to the standard SW one despite cosmetic differences. Threaded sleeve on telescope side 43.3mm Lip on EP side 41.5mm (EDIT: This one is not GSO/Revelation, I was mistaken. It's actually Opticron.) I know that the Baader BBHS 2" diagonal has a 47.5mm clear aperture as this is what started the conversation, and it is listed by Baader. This means there is a 6mm difference between the Baader and these two models, so presumably some vignetting must occur with these two for heavyweight 2" EPs with larger field stops, such as the Panoptic 41mm with a field stop of 46mm (I believe this is the largest FOV possible but happy to be corrected). Perhaps if other people know measurements for other brands/models of 2" diagonals, they could be added to this thread for reference.

Ah sorry, I never said in my original post. Gitzo 5 series, 4 leg sections. Listed as 40kg payload although perhaps half that for astro/high power, and weighs about 2.8kg itself.

More than happy to participate in that thread! Might get us kicked off SGL though, I'm already worried that my ambivalence towards Berlebachs is making me no friends 😂 Re leg angle, in my (limited) experience of CF tripods that ratchet-style leg angle lock seems to be quite common. I have a small travel CF tripod from TS-Optics which is the same.

I promised a photo of my recently purchased Scopetech Mount Zero, and here it is now I have the right tripod to go with it!

Thanks! I spent a lot of time thinking about the right tripod choice and once I'd finally put everything together, it just felt and looked right 🙂

Do you mean the angle of the legs at the top? If so, they are locked from further outward movement only. If you mean the leg lock for the height, it's locked in both directions.

Thanks, I really hope so too! I love the pared-back styling, it looks great, all of the finishing is super high quality - and most importantly it is absolutely solid as a rock. I'm just trying very hard not to think of the cost!

So this happened 😱

Whoops, duplicate

It may already be too late to save me from myself 😱😱😱

Would love to have seen this - clouds though!

Amazing. Now we need to see your current setup!

Certainly from pictures it does look like the Baader has no such sleeves/baffles (I know it's not really a baffle but unsure how else to describe it) and as we know the measurements for the Baader, I guess we can infer that the ones with an internal sleeve like the Revelation will be narrower. I do not have any calipers to measure internal diameters and get real data - maybe I'll pick up a cheapo one and measure it 🙂

Thanks! It certainly seems like with some others (I have both a Revelation and Skywatcher dialectric) there is often an inner sleeve of a couple of mm, or a baffle of sorts, but it seems a bit tricky to track down clear aperture measurements for comparison.

A question on this if I may: Does the Baader 2“ BBHS Mirror Diagonal have a larger light path /internal diameter than other 2“ diagonals?

This is sort of what I do, a two stage approach. Assuming equipment is not damp already, I'll make sure everything is fastened shut so it doesn't instantly dew over, and leave it inside cases for about an hour in the spare room which is a touch cooler than the rest of the house. Once it's had a bit of time to take the edge off the cold, everything comes out of the cases with caps off overnight.

Thanks Lee! Looking forward to the next session 🙂