Details

Written by: Ray Oltion

Category: RoGarOn Observatory

Published: 24 March 2025

Hits: 133

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.