The Denver JULY 2018 OBSERVER The globular cluster, Messier 19, one of this month’s targets in “July Skies,” in a Hubble Space Telescope image. Credit: NASA, ESA, STScI and I. King (Univer- sity of California – Berkeley) JULY SKIES by Zachary Singer The Solar System ’scopes towards the planets when they’re Sky Calendar The big news for July is that Mars comes highest in the sky on a given night, to get the 6 Last-Quarter Moon to opposition on the 27th, meaning that it sharpest image—but Mars is worth viewing 12 New Moon will be at its highest in the south on that date naked-eye when it’s rising. Surprised? The 19 First-Quarter Moon around 1 AM, and also more or less at its red (well, orange) planet appears even redder 27 Full Moon largest as seen from Earth. Now, don’t let that when rising, making for much deeper color. fool you—Mars is already very good as July It’s a guilty pleasure on an aesthetic level, if begins, showing a disk 21” across, which is not a scientific one. If you want to indulge better than we got two years ago, and only yourself, Mars rises around 10:30 PM at In the Observer slightly smaller than the 24” expected at the beginning of July, an hour earlier mid- the end of the month. (Observations in my month, and about 8:20 PM at month’s end. President’s Message . .2 6-inch reflector at the end of June showed an Meanwhile, Mercury is an evening Society Directory. 2 impressive disk at just 150 power.) Realisti- target, low in the west in early July as it Schedule of Events . 2 cally, Mars will maintain its size and bright- approaches its greatest elongation (largest ness at similar levels through the end of angular distance from the Sun as seen from About Denver Astronomical Society . 3 th August, so don’t restrict yourself to observing Earth) on July 11 . After passing that mark, Astro Update . 4 the planet appears increasingly closer to the it only at opposition! DAS News . 5 For what it’s worth, we usually turn our Sun until getting lost in sunlight about mid- The Observer is available in color PDF format from the DAS Continued on Page 3 website: http://www.denverastro.org/das/denver-observer/ THE DENVER OBSERVER JULY 2018 Society Directory PRESIDENT’S MESSAGE by Ron Hranac DAS Executive Board Happy Anniversary! President: th th Ron Hranac July 14 marks the 124 anniversary of and its 20-inch refractor are still being used to [email protected] first light at the University of Denver’s his- “entertain” (and of course, educate) the public. Vice President: toric Chamberlin Observatory. On that date Counting our twice-weekly Public Nights Lindsey Shaw [email protected] in 1894, DU Professor Herbert Alonzo Howe and monthly Open Houses, upwards of 4,000 Secretary: (1858-1926) started trial observations with people visit Chamberlin each year and enjoy Ed Ladner the observatory’s 20-inch Clark-Saegmuller views through the big telescope. [email protected] refractor telescope. How big? The observatory’s Clark-Saeg- Treasurer: Scott Perrin According to the book Denver’s Great muller refractor is nearly 26 feet long, and has [email protected] Telescope (second printing, 2015), by Claire a focal length of 300 inches, or 7,500mm. The Executive Board Members: Past President, Ron Pearson M. Stencel and Robert E. Stencel, among the width of the objective lens (a doublet achro- July Candia Ed Scholes objects observed that night by Professor Howe mat, in case you were wondering) on the front Jack Eastman Sorin were stars in the globular cluster M13, and the of the ’scope is the previously mentioned 20 Joe Gafford Chris Ubing Dena McClung Dan Wray Moon. My SkySafari Pro app shows the Moon inches. That makes the refractor’s focal ratio on that Saturday night at about 93% illumina- equal to f/15. Pop a common 25mm focal President Emeritus, Larry Brooks tion. Saturn was visible above the southwest- length eyepiece into the star diagonal, at the Committees ern horizon early in the evening, although focuser end of the ’scope, and the magnifica- Van Nattan-Hansen Scholarship Fund: Megan Daniels (Chair) there is no mention in Denver’s Great Telescope tion is a bit more than 300x. (Compare that [email protected] that Howe looked at the ringed planet during to one of our ’Scope Loan Program’s Orion EGK Dark Site Committee: th Darrell Dodge, Interim Chair his July 14 observations. 