SkEye User Manual
Contents
1. DSC Support for encoder based Digital Setting Circles connected over Blue tooth is in the works Checkout the DSC test app in the Play Store Chapter 2 Magnetometer Calibration IMPORTANT Please read this section before using SkEye It is a sim ple procedure but a crucial one for the proper operation of SkEye on some phones Android phones are equipped with a device called a Magnetometer This device helps to determine the orientation of the phone relative to the Earth s magnetic field Similar to a compass needle but in three dimensions The magnetometer on some phones requires to be calibrated This needs to be done every time you use an app that needs the magnetometer 2 1 Calibration procedure The procedure is very simple and takes just a few seconds After starting the application wave your arm holding the phone in a figure 8 motion You may have to repeat this a couple of times This is best illustrated with a video If you can t click the link try search ing YouTube for best compass calibration method After doing so check whether North as shown in the app is approximately where you think it is If the sensors are not calibrated you will see really wild errors that are easy to notice 4 CHAPTER 2 MAGNETOMETER CALIBRATION 2 2 Substances that cause interference Since the operation of SkEye is affected by interference from metals it is worthwhile to understand this phenomenon in brief E2. ation buttons are dimmed 15 16 CHAPTER 4 USER INTERFACE 4 3 Catalog filters Only available in SkEye Pro Accessed via Menu gt Catalogs With filters you can choose which catalog objects are shown in the dis play based on their surface brightness and size In the case of Open Clusters magnitude is used instead of surface brightness 4 4 Double Tap to launch Menu Android has a dedicated menu button but on most phones this button requires a hard press which might disturb the telescope s or phone s alignment As an alternative you can double tap anywhere on the screen to bring up the menu Tapping requires less force than pressing a hardware button 4 5 Principal Orientation The default orientation of SkEye s main screen is portrait But if you prefer landscape you can change it via the Settings screen There is also an Auto mode which changes the orientation dynamically to match the phone s orienta tion but beware there is a noticeable pause while switching orientations 4 6 FOV angles The FOV angles in the horizontal and vertical directions are shown in the HUD and updated when you zoom in or zoom out or change the principal orientation 4 7 Sensitivity settings Each Android phone model has slightly different sensors types and sensitiv ity If you find the display is too jerky or too laggy SkEye lets you alter the sensitivity of each sensor Seen Appendix B for more details 4 8 SEARCH 17 4 8 Sea
3. e website vi PREFACE Chapter 1 Introduction SkEye is a planetarium for Android devices phones and tablets It can orient its view using sensors available on the device The unique feature in SkEye is that you can use your Android device as a PushTo guide for telescopes binoculars and other observing equipment 1 1 A note about Accuracy The accuracy of SkEye is affected by a number of factors both internal and external The external factors have the maximum effect and include the following e Accuracy of the phone s sensors and environmental effects such as sur rounding magnetic fields The effect of external factors can be mitigated to a large extent by multiple alignments Internally SkEye is yet to account for the following tiny effects e Atmospheric refraction which is most evident near the horizon e Proper motions of stars 2 1 2 CHAPTER 1 INTRODUCTION Operational Modes Hand held mode Users of Google SkyMap would be familiar with this mode It lets you quickly identify objects visible in the sky as well as search for them Virtual DSC This is the most innovative feature in SkEye It is the cheaper convenient and possibly less accurate alternative to encoder based DSCs After attaching your phone to the telescope OTA you can use it as a finder scope and a PushTo guide without any additional equipment Please make sure you read the detailed tutorial below before using it Bluetooth
4. ible and operable You will get best results if your telescope doesn t have steel tubes or mounts since they cause magnetic interference If they do try to attach the phone farthest from the metallic content Try to observe from a location where there is little magnetic interference for example keep away from electric poles and wires large buildings or steel railings 3 3 3 First Alignment Although in theory you need just one alignment you would be making about three alignments in practice Choose a bright and well known star planet for your first alignment Click Menu button Indirect Mode Add new Alignment You will see a list of objects sorted by their ease of viewing SkEye prioritizes objects by their current altitude and visual magnitude Chose one of these objects and a dialog will show up asking for confirma tion Not all metals are problematic Read the note on substances that cause interference CHAPTER 3 VIRTUAL DSC 5 01 PM Align the equipment to Mars Press Accept after completely aligned 3 3 TUTORIAL FOR VIRTUAL DSC 11 Now move your telescope so that this object is centered in the field of view Only then press Accept Keep the telescope stationary for a few seconds after clicking Accept The alignment is done To help you to center the star in the field of view you can use an illuminated reticule eyepiece If you don t have that you can use a high power eyepiece and defocus it so
