Installation

indi_celestron_aux is not included with indi-full by default. It is a new separate driver and at the moment must be installed from source. You can install current version of the driver from the Nightly INDI PPA. for Ubuntu 16.04 or newer. It will probably migrate int main PPA at next release. This driver is a full replacement for the NexStar Evolution driver which will be discontinued in the near future.

Warning: This is a new, beta-quality driver and should be treated as such. There are no known functional issues with it and only one long-runtime-stability issue. Nevertheless, the driver should not be left operational unattended.

Requirements

For building the driver you need standard development environment (gcc, cmake, libraries) plus indi library dependencies. For building Debian/Ubuntu packages you need additionally build-essential, fakeroot and dpkg-dev packages installed.

Compilation

The building from source procedure is simple. You need to have standard indi development environment installed. Usually it is a package with a name like libindi-dev or similar. You also need gcc and standard development libraries. Assuming you have the indi-3rdparty source tree in Projects/indi-3rdparty directory, run the following:

mkdir -p ~/Projects/build/indi-caux
cd ~/Projects/build/indi-caux
cmake -DCMAKE_INSTALL_PREFIX=/usr/local -DCMAKE_BUILD_TYPE=Debug ~/Projects/indi-3rdparty/indi-celestronaux
make -j4

If you have Debian/Ubuntu based system you can build debian package for the driver by running the following code (having indi-3rdparty tree in the same place and debian development packages installed):

mkdir -p ~/Projects/build/deb-indi-caux
cd ~/Projects/build/deb-indi-caux
cp -r ~/Projects/indi-3rdparty/indi-celestronaux .
cp -r ~/Projects/indi-3rdparty/debian//indi-celestronaux debian
cp -r ~/Projects/indi-3rdparty/cmake_modules indi-celestronaux/
fakeroot debian/rules binary

The packages will be build above the driver directory (in this case in ~/Projects/build/).

Features

The Celestron AUX driver provides GOTO and sky alignment functions of Celestron mounts which support AUX protocol and is designed to work over all available communication channels. It is modeled after EQMod driver for skywatcher mounts. It works directly with mount and axis controllers, without any help from the Hand Controller. In fact the HC may interfere with the driver operation and is better left disconnected from the mount or not used. The only potential function left to the HC is working as a serial interface to the mount. In principle, it should support any Celestron mount using AUX command set (most of them) with SkyFi wireless module, additional or build-in or over any type of serial connection (PC/AUX port with proper level converter or Hand Controller serial port). The driver was tested with NexStar Evolution (Alt/Az) and CPC (EQ) mounts.

Operation

The driver operation should be similar to other mount drivers. You need to set communication mode (Serial/TCP) in communication setup. The driver requires alignment (by sync operation after pointing to the selected object). Even one sync point is enough to have it operational in AltAz mode if the mount was properly leveled. The EQ mode requires a minimum of two sync points. For completely misaligned mount you need at least 3 sync points to have accurate pointing.

Alignment

The Celestron AUX driver embeds the Alignment Subsystem module that comes with the INDI library. This module allows to align the pointing coordinates of the telescope with respect to the celestial frame. After module alignment, the telescope pointing coordinates read from the driver will coincide with the direction actually pointed in the sky, less than a small error. This operation is generally performed at each power up or when the telescope mount is moved or changed for some reason.

This alignment operation is not a substitute for a correct mount leveling and orientation to north meridian for altazimuth mounts or to north/south celestial pole for equatorial mounts. Indeed, they are a prerequisite.

The software of the telescope mount that is generally embedded in the hand control has its own alignment system also. It is important to understand that the alignment system of the Celestron AUX driver and the alignment system of the telescope mount hand control are completely separated. They do not cooperate directly in any way. After power up, a mount alignment performed with the hand control is useful to have a correct telescope pointing during GOTOs given by the hand control, but this operation gives no information to the driver alignment subsystem. So, any GOTO performed by the driver will be incorrect until a driver alignment is done. This is the case of any GOTO operation requested by an INDIlib client like Kstars.

