April 19, 2016: Science! and Vixen!

As I posted a few weeks ago here, I questioned the recent discovery of gravitational waves.  Oh, not in the sense that I was questioning whether there was anything incorrect about their discovery, whatsoever – I remain as certain as certain can be that the data is entirely correct, and that they have discovered them.

No, I questioned the method of the checking to see whether the discovery was correct.  It appeared to me, a member of the general public, that the checking of the discovery was done behind closed doors, namely, behind the closed doors of the LIGO project.  As I mentioned in the previous blog post, there was a speaker at NEAF, David Shoemaker of MIT, Director of LIGO, who gave a fascinating talk on the subject, most of which you can watch at Youtube.

Also present at NEAF discussing gravitational waves as well were some scientists from Montclair State University, who were in a booth on the floor of the Fieldhouse .  (I remember that they had a booth at last year’s NEAF too, but before the discovery, I didn’t quite “get” the importance of gravitational waves at that time.)  I spoke with one of them, Marc Favata.  I thought Marc was just some young snot-nosed kid, but it turns out he is actually Dr. Marc Favata, Ph.D., and a member of the LIGO project.  We spoke about the concerns I raised in my other blog post.

He literally gave me some inside information.  First of all, he told me that the discovery was in fact submitted for peer-review to scientific journals before it was announced.  Marc explained that because of a premature announcement of the discovery of gravitational waves the last time around had turned out to be incorrect, this time, the submission was given to a referee for a “secret” review.  It was decided to make this submission on the down low, although in this case, word of the discovery was prematurely leaked by noted popular astronomer Lawrence Krauss before the big announcement.  But “secret” reviews such as this are not uncommon.

He also explained that, no, everyone isn’t already in LIGO, or that everyone worth their salt was already in LIGO either, although literally a thousand scientists are.  So, yes, while those thousand scientists did review the discovery internally, there are also separate gravitational detection teams in Europe and in Japan who are unaffiliated with LIGO, and scientists on those teams would have been among those reviewing and checking the LIGO data for errors.  When the announcement of the discovery was made in February, the discovery had already been peer-reviewed, and the scientific journal thereafter published the data and the results.

This tied in to what David Shoemaker said in his LIGO talk:  as a check on the people reviewing the data, they often introduce false data into the detection process to keep the detection team on its toes, so as to be able to weed out false positives.  When the discovery was made only 2 days after turning the detector back on again after its refit to increase its sensitivity, there was a lot of checking around at LIGO to make sure that no one had introduced the positive but false data into the data stream.  Obviously, no one had done so.

However, Marc did acknowledge that those days of there being separate teams would fast be coming to an end, due to the nature of the detection of gravitational waves.  This is because more detectors significantly increase the accuracy of the data.  All the teams will soon be collaborating together.  He acknowledged that eventually, everyone will be on the same LIGO team.

Indeed, although something similar could be said of the discovery of the Higgs Boson, that there was no one outside of the teams involved at CERN, Marc stressed the point that within CERN there were separate experiments, separate detectors, laid out along the miles of tubes, and most importantly, separate teams.  We tend to think of the Large Hadron Collider as being just one massively long particle accelerator, but there are actually different detectors within it, and with that, different teams analyzing different data streams produced by different experiments.  All of these teams reached the same conclusion that the Higgs had been discovered with their own data.

Marc predicted that, just as with the discovery of the Higgs Boson, the Nobel Prize for gravitational waves will be awarded within the next year or two, and that Kip Thorne would be one of the recipients.

Based on my discussion with Marc, although the concerns that I raised in my earlier “Science?” post have not yet come to fruition, they will, and soon.

 


 

While at NEAF, one particular scope really caught my eye.

20160409_111841

Well, of course, those enormous binoscopes would catch anyone’s eye.  But if you look in the lower right hand corner, you’ll see a scope I had long been wondering about, the Vixen VMC 200L.  This scope briefly caught my eye a year and a half ago when I was casting about for an alternative to the 8″ dob that I figured out I would have to collimate from time-to-time – and thus abandoned in terms of purchasing.  This Vixen is an 8″ catadioptric cassegrain, but with a twist.  It is a sub-aperture Maksutov as well.  That means there is a small meniscus just below the secondary, so that the light from the mirror passes through it twice; this design is known as a “Field Maksutov”.

This blog is about observing from light-polluted skies.  And yes, I have bagged over 40 Messier objects and well over 100 NGCs from here.  But for most of the objects, I’ve only “seen” them rather than “observed” them.  Globular clusters are just a bit more than a round haze of stars, and galaxies are indistinguishable faint fuzzies, while nebulae are almost completely washed out.  The theoretical limiting magnitude of my 5-inch Mak (operating at 120mm because of an undersized primary) is about 12.4; in practical terms, because I am observing here in the light-polluted skies of Manhattan, that means I can only get down to about 3 magnitudes dimmer, around 9.5 or so.

Going larger would obviously allow me to go deeper, both in terms of seeing more, and in terms of seeing what I can already see that much better.  Up until this point, I had been trying to satisfy my aperture fever by focusing my next telescope lusting energies on the Skywatcher 180mm Mak:

sw180
Rear view.  Note the two-inch diagonal and eyepiece.

This is regular a 180mm Mak, made by Synta, just like all the other Maks.  Orion also sells a version of this, but Skywatcher sells it equipped with a two-inch back, diagonal, and eyepiece.  The Orion version has a 1.25″ back, so that it can only make use of 1.25″ accessories.  Also, the SW version is $1275, while the Orion comes with nothing and is usually priced higher (although right now it’s priced at $1199 for the bare OTA).

