Archive for the ‘Observatories’ Category

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Kickstarter – the Great Lick Refractor

February 25, 2017

I have been very fortunate in getting to visit the Lick Observatory three times, and to look through the Great Lick Refractor (36″/914mm aperture, f/19) on two different occasions. On the second visit I even got a quick afocal snap of Saturn through this wonderful, 129-year-old instrument. Those stories and accompanying photos are on Cloudy Nights, here.

I bring this up because there’s a Kickstarter going on right now to sponsor a couple of experienced astrophotographers to use the Great Lick Refractor for one night (or maybe two, if they enough funding), and backers get copies of their pictures. The project will be funded – they’re already well over the target goal of $6500 and closing in on the $9000 they’ll need for a second night – so there’s no real risk here. I pounced as soon as I heard about it. If you’re interested, click on one of the links above and check it out.

This project will be funded on Monday, March 20, 2017, at 7:17 PM PDT.

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Impromptu binocular digiscoping

January 18, 2017

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I grew up in Oklahoma, on the Great Plains. The plains have a wild, forlorn beauty, but I have always craved seeing mountains. When I was a kid, that meant waiting for a family vacation to the Rockies or the Black Hills of South Dakota. I have been very fortunate that since moving to California in 2001, I have essentially always lived within view of mountains. In Santa Cruz and Berkeley it was the coast ranges, which are really more like ambitious hills. In Merced it was the Sierra Nevadas, which are legit, but not particularly close to Merced. The mountains were only visible as a low line on the eastern horizon, and only when the air quality was good, which was not often. Fortunately that was just one year.

Since 2008, I’ve had the privilege of living at the feet of the San Gabriels and especially Mount Baldy (formally Mount San Antonio, but universally ‘Baldy’ to locals), which looms directly north of Claremont like a slumbering god. So I get to see proper mountains – the San Gabriels are still rising fast so they are impressively steep, and Baldy tops out at 10,064 feet (3068 m) – pretty much every day that it’s not raining and there are no nearby wildfires. In the winter the mountains are often snowcapped, although never continuously so, it’s just too warm here.

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A couple of days ago I was out running errands and the mountains looked so good that I had to drive up to the top of the First Street parking garage downtown to get some unobstructed photos. Off to the northwest, 22 miles distant, I could just make out the gleaming white domes on Mount Wilson. Then I remembered that I had my 10×50 binos in the car, so I got them out and spent a few pleasant minutes scanning the whole northern skyline, from Mount Wilson in the west to mount San Gorgonio, above Big Bear, 51 miles due east.

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Then I got to wondering – if I held my iPhone up to the binos, would I be able to get a recognizable photo of Mount Wilson? It was worth a try. I had to prop the binos on my sunglasses to get the angle right, and the raw shot is vignetted because getting the camera-to-eyepiece distance correct is a little hairy, but hey, there are the domes.

mt-wilson-from-claremont

Here’s a cropped, tweaked, and labeled shot. Except for the CHARA Array, an optical interferometer using six 1-meter telescopes in small domes that started work in 2002, all of the historically important installations are visible from 22 miles out.

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I also got some shots of the nearby peaks, especially the higher foothills of Mount Baldy. This shot is a pretty good match for the last photo in this post, which was taken through a different instrument at a different time of day in a different season, but focused on the same peak. This peak is 10.5 miles from my house, as the crow flies, so about 10.25 miles from the Claremont parking garage where the photos in this post were taken.

snowy-trees-on-mt-baldy-foothills

Cropped and tweaked. Not too bad for 10×50 binos that cost less than $30.

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Mt Wilson photo tour and a brief observing report

June 5, 2016

Mt Wilson 1 - Geo on the 60-inch

Last night the PVAA had the 60-inch telescope booked at Mt Wilson. It had been ages since I’d been up there – my only other trips up were in 2009 and 2010 (observing reports here and here). So it was very satisfying to be back. It is amazing to look back and realize that in 2010 I was only 3 years into what has now been almost 9 years of stargazing.

The last two times I went up, we didn’t have time for a tour of the grounds, so about all I saw were the parking area, the 60-inch dome, and a few odds and ends in the distance. This time we got a nice long tour from Geo Somoza – most of the rest of this post is a photographic tour of part of the observatory. We didn’t have time to go through the museum up there, or see the solar telescopes – guess I’ll just have to go back again to catch those (which is no bad thing!).

