Mount Query

[Tommohawk]

Hi all. Well I've been having a go in a newbie sort of way at astrophotography - equipment as per signature. It's certainly proving to be an interesting learning experience.

One of my biggest problems is driving the mount. I added the motor drive, and am slowly getting used to this. Its a bit of a faff that the RA doesnt have an unlockable drive like the Dec drive does. It means all the RA fine tuning has to be done by motor. That said I have got te be quite an accurate slewer (real word?) so can use the motor to do just the final fine tune pretty well.

Initially I found the drive to be very jerky - but I think this was simply because I had the RA clutch too tight. I took this apart - thanks to the guide posted here - and figured out how the clutch works. It's kind of a brake also, because if you do it up super tight it can allmost prevent movement completely, but the worm drive is powerful enough to overcome this so I didnt realise this was the case whn working manually.

The main problem I have is that my garden is really not well suited for AP! Theres a 45deg bank on the west side rising to about 8 meters, with a row or trees on top , and more trees to the south. It means I have to be very well organised, and resite several times during the evening. I get about an hour after dark to get M31, then have to relocate for Orion etc

So - the headache I have is good, quick, polar alignment. So far Ive just sighted throught the polar "hole" in the mount, and this is OKish for shortish exposures. But for multiple exposures is slowly drifts off.  I'm just about to order a polarscope, but even with that its going to be a right pain having to relocate, especially as I dont have the tripod legs extended, and have to grovel on the floor to peer throught the polar sight. The ground isnt very level, so I have to re-level at each new site also.

For now I'm trying to get what I can from my current kit, but sometime I will want to upgrade. I'm quite happy to track down targets by star-hopping and dont really feel I need a GoTo mount, but I'm wondering is there a mount that uses some kind of software/wizardry/wotever to do ultra quick polar alignment? I pretty sure that if anything this capable exists it would do GoTo also.

Does anyone have any thoughts/ideas?

[sidewind]

Hello Tommohawk

You have almost the same setup as I have in my avatar. What I don't understand is that you say that you have to finetune by ra motor, you have a clutch that youcan en and disengage at will.

I will give you, that you have things cut out for you, with the terrain.

If you want to stay at a EQ3, you have the option of an EQ3 synscan, while it is a Goto, it can also be controlled by a PC, and thus is very versatile, and yet not that expensive. I just googled it at FLO (first light optics) at 385£. If you buy that, you will have the option to have a mount placed in each of two places.

Hope it helps

[Tommohawk]

Hi Søren. Thanks for you comments. Regarding the clutch, what I mean is that without the motors attached you can use the manual cables to fine tune quite rapidly, but once the motors are attached you cant use the RA cable to fine tune because its trying to turn the motor which has a worm gear. Of course I can use the mount clutch and slew. The Dec axis motor has a release mechanism which can be loosened to that the cable adjuster will function.

Mounts generally, I have read around this a bit more and a few interesting points emerge.

Firstly, an Alt Az Go to may track OK, and could allow for photography - which is my interest - but because it doesnt rotate about the NCP axis, there is field rotation. So the star that is fixed would look steady, but the rest of the field would rotate and blur. I guess thats why I here talk of wedges - to achieve polar alignment. So thats ruled out - I deffo need an equatorial.

As far as I can see, all of the equatorial GoTo types still require polar alignment. I would really appreciate any guidance on this though. Specifically, are there any Synscan type mounts which dont require polar alignment? Given the issues I have with having to re-site through the evening, and the fact that the tripod isnt extended, (and I'm taller than 60 cm) this would be really usefull.

Any thoughts, anyone?

[Tinker1947]

My NEQ6 and this might apply to the HEQ5 have Polar Align option built into the handset that will Polar Align on any star so Polaris doesn't need to be in view, if you move the mount about PA is going to take most of your time up, if you could mark the spot where the tripod feet will sit so when it's moved it will be quite close for AP with just a tweek to get it close...

[Tommohawk]

My NEQ6 and this might apply to the HEQ5 have Polar Align option built into the handset that will Polar Align on any star so Polaris doesn't need to be in view, if you move the mount about PA is going to take most of your time up, if you could mark the spot where the tripod feet will sit so when it's moved it will be quite close for AP with just a tweek to get it close...

Fantastic! That would be a real help, because as you imply, from some positions polaris isnt in view.  I'm wondering how on earth that alignment works? I can see how fixing on any known star could allow calculation of the polar position, but how does the mount physically adjust for this? The mount looks like it has a conventional manual Alt/az adustment for polar set up, so puzzled how it self aligns.

[Tinker1947]

Fantastic! That would be a real help, because as you imply, from some positions polaris isnt in view.  I'm wondering how on earth that alignment works? I can see how fixing on any known star could allow calculation of the polar position, but how does the mount physically adjust for this? The mount looks like it has a conventional manual Alt/az adustment for polar set up, so puzzled how it self aligns.

Self align not a chance you need to turn the bendy bolts.....

[Tommohawk]

Just a quick follow on. Since starting this topic I've dismantled the EQ3-2 and cleaned and greased it - thanks to a guide found somewhere on here! What I've discovered is that if I clamp the RA clutch up very tightly it ovals the outer bearing slightly and clamps on the inner, and therefore prevents smooth rotation. The trick is only clamp only as much as required to pick up drive.

That said, it is still slightly jerky and this causes ovaling/elongation of stars in the same axis as the direction of tracking. This could be due to the scope wobbling slightly rather than the drive itself. It isnt possible to adjust the worm gear to completely eliminate backlash in all positions, because the wear in the gears is not completely even.