ES MaxVision 24mm and 16mm; BST StarGuider 12mm, 8mm, and 5mm - First Light, 22/01/2015

[hgjevans]

Let me say first that, barring the basic 25mm and 10mm eyepieces supplied with my 8" f/5 SkyWatcher, these are the only ones I've used, and they represent my first 'upgrade'. They also represented a sgnificant cash outlay, by my standards, and I sincerely hope they'll be keeping me happy for a good few years to come. So, I have to acknowledge that I might be more inclined to gloss over any shortcomings and talk up their good points - I believe the psycologists call it 'choice-supportive bias'. Accordingly, anyone wanting a thoroughly objective analysis should keep that in mind. Caveat lector!

Anyway, yesterday evening provided me with an unexpected opportunity to try the eyepieces out - I'd received then only a couple of days earlier, and true to form the weather forecasts all suddenly agreed that it would be wall-to-wall cloud at least until the next full moon. But, as I put the wheelie-bin out after dinner on Thursday it was apparent that things weren't quite that bad - plenty of the brighter stars were visible, and some sort of observing would be possible after all. It certainly wasn't great - there was a huge amount of moisture in the air, making the sky-glow much worse than normal, but it was better than nothing. 

As it was a somewhat spontaneous session I didn't really have a plan - except that I would mostly be looking at open clusters and Jupiter. And if the conditions improved as the night went on I would maybe have a look at some galaxies when Leo got up, and perhaps M13 if I could last out myself until the wee hours.

As things turned out, it really wasn't the ideal night for the 24mm MaxVision - the sky-glow was indeed dreadful, with all the water vapour reflecting back the LP. The poor thing didn't stand much of a chance of showing anything with a low surface brightness. Orion was not far from disappearing behind a tree as I finished setting up the scope, so of course I had to take a look there first. The nebulosity of M42 was barely noticeable as I started out with the basic 25mm SW eyepiece, just to establish a reference point, and the difference when I put the MV in was marginal, at best. It was an inauspicious start, but at least I knew it wasn't the fault of the eyepiece. One thing I did notice, though, as I began to swap up through the powers - I was seeing distinct colour in the Trapezium stars. I never had before, and in fact the lack of visible colour in stars had been something that had worried me throughout my time with this scope. I wasn't sure if it was a lack of sufficient aperture, or too much LP, or what. Even Albireo, which I had viewed on my first evening with the scope back in October, had been a disappointment. Well, all of these eyepieces were showing distinct and consistent colouration in the main four stars of the Trapezium - and that was a pattern that continued (indeed, got better) on other clusters throughout the evening. So I guess the SW 25mm and 10mm just lacked the contrast to show up the colour that I had previously expected. It was there alright on bright stars - say mag 5 or better, but really not much beyond that. Anyway, that was a benefit I hadn't anticipated, and the evening - indeed the upgrade - was worth it for me on that score alone.

From M42 I swung back to pick up Jupiter - the seeing here was truly awful, but it was still low over a neighbour's rooftop, so I wasn't expecting too much at that stage - I would be coming back to it later. Even so I noticed that one of the moons (Ganymede, as I later found out) was just emerging from behind the planet, so I watched that for a while, swapping mostly between the 16mm, 12mm, and 8mm. It was at this point that I saw that there seemed to be a firefly dancing about in the line of sight. Eventually I realised that it was a reflection of the image of Jupiter off my cornea, back to the glass surface of the eyepiece, and back again into my eye. The phenomenon was only apparent with the StarGuiders, and I presume it was down to the particular shape of the rear surface. It wasn't a big problem to me, and it wasn't apparent with any other object viewed that evening.