5. ime application to verify system time accuracy See Appendix A for more details e Start the SkEye application e You will be prompted for your location when you first start the app Spec ify your precise location for maximum accuracy I recommend you use GPS to specify the location The locations you specify are remembered so you can use them quickly later 3 3 TUTORIAL FOR VIRTUAL DSC 7 If you specify the location manually note that the input is in decimal degrees Hence a latitude of 15 30 should be entered as 15 5 and not 15 3 You can use Google Maps to find the co ordinates of your location e Important Calibrate the magnetometer as described in the previous sec tion Now attach the phone to the OTA as described below 3 3 2 Attach to telescope e You need to attach your phone to the telescope s Optical Tube Assembly OTA such that the phone moves whenever the OTA moves See figure below for an example CHAPTER 3 VIRTUAL DSC 3 3 TUTORIAL FOR VIRTUAL DSC 9 You can use a phone jacket or case holster etc and attach the jacket permanently to the OTA That way you can plug in the phone quickly when needed To attach the jacket to the OTA you can use for example Velcro or two sided tape Checkout several ideas contributed by users on my website The direction in which you attach doesn t matter The type of mount doesn t matter either Attach in such a way that the display is conve niently vis
6. ments nearest to current location having more weight TIP Here is a typical observation session Let s say I have made the first alignment to Sirius Now I try to find M33 But first I will check the alignment in this direction I see that there is a nearby star called Mirach I get it into the FOV and observe that Mirach is slightly off center on the phone I Insta Align to it When I push to M33 using SkEye I see it right in the center of the FOV 3 3 TUTORIAL FOR VIRTUAL DSC 13 I can now find several objects in this part of the sky without checks or alignments When I move to another part of the sky it is time to check the alignment with a nearby bright star and Insta align if needed 14 CHAPTER 3 VIRTUAL DSC Chapter 4 User Interface Here is a walk through of the main user interface of SkEye 4 1 Features There are many features packed inside SkEye some of which may not be im mediately obvious I recommend reading or at least skimming through this section once 4 2 Color themes The night color theme is designed to preserve dark adaptation Accessed via Menu Change Color Theme There are actually three color themes to chose from e Day No color filtering display brightness is kept normal e Dusk Green and Blue colors are filtered by 50 display brightness is kept normal Android navigation buttons are dimmed e Night Only Red color shows through display brightness is kept at min imum Android navig
7. planetarium realtime co ordinates bulls eye reticle intuitive search handheld and telescope modes SkEye User Manual A How to guide and reference for SkEye Harshad R J 11 Contents Preface v 1 Introduction 1 1 1 A note about Accuracy sino dw de we oes 1 1 2 Operational Modes s sosa s onde OR Ee we OR OM 2 2 Magnetometer Calibration 3 2 1 Calibration procedure y varada aan eee 3 2 2 Substances that cause interference 4 3 Virtual DSC 5 3 1 Advantages over a real DSC 20 00 0000 0 0 0 5 3 2 Disadvantage as a Ae DAA Ge naeh 5 3 3 Tutorial for Virtual DSC nw eo eee ee eRe o 6 3 3 1 Prepare your phone 4 664624 86644 464 4 6 332 e se bac er Be Soe HG AK ees 7 333 First Alignment 3 Ka RA 2er OSE EH DEO EH 9 3 3 4 Adding more Alignments 11 4 User Interface 15 4 1 Features sc ae oo ae bo See A 15 4 2 Color themes A E eS A 15 4 3 Catalog filters orina a a Soe RR ANG 16 44 Double Tap to launch Menu aaa aa 20 44 400 16 45 Principal Orientation oi is Hoe be HEH BE EE 16 iv 4 6 FOV angles 4 7 Sensitivity settings sus 306 AS Search o ogera we Ge a OR Hk OA Hs 4 9 Manual mode 4 10 Misc Features 4 2 05 5 2a 4 wa 5 Appendix A Managing system time 6 Appendix B Adjusting Sensitivity CONTENTS Preface This document was written for SkEye version 6 6 in the summer of 2014 Get the latest updates from SkEy
8. rch You can search for any of the objects in SkEye s database Click the search button or invoke via Menu Search After selecting the object to search an arrow is shown to guide you the target Also shown are the Alt Azm and RA Dec co ordinates and the delta angle between the current position and the target 4 9 Manual mode When you drag your finger on the main display SkEye switches to manual mode You can move the view around by single touch gestures You can even zoom and rotate the display with multi touch gestures Click the Back button to return to normal mode Or click the Align button to align to the highlighted object if you are using it with a telescope 4 10 Misc Features Precession of the equator calculated to arc minute accuracy Alt azimuth and Equatorial grids Real time Alt Azimuth RA HA Dec coordinates Complete Messier catalog e NGC Catalog e The Free version has a subset of NGC the most prominent 200 NGCs e The Pro version has the complete NGC and IC catalogs Intelligent positioning of labels that avoids overlap e Pinch to zoom in and zoom out twist to rotate the view 18 CHAPTER 4 USER INTERFACE e Major star names e Constellation lines and labels e Multiple locations that are saved between sessions Chapter 5 Appendix A Managing system time The accuracy of phone s system time is important for all planetarium apps It is especially important in the case of SkEye since it use
