Feb 23 2020

First Light for the 0.7m!

First Light in astronomy is an old tradition filled with all sorts of interesting history. Some first light examples are not the best, while others are just tremendous. Ours was a little of both with the first exposure of the 0.7m telescope to the nighttime sky. Don’t worry! It all turned out just fine!

The vert first exposure of starlight to the telescope was last week: Conditions were good with a nice clear sky and freezing temperatures. The wind was calm. The telescope had never been focused before and had yet to have a pointing solution…. so it really had no idea where it was looking. We decided to aim it in the general direction of Orion and take the first images. Of course, they were blurry. The scope had never been focused before. At this point we got the CCD imager into automatic mode, making it take an image every second, non-stop so that we could run the focuser until we had the images nice and sharp…. out the focuser went, and the star images got smaller and smaller and smaller, then “kachunk!” The focuser had run out of travel, and the star images were not quite in focus yet! The imager was perhaps a few millimeters away from achieving a perfect focus. The good news was that this was more than enough to engage in the time consuming process of collimating the primary mirror. A few hours later we had aligned optics, but we had to order a small spacer ring to push the CCD imagers little further out.

The bright star Betelgeuse just slightly out of focus. Note the doubled diffraction rings around Betelgeuse. Those should be single spikes. The focuser didn’t have enough travel to bring the camera to the needed distance away from the scope. Time to order a part!

The interesting thing about this telescope’s control software is the building of a pointing model. By taking a series of images all over the sky, the software does an astrometric reduction on each image and measures the slight variations in the telescope’s true pointing versus where it thinks it is pointing. This takes care of all sorts of interesting issues: flexure in the pier, telescope and mount, mirror sag or flop (none here!) and general pointing. After some 20 images, we were able to point to any object in the sky and have it show in the images we took… just like that image of Betelgeuse above.

Once the spacer arrived this past Wednesday, we went out to install it and then wait for darkness to arrive. It was a nice clear and very cold night. The goal was to build a large pointing model and take some images of famous deep sky objects. I also wanted to test out a start-up and shut-down procedure that I had typed up earlier in the week. That evening, we started everything up: the dome was homed and set to track the telescope. The CCD imager was on and cooled to -30ºC. The telescope was on, homed and tracking. Would it reach focus! Absolutely! It was spot-on perfect. We then built a large pointing model with over 100 images. Now the telescope would find and center objects of our choosing, and it would track them for better than five minutes without needing any autoguider corrections. This is quite the telescope!

We chose some of the iconic late winter deep sky objects to share with you for official first light. These are all composites of four filters:

Luminance: a clear filter
J-C Rc: which was used as the red channel
J-C V: which was used as the green channel
J-C B: which was used as the blue channel.

The V, B, and Rc filters are Johnson-Cousins photometric filters used for photometry, the science of measuring brightnesses, which can lead to our understanding of an object’s surface temperature and size, among other things.

You might want to dim the room lights to see the details. Also, click on the images to see in a larger format. Enjoy!

The Orion Nebula, M-42, a star birth region about 1300 light-years away. This can be seen with binoculars and small telescopes easily. It was almost too bright for our CCD imager!

M-82, the Cigar Galaxy, a starburst galaxy about 12 million light-years distant.

M-81, Bode’s Galaxy, about 12 million light-years away. This resides very close to M-82.

This is the Crab Nebula, M-1 in Taurus. This is a supernova remnant from a star that exploded back in 1054 A.D.

The next phase of this telescope’s use will be to collect scientific data. We have already taken images of U Gem and V Ori to calibrate our photometry and to see if we can produce good data for scientific publication. It has passed with flying colors thus far!

Feb 18 2020

Telescope Installation

With the building complete, the time had come to install the telescope. Arriving early on a Wednesday morning, whole crews of people came to be a part of the event: the crane operator, the contractor, architect, videographers, students and more! It is not often that one gets to see such a large telescope lowered onto its pier using a crane. Below is a photo journal of that day’s events as well as the following day during which PlaneWave’s engineer, Matt Dieterich, and I spent the day wiring the systems and testing the electronics.

Brian Carmody and Matt Dieterich begin the initial inspection of the dome and pier prior to getting the installation started.

The CDK700 telescope arrives on a flatbed from the storage facility. The crane and operator has already arrived, so things are about to get busy!

The various telescope components were then uncrated while on the truck.

Tethering the telescope’s mount and primary mirror assembly to be hoisted. It was at about this point that everyone’s heart rate went up a little!

The telescope is now airborne, taking a short ride from the truck to the pier within the dome.

With some serious expertise, the telescope was guided gently to the dome.

The telescope being lowered through the dome’s shutter. While Matt (and everyone) looks on.

The sunrise continues while the telescope is gently lowered to the three bolts that will hold it onto the pier.

Slowly, slowly, slowly. Using tag lines, the telescope is kept from swaying or rotating as it is lowered into the dome.

