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Adrena1in
sage
Reged: 09/02/07
Posts: 275
Loc: Hampshire, UK
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Hi all. I'm still getting conflicting information with regards to drift aligning, and for correcting east/west errors on the mount. (This is with regards to the Northern Hemispere by the way. Let's imagine I'm roughly aligned on Polaris, and have the scope pointing south at roughly the meridian and at 0 degrees DEC.)
A lot of sites on the web say this: "If the star drifts up, adjust your mount to make the start move to the right." But others say: "If the star drifts up, your mount is aiming too far west." Now, I may be wrong, but I see those comments as conflicting.
In the second comment, it mentions the mount pointing too far west, or left, (when standing by the mount and facing north). Therefore, with the scope pointing towards the south, it's going to be pointing too far east, )or left when standing by the mount and facing south). Move the mount east and the scope will move west...to the right. Therefore, the star will move left.
I do my drift aligning with eyepieces set up to give me an actual image...not a reversed one. So WHICH is correct? Which way do I need to move the star in the south if it drifts up?
(No wonder I'm reluctant to spend much time doing it if I don't know for sure which is the correct way!) 
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Phenix 102mm f/5.9, Phenix 127mm f/9.5 and Orion ST80 f/5 refractors on EQ5 with GOTOStar
Phillips SPC900NC, Meade DSI-C, Canon EOS 450D with 18-55mm IS, 28-105mm and 75-300mm plus 2x TC
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walt r
Carpal Tunnel
Reged: 02/13/07
Posts: 2416
Loc: Doylestown, PA
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When I first learned to do drift alignment I spent a few hours working it out and keep notes on what I did. Then I wrote a quick guide to use for my set-up (Mak-Cass with diagonal).
After making an adjustment to the mount, note if the drift is slower or faster. If slower than the adjustment was in the correct direction, if faster then wrong direction. Use a reticle EP and a clock (with seconds) and note the amount of drift in the same unit of time (say two minutes) for uniformity in judging drift speed.
The first time doing a drift alignment is difficult and time consuming. Spend the time, take notes and drift alignment will become fairly easy.
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Walt
Obsession 18" f/4.45 #1370 AN/SC
MK67 Deluxe 6" f/12 Mak-Cass, Super Polaris GEM, JMI MicroMax DSC
DIY 60mm f/6 Achromat
Cookbook 245 CCD
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Qkslvr
Pooh-Bah
Reged: 06/23/06
Posts: 1052
Loc: NE Ohio, US
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I used my camera and took timed shots of a bright star.
I also put 3 small holes on my driveway, so my scope always goes back in the same spot, and I don't have to bother with it anymore.
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Mike
N8/CG-5/40D
Coming sometime/Maybe FrankenRebel
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imjeffp
Senior Space Cadet
Reged: 09/30/03
Posts: 4422
Loc: Cedar Park, Texas
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The answers you seek may all be found here. Pete shows you how to do it, and why it works.
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Blog
ST80 • AT80EDT/LXD650
ETX-90/DS-2000 • 10" LX200 Classic ("The Quarter-Meter Telescope at the Heritage Park Observatory")
SPC900NC • DMK21AF04 • Digital Rebel XT
  
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Jared
Carpal Tunnel
Reged: 10/11/05
Posts: 1871
Loc: Piedmont, California, U.S.
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If you move the mount so the star moves to the right in the eyepiece when the scope is pointed South, then you are shifting the telescope to the West (and therefore the mount to the East since the mount is always pointed North). This assumes that you are using a telescope where the light comes out the back and have a star diagonal in place--such as an MCT, SCT, or Refractor.
No contradiction in the instructions. They are both correct. Shifting the mount to the East when the scope is pointed South will cause stars to move to the right in the field of view if you are using a star diagonal. If you are looking straight through at an inverted image, obviously stars would move to the left instead.
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- Jared Willson
- Fluorostar FLT-110 w/ TEC optics
- Vixen VC200L
- Astro-Physics Mach1 GTO
- Stellarvue SV80S
- Takahashi Teegul SP Mount
- STL-11000
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Adrena1in
sage
Reged: 09/02/07
Posts: 275
Loc: Hampshire, UK
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Quote:
I also put 3 small holes on my driveway, so my scope always goes back in the same spot, and I don't have to bother with it anymore.
That's what I'm going to do on my patio out back, once I've got it set up spot on. 
Cheers for the replies...I guess this is just one of those things which isn't necessarily going to make sense in my mind, as long as I just know which way to turn the mount to counter the drift error.
From whateveryne's saying, when turning the mount east, when looking at it from above, this means turning it anticlockwise? Because only by turning it anticlockwise are the stars going to move right in the eyepiece.
(I've probably just got the wrong spatial perceptions in my head here. I thought that to turn the mount east, this meant standing by it while facing north, and shifting the northern end of the mount to the right, or clockwise, because, when facing north, east is to the right. (It STILL makes sense to me to move it that way if the star drifts up, but hey, what do I know!  ))
Cheers.
