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#51 Clif

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Posted 22 July 2006 - 10:32 AM

Similar approach: I discovered that the plotting accuracy of today's ink jet printers is quite impressive (on a Mac at least, don't know how well it works on a windows system) and the drafting ability of many drawing programs (MacDraw, ClarisDraw, Canvas, probably the CAD packages too) is just as good. Combining these, I have found that one can make setting circles which are very servicable by just drawing them on the computer, printing them out on the ink jet printer and laminating them to plywood circles using liquid epoxy. They are at least as accurate as 0.1 degrees which is about as good as you can read a circle anyway. I have even made verniers for the circles this way. If anyone wants details, I can expand on the technique. Attached is a picture of a 24" RA circle I made this way. The small divisions are one minute of RA in size. The circle is for a big reverse fork mount I am working on.

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  • 1055323-24in drive pulley.jpg


#52 Astraforce Paul

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Posted 28 July 2006 - 10:20 AM

Clif, yes, please describe more about what you did. Do any of those programs automatically put the circle number in? I presume so. Is there a freebie program or demo program for the Mac that one could test this with? Anyone besides Cliff who knows please chime in, too!

I'm interested in rolling my own template (I like your BIG numbers--easier to read) with my own degree markings (e.g., longer 5 degree line, no outer checkerboard, etc.).

How did you handle the overlapping? I've found that my inkjet does NOT print to the border so that there is a white, unprinted border. It's a bit tricky overlapping the sheets.

#53 Clif

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Posted 03 September 2006 - 09:22 AM

No, everything is put in by hand, but it was not very difficult. The tic marks are really lines going all the way across that were put into final position by copying, rotating, grouping, copying, rotating, etc. The numbers had to be rotated also and individually placed. Masking white opaque circles with black borders were plotted on top of the maze of crossed lines to leave the tic marks sprouting from the edge of the circle. I used MacDraw Pro which is just the grown up version of MacDraw that used to be given away free with all Macs. ClarisDraw, Kalaidadraw and Canvas would probably have enough tools to let you do it, PC or Mac.

#54 chmee

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Posted 04 September 2006 - 01:33 PM

How about using the smarttool w/ well-designed mount (a la Rod's) for altitude ($80 at sears), and a digital compass for azimuth (see also at sears, for example, $20), total price $100 plus tax.

I don't know how accurate the compass is. It only reads out to the nearest degree. However, Rod points out that by calibrating the smarttool mount onsite, one can get the altitude spot-on every time. This reduces the searching to just azimuth, and a search on only one axis is trivial.

The other problem w/ the compass is the magnetic declination, as pointed out above. However, one can look this up ahead of time (it appears to be 10 degrees 45' west for my location near DC), and compensate onsite.

Does this sound reasonable to anyone? Anyone have experience w/ digital compasses and have an idea how precise they are?

Cheers,
pete

#55 Curt B

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Posted 05 September 2006 - 06:23 PM

I use Planetarium on my Palm to look for my objects. There is an option for magnetic azimuth on it, so it should solve the problem of knowing what true north is. My only concern is will the metal OTA interfere with the compass?

#56 chmee

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Posted 06 September 2006 - 08:52 AM

I use Planetarium on my Palm to look for my objects. There is an option for magnetic azimuth on it, so it should solve the problem of knowing what true north is. My only concern is will the metal OTA interfere with the compass?


Good question. I ordered the cheap wayfinder from amazon ($17) and will try it this weekend. I don't have a big tube, but do have four long aluminum poles (2" diameter), so it would probably be similar. However, it's supposed to work inside a car or truck, w/ an indicator when bothered by interference from metal, so we'll see.

pete

#57 Curt B

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Posted 06 September 2006 - 06:33 PM

Looking forward to hearing about your results chmee....please keep us posted!

#58 chmee

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Posted 07 September 2006 - 07:23 PM

Good question. I ordered the cheap wayfinder from amazon ($17) and will try it this weekend. I don't have a big tube, but do have four long aluminum poles (2" diameter), so it would probably be similar. However, it's supposed to work inside a car or truck, w/ an indicator when bothered by interference from metal, so we'll see.

pete


No go, it only registers in increments of 5 degrees, and even that might be overstating its accuracy. My sense is that this is representative of other cheap digital compasses as well.

Oh well, at least it works quite well for its intended purpose, i.e. in the car.

#59 Curt B

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Posted 08 September 2006 - 06:53 PM

Sorry to hear that....was looking forward to hearing about your results...

