HEQ5 mount help please

[Leebert]

After a couple of observing evenings in the back garden, I am slowly getting more used to setting up the 200p on an HEQ5 but I am struggling with some bits of set up and subsequent GOTO and tracking.

After seeing a few videos on you tube and tutorials on Astro Baby's web site, I think I have polar alignment sorted but, as I am having other problems, I may be aligning on a star near Polaris!

Once I think I have aligned the mount and put the scope into the home position, I go through a two star set-up procedure which is successful and then GOTO M92. Both nights that I have set the scope up, M92 has not been in the centre of the eyepiece but on the edge. A whizz round to M31 and it's not even in the eyepiece. Finally, I tried a stacked photo of M92 and the cluster was working it's way left across each sequential photo. There were star trails too on a short exposure (20 seconds) so something definitely isn't right!

Can anyone suggest and step by step guides of what I need to do to check the mount up from scratch please? I guess that would include polar scope alignment and the adjustment on the dovetail so that the tube is in line with the RA axis - or have I gone too deep?

I have leveled the mount (by eye only) and balanced the OTA in both axes as best as I can.

Possibly related points... When balancing, moving either axis is smooth but not totally free (it can't be spun around) and, when locked off, there is a tiny amount of play in the RA axis. I can't really see the movement but I can feel it. The Dec axis has no movement whatsoever that I can detect. Are these both typical?

Sorry for the rambling post. Thanks in advance for any help

[Leebert]

Nobody?

[malc-c]

Even with the high quality motors in the HEQ5, there is still backlash and other errors inherent in the system, but there should be no movement in the axis when locked as you describe. I read somewhere that the encoders on these mounts are "virtual" in that the controller effectivlly counts the number of steps each motor has made between points rather than read a hardware encoder. How true that is I don't know but it would go some way to explain why when slewing from one side of the sky to another the target is slightly off centre.

There has also been some debate over having to have the mount perfectly level, and IMO I beleive it helps. It's worth using a spirit level on the tripod, then spend some time in the day to balance the OTA in all directions including in rotation within the rings (have a look on Youtube at Astronomy Shed's excellent videos). Then you need to get Polar alignment as close as possible. One thing that can cause problems here is if the polar scope is out of collimation. Again Astronomy shed has some excellent informative videos on how to do this.

Lastly, once you have the scope leveled, balanced and aligned, perform a 3 star alignment, as this will help the mount work out the cone angles and hopefully should give better goto location when using a wide field, low power eyepiece, but you still might have to tweak it slightly to bring it in dead centre

Hope that helps

[Leebert]

Thanks very much for the advice Malc-c. I will be trying a few things next dark night

[g0ibi]

I echo what Malc has said, the set-up videos in the Astronomy Shed are brilliant, it's the little things that count! Until I had seen the video's I struggled with polar alignment, but when he said 'as long as Polaris is on the circle, it does'nt matter where!' then I started getting it right first time! I always use a 3 star alignment to set up then go straight to a known star and check. Good luck and clear skies..

[Gunnar]

Hi

You may be aligning to a star near polaris! When you polar align you can try looking at polaris along the side of the mound to visually see if the moun/body is pointing in a direction close at polaris. Adjust to left or right until it does. Then start looking in the polarscope and fine tune polaris in the circle.

This always take polaris inside the edges of the polarscope for me so it`s easy to find.

Gunnar

[malc-c]

In addition to above, if you have a laptop install EQMOD and either make a EQDIR cable or purchase the serial PC cable and hook that up to the synscan / handset respectively. EQMOD has an excellent utility for aligning the mount, in that you centre Polaris on the cross in the middle of the polarscope with the bubble at the top or bottom of the circle, then using just the altitude bolts place Polaris in the bubble. Then you click on a button on the application and it rotates the RA to the exact position Polaris will be in it's "orbit" around the NCP. You then use the alt/azi bolts to place Polaris in the bubble - job done !

[bibbsy]

hi lee,

glad you posted this question as i'll be in the same boat this week when the mount arrives,i'll follow this thread closely

[Leebert]

Thanks for all the helpful replies

I had a look at the Astronomy Shed videos and they are very helpful and easy to understand.

Arned with this, I carefully and methodically set up the tripod, leveled it and pointed it to the pole using a compass.

I popped on the mount and set the home position as per the Astronomy Shed video and went through the 3 star alignment which was sucessful first time.

I typed in M92 and there it was right in the centre of the EP. I left it for about 10 mins and it was still in the centre

I then spent the rest of the session observing lots of new stuff such as the Blue Snowball, Uranus and Neptue whilst grinning like a kid on Christmas morning.

Result - thanks for your help all

Cheers,

Lee

[JamesM]

I'm glad you have managed to sort out your difficulties there Lee, it's always a worry if you think the equipment might be at fault.

Not to hijack this thread but I wonder if it is possible to clarify the correct answer to Malcolm's question regarding the need to level the tripod. It is my belief that the tripod does not have to be completely level to permit accurate three star alignment, as the adjustments you make to centre each object during the alignment process would take account of any tripod discrepancies. It is when you are tracking an objection during long observations or performing long exposures that the tripod need would need to be accurately leveled. I always level my tripod as part of my set up procedure but I would like to know what others think.

James

[Ant]

A tripod does not have to be level - it just helps simplify the adjustments in the polar aligning routine.

The only important thing is that the polar scope (and therefore the mounts) points to the NCP.

Cheers

Ant

[malc-c]

Lee, glad to hear you have had a decent observing session at last

Personally I think having the mount level does make a difference. Whilst it probably doesn't make a deal of difference if the N leg is out as you would compensate by adjusting the bolts to bring the mount up or down to get Polaris in the correct position, but I think if one of the other legs were out then its going to cause issue with the DEC position... Bit hard to explain in words.... lets say you have the mount perfectly level, in the home position. Now rotate the DEC to point East or West so that it's at 0 degrees. The OTA will be perfectly level. Now drop one of the rear legs opposite to where the scope is pointing - the OTA is now pointing upwards. OK in reality you wouldn't be far out as in practice you would try and place the mount reasonably level by eye, but if the mount was too far out I would predict that the errors the goto would encounter would confuse it too much to make the corrections.

One day I might actually try this out and see if having the mount well out of being level makes much difference to the alignment procedure. My theory is that it will, otherwise why did having the mount level and squared prove so successful for Lee

[Leebert]

Thanks - it was a great night

I might try a night setting it up as carefully but without leveling and see if there are any changes.

Looking forward to capturing and seeing loads of new things