9. s real time object locations for alignment If the time is wrong by a few minutes the errors add up Sometimes up to several degrees of bearing Normally Android doesn t let applications change the system time There are basically two choices to the user for setting the system time e Automatically set to network provided time the mobile carrier network not the Internet The problem with this is that the network s time may not be accurate or may not even exist in certain parts of the globe e Set to the time manually The problem with this is that the timer may drift over a period of time So you will have to periodically check and reset the clock To check how accurate your system time is you can use a GPS app or the Clock Sync app former uses GPS time while the other uses the Internet to access the atomic time 19 20 CHAPTER 5 APPENDIX A MANAGING SYSTEM TIME I recommend the Clock Sync app If you have a rooted phone this app can automatically sync the system time to the atomic time If you don t have a rooted phone the app pops out notifications when the phone s time drifts too far from the atomic time Chapter 6 Appendix B Adjusting Sensitivity How to adjust the sensitivity of the display First start SkEye and calibrate the sensors with a figure 8 motion Now observe the display for a few seconds In case of too much jitter keep the phone on a level surface e If the jitter is such that the displa
10. sy no wires batteries etc 3 2 Disadvantage Possibly less accurate than a real DSC The source of the inaccuracy is in the magnetic field measurement Magnetometers sense the direction of Earth s magnetic field to provide ori entation There are various errors introduced at this stage 5 6 CHAPTER 3 VIRTUAL DSC e The Earth s magnetic field itself is not consistent It varies from place to place and time to time quite unpredictably The major components of the variation are more predictable and taken care of but smaller compo nents aren t e There is often some magnetic interference from the environment such as large metal structures electric circuits underground metal deposits and so on e Some phones induce a magnetic field around themselves affecting their own sensors In spite of all these caveats I have found this method to be accurate to about 15 arc minutes with single point alignment With two or three alignment points accuracy can be improved further to about 8 arc minutes Complete accuracy is possible under ideal conditions 3 3 Tutorial for Virtual DSC Since SkEye is the only application that I know of with a Virtual DSC feature am writing a detailed step by step guide for using it It s actually quite simple once you get familiar with it 3 3 1 Prepare your phone e Make sure the phone s system time is accurate to within a minute if not seconds You can use for example the Navy T
11. that the star appears like a blob Centering a large blob of light is easier than centering a pin point source of light In the alignment screen click Return to get back to the planetarium view The object you selected in the previous step should now appear in the center of the cross hairs If you move the telescope now you will see the display changing in tandem You can now try finding a few objects or do more alignments as described in the next section 3 3 4 Adding more Alignments You can add more alignments by repeating the procedure above but SkEye offers a quicker way to do this Insta Align Here s how you use it Slew your scope to find another bright object If there is a difference be tween the scope s view and the planetarium s view you can simply drag the view until it is centered in the cross hairs The words Insta Align will be shown along with a couple of buttons as in the figure below 12 CHAPTER 3 VIRTUAL DSC Once the object is centered press the button and you are done As a further shortcut SkEye will show a button to align to the nearest object For example the Align to Pollux button in the figure This is handy and more precise than relying on your eyes to match the cross hairs To cancel the alignment procedure you can click the red X button or simply move the telescope away You can add as many alignment points as necessary SkEye uses a weighted average of the alignment points with the align
12. very substance interacts with ambient magnetic fields such as the Earth s magnetic field in a unique way Their level of interaction is measured by the relative magnetic permeability of the substance Higher the value the more the substance distorts ambient magnetic fields The relative permeability of some materials can be found in this wikipedia article Among the commonly found materials the following are cause for concern to us e Iron e Nickel e Cobalt e Alloys of the above For example Steel All other materials don t pose a problem Examples are e Aluminum e Copper and it s alloys like Brass e Wood Plastic and most of the other commonly found substances The latest versions of SkEye show a warning if abnormal magnetic fields are detected This warning may only be shown in certain directions When you see this warning you should consider shifting the device to a different location Chapter 3 Virtual DSC DSC stands for Digital Setting Circles These are typically implemented using optical or magnetic encoders in the mount It is quite accurate typically within 5 arc minutes on an amateur setup but it is costly and cumbersome to install In contrast the Virtual DSC mode in SkEye uses only the sensors on your device to guide the planetarium view 3 1 Advantages over a real DSC e Cheaper if you already own an Android device e Isn t affected by mounting errors e Quicker to install and get started e Less mes
13. y rotates around the Nadir then you need to reduce sensitivity of the magnetometer e If the jitter seems random then you need to reduce the sensitivity of the accelerometer On the other hand if there is too much lag determine the direction of the lag e If there is a lag when moving along the horizon azimuth change you need to increase the sensitivity of the magnetometer e If there is a lag when going from horizon to Nadir altitude change then you need to increase the sensitivity of the accelerometer 21
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