JTEC

11mm TV Plossl is an excellent eyepiece, as is the 8mm, if you’re not bothered about eye relief. Observing Mars and Saturn with a 140mm apo and Baader MkV binoviewer from 8,000ft an experienced observing friend and I tested pairs of 11mm TV Plossls against 10mm Tak LEs and 9mm Tak orthos - OK some mag difference to be sure - and both of us gave the nod to the Plossls. Make of that what you will 🙂

I’m with Olly on this. The terminology is loose. Nothing is being ‘cropped’. The system projects an image of given size onto the sensor. Keeping the optics the same and assuming adequate coverage, if you switch to a bigger sensor, the optics will illuminate it and you’ll capture a wider image. If you change the sensor for a smaller one, it’ll only be big enough to receive part of that wider illuminated field and, by comparison with the wide image, it’ll appear ‘cropped’. But ‘cropped’ from what? You’ve just used a smaller sensor that allows a smaller field to be captured for the same focal length. I think the crop factor terminology originated, as I think Louis and others have said, when from a base of 35mm camera lens technology we had to get used to smaller sensors being used and it became convenient to pretend that a 50mm lens behaved , in effect, like a longer one - again, it didn’t, it continued to be a 50mm lens but it was now projecting onto a smaller sensor so that a smaller field was recorded - similar to the effect of using a longer lens on the baseline 35mm format that we had been used to working with. But in astro-imaging with its plethora of focal lengths and sensor sizes, not to mention the complicating effects of flatteners, reducers, etc, there is no such traditional baseline and it makes no sense to say that an image has been ‘cropped’ as if something has been actively done to chop its dimensions relative to some imaginary standard. We’re dealing with individual outcomes specific to a given system, so perhaps more use, I would argue, to describe this in terms of focal length and sensor size used.

I think that’s right. I’m clear that the Baader Zeiss prisms give me the better results with my TEC140 - which is a very ‘decent apo’ - than the AP dielectric did. Less scatter, purer and brighter. That goes for mono and bino viewing. If I plugged them into my dusty old, uncollimated Newtonian perhaps these differences might not be apparent. There is something subjective about this though that isn’t easy to characterise. Can you ‘see more’ with the prism than a quality mirror? Perhaps not, unless scatter is an issue. Is the observing experience a little bit different? In my opinion, yes. But however hard I try to be objective about this, I’d have to agree that in the end it might boil down to preference and taste.

Don’t know about that , John ... 🙂. I do like the prisms though. I read somewhere that they’re back coated with the BBHS silver. Not sure whether that’s true. When I bought my TEC more than 10 years ago I went for what I thought at the time would be the best diagonal, the 2” AP. It was good, of course but I think the prisms give a more scatter free, brighter image. So much of visual astronomy is down to taste and impression though, so I wouldn’t want to claim any more than that.

I’ve seen Triton with a friend’s 8inch SCT. It wasn’t firmly held but definitely detected. I remember saying ‘Hey, I can see something else, I wonder if it’sTriton?’ On checking charts the glimpsed object and its position relative to the primary were confirmed. Checking magnitude , this would have been close to the limits of the scope. Can’t recall the magnification or eyepiece used.

I use the Baader Zeiss spec prisms for mono and bino viewing with the TEC 140. To my eye they clearly outperform the AstroPhysics dielectric that I used previously - and the AP is supposed to be as good as it gets in terms of a mirror/dielectric. There’s less scatter and better contrast and image brightness - I sold the AstroPhysics.

Is this it? https://www.kyoei-osaka.jp/SHOP/docter-uwa125.html.

I have the 8 and 10mm Delos which I use with my 140mm f7 refractor and find them excellent: sharp, comfortable, contrasty, great tone and rendition of star colours, throughput reportedly a little bit better than comparable Ethos. I still might be tempted by the Ethos if money were no object but Alvin Huey reports that he replaced his Ethos eps with Deloses because they went deeper! I can honestly think of nothing to criticise about the Deloses I own - even in those moments of restlessness we get that lead us to dream and speculate about eyepiece pastures new. And I always conclude that I can’t think of anything that would be better.

I agree with Roger’s view. I’ve used both though not in alongside comparison. I kept the Tak and sold the Delite. You might also like to consider the Vixen HR. I have both the 4mm TOE and the 3.4mm Vixen HR. I think both are fantastic. In so far as it’s possible to allow for the difference in focal length, if I was pushed to choose one it would be the Vixen. Less pricey as well.

