Another drift alignment question

robin · #1 02-08-2005, 10:22 PM

Can someone please help me out here with regards to drift alignment.....

Lets say I've got the scope roughly polar aligned & centered on a bright star on the meridian with an illuminated reticle, around the zenith say:I let it go a couple of minutes,it starts to slowly drift UP so I move the azimuth control to make it move to the RIGHT...right??
My question is...by how much do i move it to the right? The same amount as it has drifted up?...
Appreciate any suggestions.

[1ponders] (Paul) · #2 02-08-2005, 10:33 PM

I don't know about UP and Right robin, I nudge my ota gently north or south to see which direction is needed to return the star to the center. If I need to move the scope north then the mount needs to be turned east. If South then the scope needs to go west. There no correlation between the distance moved but the faster the star moves off the center of the reticle the further you are away from your desired alignment position.

Now the tricky part is as I'm sure your aware is regaining an alignment star in RA direction after you've adjusted the mount. I like to set my RA speed to about 16X so that when I adjust the Az control I can use the hand controller to keep the star in the field of view. That way I don't have to search for another star.

robin · #3 02-08-2005, 10:51 PM

Thats interesting Paul....I read a book recently that said you should move it the same distance it drifted then,using your hand controller,re-centre it & wait for it to drift again.
My drift star ,through a 9mm reticle tends to drift real slowly 'up' in the field.

[1ponders] (Paul) · #4 02-08-2005, 10:56 PM

The distance drifted will depend on how long you wait for it to drift and the inaccuracy of your initial polar alginment. Are you meaning that you adjust it the same distance and same direction of the drift?

[1ponders] (Paul) · #5 02-08-2005, 11:00 PM

I've just had a bit of a re-read of one of my drift alignment guides and both of our methods end up doing the same thing. For altitude adjustment, move the star back to the center, for Azimuth move the star away from the center.

robin · #6 02-08-2005, 11:03 PM

If it was to drift,for arguments sake, 1cm 'up' in the field, then I'd move the wedge to make the star move 1cm to the right in the field then using the hand controller, re-centre it & watch for the next drift.
Hope I'm not confusing you too much here Paul!

http://www.darkskyimages.com/gpolar.html

beren · #7 02-08-2005, 11:18 PM

Ahhh Robin i had this written down somewhere with which way to turn the Superwedge knobs etc but i cant find my notes, always seem to forget but when im at the scope it all comes back . Its all about trail and error , i use a stopwatch which gives me a idea on how much to adjust etc.The difficulty with the superwedge Alt adjustments is the freeplay when changing directions , this is critical for the fine tweaking needed.

This a good link for dift aligning froma SH perspective http://members.iinet.net.au/~rog1/astro/info/polar/

[1ponders] (Paul) · #8 02-08-2005, 11:50 PM

I didn't even want to go into the freeplay in the meade wedges Stuart

Basically Robin as I said I don't worry about up and down. I stick to the NEWS principle. If the star is moving North then I need to rotate the mount more to the east. If the star is moving South then I need to rotate the mount to the west. Oh and its surprising at time how much you need to move it, even if your star is only moving slowly away.

gbeal · #9 03-08-2005, 03:15 PM

If you have K3, it is written there as well

robin · #10 03-08-2005, 05:32 PM

Thanks for your help guys.Appreciated it.

[1ponders] (Paul) · #11 03-08-2005, 07:01 PM

Robin do you have an LPI or ToUcam? Oh and a laptop

robin · #12 03-08-2005, 10:17 PM

I have an LPI Paul but there's a toucam on order.Got a laptop too mate.

[1ponders] (Paul) · #13 03-08-2005, 10:54 PM

Then download K3ccdtools V2

(You can use either the LPI or the ToUcam with it.)

You get to use it fully funtional for 30 or 35 days. It takes a bit of getting used to to learn it, but i wouldn't be without it now. When I first started to learn to drift align with a reticle it used to drive me nuts trying to work out which way to turn the azimuth. Especially as I needed to wait for so long when it was nearly there to see the drift. I find it a dream now using the ToUcam and K3 with the drift explorer. Unless its almost spot, on I can see any drift in a matter of second and adjust for it. And if I go the wrong way its also obvious in a few seconds. And because I'm working with the accuracy of electronically detected pixels rather than the old astigmatic eyes I can get much greter accuracy in polar alignment much more quickly.

From what I understand you can do the same thing with guidedog but it doesn't show you the dec response graphically only numerically. My personal preference is for visual aids, but that's just me. You might find the digital readout fine to use. Give each a go and see how it works out.

BTW have you done any wedge improvements? I found my 8" meade a pain to azimuth adjust 'cos of the binding between the wedge surface and the tripod top. I followed the advice in a previous post and placed a circle of teflon or acrylic between the two and it made the Azimuth adjustment much smoother with next to no snagging.

http://www.iceinspace.com.au/forum/s...ght=superwedge

robin · #14 03-08-2005, 11:42 PM

Cheers Paul...I will definetely look into K3ccd tools & the tripod/wedge teflon issue. I've read that placing a cd in there is a good option too but i havent tried it.Its meant to really make the wedge glide easily & smoothly.I reckon it'd break though.

beren · #15 04-08-2005, 01:06 AM

Robin i fitted some mods to my wedge to make it smoother in operation , you might be able to rig something yourself but theres a kit available to replace the Altizmuth controls http://www.optcorp.com/product.aspx?pid=3111 , this cuts a lot of the backlash and is certainly a big improvement , there is a bigger kit that replaces the altitude gear as well and better machined crossbars http://home.cfl.rr.com/mitty/Combo_SLO-MO_Kit.htm

I used a thin cutting board and routered out holes to match the spacing for the bolts that hold the wedge to the tripod and their movement , it works very well and acts as a shelf for stuff as well

robin · #16 04-08-2005, 09:33 AM

Just had a look at it Stuart, looks interesting.It'd certainly take a lot of the backlash problem away.

beren · #17 04-08-2005, 10:05 AM

The Altizmuth mod does take a lot of the free play out, but being a threaded rod your not going to get a 100% fix , i highly recommend this mod the altitude one doesnt give the same apparent improvement but still helps . My wrists are still on the mend trying to dismantle the stock knob handles to install the kit but its fairly easy just need to use the missus hair dryer {ok its mine LOL} to weaken the LOCKTITE substance that holds the knobs in place , some spanners, a can of lithium grease and a dremel hobby tool for the altitude mod {makes it easier}.One thing i noticed with my superwedge is the side panels arent completey square , suspect the connecting surfaces need machining to correct the level {check the rest of the Mitty site for more info about this}, this might put stress on the structure to some degree .