polar alignment qustion

[muletopia (Chris)]

Hello Folks,
I have no regrets about not following the general advice in this thread, for my first real telescope I bought a Takahashi Mewlon 210 and put it on a a
HEQ 5 pro mount. The Skywatcher tripod was quite useless so the mount was put on a very solid pier bolted to a suitably large mass of concrete.
Iterating through the mount's three star and polar alignment routines the PA error has been reduced to 4 and 11 seconds in azimuth and elevation respectively. This means that mount goes to objects fairly accurately and faint objects found in the main scope at 100 magnification.
(Omega Centauri at 400 times using a Losmandy G11 on an excellent winter night was a sharp well resolved treat to behold).

For the alignment a 20 mm reticle eyepiece was used, the centre square of which is about 12 seconds wide (Granted the 2415 mm focal length the magnification is 120.75.) and the alignment stars were defocussed so that they just fitted into that square and all final placements were with N and E movements.

I now want to do drift alignment to reduce the PA error.

My question, what sort of drift rate might I expect in declination? This would tell me how patient I will need to be.

I hope this not a silly beginners question.
Cheers
Chris

[blink138 (Pat)]

it will drift quicker with greater magnification and thus you should be able to do the adjusments quicker on the fly
centre it with a lower powered eyepiece first and then drop in shorter focal lengths to keep it there
pat

[BeanerSA (Paul)]

Is this for purely visual use?

[muletopia (Chris)]

no

[raymo]

Hi Chris, I would love to know why you thought the tripod was useless.
It is used happily by many many people. Mine is rock solid with my
8" f/5 Newt on it, and occasionally is used with a 10" f/4 on board.
The mount would be borderline for photography with the Mewlon, but
the tripod would cope easily.
raymo

[muletopia (Chris)]

Raymo,
My sad history with the tripod. I bought the mount and tripod new with the Mewlon.
Set up in daylight to align finder and scope as per Takahashi's instructions, having done up the screws on the legs reasonably finger tight. Suddenly the south leg (supporting the counter weights) just collapsed. I thought that I had not done up the screw tightly enough so I did it more tightly. This allowed me to make the alignment.
So it came to set up for viewing . Again collapse, so I put worm drive clips on the lower legs beneath the castings of the upper section.
This worked for several sessions of setting up. Then one evening the thread in the south leg casting stripped.
The threaded hole passed through a void in the casting. No wonder it stripped. I complained to Claude who in turn complained to Tasco and in a short time a new tripod leg arrived in Kojonup, points to Claude.
I put in the new leg, but the original rubber washers were not replaceable (where the leg fits into the mount). I resumed using the mount, with the worm drive clips which stop collapse but won't help wobble in general.
With the new leg in place I disassembled the failed leg with the idea that when I next had time in Albany I would get a 10m helicoil to produce a spare leg. BUT all the legs have depressions where the tightening screws press on a small plate captive in the casting, the legs are just not heavy enough, alfoil comes to mind.

All up, really shoddy.

Chris

[raymo]

Sounds like you had reason to be unhappy. I believe this to be a rare occurrence. I've never heard of this problem before. With mine I just turn the screws until I feel contact, and then a further quarter of a turn. With my little 80mm scope I have to have the legs fully extended, and it is still
sturdy. I suppose there has to be a lemon now and again.
raymo