Which Lunt for outreach - 80, 100 or 80DS?
Posted 19 April 2014 - 06:33 AM
One problem - I live in the UK and summer is approaching! While it's not quite "land of the midnight sun" here it can feel like it in June as we're far enough north that darkness (or semi-darkness) only falls at very unsociable hours. But I'd like to keep on doing my astronomy outreach in the summer months if I can, so it occurred to me that a dedicated H-alpha scope might be just the thing - allowing me to do my outreach activities in the daylight.
I'm considering buying the Lunt 80, single or double stacked, OR the Lunt 100 single-stacked (with the possible option of upgrading the 100 to a good double-stack at a much later date). The pressure-tuning system the Lunts use seems to be the thing to have, and the Coronados are no cheaper here in the UK (I was amazed at the cheap SMII 90 deal you guys had in America a few months back, but as far as I know it was never offered at that price in the UK). Anyway, I'm a little bit torn between the 3 Lunt options on my list and I'd appreciate some help in deciding between them. Any and all opinions would be welcome but I have some specific questions too:
1) Would the view provided by the double-stacked 80 be "too dark" for binoviewing? The first role of this scope would be for mono-viewing public outreach (for simplicity's sake I wouldn't often do binoviewing for outreach as it's too much to adjust and explain to the first-time viewer taking a quick look), but in rare cases such as doing outreach amongst small groups of patient people, and more generally when I'm using the scope on my own, I would like to binoview. I would prefer to only buy one h-alpha scope (given the prices of them!) and make sure it's something I can use very well for both for mono-outreach and BV'ed personal use. Whatever else might be said about single-stacking, isn't it fair to say that it provides more headroom in terms of brightness than double-stacking?
2) I've heard it said often that the Lunt 80 offers particularly nice full-disc views at "low to medium" powers. But I'm never quite sure what the author has in mind when they say that. Is "low" 30x, "medium" 60x, "high" 90x? Could someone state some specific magnification numbers please, for context?
3) Conversely to question 1), would the 100, single stacked, be too *bright* for full-disc viewing with a single eyepiece? I've seen people say that the single-stacked 100 is a little bit too bright for easy contrasty views of details within the disc, but that you can just up the magnification to help with that. Are they suggesting using a wider-apparent-field eyepiece to maintain a whole-disc view at higher magnification, or are they essentially saying "forget full disc, just look at parts of the disc with a high magnification"? From doing lunar-observing outreach I think a good "whole disc" view matters a lot to inexperienced viewers, so that they can more easily understand what they're looking at. I could go a long way towards answering this question myself if I knew the magnification numbers being bounced around, as in question 2), rather than just "high, medium, low", because I would know what higher-mag eyepieces I have that could still frame the whole disc and just how high I want to push the magnification to balance out the brightness.
4) Out of the 3 scopes mentioned which view would members of the public, having never seen the sun in H-Alpha before, enjoy the most, in your opinion? I'm guessing that the 80DS would do the trick brilliantly. But does it, for example, leave much to be desired on the visibility and noticeability of prominences? How much better or worse would the single-stacked 80, and single-stacked 100, be for making prominences bright enough to be noticeable? I am currently under the impression (feel free to correct me) that double-stacking takes something away from prominence visibility by darkening the image to a point where they're less noticeable. If the double stacking changes the view of surface features from "good" or "interesting" to "fantastic" or "compelling", but the prominences are pretty much gone (at least to the untrained eyes that'll be looking through the scope), then I'm not sure whether to welcome that compromise. And what if the single-stacked 100 provides more of a "something of everything" view, thanks to its extra brightness, than the 80DS? I wish I had some direct experience using h-alpha scopes of this size to form my own opinion but you don't encounter them every day!
5) I think that, in general, the basic Crayford focuser will be good enough for my uses (100% visual, with the most stressful usage case being occasional binoviewing). Any objections to that conclusion? Minor point - in a 2009 post (http://www.cloudynig...63/Main/3038783) it was stated that the Feathertouch focuser upgrade is nice to have but has a much shorter (1.5") drawtube than the standard Chinese Crayford focuser (3"). This might make a difference for binoviewing, so does anyone know if it's still true? I'll check with the retailer when I make a purchase too of course.
Oh - and sorry for asking a silly question, but is the basic Crayford focuser easily rotatable? I find that quickly rotating the focuser can be one useful way of compensating for height differences when doing outreach, especially when children are involved.