Like my 127 Mak, due to an undersized mirror, the 180 Mak operates at around 170mm. (EDIT – I have since “learned” from someone posting at Cloudy Nights who has measured it, that the primary is not undersized – that it is 190 or 193mm or something.) That would let my theoretical limiting magnitude go down from 12.4 to 13.2, which would be nice.  An 8″ scope, like the Vixen, would give me an extra 1.2″ of aperture over that 170mm, and would let me go 1/3 of a magnitude deeper, to 13.5 – and more than a full magnitude deeper than I can currently go.  10th magnitude stars would come into view.  Globular clusters would show as individual stars.  I’d see more structure in nebulae.

As opposed to the 180 Mak, I had been considering moving up to a regular old C8 SCT instead.  But SCTs always seem to scream out to me that they are “optically inferior!” as they try to be everything to everyone.  SCTs are commonly described as being a “jack of all trades”.  But the second part of that aphorism is “master of none”.  I mean, why is there a need for the existence of the very expensive Edge HD line of SCTs, if the non-Edge HDs are all that great to begin with, y’know?  (And yes, I know that it’s because the Edge HD line is designed for use in AP, but still.)

Vixen is a well-respected Japanese telescope manufacturer and vendor.  The fact that Vixen does both roles is important, because of the main vendors, Celestron, Orion, Skywatcher, Meade, and Explore Scientific, none of them manufacture their own equipment any longer.  Their stuff is all made by Chinese companies:  Synta for the first three, Sunny for Meade, and JOC for ES.  Vixen still manufactures its own equipment in its own factory; and that ties in to what the Vixen salesman told me at NEAF – that Vixen does 100% quality control, inspecting every scope.  Vixen has been celebrated as a refractor-maker, particularly apos, but about 10 or so years ago, decided to dip its feet into the catadioptric world with the VMC 200L model, as well as a few other cassegrains of various apertures.

The Vixen salesman admitted that while this VMC isn’t quite the equal of a regular Mak, it beats an SCT.  Its open-tube design means faster cooldown times, and its rack-and-pinion focuser means that there is no mirror shift.  No big meniscus means no dew. Finally, he said that the scope maintains collimation for a very long time.  That last bit was music to my ears.  As long-time readers of this blog know, I am collimation-phobic, and thus the reason why I’m interested in Maks and ‘fracs.  Here’s the studio glamour shot of the 200L as well as the light path diagram, where you can see the meniscus right behind (as well as ahead of) the secondary:

Vixen_VMC200Lvmc200l_diagram

In researching the Vixen since returning from NEAF, it seems like the claim of besting an SCT might not hold water.  A number of people have complained that the very (very!) thick spider vanes along with with the very large obstruction of the secondary – 40%! – combine to rob the scope of contrast on planets.  Take a look at the front end and see:

vixen spider

To me, those spider vanes scream out “sturdiness!” such that there would never be any need to collimate the secondary.  However, those are some mighty thick vanes, and that secondary obstruction is indeed very large, so that I have to accept that the contrast-robbing effects must be real.  Since my purpose in getting this scope would be to use it to go a full magnitude deeper than my 127 Mak to get some better looks at DSOs, this problem may not really concern me.  I’d still have my Mak, which is terrific on planets.

As I see it, the pros of the 200L vs. the 180 Mak are:

200L pros:

1. Lighter: 13 lbs. vs. 16 lbs., and easier to handle with its built-in handle;
2. Cheaper: $900 vs. $1275;
3. More aperture: 200mm vs. ~170mm = 1/3 magnitude deeper;
4. Better focus: Crayford vs. moving mirror, so no mirror shift, and snap to focus;
5. Better 2″ capabilities – fully illuminated to the edge of field, so no vignetting;
6. Shorter focal length of 1950mm vs. 2700mm = wider field: 1.35 vs. 1.05 degrees;
7. No dew issues (which isn’t a problem for me in Manhattan anyway);
8. Open tube means faster cooldown than a Mak.

180 Mak pros:

1. It’s a real Mak = better optics, and that much sharper of an image;
2. Smaller central obstruction = better contrast;
3. No spider = no diffraction spikes;
4. No collimation issues vs. possibly, maybe some for the 200L?

In reading up on the scope at Cloudy Nights, some have mentioned that they did have to collimate the scope.  While my collimation-phobia remains strong, it has been weakening of late.  This is because I understand that collimating this scope is actually very simple.  With those thick spider vanes, the secondary is relatively stable, so it’s only the primary you’re adjusting.  You find a bright star, defocus it so you can see the shadow of the secondary inside a donut of light, and check to see that the shadow is precisely centered.  If it’s off center, then you just pick the primary screw on the back that’s closest to where it’s off and move it with an allen wrench one way or the other to move it until it’s centered again.

I will have to research it further, but it seems like a Japanese firm like Vixen, with over 80 years of optical experience, would know what they’re doing when they both design and manufacture a scope like this such that it would at least be pretty good optically, if not better than pretty good.

Regardless, “professional” reviews, like this one from Astronomy Technology Today from 8 years ago, and this one at Astromart from 10 years ago, give the scope an unqualified thumbs up.  Some old reviews at Excelsis are of exactly the same tenor.  And they all seem to be in agreement that the scope bests an SCT, as the scope is essentially just a Mak with its meniscus repositioned.  (And if it sounds like I’m trying to convince myself that this scope is better, you’re right.)  So it looks like the object of my aperture fever and scope lust may be getting transferred to another scope.

 

Next time:  5th Moon of Jupiter?  42nd Messier; and A New Season of Outreach

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2 thoughts on “April 19, 2016: Science! and Vixen!

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