- Details
- Written by: Ray Oltion
- Category: RoGarOn Observatory
- Hits: 19
0.1 Optics
-
Telescope
-
This is a TPO 254 mm (10 inch) f/8 Ritchey Chretien I purchased through Oceanside Photo and Telescope in 2015. It has a focal length of 2000 mm and a back focus distance of 288 mm. The OTA weighs 35 pounds. This optical design provides less distortion off-axis. I also wanted to avoid SCT designs that incorporated a glass corrector element. In retrospect the extra cost and effort in collimating this system make it a questionable investment. Also, for a portable system that I have to erect by myself when camping, it is at the limit of my physical capabilities.
-
Focal reducer
-
This might be useful for measurements where comparison stars necessitate a larger field of view. So far I haven’t found a need for it.
-
Filters
-
My belief that the Sloan filter system is superior led me to purchase several of them, but I realize that the Johnson/Cousins system has a huge following. To that end I decided to build my own J/C filters from colored glass filters by combining various colors, with appropriate UV /IR cut filters. I have the filters and the spanner wrench to stack them into standard 1.25 inch filter rings, but haven’t done this yet. There is a description online of which filters to use for the various J/C passbands.
-
Sloan g’, r’, i’ 1.25 inch interference filters
-
J/C v, g, r, b: Do-It-Yourself from 1.25 inch colored glass filters
-
No. 47 Violet
-
No.38A Dark Blue
-
No.56 Green
-
No.12 Yellow
-
No.23A Light Red
-
UV / IR Cut
-
-
Narrow band H-alpha and H-beta: I bought these for their potential science use in determining stellar temperature. I wanted the Stromgren filters for this purpose, but these are not widely available or affordable.
-
Star analyzer diffraction grating for slitless spectroscopy.
-
-
On Axis Guider mirror
-
This dichroic mirror from Innovations Foresight splits the light into visual and infrared beams. I bought it for guiding when performing spectroscopy, but so far haven’t used it. I don’t have a suitable guide camera for it. It might be useful for photometry, but with adequate polar alignment and relatively short exposures, it seems to be too much hassle with little advantage.
-
Field camera lens
-
This is a camera lens that screws into the filter wheel of the QSY camera, which provides a wide field of view for a finder. It sits piggyback on the TPO telescope tube via a pair of Losmandy rings.
-
Eyepiece
-
I have a 2” eyepiece for visual observing, but I rarely use it, as it requires a completely different setup on the telescope, and re-balancing the system, a laborious task that I don’t want to perform any more often than necessary. If I was a strictly visual observer, I would set up the system that way for a whole observing session, but that isn’t my area of interest. I am not even interested in capturing pretty pictures with my cameras. Images from my wide field finder camera might be useful for documentation, but they are not intended to wow the viewer.
0.2 Imaging
-
CCD camera
-
The QSI 632 is a cooled monochrome system with an integrated 5 position filter wheel. Its specifications are:
-
Pixel dimensions (microns) L:6.8 W: 6.8
-
Well depth: 55,000 e-
-
Imaging field dimensions (pixels) L:2184 W:1472
-
Readout noise: 7 e-
-
-
CMOS camera
-
The QHY 183M is a cooled monochrome camera. I paired it with an seven position filter wheel. Its specifications are:
-
Pixel dimensions (microns) L:2.4 W:2.4
-
Well depth: 15,500 e-
-
Imaging field dimensions (pixels) L:5544 W:3694
-
Readout noise: 2.7 e- low gain, 1.0 e- high gain
-
-
Focuser
-
I use a Starizonia MicroTouch motor driven Feathertouch focuser for controlling image sharpness. It has a limited travel range, so I must adjust the image path length with rings of various thickness which attach to the back of the telescope tube assembly.
-
Spectoscope
-
I purchased a spectrometer from Science-Surplus that employs a fiber optic cable to feed the spectrometer. It has a Czerny-Turner design with a 1800 lines/mm reflection grating. The spectrometer outputs a stream of counts for wavelengths over the 430-660 nm range of the instrument. This data travels to the computer via a serial port and is displayed by a program, which also controls the spectrometer for data capture. I haven’t been able to capture any spectra of stars with it, other than Alpha Lyra. It is difficult to position the star image on the fiber optic cable end. That is one reason I purchased the off-axis guider mirror, to enable me to image the star with a camera on the IR beam, and capture the visible light beam in the fiber optic cable. This is a challenge for the future.
