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10/05/2018 – Ephemeris – All about telescopes for the gift giving season

October 5, 2018 Comments off

Ephemeris for Friday, October 5th. The Sun will rise at 7:45. It’ll be up for 11 hours and 30 minutes, setting at 7:15. The Moon, halfway from last quarter to new, will rise at 4:28 tomorrow morning.

We at the Grand Traverse Astronomical Society get asked a lot about what kind of telescope to get for their beginning astronomer, whether young or old. With the gift-giving season coming upon us, now is the time to plan ahead. This month’s meeting at 8 p.m. at the Northwestern Michigan College’s Rogers Observatory there will be several types of telescopes there, including one of mine*. There is no right telescope, but there are lots of wrong telescopes, and its not always the telescope itself, but the mounting that’s the problem. Society members will show you what the various telescopes can do, what you need, and don’t need. What’s the best telescope for what price range.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

* I’m currently suffering from a sprained wrist, so I may not be able to bring in my 11″ Dobsonian telescope, but will bring in a much smaller (3″) telescope of similar design instead.

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02/02/2018 – Ephemeris – Telescope clinic rescheduled to tonight

February 2, 2018 Comments off

Ephemeris for Ground Hog Day, Friday, February 2nd. The Sun will rise at 8:00. It’ll be up for 9 hours and 52 minutes, setting at 5:52. The Moon, 2 days past full, will rise at 8:43 this evening.

If you’ve received a telescope for Christmas and are having trouble setting it up, or have an unused one in a closet, basement or attic, bring them to Northwestern Michigan College’s Rogers Observatory tonight at 8 p.m. The Grand Traverse Astronomical Society will be holding their annual telescope clinic to help you understand and use your telescope. Last month’s meeting and clinic was canceled due to the weather. The clinic will extend through the period that will be set aside for a star party if it’s clear, to test the telescopes and show the owners how to use them. Like anything telescopes take some time to learn how to use them and find celestial objects. The observatory is south of Traverse City on Birmley Road.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

01/05/2018 – Ephemeris – Telescope Clinic tonight (Has been canceled due to weather)

January 5, 2018 1 comment

Ephemeris for Friday, January 5th. The Sun will rise at 8:19. It’ll be up for 8 hours and 56 minutes, setting at 5:16. The Moon, 3 days before last quarter, will rise at 9:56 this evening.

If you’ve received a telescope for Christmas and are having trouble setting it up, or have an unused one in a closet, basement or attic, bring them to Northwestern Michigan College’s Rogers Observatory tonight at 8 p.m. The Grand Traverse Astronomical Society will be holding their annual telescope clinic to help you understand and use your telescope. The clinic will extend through the period that will be set aside for a star party if it’s clear, to test the telescopes and show the owners how to use them. Like anything telescopes take some time to learn how to use them and find celestial objects. It took me 15 minutes to find Saturn with a telescope the first time I tried, and I knew where it was in the sky. The observatory is south of Traverse City on Birmley Road.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Link to my December 26 post on telescope basics to start you off:  https://bobmoler.wordpress.com/2017/12/26/

Can’t make it tonight? Members are generally available at star parties at the observatory when time permits to help folks who bring their telescopes out. See http://www.gtastro.org for our current schedule of events for 2018.

Updated 7:02 p.m.

12/26/2017 – Ephemeris – Help for that Christmas telescope

December 26, 2017 1 comment

Ephemeris for Tuesday, December 26th. The Sun will rise at 8:18. It’ll be up for 8 hours and 49 minutes, setting at 5:08. The Moon, at first quarter today, will set at 1:34 tomorrow morning.

Get a telescope for Christmas? Or is there one lurking in a closet or attic? Tonight’s a good time to get it out, if it’s clear, because there’s a first quarter Moon out. I consider the Moon round the first quarter to provide the finest viewing.  To get started, most astronomical telescopes have a small finder scope attached. Daytime is the best time to align them on a distant object. To find anything, even the Moon, use the lowest power eyepiece. In most scopes that’s a 20 to 25 millimeter eyepiece. Eyepieces with lower numbers are higher power. Most amateur astronomers use their lowest magnification 90% of the time. The bright planets right now are in the morning sky, and only Jupiter is worth looking at. It’s easy to find because it’s the brightest star-like object, and in the southeast before 7:30 a.m. To help you further, on January 5th, at Northwestern Michigan College’s Rogers Observatory the Grand Traverse Astronomical Society will host its annual Telescope Clinic for telescopes new and old.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Here’s a handout we make available at these telescope clinics:

Telescope Basics

Telescope Types

                           Telescope Types

There are two basic telescope types: The refractor or refracting telescope and reflector or reflecting telescope. The reflecting type shown is a Newtonian telescope, is the simplest and most inexpensive reflector. The Catadioptric (Mirror-Lens) telescope uses a corrector plate in front of the telescope. The one shown is a type called a Maksutov-Cassegrain. The more popular type is the Schmidt-Cassegrain which uses a thin, nearly flat corrector plate. The Cassegrain design uses a convex secondary mirror the sends the light back through a hole in the Primary mirror (O) to an eyepiece.