6) Mounting requirements aren't "really" a consideration as I have a couple of over-sturdy mounts that I don't mind lugging about and that would easily be stable enough for either the 80 or the 100. There might very well be something to be said for the grab-and-go potential of an 80 on a lightweight mount, but I feel like I've already got too much kit so the prospect of buying another tripod (this time a lightweight one) doesn't really appeal right now. Maybe a consideration for another time, but a minor one. Perhaps more relevantly, though, I *might* like to mount my 6 inch refractor (for white-light solar) and the new H-alpha scope side-by-side for my outreach activities (on, perhaps, my AZ-EQ6 mount) and maybe the bulk of the 100 would mean this was pushing things too far while the 80 would be just the right size in this role. It's at least as likely, however, that I wouldn't bring the 6 inch refractor along at all for daytime solar outreach and so I'd want the h-alpha scope to stand up for itself as well as possible in terms of the views it provides. (One more, incredibly trivial, aspect - if you're trying to get passing pedestrian traffic interested enough to stop and take a look, I've learned from experience using the 6 inch refractor that having a "big" scope is excellent bait, which may be something in the 100's favour over the 80s. But that's only a very minor point!).
Any advice that you can offer would be gratefully received. I'm acutely aware that I'm fairly ignorant and inexperienced when it comes to H-alpha viewing so I need all the help I can get!
Posted 19 April 2014 - 08:35 AM
I would consider the LS80 DSII or the LS100 SS for now. The DSII brings such advantage to the LS80 that it would be a shame to skip it. Others have enjoyed the LS60F on the LS80 (blacker sky, but less detailed disk). I think portability would be my main discriminating factor between the 80 and the 100 (assuming you get a smaller case for the LS80).
1. I use my LS80 DSII exclusively with binoviewing, even for public outreach. You learn to judge people's inter-pupillary distance pretty quickly. I use a hood for higher powers (above 80).
2. I use a Denk II Supersystem binoviewer. The low power arm is 35-40, the medium power is about 55-60, and the high power is 80-95. (The reason for the range is that the nominal magnification does not match my measurements, and I am not sure which is right.) I also use very high power with a Barlow, bringing me to about 140x (definitely needs a hood and good seeing).
3. Don't worry about too bright. You can always add a filter. And the LS100 SS can indeed also give a nice disk image. I find the LS100 SS significantly superior to the LS80 SS because the LS100 disk image is better and the prominences are indeed brighter and sharper. Comparing the LS80 DSII to the LS100 SS is more of a tradeoff.
4. At NEAF last week, my LS80 DSII with binoviewers produced a lot of "wows" and "whoaa" and " oh my ..." from people who had never viewed before. The binoviewer makes it come to life for them. Prominences are easily visible in the LS80 DSII even for people looking through for the first time.
5. Get the Feathertouch and the BF1800 if you plan to binoview. Period.
6. I think it comes down to mounting. I love the LS80 DSII, but many love the LS100, and the latter can later be double-stacked. At NEAF, the LS152 DSII was most impressive. I wondered also about the LS100, but now I think if I get the money to upgrade, I would skip over the LS100 to the LS152 or a rear-mounted filter and hopefully keep the LS80 DSII forever.
- Stellarfire likes this
Posted 19 April 2014 - 08:59 AM
I would just like to add: I was told at NEAF by Andy Lunt that down the road they are going to make an improvement an improvement in the DSII modules for the LS80 and LS100.Adding some kind of polarizing filter. This is already incorporated into the DSII for the LS152 and helps eliminate the "red glow"
Posted 19 April 2014 - 09:53 AM
Bill, I'd seen your comment about the upcoming change to the DSII modules, in the thread about NEAF, and it did make me wonder. Of course one can't know how long it might take for them to appear, or whether we can be certain it'll happen at all (plans can change - or maybe somehow the newer DSII won't be all it's cracked up to be!), but the possibility does perhaps help tip the balance towards the LS100. If the single stacked 100 more readily produces a great image than the single-stacked 80, and there's an advantage to waiting for a "new and improved" version of the DSII, then that's a point in favour of the LS100 since I can have something very good right now without running the small risk of regretting buying the DSII "too early". But context is important - I am fully prepared to believe that the improvement the current DSII makes to the image is already amazing enough that this isn't a big issue either way.
I'm reassured, as well, to hear that prominences are still "prominent" (OK, I'll get my coat) with double stacking on the LS80.
It's interesting, or perhaps I should say reassuring, to see the LS80DSII vs LS100 SS question described as a "tradeoff". I like the sound of that - a closeish balance of different advantages with neither being at all a "wrong" choice. Considering the price similarity between them (when you consider the feathertouch focuser, BF1800 and the extra DSII add-on for the LS80) it really does suggest, as George says, that it comes down to the importance I personally place on portability (and perhaps the question of how likely I am to add a DSII to the LS100 later on - but it really won't be any time soon as my budget is at its limits already).
Thanks for giving a simple answer to the "Feathertouch or not?" question! Can you comment on the drawtube length, though? Or does it not make any difference in your experience? The binoviewer I had in mind was my Binotron-27, with all the usual powerswitch and OCS malarkey, so if your Denk II is working well with your LS80 then I guess there is nothing to worry about there.
(I was already planning on the BF1800 instead of the 1200 for the sake of binoviewing, sorry, should have mentioned it the first time round.)
