Preference for marking on mounts?

[baileys2611 (Simon Bailey)]

Hi everyone,

I'm getting closer to an accurate polar alignment on this MI-250

As I get closer, I'm thinking of marking some spots so I can do some more testing, move things a little and re-set back again - but wondered what is the general practice for marking? Masking tape or some other kind of tape? Is there a nice silver metallic tape that has a good adhesive or do people just use permanent marker on the mount itself.

Any preferences?

[Bart]

I have used removable spots, about the size of a 10 c piece and are bright green in colour. Use a fine Biro to mark it then a Stanley blade to cut it in half if you stick over the two moving sections of RA and Dec. The finer the Biro mark the higher accuracy you will have when realigning.

[alocky (Andrew lockwood)]

Interesting- I assume you'll always have to fine tune the alignment after each setup? I'd be very interested if anyone ever gets their mount routinely into an alignment good enough for imaging this way?
My 'trick' was to stop during disassembly and take a very careful measurement of the apparent magnetic bearing by holding a compass against a repeatable spot on the tripod. This accounts for the local magnetic distortion caused by the steel in the tripod - which in my case is mostly aluminium anyway. Then when I set the thing up I align the tripod and I'm usually well within a degree. I did 'hole it in one" once!
Caveat is that I'm a geologist, so the compass is actually my trusty old Brunton, which is a bit better than the compass we used to get with our school shoes back in the '70s..
Cheers
Andrew.

[bojan]

For my transportable mount I use holes in concrete pads, where the legs of the tripod go.
No need to re-align for less that 500mm FL.

[Wavytone]

When I had an eq mount what I did was

- align it the first time accurately, using the stars;
- leave it out overnight,
- the next morning set the mount with the dec axis horizontal with the scope on one side, swing it down till the field of view intersects something like a building or fence where you can put a mark. In my case it was the back fence.

Next time you set up use the scope to align the mount by rotating in azimuth to centre the mark in the scope.

Even if the object is distant or inaccessible you could take a photo and put a mark on the so you'll know where due north or south is.

[baileys2611 (Simon Bailey)]

A few variations to think about. Thankyou.

It's permanently mounted on a fixed pier, the only movement I will be doing is moving the scope off and back on, adjusting worm drive tension, etc.

Different topic - Getting accurately polar aligned is not easy!

I read somewhere that PEMPro was a good option.

I've done drift alignment and am close, Tpoint says within 8 arc-minutes on the horizontal axis and within 7 arc-seconds on the vertical (must have been a stroke of luck) but that might not be such a good measure, I've read that TSX takes a lot into account when it builds a super model so it might be averaging out errors and such.

Has anyone used PEMPro and had good experiences polar aligning?

[Bart]

Use Sharpcap, polar alignment utility is great.

[baileys2611 (Simon Bailey)]

Sharpcap looks like it's freeware (under some complicated license thing but at no charge).

Is that right? Looks like a pretty good utility actually.

[sil (Steve)]

Marking mounts/positions, for long term I use a thick silver marker first to draw a prominent thick line across a join line and when its dry I use a very fine black marker on top to mark the precise alignment position. Gives me a good clean repeatable position marker, no tape to unstick from dew or gather dust etc into a join and is a highly visible marker in any light/red torch.