June 16, 2017: The Orion Sirius Pro AZ/EQ-G mount, Part Two – Great Locating and Tracking! and the Celestron Lithium Powertank

Power problems solved!  The Celestron Lithium Iron Phosphate Powertank (which I’ll more fully describe below) puts out 3 amps, and powers this mount excellently.  No more stutter-slew or stutter-track as I described in my last post.  The mount just works great.  Finally.

But how well does this mount really work?  I tested it two ways – to see how well it would locate objects, and then to see how well it would track.  With only my eight-pound Mak on it, the mount would not be stressed at all in terms of payload capacity.

As I discussed in my last post, even with the stutter-slew and stutter-track, the mount was still very much aware of where it was pointed.  It was finding objects and putting them well within the field of view, even with the inadequate power source.

Now that the power problems were solved, I started with the same two alignment stars, Spica and Altair, on pretty much opposite sides of the sky.  I first centered Spica very well, with the final centering movements being up and to the right.  This supposedly tightens the belts in the motors and eliminates backlash error – which is that the mount thinks it’s pointing at a particular location, but it’s actually pointing slightly off from that based on the position of the belts.

Completing the two-star alignment by slewing over to Altair, it placed it just outside the bottom of the field of view, but close enough so that its reflected light was bouncing off of the inside of my tube, so that although I couldn’t see the star, I could see the flare.  Obviously, that’s not a good thing, as it is indicative that there is a loss of contrast because the light isn’t going where it’s supposed to go, but it is kinda helpful in situations like this.

Next, I slewed on over to the 8-day-old moon.  While it was well within the field of view, it was not centered in the 32mm Plossl, which has a field of view in the Mak of about 1.05 degrees at 48x.  It was off by about a quarter to a third of a degree in both altitude and azimuth, in the lower left of the field.   Not too shabby.

Jupiter was right next door to the moon, so I went there.  Again, about the same amount off, same location.  Saturn was next.  It was off by the same amount, but this time on the bottom left of the field.  I moved the scope a bit to put Titan just inside the edge of the field at 48x.  I came back 30 minutes later, and I could not detect any significant movement.  Which is not to say that it didn’t move, but just to say that I couldn’t see any.  That’s pretty darn good!

Moving back to the moon, I centered Copernicus, upped the magnification to 123x with my 12.5mm ortho and left it.  After 20 minutes, the crater had slid about three-quarters of the way to the bottom of the one-third degree wide field, a tracking error of about 8 minutes.  Hmmm.  That’s not so darn good.

I would have noticed this much movement in relation to how it was tracking Saturn – that much error would have moved the planet about one-quarter of the way from the edge in towards the center (or completely out of the field entirely).  I wonder if this tracking error has to do with the tracking rate more than anything else – that the moon is not moving precisely with the rest of the sky’s sidereal rate, but is moving at its own lunar rate.  You would think that if you told the mount to track the moon that it would switch from sidereal tracking to lunar tracking automatically.

Finally, I’m sort of getting used to the weight of the mount.  Yeah, it’s heavy, but it’s still “easy” enough to lift by the counterweight shaft on one side of the pier, and the Vixen dovetail on the other, and reposition the loaded mount around on my balcony, a few feet this way and that.

However, the very fact that it is sooo much heavier than my SLT mount makes me not want to use it as much; i.e., take it on up to my apartment building’s roof for a full observing session.  For all its shortcomings, with the SLT mount, I can just take the entire mount + scope, sling it over my shoulder, and go – even hiking a mile or more with the entire mount + scope assembly, ready to go.  But with this mount, I have to take the scope off, disassemble the mount – meaning, take the mount head off of the pier and tripod – and then make three trips just to get the scope up there, let alone reassembling the whole thing, and then making a fourth trip to bring up my observing chair and eyepiece case.

As the saying goes, the best scope – or mount – is the one that gets used.  This mount is just too heavy and too cumbersome for me to use as an everyday mount to take the scope out whenever I feel like it.  It looks like my SLT mount will certainly have some use left in it after all – at least for using the Mak, of course.

One annoying thing about this mount is that with the positioning of the vixen dovetail on the right side of the mount, I have to attach the Mak upside-down, as shown in this picture.

The mount with the Mak. The orange PowerTank is there, as well as a blue tarp I bought from Home Depot for $16 to cover this whole thing.  Note the orientation of the Mak, as seen by the location of the RDF on the bottom.

This is annoying because, as you can see, the RDF is located on the bottom of the scope.  That means I gotta get real low to look through it.  Of course, that’s not a big deal, because I’ve only gotta do that twice, for a few seconds each, right at the beginning of each observing session, to align the scope on the two stars.

And yes, of course, I can flip the scope over on the altitude axis so that the RDF is on top.  But when I did try that (I’m not that stupid, ya know), the mount doesn’t like that – at all.  When I did that, the mount decided that the sky was below it, on the ground.  That wasn’t helpful.

Fortunately, this won’t be a problem once I get the C9.25.  The C9.25 will go on the right – maybe with the same upside down problem, though – and the Mak will go on the second vixen dovetail, on the left – where the counterweights now are.



The Celestron Lithium PowerTank does the job, that’s for sure.  No more little powerpacks for this big mount.  The PowerTank is a tiny cylindrical little thing, just 2 1/4 pounds.  It comes with a strap to attach it to a tripod leg, which is handy.  I’ve had it running the mount for about 5 hours so far over two sessions – I just let it track for awhile – and it still shows one out of four lights lit in terms of the power it has remaining.  That’s pretty good.  The specs say it’s supposed to give 10 hours of power.  It looks like that might be closer to about 6 or 7, but that’s still plenty enough for me.

It helpfully has 15 LEDs (fifteen!) that shine in either red or white light on its side.  There are two settings:  bright, and blinding.  The bright setting would be more than enough for setting up or tearing down in the darkness of a dark site.  The blinding setting would be good not only for finding lost setscrews and such that have dropped on the ground in the dark during your observing session, but also for signalling passing planes in case you’re lost at sea.  The battery also has two USB ports that you can use to recharge your phone or tablet.

And of course, the key feature of this battery for me is that it maintains its charge on a shelf, well, basically forever.  What has two thumbs and won’t be baby-sitting batteries?  This guy!

I’m back in business, baby!  Now if I could just find the right used C9.25 . . .

Next time:  I Like Dobs!  A Semi-Brief Rant


3 thoughts on “June 16, 2017: The Orion Sirius Pro AZ/EQ-G mount, Part Two – Great Locating and Tracking! and the Celestron Lithium Powertank

  1. I have heard much about mechanical play in this mount. Did you notice anything of that sort? I am thinking about buying one of these but don’t want to have to take it apart to fix a problem that really shouldn’t be there in the first place, especially for the price of the mount. Thanks and I liked your review. You sold me on the Celestron Power Tank.


    1. Hi, Robert, and thanks, Yes, I heard and read the same thing. I asked Orion about this specifically when I bought the mount, because the only review on the Sirius Pro page specifically complained about that.

      I have not experienced this problem. However, there are a few caveats to that statement. One is that I’m only put my 8-pound Mak on it so far, so I can’t answer whether there’s play in the mount with heavier OTAs. The other is that I don’t do astrophotography, so that if there is play at that level, I won’t see it.

      At some point in the future, I will try the mount with both my Mak and my ST-80 on it, which will make it 12 pounds, and a better test, and I’ll let you know.


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