Observatory
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Observatory
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Grand View Observatory Grand View Observatory (GVO) is the collaboration of Brian and Julie McCandless. The facilities include Celestron and Vixen telescopes, Optec photometers for BVRI, Wing, and J and H band measurements, Santa Barbara Instrument Group (SBIG) ST7-XME CCD cameras, and an SBIG SGS spectrograph for spectral acquisition from 400 to 1000 nm. For planetary viewing there is a Vixen VC200L catadioptric telescope and a 4.5 inch f/12 Dall-Kirkham reflector made by Bill Hurdman in the early 1980's. At present, all of our telescopes are operated en plein aire, in preferred spots of the yards, depending on where we need to aim them. Our differential photometric results are reduced using home-written software and submitted to the AAVSO (observer code MBE). We rely heavily on the book Astronomical Photometry by A. Henden and R. Kaitchuck, Willmann-Bell (1990) for reference to techniques and standard cluster star magnitudes. The 2008 AAVSO website has been upgraded so that we (all) have access to more BRI and JH data than ever and have expanded our list of standard stars - thank you to the good folks up there! We are relatively new to quantifying CCD astronomical spectrographs and so our data reduction is still quantitatively maturing. In addition, our Elkton site is so light-polluted that deep-space spectra are contaminated by sodium and mercury lines. Nevertheless we persevere and will make raw data files available to any interested researchers upon request: Selected GVO Data
On Single Channel Photometry We prefer to do single-channel photometry (SCP) over CCD photometry. Apart from being what Brian learned to do in his youth, SCP has advantages for our observing program. Real-time events become really apparent, such as flickering and the approach of clouds or aurorae. The method is more accurate than visual estimates and likewise affords access to a wide magnitude range, so the dynamic range is good and there are plenty of interesting objects to monitor. Using different filters and detectors allows a wide wavelength range to be covered at a modest cost. No computer is required for data acquisition, and there are no files of dark frames or flats to manage. SCP is very tolerant of mount and drive imperfections and is reliable even on windy nights since additional readings can be easily taken; we have obtained high quality data in 20-30 knot winds, thanks to the CGE mount and our ability to switch between 5 and 10 second integration times on the Optec photometers (the art is in timing the wind gusts!). Our entire observatory can be run on a few (heavy) batteries, permitting data to be gathered uninterrupted all night. Finally, the joy of looking through the telescope at the stars directly and aligning them in the diaphragm is more rewarding than being glued to the computer screen waiting for an image to download and losing one's night vision. The immediate feedback of seeing the variable star and the comparison stars in the generous finder scopes is very assuring. Not being total Luddites, we are designing some new spectrographic hardware and presently employ our CCD/webcam equipment to take medium-resolution spectra (R~3000) of program stars as well as photographs of planets and deep-sky objects.
On Instruments for our Observatory A telescope focuses light onto a sensor! A mount keeps the light located on the sensor during the required period. The sensor yields quantifiable data regarding the intensity of light striking the sensor. All three components must function in-harmony to the standards required by the task at hand. For the amateur photometrist, the commercial equipment available today is amazing! We have been very happy with the products, dealers and manufacturers who have outfitted our observatory; this is because we matched the things we wanted to do with the equipment we bought! Specifically, the Celestron CGE1400 (14" f/10 and f/6.3) affords us the aperture to perform single-channel photoelectric photometry with the Optec SSP3 of stars to 12th magnitude (on really good nights) and acquire stellar spectra to 10th magnitude from the terrible skies of the Elkton site (Our book caricaturing the real-life events endured while observing from this site is pending!!!). The CGE mount was easy to learn, tracks exceptionally well and has been reliable under many adverse conditions. For remote work we mated a Vixen VC200L optical tube assembly to a used Meade LXD75 mount for making photoelectric measurements at the remote Shenandoah site. This has turned out to be a winning answer, yielding good tracking, sharp images and sufficient light-gathering power in these really dark skies - yes, we have indeed seen M33 with naked eye in 2006 and 2007! The Vixen telescope has an extremely flat field, making for stunning wide-angle visual views at f/9 and f/6. Thanks to Hands on Optics and to OPT Corp for all their help in assembling this amazing equipment which sends light to the Optec SSP3! Both Optec SSP and SBIG SGS instruments are very well made and produce reliable and repeatable accuracy over a wide dynamic range; and technical service is within an email's reach. The SSP3 was purchased in 1986 and was recently overhauled, and is still cranking out reliable counts in seven filter bands for us. Infrared work is done with the SSP4 to J and H magnitude of ~6 with good signal. The SBIG spectrograph gives us access to spectra of most of our program objects. We hear about photometry being the "poor-man's spectroscopy", and we recognize that both are essential for efficient gathering of stellar brightness data. At present, the SNR is higher for filtered single-channel photometry, so that occupies most of our observing time. Finally, the USER groups for all the above-mentioned products have been indispensable for helping us move up the learning curve. It is so helpful to connect with others who have toiled about a specific problem or situation that crops up when so many complex systems are strung together! We hope that folks will think hard about what they most want out of their equipment before making their purchases and encourage those who get discouraged to reach out for support - it is there!!!
Instruments
Celestron CGE 1400, Hurdman 4.25", and Vixen VC200L |
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Send mail to
bemccandless@earthlink.net with
questions or comments about this web site.
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