I rode up with Ron Hoekwater, Laura Jaoui, and Gary Thompson, who kindly drove us. We left Claremont early and got up there about 6:00, well in advance of the planned 6:30 start time for the tour. While we were chatting outside the gate, we saw something ominous: a tower of smoke going up from the mountains to the west. This would come back to haunt us.

Mt Wilson 2 - Einstein bridge and the 100-inch

Here’s the dome of the 100-inch Hooker telescope – world’s largest from 1917, when it eclipsed the 60-inch telescope on the same mountain, until 1948, when it was eclipsed in turn by the 200-inch Hale telescope on Palomar Mountain. It is a bit staggering to realize that from 1908 to 1993, when Keck 1 went online on Mauna Kea, the three consecutive world’s largest fully-functional telescopes were all within 92 miles of each other in southern California. (The 240-inch Soviet BTA-6 saw first light in 1976, but it suffered terrible thermal stability and seeing problems and never performed anywhere near its full potential.)

This bridge is nicknamed “Einstein’s bridge” because Einstein paused here for a famous photograph during a visit to Mt Wilson in 1931 – see that historical photograph here.

Mt Wilson 3 - the 100-inch

Here’s the scope itself, the same machine that Edwin Hubble and Milton Humason – a former mule-driver who worked his way up to master observer – used to chart the expansion of the universe. I was scheduled to go up and observe with the 100-inch last year, but I got very sick the day before and couldn’t make it. So that is still on the bucket list.

Mt Wilson 4 - the 100-inch mirror

A view into the back of the mirror cell of the 100-inch telescope. The green champagne-bottle glass of the primary mirror is clearly visible. If you click through to the full-size version you may be able to see bubbles in the glass. The 14-inch-thick mirror had to be made in three separate ‘pours’ of molten glass, and bubbles from the first two pours were trapped by the layer above. The people at Mt Wilson were so concerned about the bubbles interrupting the figure of the mirror that at first they refused to work with it, but St Grobain Glassworks was unable to pour a better one and eventually George Ellery Hale ordered his people to grind and polish this mirror, which turned out to be fine at the optical surface after all.

Mt Wilson 5 - 100-inch eyepiece

In the old days, to observe visually with the 100-inch you had to go down a narrow hallway to a tiny room where light from the scope was bounced to the Coude focus. That was pretty unsatisfying so a few years ago the telescope was modified for more intimate visual observing. Now the primary mirror at the bottom of the scope bounces the light to a secondary up in the upper cage, thence to a tertiary at mid-tube which directs the light out to a quaternary mirror in the diagonal housing at the top of the black tubular assembly on the left of the scope in the above photo, thence down to a quinary mirror at the bottom of the black tube, then into the white refractor that is pointing down and to the right. A diagonal sitting nearby can be placed into the refractor to put the eyepiece into a convenient orientation when the scope is tilted.

Mt Wilson 6 - 100-inch controls

The control board of the 100-inch, with at least three separate control systems lined up right to left in order of age. Most interesting is the old table on the right with the clock and the two periscopes. The periscopes allowed the telescope operator to see the telescope’s setting circles. Nowadays, the scope is controlled by the computers on the left.

Mt Wilson 7 - 100-inch dome

Excited amateur astronomers lingering outside the dome of the 100-inch. We got to walk around on the walkway you can see on the outside of the dome. The entire dome rotates, walkway included. It’s a fearsome engine indeed.

Mt Wilson 8 - CHARA array and 60-inch domes

On the left is one of the six domes of the CHARA array, I believe still the world’s longest-baseline optical interferometer. It has enough resolving power to image the discs of nearby stars. On the right is the 60-inch dome.

Mt Wilson 9 - lightspeed test site

Geo shows us the concrete pier used during the speed-of-light experiments in the 1920s. More on those in a sec.

Mt Wilson 10 - lightspeed test plaque

For decades in the late 1800s and early 1900s, Albert Michelson conducted a series of experiments to measure the speed of light. In a series of famous tests in the 1920s – almost two decades after Michelson earned his Nobel Prize – a beam of light was bounced from this pier on Mt Wilson to a mirror on Lookout Mountain, one of the foothills of Mt San Antonio, better known to locals as Mt Baldy – the mountain at whose base I live. The concrete pier on Lookout Mountain is still there and it is apparently an easy hike. It’s on my to-do list.

