Founded in 1937 at the US Naval Observatory by a group of professional and amateur astronomers, the National Capital Astronomers (NCA) is a volunteer-driven nonprofit aiming to ignite public interest in astronomy and space science. We're all about sharing the wonders of the universe with everyone!
While we marvel at the discovery of thousands of exoplanets, we recognize Earth's unique hospitality. This drives our mission to protect our planet's resources and life. After all, as Captain Kirk (a.k.a. William Shatner) discovered, space is a harsh place!
Join us for a cosmic journey and be part of our mission to explore, understand, and protect our universe!
NCA has regular monthly meetings September through June on the second Saturday of the month. For 2025-26, meetings will be held in-person at the University of Maryland Astronomical Observatory in College Park, Maryland (directions/map) AND online via Zoom (details below). Seating is limited, so we are encouraging folks to attend via Zoom.
Public transportation: Directions/maps to the UMD Observatory
Inclement weather: In case of severe weather (tornado/snow/impassable roads), a notice will be placed on the Observatory Website on the day of the meeting. (Be sure to refresh/reload the page to make sure you are seeing an updated page.)
The meetings for this year will be HYBRID (online via Zoom AND in-person), unless otherwise noted!
With permission of the speakers, most meetings will be recorded. Once available the audio and video will be linked.
National Capital Astronomers will be holding its 2025-2026 meetings online via Zoom and in-person. This year, the Zoom meetings have been set up so that there is no registration required. This is the direct Zoom link, it is the same for everybody for every meeting this year. If we have problems with Zoom bombing at a meeting, then the link will be canceled and a new one created that will require registration for subsequent meetings.
As usual, the Zoom room "doors" open at 7pm ET with the actual meeting starting on time at 7:30pm! While you do not need to sign in right at 7pm, please do not wait until 7:35pm!! And since we are not registering folks, it will be important that you have a recognizable name showing so that I can let you in from the virtual waiting room.
With the permission of the guestspeakers, we will be recording the meetings.
Join Zoom Meeting: NCA Monthly Zoom
These guidelines will be updated as needed.
Dharma Prasad Agrahar - NCA
7:30 pm
Abstract: An SHG - spectroheliograph - is an optical instrument or a device that is used to analyze individual wavelengths of sunlight. The spectroheliograph, in combination with a typical amateur grade refractor telescope and a modern planetary digital camera that supports captures at very high fps (frames per second), mounted on an equatorial telescope mount is used to scan the sun. The spectroheliograph splits the sunlight or the radiation from the sun into individual wavelength of our choice, which is captured in the form of a 16-bit video. The individual frames of the video are then assembled together to create the image of the sun at that specific wavelength. My spectroheliograph is a DIY unit. I built it using two old screw-mount Pentax camera lenses that I bought on ebay, a 50x50mm holographic reflective grating and an 8?m quartz slit, placed inside a 3D-printed housing that is sealed from entry of stray light. My presentation will cover a brief history of spectroheliographs, some theory behind it, how I built my device, how to align it and how to generate the images of the sun at different wavelengths including Hydrogen-?, Hydrogen-?, Sodium-D1 & D2, Helium-D3, Calcium-H, Calcium-K and more.
Bio: I am a retired individual with engineering background, after a long career in the elevator and escalator business, I have been keeping busy by spending my retirement time in amateur astronomy. I have been a member of NCA for maybe, 16 years or so. I built my 8-inch f/6.3 Newtonian-Dobsonian under the expert guidance of Guy Brandenburg, that included making a Crayford focuser at the telescope workshop at the CCCC. My Newt-Dob won the 2nd place for its optical performance at Stellafane in 2015. See stellafane.org/convention/2015/2015-scopes.html for the listing and photos.
I got interested in solar observation in 2017, soon after the Great American Solar Eclipse. After a few years of visual observing with different white light filters, a Herschel wedge and then an Etalon-based H? telescope, I progressed into imaging the Sun. In 2023, the use of a spectroheliograph for solar imaging caught my attention. I began studying it. As an active ATMer (Amateur Telescope Maker), I love making or building my equipment. I tried making one based on a French design that uses entirely 3D printed parts with limited success. Finally, this led me to my current DIY spectroheliograph. Today, I run my DIY spectroheliograph on a DIY "harmonic drive mount" that I have built on which the refractor and the spectroheliograph are mounted.
Weather-permitting, there will be observing through the telescopes after the meeting for members and guests.
The telescope making, maintenance, and modification workshop with Guy Brandenburg is held in the basement (wood shop) of the Chevy Chase Community Center which is located at the intersection of McKinley Street and Connecticut Avenue, NW, a few blocks inside the DC boundary, on the northeast corner of the intersection. The workshop is open on Tuesdays & Fridays, from 6:00 to 9:00 PM. For information visit Guy's Website. To contact Guy, call 202-262-4274 or Email Guy!
Exploring the Sky is a joint program between the National Capital Astronomers and the National Park Service Rock Creek Park Nature Center and has been run since 1948 at this location, the field at the corner of Glover and Military Roads in the District. There is an adjacent parking lot. It is free and all are welcome who have an interest in observing the heavens. It's not an ideal dark sky location but we can still see solar system objects (even the occasional comet), open and globular clusters and maybe a fuzzy galaxy or two.
Questions? Call NCA at 202-262-4274 and leave a message.
| Date | Time | Things of interest |
| 05 Apr | 8:00pm | M45, Orion, Moon, Mars, Jupiter, Uranus |
| 03 May | 9:00pm | M44, Leo, Arcturus, M13, Moon, Mars, Jupiter |
| 07 Jun | 9:00pm | Leo, Bootes, Hercules, M13, Moon |
| 05 Jul | 9:00pm | Moon, Hercules, M13, Summer Triangle |
| 02 Aug | 8:30pm | Moon, Hercules, M13, Summer Triangle, M57 |
| 20 Sep | 8:00pm | Moon, Summer Triangle, Great Square of Pegasus, Saturn |
| 18 Oct | 7:30pm | Summer Triangle, Great Square of Pegasus, M31, Saturn |
| 15 Nov | 7:00pm | Venus, Summer Triangle, Pegasus, M31, Saturn, Uranus |