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iOptron ZEQ25GT page 2

First light:

I took the mount out last night as I wanted to get the polar alignment sorted, so I can use it more accurately during the daytime for solar imaging. As the skies were partly cloudy, I had to wait for my time to see Polaris. But when it came into view, it was very easy indeed to align the mount. iOptron has an app for polar alignment which costs £1.49, but there is an alternative app called Polar Scope Align which is free to download. Using this app, it becomes very easy to do the polar alignment.

Following the polar alignment, I did a one-star alignment with Capella. Once this was aligned, subsequent stars were visible with my 5mm reticle eyepiece and not too far off from the center of the reticle. That is pretty accurate indeed. As the skies became even more cloudy, I decided to slew to the moon to check out the slewing accuracy. As expected, it stopped right in the center of the view. Very pleased with it.

What I like about the ZEQ25GT?

1) It is very light and can be carried about without hurting my back – just 9.7kg kg for mount and tripod (without the counterweight and its support bar which I normally take off for storage, and are only reinstalled after taking the mount outside).

2) It has a built-in illuminated polar scope to aid alignment – brightness adjusted via the hand controller; you will not drop this unlike the Astrotrac polar scope, so it should maintain its collimation. And it works much better too.

3) It has Goto function with a database of about 50,000 objects, including some asteroids and comets. So far it has worked for stars, the moon and the Sun.

4) It has fine control of the slew speed (1x, 2x, 8x, 16x, 64x, 128x, 256x, 512x and max), so I can slew around the Sun to center the areas of interest more accurately; this is selected by pressing the numbers on the handcontroller (e.g. number 5 equates to the 64x slew speed – default).

5) It has built-in GPS, and I have found that it works fine from where I live, and will be able to set the location automatically with the mount in its zero position. I have read reviews where the GPS has not worked for the reviewer though.

6) The mount feels very solid with my solar setup (Skywatcher ED80 gold tube with the Daystar Quark), and definitely feels more steady than the Astrotrac. 

7) This mount allows for easy balancing of the telescope as it rotates freely when the RA and DEC locks are released. Much better than my Celestron CGEM.

8) This mount is supposed to be able to select the tracking speed for solar, lunar and deep sky objects – not mentioned in the instruction manual. But according to iOptron’s support this function is automatically selected by the mount depending on the object chosen.

9) The slewing noise is much quieter than the Celestron CGEM, even at maximum speed. It definitely is acceptable for night time use.

What could be improved?

1) This mount will beep to indicate that it has finished slewing to an object. As there is no mention in the instruction manual on how to switch this off, I contacted iOptron to ask them about this. Their reply was that it could not be switched off, so the way to muffle the sound is to put some tape on the speaker in the handcontroller. This was easy to do, and in fact I filled the speaker opening with tissue paper to muffle it even further. Now it is soft enough not to be a bother at night.

Here you can see the small round speaker with some tissue stuffed into its opening, and then taped up with duck tape.

The small black round speaker - I've stuffed some tissue into the hole of the speaker
The small black round speaker is on the keypad side of circuit board – I’ve stuffed some tissue into the hole of the speaker to muffle it
Duck tape stuck onto the speaker
Duck tape stuck onto the speaker to muffle it even further

Now I did note that that the flat ribbon connecting the circuit board to the display had slipped through the opening while I was fiddling with the speaker and was sandwiching between the Back button and the circuit board, preventing its use. Hence I had to move it back out (as in the pic below) before reassembling the hand controller.

The flat ribbon needs to be pulled back out, otherwise it will affect the back button on the remote
There is a flat ribbon on the back of the hand controller which needs to be pulled back out, otherwise it stops the contact of the back button with the circuit board

2) The 1.5″ tripod included with the mount is fairly short, so needs to be extended fully to get it to a height which is usable – which means it is not going to be as stable as it could be. Unfortunately there is not a pier (only a pier extension for the tripod) available for this mount, as a pier would be more stable.

3) The arm which supports the counterweight bar was not centered properly, being about 3 degrees out counterclockwise. This is easily fixed by loosening the three Allen screws holding it in place and then doing the adjustment before re-tightening these screws.

Three Allen screws holding the arm into which the counterweight shaft fits
There are three Allen screws (the bigger ones) at 120 degrees apart holding the arm into which the counterweight shaft fits. This photo was taken after I had aligned the two Allen screws pictured above to be in line

4) There are no markers to indicate that the mount is centered along the RA and DEC axis. Hence I had to print some stickers to help with this.

Sticker for aiding centering of declination axis
Sticker for aiding centering of declination axis
Centering sticker to aid centering of right ascension axis
Centering sticker to aid centering of right ascension axis (there is one on the opposite side as well)

As you can tell, there are a few minor issues with this mount, but easily fixed with a little DIY. So in a sense it does not detract from me liking this mount.


I am very pleased with the iOptron ZEQ25GT for solar visual, and I am pleased with how easy the polar alignment is. It slews very accurately after alignment to the stars, and should perform very well for solar imaging as well. It is so portable and not back-breaking, which makes it very handy indeed.

Now the real test for this mount would be night time use for long exposure imaging, which I’ve not done so cannot comment about this. With the ability for PEC recording and playback to improve the periodic error, and an autoguider port to allow for longer guided exposures, it should do very well. Definitely recommended (but if it does work well for astroimaging, then it will be highly recommended).

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