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Posts by John A. Blackwell

12
Mar

A 360 Degree Tour of the 0.7m Dome

The new 0.7m telescope dome is up and running at Phillips Exeter Academy. There is still some serious testing to do in order to prove out the various bits and pieces that all have to integrate together: mount control, focus control, heaters, fans, pointing models, dome control, linking dome to the telescope, imager and filter wheel control. We’ve had a couple of clear nights, and thus far everything seems to be working. Below are two 360 degree tours of the building. One is a view from the control room. The other is from the dome. Be sure to use your mouse to look around the images by clicking and dragging. You can also zoom in and out. Enjoy!

18
Jan

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.

Wide field view of Orion and Taurus 2020-01-18

Wide field view of Orion and Taurus 2020-01-18

An annotated image is below. Once again, click on this to see full scale.

Orion annotated

15
Jan

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 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

AAVSO V filter light curve of Betelgeuse

Where is Betelgeuse located? Here’s a chart as seen from mid northern latitudes tonight at 9:00pm

Orion

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

4
Dec

How to Observe a Meteor Shower

Whenever the major yearly meteor showers show up on our calendar, I am often asked:

  • How do I observe a meteor shower?
  • What’s the best place to go?
  • What is the best time to observe?
  • Do I need a telescope: also, is your observatory open?

Here is some helpful information to help you plan out your meteor shower observing event.

Best Methods:

Look up!  That is all there is to it for the vast majority of meteor showers. You need to lie down and look up! Keep your field of vision away from obstructions (trees, houses, etc). At a minimum keep your vision aimed at 45 to 60 degrees above the horizon.

I recommend bringing a blanket, a sleeping bag, some snacks and warm drinks to help you stay safe, comfortable and awake. A lawn chair helps to keep you off the moist ground.

You do not need any optical instruments. Meteors streak across the sky as the small particles disintegrate in our atmosphere. These quick streaks of light will cover some 10 degrees or much more. Now, there are some telescopic meteor showers. There is a lot to be said about doing science with the use of a wide field instrument like a pair of binoculars or a rich field telescope. My recommendation is that if you are new to observing showers, then keep the telescopic meteor showers in your back pocket until you have some experience with what to expect and some of the science behind it all.  More info about this can be found here: Telescopic meteor observing (external link to Society for Popular Astronomy).

Location:

The very best piece of advice is this: go to a place that is far away from city and town lights. Nothing (except the weather) causes more interference to meteor shower observing than lights. Stay away from them. Period.  This includes your own lights that you might bring with you: Flash lights? No. Cell phones? No. Candles, lanterns? No. This also includes lights you cannot control: the moon, aurora or zodiacal light.

During the summer, avoid low lying areas that get foggy in the late hours (near swamps, rivers, etc). This also helps reduce your being bothered by mosquitoes.  Bring and use DEET. During the winter be sure you can get to a place of safety and warmth when you are done. Make sure that your car battery works well before driving to a remote site! You don’t want to get stuck some place in the cold and typically away from good cell phone reception.

If your observing takes you to some place unknown: scope it out first. If it’s on private property, get written permission to observe from that location.  Tell people where you are going.

Best sites are fields away from trees which block some of your view.

Time:

Meteor showers happen when the planet Earth orbits through debris left behind by comets and asteroids in their orbits around the Sun.  The side of the Earth that faces the same direction as our orbital path is on the morning side of the planet…. so the best time is very typically after local midnight until the morning dawn. This makes showers tricky for little kids and those who have to get to work the next day!

Other Thoughts:

Do you wear bifocals or multifocal glasses? Change them out for distance-only glasses if you can. All the stars in your entire field of vision should be in focus at once.

Bring a friend or two: that way you can see more of the sky and share the event. It also allows you to keep each other awake! Start with a pot-luck supper and turn it into an event.

Keep reasonable expectations: Not all showers have huge cataclysmic appearances… in fact those huge shower events are rare. Astronomy enthusiast calendars will post a tidbit of information for you: the Zenithal Hourly Rate. This ZHR is an estimation of how many meteors you could expect to see from the shower on the night of the shower’s peak under perfect observing conditions. Rarely will you see anything close to that value.

Geminid Meteors

An outburst of Geminid Meteors in 2009 taken with a wide field lens in a time exposure (Credit NASA/JPL).

More Information (links to external sites):

3
Dec
2019 Geminid Shower

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.

2019 Geminid Shower

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.