Mt Wilson 11 - LA and smoke from wildfire

Sunset over LA. On the left, the marine layer of fog is moving in over the city. On the right, a tower of smoke is going up from a wildfire near Calabasas, about 40 miles to the south and west of Mt Wilson, and spreading out over the LA basin. For a while the smoke was going southeast from the fire, and it looked like it might miss us. But by the time it was getting dark, the wind had shifted and was carrying the smoke directly toward the observatory.

Mt Wilson 12 - going up to the 60-inch

As darkness fell, we trooped into the dome of the 60-inch telescope.

Mt Wilson 13 - Edison bulbs

Here are the controls for the dome’s shutter, which has to be opened for the telescope to see out, and closed again to protect the telescope during the daytime and in inclement conditions. The three light bulbs on the upper left of the console are original Edison bulbs – they have been working without ever being replaced since 1907 or so.

Mt Wilson 14 - control board and mercury tank

Our telescope operator, Christopher Burns, checks something on one of the computers in the control center, while beyond him Geo stands by the mercury tank in which the 60-inch telescope floats. Don’t worry, it’s fully sealed now. In the old days, it was open, and mercury would sometimes splash on the floor as the telescope rotated.

Mt Wilson 16 - Jupiter with blue filter

Our first target was Jupiter. As usual, the photo completely fails to do justice to the naked-eye view. The seeing was imperfect and I think the smoke from the fire might already have been affecting the views. The north and south equatorial and temperate belts were visible, and the Great Red Spot was prominent, but I could see little detail beyond that. I have seen much better on other visits, and indeed in much smaller scopes (see for example the two previous Mt Wilson observing reports linked at the top of this post). But I won’t complain too much – part of the joy of observing with the 60-inch is in the process, not the outcome.

Mt Wilson 15 - 60-inch lit by laser

After Jupiter we moved on to the globular cluster M3, and then the Sombrero Galaxy, M104. M3 was already looking a bit dim – certainly not as bright as it appeared in Ron’s 25-inch scope from RTMC last weekend – and about this time the smell of smoke became pronounced in the dome. We had a hurried look at M104, but it was just a dim smudge of light and I couldn’t even make out the dust lane.

After M104 we had to shut down early to protect the telescope. If ash from the fire was allowed to fall on the mirrors, it would combine with moisture in the air to produce acids which would eat away the coatings. In the photo above, Geo is shining a laser up through the optical train to check for ash on the mirrors.

Mt Wilson 17 - Matt with the telescope

It was a bummer to have to shut down early, but we had an awesome tour and it was fun to observe again with the 60-inch, even if only briefly. Geo and Chris were great hosts and everyone had a good time. We’ll get to reschedule our night on the scope, since we only got about an hour and a half of observing in, so the club’s investment is protected. It’s a shame about Mars, though – we won’t have another opposition this close for some time, and the planet will be noticeably more distant, smaller, and dimmer by next month already. Still, into every observing career a little rain – or ash – must fall, and I’ve been extremely fortunate. Two eclipses (2012, 2014), a Venus transit, and a Mercury transit in the last four years, and not one of them clouded out. Mars will be back, and I’ll be ready.

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A tour of Big Bear Solar Observatory

October 13, 2015

BBSO from up high

The gleaming white domes of the Big Bear Solar Observatory sit at the end of a causeway that projects from the north shore of Big Bear Lake – they draw the eye from almost any point in Big Bear Valley. And as I mentioned in my last post, the Pomona Valley Amateur Astronomers got to visit the BBSO on Friday, October 9.

BBSO causeway

We were greeted at the gate by Claude Plymate, Chief Observer and Telescope Engineer at BBSO, and Teresa Bippert-Plymate, who is not only a professional solar astronomer but also the president of the Big Bear Valley Astronomical Society. As pros who are also enthusiastic amateur observers, Claude and Teresa did a great job of pitching the tour with just the right balance of necessary background, technical detail, and the hands-on practicality of managing big scopes and the complicated hardware and software necessary to run them.

BBSO GONG scope

The first thing you come to on the causeway is a big white storage container with a coelostat (sun-tracking mirror) – this is one of the six Global Oscillations Network Group (GONG) installations spaced roughly equally around the world. The GONG telescopes track the sun around the clock for helioseismology research, mapping the acoustic pressure waves that propagate around and through the sun.

