Another woeful account (sorry)

[palebluedot]

So I took my time setting up before dark (as much as I could) so that I could get straight down to business. At about 20:00, the brighter constellations were clear and I could start polar aligning, I had already calibrated the mount for 20:30. After battling with the very tight altitude adjustment bolts [Note to self: check they have not sheered] I got Polaris in the reticule, attached my camera and a small weight and checked the balance. Fired up EQMOD and set the mount to park, then aligned my camera so that Polaris was as close to the centre of the frame as possible. Started StellariumScope, connected and ran Stellarium. Then attempted to slew to M31, after being momentary puzzled at the lack of movement from the scope I realised that I had left the mount parked and that was quickly resolved. So off she went, round to M31 and I immediately took a randomly long exposure with the DSLR at 200mm to check the alignment... Bang on, the galactic centre was just where Polaris had been in the frame. After a small cheer I set about taking some test subs, just 30s each to make sure tracking was working, this is where my evening started getting bad. M31 was slowly disappearing out of the frame, up and to the right and after a while I noticed the sound of the mount had changed and there was not so much whining. I checked EQMOD and noticed that the dec was no longer changing, when I later checked the subs I had perfectly vertical lines for stars. I then powered everything off and started over, it looked and sounded like the tracking was working again, so I slewed back round to M31 and it was nowhere in sight. I checked the polar alignment and several times and Polaris was doing the rounds around the centre circle as expected, I made sure that my location was set correctly both in EQMOD and Stellarium after that I did not know what else to check. After an hour of faffing, the dew just got too heavy to continue and I gave up for the evening.

Does anyone have any ideas what else I can check next time out. Any help would be most welcome, I am sure that I have just missed something fundamental rather than it being a hardware issue.

[barkis]

RA and DEC clutches tight enough & adequately balanced,

Power supply sufficient, ie are you running the mount and everything else off one source?

Fundamental stuff I know, and I'm not suggesting you haven't checked through it all, but hey, it's forgetting the simple things that do the damage .

Ron

[palebluedot]

I know, and I am sure it is something simple. However, I did check and double check all of the above. I am using a mains transformer that dishes out 5A DC, nothing else is drawing from it, I'll check it with the multimeter, but I doubt it is that. I only had a DSLR and a 200mm lens on, I had to use a weight of the EQ3-2 because the others were too heavy, and it did balance.

[Edit] I don't think its slipping as it returns to the home position okay.

[jgs001]

Sorry to hear that Lee, I can only think of what Ron has said also I'm afraid. I know that others have had oddities like this when guiding, but that was a setting in the guiding software. I've had oddities a bit like that, that just didn't happen again.

[chrisshillito]

I assume this was unguided as you don't mention any guiding program?

If unguided then there is no reason why the DEC axis should be moving - after all with a perfectly polar aligned setup only movement in RA is required. Perhaps the fact that you are seeing movement indicates that your polar alignment was not good. How did you do your polar alignment? given you're using EQMODm why not use the tool it provides for alignment?

The altitude adjustment bolts really shouldn't be tight - make sure you undo one before tightening the other otherwise you will bend the bolts (the ones that come with the mount are quite soft - I replaced mine with stainless steel ones.

Also what version mount motor controller board do you have ? (EQMOD will display it in the message center on initial connection) If it happens to be V1.06 then you will need to apply a drift compensation value of 3 in EQMOD.

Chris.

[palebluedot]

Thanks Chris, Unguided is correct.

I was wondering about the DEC, but then decided that EQMOD wouldn't know that I wasn't correctly polar aligned, so it should not try and compensate. Agreed that it could have been off though. I will have a go at polar aligning though EQMOD next time.

Point taken re-bolts, I had already ordered replacements from Astro Developments.

Thanks for the controller board tip, I'll check it out.

[Edit] You are definitely right about the DEC not being required. I should be finding out why I was getting movement in the first place.