+1 for the ES filters in terms of value for money. Having tried most, including the Lumicons, etc, the DGM NPB filter is now my preferred UHC-type filter - and they’re not massively expensive at least in the 1.25 size. I’ve also tried the Televue (by Astronomik) OIII and thought it was the best OIII I’d ever used, again, including the Lumicons. Admittedly, personal preference and other system characteristics can play a part in this.

It may be worth pointing out, to add to the above, that not all Televue eyepieces are expensive. The Televue Plössls, for example, are relatively inexpensive but, if you don’t mind the modest eye relief and fairly narrow field of view (and I don’t) they are very sharp indeed. I had a best ever view of Mars in 2016 with a pair of of 11mm TV Plössls in the binoviewer. The other contenders at the time were Tak LEs (slightly more complex design) that cost at least twice as much. Not all eyepiece designs are as expensive to produce as, say, an Ethos and perhaps that’s worth bearing in mind. I don’t use a lot of wide field eyepieces, but among the narrower field offerings there are one or two ranges I’ve come across that punch well above their weight in relation to cost - these are the Sterling Plössls that used to be sold by Smart astronomy and I think are made by Long Perng. Then there are the Edmund RKEs which seem to have gone off the radar a bit (perhaps because they don’t advertise much and make extravagant claims) but are very sharp and contrasty with excellent throughput. Many people like the Baader Classic Orthos and imv they are exceptional vfm. I don’t share the view though that they’re as a good as the older BGOs and they’re not as good, imv, as the Taks of similar design. I think you have to compare like with like in terms of design: orthos with orthos, plossl with plossl, 82* with 82*, etc. There are bargains to be had and others on this forum are well-placed to tell you what they are, but, generally speaking, I’ve concluded, after some decades of doing this 😐, that design for design, the cheap option is rarely quite as good as the more expensive one. I agree with Rob that it’s best if you can to buy good stuff and keep it. That said, I’ve certainly blundered along the more expensive zig-zag route before arriving at what I personally think is best. It’s also worth remembering that quality differences that might be obvious in, say, a high-end apo will not stand out in, say, a badly collimated Newtonian. And, of course, the fr and other qualities of the scope contribute as well. And then there is the whole issue of ‘feel’, personal preference and taste, which sounds vague but can turn out to be surprisingly important.

Ant, I posted a review of the 3.4 HR on 19th Jan; you can find it via the search with my moniker JTEC attached - sorry, I don’t know how to send you the link directly. Wonderful eyepiece!

That’s for sure ... and there is no lack of opportunity 😐 Notwithstanding what I’ve said in support of film, I’d have to say to the OP that I don’t think there’s any point in taking the film route now. It does most things that astronomers want to do less well than digital, imv, and in any case, the technical support and favoured film stock are no longer there.

😆 Not really, Andrew. Speaking as one who has frequently lugged kilos of ccd equipment off to the Canaries, running the gauntlet of unpredictable checkin assistants, copping sometimes massive excess baggage fees, scrambling up mountains, grovelling in the dust to polar align, tripping over birdsnests of wires, falling asleep as the imaging equipment ticks away before staggering blearily back down again and crashing out in an uncomfortable bed ... that is masochism. Trust me, the work with film - just a camera and a good ‘ol GPDX running off the car battery ... by comparison, that was bliss. The real point is that, in that specific application, that particular film did better than digital - in everything else, of course, digital wins. As for using camera lenses on ccds, given the short fls typically involved, that’s possibly the technically least demanding kind of ccd imaging you can do. No getting away from the wires, of course ... 😖 John

Sorry, I need to correct something I wrote above: the lens I mentioned is the F lens, 250 mm f4 Tele-Tessar, not the CF. The F lens is shutterless.

Very much with Olly on this. 10 years ago I used to image widefield from very dark sky locations using a Hasselblad medium format camera and Kodak E200 film and exposures around 20-30 minutes. Those projected 6x6 cm slides were absolutely stunning. E200 had a colour palette that rendered the sky background nicely and showed sufficient red sensitivity to record HII regions more pleasingly and convincingly than available ‘one shot’ digital techniques. If it was still available, I’d still be using it for that sort of imaging. But it’s gone ... I continued to use the Hass. lenses for CCD imaging and they work well; if anyone wanted to try that, the 250 CF is imv the pick of the bunch. Very sharp even wide open and, designed as it is for 6x6, swallows up many CCD sensors (mine was the QSI583) with ease. No question of the advantage of digital techniques in most applications, but I think the demise of this particular film stock has left a gap that hasn’t yet been effectively filled. All that said, it was medium format kit which scanned produced a lot of data and big file sizes - I have an image of the Cygnus region that comfortably prints to a metre square. 35mm would obv be more limited. Medium format lenses can be picked up pretty cheaply s/h - if you wanted to give it a go with ccd, you’d need to find a way to attach them to your CCD as, afaik, there aren’t ready made adapters available. Worth the trouble, because, from what I’ve seen, they clearly out perform lenses like the 35mm Nikons.