Posted 19 April 2014 - 10:56 AM
For the Denk II (and I assume for the Binotron), I put the OCS on the scope side of the BF1800 (removing the 3" tube). I use a T2-to-48mm adapter that I got from Russ, then the 2" OCS, then a 48mm-to-48mm extender that I also got from Russ. The result is 2.5" stack on the telescope end of the BF1800. I generally keep it about 0.5" out from the focuser and reach focus easily at all three powers. Bottom line on the Denk is talk to Russ and he will send you the right parts.
(Bill is right on the other issue, but Lunt is likely offer an upgrade to older DSIIs. Talk to Rikki or Andy. I am already happy with mine.)
Posted 22 April 2014 - 02:35 PM
How about buying the single stack 80 in the meantime? Well, while I'm sure the SS view on the 80 is really quite nice I suspect I'd feel like I was waiting around until I could afford to add the DSII, and perhaps wasting my time a little until I had it. People don't seem to speak as highly of the single stacked view on the 80 as they do on the 100, and when they talk of the 80 they strongly recommend going straight to double stacking for a particularly excellent view. If anything, the scope where DS is to be viewed as an "optional upgrade path" rather than a "get it ASAP" must-have is the 100. Is that a reasonable point of view? The best view available that's just barely within my pricing comfort zone is the single stacked 100. It may be as simple as that.
Perhaps it would do no harm to elaborate a bit on my expectations or assumptions about how I'd do my viewing. The analogy I am perhaps unwisely or naively applying is that of lunar viewing. My own personal preference, for lunar outreach with first-time observers, is to give them a whole-disc view so that the observer can tell where they are - "see the wood for the trees", as it were. If you throw them straight onto a highly magnified subset of the moon they struggle for a sense of scale, or an idea of how much they have zoomed in. A good bit of magnification is very welcome too, of course, to provide rich and interesting detail to study, so I use wide apparent-field-of-view eyepieces of shortish focal length to have both a decent magnification and a full disc. As long as the eye relief and general comfort/usability of the eyepiece is adequate, I think this works well. I have been assuming that a similar approach might be good for h-alpha: a moderately well magnified, wide view that still frames the whole disc - 80x, 100x perhaps? I suspect that the 100mm scope is a slightly better fit for this philosophy because it has spare brightness to offer.
I can think of at least one snag with this assumption or expectation. I have heard that the uniformity of the view, from one side of the FoV to the other (or rather, from the center towards the outside of the FoV) can often be imperfect for h-alpha viewing due to the optical necessities of the etalon designs. I'm not entirely clear on whether this is a point that applies mainly to double stacking and not much to single-stacking (may just be wishful thinking on my part - perhaps it applies to both, but just somewhat moreso to DS). Regardless - if this IS the case, then I wonder whether wide apparent-FoV eyepieces are wise for h-alpha viewing.
I'm thinking, by analogy, of coma in reflecting telescopes. Essentially I believe it's proportional to apparent field of view. With standard apparent-field eyepieces (~50 degrees) it's less noticeable, if at all, than with widefields of 70+ degrees. In a reflector, you can add a coma corrector and then use as wide-field an eyepiece as you like, but if a coma corrector is not an option and you want a clean view framing an area of sky of a certain size then you have to reduce the magnification and aFoV.
Any thoughts on whether this is meaningless worrying? I'm rather fond of my Naglers and Delos and might like to keep using them with the h-alpha scope, but perhaps HA viewing requires a different approach and attitude. Then again, maybe the order of magnitude of any off-axis departure from the sweet spot is nothing to be concerned about.
If not, then I'd probably start at 80x and go from there (unless my expectations are totally out of whack with what is, in practice, most aesthetically pleasing). In which case, the 80 may be short on aperture.
You can probably tell that a lack of experience is hampering me more than a bit.
All that said, the 80 does have a certain intangible pull in terms of its sheer portability. I really don't want to buy and store any more tripods than I already own, and everything I own is heavyish, but all the same I shouldn't be too sure of what's in my future and the sheer potential convenience of being able to just pick up and carry the 80mm rig somewhere I wouldn't otherwise be able to go, to share the view with people I might not otherwise be able to reach, should not be quickly ignored.
On a very different topic - with some solar viewing systems I've seen talk of the equipment steadily degrading with time, needing maintenance or replacement after a few or several years. I'm thinking of, for example, the rusting issue on the PST, and I may have seen something similar said regarding powered Daystar filters, the sort designed to be used at the focuser-end of ordinary refractor (which a vendor has recently suggested to me). Does anything like this happen to Lunt scopes? I haven't seen anything said about it that I can recall. I know the current designs may not have been on the market long enough to be sure either way!
Posted 22 April 2014 - 03:49 PM
I think there are going to be differences from person to person in what they enjoy seeing with their solar scopes.
I have or have had the LS80DSII, the LS100 and DS and the LS152.