#60 YankeeJeff

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Posted 08 September 2006 - 08:17 PM

I picked up the wayfinder v7000 for 50 bucks from overstock.com it's supposed to be accurate to 1 degree and I can set to true or magnetic north. I'll let you folks know how it works out. I don't really need it but I think it may be a cool looking gizmo to add on that also gives me the weather and some other neat tricks.

#61 YankeeJeff

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Posted 11 September 2006 - 09:57 PM

Update: Received and installed the Wayfinder v7000. IMHO, it does an excellent job (accurate to 1 degree + true or magnetic North settings). With the $9 Home Depot inclinometer and the Wayfinder 7000 digital compass ($50 refurbished from Overstock.com) the total system is about $60. If the digital SmartTool price drops enough maybe I'll get that too. Not a bad overall price for the results. It also works and I find it a bit easier to use. The down side - it costs more and defeats the purpose of doing this on a budget.

In any case, I will keep the setting circles on the scope just in case I'm ever observing in a location w/ strong magnetic interference. I can't thank you folks enough for the threads on this subject - it makes life a whole lot easier AND saves money! :bow:

#62 Curt B

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Posted 12 September 2006 - 06:46 PM

Thanks for the update....i just might get one too!

#63 chmee

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Posted 12 September 2006 - 10:01 PM

Update: Received and installed the Wayfinder v7000. IMHO, it does an excellent job (accurate to 1 degree + true or magnetic North settings). With the $9 Home Depot inclinometer and the Wayfinder 7000 digital compass ($50 refurbished from Overstock.com) the total system is about $60.


Wow, this I really didn't expect. Did you really give the compass a workout? I realize that it reads out in 1 degree increments, but does it repeatedly give the same value for the same orientation (place it against a wall, read, spin it a bit and place it back against the wall, read again)?

What about the backlight, can you keep the display on and backlight off for more than a minute or so?

I've already ordered the smartttool ($90 at amazon w/ an automatic discount) w/ the intent of replicating Rod Nabholz's setup. If this really works, I'd order it in a minute.

#64 YankeeJeff

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Posted 13 September 2006 - 12:37 AM

When I started using the compass tonight it was a little off. I had to recalibrate (takes about 30 seconds). This entails pressing the menu button once, pressing enter, spinning the base of the scope one full revolution, then repressing menu. I took off the suction cups of the compass and drilled it into the base to make it nice and tight. I also tightened the adjustment screw on swivel/tilt so that it basically can't move out of it's horizontal position. This also allows me to press the buttons without fear of knocking the compass out of it's holder. Your supposed to keep the compass (made for your car) in the same place w/in your car, thus I want to keep it in the same position on my scope.

Which brings me to one of the questions above: Did I

place it against a wall, read, spin it a bit and place it back against the wall, read again

... the answer is no.

Again, I screwed the plastic compass holder into the base (the compass itself can be removed from the holder but I don't move it). On the contrary, I keep it nice and tight on the holder at a horizontal position with the base for most accuracy.

Before viewing I simply calibratrate, make sure magnetic declination is set, and then generally keep the bottom base in place as I slew the scope. I do occassionally move the entire telescope unit around the house from one window to another) and it doesn't seem to affect results. How it works outside I don't know yet. Maybe I'll test it this weekend if the weather permits. For now it seems to be working in my home. I'm finding things very quickly.

Generally the target objects (using starry night & skycharts software) are found within the FOV of my 32mm eyepiece. Once in a while they are slightly off and it takes a nudge on the AZ setting to get it in the FOV. Usually this happens because the AZ coordinate lies almost directly between two 1 degree increments (e.g. 87.467 degrees) - add that to the rounded off declination and you may be off about 1.5 degree total at times. All in all I can live with that. I'm happy with it thus far. I'll keep you posted and report any problems.

FYI - the backlight can stay on up to 3 minutes and when the backlight goes off, the unit stays on a bit longer before the auto shut off kicks in. The compass is plastic. I think this little unit is ideal for my situation because I don't have to fuss w/ Polaris or anything -which is good for me since I can't see it from my window.

#65 Gigatron

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Posted 13 September 2006 - 09:15 AM

Hey Jeff,

Got a couple of questions for ya.

1) do you think the v700 would work well in place of the v7000? The difference seems to be the thermometer and barometer. I don't think I really need those to see a star, as long as the compass is just as accurate.

2) how did you mount it to your scope? any pictures?

3) have a part number on that inclinometer?

