Compass usage for alignment

I know that a major part of my issues with alignment have to do with the fact that I am having to set up on very uneven ground and am eyeballing Polaris as well. I think I may be able to fix the uneven part by installing another level on my mount, but so far, I have been unable to reliably get set on polar north. Something that my husband mentioned was to take a compass, get it placed on my mount (probably not permanently, but placed where the rail of my scope would go) and figure out where my true alignment would fall on the compass in degrees. This way, I could mark that spot on the compass when I get my mount perfectly aligned, and so that the next time I went out, I would just have to make sure my scope was level, and the needle pointing to the mark in order to get the rough alignment out of the way, thereby saving me massive amounts of time, and also allowing me to get a little bit more time in exposures. As it is, I am lucky to get around 30-45 second exposures with my camera piggybacked with a 135mm lens. I don't even dare attempt to use my scope directly, as I am sure I would be limited to exposures of only a few seconds. Does this sound feasible? I CANNOT place a concrete pad in the middle of a cow field, so unfortunately, that is not an option.

Hi Elizabeth,

When setting up before dark it's nice to have a distance land object to use as reference for north. For instance, a tree or telephone pole that is lined up with Polaris. As long as you set up in the exact same spot each time that object will give you reference to get close enough to tweak your final alignment once it gets dark enough to see Polaris. You can use a compass but keep in mind that Polaris is not aligned with magnetic north, it's actually slightly to the east of magnetic north so you'll need to "guesstimate" a slight shift to the right of where magnetic north is indicated on the compass. This can be pretty accurate once you've done it enough and know how much that slight adjustment is. Also, stand a good distance back from your mount/pod when using the compass, the metal from the rig will effect the compass reading if you are real close.

When setting up your mount on soil it's a good idea to use something solid under each leg of your tripod. 3 to 5 pound steel weights(flat old-style type for dumbbells with hole in center) work great for this if your tripod leg can sit on top or in the center hole without going through and touching the ground. I used an adhesive and glued a dense foam padding(cut in circle inside rim of weight)) to the top help with vibration dampening. Even seemingly solid ground will give way over the imaging session and cause your mount/scope rig to settle or lean which of course will have negative impact on your alignment. A friend of mine brings along 12 inch concrete patio blocks to set under his tripod legs. I like the weights because they take up less space in transport.

Hope this helps.

My SCT mount came with a compass which I found to be a total waste of time as the steel tripod legs deflected it by about 20 degrees. It would pay to check yours.
One of things I do to get me in the ballpark (since there's no Polaris here) is to find true north/south by putting a vertical pole in the ground and noting where the shadow is at solar noon (which you can get from the newspaper or an ephemeris). At home I have marks painted on the ground. When I was overseas, I found a patch of dead grass and took a photo from that point with the shadow and distinct local features (trees). That night I put the telescope in the same place and aimed for the appropriate tree from the image in the camera.
You could do something similar using a distinct fence post for example. Use the shadow technique to find north from your post during the day and put a temporary pole directly north of it. Use that to sight down towards something some distance away (a house, light pole, etc). Get two red lights and put one on your fence post and one on the thing you've identified. Now when you go out at night, anytime that you can see the two lights directly above/below each other, you are on a north/south line.

Hi guys. Your ideas sound great, and I believe they may work out quite well. Only thing is that I have to adjust where I set up due to what field the cows are in, and getting the exact same spot is iffy at best, because the fields are typically 70-100 acres apiece. Most of our fence posts are obscured by woods along the edge, so I may have to find new favorite spots. I have to be very careful about leaving anything in the fields because of the cattle, and they are our money makers, so they come first over the hobby. A temporary pole in the gound may work out quite well, though. The idea about the weights is a great one, and we have several of those weights hanging out at the house. The legs of the mount are think enough that they shouldn't pass through. Thanks for some great ideas, guys! I can't wait to try them out!

If you have a GPS and compass, you can use the following website to get the exact variance from magnetic north to your location:

http://www.ngdc.noaa.g​ov …ls/struts/calcD​eclination

If you don't have a GPS, but know ahead of time where you will be, there are other web sites that can give you the LAT and LONG of that place, using Google Earth or something similar. Then when you set up, take the variance that you found ahead of time from the web site above, into account when you set the scope to true north. You'll know the latitude from the GPS coordinates, which should be pretty easy.

Steve

Great information. Can't wait to try it out!