PVAA group outside BBSO domes

The smaller dome just short of the end of the causeway holds two telescopes on a common mount. One is a 10cm full-disc hydrogen-alpha solar telescope, the other is a second smallish refractor for Project Earthshine, which tracks the Earth’s albedo by measuring the intensity of the earthshine that falls on the moon’s unlit side.

London with BBSO New Solar Telescope

The observatory’s ‘big gun’ is the 1.6-meter New Solar Telescope, an off-axis Gregorian. One-point-six meters is 63 inches, which means this scope has a slightly larger aperture than the famous 60-inch reflector on Mount Wilson (which I’ve been fortunate to visit – see here and here). Here’s the light path of the NST (an unmodified version of this image is at the bottom of the post):

BBSO New Solar Telescope light path

And here’s a view on the right side of the scope showing the mask that rejects the light from most of the sun (which bounces onto the back wall of the dome, landing at about the same intensity as natural sunlight). The mask has a small hole which allows light from a small part of the sun to pass through to the chain of lenses and mirrors that bounce the beam to the research instruments on the next floor down.

BBSO New Solar Telescope right side optics

It took me a while to wrap my head around how this works. If the mask rejects most of the sun’s light, doesn’t that mean that most of the telescope’s 1.6-meter aperture is wasted? The answer is no – the mask functions as a field stop, not an aperture stop. If I put a mask across the front of my 10″ Dob and let only a 4″ beam of light through, that’s an aperture stop – it effectively turns a 10″ f/4.7 obstructed system into a 4″ f/12 unobstructed system (which may be desirable for sharp planetary and lunar views, where light-gathering is not so important). But imagine I left the front of the scope uncovered and instead masked down the field stop at the bottom of one of my eyepieces, so that I could only see a tiny hole in the center. If I put the scope on Jupiter, I’d see Jupiter in the center of the field but nothing else – I’d be getting the full benefit of the 10″ mirror’s light-gathering and resolution on Jupiter, but rejecting the light from the surrounding starfield, which would reflect off the mask at the bottom of the eyepiece. That’s more or less what happens with the New Solar Telescope, only “the rest of the field” is the rest of the sun, and the small area that the scope focuses on is not a planet but a small patch of the sun’s surface. But that patch can be imaged with the full benefit of the 1.6-meter primary mirror’s angular resolution.

BBSO burnt light shield

Now, a 1.6-meter mirror focusing the light from the full disc of the sun onto an area about 3cm across is a hell of a lot of energy. That beam could fry electronics, melt metal, and start fires if it got off-course. There are multiple redundant systems to prevent that from happening – the dome can close, the primary mirror has a cover that can activate quickly, and if all else fails a 1/16″ steel plate slides into position in front of the field stop. A few years ago – before Claude’s tenure as Chief Observer! – there were not so many safeguards in place. The software that allows the telescope to track the sun briefly got confused by some passing clouds, and the scope stopped tracking properly. That allowed the concentrated beam of sunlight to slide off-target. The steel plate did its job and slid into place, and the scope melted two holes in it in the space of about 30 seconds. The folks at the observatory keep the melted metal plate as a visible reminder that they are in a very real sense playing with fire.

BBSO sunspot image

This sunspot is a bit larger than our planet.

Our last stop on the tour was the telescope control room, where another professional astronomer was driving the scope and taking data. There was a minor mechanical hiccup at one point and Claude had to swing into action, running back and forth from the control room to the instrument room to get everything back on track. It was amazing to see live images coming in in real time. I’ve been fortunate to tour a lot of observatories but never while they were working. At one point Claude and the other astronomer put the scope on a sunspot group which was just swimming in atmospheric distortion. Once the computer had enough data to engage the adaptive optics, they switched on the AO and the view instantly settled down to nearly rock-solid, like it was painted on the monitor.

BBSO New Solar Telescope

The NST is currently the largest, best-equipped solar telescope in the history of humankind, and it is producing the sharpest images of the sun ever taken. BBSO joins Mount Wilson and Palomar in continuing the long, proud history of world-class astronomy in southern California. And it’s 65 miles from my house. Many thanks to Claude and Teresa for being such gracious hosts and letting us see their beautiful machines in action.