Refracting telescopes get expensive in a hurry as the diameter of the objective (O) lens increases due to the requirements of at least 4 lens surfaces of the at least two lenses that make it up. The reason for it is to correct for color fringes that would result around bright objects seen through it (chromatic aberration), and the optical quality of the glass required. Reflectors primary mirror have a single surface and the glass simply supports it. The corrector plates of the catadioptric telescopes don’t create chromatic aberration because they don’t bend light much. Telescopes are rated by the diameter of their objectives (O). One could purchase an 11 inch Newtonian telescope for less than $1,000, An 11” Schmidt-Cassegrain for $2,500, or an 11” refractor for the cost of a Lexus.

The reason astronomers go for wider telescopes (greater aperture) is two-fold: To gather more light to better see faint objects, and to increase resolving power, the ability of the telescope to see fine detail and be able to use higher magnification. We’ll see the rules when we talk about eyepieces.

Telescope Mounts

Telescope MountsThere are four basic mounts. Equatorial mounts have to be aligned to the earth’s axis in order to work properly to follow objects in the sky. Alt-Azimuth mounts are the simplest and easiest to set up, but all but the most sophisticated cannot be made to track objects in the sky as the Earth rotates. A relatively new addition to mounts is the computerized “Go To” feature allows the telescope to find objects itself when the mount is properly aligned to the sky. Telescopes with Dobsonian mounts have the largest aperture for the buck. Cheap telescopes tend to have cheap mounts that are hard to use and wobbly, especially the ones with German equatorial mounts. An alt-azimuth mount would be steadier and a whole lot easier to use in this case.

Finder Telescopes

The telescope eyepiece covers so little area of the sky to make finding anything virtually impossible. So all telescopes have small finder scopes attached of 6 to 10 power, or 1 power devices that put a finder circle or red dot on the sky when you look through them. A newer finder idea is a mount for a green laser that projects a beam in the atmosphere toward the object to be located. The author prefers a finder with an aperture of at least 50mm to be able to see most of the dim objects he’s looking for. In the main telescope, use the lowest power eyepiece because it has the widest field of view.

Eyepieces

Magnifying power or magnification is not a telescope property. The eyepiece is essentially a magnifying glass to view the real image that the objective lens or mirror produces at the focal plane (F) in the telescope type diagram on the first page. The focal length of the objective lens or mirror or the effective focal length of the mirrors of the catadioptric telescope divided by the focal length of the eyepiece gives the magnification of that particular combination of telescope and eyepiece. The focal length of the eyepiece is marked on the eyepiece. The telescope focal length may or may not be stamped or marked on the telescope, if not, check the owner’s manual for that quantity.

A telescope will generally come with one or two eyepieces, The lowest power eyepiece will generally be a 25mm eyepiece of some kind. Eyepieces come in 2 standard barrel sizes, 1 ¼ inch and 2 inch. There are some old telescopes that only accept sub 1 inch eyepieces. You may have to hunt to see if any of those size eyepieces are still around. The cheaper the telescope the crummier the eyepiece. Decent eyepieces start at around $35 and go up from there. The best way to tell which eyepiece fits your needs is to ask an astronomer what eyepiece he or she is using at a star party.

About magnification. The highest usable magnification in a telescope is calculated as the aperture in millimeters times 2.4 or aperture in inches times 60. After that the image becomes fuzzy and dim. It’s due to the wave nature of light. I halve those values in his experience. I’d rather have small crisp images than big fuzzy ones devoid of contrast.

A handy accessory to have is a Barlow lens, a negative lens in a tube, that the eyepiece is slipped in before inserting the pair in the eyepiece holder. It will double the power of the eyepiece. So with two eyepieces and a Barlow four separate magnifications are available. The author would rather us a lower power eyepiece with a Barlow than a high power eyepiece of the same power. In that same vein a good low power wide-angle eyepiece is generally the first extra eyepiece astronomers purchase. More expensive ones can be like viewing the universe in IMAX. Here is a truism: Amateur astronomers use their telescope’s lowest power 90% of the time.

Solar filters that fit over the front of the telescope and finder is a fine addition to any telescope and allow viewing of our star close up. Some old telescopes have a solar filter that fits in an eyepiece. For your visual health take the filter and beat it to death with a hammer, and throw it away. There are also filters that can filter out some of the light pollution for dim nebulae. There are filters also to bring out detail in planets.

Above all, have fun! If you have any questions ask that friendly amateur astronomer over there, standing by his or her telescope at the next star party.

03/17/2017 – Ephemeris – When Ireland had the largest telescope in the world

March 17, 2017 Comments off

Ephemeris for St. Patrick’s Day, Friday, March 17th.  The Sun will rise at 7:50.  It’ll be up for 12 hours even, setting at 7:51.  The Moon, 3 days before last quarter, will rise at 1:01 tomorrow morning.

