HEQ5 alignment trying to slew below the horizon

[mrjolly]

Hi,

Just had my second play around with my HEQ5 which went slightly better than the first but had a problem during one of my attempts at 2 star alignment. The controller picked Sirius as the first star to align to which I picked, it then slewed roughly in the right heading but then carried on a bit further than necessary and started heading below the horizon! I quickly brought it to a halt (by pressing the esc button in a panic) in case of a collision, moved back to home position and tried again on some different stars which went a bit better.

A bit later I decided to try aligning with Sirius again and it went roughly in the same direction and also got roughly the correct declination (although still a bit off.)

Is there anything I could have done to have caused it to try and go below horizon? I'm pretty sure I've got the latitude & longitude entered correctly (got it from Google Earth) and the time and date were entered correctly. Once I'd finished the alignment, it was fairly accurate and picked out Jupiter and M42 with no problem so once aligned it seemed to know where and when in the universe it was.

The only thing I can think of is that when starting alignment I didn't get home position correctly but I had Polaris in the finderscope and eyepiece so don't think it was that.

Apart from that, it went better than my first session when I just gave up and slewed manually! (Still struggled to find M31 though as it wasn't that accurate so gave up and slewed by hand!)

[Jessun]

So when you started you had the weights down and telescope pointing north? You're not necessarily pointing at Polaris in this position, since polaris travels around the NCP. But sure, roughly in that direction.

/Jesper

[mrjolly]

It was pretty much in the right direction with weights down and north pointing, the only thing I can think of is that maybe it guessed Sirius was a bit lower than it probably was!

I'll double check my lat/longitude settings tomorrow to make sure I've got those entered okay.

[ronin]

Double check all the data entered, assume that something is wrong.

Polaris is only about a degree off of the Celestral Pole so that would be the error when it slewed, not enough to make it point below the horizon.

Suggest that you write down everything, then check it, then re-enter it.

Would also suggest checking the alignment procedure, if I recall it doesn't appear that logical so you may have skipped, or missed, something.

Being in Kent your Longitude will most likely be East or +ve, most of us are West or -ve.

Would expect something like 50.5N and 0.5W (+0.5).

[Jessun]

Hmm... the software would not suggest a star that is below the horizon... The mount is actually not guessing about the position of Sirius in relation to your position, it knows that position to the arc second, but since it doesn't know where it's pointing at startup it IS guessing that you indeed started from the home position as best you could and that you got the time, date and position spot on .

A relatively small error in time or place can throw it miles off so to speak.

/Jesper

(The comment about Polaris and NCP was just to check that the OP hadn't swung around in RA to center it precisely, in which case it could soon knock the tripod away going for that first star )

[Extreme Fencer]

Same thing happened to me the second time i had my HEQ5 out when alligning it asked to start from home position.

I had weights down scope up.

Started 3 star allignment and the scope headed for the ground when i selected Sirius hit the escape key a bit rapid.

I put the scope in a rough home position and left the clutches off and set the scope back to home position on the handset, once the mount had stopped i engaged the clutches.

Turned off the mount and started again, but went straight to allignment ,didn't bother with start from home position.

I had alligned the mount before hand and it found the allignment stars fairly well from there on

[Steve Ward]

Silly question , but did you remember 2013 . . . ?

I inputted 2012 the other day through 'habit' and nearly had kittens when the mount went "walkabout" when it's usually within a gnats of the first star . . .

[Jessun]

There are sometimes bugs in the software... Sirius may not work on one particular day, anything is possible in the digital world...

/Jespe

[mrjolly]

Silly question , but did you remember 2013 . . . ?

I inputted 2012 the other day through 'habit' and nearly had kittens when the mount went "walkabout" when it's usually within a gnats of the first star . . .

I was lucky today, just before entering the date I remembered to enter it as m/d/y format, looked at the clock and saw it was 2/2/2013 which was nice!

Reading some of your replies has just made me think of something (which doesn't happen often!)

I can't remember the scope asking me for home position during the alignment. This wasn't my first attempt at alignment, the first time I tried wasn't successful so I moved back to home and selected 2-star alignment again without powering down.

Was it using the data from my first unsuccessful attempt to guess where Sirius was? Maybe next time when I make a mess of alignment I should power off & on again to reset everything.

[Herbig]

Did you put the date in the American way?

[Jessun]

I can't remember the scope asking me for home position during the alignment. This wasn't my first attempt at alignment, the first time I tried wasn't successful so I moved back to home and selected 2-star alignment again without powering down.

Yeah it does ask doesn't it, as far as I remember from using a HEQ5. Start from home is pretty safe so long as you place the mount and scope in that way. You can do a start from home, do a one star alignment, move with you handset to center, and then ask the mount to park. Next time you start from park, even star one should be pretty spot on so long as you PA is OK and that your cone error isn't brutal.

/Jesper