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Another visit to the Palomar Observatory

November 28, 2014

Palomar 2014 - London with the dome 1

London had the whole Thanksgiving week out of school, so I took some vacation days to spend it with him. On Monay we went to Anza-Borrego Desert State Park to camp and observe – more on that in the next post. We’d never been there before, and in planning our route I noticed that we’d go pretty close to Palomar Mountain. I asked London if he’d like to visit the observatory again, and he jumped at the chance. Our only previous visit, in September of 2012, had left a big impression on him.

Palomar 2014 - 18-inch model

The visitor’s center had gotten a major upgrade to its exhibits in the intervening two years. Out in the entrance lobby, a small display case showed this model and photo of the 18-inch Schmidt camera, which was the first operational telescope on Palomar Mountain. It entered service in 1936, a full 12 years before the 200-inch Hale telescope first opened its shutters in 1948. The 18-inch Schmidt had a long run – Carolyn and Eugene Shoemaker and David Levy were using it in 1993 to find and catalog near-Earth objects when they accidentally discovered Comet Shoemaker-Levy 9.

Palomar 2014 - 18-inch front

The 18-inch Schmidt has since been retired, and now it’s on display in the visitor center. This is a huge upgrade to the exhibits there – when we visited in 2012, all there was to see were the lighted plates along the walls of the room. Now the 18-inch Schmidt sits in a plexiglass island that is surrounded on all sides with photographs, signage, a touch-screen that shows short movies about the history of the observatory, and display cases with equipment used to operate the camera, including the hand-operated press that punched 6-inch circles of film.

Palomar 2014 - 18-inch back

Here’s the back end of the scope. As you can see, it has no eyepiece and no provision for one. Where an amateur Schmidt-Cassegrain telescope has its secondary mirror, the Schmidt camera had a piece of film (and maybe later a CCD?). On top is what looks to be a 6- or possibly 8-inch guidescope, which does have an eyepiece. Until the advent of computerized autoguiders, taking long-exposure photographs meant that an astronomer had to sit at the guidescope for hours, keeping the crosshairs centered on a guide star and tweaking the alignment of the telescope by hand. Sounds thrilling, eh? I wonder how much more productive professional astronomers are as a group, now that they don’t have to spend so many hours guiding telescopes.

Palomar 2014 - Hale dome with book

But of course the real attraction at Palomar Observatory is the 200-inch Hale telescope, which was the world’s largest fully-operational telescope for almost half a century. Astronomy books from before the early 90s talk about the Hale telescope in the same glowing tones reserved for the Hubble Space Telescope today. And for good reason – the 200-inch scope served roughly the same purpose as the HST and the twin Keck telescopes today. Until the space race of the following decades, the construction of the 200-inch telescope was probably the closest thing to a ‘megaproject’ in science and engineering. The story of how the telescope came to be is a decades-long saga of obsession, invention, science, engineering, and politics; if you’re interested in that story, I highly recommend The Perfect Machine: Building the Palomar Telescope by Ronald Florence. Here’s the 200-inch dome alongside its portrait from London’s Golden Book of Stars and Planets (1985 printing).

Palomar 2014 - London with Hale model

Famously, much of the design of the 200-inch scope came from the mind of amateur astronomer and amateur telescope maker Russell Porter, who built this scale model in the 1930s.

Palomar 2014 - Hale telescope

And here’s the scope itself. We didn’t get to go inside the dome and walk around the scope like we did last time. Those tours only run from April to October. But we were able to look in at the scope from an observation gallery.

Palomar 2014 - Hale concrete mirror blank

Outside the dome is this 200-inch concrete disk, which was used as a mass simulator to make sure the mechanical structure of the telescope worked before the actual mirror was installed. The mass blank has apparently been sitting out in the elements, right across the road from the dome, since 1948. It looks little worse for the wear, and it gives visitors a visceral sense of just how big a 200-inch mirror actually is.

Palomar 2014 - London with the dome 2

One last shot from this visit: London just off the path that leads from the visitor center to the dome. I had to take this one to replicate the picture below, from our last visit in 2012. It’s part of what is apparently now an ongoing series of pictures of London at different ages in front of the same telescope – see him with a replica of Galileo’s telescope here.

London at Palomar Mountain

Next up: crazy-dark skies at Anza-Borrego. Stay tuned.

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A visit to the Griffith Observatory

November 2, 2014

2014-11-01 Griffith Park 1 - the observatory

Yesterday London and I went to the Griffith Observatory for the first time in a while. We used to go fairly frequently between 2010 and 2012, but this was our first visit in 2014 and might have been our first visit since 2012.