Thanks,
Fred

#66 kestrel0222

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Posted 13 September 2006 - 09:46 AM

Jeff,

Are you able to set north to Polaris? How do you calibrate it to correspond with computer generated azimuth coordinates? It all sound good.

#67 YankeeJeff

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Posted 13 September 2006 - 06:52 PM

Fred
1)The v700 gives the read-out in 5 degree increments. IMHO, this is not enough. I believe the v7000 unit has both critical components, namely the ability to correct for magnetic declination, as well as, giving read-outs in one (1) degree increments. There could be other units out there that have those same capabilites without the other bells and whistles for cheaper - I'm not sure.

2)I don't have the ability to post pictures right now.

Basically I screwed the compass into the swivel base board (toward the rear-end of the scope and directly opposite the front of the scope with the handle). If you can imagine placing the degree circle on the base board with zero (0) in the front - the compass would be screwed into EXACTLY where the 180 degree mark would be in the back. The compass should be screwed in tightly to the base. According to the instructions you can tilt the unit up or down within it's swivel bracket a maximum of 20 degrees but I found that not having a tilt at all is most accurate. Whatever angle you select for the tilt, the compass must stay that way (otherwise you'll have to recalibrate), thus I also tightened the side adjustment screw for the angle of the tilt so it doesn't accidently get bumped out of it's bracket.

3)The inclinometer was purchased at Home Depot (you won't find it on their website). It is an "EMPIRE magnetic polycast protractor" that can be purchased for a little less than $9.

Tom
I do not need to set North to Polaris - North is set magnetically by the compass and adjusted for magnetic declination. Once I turn on the compass and calibrate it (by pressing a button and spinning it in place one full revolution), I'm set to slew the scope to the coordinates I get from my planetarium software.

#68 Gigatron

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Posted 14 September 2006 - 09:05 AM

Thanks for the answers, Jeff. Just one more quick question, is there a particular reason that you mounted the compass where you did, or can it be put anywhere?

I mean, I have no problem mounting it at the rear, I'm just wondering if there's a reason.

Thanks,
Fred

#69 YankeeJeff

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Posted 14 September 2006 - 07:19 PM

I could be wrong, but I thought it would give me the most accurate reading -esp. when I'm trying to get down to 1 degree. Its placement mimics the finderscope placement - kind of like splitting the primary and seconday. When you step behind to read the display, its like you would in your car, i.e. looking at the compass display which gives the reading of the direction directly in front of you as you drive.

I guess it may be more convenient to place it to the left of the scope so I can just look down and take a quick read before peeking into the eyepiece but intuitively I'm thinking that wouldn't work. I guess you could try that out and test with a sky object. If it were not accurate, you might then readjust the declination to compensate. I'm not sure.

#70 Gigatron

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Posted 15 September 2006 - 08:43 AM

Well, here's my thinking on this; as long as the compass is facing forward (i.e. same direction scope is pointing), the readings should be just as accurate. 87* is 87* either under, above or along side the scope.

The only time I can see there being a problem, regardless of where the compass is placed, is when the object is at zenith.

When I get one, I'll mount it temporarily and see what happens if it's mounted along side the scope.

-Fred

#71 chmee

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Posted 15 September 2006 - 07:33 PM

Jeff.

I think the only real question is whether the compass will give precise, repeatable directions. I'm definitely looking forward to hearing your experience. Around here (DC), at least, we're going to get the first decent night in weeks tomorrow. Hope you have it as well.

I was thinking about the backlight. This is probably not a problem, as the screen could be covered by a red film.

pete

#72 YankeeJeff

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Posted 30 September 2006 - 06:48 PM

Update2: Believe it or not, I haven't yet had the opportunity to test the digital compass outside (Floyd Bennett Field is where I would go). The opportunity to step outside has been elusive and to be honest - it's nice and comfy inside and I've been learning a lot from the comfort of my own home. :grin: So, thus far I've had about 4 or 5 nights of testing indoors.

When I turn on the compass at the beginning of my viewing session, sometimes it puts an object in the FOV or sometimes it's accurate to about 1 or 2 degrees and requires some nudging to find the object. Thus far it has always been in the ballpark (under 5 degrees).

However, if I do a lot of moving around, which I usually do because of obstructions in the home and the limitation of window angles, it may eventually throw off accuracy by 5 degrees. Unfortunately, I've seen it get as bad as 8 degrees. I end up resetting the compass about 3 times a full night (i.e. 9pm - 5am). I also have a lot of electronic equipment around so I think it may contribute to throwing the thing off. In any case, even when it's off, I know I'm basically looking on the azimuth plane only so nudging is usually over quick.