Moving on from Jupiter to something a little higher up with a tad better seeing, I took a look at what has become an unexpected favourite to me with the 8" - M37. This was where I really began to notice the astigmatism in the 24mm that Alan Potts described in his report earlier this week. It was definitely there, and there seemed to be plenty of it. But whereas Alan described its appearance as resembling coma in the f/5.26 Maksutov Newtonian, with my f/5 conventional Newtonian I saw only the usual seagulls - quite sharply defined seagulls. Their shape and size varied quite a lot with re-focusing, which made me wonder if the optical designers had done as designers of photographic optics sometimes do, and deliberately allowed some uncorrected astigmatism to compensate for a lack of field-flatness - pure speculation on my part, though. What was more encouraging was that the contrasty nature of this eyepiece was becoming apparent. I would definitely want to reserve final judgement on it until I can try it out on some more diffuse objects from a darker site, or at least from here on a darker night!

The 16mm MV was a different story, though. Any residual astigmatism was much less apparent, and if I hadn't been looking for it I probably wouldn't have thought about it at all. I had been worried about eye-relief too, having read some negative things about that. Had I read them before I ordered it I probably wouldn't have considered buying it at all, but as it turns out I'm quite glad I didn't, because it was fine in use, and actually one of the real success stories of the evening. I also tried the 12mm and 8mm StarGuiders here, and they were fine - no astigmatism with them, indeed no problems at all. The seeing, though, was evidently still not good enough for much higher magnification (the 8mm gave 125x in my scope), and I didn't bother trying the 5mm. All I would say here is that although the BSTs were clearly very good, somehow I was left with the impression that the MVs (both of them) were that bit more crisp and contrasty. I'd like a few more sessions to verify that, though.

By now the frost was descending - the front glass of the finderscope particularly had iced up, although I could still use it on brighter stars to initiate a star-hop. Still, I thought it might be time for a break. I was hoping the skies might be clearer later on, and some more targets higher in the sky.

A good hour later, and the Pleiades were now out from behind the same tree that swallowed Orion earlier in the evening. (I hide from neighbour's lights behind it normally, but on this occasion I was in such a rush to set up that I accidentally placed the scope rather closer to it than usual.) M45 was an important test for me, because for all the beautiful sights in the night sky, I still think there are few that rival the Seven Sisters for breathtaking beauty. And I'd been disappointed with the basic SW 25mm eyepiece because, amongst other issues, it couldn't quite show me the whole cluster in all its glory - a wider field low-power eyepiece was essential! And that's really why I wanted the 24mm MaxVision to be a keeper - if not I'd have to find something else, and maybe even a 2" option, which I had hoped to avoid for now.

Well, having lined up the scope on the target I was perplexed - I didn't even recognise the cluster I was looking at. I thought somehow I must have aimed at something else entirely. Then I realised it - the MV was so much clearer and more contrasty than the stock 25mm that I was seeing many more stars than I was used to, and the brighter ones no longer stood out so much. As for the astigmatism - well I presume it must still have been there, but I really didn't even stop to think about it, because I was lost in the process of spotting stars I'd never even noticed before. I guess that's a box successfully ticked.

Jupiter was up above 40 degrees by the time I went back to it, and a good deal better placed. Now the StarGuiders really shone - I couldn't separate the 12mm and 8mm on their performance, except to say that the seeing was now good enough to easily support the 125x of the 8mm eyepiece so that was the clear winner. I was definitely having the best views of Jupiter I've ever had - beautiful! Of course I tried the 5mm too, but I really think conditions were still not good enough for that much magnification - and much more experienced observers than I am do seem to agree that Jupiter is at its best with rather less than the 200x that the 5mm gave, so who was I to argue? 

Finally - because frost on the secondary mirror brought an end to my efforts at around midnight - I took a look at the Perseus Double Cluster - always a favourite. And this was where those star colours really started leaping out at me - both of the MVs were good, but it was the 16mm that really framed the pair beautifully. I tried all the BSTs here too, but once again I was left feeling that the MVs were just that bit crisper. I'm wondering if it could just be the general consequence of trying to pull more and more magnification off an 8" mirror though. Certainly it's something I'd like to check further.

So, overall it was good within the limitations of the conditions - the sky-glow was too much for the 24mm, realistically, and the seeing not good enough for the 5mm. But everything else was good. The prize for the best view of the evening was a split decision between the 16mm MaxVision on the Double Cluster, and the 8mm StarGuider on Jupiter - both an absolute delight!
 