2014-11-01 Griffith Park 3 - moon over the observatory

It had been rainy earlier in the day but the skies opened up nicely in the late afternoon, and the waxing gibbous moon was bright overhead.

2014-11-01 Griffith Park sunset 2 - snapseed

Happily there were still some clouds to the west and north, which made for a fantastic sunset.

2014-11-01 Griffith Park 5 - London with Galileo telescope

One of my favorite displays is the replica of Galileo’s ‘Old Discoverer’ in the Hall of the Eye. It is still amazing to me that Galileo saw and learned so much with a 1-inch objective mounted in a paper tube. London is blocking the objective end here, but I had to pose him there for a reason.

2009-11-01 Griffith Park - London with Galileo telescope

Here’s the same shot, five years earlier. London was not quite five years old, and he was very excited about being at the “Griffick Ugzerbatory”. I didn’t realize until I checked the dates on the photos that that first visit was not approximately five years earlier, it was exactly five years earlier, on the first of November, 2009.

2014-11-01 Griffith Park 4 - observatory model

Farther down the same hall, there is this miniature architectural model of the observatory. The three domes all house different things. The one on the west end of the roof, nearest the camera in this shot, holds the triple beam coelostat for live viewing of the sun. The huge middle dome holds the planetarium, and the dome on the east end holds the big 12-inch Zeiss refractor–you can even see a translucent miniature version of the scope in the model dome.

2014-11-01 Griffith Park Zeiss refractor 1

And here’s the 12-inch Zeiss itself. There are actually five scopes on the mount currently: the big Zeiss, f/16.7, at the center, a 9.5-inch f/14.8 Zeiss refractor piggybacked on top, a 2- or 3-inch finderscope on the lower left, and two 8-inch Celestron SCTs on either side.

Originally the mount only held the 12-inch and the finderscope–you can see photos of it mounted that way on this page, which has a very interesting history of the scope and its uses. The 9.5-inch was added in 1955. The double refractors allowed one scope to be used for visual observation while the image from the second was sent to a closed-circuit TV. That job is now farmed out to one of the Celestron SCTs, which are much more recent additions.

2014-11-01 Griffith Park Zeiss refractor 2

Here’s another view. The total moving mass of the rig is 9000 lbs, or 4.5 tons.

We have gotten to look through the big Zeiss a couple of times, but we didn’t do so last night. There is usually a line with a wait time of about an hour. The way to beat the system is to be on the roof and near the east end at the moment that they open the dome and the line first forms–we have been lucky to be in that position once before. But last night we were in the middle of a planetarium show when the dome opened at 7:00, and we didn’t fancy standing around in the cold for an hour. Especially because there was a public star party on the lawn in front of the observatory, with about half a dozen scopes set up. There were long lines for the big scopes, but one guy had a 90mm Mak on an EQ mount that everyone seemed to be ignoring. London and I got razor-sharp views of the moon through that little scope with no waiting at all.

2014-11-01 waxing gibbous moon - raw

At home I hauled out the C80ED and the 8-24x zoom eyepiece for a quick look myself, and to make another photographic attempt with the iPhone. The two biggest challenges are getting the camera the right distance from the eyepiece, and getting the sensor fully illuminated without being overexposed. Through much trial and error I found that if I left the eyepiece cup up and stripped off only the outer layer of my 3-layer Otterbox phone case, I could rest the second layer of the phone case on the rubber eyepiece cup and have the phone at just the right distance. But that only worked perfectly with the zoom set to 18mm (33x), which is how I took this shot. There is some CA, but I’m pretty sure that was mostly from the eyepiece. If it’s clear tonight, I’ll try again with the ES eyepieces to see if I can isolate the cause of the CA.

One thing I desperately need to do is get one of the iPhone apps that lets you control the ISO and shutter speed of the camera. As it is, I’m just using the camera as-is, so I’m constantly fighting with its auto-exposure and auto-shutter. There’s a delicate balance–if I don’t magnify the moon (or the filtered sun) enough, all I get is a featureless white spot. But if I magnify the subject enough to spread out the light and give the camera’s internal processes some detail to bite on, then it’s hard to get the object fully illuminated–I get vignetting, or kidney-bean blackouts, or both at once. Eric Teske has a nice list of iPhone astro apps on his (ridiculously entertaining) blog–past time I started using them.