The telescope had to be lowered onto the three pier bolts. Tolerances were to the millimeter!

The telescope’s mount holes aligned perfectly with the pier bolts. Everyone breathed a sigh of relief at the exact moment when the scope landed onto the levelling bolts.

Now it was time to repeat this whole process with the secondary mirror cage and assembly.

The secondary mirror arrives in place and is bolted to the telescope.

Next to install was the telescope’s control system which feeds power, reads encoders and sends commands back and forth through a neat intranet system.

The many components within the control box.

Using a laser mounted onto one of the two Nasmyth focal points, Matt begins initial collimation of the three mirrors. The corrected Dall-Kirkham optical design uses an elliptical primary, a spherical secondary and a flat tertiary mirror.

The many wires routed from the telescope’s interior, to the control box and to the control room computer.

Those same wires, this time a view from the base of the telescope mount. Within the mount are USB hubs, power supplies, and encoder systems. All must be wired correctly to allow proper control and to prevent twisting as the telescope moves in azimuth.

The pirmary CCD and filter wheel installed

The primary instrument will be an FLI CCD imager with a 10-place filter wheel, seen here at focal port #1 attached to the electronic focuser/de-rotator. All of these components are remotely controlled.

Brian, Matt and John: three happy and very tired telescope installers. The end of two days of work. Next steps? Clear skies to collimate and focus the telescope then build a pointing model.

Feb 3 2020

The 0.70m Imaging Train

The soon-to-be-installed 0.70m telescope will not have provision for eyepice viewing. Instead, telescopes of this size usually have an imaging system for collecting image data, among other instruments attached. This telescope will have tow primary instruments attached at its two focal points: an imaging CCD and a fiver-fed spectrograph.

The imaging CCD will be a Finger Lakes Instruments (FLI) PL16803 4096×4096 9μm pixel array (16.8 megapixel array) with an attached 10-place filter wheel system. The CCD is a non-antiblooming gate (NABG) system and is linear for most of its efficiency range. Below is a plot of its quantum efficiency. Given that it cooler can get 55ºC below ambient temperatures, we’ll be operating well below freezing every night, even in the summer. This means less thermal noise and clearer images with better data.

FLI CCD Imager right out of the box.

The filter wheel is a ten-place system, holding 10x50mm square filters for astronomical imaging. In this installation we’ll be using the system mostly for photometric and astrometric work, so the following filters have been installed:

Luminance: a clear filter.
Hα: Narrow band Hydrogen filter.
OIII: Oxygen narrow band filter.
SII: Sulfur narrowband filter.
g’2: The Sloan (SDSS) g photometric filter.
r’2: The Sloan r photometric filter.
B: Johnson/Cousins B photometric filter (Blue).
V: Johnson/Cousins V photometric filter (Green/Visual).
Rc: Johnson/Cousins Rc photometric filter (Red).
One empty filter position just in case 🙂

The FLI CFW-3-10 filter wheel ready to accept filters and the CCD imager.

The CCD bolts right onto the filter wheel, then the whole assembly is attached to the focal plane of the telescope. All of this is controlled remotely using imaging software, in this case MaxIm DL and ASCOM.

Installing all this requires good lighting, a relatively dust free environment, small tools and some time.

The color filters in their packaging, ready to be installed.

Equipment at the ready: it’s time to install the filters.

With clean-room gloves on, each filter is removed from its packaging, then placed into the correct slot with the filter wheel. Two small plastic retainers are then screwed into place to hold the filter wheel in place. The lovely part of this system’s design is that the filters can be installed without removing the filter wheel’s cover. Many others on the market require complete disassembly – not fun.

Should you be interested, some external Links:

Jan 18 2020

A Wide Field Orion Taking on Taurus

Winter is the Orion time…. time to get a wide field camera taking snaps of the winter sky. Here is a wide field frame of Orion with his nemesis, Taurus the Bull. This was a process-image of seven 15-second exposures at f/3.5 28mm, ISO10000, with automatic dark frame subtraction using a Nikon D810a on a tracking mount. Post processing was done in PixInsight to stack the images using median combine, flatten the background, correct color, then crop and save off as a JPG with the correct histogram. Some graininess was removed in Photoshop in the end.

This shows Orion with its definitely-fading Betelgeuse (upper left shoulder), the Orion Nebula, The Barnard Loop, The Rosette Nebula, Sh2-264 (Lamda Orionis Ring) and NGC2175 (upper left). Click on the image for full size.

Orion and Taurus Wide Field 2020-01-18

For an annotated picture:

Jan 15 2020

Betelgeuse is Fading

There has been a lot of buzz on the net about the star, Betelgeuse, Alpha Ori… the red supergiant in Orion’s shoulder (or armpit as people might prefer). It is a well known, bright red, supergiant, and it is a well known variable with a long period. Of late, it has been fading rather unusually for its regular patterns of ups and downs in brightness. This fading has everyone charged up…. you see, the star is old, near the end of its life. Stars of this high mass are supposed to supernova… BOOM! The trick is to know when. We have little idea on that, so any changes seen in stars like this make us get realllllly focused. Below is a snap of the latest observations of Betelgeuse’s brightness in V taken from the AAVSO. You can go see this data for yourself at http://www.aavso.org, and entering “Alfa Ori” sans quotes into the “Pick a star” field on the lower right of the page. Select plot light curve after that.

