The following commands (#tags) are supported by the observatory's Twitter and Email interface. Except for the #help, #hello and #human commands, more than one command can be included in a single tweet, Twitter direct message or line of text in an email.

Some commands need additional information (parameters) in the form of xxx=yyy. If yyy needs to include spaces, surround the entire parameter in double-quotes (eg. "parameter=this is a parameter value". Anything other than a tag or parameter is ignored.


This sends a message which directs you to this website. If this tag is received, other tags are ignored.


This sends your message to a human by email - include what you need help within the tweet or on the same email line. If this #tag is received, other tags are ignored.


This is a good "test" message - the observatory replies by introducing itself!


This sends the status of what the observatory is doing (or not doing) now. An example response is:

#aroreplies @davidjameslane I am starting up the observatory...


This sends the status of whether the Sun is up, the sky is in twilight or if its fully dark. An example response is:

#aroreplies @davidjameslane The Sun is presently up!


This sends a brief report from the observatory's cloud sensor. If the command originated from a public Tweet or an e-mail (but not a Twitter direct message) a graph showing the last 24 hours of cloud sensor data will also be included. An example response is:

#aroreplies @davidjameslane The sky is CLOUDY (temp=25C, wind=3 km/h)


This sends either a current IR (default) or visible light satellite image centered on the observatory's location. Specify a visible light image using the parameter "type=vis" - not including this parameter or specifying any other value selects an IR image. An example response is (not including the image):

#aroreplies Here is the IR satellite image (courtesy NASA/NOAA). ARO is near the centre!

This command cannot be used if sent from a Twitter direct message.


This sends an image showing the inside of the observatory's dome. An example response is:

#aroreplies @davidjameslane Here is the current domecam image!


This command requests the telescope take an image of an astronomical object. The request is placed in the telescope's observation queue. Certain checks are done before the request is accepted. In particular:

  • The object must be observable from Nova Scotia within the next month's time.
  • Most users are limited to having 3 observations in the queue at a time. Users given special permission may have up to 15 observations in the queue.
  • You can't request the same object twice (unless using a different filter or exposure). An exception is made for special observations and solar system objects.

The parameters accepted are as follows:


objectname is required and must be the name or catalog number of an astronomical object (without any spaces). The telescope knows how to find lots of celestial objects, including:

  • The Messier Catalog - a list of bright star clusters, nebulae and galaxies (eg. M1 or M33)
  • Common object names (eg. OrionNebula, ClownFaceNebula, etc.)
  • Any object in the Saguaro Astronomy Club Deep Sky Database. This includes about 10,000 bright star clusters, nebulae and galaxies. Specify the object's catalog number (most off these will be an NGC)
  • Any galaxy in the Principle Galaxy Catalog (eg. PGC65086)
  • Stars (by their common name (eg. Vega), or by their HD, HR, SAO, HIP, TYC, GSC, or USNOA2 catalog number). Stars brighter than magnitude 6.5 are not allowed.
  • Variable Stars - any star in the General Catalog of Variable Stars (eg. ZLeo or V0456Cyg)
  • Double Stars - any star in the Washington Visual Double Star catalog (eg. STF2578)
  • Planets (by their name) - note that planets will not look that good as we are all used to seeing planet images taken with space probes!
  • Moon - use 'Moon' as the name. Because the Moon is too bright, it will not be imaged when its phase is close to full.
  • Comets - any comet presently considered observable by the IAU. Use their full name or their shortened designation (eg. "C/1997B1" or "125P")
  • Asteroids - any "numbered" asteroid (also called minor planets) brighter than about 17th magnitude (that usually means 1000s of them!). Use their proper name (eg. "Vesta") or their number designation (eg. "(94)" which is Aurora)


This adds your comment to the observation. If more than one word is needed, enclose the whole parameter in double-quotes (eg. "comment=Andromeda Galaxy"). As an example of how it might be used, you might use this feature to give another name for your request or the reason for the request.


This specifies the exposure time, in seconds, for the observation. It is optional. If left out, 180 seconds (3 minutes) is used. The shortest values accepted are 0.1 seconds and the longest is 300 seconds (5 minutes). When the telescope takes the image, it actually splits the exposure into parts 60 seconds or less and automatically combines the parts into one image before it is sent to you. Users given special permission are allowed up to 900 seconds (15 minutes).

For some bright objects (the Moon and the planets) the specified exposure is overridden to hopefully provided better images for these objects. See the 'override' option below.


This specifies which colour filter is placed in front of the camera. It is optional - if left out, the CLR filter is used (this is un-filtered). Our camera takes black and white - colour images are made manually by combining separate images taken in red, green and blue filters. Valid filters are: CLR, RED, GRN, BLU, B, V, R, I, and SPECTRA.

Normal Special Observations:


This specifies that the observation be done as a special exposure, which allows advanced control over how the exposures are taken and multiple filters to be observed together in a single request. You need special permission to use this feature.