I thought the 80 was really really good for full disk views and with the DSII. I loved those views. It had the best low power full disk views.
The 100 SS might have had a smaller sweet spot so the full disk views were not as good as the 80DS but still really very good and this is SS. The 80 had the advantage of the DS here too. But the prominences for me were a lot better on the 100 than on the 80 SS because I could use higher power and get really close to them without them being too dim and this is what I really liked. I sold the 80DSII but I really would like to see it again for those full disk views. The 100DS can be really nice too but does not change the view as much as adding the DS to the 80. At least in my scopes. I also think there is variation among the scopes.
The 152 is the best for prominences because it is brighter yet and when seeing is good you can use really high power. Once again the full disk views are not as good as the 100 because they are too bright and there is less contrast. For lower powers I stop it down to 100 and get similar contrast but the sweet spot is quite a bit less for the 152 than the 100 so I have to move the scope around to see better all the detail in all places.
The 152 is a large aperture jump over the 100 but the view is not way better. I chose the 100 over the 80DSII but I have thought that perhaps now that I have the 152 I should have kept the 80DSII because then I would have the best full disk views and the best prominence views. The 100 is a perfect compromise I think. I have never looked through a 60 or smaller except the PST.
I hope this helps. I recall reading where someone set up an 80 and 100 side by side for public viewing. I don't remember if the 80 was DS. But some liked the 80 view better and some liked the 100 better. It is too bad we can't have the best of everything with one scope but I think each scope offers something better than the other and you have to decide what you like best.
I have one mount and it is a good one because I use it for my large refractor also so portability was not an issue for me. But the 80 is smaller and may work well on a smaller mount than the 100 if that is a consideration for you.
I was one who also thought the 80 did best with the DSII for the full disk. Without it I could not see the detail well. It was a major improvement. But for prominences I liked it better in SS. I know some are happy to keep it DS all the time. I suppose if you use lower magnifications only that would be fine. Or perhaps as I said every scope is different. The etalons are not all the same.
Best wishes in your decision. All the Lunt scopes are great.
Posted 22 April 2014 - 06:12 PM
A couple of comments:
1. For public outreach, I lean toward lower powers for the reasons you state, but even lower than you mention. Most of the time about 40x and at most 60x. It's not just brightness, but when they see the full sun and prominences all around, it has much more impact. I think high powers are more for your enjoyment.
2. They are supposed to last forever. My 2000 Coronados, which are similar in design to the Lunts, still work. One de-contacted at 12 years, but I re-contacted it. The blocking filters seem fine. But designs do change and any company can have a problem.
Posted 22 April 2014 - 06:32 PM
Posted 23 April 2014 - 08:32 AM
As I briefly mentioned in my last post, and just to completely derail the conversation, I have had a 0.5A Daystar Quantum system suggested to me by a vendor. This would be for use with my 6 inch refractor. The price would be broadly comparable to the Lunt 100 (single-stacked). Interesting that a 0.5 Angstrom system with similar or greater aperture would be on offer at a similar pricepoint.
The system requires power, and I'm not sure my current battery (at a mere 24 Amp-hours) would keep a heating element running for long, but I can think about that. EDIT: Cobblers! Apparently the little oven only uses 0.8A. My battery should be OK when also powering my mount, unless I'm observing from dawn to dusk!
The Daystar system would involve a choice of compromises. As I understand it different energy rejection filters would be needed, for use with my 6 inch f/8 refractor, for full-disc viewing at a substantially stopped-down aperture vs for zoomed-in viewing at (closer to) full aperture. The maximum field of view available when binoviewing would be somewhat limited, too, because of the need to use a strong Powermate to give the Daystar system a long enough focal ratio to work well and the need to only use 1.25" eyepieces when binoviewing. EDIT: Wrong. A UV/IR cut filter is all that's absolutely needed, I'm told. Any aperture stops would only be used to permit the necessary f/30ish (generalising a bit) focal ratio to be achieved with lower magnifications, by cutting down the aperture and then using a less powerful telecentric barlow. It's still in the realm of relatively high magnification no matter what, but cutting the aperture down to 130mm or less would (it seems) still permit a full disc. I think that's only with single-eyepiece viewing, though (with a 55mm Plossl)! The ~1.25" field stop limitations when binoviewing would seem to become a lot more significant that I'm used to when doing night-time observing at a mere f/8!
I've read one or two mixed opinions of Daystar products but I think that at least some of them were regarding very old equipment - 15+ years old. It was said that the system wasn't working perfectly any more because more than one component of it was getting worn out (I'll try to dig up the link to the thread, with more details, this evening). Does anyone know if the current Daystar kit still has a limited lifespan?