0.3 Mount / Observatory
-
Mount
-
The ASA DDM60 is a direct-drive German equatorial mount manufactured in Austria. It has a maximum load limit of 25 kg and weighs 19 kg excluding the two counterweights. It offers advanced control and superior tracking. It is a complex system that is rather finicky and dependent on the driving software. It seems to be sensitive to balance, and will drop out when guiding. It also seems to lose USB contact at random times, possibly due to Windows interrupting the system to check for updates. The mount also does not directly support azimuth adjustment, but instead has four thumbscrews that rock the mount on a central ball support. Supposedly this allows both azimuth and altitude adjustment, but I haven’t figured out how this works. The mount includes an integrated laser pointer, which seems to be pointed to the offset for Polaris. All in all this mount has been challenging to use.
-
Tripod
-
When I purchased the system it was to be portable, so I got the Losmandy HD tripod which is designed for their G-11 mount. It is very robust and has vibration dampening shoes for the feet. It uses an adapter plate to connect to the ASA mount. This adapter plate does not allow for azimuth adjustment. Consequently, accurate polar alignment is challenging.
-
Azimuth rotating ring
-
To solve the azimuth alignment problem, I built a rotating ring that the tripod sits upon to allow fine adjustments in azimuth. This may introduce flexure in the system unless the ring is very well supported upon the ground. It does allow for very fine nudges in azimuth, perhaps down to several minutes of arc. I might try to incorporate azimuth adjustment into the adapter ring between the tripod head and the mount, but this is a metal fabrication project for the future. Then I would eliminate the rather clunky ring system on the ground.
-
GPS receiver
-
This device plugs into a USB port on the observing computer and provides accurate time as well as position information. This allows the pointing software to accurately determine the location of target stars. Since the whole data acquisition system was designed to operate at remote sites, it does not require Internet access.
-
Computer
-
This is a windows based system with two ultra-widescreen monitors. It operates on 12 volts and incorporates solid state drives for data storage. It uses a wireless keyboard and mouse.
-
Power
-
The observatory relies upon two 50 watt solar panels and two 100 amp-hour lead-acid storage batteries. It employs a 300 watt pure sine wave inverter to supply power to the various components. I originally bypassed the 120 volt transformers supplied with the components and built my own 12 volt power supply with appropriate connectors, but ran into ground loop problems when disconnecting the equipment, which burned out a component in my QSI 632 camera. Their engineers advised me to use the 120 volt transformers and the inverter, even though it is less efficient, since they designed the system to operate with that power source.
-
Tent
-
I used the Kendrick observatory tent, which has two rooms, one with a zip-out roof for uncovering the telescope, and a partition which separates it from the control room. The tent came with a rain fly. The tent suffered damage from wind and blowing sand when I used it in the Arizona and New Mexico deserts, and is now only partially functional. The zippers wore out with the sand, and several of the aluminum support rods broke due to wind pressure. The rain fly ripped in various places and essentially shredded. The tent fabric rubbed on the equipment inside and wore several holes in the walls. Maybe if you consider tents as consumables it served its purpose, but it only lasted a few months.
-
Hexagonal enclosure
-
I designed a modular enclosure consisting of 1/8 inch 4x4 foot hardboard panels around a hexagonal base. Triangular panels above each wall panel formed the peaked roof. The roof panels were fixed together and could be moved aside onto rails to expose the telescope for observing. Alternatively, the triangular panels could be hinged on each wall panel to fold down, like petals on a flower. I built a prototype system and used it sporadically at my home to test its utility, but never did deploy it in the field, although it was designed to be taken apart and erected while camping. I wanted something with hard sides to resist wind pressure while camping in the desert.
0.4 Software
-
Operating system
-
Since the ASA mount software runs on Windows only, that is what I used on the observing computer. Windows is not my operating system of choice, and I have used Linux for many years. I have found numerous other astronomy applications in Linux for various functions, but the mount software ties me to Windows.
