Polar Alignment Software

Sumerian Optics Canopus

iOptron iEQ45 Review

iOptron iEQ45 Periodic Error

Maxim DL DDP Filter

Electroluminescent panel light box


iOptron iEQ45 Review - Is it the "premium astro-imaging mount" that iOptron claim it to be?

This review aims to establish whether or not the iEQ45 is the "premium astro-imaging mount" that iOptron claim it to be. Not least because the reason that I bought one was because I wanted a portable, affordable mount for astro-imaging purposes.

In order for the iEQ45 to live up to iOptron's claim, my expectations for the mount were that it would achieve the following.

  1. Achieve good polar alignment.
  2. Provide acceptable go-to pointing accuracy.
  3. Have an acceptable level of periodic error.
  4. Have an acceptable level of backlash.

I am therefore using the above criteria for the basis of this review.

Polar Alignment

ioptron ieq45 polar scopeThe iEQ45 is fitted with a polar alignment scope that incorporates an illuminated reticule. The reticule is in the form of a clock dial with concentric circles for use in either the northern and southern hemispheres. The procedure for using the polar scope is very straight forward. The entire process took less than five minutes.

Having polar aligned the mount using the polar scope, I was curious to know just how accurate the polar alignment was. Using the polar alignment function in PEMPro, I set about measuring any remaining alignment error. I was pleasantly surprised to find that the iEQ45's polar scope had aligned the mount to better than 3 arc minutes of the celestial pole. From my experience, 3 arc minutes is perfectly acceptable for imaging purposes and pretty much as good as it gets with a polar scope, perhaps with the exception of the Takahashi polar scope.

5 minute un-guided exposure

As a further test, I set about taking a series of un-guided exposures and found that I could take 5 minute exposures before noticing elongation of the stars within the image. The following is an area of an un-guided image taken over 5 min's viewed at 100% of actual size. This is obviously an excellent result.

iOptron iEQ45 un-guided exposure

Go-to Accuracy

The iEQ45's firmware provides the option for either a one star alignment or a two star alignment. I chose to use the two star alignment option and used images from my CCD camera with the cross hairs enabled in Maxim DL. This ensured both the accuracy of the alignments and also eliminated the need for a star diagonal. Following a two star alignment, I found that the go-to pointing accuracy of the mount was good enough to almost centre subsequent objects on the CCD chip. Again, an excellent result.

Also, having parked the mount in its "zero position" and left the mount/scope/camera over night, when I came to use it the following night, without doing any further alignments, the go-to pointing accuracy was still good enough to put objects on the CCD chip.

Periodic Error

I have included a detailed analysis of the iEQ45's periodic error within this web site. As you can see, prior to PEC the error was 31.47 arc sec's peak to peak. This is probably comparable to most mounts in this price range. Having programmed the PEC function within the mount's software using PEMPro, the periodic error was reduced to 6 arc sec's peak to peak. Specific details of the PE curves produced by PEMPro can be found here.


iOptron describe the mount as having a "gap-free structure for both the RA and declination worm gears. There is also a facility within the hand-controller to set backlash compensation, should this prove necessary. I haven't undertaken a detailed study of the mount's backlash, but both the auto guiding calibration in Maxim DL and auto guiding corrections appear to show very little backlash. I have therefore been imaging with the mount without any software backlash compensation.

The Results.

I have imaged several deep sky objects to test the iEQ45's capabilities and have used my Takahashi FSQ106ED and FLI ML8300 CCD camera with Lodestar guide camera. Maxim DL was used for both Image acquisition and auto guiding. The following images were all taken using the iEQ45. Click on any image to enlarge and use the left and right arrow keys to scroll through the images.

M44 Beehive Cluster
M51 Whirlpool Galaxy
M81 and M82 Galaxies
M101 Pinwheel Galaxy
M44 Beehive Cluster
M51 Whirlpool Galaxy
M81 & M82 Galaxies
M101 Pinwheel Galaxy
M31 Andromeda Galaxy
M33 Pinwheel Galaxy
IC5146 Cocoon Nebula
M31 Andromeda Galaxy
M33 Pinwheel Galaxy
IC 5146 Cocoon Nebula


The following is a screen-shot of the Maxim DL camera control window with Camera 2 relating to the guide camera. The RA axis corrections are displayed as the X axis and declination corrections are displayed as the Y axis. The minor declination corrections confirm the accuracy of the polar axis scope. During the time that I watched the tracking information, corrections in the RA axis varied from 0.05 pixels to around 1.0 pixel.

ieq45 camera control in maxim dl

The following screen shot shows the tracking error graph. The vertical scale is set to 2 pixels.

ieq45 tracking error graph

The following is a cropped image of M44 shown at 100% of actual size.

iEQ45 M44 Beehive Cluster

Below is a region of the same image at 400% of actual size

iEQ45 image of M44 Beehive Cluster

Whilst there is some elongation of the stars at 400% of actual image size, the image at 100% is acceptable by most people's standards.


Having bought the mount because of it's load capacity and portability, I found it to be very good value for money. The polar alignment scope consistantly gave me very good polar alignment, the pointing accuracy was such that it would place objcets pretty much in the centra of a CCD and the mount does not suffer with backlash problems. The periodic error without PEC is probably comparable with other mounts of similar price. Having programmed the mount's PEC function and reduced the error to 6 arc sec's, I found that the mount performed very well. The images that I took using the mount speak for themselves. iOptron describe the mount as being suitable for entry level and intermediate astrophotographers and I would agree with that..