Fearing the pier placement
Posted 24 February 2013 - 03:46 AM
Posted 24 February 2013 - 07:39 AM
I don't know whether I'm teaching my grandmother to suck eggs and I'm making a few assuptions, but having selected your optimum position, irrespective of not being able to see Polaris, I would definitely "pitch camp" at that point and cross any potential, (but never innsuperable), mount alignment problems once the pier is in place.
Personally, I did have the advantage of being able to access Polaris when I laid the base for my observatory, but went about it, in daylight as follows.
With the site optimised, (primarily decided by walking about the yard at night to establish the maximum amount of sky accessible to me), I laid a circular concrete base to a depth of 6" wide enough to accomodate my 7' diameter "dome", but marked out and left a separate 2' square 2' deep hole in its centre to accept a cast iron pier.
This was shuttered from the rest of the base, in order to eliminate any vibration whatsoever, and then also filled with concrete. When dry, I then set about establishing a North/South meridian line.
To this end, I marked the centre of this central square block of concrete by drawing two diagonal lines across it and then I simply used a long upright pole to cast a shadow of the Sun at noon to create a shadow which bisected the central pont of the pier block. The shadow line was then made (semi) permanent by tracing it onto the ground with a chalk stick. I was now in a position to attach my pier to its block.
With the pier now bolted down, in position and levelled, it was a relatively easy matter to align the mount; (a Skywatcher HEQ5 Pro) but as said, for me it was easily accomplished since I was able to access Polaris.
In your case, your latitude, (elevation), angle is relatively easy to achieve; adjustment in azimuth less so.
To achieve the correct angle of latitude, and assuming your 'scope is at present EQ mounted on a tripod, take the tripod to a place in your backyard from where you CAN see Polaris.
Level it as accurately as you are able, and then set the mount upon it. Now manoever the tripod legs and adjust latitude scale until you CAN see Polaris via your polar 'scope or, if you haven't a polar 'scope, through the hole in the mount's RA axis. Don't forget though, to continually monitor the mount's levelness.
Once you are satisfied that you have Polaris where you want it, the mount can be removed from the tripod and transferred to your pier with reasonable confidence that its set to your latitude and pointing essentially North as pre-determined by your North/South meridian line.
As to adjustment in azimuth, the above position of the mount should be accurate enough as it stands for visual astronomy. For imaging however, it would most likely have to be refined by means of drift alignment.
Hoping this helps,
Posted 24 February 2013 - 07:50 AM
A shot of the preparations prior to placing my pier in position.
The diagonals establish the mid-point of the block while the extended line from its centre, represents my N/S meridian.
Posted 24 February 2013 - 08:48 AM
It took me a long time to realize this.
Posted 24 February 2013 - 10:01 AM
My first approach to this would be "try before you buy". Putting in a pier is pretty permanent. Try various locations on a tripod first and see what works best for you.
As for optimizing the location, As Jim says, is it possible to lose a tree or two? Also, building the observatory up off the ground can gain you some precious degrees of lower altitude viewing. Depending on the kind of observatory, you might be able to build a wooden deck to place it on, or use other means to get it higher.
Keep in mind that trees grow. (and your pier doesn't! ) You might want to look into exactly what kind of trees are around you, how fast they grow, and what their expected maximum height is. That might help you decide which trees you want to avoid the most.
Not having a view of polaris is inconvenient, but not a deal killer. Some mounts offer a polar alignment routine that does not need polaris. Some can be used with eqmod.exe which provides that capability. Or you can use something like AlignMaster which is designed to replace a drift align technique, but can be used to fine tune a rough polar alignment that was started by just aiming north and raising the RA axis to your latitude angle.
Posted 24 February 2013 - 10:10 AM
Now, you say, how do you polar align the Mount without Polaris in the alignment scope? There are several ways to do this. I won't go into them here, but there are ways to align a scope without Polaris. And without a polar alignment scope.
But, how do you decide how to align the pier without seeing Polaris? The pier itself does not have a scope on it to use one of the alternative polar alignment methods.....Again---several options.
Obviously a compass, correctly calibrated, and with the correction for magnetic declination for your location, should get you within a degree. And your mount itself will have several degrees of correction in it should you need it.
An alternative method? Set your scope up on its portable tripod, and get it polar aligned using the drift method, or one of the computer assisted methods. Then just look where the polar axis is. That is what you are after. Line your pier up to accommmodate what you find on your portable tripod mounted scope.
