Beginner Basic Questions


I have a NexDome Observatory with rotator and shutter motor kits, Celestron CGEM-DX mount, rain sensor, ASCOM 6.5SP1 running Beaver. I need some basic help getting started. I have read the getting started section in help, but my questions are more basic: Do I need to initiate ASCOM Hub, open it, and connect my equipment there first?

Secondly, I think I just want to start with making sure SGP connects to my equipment and everything moves as it should. I’ve read help on setting up a sequence and kind of got this. The tutorial uses the icons for selecting equipment which is fine, but where do the dome statistic get entered, under tools>equipment profiles?

I know these are really basic, so please keep it simple for me. I just purchased SGP based on some other owners with domes who recommended it to me. BTW, my dome is running under Windows 10 64 bit Home edition, and I’m remote controlling it using an iMac.


Link to Logs

Useful Info

OS: 10 64 bit


I have a different set-up to yours with a Pulsar Dome with the rotation kit and an EQ6R-Pro mount, but the principles are still the same and so no, you shouldn’t need to connect via the ASCOM Hub to connect everything up. In SGPro, you connect your telescope via the buttons on the right hand side of the sequencer window, but just below the telescope section, there is an arrow that will expand out to show additional options, including the observatory, flat box, camera rotator, etc. You select your NexDome ASCOM driver in the observatory box and connect from there.

To synchronise the dome movement with the telescope, you need to enter the slave settings, and you find these by first opening up the control panel - you are best doing this via an equipment profile, but you may not be sufficiently familiar with SGPro yet, so you could do that later if you want (in fact this is a must to avoid having to repeatedly enter the slave values). Having opened the Control Panel, click on the Other tab and somewhere on that page you will find a box called Slave Settings. Click on it to bring up something like this:


If you hover over the numeric entry box, a pop-up will appear explaining each parameter, but they are mostly obvious:
Radius - radius of the dome, not the diameter
East / North Offset - if the centre of rotation of your mount (where the RA and DEC axes intersect) is slightly offset from the centre, this is the amount of offset, normally these will be small
Vertical Offset - this is how much the centre of rotation of your mount is above the bottom plane of the dome hemisphere - a negative number indicates it is below
GEM offset - here you need to measure from the centre of rotation to the centre-line (optical axis) of your scope along the DEC axis
Allowable error - how far the centre of the dome opening can be from where the scope is pointing before it is asked to move - this depends on the width of the opening and the size of your scope - I use 2 degrees although I’m sure I could use a much higher number.

Having the observatory synchronised with the scope has made such a difference to my sleep patterns - I can go to bed and all I really need to worry about is whether unexpected clouds have rolled through in the night, but SGPro even handles that pretty well.


Terry, thanks so much for your help. I could not find, probably using the wrong search terms, a tutorial for setting up the dome. I’ll continue to follow the tutorials, but the first one is focused on setting up a sequence, and I would think connecting equipment would be on the list.

Your instructions were right on, and I was hoping that once I enter the scope slave settings that this will populate the dome equipment profile? When I looked at the profile for the dome, the slave settings we not there.

If you could point me to the tutorials or knowledge base, I’d be grateful.

I’m not quite sure I understand what is going wrong, so all I can do is run through my set-up - my dome is the Pulsar system, so there might be differences in detail, but that should be all. I assume that you have your dome control box connected up to your observatory PC by USB and you have installed any NexDome control software plus the ASCOM driver. Now with my system, all I ever need to do is put the dome dimensions into SGPro, I don’t need to specifically populate information into the ASCOM driver (note the same is true with NINA which I have also used successfully). The way that I set things up in SGPro is via and Equipment Profile, in this example using an ATIK 383L with broadband filters, etc.

The “Other” tab has a box that lets you select the Observatory ASCOM driver, then in my case I need to click the “Settings” button to bring up the following:

Screenshot 2021-09-16 081504

This tells SGPro which COM port the control box is located on - I know that from Device Manager for instance, but the Search button found the right COM port. Having established the right connection path, the next step is the Slave Settings:

Screenshot 2021-09-16 081650

These are my numbers (in mm obviously - if they were inches it would be sitting on top of a mountain in Tenerife or Chile or somewhere!). Remember to save your profile (having already set up your camera, focuser, etc., as appropriate) as you’ll need it to set up the sequence. You do this using “File>New Sequence with Profile” or Ctrl-Shift-N and selecting the profile that you created. One of my sequences looks like this:

Note that I’ve expanded the section on the right which shows the Observatory populated with the Pulsar Dome as set up in my profile. If I click on the wrench next to it, it will bring up the COM port dialogue which will have the correct COM port already selected, and to connect to the dome you now click on the grey button to the right of that which should turn yellow to show the link has been successful. Once you have your telescope connected, the final step is to make sure that the two are working in sync:


Make sure you check the “Slave to Telescope” box in the Observatory Panel, otherwise nothing will happen when the scope moves.

You’ll find some information in the Help file under Control Panel>Other Equipment>Observatories.

I hope that this has helped.


I have a nexdome and these videos should answer a lot if your questions.

Greybeard, I just left a comment on your YouTube channel. I’d like to contact you via DM but have no idea how to do that either here or YouTube.