101 level questions

Devin Gingrich


I am strongly considering getting an exos2-GT with PMC-Eight, as opposed to a Celestron AVX, to go along with my newly acquired first gen Comet Hunter (so dang excited!!). That said, I have a few basic questions (my current mount is a Celestron):

1) Can I calibrate the scope using a third party program (SkySafari 5 Pro) or do I need to calibrate it using ExploreStars First, then hand off control to SkySafari?
2) What is the timeline for a native macOS or iOS variant of ExploreStars?
3) What is the process for doing daytime (solar observation) alignment?
4) Has there been any involvement with the PixInsight community? Their INDIClient would seem to me to be an extremely interesting point of integration (here’s an older link):

W. Christopher Moses

I'm glad you are looking at the pmc-8 system.  So far, I really like it.  I have the G-11 version.  You might want to check out my main thread for it:

It's really more about the pmc-8 than the G-11. I should start a new thread with a better name.

Your questions:
1. I assume you mean the star alignment.  You can do that from ExploreStars or from any ASCOM compatible programs. I think SkySafari is strictly iOS and Android, so you could not use it.

2. Have to ask Jerry 
3. Have to ask Jerry.
4. I can't speak for Jerry or Explore Scientific, but INDI is something I find very interesting.  It seems to have a more mature architecture than ASCOM. Unfortunately, it is not easy to port to windows. I belive such a project is under way and even operational to some degree.  How much of that can be used by PI is another question.

I'll take a look at the Windows port.  If it is mature enough to justify some work, I'll look into writing an INDI driver for the pmc-8


The ASCOM driver does not currently have a 2 or 3 star sky alignment incorporated, it just has a SYNC or as it is sometimes referred, a 1 star alignment. The SYNC does nothing to correct for polar alignment errors, that is the job of a 2 or 3 star alignment. You need to do a very good polar alignment and then you can correct the minor pointing errors with the SYNC command. The ASCOM Standard assumes the mount is physically polar aligned and therefore does not have any alignment functions.

The ExploreStars app is a stand alone application that is not used in conjunction with any other program. It is only meant to be a hand controller mainly for visual use. If you use a third-party program with the ASCOM driver then you will need to do a physical polar alignment so that the view does not drift while tracking.

There is no announced release date for a iOS or Android version of the ExploreStars app. I can say, though that the Android app is under active development and could be announced by the end of the year.

To do a daytime alignment is a process of aligning the azimuth axis to true north, and setting the altitude to the correct latitude value. I have used a quality magnetic compass to set the azimuth, make sure you correct for magnetic declination. Here in Virginia, the magnetic declination is +10 degrees. You can look up you location's magnetic declination on the web. Make sure you level the mount on the tripod first. In the following, you will be moving your mount with the ExploreStars application. You want to start out by positioning your mount using the index marks so that you are weights down (NORTH) and Declination 90 degrees (straight up and down when observing your telescope from the SOUTH, looking NORTH).

After you have aligned your mount on the azimuth axis to true north, then you can set the altitude by moving your mount (via the coordinate input screen) to RA close to the LMST (local mean sidereal time). I would suggest you move it just west of the Meridian say to 5 minutes before the current LMST, and then move your mount in DEC to make the scope point UP and to a value equal to your LATITUDE. So you would enter a value for DEC of 38 degrees, if your LATITUDE is 38 degrees.

What this does is point your mount vertically the ZENITH. Of course your telescope will be close to ZENITH but this is when you move the ALTITUDE axis on you mount to point the telescope straight up. You can measure this by laying a level across the top of your telescope tube (making sure it doesn't touch your objective if it is a refractor) and leveling it. This is when you can be sure it is pointing close to zenith.

This is how you can get a pretty good polar alignment during the daytime.

We have not done any work with PixInsight, but I have looked at the INDI stuff. I have talked with several people interested in developing an INDI driver, and our current position is that we will leave that up to others to do. We will supply all the needed information about our controller of course to facilitate that.

Ben K

My exos 2gt with PMC-8 just arrived this afternoon.

Haven't tested it outside yet, assembled it inside, fitted my OTA to a vixen cradle, and tested the fit in the mount.

Tomorrow I'll be booting up the PMC-8, and testing the app and confirming firmware versions and such.

Worth noting, not only is the exos 2gt with PMC-8 an upgrade because of the PMC-8, they include *2* 9.9kg counterweights and they tossed in an AC adapter for the PMC-8, it's no longer battery driven.

I'm pretty impressed so far, but I do want to figure out how to do a 2 or 3 star alignment.

Devin Gingrich

Outstanding!! I’m waiting on the next batch to go online from ES (apparently a week or so) and then place my order. Can’t wait to hear more of your impressions. Thanks!

Ben K


I got an odd item in my PMC-8 kit. It's an st4 plug with about 2" rubber cord, no wires sticking out. I put photos of it in an album on the group. Any ideas?

W. Christopher Moses

Its for changing the wifi channel.

Ben K

Ah, thank you Chris.