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Phenix 102mm f/5.9, Phenix 127mm f/9.5 and Orion ST80 f/5 refractors on EQ5 with GOTOStar
Phillips SPC900NC, Meade DSI-C, Canon EOS 450D with 18-55mm IS, 28-105mm and 75-300mm plus 2x TC
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nimthor
member
Reged: 02/10/08
Posts: 50
Loc: Durbanville, South Africa
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I worked out all the maths befre I did drift alignment for the first time (this is only about a month agao ;-) and thought it was going to be easy. Well that was until I actually tried it out at the scope the first time! To get around this confusion I did the following:
1) Set up the scope roughly polar aligned (I do this with a compass as I live in the SOuthern Hemisphere, but you have Polaris, which makes things so much easier),
2) Turn you azimith way out with your adjustment screws either west or east, just make sure you know which way. So if you turn the adjustment screw and the front of the telescope moves to your left you are moving it to the west and vice versa for east.
3) Point scope at the intersection of meridian and celestial equator
4) Watch for drift in dec after you have set up your reticle so it lines up to the RA direction. Note the direction of drift. In order to correct you need to turn the adjustment in the opposite direction you used to turn it out of alignment earlier.
5) Make a note of the drift and which way you had to turn it to correct. This way you have experienced it and can do it anywhere if you forgot your notes.
As said before in the thread, the quicker the drift, the more you need to correct.
Hope this helps.
Clear skies,
Charles
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Telescopes:
Meade LXD75 SN8, Orion 80mm Guide scope, Celestron 60mm Alt/Az
Camera's:
Pentax K1000, Canon A700
Binoculars:
Safeway 16x50, Tasco Lumina 10x25
"Never underestimate the predictability of stupidity"
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Adrena1in
sage
Reged: 09/02/07
Posts: 275
Loc: Hampshire, UK
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AHA!
Just had a lightbulb moment, and I get it now. I see where I was going wrong. I had a vision in my mind, of looking south, and there being an arc, rising from the ground in the east, flattening to horizontal at the meridian, then arcing back down to the ground in the west. I then had a vision of the arc my mount making when it's adjusted too far west, (i.e. the scope facing too far east), of being on the eastern or left side of the star-arc. THAT was my mistake. The arc my scope would trace would actually be on the west side, or the right. I see now why the star would drift down were that the case.
(I've spent hours thinking about this...it's great to suddenly achieve clarity.)
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Phenix 102mm f/5.9, Phenix 127mm f/9.5 and Orion ST80 f/5 refractors on EQ5 with GOTOStar
Phillips SPC900NC, Meade DSI-C, Canon EOS 450D with 18-55mm IS, 28-105mm and 75-300mm plus 2x TC
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MartyT
professor emeritus
Reged: 09/28/07
Posts: 544
Loc: Kansas City
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Too much thinking for my little brain!
I use WCS software and a Meade DSI camera and it tells me how much to move the mount and in which direction...
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Celestron CGE / C-11 (CGE-1100)
Megrez 90 FD APO / 0.8x FR/FF III
QHY8
Modified Canon 350D (Baader UV/IR Filter)
DSI Pro (guider), SPC900NC
ETX-125AT
Meade 12" Lightbridge
Astronomical Society of Kansas City
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Adrena1in
sage
Reged: 09/02/07
Posts: 275
Loc: Hampshire, UK
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I actually spent a little longer aligning on NCP using my polar scope last night. It's never really worked very well, but I've adjust it and it came to pretty good effect last night actually...was probably the closest I've ever had it, and it only took a few minutes. Didn't practice drift aligning though...I wanted to test a 10mm wide-angle lens a friend lent me to shoot the Milky Way.
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Phenix 102mm f/5.9, Phenix 127mm f/9.5 and Orion ST80 f/5 refractors on EQ5 with GOTOStar
Phillips SPC900NC, Meade DSI-C, Canon EOS 450D with 18-55mm IS, 28-105mm and 75-300mm plus 2x TC
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Jared
Carpal Tunnel
Reged: 10/11/05
Posts: 1871
Loc: Piedmont, California, U.S.
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Quote:
I actually spent a little longer aligning on NCP using my polar scope last night. It's never really worked very well, but I've adjust it and it came to pretty good effect last night actually...was probably the closest I've ever had it, and it only took a few minutes. Didn't practice drift aligning though...I wanted to test a 10mm wide-angle lens a friend lent me to shoot the Milky Way.
One thing I'd recommend depending on the quality of your polar scope. I found with my last mount, the polar scope was slightly off but consistently so--always off by a tiny amount in the same direction. By doing a careful drift alignment one time and then shimming the polar scope with scotch tape so that it matched the mount I was able to get good results from then on using just the polar scope alone. No more need for drift aligning. Ten minute subexposures would be consistently free of noticeable field rotation even with a full frame chip.
Of course, this assumes a reasonably good quality alignment scope capable of providing consistent results. In my case, it was a Losmandy scope in a GM-8 mount and it really made a difference. I was able to completely give up drift aligning in most situations.
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- Jared Willson
- Fluorostar FLT-110 w/ TEC optics
- Vixen VC200L
- Astro-Physics Mach1 GTO
- Stellarvue SV80S
- Takahashi Teegul SP Mount
- STL-11000
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