Thanks very much all for your generous advice! I’ll go, for now, with the SkyTee - it’s received a lot of support, is available and relatively affordable, I already have some of the extra bits I’ll need and I like the idea of slo-mos. 👍🏻

Well, make of this what you will. I emailed Teleskop-Service with the question: ’Do you have an alt-az mount that you could recommend for a TEC 140, please?’ Here’s their reply: ’We only have one mount that is stable enough.’ And they sent the following link - oddly, no mention of the Ercole. https://www.teleskop-express.de/shop/product_info.php/language/en/info/p4537_TS-Optics-AZ5-Azimutale-Montierung-mit-Stativ-und-Feinverstellung.html

Thanks John. Looks fine 🙂. The TEC is a bit longer and heavier than the TS, I think, but not hugely so - looks definitely worth a shot. I’ve also asked TS for their opinion - wonder what they’ll come up with 🤔

Well, that is tremendously helpful and reassuring ... thank you all so much for taking time to respond. In fact I’d dismissed the SkyTee because I didn’t think it would be up to the job, but in view of what some of you have said (John and Jam1e1), I’m inclined to give it a go. I already have a tripod and the pillar that will fit, so, by comparison with the Ercole, the other clear contender, it will be the least expensive way to try out the idea in principle - and it might turn out to be ‘the answer’ 👍🏻 John E

Thanks very much everyone for your advice and suggestions and those invaluable reviews - that’s genuinely helpful. I’ve been pondering this for a long time and not been sure which way to go between the lighter options that are affordable but might not be up to the job and the massive ones that’ll do the job but are expensive. As John says, there does look to be a gap in the market between the two. Of the mounts that are available and affordable, the Ercole looks to be front runner with maybe the SkyTee worth a look as well, though FLO advises the load capacity of the SkyTee to be lower than the Ercole’s. So the Ercole probably; and thanks JeremyS for the adapter link - It looks as though something should be possible. John

Thanks PhilipR. It looks as though the Ercole would certainly carry it, though I’d have to find a tripod with suitable scope swing clearance at the top - the Berlebachs, which I’ve used, are great but expensive - I’ll need to investigate whether it could be attached to something I already have, e.g. the EQ6 original tripod. The Swiss AYOII I’d looked at but thought marginal weight-wise and expensive. So far, subject to tripod, your suggestion of the Ercole looks like the most cost effective option for something lightweight and simple. Thanks again. BW John

Thanks JeremyS. I’d been given similar advice about the Ioptron - pity, because, though I’ve done years of virtuous star-hopping, I like goto as well. The figures, 16kg a side, suggest that the AZ8 ought to be up to it. Maybe extrapolating from the GM8 equatorial isn’t strictly indicative, given that with the simple, visual observing I have in mind, there’s no driving involved, PE to think about, etc? And your C9.25 , though it’s shorter, must have at least twice the focal length of my TEC, which might make for a difference? I’mvery pleased indeed with the AZEQ 6. I can’t think of a better option. I’d just like to find an alternative to unbolting it, lugging it around, etc. That, rather than the wires as such, is what I’m trying to an alternative for. It would certainly be interesting to know whether manual slo-mos could be attached though. Thanks again. John

Does anyone have any suggestions for a portable alt-az for a TEC 140, please? The OTA with dovetail, tube rings, prism, eyepiece, etc maxes out at around 12 kg. At the moment I use it on an AZ EQ6 mounted on a pier - as you’d expect, this works well. For occasional visits to dark skies, I unbolt the mount and cart it off, wires, power source, etc and set up using the original tripod. Again, in terms of functionality in the field, this works fine but it’s a lot of fuss. As an imager, I know what terrific fun it can be grovelling around getting polar alignment, disentangling birdsnests of wires, tripping over power supplies, etc - which is why for visual observing, I’m looking for simplicity. I’ve looked at the AZ8. Does anyone have experience of these? For goto, the bigger Ioptron looks interesting, but I suspect it’d be marginal for my setup even for just visual. I’d be grateful for any insights and suggestions anyone might have!

All the best with your search. I absolutely think it’s worth persisting with. If you find a pair you like and if your experience is anything like mine, they’ll bring a whole new dimension to your observing. 👍🏻