I guess there's some neatness to not having to buy another whole OTA for solar viewing, though because I won't have that 2nd OTA I'd be unable to do any kind of side-by-side white light vs HA viewing. And there's extra setup time given that the Daystar rig requires some assembling each time it's used (another plug needing power, the need to fit a front filter to a scope that won't always be using one, etc.), which may mean I'm pushing the limits of convenient setup times a bit given that this is a biggish 6" refractor already.
(I ought to admit I may have been giving the Daystar system an unfair hearing through sheer ignorance so I will be posting back to correct myself on any doubts that I've since learned to be unfounded.)
On the whole I'm still more sympathetic to the idea of a Lunt scope than the Daystar, I think, just for the sake of simplicity and one scope doing everything quite well. It seems to me that 100mm of aperture, single stacked, is a pretty good all-rounder.
If it comes down to a Lunt scope after all then the question of the value of portability, and whether I'd want to do side-by-side viewing or not, remains but that's something for me to decide for myself based on my own preferences. Thanks again.
Posted 23 April 2014 - 08:48 AM
Posted 23 April 2014 - 02:28 PM
frolinmod asks for advice on choosing between "LS80T DS vs. LS100T". On the 2nd page (post #5449191) he later shares his own conclusions having tried both scopes:
Second page of the "Questions about my new LS100 and LS100F" thread - Kent10, jerwin and frolinmod discuss 80DS vs 100SS.
"Lunt 80 vs Lunt 100" thread from March 2014. This thread lived and then probably disappeared again during the temporary switchover of the forums. I only have a google cached-page link to it:
"Thoughts on my new LS100//LS100F" - discussion of use of a front-mounted double stacking module on the LS100, rather than a DSII. Initially some tweaking seems to be needed but Kent's very happy with the views by the end of the thread. Others discuss the 80 DSII by contrast.
Another 80 vs 100 thread: "Lunt LS80 + DSII + Mark V?"
A long thread - "If you had a choice, which Lunt would you choose?" - in which the 80DS and 100SS are discussed, including in context with their performance relative to the larger 152.
Discussion of binoviewing with a Lunt 80 SS.
"Ordered Lunt's New LS80THa/PT/B1200 and DSII..."
The author, WirelessDude, waxes lyrical about how much he's enjoying the views with binoviewers and ('only') single stacking on an LS80, on the 2nd page once all the kit has arrived and he's had time to test it out.
"Lunt Choice DS60/80 (Crayford/FT)" Starts out talking about focuser options and 60 vs 80, but moves on to discussing the merits of binoviewing and the merits of a portable setup (including details of George9's nifty LS80 rig)
One of the many "single vs double stack" threads, named "Single stack sometime better than double stack". A quote:
"The detail you can see single stacked is impressive, but once you see the sun at < 0.5 Angstrom double stacked -- well I'd say 99 out of 100 people will prefer the double stacked hands down. It is not subtle; it's a major improvement - especially visually. I've often heard "now my wife is going to be very upset with me - I have to have this." Then when the wife takes a look, she agrees with the additional investment!"
A small thread about mounting the LS100: "Mounting Lunt 100mm DS?"
Another thread on mounting requirements and portability of LS80 and 100 (mainly 80) - "Lunt LS80 PT"
Another thread about mounting the 80 and 100, this time regarding a DM-6 mount - "How to Mount My Lunt LS80 and LS100 onto My DM-6"
Thread about the recent NEAF show. "New at neaf part2". Including discussion of the new LS50, and mention that a tweaked DSII module for the 80 and 100 scopes may be on the way.
A range of options discussed in brief in this SolarChat! thread: "Choosing a Large Aperture Solar Scope in the UK"
Posted 23 April 2014 - 07:41 PM
Posted 24 April 2014 - 01:14 AM
Posted 24 April 2014 - 08:55 AM
Would, then, a "single" 0.5A filter as in the Daystar lose some of that advantage? I think I'm being needlessly theoretical again - if the blasted thing produces good views, then who cares.
What bugs me about the Daystar is that I haven't yet stumbled across many user testimonies of what people liked and disliked when using their Daystar filters (only occasional comments about an old filter needing servicing). For the Lunt scopes I'm looking at there are all sorts of comments regarding what people liked and disliked when using them, and even comments on relative differences in side-by-side comparisons.
With a dearth of Daystar user reviews it feels risky to buy one. If I've missed a stash of reviews that anyone knows of, please let me know (I'll keep looking too!). I do know, for example, that with the right aperture stop and powermate combination I could get a whole-disc view with the Daystar, but I still don't know what to expect regarding how good that full-disc view would be compared to anything else.
The Lunts may, in certain circumstances, have sweetspots or a red glow around the edge of the view. I'm sure the Daystar isn't all perfect either, but it's "the devil I don't know" right now.