[John]

A very interesting and thorough report Huw - thanks for posting it

[alan potts]

A very nice report Huw and I hope better evenings will come your way.

Just talking on the point of coma, seagulls is maybe a better way of saying it on clusters . The problem is none of my scopes suffer coma and although I have seen it, it was in a 12.5 Newtonian scope back in 1977. I would have said that me calling Vega comalike was about right. Hopefully in the next few days I will have my new scope which at F4.3    will show coma and I can remind myself what it really looks like, though after that a Paracorr will be employed as I think it may annoy me.

As for the BST's there are few scopes I have ever seen where 8mm and 5mm will not give a high magnification, the latter in my shortest ups the power to around X160 so even on  a smaller refractor it will still be around X100, I know I am a few miles away but I have only seen a very few nights where X160 cannot be used and BST's seem to have a good following.

Thanks for posting the report

Alan.  

[happy-kat]

That would be my collection to if I were to build it differently, enjoyed the read. I am another fan of the MV 16mm.

[John]

A useful observers guide to the abberations, with pictures !:

http://www.umich.edu/~lowbrows/reflections/2007/dscobel.27.html

For me:

Coma = tadpole / comet shaped stars with the "tails" pointing away from the center of the field of view.

Astigmatism = "seagulls" with their "wings" seeming to wrap around the central axis of the field.

Each will increase in extent towards the edge of the field of view. Sometimes you can see a combination of both abberations plus some others. It's not always easy to decide what it is you are seeing !

Coma is generally produced by a fast newtonian rather than the eyepiece.

Astigmatism is generally produced by the eyepiece.

There are occasionally exceptions to the above though.

[hgjevans]

To be fair, looking now at the example images in the web page John linked to, I'd have to say that the effect I was seeing was probably about mid-way between the astigmatism and coma images - sharp 'wings' but swept somewhat towards the outer field - not radial as in the coma picture. I really want to investigate this eyepiece rather more before I'll feel really sure about what it's actually doing. I dare say I'll live with it happily enough for it's intended purpose of observing, but my scientific curiosity is piqued now.

Sadly I don't have some massive f/3 'Dobzilla' handy to throw a real challenge at it, but I have an f/2.8 300mm photographic lens - I might try jury-rigging it behind that just to see what I can glean there.

[Paul73]

Good report Huw

I also have an f4.7 scope. Chasing the perfect image is an expensive pastime.

The 24mm MV is probably my most used eyepiece. Yes, there are some misshapen stars as you go to the edges, but do you actually notice them during normal viewing? I love the contrast and natural view that this eyepiece gives and don't feel the need to plug in the Paracorr which should sort a lot of these artefacts.

Paul

[alan potts]

Paul

A Paracorr will only remove coma, not the astigmatism but your absolutely correct about chasing the perfect image, my wallet has stopped talking to me .

Alan

[hgjevans]

 Yes, there are some misshapen stars as you go to the edges, but do you actually notice them during normal viewing?

An absolutely fair point. And truth to tell, my lasting impression of the 24mm MV (just on the basis of that one evening, admittedly) was not seeing its faults on M37, but of forgetting to even look for them while I was counting Pleiades - that was my 'wow moment' for that eyepiece. I'm sure the time will come when I'll want better performance, but for the meantime I'm probably in that happy place where I'm easily - and cheaply - satisfied.   

[bingevader]

Well done Huw, good report.

I'm sure a follow up report on a better evening would be appreciated.

I know we tend to be quite nit-picky about the MVs because they're supposedly Meade cast-offs, but then you just stop to think of the performance the 24mm EP is delivering for £60!

[hgjevans]

Thank you Ben - yes I would definitely like to report again when I feel I've given all of the eyepieces a fairer chance to show their stuff.

And as for the cost of the MV - yes, knowing how much optical glass types can cost, and how much work goes into finishing them, and then again the basic mechanical engineering of these eyepieces, it's immediately obvious that you're getting an awful lot for your money.