Reference points

All alignment procedures explained here are based on taking some reference points in the sky. For each reference point, its exact celestial coordinates must be known. This goal can be achieved in one of the following ways.

• plate solving the telescope image centered on the reference point
• taking the sky coordinates coming from the mount hand control that was previously aligned using its alignment procedure
• pointing the telescope according to the index marks on its mount
• visual slewing to known celestial objects with Kstars virtual hand control

If there are no reference points, the alignment system does not perform any transformation of the coordinates read by the telescope axis encoders. These coordinates are taken as the current celestial coordinates as they are. Since at power up the Celestron mount software presumes to be pointing to north with zero altitude (altazimuth mounts) or with zero declination (equatorial mounts), the telescope must be manually pointed to such coordinates. Otherwise, any GOTO from Kstars will be wrong.

If there is only one reference point, the alignment system with the single reference point and the mount type (altazimuth or equatorial) read from the alignment tab declares to be able to maps the coordinates read from the telescope axis encoders to the celestial coordinates that it is pointing at. In practice, the mount slews in altazimuthal model until two reference points are provided and SYNCed.

If there are two or more reference points, these are sufficient for the alignment subsystem to understand automatically the type of mount and to map the telescope axis encoders outputs to the pointed celestial coordinates.

Some rules of thumb to choose where to take the reference points. Avoid critical areas around celestial poles and zenith. Take them not too far from the sky zone where one want to point at.

The Celestron AUX driver alignment procedures explained below refers the use of Kstars.

Equatorial mount alignment

Quick alignment

This alignment can be done using the index marks of the mount or using the coordinates from the hand control. Tracking must be disabled.

1. point to declination (DE) zero and hourly angle (HA) -3 hours (rotate polar
    axis 45 degrees toward east starting from south meridian). Use mount hand control arrows or Kstars mount control arrows to slew.
2. establish this direction as the first reference point: do a manual SYNC (see below) with coordinates HA=-3 , DE=0.
3. rotate the polar axis westward by +6 hours. Keep DE=0. If DE displayed by Kstars changes even if the only slewing axis is RA, it don't care.
4. establish this direction as the second reference point: do a manual SYNC with coordinates HA=+3h , DE=0.

After the second SYNC, the driver is aligned and the GOTOs done by Kstars must work properly with some small error.

Precision alignment

This alignment can be a second step after the "quick alignment" or a start point. The only difference is that, if it is a second step, one can use the GOTO and the plate solving capabilities of Kstars to point the sky where to do the plate solving. Otherwise, another type of pointing is needed as listed above.

The screenshot below shows the Ekos plate solve tab. The plate solve procedure can started manually by clicking the "Capture and Solve" button at the upper left.

Kstars has also an automatic alignment procedure based on plate solving performed by the "Mount Model Tool" that can be started by clicking on the "Mount Model" button at the bottom of the above screenshot. Below there is a screenshot of the Mount Model Tool.

 Manual SYNC

Before to do a manual SYNC with Kstars, the telescope must be pointed at the selected reference point and the celestial coordinates (RA/DE or HA/DE or ALT/AZ) of the point must be known.

Open the mount tab of Ekos and click on the upper right button "Mount Control".

The mount control window opens.

Select the proper celestial coordinates type (RA/DE or AZ/AL or HA/DE). For example, in the figure is selected the coordinate type HA/DE. This type needs Kstars >= 3.5.0 .

Write coordinates values into input boxes. For example, in the figure HA = +3h and DE = 0 are given. The current coordinates displayed by Mount Control can copied into input boxes by clicking on them. This needs Kstars >= 3.5.1 .

Click on SYNC button.

Now, the current pointing direction, associated to the given celestial coordinates is acquired by the alignment subsystem as reference point.

Connectivity

USB/Serial

Celestron AUX driver can use any of the serial connections offered by Celestron scopes. The serial connections are listed below with their main characteristics.

