Observatory

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 we use 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 BVRI and JH data than ever and so we have expanded our list of reference stars - thank you to the good folks up there!

We are relatively new to quantifying CCD astronomical spectrographs - our data reduction methods are still being developed.  In addition, our Elkton site is so light-polluted that deep-space spectra are contaminated by sodium/mercury emission and broad-band sources.  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 single-channel photometry (SCP) over CCD photometry for bright objects.  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  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  spectrographic and polarimetric 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 photosensitive element, the sensor, which permits quantification of the received light.

A telescope mount keeps light focused on the sensor during the required interval.

The sensor yields a reproducible measurement of the intensity of the light received during the interval.

All three components, the telescope, mount and sensor, must function in harmony with the standards required for  the task at-hand.  For the amateur photometrist, the commercial equipment available today is quite amazing!  We have been very happy with the products, dealers and manufacturers who have outfitted our observatory, and we feel this is primarily because we let the the things we want to do dictate the equipment we obtained.  All too often we read and hear about folks taking the approach of buying equipment  and then finding a use for it, which typically ends up with the equipment falling into disuse.

For our work, the Celestron CGE1400, operating at either f/10 or f/6.3, affords us the aperture to perform single-channel V band photoelectric photometry with the Optec SSP3 of stars to 12^th magnitude (on really good nights) and acquire stellar spectra to 10^th magnitude from the terrible skies of the Elkton site (A book caricaturing the real-life events endured while observing from this site is pending!!!).  We also use an Optec SSP4 to measure the near infrared magnitudes of our targets, and routinely achieve 10 milli-mag precision in J and H bands for targets with J magnitude as low as 4^th magnitude.  The CGE mount was easy to learn, tracks exceptionally well and has been reliable under many adverse conditions.

For supplemental and remote work we mated Vixen VC200L and VMC260L optical tube assemblies to Meade LXD75 mounts for making photoelectric measurements at either site.  This allows making simultaneous photometric measurements in multiple bands or simultaneous photometric and spectrographic measurements.  With some attention spent on the mechanics of the very affordable LXD mount, this system has turned out to be a winning answer, yielding acceptable tracking, sharp images and sufficient light-gathering power to obtain photometric data at 5 milli-mag precision from both sites.  The Vixen telescopes have extremely flat fields, making for stunning wide-angle visual views as well. Thanks to Hands on Optics and to OPT Corp for all their help in assembling this amazing equipment which is dedicated to sending light to the Optec SSP3 in BVRI and Wing ABC bands!

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 - it is still cranking out reliable counts in seven filter bands for us: BVRI and Wing ABC.  Infrared work through the 14-inch telescope is done with the SSP4 to J and H magnitude of ~6 with acceptable signal-to-noise ratio.  However, we have found that the most stable and reproducible results are obtained on the coldest nights.  The SBIG spectrograph gives us access to spectra of most of our program objects with a modest half-hour set-up time.  We do hear about photometry being the "poor-man's spectroscopy", and we recognize that both photometry and spectroscopy are essential to truly quantify stellar brightness over a wide energy and intensity range.  At present, we obtain the highest SNR with rapid turn-around for SCP, so that still occupies most of our observing time.

Finally, it is important to acknowledge the USER groups for all the above-mentioned products, which 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 (with Hurdman 4.25" in middle), and Vixen VC200L and VMC260L on Meade LXD75 mounts