-
Mount control
-
The mount must be controlled by the computer, and the AutoSlew/Sequence software to do that is very advanced and more geared to scientists than amateurs. It contains many options for adjusting mount parameters and closely monitors motor current levels. It will drop motor power if it encounters a surge in motor current, which could be due to an obstruction. However, it seems to be sensitive to imbalances in the telescope tube and image acquisition system, not only on the telescope imaging axis, but perpendicular to that as well. The software facilitates balancing the system via current measurements in the motor when moving the mount back and forth in RA and DEC. This may be the best way to balance a telescope and imaging system that I have ever found. The ASA company to my knowledge does not offer upgrades to the software, so I have had a continual struggle with this system and probably should have reached out to OPT for help after I purchased the system from them. The software might be the weak link in an otherwise superior drive. Maybe it is just too complex for me to understand, and the manual does not offer enough insight to overcome these problems.
-
Image acquisition
-
I bought my system through OPT and they recommended Maxim DL for controlling the QSI camera. It doesn’t work well with the QHY camera, so I use the EZCAP QT program for my finder images. Maxim DL works okay but I am not a fan of proprietary software. Consequently the version I have of this program is ancient, which may be why it doesn’t like the QHY camera. I just use Maxim DL for acquiring images, and don’t use it for calibration or measurement. There are probably better open-source programs for image acquisition in the Linux environment, and I would use them were it not for my mount software tying me to Windows. That being said, in a dual-boot environment, I could process all the images from an observing session with my Linux tools, or store the images on a server and access them with a Linux-only system.
-
Focusing and pointing
-
FocusMax is useful for finding optimal focus via software control, which does so via a V plot of the star image size relative to the motorized focuser position. It also combines this function with algorithms that compute distortions in your optical system, which can improve pointing accuracy. This software can also compute polar alignment adjustments in altitude and azimuth for precise centering of the equatorial mount on the celestial axis.
-
Planetarium and mapping
-
I use Cartes du Ciel / Skychart for my main sky visualization software. It combines great charting capabilities with the ability to overlay the camera field of view. It can also connect to the mount to drive the telescope to selected objects.
-
Observation planning
-
My favorite system is Deep Sky Planner, even though it is proprietary and runs in Windows. It contains numerous databases for objects of various types and calculates optimum observing times for them based upon your location. It also allows you to log your observations. It interfaces with Cartes du Ciel and the mount, so it is possible to point the telescope through the planner program. This is handy when you have an observing plan set up for the night, as you can just step through the objects as they enter their optimal viewing window. I also purchased AstroPlanner, which also runs in Windows. It has some nice features, such as showing the Moon phase and dark time in a graph, and generates simple star images for your field of view.
-
Image calibration
-
The free and open-source AstroImageJ package contains efficient tools for calibrating images. This can be done with a single button push for a whole series of observations. It also offers tools for image stacking and measurement. It will plot light curves, too. However, since VPhot includes the AAVSO comparison stars, that might be my preferred tool for measuring variable star magnitudes. I also have an old copy of Richard Berry and James Burnell’s AIP 4 Windows, which is a Swiss Army knife collection of image processing tools, and includes a thick hardbound book with lots of theory. I haven’t used this software in years, but it might still be great for some purposes.
-
Plate solving
-
The Astrometry.net system works well and provides plate-solved images with global coordinates, which is important for registering images with photometry applications like the AAVSO’s VPhot. This system will run offline if you download the database files, but it can be tricky to set up the astrometry server, and the data files can be huge.
0.5 Conclusion
My brother is an amateur astronomer who does strictly visual observations. He also builds telescopes and writes about them for Sky and Telescope magazine. He advised me to start simple when I first considered purchasing a telescope system. Maybe I should have taken his advice. I spent probably 25 thousand dollars for a system that I have used very little over the last ten years. I still have an interest in amateur science oriented astronomy, and maybe I can overcome the problems I have encountered and still get some enjoyment from my investment. Would I do it again? Probably not, at least in the form I chose. If I had a permanent observatory maybe I could set it up and just use it. I don’t, and the older I get the less appealing camping in the desert becomes, and the worse my memory is for all the details involved in keeping such a system running. Simple might have been best in the long run.