2014-11-01 waxing gibbous moon - snapseed

Still, for a shot through an 80mm refractor with the came-bundled camera driver on my phone, I’m pretty happy. One thing I really like about the iPhone is the number and utility of photo-editing apps. The first moon image here is the raw shot, only reversed left-to-right to match the moon’s orientation in the sky. The one immediately above I processed in Snapseed: sharpened, contrast enhanced (using the ‘Ambiance’ tool), and desaturated to take out the CA. Given the relatively small number of GIMP features that I actually use, Snapseed is a fast and easy alternative. I’m going to keep messing with it and see how far I can go.

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Guest post: The “First” Great Telescope: the Great Dorpat Refractor in Tartu’s Old Observatory

October 1, 2012

Here’s another guest post by Terry Nakazono (his first is here). Enjoy!

(All pictures, except for the image of F.G.W. Struve, were taken by the author)

In a few posts (and one Cloudy Nights article), Matt made mention of getting his start in observational astronomy after a visit to Lick Observatory in San Jose, California and looking through the Great Lick Refractor.

The term “Great Refractor” refers to an achromatic refracting refractor that is the largest in a region, or in the world. When it was completed in 1888, the Lick refractor was the biggest (36-inch lens) in the world. Hence the term the “Great Lick Refractor”.Earlier in April this year, I made a visit to the Old Tartu Observatory in Tartu (Estonia), built between the years 1808-1810 and now a museum.

This observatory houses the first “Great Refractor” – the Great Dorpat Refractor (Dorpat is the old German name for Tartu), built by the noted German optician Joseph Fraunhofer in 1824 (also known as the Fraunhofer Refractor). This telescope was the forerunner of the Lick and other large refractors built in the 19th and 20th centuries.

This 9.6 inch (24cm) achromat with a focal ratio of 16.6 was the largest and best refractor in the world for many years. The lens had a light-gathering capacity equal to a reflector of that era having twice the aperture of this refractor. This was also the first telescope to use a German equatorial mount, with a precision clock drive that allowed objects to be tracked automatically.

The man who ordered this telescope from Fraunhofer was Friedrich Georg Wilhelm Struve, the director of the observatory from 1820-1839.

His most famous observations with this refractor included a massive survey of double stars (whereby he published two double star catalogs), the measurement of the parallax of Vega in 1837, measurements of the diameters of Jupiter’s 4 largest satellites in 1826 (which turned out to be the most accurate for the next century), and Halley’s comet in 1835, where he measured the dimensions of the tail and was able to see the nucleus of the comet. On the observatory grounds is a monument to Struve.

On display at the observatory are many other instruments used by Struve and others. One is the Dollond transit instrument (purchased in 1807), used to determine exact astronomical coordinates.

Another instrument used to measure the position of stars was the Reichenback-Ertel Meridian Circle (purchased in 1822).

The Troughton telescope (purchased in 1807) was a 3.5 inch achromat that was Struve’s main observational instrument before the Fraunhofer refractor.

But the most fascinating item on display (besides the Fraunhofer scope) is the Herschel 7-foot refractor, bought in 1806. Herschel made 200 of these 7-foot scopes between 1778 and 1820, out of which only 21 have survived today. It was with one of these scopes that he discovered Uranus in 1781. The aperture of the Herschel 7-foot scope was 160mm, or 6.3 inches. Reflectors of that era were made of speculum metal, which tarnished easily and reflected only 66% of the light that hit it. During the pre-Fraunhofer refractor days, it was easier for Struve to use the Troughton 3.5 inch refractor as his main observing scope, since it was much more portable and probably matched, if not exceeded, the light-gathering capability of the Herschel reflector. Consequently, the Herschel scope was used mainly for observing the occultation of stars by the Moon.

There were two Tartu University students working in the observatory (one worked the front desk and the other was letting visitors in and out of rooms]. Unfortunately, they were neither astronomy nor science majors and could not answer any of my questions regarding the Fraunhofer and other instruments.

Here is a picture of the dome of the observatory at night – you can see the moon and Venus next to it.

This next picture shows my Galileoscope 2-inch achromat refractor in front of the entrance to the observatory.

Looking forward to visiting other historic observatories, including the ones closer to home (e.g. Lick, Mt. Wilson, Palomar).