Up to 10 groups of 3 parameters (separated by commas), each specifying the exposure details for a filter, are to be provided as follows:

filtername - this is the same as described above for the filter= option, except for an additional "filter" called "time", which can be used to insert a time delay between observations

subexp - this is the sub exposure in seconds, from 0.1 to 60 seconds

numsubs - the number of sub exposures taken and combined into a single image (1 to 20). The total exposure of numsubs x subexp cannot exceed 900 seconds

The total overall maximum exposure for all filters is 3,600 seconds.

The example below takes 10 minute exposures in RED, GRN, BLU filters:


If this option is used, the filter and exposure options are ignored.

Time-Series Special Observations:


This specifies that the observation is to be done as repeating time-series ("TS") of Normal Special Observations for a minimum of min and a maximum of max minutes duration. You need special permission to use this feature.

The min and max values are used as follows:

min - for an observation to be done, the object must be observable (object above "minalt", above the observatory's local horizon restrictions, and enough time left in the night before morning twilight) for at least "min" minutes.

max - when the observation is underway, it will continue for a duration "max" minutes, as long as the object remains observable (see "min" above).

Min and max can range from 1 to 480 minutes, provided max is greater than or equal to min. min should be set to the shortest time-series that will be accepted and max to the preferred longest time-series length.

The example below takes 2 minute exposures in B and V filters and a delay of five minutes for a minimum length of 60 minutes and maximum of 3 hours:


If this option is used, the filter and exposure options are ignored.

fullsize=yes (or no)

This is optional and when set to 'yes' causes the image to cover the largest sky area possible - about 22.9 x 15.3 arc-minutes (1536 x 1020 pixels) or about the size of the Moon. The default size, which fits many common objects, is 17.8 x 13.5 arc-minutes (1200x900 pixels).


This specifies the minimum altitude (in degrees) above the horizon that the observation will be done at. The default value is 25 degrees. Images taken at higher altitudes will generally give better images (sharper and clearer), but setting larger values reduces the number of hours per night that an object can be observed, so setting a high value may mean your request takes longer to fulfill. The smallest value allowed is 20 degrees.


This specifies the maximum moon illumination (as 0 to 100 percent) that the observation will be done at. The default value is 100%. The Moon is a major source of light pollution - images taken when the Moon is up and bright will not (generally) be as good as images taken when the Moon is not up or not as bright (eg. crescent phases). If the Moon is lower than 5 degrees in altitude (or not up at all) when the observation is taken, this value is ignored.


For some bright objects (the Moon and the planets) some of the settings above are overridden to hopefully provided better images for these objects. You can override this by including 'override=no' in the tweet.

repeat=yes (or no)

When your observation is completed successfully, this optional feature causes it to be automatically re-submitted to the queue. You need special permission to use this feature.


This advanced parameter is used to precisely constrain when an observation request will start. It is intended to be used to observe during an "interesting" time of a periodically changing object, for example, the eclipse part of an eclipsing binary star's orbit or the transit of an extra-solar planet. It can also be used to constrain the time of night that an observation takes place. Note that all other conditions must be met before the observation will start (eg. 'minalt' and 'maxmoon' parameters). The observation also competes with other observation requests in the queue - the priority option can be used to help ensure that the observation starts when needed.

The 'epoch' options are:

hdj - the Heliocentric Julian Date of a reference point in time when the observation should take place. This is usually a date in the past.

period - the number of days between observations (this is added or subtracted in multiples from hjd to calculate valid observation times).

adjustment - the number of minutes to adjust the calculated valid observation times forward or backward. Values of -1440 to 1440 are accepted (which is +/- 1 day). This is intended, for example, to allow the observation to start before the "interesting" time that the hjd and period refer to. The actual time that an observation takes place is also affected by "overhead" activities, for example, the time it takes to move the telescope to the object. This can be a few minutes, so should be considered when setting an adjustment value.

tolerance - the number of minutes, up to 1440 (1 day), early or late from the time determined by the hjdperiod, and adjustment values, that an observation will take place. Observations will rarely happen exactly when an observer wants them to. This is most often caused because the telescope is completing another request. If larger values are used, the observation is more likely to take place but may start an proportionally amount of time before or after the ideal time.


... epoch=2454237.53556,1.7429935,-102,30 special=TS,217,217,V,60,1 ...

This observes the whole transit of the extra solar planet CoRoT-2b for 196 minutes (time-series of 60 second exposures in a V filter). This planet takes 136 minutes to transit, so we start observing it about 102 minutes before the predicted time and are willing to start +/- 30 minutes from the ideal time. The adjustment value of -102 comes from: half the transit time (68), 30 minutes tolerance, and 5 minutes of overhead. The time-series duration of 196 is the transit time (136 plus the 1/2 the adjustment value (51) plus the tolerance value (30). 


This is an advanced parameter that defocuses the telescope by the specified "steps". It is intended to be used when performing photometry of bright stars to reduce overexposure OR to increase photometric precision by blurring stars over more pixels - this can reduce errors caused by how light falls and is recorded by each pixel. The allowable range of steps is -1000 to 1000 (the default is 0). If the specified value causes the focus position to go past its limited range, the observation will be skipped.