In the 19th century Ireland laid claim to having the largest telescope in the world.  It was a reflecting telescope with a mirror diameter of 72 inches.  It was built by William Parsons the Third Earl of Rosse.  The base of the telescope tube rested in a pit between two massive walls and could only look in a north-south direction.  It saw first usage in 1847.  The telescope was called the Leviathan of Parsonstown, and was in use until 1890.  Mirrors in those days was made of a silvery alloy called speculum.  Two mirrors were used alternately because speculum tarnished.  The mirror not in use would have to be re-polished and swapped in from time to time.  It was the largest telescope until the 100 inch at Mt. Wilson was put in service in 1917.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Leviathan of Parsonstown

The 72 inch Leviathan of Parsonstown. source: http://www.klima-luft.de/steinicke/ngcic/persons/rosse3.htm

M51 drawing

A drawing of the Whirlpool Galaxy, M51 (NGC 5194 & 5195) by Lord Rosse with the 72 inch telescope. Public Domain.

M51 photo

The Whirlpool Galaxy, M51. Credit Scott Anttila.

The Whirlpool Galaxy is the only galaxy that I’ve actually visually seen spiral arms on.  It was seen using a Celestron 14″ telescope at Northwestern Michigan’s Joseph H. Rogers Observatory.  That was a looong time ago.

01/06/2017 – Ephemeris – Telescope Clinic tonight at the NMC Observatory

January 6, 2017 Comments off

Ephemeris for Friday, January 6th.  The Sun will rise at 8:19.  It’ll be up for 8 hours and 59 minutes, setting at 5:18.  The Moon, 1 day past first quarter, will set at 2:34 tomorrow morning.

If you’ve received a telescope for Christmas and are having trouble setting it up, or have an unused one in a closet, basement or attic, bring them to Northwestern Michigan College’s Rogers Observatory tonight at 8 p.m.  The Grand Traverse Astronomical Society will be holding their annual telescope clinic to help you understand and use your telescope.  The clinic will extend through the period that will be set aside for a star party if it’s clear, to test the telescopes and show the owners how to use them.  Like anything telescopes take some time to learn how to use them and find celestial objects.  It took me 15 minutes to find Saturn with a telescope the first time I tried, and I knew where it was in the sky.  The observatory is south of Traverse City on Birmley Road.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

In Memorium

Emmett Holmes

Emmett Holmes passed away last night (January 5th, 2017) after a long ordeal in attempting to have stem cells from his sister infused into his blood to rebuild his bone marrow. We at the Grand Traverse Astronomical Society knew him for a few short years, but in the time we benefited greatly from his expertise with telescopes and, helping out with star parties.. In the picture is his 13″ telescope with its distinctive tube that he built. Just recently he was elected to the Board of Directors of the Society.
We at the GTAS express our condolences to his wife Karen and the rest of his family. Emmett, rest in peace.

09/03/2015 – Ephemeris – Jewels in the shield

September 3, 2015 Comments off

Ephemeris for Thursday, September 3rd.  The Sun will rise at 7:07.  It’ll be up for 13 hours and 9 minutes, setting at 8:16.   The Moon, 2 days before last quarter, will rise at 11:26 this evening.

The teapot pattern of stars that is the constellation of Sagittarius lies at the southern end of the Milky Way this evening. It appears that the Milky Way is steam rising from the spout.  The area above Sagittarius in the brightest part of the Milky Way is the dim constellation of Scutum the shield.  Don’t bother looking for the stars that make up the constellation; what’s important is the star clouds of the Milky Way.  Scan this area with binoculars or small telescope for star clusters and nebulae or clouds of gas.  In binoculars both clusters and nebulae will appear fuzzy, but a small telescope will tell most of them apart.  Even if you’ve never been able to find anything in your telescope, you’ll find something here.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Scutum

Scutum between Sagittarius below and Aquila above at 10 p.m. September 3, 2015. Created using Stellarium.

Star hopping in Scutum

How to find the three brightest deep sky wonders around Scutum by star hopping. Created using Stellarium, annotated by myself.

Star hopping is a method to find objects from familiar star patterns.  At the top my method to find M11, the wild duck cluster is to locate the three stars at the tail of Aquila the Eagle and follow them to M11.  M11 takes a little bigger telescope to resolve.  I remember having trouble resolving it is a 5″ telescope.  It looks like a triangular cluster with all the stars of the same dimness except one brighter one.

At the bottom of Scutum, I locate that distinctive 5 star group circled.  Directly west is M16, the Eagle Nebula and star cluster.  The star cluster is easy to spot, the nebula is hard.  The Hubble space telescope made the nebula famous in the 1990’s as the Pillars of Creation.

Below and west is M17, the Omega Nebula, or the Swan Nebula.  To me it looks like a swan swimming or a check mark of nebulosity.  The associated star cluster is much less noticeable.

Happy star hopping.