Fireball
sage
Reged: 03/24/06
Posts: 265
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Quote:
Carol,
Imagine a piece of thin steel - the steel strapping used on lumber or pallets would work great. You simply attach, say, 6 inches of that to the edge of your groundboard with a couple of screws.
Then attach your pointer to a small magnet, and stick it to the center of the steel strip.
When you need to tweak your calibration you simply slide the pointer along this strip of steel strapping until it matches the computer's azimuth setting and you are good to go.
Let me know if that is clear as mud and I will try again. 
Rod
Sounds interesting and simple.
Is it possible to show a picture of this set-up ?
That would make everything very clear.
Thanks !
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20x90 Bino
12" Lightbridge
Selection of ultra wides from Meade, Televue and Pentax.
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csa/montana
Astro Ambassador
Reged: 05/14/05
Posts: 28286
Loc: montana
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Fireball: Go to top of this post, my first picture.
On the outer side edge of the lower circular base, the metal strip will be affixed there, completely around the base; then where the pointer is,(screwed in), I now will have the pointer glued to a small magnet that I can now move anywhere on the degree circle, to get set up.
Carol
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Carol
AstroTech 16" Dob (Thanks ASTRONOMICS!)
AstroTech 66ED / Vixen 80MF/AstroTech Voyager
Masuyama's 7.5, 15, 25W, 35mm,
Tak LE 5mm B/TMB 3.2
7mm Pentax XL, 10mm Pentax XW
14mm Meade 4000 UWA
22mm Pan, 35mm Pan
DreamCatcher Dobservatory, #2
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csa/montana
Astro Ambassador
Reged: 05/14/05
Posts: 28286
Loc: montana
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Ron: Just downloaded trial PC version, & am ordering PC & PDA version. This is a great program, just what I was looking for. Now, I'm going to try to find a good price on the Axim. Again, thanks for all your help, couldn't have done it without your kindness & expertise!
Carol
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Carol
AstroTech 16" Dob (Thanks ASTRONOMICS!)
AstroTech 66ED / Vixen 80MF/AstroTech Voyager
Masuyama's 7.5, 15, 25W, 35mm,
Tak LE 5mm B/TMB 3.2
7mm Pentax XL, 10mm Pentax XW
14mm Meade 4000 UWA
22mm Pan, 35mm Pan
DreamCatcher Dobservatory, #2
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Curt B
super member
Reged: 08/02/05
Posts: 171
Loc: Regina, Canada
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Here is the link for Pleiadatlas
http://astro.isi.edu/pleiadatlas/
and Planetarium
http://www.aho.ch/pilotplanets/
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Celestron 102SLT,red dot finder
WO ZenithStar 80II ED with WO 1 1/4" dielectric diagonal, and red dot finder
SkyWatcher 100mmED Pro, with WO 2" Dielectric diagonal, 9X50 RAC finder, with telrad
Baader Hyperion 21, 13, and 5mm eyepieces
GSO 30 & 26mm 2" eyepieces
WO 8 - 24mm Zoom eyepiece
Tele Vue Ethos 13mm eyepiece
Celestron Power Tank 17
Orion SkyView AZ mount
William Optics TR-188 Tripod
Edited by Curt B (05/03/06 06:53 PM)
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rnabholz
scholastic sledgehammer
Reged: 07/25/04
Posts: 764
Loc: Iowa
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Carol,
Of course the call is yours to make, but if it were me, I wouldn't bother to make the strip go all the way around.
6-12" of strapping would give you around 30 to 45 degrees of adjustment, plenty for even a casual initial polar alignment.
Just another two cents - making my total to date $3.08.............Sorry.
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Rod Nabholz
Home Built Astronomy Projects
Wild Bird Photography
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csa/montana
Astro Ambassador
Reged: 05/14/05
Posts: 28286
Loc: montana
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Rod: Again, thanks! Didn't realize this. It will save me a lot of work. Can tell I'm an amateur at this, huh? I've got the "0" degree mark on the left side, so a short strip running each way of this would be good?
