Book contents
- Frontmatter
- Contents
- List of Illustrations
- Preface
- Acknowledgements
- 1 History and development of the 20-cm Schmidt–Cassegrain
- 2 First observation – the Moon
- 3 Planets, double stars and other bright things
- 4 Deep sky
- 5 A Couple of Interesting Problems
- 6 Some accessories for the telescope
- 7 Observing with friends
- 8 Projects
- 9 Photography
- 10 Photometers, computers, image intensifiers and television
- 11 Afterword
- Appendix 1 Sources of further information
- Appendix 2 How to align the polar axis with the Earth's axis of rotation
- Appendix 3 Collimation of an S–C telescope
- Appendix 4 Cleaning the corrector plate
- Appendix 5 Mount vibrations
- Appendix 6 Field operations packing checklist
- Appendix 7 Astronomical nomenclature
- Appendix 8 Catalogue of bright stars & interesting things
- Appendix 9 Catalogue of nearby stars
- Appendix 10 Messier Catalogue
- Index
Appendix 2 - How to align the polar axis with the Earth's axis of rotation
Published online by Cambridge University Press: 05 August 2012
- Frontmatter
- Contents
- List of Illustrations
- Preface
- Acknowledgements
- 1 History and development of the 20-cm Schmidt–Cassegrain
- 2 First observation – the Moon
- 3 Planets, double stars and other bright things
- 4 Deep sky
- 5 A Couple of Interesting Problems
- 6 Some accessories for the telescope
- 7 Observing with friends
- 8 Projects
- 9 Photography
- 10 Photometers, computers, image intensifiers and television
- 11 Afterword
- Appendix 1 Sources of further information
- Appendix 2 How to align the polar axis with the Earth's axis of rotation
- Appendix 3 Collimation of an S–C telescope
- Appendix 4 Cleaning the corrector plate
- Appendix 5 Mount vibrations
- Appendix 6 Field operations packing checklist
- Appendix 7 Astronomical nomenclature
- Appendix 8 Catalogue of bright stars & interesting things
- Appendix 9 Catalogue of nearby stars
- Appendix 10 Messier Catalogue
- Index
Summary
The object of this exercise is to make the telescope's polar axis parallel to the Earth's rotation axis. Like a theological problem, there are many different paths to accomplish this. Like a theological problem, you will find people arguing incessantly as to the best method. The precision and detail of polar alignment has been taken to a fine art. There is probably a method described in your owner's manual. I will present another one here. You may wind up inventing your own.
Contrary to popular belief, the tripod does not have to be level, although this makes adjustments easier. Note; severely leaning tripods can tip over.
The question arises as to how accurately you should align your telescope. Greater accuracy in alignment requires more setup time and this is time which might have been spent observing. Clearly, spending an hour and a half aligning the telescope to observe the Moon visually at low power is excessive. On the other hand, if you're looking for Messier objects using the setting circles then a bad polar alignment is going to cost you search time every time you point the scope at blank sky and have to hunt around for a few minutes for each object. If you've just rolled the telescope out for a quick visual Lunar session while your spouse finishes dressing for an evening out, get within five degrees of the pole and start observing.
- Type
- Chapter
- Information
- The 20-cm Schmidt-Cassegrain TelescopeA Practical Observing Guide, pp. 223 - 231Publisher: Cambridge University PressPrint publication year: 1994