George wisely pointed out early in this thread that my decision may come down to my own personal preferences for portability. I seem now to be faced with the full range of sizes and weights. The Daystar system seems very powerful but it needs my big refractor plus power plus a 10 minute wait for the filter warm up, etc. Right at the other end of the scale the 80 is supremely portable, and quick and simple to setup. Maybe in an ideal world I'd have the 80 and the Daystar - simple, great full-disc views combined with elaborate but high-resolution zoomed-in views. But I'm not made of money!! The 100, at least, is a "jack of all trades, master of none" with an upgrade path to DS further down the road.
Posted 24 April 2014 - 12:21 PM
I'm personally not a big fan of daystar because most of their filters require electricity, the blocking filters eventually wear out, and the field of view tends to be narrow. But some people like them. So whatever floats your boat.
Posted 25 April 2014 - 02:58 PM
All things being affordable I'd probably have a nice, simple, portable and very-effective-at-what-it-does 80 DS, plus the Daystar Quantum system to use with my 152ED for high resolution viewing. (In a perfect world, the Quark would affordably fill the Daystar Quantum's role for me so that I could afford the Lunt 80 as well - regrettably I think it doesn't because of its high 4.3x magnification factor coupled with its inability to switch telecentric Barlow powers to change things around when coupled with aperture stops. The wide interest in the Quark, and the large amount of discussion it's generating, is shedding very helpful light on what people find the Daystar-type views to be like though. Very helpful for me). In this imaginary world I'd sometimes use the Lunt, sometimes the Daystar, perhaps even sometimes both side-by-side.
I may be leaning towards just getting the Daystar Quantum if I can only afford one because it offers versatility in being usable with aperture stops to get a full disc view (and probably a fantastic one at that) when desired, and a when using full/near-full aperture in good seeing. And it costs LESS than the DS80 (given that I already have my 152ED to use it with), while still operating at 0.5 Angstroms bandpass. But the all-conquering ergonomics/value-of-grab-and-go issue could still override all that. Anyway, here are some details surrounding the Daystar system that I'm chewing on at the moment:
- Tuning is slow because it's done by changing the temperature of the etalon. Red shifting takes 8 minutes, blue shifting takes longer. No "quick" adjustment. I suppose once you find a setting that works you can sort of stick with it. But something to think about and less opportunity to experiment in a carefree sort of way.
- Initial warmup time on the order of ~10 minutes
- Needing power isn't *necessarily* such an issue for me. I'd often want tracking anyway, in which case the battery is there anyway.
- High focal ratio in the f/30 range is necessary, to be achieved through use of telecentric barlows (and/or aperture stops - see below). The primary effect being to make binoviewing limited in options without producing too dim an image. Binoviewing full-disc is impossible, pretty much (have to stop down to 80mm, with 2x powermate, to get near!). Monoviewing still "works" well enough with f/30, just use a 55mm Plossl or similar. When operating at full aperture with a 4x Powermate (--> about f/32), on my 6" f/8 scope, this gives a magnification of about 88x and a tFoV of about 0.57 degrees (and is, broadly speaking the lowest mag possible at full aperture - other eyepieces, if used, would be for high magnification views. The only exception being the idea of using a 3.5x telecentric Barlow instead, to push the system's acceptable limits on the focal length to f/28 or just under, but you still end up using the same eyepieces with only a small overall difference made to their magnifications, brightnesses and FoVs).
I think I can't do full-aperture whole-disc viewing, even in mono, with my 6" f/8 scope - Would need to stop down somewhat, probably to 120mm and then use a 3X telecentric Barlow (Televue don't make one, but Siebert do). With the 55mm Plossl this gives a tFoV of about 0.76 and magnification about 65x.
But I'm short on information here. What's the minimum true field of view required for "practical" full-disc H-Alpha observing? I know the Sun is on average 32 arcminutes wide, but how much extra does a large prominence add? And how much extra on top of that would folks (subjectively) consider helpful to give an aesthetically acceptable gap away from the field stop of the eyepiece?
- All things being equal, double stacking to get to 0.5A knocks down out-of-spec "unwanted" light by a substantial amount more than a single-stack 0.5A system like the Daystar would (will add reference later, but I think it's discussed in the above listed threads!), but how much does that matter?
And is that comparing apples and oranges (all things are not equal)?. Plus, perhaps different etalons might let more or less "unwanted" light through in the first place I'd imagine (e.g. where do things settle out in a competition between two "OK" etalons and one "really good" one both aiming at the same bandpass?). Or are there generally no real differences in out-of-spec light throughput in all quality etalons nowadays, such that you can confidently talk about the implications of getting to 0.5A via a single stack vs a double stack?
Posted 25 April 2014 - 03:59 PM
Based on the type of scope you have now (152ED), I'm guessing you like sharp crisp high resolution views of objects. That, I suspect would point more to the higher aperture lunts, imo.. 152mm or maybe 100mm at a minimum. but I'm guessing. Or a good daystar setup. Although I've never personally seen a "good" daystar setup myself.. I've only read about them. You can get full disk views in the lunt 152mm btw..