8-inch Dobs, whose focal length is 1,200mm; [email protected] The first public use of the 20-inch refractor the magnification with the same 25mm eye- IDA Representative: took place a couple weeks later on Wednesday, piece is just 48x.) Dr. Robert Stencel st [email protected] August 1 , “…when Howe entertained the The Clark-Saegmuller’s optical tube as- Volunteers or Appointed Swedish Methodist Christian Endeavor Soci- sembly, German equatorial mount, cast-iron Representatives ety with a look at Saturn.” Professional use of pillar, and iron three-legged support (the latter ALCor: the observatory began in late autumn of 1894. is beneath the dome room’s wooden floor)— Darrell Dodge 303 932-1309 More than a century later, the observatory which combined weigh more than 11 tons— Newsletter Editor: Zachary Singer 303 718-4188 Continued on Page 3 [email protected] Newsletter Proofreaders: DAS SCHEDULE Darrell Dodge, Ron Hranac Website: July 2018 Darrell Dodge 6 E-Board Meeting—At DU’s Historic Chamberlin Observatory, 7:30 PM. [email protected] All members welcome. IT Coordinator: 7 DAS Member In-Reach—At DU’s Chamberlin Observatory, 7:30 PM Ken Sturrock [email protected] 14 Dark Sky Weekend—EGK Dark Site & Brooks Observatory External Outreach Coordinator: 21 DAS Picnic—DU’s Historic Chamberlin Observatory North Lawn—Starts at 4:00 PM Julie (July) Candia [email protected] 21 Open House—DU’s Historic Chamberlin Observatory—Starts at 8:30 PM Public Night Coordinator: 27 DAS General Meeting—DU’s Olin Hall, Rm. 105—Starts at 7:30 PM Hugh Davidson 303 679-0629 (August 2018) Librarian: Eileen Barela 3 E-Board Meeting—At DU’s Historic Chamberlin Observatory, 7:30 PM. Telescope Loan Program: All members welcome. Ed Scholes 11 Dark Sky Weekend—EGK Dark Site & Brooks Observatory [email protected] DAS Information Line: (303) 871-5172 During Open House, volunteer members of the DAS Public Nights feature a presentation on astronomical DAS Correspondence: bring their telescopes to the Chamberlin Observa- subjects and a small-group observing session on the Denver Astronomical Society tory’s front (south) lawn, so the public can enjoy historic 20-inch telescope (weather permitting), at Cham- P.O. Box 102738 views of the stars and planets, try out different berlin Observatory on Tuesday and Thursday evenings Denver, Colorado 80250 telescope designs, and get advice from DAS mem- (except holidays), beginning at the following times: [email protected] bers. The Observatory is open, too (costs listed March 10 - September 30 at 8:30 PM New-Member Ambassador: below), and its historic 20-inch telescope is open Digby Kirby for observing with no reservations necessary. October 1 - March 9 at 7:30 PM [email protected] Open House costs (non-members): If the skies are clear, Public Night costs (non-members): $4/adult, (970) 301-2287 $2/person ($5/family), $1/person in inclement weather. $3/child and students with ID. DAS mem- Membership Coordinator: DU students with ID, and DAS members free. bers and DU students with ID: free. Dena McClung [email protected] Members of the public (non-DAS/DU, as above), please make reservations via our website http://www.denverastro.org (www .denverastro .org) or call (303) 871-5172. The Denver Astronomical Society One Mile Nearer the Stars - 2 - ∞ THE DENVER OBSERVER JULY 2018 President’s Message Continued from Page 2 sit on top of a 25-foot-tall, 320-ton sandstone pier. The pier passes Panic_of_1893) bankrupted Chamberlin and severely depressed through the center of the building, and down into the basement. the value of the land he used for partial payment. Things eventually It’s not clear how far the pier goes below the basement level; draw- got sorted out with a combination of loans, personal funds, some ings in Denver’s Great Telescope suggest it might begin at the same payments from DU, and delays, but the observatory finally saw first level as the building’s foundation. In any event, the pier does not go light in 1894. Interestingly, the smaller student observatory next to all the way to bedrock. Chamberlin was built and operational first, with first light via its You might have noticed the unusual brackets supporting the 6-inch telescope on May 4, 1891. These days, the student observa- two grandfather type clocks located in the observatory’s main level tory building is used for storage. (one clock keeps civil time; the other, sidereal time). Those brack- A couple more tidbits: The cost of the 20-inch Clark-Saegmuller ets don’t attach the clocks to the walls. Instead, they pass through refractor was $4,185 (about $118,000 today), of which $1,000 was the walls and attach directly to the central sandstone pier. That just for the objective lens. The “Lyons Red” sandstone used to build mounting technique helps to isolate the clocks from vibrations, the observatory and pier came from a stone company owned by which would otherwise affect their accuracy. a Mr. Kimball, whose quarry was near Lyons, Colorado, on the The observatory is named after Humphrey Barker Chamberlin south end of Beech Hill (https://www.colorado.edu/fm/sites/default/ (1847-1897), who agreed to pay for its construction in the late files/attached-files/_frontrangesandstonequarries-databybilldeno.pdf).