This parameter offsets the telescope's position from its catalog position by the specified amounts in right ascension (offsetra) and declination (offsetdec). The values are specified as the percentage of the field of view (see the fullsize parameter above) and can range from -500 to 500 percent. Positive values of offsetdec move the position north and positive values of offsetra move the position east.

This parameter has several uses, for example:

  • building larger images using a mosaic of separate fields,
  • offsetting a comet's nucleus to a corner of the field so more of the tail can be recorded,
  • and placing a variable star off-centre so that reference/check stars are in the field of view.


This specifies the priority given to the observation request. You need special permission to use this feature. The points value can range from -100 (lowest priority) to 100 (highest priority). The default value is 0. The observatory plays a "points" game when deciding the order to observe requests in its queue. It considers a number of factors - the priority setting essentially "rigs" the points game to favour or disfavour your request. A priority of -100 disables the observation.

hide=yes (or no)

This causes your observation to not be displayed on the Completed Observations index page. Do not assume that this means your observation will be private because it won't.

If non-recognized parameters are present, they are ignored. If an error is detected, you will receive reply message indicating the nature of the error, otherwise you will receive a reply like:

#aroreplies @davidjameslane Object M42 is in my #request queue as ID 00006 (exposure=120 seconds filter=HA)

Note the ID (00006 in this case) - that is the request ID assigned uniquely to your observation request.

Here are some examples:

#request object=M36

Requests an observation of star cluster M36 (exposure time would be default of 3 minutes and unfiltered (the "CLR" filter) with normal image size)

#request object=NGC7331 exposure=300

Requests an observation of galaxy NGC7331 (exposure time would be 300 seconds and normal image size)

#request object=M27 filter=OIII exposure=30

Requests an observation of planetary nebula M27 (exposure time would be 30 seconds using the Oxygen III filter and normal image size)

#request object=M42 filter=HA fullsize=yes

Requests an observation of nebula M42 (exposure time would be default of 3 minutes using the Hydrogen Alpha filter and full image size)

#request object=M5 minalt=40

Requests an observation of globular cluster M5 (exposure time would be default of 3 minutes unfiltered at a minimum altitude of 40 degrees and normal image size)


This command sends you the number of requests in observation queue and a link to web page showing your requests. An example reply is shown below.

#aroreplies You have 2 requests in the queue. The details are here:


This command allows you to edit an existing observation request. The advantage of editing an observation vs. deleting and re-requesting it is that its place in the queue is maintained.

The following example changes the exposure of request ID 1927 to 300 seconds:

#edit id=1927 exposure=300

An example reply is:

At 09:07:15: Observation request ID 1927 (C/2013US10) has been edited.

The following options, described in the #request command, can be edited: comment, exposure, filter, special, fullsize, maxmoon, minalt, hide, and priority. The target object cannot be changed. You can include multiple attribute changes in the same #edit command.

If the parameters maxmoon and minalt are changed the observation be not observable (and this is not checked).


This command deletes one of your requests from the observation queue. The request ID is to be provided as in the following example:

#delete id=00005

You can only delete your own requests. If you don't know the ID, use the #myrequests command.


This command adds a new object to the object to the object database that can be accessed by #request command. You need special permission to use this feature.

The parameters accepted (some are optional) are as follows:


objectname is the name you wish to refer the object by. It is augmented by the observatory's code (ARO) and your unique observer ID. This ensures that your object names are unique and won't interfere with other observers or the built in object database. The assigned name will be sent to you.


This is the object's Right Ascension in decimal hours or in the format hh:mm:ss.s (J2000 epoch).


This is the object's Declination in decimal degrees or in the format +dd:mm:ss (J2000 epoch).


This is the object's brightness in magnitude units (this is an optional parameter).


This is an optional parameter that specifies the type of astronomical object. Values from 0 to 17 represent the following object types:

  • 0 is a star
  • 1 is a galaxy
  • 2 is a globular cluster
  • 3 is an open cluster
  • 4 is a nebula
  • 5 is a planetary nebula
  • 6 is an “other” type of deep sky object (this is the default setting)
  • 7 is a solar system object
  • 8-12 are not used
  • 13 is a double star
  • 14 is a variable star

Here are a couple of examples:

#addobject object=Cluster205 ra=12.345 dec=-5.3432

#addobject object=UMaSN1 ra=05:35:01.1 dec=+62:10:35 type=1 mag=17

An example reply is:

#aroreplies @davidjameslane Object ARO-2-UMASN1 has been added to my database


This command queries the telescope's object database. If found, it also determines whether or not the object can be observed, and therefore be used by the #request command.

The 'object' parameter is required as follows:


objectname is the name of the object you wish to search for.

Here is an example:

#lookup object=ARO-2-UMASN1

An example reply is:

#aroreplies @davidjameslane Fixed object ARO-2-UMASN1 found at position RA=05:32:02.6 DEC=+82d02'18", and it can be requested now


This command sends the jpeg image (if available) for a completed observation.

The request ID is to be provided as in the following example:

#send id=599

This command cannot be used if sent from a Twitter direct message.