Posted 25 April 2014 - 04:34 PM
I agree that all the theoretical details completely take a back seat to user testimonies on what they actually like or dislike, in the real world, about their scopes. There's plenty of that sort of information about the Lunts, because there are plenty of Lunt owners about, and conversely for the Daystar there are very few comments to read (good or bad). The only comments I have seen so far are of the kind "my very old model is in need of servicing" - and terribly little seems to be said about what a "modern" Daystar rig does well, or badly, when in good condition! (I'll keep looking in case I've missed the discussions I'm after - in the morning!)
I'm glad of the launch of the Quark for this reason - it's a taster for what a modern Daystar rig might be capable of and it's affordable enough that a lot of people are starting to buy it. It's already getting talked about a lot.
The vendor who recommended the Daystar Quantum to me did so because he thought it would produce a better image than any broadly comparably priced Lunt (it's slightly cheaper than the 100SS! Because I already have a scope to use it with). He uses a Daystar himself, and he swears he'd make more profit by just selling me either of the Lunts I'd been looking at but thinks the Daystar would give a better image. Having dealt with him quite a bit before now and found him to be a pretty honest and fair guy (who's gone out of his way to help me out at times) I am willing to believe him. But there's more to it than "is the vendor giving his honest opinion?" (just to make it quite clear - I'm satisfied that he is) - what about the things he just didn't think to mention because they aren't an issue to him, but might be to me in different circumstances (for example). That's why I really wish I could see more user feedback on the Daystar. "Many eyes" looking at a product are going to spot more points that may or may not be of interest to me.
On paper it looks like there's a lot of potential - and then the only thing to decide is whether I value, for my purposes, a bigger, more elaborate but more capable observing rig (Daystar) or the smaller, portable, easy rig (Lunt) that might get used more through sheer convenience. But I'd much rather have the backup of real world reports.
Posted 25 April 2014 - 05:14 PM
I'd rather rationalize, at least in this way. If I want to buy something.. I'd imagine what would happen if I did actually buy it and the consequences of such actions, and the worst case scenario of what would happen if I didn't like what I bought. But that doesn't work always either.
What has worked for me best (but now always), is if it "feels" like the right thing to do. But that method of course, doesn't work for everybody. And sometimes that has led me to trouble as well too.
Posted 26 April 2014 - 09:47 AM
The clear aperture of the Daystar system is 32mm. As far as my limited understanding extends, this means there'll be severe vignetting with the 55mm Plossl (46mm field stop) I was basing my ideas and sums around. My first reaction is that I'm basically limited to 1.25" eyepieces after all, whether binoviewing or not. Which severely limits potential for full-disc viewing at all (and means that any partial-disc viewing will be narrower than expected!).
I've been googling to get some idea of the relevance/importance of the 32mm clear aperture size, and I've found this thread:
Daystar H-alpha: which Barlow for f/30?
I know that I'll get better views with more aperture, but I am now trying to figure out the ideal combination of aperture and focal length. Daystar filters are nice in that you can use as much aperture as you want. But the clear aperture of the filter unit is only 32mm. This means there is very little advantage to using a 2" eyepiece over a 1.25" with the widest possible field stop. Also, by my calculations, it will start vignetting the solar disc at an effective focal length above 3300mm or so.
I'm not yet sure how he worked out the 3300mm figure, though.
EDIT: I've removed some of this post because I may have gotten things confused and wrongly thought there was a 2nd "catch" to the 32mm clear aperture. I think astrobug is talking about full-disc viewing, not any other situation or restriction on top of that.
For the 6" refractor I'd have used the system with it just seems like there's a lot of wasted potential. 1.25" eyepieces are a really tight restriction when operating at f/30. Not sure the Daystar makes sense for me any more. So I may be back to choosing between the Lunts after all! What a merry-go-round. I apologise for the foolish way I've been leading any (very patient!) readers of my thread down this blind alley.
At least with either Lunt I'll have more simplicity in the setup - and I can't now imagine that the performance of the Daystar would have been wholeheartedly much better than the Lunt 100 (if I were to choose that and, eventually, pay for the DSII module for it - admittedly at first it'll only be single stacked and that makes a real difference) - it'd be better in some ways but just so limited on FoV. The Daystar still has the 0.5A bandpass, at a lower price than double-stacking either of the Lunts, but it just seems like an inefficient system for a 6" refractor now. All the bulk of a larger scope and not all of the capability.
Thanks Bandazar for the advice on decisionmaking - I was certainly hitting the classic "analysis paralysis" stage - but this 'bad news' about the Daystar may have made things a fair bit simpler for me after all.
In fairness I may still be misunderstanding things a bit (again, apologies for any inaccuracies in my posts) but, either way, the 1.25" eyepiece limitation seems like one more point counting against the Daystar and may be all it takes to make it less attractive than the Lunts.