Posted 24 February 2013 - 01:42 PM
One thing to consider, raising the height of your observing position even a little bit (couple of feet) can make a big difference in horizon access. Going 2-3' in the air isn't difficult if you're putting together a permanent (or semi permanent) observatory.
Because you're using Celestron scopes/mounts you won't need to be able to view Polaris to get a good polar alignment. The software in your hand controllers will give you that capability so don't worry about it. You will need to approximate the position of Polaris during the construction of any pier you might use, and this can be done in the daylight using the sun at it's highest point or with a compass as Alex mentioned.
Posted 24 February 2013 - 03:23 PM
Most of the trees are large however thinning out might help a good bit.
When I look at the sky with no formal knowledge I am looking for the largest overhead degrees in the path of the ecliptic for observing and taking into consideration for the seasonal shift of that path. Am I looking at this correctly?
I have been setting up the big C11 on the tripod in a few spots, but the past couple of months have been pretty cloudy or clouds break for just a few hours (not time to setup the c11 but able to get out the 80mm ref).
Here are a few choices that I am thinking of, mostly the one off the front deck due to 25 feet away I have a warm room of the house. This image is N up
Posted 24 February 2013 - 03:30 PM
Also worth keeping in mind is whether the sacrifice of one or two trees might make a major improvement.
It took me a long time to realize this.
Hey Jim, I visit my sister and her fam regularly in Lovettsville, very nice area. There are two big trees in the front but in the summer they really help keep the house cool. I have removed any Pines that were in the way. I am not a fan of Pine trees, more so when they are near the house.
Posted 24 February 2013 - 04:50 PM
My opinion is you want as much view of the South as possible. Your red location is one of the better places on the property for that view South. You could do even better if you took out those two trees in the front yard and moved the observatory further North.I love trees, but trees by structures are problematic anyway.
Posted 25 February 2013 - 06:33 PM
The property slopes to the south so the lower garage is below the horizon at the red marker. The two trees are about 40+ feet high and currently hold the hammock in the summer But you are correct, It would really open the sky up.
It will be tough to get rid of them because of the great shade to the house that they provide.
In the build I am going to plan on having the ability to add a second pier in the OBS.
I am working with a budget of around $2,000 just for the concrete and building materials, I know it is a small budget but it just happens to be my pay grade.
Posted 25 February 2013 - 08:09 PM
There is no need to see Polaris for a permanent observatory......
Agree on this - we in Australia cope without a pole star anyway - I would mark true north when you can, just align on that when building, and then drift align to fine tune....
Posted 04 March 2013 - 09:11 PM
I have had the scope setup for the past 4 days in the location I am thinking. Here is a link with where I am heading.
Most of the light pollution is low on the southern horizon (The Mall of Georgia 10 miles south!) but local is nice and dark for now.
Posted 05 March 2013 - 01:16 AM
Posted 05 March 2013 - 12:44 PM
Yes, 6 feet off the corner of the existing deck. Not where the scope is pictured, I added a picture that shows a red circle on the ground where I think the pier should go.
I'd move it farther away from the deck and chop down those two tall trees just to the West. But that's just me.
So far the trees stay, I have been camped out for a few days and the trees don't seem to be a major issue.
Thanks for the input.
Posted 05 March 2013 - 11:42 PM
Posted 06 March 2013 - 01:10 AM
I will do that, I will get up on a ladder and get a real visual the next nice night. Tonight it rained and had 25 mile an hour winds. I was a little nervous because the scope was under that 365 cover, but it's over and the cover really worked great.
Consider going taller. I am in a somewhat similar situation but have an existing 2 story workshop on the property which is where I will be placing my observatory. I don't live there unfortunately it's my parents second home. 20 acres must be incredible. There house is 3 acres and I am completely blown away by that. Property is probably bigger then my block.
Yes, I'm very fortunate where I am at, to the east of me is 100 acres of green space that was donated as a daytime use park.
Posted 31 March 2013 - 10:54 PM
Good tutorial: http://stargazerslou...ium-landscapes/
Here are the files I created.
360 Deg Image
New CGEM DX mount arrives tomorrow, still have not completed the pier mount portion yet. I am thinking I will use Dan's pier plates 12" mount bolt pattern and try and fabricate my own mount and if I fail I can order the CGEM mount plates from Dan.
Posted 10 April 2013 - 12:36 PM