ASGT problems again!

Just another tip. For cleaning off old grease from mount parts the best solvent I have found is good ol' unleaded petrol. Kerosene or diesel will work quite well too. Soak the parts in a tub of this for a couple of hours and it will dissolve most of the old grease. Just remember to rinse them well in soapy water afterwards.

It goes without saying to take care when using such a flammable liquid (get an adult to help if your a kid or a responsible adult for everyone else :lol:) Also dont let any get near electrical parts.

Thanks for the tips guys. If the autoguiding works out I think I'll have a go at the gears. Should be fun, haven't done any engineering since college.

I take your point on the performance Dave. This is a relatively inexpensive mount. I used to get 1.5 to 2 minutes unguided before though.I have a feeling it stopped working well when on a polar alignment it pointed the scope straight into the ground & whacked it off the tripod. I don't think it ever worked too well after that.

One clue that there could be a problem is that I used the small refractor by itself once to debug this. Each successive Polar Alignment routine just shifted the goto errors by another 6 degrees in the wrong direction.

Last Saturday we had clear skies and I got a run of about 30 x 45sec shots of M31 as a test of the tracking. Strangely enough about 7 or 8 of them were OK. Could that possibly be periodic error? It seemed to be mainly on the Dec axis though.

Anyway, I'll be keeping the mount even if I don't get the tracking sorted. It's stability is still great & I guess the learning curve on any other mount would be substantial as well.

Cheers,


Trev

Good advice Dave.
I didn't have any petrol to hand so I filled a small paint tray with WD40 and used a paint brush to coax the old grease from the cogs. However my first choice would also be petrol for the cleaning part, I've done this many times restoring old motorbike engines, and it beats any other chemical cleaner hands down. For the muppets - don't set yourselves alight. This is really easy, it's not a difficult task - something that can be done in an afternoon, and should form part of everyones maintenance schedule. If you don't look after your kit it won't reward you!!

Just out of interest, what focal lengths are folks using on this mount?

The reason I ask is because I assumed it was the same scope (and focal length) that ye are all using on the mount. But don't forget, the longer the focal length, the easier any tracking errors will show up.

This is why a 3" refractor will give great rouind stars at, say, five minute exposures but they go all blobby with an 8" SCT. Its not the aperture, its the focal length...

Dave

Hi Dave,

I'm using 480mm from the refractor. Will probably use the SCT at 1280mm to guide.

Trev

Dave,

I can autoguide happily at 2350mm (F/10 on the 9.25" SCT). You are dead right though the shorter the focal lenght the less critical guiding can be.

BTW guys, I started writing up an article on guiding and all of the techniques that go with it. Instead of a short article I've ended up with a short book!! I should have it finished and published on the web next week. It not only contains the techniques needed for good guiding but also includes a tutorial for guidedog explaining what all the different parameters do and how to make best use of them.