Highburymark

Nice report - and very encouraging about the XO 2.5, Gerry. Hectic work schedule means I haven’t had a chance to really test the 5mm yet.

So you’d get rid of your Ethos John? At current prices they would be very expensive to reacquire if you missed them.

Nik - I will try and PM you about this this weekend - just super busy with work at the moment so don’t have time right now. I have some experience that’s relevant.

Excellent! - sounds like you’ve got a good one. The Quark will be stunning in your bigger refractor under the right conditions! It’s a real learning curve working out how to get the best out of these type of filters - but really good idea to start with the smaller scope. You should get more contrast on filaments with the 102mm with the slower focal ratio. One option for the future is to mask down the 102mm to 80mm or so - the slower the focal ratio, the better definition you’ll get on surface features.

Good spot! A medium C class is about half way up the classification rating for solar flares, so quite substantial. Don’t know what scope you’re using, but your Quark is perfect for high magnification flare watching when conditions are steady. I was incredibly fortunate last year to witness an X class flare on the limb which I could see moving in real time - without doubt the most amazing thing I’ve seen through a telescope. Hopefully there will be a few more this year.

No it doesn’t Gerry - Solar Spectrum is a US company - they are just marketed by Baader. Also the Baader Sundancer (Quark type filter) incorporates a Solar Spectrum etalon, but the etalons are all made in the States. Very nice quality on the whole - but PM me before you press any buy buttons.

The Baader ERFs are highly rated. Speaking of enthusiastic SV marketing, Baader’s blurb for its ERFs describes them as “hellishly diffficult” to make, with “the world’s most advanced coating machines, inspected on a Carl Zeiss optical bench. 1/10 wave”……. so should be as good as any ERFs.

That’s the question I was going to ask too. I found a couple of threads on CN in which people say they’ve used ERFs successfully as flats for DPAC - but they give no more detail.

I remember reading that energy rejection filters used for solar Ha might make good flats for DPAC testing. I have a 130mm Baader ERF that I use with a Sundancer/Solar Spectrum etalon - and I have a Ronchi eyepiece. Hmmm. Need to look into this further.

For an $18,000 triplet, I agree. But the vast majority of scopes sold as ‘apos’ have varying degrees of CA and SA. It’s why we can buy pretty good ED doublets for £300+. We can’t expect perfection with such competitive products. The only loser in the long term if we expect too much from cheaper scopes will be the consumer.

I read the Suiter book, and have to admit half of it flew over my head. However I understand the basics, and for people like me, the simple star test, done properly, is enough to establish whether a telescope is doing a good enough job to be happy with it. Only one of my refractors has ever shown a near perfect star test - the TSA120. The others have shown some false colour at high powers, and clearly contrasting rings either side of focus. Yet I’ve been happy with their performance under the stars. So, for most amateur needs, I agree DPAC results are not needed. But I’m interested in what they can teach me about optics - that’s the attraction rather than trying to establish whether my scopes are perfectly figured. The hi-fi analogy is a good one - I sometimes wonder whether hi-fi buffs are too wrapped up in sound quality to enjoy the music they are playing.

Three things: I second Jeremy’s comment earlier - I think Nicos has done a great job moderating the CN thread. Rather you than me mate…… I’ll follow your DPAC progress with interest Gerry. I don’t think you need a justification for investing in this gear besides an interest in optics. But whether I’d submit a telescope I am entirely happy with for testing is another matter. Perhaps it would show up my own shortcomings as an observer more than anything else…… With the quality of premium refractors so high and consistent these days, the CN thread has made me wonder the ramifications of amateurs having access to kit measuring how solar Ha etalons perform. Compared with expensive apos, the variation in etalons is dramatic - and yet a few solar experts are now able to test Ha filters with hydrogen spectrum tubes. That really could shake up the market.

On Gong, the prom is significantly taller than visible image - someone there needs to invest in a bigger blocking filter……. It’s obviously a real beauty. But no prospect of clear skies this afternoon sadly.

Same here in London - clouded out

Just a word of warning. If you struggle to merge properly collimated binoculars, it’s very likely you will struggle with binoviewers too. So if you can possibly test a pair first it might save you a significant amount of money. Even some of the most experienced observers have trouble with them - so it’s not uncommon.