EDIT2: It occurs to me that, in all fairness, I should "check my sums" with Daystar. I'll email them asking for their input and see what they say. It may be that there is some aspect of the Quantum's optical system that makes the 32mm aperture not matter as much as I have assumed. Or it may indeed simply and straightforwardly be that there are "no excuses" or mitigations and it really is a 32mm clear aperture, but perhaps the extent and relevance of the vignetting may be a lot less than I think, even with a 55mm Plossl. Or perhaps there's a compromise level where a shorter focal length 2" eyepiece, of greater FoV and brightness than any 1.25" eyepiece, is vignetted by only an insignificant amount for visual use. Something I should make sure to stay aware of, and acknowledge, is that I know with some confidence that I'm not going to do terribly with any of these setups - it's just a matter of which is slightly more awesome for my purposes! Nice problem to have I guess.
You might be wondering why I'm typing what is fast becoming a long and waffly soliloquy. Basically it's because someone else, sooner or later, might be faced with similar options and they might be glad of whatever rare and scattered nuggets of information or ideas are to be found somewhere within these posts (especially regarding the Daystar systems - I can't be the only one who finds some of the details of the system jarring and hard to get used to (f/30 anyone??) and so little is said about Daystars elsewhere). Last of all, I wouldn't want to misrepresent any product so if I've stated an assumption about why something will or won't work, I had better come back and say so if it turns out I'm wrong.
Posted 27 April 2014 - 07:06 AM
The DayStar will be the most fun to tinker with, it will produce amazing high-power views of prominences, and it will be great for imaging. Setting up a 6-inch refractor, power source, imaging train, heat-up, etc. will make you use it a little less and make public outreach more for special occasions. A Lunt or Coronado will produce amazing full-disk images, great contrast on the disk (DS), and good prominences. And depending on which one you get, it will be easy or at least not too hard to set up. That is based on 15 years of owning Coronado and Lunt and (only) ten years of looking through DayStars at the annual NEAF solar party. (In 1998, I wanted a DayStar but it was one of their lull periods, and then Coronado showed up.)
This past solar party, the 7-inch refractor with a Solar Spectrum rear filter (like DayStar) had the best prominence view, but the field had some odd aberrations around the sweet spot. The Lunt LS152 DSII had almost as good prominences and a great disk and the ability to do full disk and no aberrations. The Quark was impressive, I think better than a regular PST, but no match for the Lunt LS50 DS or an LS60, at least for the scope the Quark happened to be mounted on.
One of the biggest amplifiers of performance in H-alpha is a binoviewer. The Lunts and Coronados work pretty easily with binoviewers. I really do not know how the DayStar steup affects binoviewing, but it seems to me that it should only increase the back focus (good news). Remember that binoviewing will further limit your effective field stop to about 26mm, and probably a little less with a practical set up.
All that said, I still hope to get a rear-mounted filter some day.
Posted 28 April 2014 - 04:06 PM
George and Bandazar, I fully accept the point of view that portability may do more good than chasing after the last bit of excellence in the view. I was strongly tempted by that argument. I didn't really make it clear but the reason I spent so long dwelling on the Daystar option, at first and up to now, was that I felt whether I accepted the ergonomic argument or not (which was yet to be decided at the time) I would like to understand the system and what it had to offer, to give it a fair hearing and understand why I might perhaps be prepared to put up with any extra bulk and complexity in its use with a 6" refractor compared to a smaller Lunt. Having learned about it, and spent some days wondering at the back of my mind about what size and weight and complexity of kit is really practical for me, I've decided to go ahead with it.
I strongly suspect that the beauty of the views is going to knock my socks off and make me very eager to get the scope out in public to share it. That's where I settle out on this issue. The biggest limiting factor is always going to be my own spare time and energy, so much of which is independent of equipment used (the least "grab-and-go" part of any rig I own, I find, is myself!). I am already comfortable enough with doing night-time outreach with the same rig (6" refractor on a tracking mount) as I'll be using for the daytime outreach. The only extra complexity is another wire running from my battery to the rear-mounted filter. Warmup time of the filter will be covered by the rest of my setup and mount alignment time I expect. Apart from the minor addition of the new filter everything is as bulky, but manageable, as I'm already used to.
I will add more - details of the exact configuration I intend to use, why I'm not concerned so much any more about the initially counterintuitively high focal ratios, and perhaps I'll add an introductory edit to the first post of the thread to warn future readers that I spoke a lot of BS about Daystar before my later posts. But I'll do all of that in the future when I'm a tad less worn out! Right now I need to catch up on some sleep.
When the time comes for delivery and first use I will be glad to share what information and opinions I can (though in all honesty I'm a pretty inept observer and thus a hopeless reviewer!). The foremost concern for me is outreach. I will be really excited to discover whether, and how much, good h-alpha views can inspire people. And having the ability to operate in the day as well as at night is going to add so many outreach opportunities. The public won't know what hit 'em!
Posted 28 April 2014 - 05:12 PM