Time: 7:30 – 9:00 PM
- Set up and Socializing (7:00 – 7:30)
- Welcome & Current Happenings
- Featured Presentation
- Members available for questions
- Snacks provided
Astrophotography Using Single Reflex Lens Digital Cameras
By Steve Grimsley
Modified versions of commercial digital single lens reflex cameras (DSLR’s) dedicated specifically for astrophotography, enable the capture of quality images of a wide variety of astronomical objects. The moon, eclipses, transits, planets, comets, deep sky Milky Way, supernova, and galaxies can all be photographed. They can be used with a camera lens or, best of all, mounted prime focus on telescopes. Although not the absolute best cameras for every object, DSLR’s are the most versatile means to acquire photos of the widest variety of astronomical targets. A welcome benefit that you will find with this method of astrophotography is the ability to alternate between visual observation and imaging quickly and with great ease. With a computerized mount and camera control constant monitoring of an imaging run isn’t required freeing you to visit with friends and look through other telescopes during star parties. This presentation will review the procedures and processing steps that I have used for a number of years. After the capture method has been discussed a number of examples of dozens of objects will be shown both on the screen and in hardcopy mounted prints. The astro-photos are presented in a progression from nearby solar system out to distant galaxies. Hopefully, many of your favorite visual objects will be shown. The techniques presented maybe useful to beginners and to those who already have experience in astrophotography.
Collimation of a Schmidt-Cassegrain using “GoldFocus Plus Collimation System”
By “Rev” (i.e. Bill Wick, Norwich University Chaplain)
“Collimation” (“collinear” or ‘in-line) means that all optical elements of a telescope are centered and square to its optical axis and its imaging system. Lenses must be accurately spaced; primary and secondary mirrors must be accurately separated and aligned; focal reducers, field-flatteners, field correctors and focus draw tubes require accurate alignment (centered/moving parallel to the optical axis); additionally, filter holders need to be well-centered. NOTE: the mirror grinding error on the Hubble Space Telescope (HST) primary mirror (later fixed and subsequently serviced by four Space Shuttle crews) was off as little as 4 micrometers (microns) at the edge of a 2.4 meter (94.5 inch) mirror.
A number of collimation options exist including (but not limited to):
1. “By Eye” or “Star Collimation” in which one relies upon experience and judgment to achieve good collimation (making a star image as small, round, and sharp as possible. This technique is subjective with accuracy diminished by diffraction limits and atmospheric conditions.
2. “Defocused Star” or “Concentric Ring” Collimation utilizing a defocused star image is used for telescopes having a secondary mirror obstruction (e.g. [Newtonian] reflectors or catadioptrics [Schmidt-Cassegrains]) whereby in the presence of poor collimation a severely defocused star image shows an elongation or off-center distortion. One adjusts the secondary mirror so as to make the defocused star image as round and symmetric as possible. This technique is also subjective (it can be a difficult to visually determine when the defocused star image is perfectly round and symmetric).
3. Cheshire (external light source) and/or Laser Collimation (built-in laser) employs instruments whose accuracy is limited to one or two millimeters and by the accuracy of alignment in the eyepiece holder.
“Rev’s” presentation will highlight the “GoldFocus Plus Collimation System” he uses for focusing and collimating his Celestron 11″ SCT. The system involves a GoldFocus Plus Collimation Mask and Analysis Software which measure collimation in the same way a CCDcamera forms its image with the requisite accuracy for high quality digital imaging. GoldFocus Analysis Software displays the objective measure of an image’s quality of focus and collimation on one’s computer screen in real-time. NO GUESSWORK – focus and collimation qualities are objective and accurate – neither limited by diffraction limits nor conditions. This system (mask and software) ensures proper focus and collimation (in the exact way that one’s astrophotography imager sees.
Mars – Summer Viewing 2018
Part 1 of 2
By Gary Nowak
Of all the planets visible; Mars is surely the one that has cultivated the most human imagination and interest. Every 2 years and 50 days, Mars and Earth have “close encounters” with each other. Approximately every 15.7 years, Mars has a closer than typical approach to Earth. In the summer of 2018 Mars will have one of these closer approaches called a Perihelic Opposition (described in more detail in the talk). At that time, amateur size telescopes will have some reasonable views of Martian surface features. Mars is the only planet in our Solar System (besides Earth of course) that we have a reasonable chance of seeing the actual surface features (the Moon doesn’t count- it’s a moon). Several major Martian surface features are readily visible in a good telescope. Mars is a dynamic planet with surface features that show subtle changes over time due to the effects of the Martian atmosphere. The Martian atmosphere itself displays changes, such as cloud formations and the occasional dust storm. Changes to the Martian ice caps usually can be easily seen. This talk is designed for visual amateur observations through telescopes of 4″ – 8″ aperture and will cover all aspects of observing Mars. Observing tips and techniques will be shared to help bring out the most of your telescope observations of Mars.
Part 1 Outline:
A. Introduction to Mars
B. Mars Quiz ( History of Mars and Mankind)
C. Mars Orbital Characteristics
D. Factors affecting Mars Observations: Atmospherics
Part 2 Outline (April 2018):
A. Factors affecting Mars Observations: Instrumental
B. Amateur Telescopes for Visual Mars Observations
C. Filters for Mars
D. Observing Mars: Survey of Various Visual Features
E. Changing Mars Phenomena: Atmospherics
F. Mars Moons
The presenter; Gary T. Nowak is a long time member of the VAS and is on the board of directors. His specialty is advanced visual amateur astronomic searches with telescopes and binoculars. The presenter has built several telescopes over the years which included grinding and polishing his own telescope mirrors. His first recorded observations with a telescope were in 1968. He has been observing Mars since 1971. In 1999, he co – discovered a Nova visually with binoculars. He is a member of the Association of Lunar and Planetary Observers (ALPO).
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