- Details
- Written by: Ray Oltion
- Category: RoGarOn Observatory
- Hits: 1846
Teaching astronomy for Sheridan College gave me the opportunity to prepare a laboratory activity that determines key characteristics of the open star cluster NGC 957 in the constellation Perseus. I wrote a detailed instruction manual for my students which you can view here: Star Cluster Photometry Instructions. You can also view plots of the color indexes, magnitudes, and temperatures at this site: Star Cluster Photometry Plots
The H-R diagram I created for the star cluster NGC 957 shows possible interpretations for the evolutionary stages of stars in the cluster. (Click on the article title to view the image and read the full text.)
- Details
- Written by: Ray Oltion
- Category: RoGarOn Observatory
- Hits: 3440
Riding out a 50 mph windstorm in my observatory tent convinced me that for desert camping, a hard-sided structure would be worth the effort. Inspired by the HexaYurt structures popular at Burning Man, my goal was to create a structure that would be easy to take apart and reassemble when moving from one campsite to the next. Rather than adhesive tape, machine screws and metal flashing would hold the panels together. The whole thing would break down into 4 foot panels that could be loaded into the bed of my pickup truck, and leave enough room for my telescope equipment and solar panels.
Click on the article title to read more and view additional images --> Hexagonal Observatory
- Details
- Written by: Ray Oltion
- Category: RoGarOn Observatory
- Hits: 3622

- Details
- Written by: Ray Oltion
- Category: RoGarOn Observatory
- Hits: 3924
One of the exercises in a CHOICE course on how to use VStar, a neat variable star analysis tool provided by the AAVSO, was to use the Leavitt's Law plugin to calculate the distance to Delta Cephei. The following was my response, and it led to an interesting study of how we use Cepheid variables to compute distances to star clusters and galaxies. We might expect this to be cut-and-dried in our era of space-based astronomy, but it turns out to be "not so".
I downloaded data on Delta Cep from the AAVSO data download portal, not from the VStar menu that loads data from the AID, mainly because I wanted to store the raw data file locally. That means there was no associated period information from the VSX. With my new skills at determining periods with DCDFT, it was easy to narrow down on the period, first between 2 and 6 with resolution 0.01, which reported a top hit of 5.37 days, and then with a narrower search from 5 to 6 with resolution 0.001 days, which reported a period of 5.366 days. Using that with Leavitt's Law yielded a distance of 273.16 parsecs.
To find the distance of Delta Cephei, my Patrick Moore's Data Book of Astronomy was my first choice, but that didn't list a distance, only magnitudes and period. My next choice was Cartes du Ciel, the star mapping and planetarium software that is my favorite. It didn't list the distance either, but provided a link to Simbad. The Simbad page loaded lots of information on the star, but not the distance, until checking the distance box in the Measurements area yielded the following: 0.244 kpc, which is 244 parsecs. This compares fairly well with my calculation using Leavitt's Law, to within about a 12% error. That seems somewhat excessive, especially since Del Cep is the prototype star for this class of variable.
The problem seems to be calibrating Leavitt's Law to absolute distances, not the relationship itself. That is assuming you are using the right type of Cepheid, as there is a difference between two "overtone modes". This website explains how the Hubble Space Telescope used highly precise parallax measurements to determine distances to 10 nearby Cepheids to better calibrate Leavitt's Law. This sounds paltry, but Cepheids are relatively rare and there just aren't many that are close enough to measure by parallax. Hubble measurements claim an accuracy of better than 10%, though. Hubble also measured 10 Cepheid variables in the Large Magellanic Cloud and found the slope of the linear relationship between logarithmic period and luminosity to be very close, assuming that all of those variables are at about the same distance from Earth. The calculated distance to the LMC is about 49.4 kpc, which puts it outside the diameter of the disk of the Milky Way Galaxy, which is about 100,000 light years, or 30,674 parsecs, calculated by dividing 100000 ly by 3.26 parsec per ly.
Since Leavitt's Law calibrates to absolute distances via an assumed distance to the LMC, this can lead to a rather knotty problem of chicken-and-egg origins. Current estimates of distance to the LMC from various sources, described in this excellent lecture notes webpage, put the distance from about 44 to 51 kpc, a variation of about 15% from the average of the two estimates. So now we see where the uncertainty comes from. We just can't do any better for now.