That’s the problem Neil - every etalon is different, as Peter has highlighted. I’ve seen some single stack scopes that perform like double stacks. It’s become a cliche but it’s luck of the draw. The best advice if you’re buying new is to choose a retailer with a good returns policy like FLO, just in case you get a lemon - though these are pretty rare these days, particularly with Lunt. The LS40 seems to be a particularly good scope going on forum reviews alone. The other option is to wait for the right secondhand scope to come up, which they do fairly often. This also gives you the opportunity to try before you buy, so you know what you’re getting.

There’s a double stack filter for the Lunt 40 being launched - don’t know if that would be in your price range but I’d take that over a PST double stacked if possible. If that’s too pricey, then personally, I’d go for a Lunt 50 SS over a PST DS, and wait to save up in the future for a secondhand Lunt 50 DS filter, no matter how long it takes. In the meantime you’ll still get nice views - in particular of prominences, which are stunning in single stacked scopes, although you’ll get less detail of surface features like filaments. But the Lunt 50 will also give you more resolution than the PST - and it’s considerably better built. The PST is really showing its age now, and the customer support from Meade is patchy since the company’s financial problems a couple of years ago. So my decision would be to go for the Lunt 40DS if affordable, and if not, LS50, with a view to double stacking in the future.

They must be DFs, I reckon Jeremy. The DCs have the extra section before the focuser, and the DZs have dew shield screws. Do I win the nerd of the day award?

They can be - I had a Baader MkV which was very heavy, but the cheaper pairs (WO/Celestron/OVL/TS etc) and the more expensive Maxbright II are reasonably light - you can compare weights on FLO’s website and those of other retailers. Most people use smaller eyepieces with them to keep the weight down. Having said this, even the lighter units still require a good focuser. I’ve had a couple of scopes with stock focusers that weren’t robust enough for binoviewers. Then there’s the issue of working out which BV/barlow/EP set ups come to focus in your scope. Lots of research to do - but the views are very much worth it.

Fantastic - I’ll be interested to hear how you get on with the eye relief. I’m hovering above at the moment with the 5mm to avoid any contact with the lens, so not quite seeing the field stop - but am finding it’s relatively easy to hold the view.

I haven’t compared them tbh Gerry - I tend to use them for different functions, and physically changing from an extender to a barlow during a session is a bit of a kerfuffle. I’ve heard good things about the ES 82 degree range at shorter focal lengths - at least as sharp as Nagler T6s.

I do Gerry - I have a VIP too and my feeling has always been that exceptional eyepieces don’t stop being exceptional with the best barlows and extenders. I think I remember Bill P saying the same thing once with barlowed orthoscopics. I stopped believing in the minimum glass rule when I first looked through a six element TOE.

Highest power I generally use with my TSA-120 is 360x with the TOE 2.5mm. The 5mm XO (although some say it’s 5.1mm) will give me 180x - perfect for average evenings. But I bought it for better than average evenings! So I have the 1.5x Tak extender which will bump things up to 270x. Yes, it’s more glass, but then it turns the TSA into an F/11.25 planet killer.

I’ve reported this elsewhere several times, but I find XWs and Delites impossible to split at planetary powers. If you want width, go for the XW, if you want smaller size and weight, go for Delite. There’s a tiny bit of edge false colour in the XWs, but otherwise, both ranges are pretty much perfect, even in an F/6 scope. However, the TOEs (and presumably the HRs) clearly show intricate planetary detail more readily than either, as long as seeing is steady. What will be interesting is establishing how well the XO performs in this company. The main drawback with the XO is obviously eye relief - the TOEs are very comfortable by comparison (10mm ER rather than under 4mm), but it’s easy to hover above the lens so you’re not touching it with your eyelashes, but this really requires a tracking mount, as I only see (an estimated) 60% of the fov. To see the field stop, you need to get much closer, and make sure you don’t blink. In fact the 2.5mm XO has a tiny bit more eye relief than the 5mm.

Congratulations Gerry. Fantastic find. Look forward to hearing your impressions. I’ve just bought a 5mm XO, but haven’t had chance to use it yet. I’m a big TOE fan, so will be interesting to see how the XO compares.