So... I'm able to live with this non-precise degree of accuracy because it's tough for me sometimes to see Polaris (i.e. girlfriend won't give up the bedroom for the night!), and thus calibrating with other stars takes even longer for me. I would ideally need to test outside. When I'm at my outdoor spot, I'm basically planted in one area and just turn the scope's tube - I'm pretty sure it will work better in that scenario.

Until then, I'm not convinced this is the rock solid digital solution most are looking for. Perhaps there are better digital solutions out there that won't break the bank. It does happen to have a time advantage on the azimuth for me right now. This makes me appreciate that very accurate Home Depot inclinometer that much more. Also, I finally got my Telrad so the combo of finder-scope, Telrad, and this budget 'push-to' system seems to work well enough for me. Again - my humble thanks to the folks who started this thread and have therefore saved me time and money. :bow: Oh, and my apologies for folks who ran out and purchased a Wayfinder 7000 and may not be thrilled about it :o :grin:

#73 chmee

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Posted 02 October 2006 - 09:14 PM

Oh, and my apologies for folks who ran out and purchased a Wayfinder 7000 and may not be thrilled about it :o :grin:


:( Too late!

I had the smart tool for altitude, so decided to try the compass for azimuth. I was hoping for 2 or 3 degrees max, figured it was only $40 if not. I did not quite expect 8 degrees.

At any rate, given both devices, I mounted them on my scope last night and took it out to the driveway. I had more confidence w/ the inclinometer (smart tool), as others have used it successfully. W/ the wayfinder I had several concerns: 1) accuracy, 2) backlight, and 3) directionality.

For accuracy, concerns were justified. I calibrated the wayfinder and then used the magnetic declination setting to zero on polaris. I then tried to use the two to find things, with mixed success. My first attempt, M31, was off by 3 degrees of azimuth. M76 was found in the eyepiece (40mm, about 1.5 degrees). M92 two degrees off. Several stars were within a couple degrees azimuth, but two were four degrees off, and one was eight.

Interestingly, when I finally rotated all the way around, polaris was only one degree off. I'm speculating that the "map" of the surroundings the wayfinder makes during calibration is off. Perhaps this was because I didn't do it evenly enough or some such.

Another interesting point that didn't occur to me until afterwards was that I think the error was always in the same direction (of azimuth). If so, this would significantly ease the process. After all, searching in one dimension is much easier than searching in two.

As far as the smart tool, it was always within two or three tenths, at most.

My second concern was the wayfinder's backlight. Turns out this is not bright, is easily disabled, and actually somewhat useful. The wayfinder has to be mounted down on the rocker base, so it's a bit hard to see from up near the eyepiece. Situation might be different when I get to a dark site.

My last concern was directionality, by which I mean that the wayfinder is designed to be mounted on a dashboard, facing forward. Facing the compass in the directy my mount is facing would mean mounting in on the "back", i.e., I'd have to get off the chair and walk around the scope to read it. I put the wayfinder on the side of the scope, meaning that it's 90 degrees off, PLUS the magnetic declination. The wayfinder's magnetic declination can be set up to 99 degrees, which would seem to be enough. However, it didn't seem that way, I seemed to need more like 105. So I left it at 95, meaning that I have to add 10 to each azimuth I look up on the computer. No big deal.

Overall, it's good enough that I'm willing to spend another couple of evenings trying to work out the kinks. If I can't, I'll mount the wayfinder in my car and add a printed azimuth circle to the base (which will be a bit of a pain).

Cheers,
pete

#74 YankeeJeff

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Posted 02 October 2006 - 09:47 PM

*Gosh, dang dibbity dag nabbit* - sorry Pete. That first night it was only off max 1.5 degrees. It was w/ the longer nights that I saw how bad it could get at times. Now that I think about it, I was limited to a smaller part of the sky. Maybe your right about the direction of error and it’s not the 'moving around' that causes the errors as I thought it might be. I've got to check that out some more myself. Hope you work out the kinks.

#75 chmee

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Posted 03 October 2006 - 01:42 PM

*Gosh, dang dibbity dag nabbit* - sorry Pete. That first night it was only off max 1.5 degrees.


Don't worry, I'm just messing w/ you. I'm a gadget freak and had to try it out. Might still work. Unfortunately, weather doesn't look promising here, plus the moon situation, so it might be a couple weeks.


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