MAY 2019

iOptron MiniTower GPS problem – and solutions.

[This is just one of many articles in the author’s Astronomy Digest.]

My iOptron MiniTower (as described in detail the iOptron article in the digest) is my ‘Get-up and Go’ mount for taking to star parties or when I go on astronomy field trips with my smaller telescopes.  It is easy to align and has excellent ‘goto’ and tracking abilities.  It is one of the very first imported into the UK and I reviewed it for the Astronomy Now magazine.

My first outing with the mount since the beginning of April 2019 was on May 10th 2019.  My targets were, first the Sun in white light and H-alpha and then the Moon, both high in the sky.   Initially I found and tracked the Sun as usual but then when the GPS said ‘OK’ thing went haywire.  When I asked to ‘goto’ the Sun it was low in the west and when I asked to ‘goto’ the Moon it had not risen!

However, I was aware that on April 6th 2019 the 10-bit week counter in GPS systems would ‘rollover’ and reset to zero giving GPS systems not allowing for this problem a false date.  In tests on the 13th May 2019, I found that, once the GPS system has said ‘OK, the date was set to 2099-09-27 rather than 2019-05-13.   This was thus the obvious cause of the problem.

On the iOptron website there are details as to obtaining from their ‘shop’ a replacement gps module at a reduced price of $50 (from $99).  One has to contact them directly to ship one outside the USA.

In web discussions some have suggested unconnecting the gps module from the main electronics board.  However, I would not, and have not done so for the simple reason that the gps system also provides the exact location of the mount which is most important when taking it to different locations around the country.  So I let the gps set the correct location but the wrong date and then simply reset the date within the iOpton menus.  Happily, even though the gps is still ‘OK’, it will not then try to reset the date incorrectly until the start of the next observing session.  The iOptron software appears to only set the date from the gps module once.  Good!

This does not seem to be a major problem when using this excellent mount and I am quite happy not to obtain a replacement gps module.

NOTE:  A colleague at the same field trip has one of the new iOptron ‘AZ Mount Pro GOTO’ mounts and this did not have any problems.

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© Ian Morison