AAVSO V filter light curve of Betelgeuse

Orion with Betelgeuse as it would appear at 9:00pm from mid-northern latitudes tonight (January 15)

Dec 27 2019

The Dome Works!

Not a surprise at all, but we now have a rotating, opening and closing dome! Next steps are to putty in the weather seal along edges, and it will be complete. The interior of the building is getting walls and paint soon. Lighting and network cabling come next followed by the installation of the telescope by end of January! Stay tuned!

A wide angle look at the dome interior with the lower shutter open.

Exterior view with the lower shutter open and the dome rotated to point north.

All three of the observatory’s domes visible for comparison.

Below: Two short movies of the dome shutter being opened. This is a two-part process with the top shutter opened first followed by the lower shutter which tilts out. The top shutter’s lower edge overlaps the bottom shutter thus preventing weather from getting inside.

Dec 21 2019

There is a Roof and a Dome

Progress has been swift on the construction of the new building. Roofers have installed the waterproof roof layer and sealed around the dome’s base structure (framing). The dome has been built in place, and the shutter also installed. Interior work now progresses with the installation of the walls, trim, lights and such. Remember that for any of the images below, just click on them for a larger view.

Prior to pouring the concrete walkway we were expecting both rain then snow and freezing temperatures. Heating pads were placed to prevent frost on the ground before pouring the cement.

One wall has siding in this image, and the dome opening has been covered to protect the interior from rainfall.

All four exterior walls now have been sided, ventilation louvers have been installed, and the roofers are working on the rubberized layer on top the structure and around the dome, base frame.

Inside the control room, the base bearings of the dome have been unpacked for inspection and comprehension! So many parts are in this package, that it is a little mystifying.

The view of the telescope room through the framed wall of the control room. The window casement has been installed along with initial conduit for electrical. network and telescope control lines.

The dome is almost complete in this image taken at 6:30am with the sun rising. The dome’s motion is smooth and has that familiar rumble to it as it rotates in azimuth on its well-aligned and level bearings.

A wide-field image of the dome interior. Note that edges are a little warped in this image due to the camera’s odd stitching of the frames. You can see the top of the pier and the orange power line system for dome operations which make the system effectively wireless. No wires will be dangling down from above to control the dome’s motion.

Roof is complete. Dome is complete. Door has been installed.

Dec 3 2019

2019 Geminid Meteor Shower

One of the best meteor showers of the year is rapidly approaching. Peaking on the night of December 13/14, the Geminids put on a good show with peaks averaging at 120 meteors per hour. Now, with the moon being just past full that night, many of the fainter meteors will be drowned out by moonlight. Don’t be discouraged, though: we still expect to see some 30 meteors per hour. The best time to watch? After midnight, usually around 2:00am is best, but you can start seeing them after 10pm easily enough. Gemini will be high in the sky, and the night time side of Earth will be heading into the meteor stream.

The source of these meteors is from asteroid 3200 Phaethon, named after the son of Helios… Phaeton swings very close to the Sun in its orbit, being one of the Apollo asteroid members. Does it pose a threat to Earth? Not for the next 400 years or so, which is as far as our high-level orbital analysis shows. The asteroid has a 30 year orbit… so maybe in the distant future we might have to worry about this one.

Looking east at about 9pm local time, the constellations Orion and Gemini will be well above the horizon. Alas, the moon will also be in Gemini and just past full phase. Rather than looking at the moon-lit Gemini, look straight up and all around in the sky for the Geminid meteors.

Nov 17 2019

The Structure Takes Shape

This has been an exciting couple of weeks. As we have seen our first frost of the season (no snow just yet!), we have been putting up the frame and the structure of the building. Click on images for full size.

The corners of the building have been placed and the first wall frame goes up.

Work on the wall frames continues. Soon after this they will be sheathed with plywood.

The four walls are up, and the roof’s lower layers have been installed. There is also a ring for the dome.

The entrance to the observatory. Note the walls inside have yet to receive their plywood, and the floor needs to have concrete poured.

A view of the dome base framework from the rooftop. Imagine a large telescope on the pier with a 16′ dome surrounding it. The roof has a slight pitch to allow water and snow to run off to the north.

Another view from the roof. Where is that dome? Here it is! It’s the bundle of materials on the pallet. Some assembly is required. The black mats are covering what will be the walkway to the building.

Nov 10 2019

Now That is a Pier!

Construction is well on its way. The pier being poured and the concrete now setting, the various braces have been removed allowing for a clear view of the structure’s foundation.

ExeterAstro

Astronomy at Phillips Exeter Academy