1. HC: serial cable connected to hand controller serial port (less recent models).
   • 4 pins connector (RJ11).
   • 3 wires used: GND, TX, RX.
   • RS-232 serial voltage levels (+5V,-5V).
   • 9600 baud transmission speed.
   • No transmission flow handshake, no echo.
   • Command protocol: pass through (mostly AUX protocol encapsulated inside HC messages).
2. HC: USB cable connected to hand controller USB port (most recent models) (alpha testing).
   
   • mini USB connector.
   • Command protocol: pass through (mostly AUX protocol encapsulated inside HC messages).
3. AUX: serial cable connected to Celestron AUX port.
   • 6 pins connector (RJ12)
   • 5 wires used: GND, TX, RX, CTS, RTS
   • TTL serial voltage levels (+5V, 0V)
   • 19200 baud transmission speed
   • Half duplex CTS/RTS handshake with echo
   • Command protocol: AUX
4. PC: serial cable connected to Celestron PC port
   
   • 8 pins connector (RJ45)
   • 5 wires used: GND, TX, RX, CTS, RTS
   • RS-232 serial voltage levels (+5V,-5V)
   • 19200 baud transmission speed
   • Half duplex CTS/RTS handshake with echo
   • Command protocol: AUX
5. USB: USB cable connected to an USB port of telescope mount (alpha testing).
   
   • USB connector type A.
   • Command protocol: AUX.

Celestron AUX driver autodetects the type of serial connection, setting proper transmission speed, proper serial line handshake and proper command protocol. Serial connections details are just shown as an aid for Celestron scope to computer cabling.

As modern computers generally no longer have serial interfaces, a convenient way to make a serial connection to a Celestron scope is to use an USB to serial converter with the proper cable as mentioned in the previous list.

Beware of cheapest USB/serial converters, they have serial lines with TTL levels (+5V,0V). So, they work with AUX port only. Connections to HC and PC ports require a true USB/RS-232 serial converter with symmetric voltage levels (+5V,-5V).

On the other hand old standard RS-232 is symmetric +/-12V signalling should NEVER be connected to the AUX port. Nothing should be connected there without proper level converter. The AUX port is non-standard and connected directly to the bus between all motor controllers and main board. There is an oportunity to burn all scope electronics by connecting wrong signals there.

Network connection

This type of connection can be used with scopes with WiFi interface like NexStar Evolution or any other Celestron scope equipped with SkyFi Wi-Fi adapter. Except for selecting the TCP connection mode and filling in proper IP address/Port (out of the box it is IP:1.2.3.4, Port:2000). It is well advised to change this default values since they are actually incorrect. The 1.2.3.4 is an actual public IP address assigned to some network in Moscow, Russia (of all places ;) and should never be used for embedded systems in local networks. It is best to switch the scope to AP mode and connect it to your local network or dedicated access point. The rest of the communication functions exactly like over PC/AUX connection, since SkyFi is just a serial-over-ip adapter.

First time connection

INDI Celestron AUX connection tab.

To select serial connection simply press "Serial" button of "Connection Mode" property in Connection tab and set the USB port where Celestron scope is connected to. Baud rate is set automatically by driver. Displayed baud rate may differ from real interface speed.

Linux USB

If the controlling system, i.e. a raspberry pi, runs a linux operating system, when more than one USB device are connected, the persistence of USB port number for the same physical USB port is not guaranteed after a system reboot. This problem has two solutions:

1. Enable USB port scan in communication tab page.
2. Bind USB device under a static name.

Usage of USB port scan is straightforward, you just need to enable it in the Celestron AUX Connection tab. Sometimes, if you have several devices connected to USB, USB scan can fail or can mess up your devices.

The alternative solution of USB static name always works, but it is a little more tricky to set up. Several examples can be found searching over internet for "how to bind USB device under a static name".

Issues

There are no known basic functional bugs in this driver, but there are multiple missing features and it is still not as stable as it should. If you found a bug, please report it in (preferably) github issue tracker for the driver or a main INDI project issue tracker. (You can log in with a variety of existing accounts, including Google, Yahoo and OpenID.)