Carol (p.s. you have a credit of many thousands of $, so I can pick your brain a lot, at 2cents a question, I'm gonna keep you verrrry busy!)
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Carol
AstroTech 16" Dob (Thanks ASTRONOMICS!)
AstroTech 66ED / Vixen 80MF/AstroTech Voyager
Masuyama's 7.5, 15, 25W, 35mm,
Tak LE 5mm B/TMB 3.2
7mm Pentax XL, 10mm Pentax XW
14mm Meade 4000 UWA
22mm Pan, 35mm Pan
DreamCatcher Dobservatory, #2
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rnabholz
scholastic sledgehammer
Reged: 07/25/04
Posts: 764
Loc: Iowa
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Exactly, just a few inches on both sides of zero will do the trick.
Glad to help.
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Rod Nabholz
Home Built Astronomy Projects
Wild Bird Photography
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AtLarge
super member
Reged: 08/22/05
Posts: 149
Loc: 868 Ft. Above Sea Level
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Quote:
Exactly, just a few inches on both sides of zero will do the trick.
Glad to help.
This is very informative but let me make sure I have this straight.
The pointer is on the bottom base.
The pointer is aligned with Polaris and the base leveled.
The steel band with magnet on pointer allow for adjustments so you can tweak that alignment by moving the pointer after you test on some known objects. (without having to keep moving the entire bottom base)
If the markings are on the top board and are stationary with the OTA where do you set the gradients to begin with? The zero / zero goes directly below the center of the OTA at the front of the scope? That way you always begin with the scope pointed at the Polar North.
You then match the Azm:159 and Alt:+38 as per your favorite program (my settings at the moment for Jupiter) and your on target or at least in the neighborhood.
Am I keeping up here or did I miss something? 
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Meade Lightbridge 12'' Deluxe with Orion COL.
Meade Series 4000 Plossl 7 Eyepieces & 5 Filters
Meade 114NT/500 Dwarf Dobsonian
Meade DS-114ATE
Meade 60AZ-T
Meade 227
Burgess BV125
Konus 2110 20x80mm Giant Astronomy Binoculars
Carson 20-100x70mm
Bushnell 16x50mm
 Oh, no. Not again!
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rnabholz
scholastic sledgehammer
Reged: 07/25/04
Posts: 764
Loc: Iowa
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You have it.
In Carol's pictures you can see that she set zero at 90 degrees from the tube, but it really doesn't matter that the scale match the actual azimuth direction, only that the scale and pointer indicate properly. Her approach makes it convenient to see when at the eyepiece when the scope is pointed north.
Using the approach where the scale is attached to the rocker means that you will have to leave the eyepiece position at times to line up the pointer. The approach I used is to put the scale on the groundboard and build some adjustability into the scale rather than the pointer. That allows the pointer, attached to the rocker, to be visible from the eyepiece at all times, a little handier set up, but a little more complicated build.
Let me know if you have other questions.
Clear Skies
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Rod Nabholz
Home Built Astronomy Projects
Wild Bird Photography
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csa/montana
Astro Ambassador
Reged: 05/14/05
Posts: 28286
Loc: montana
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See my new post here "my $12 Go-To" test drive
Carol
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Carol
AstroTech 16" Dob (Thanks ASTRONOMICS!)
AstroTech 66ED / Vixen 80MF/AstroTech Voyager
Masuyama's 7.5, 15, 25W, 35mm,
Tak LE 5mm B/TMB 3.2
7mm Pentax XL, 10mm Pentax XW
14mm Meade 4000 UWA
22mm Pan, 35mm Pan
DreamCatcher Dobservatory, #2
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SkyArcher
Carpal Tunnel
Reged: 04/12/06
Posts: 2010
Loc: 9545' in Colorado
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In case any wants it, I've attached the pdf of the file I used to make the degree circle. You can take the pdf to your local "Kinkos" copy center and have them print it out on 24x36 paper. Also while you're there, have them laminate the degree circles.
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An 8" Deep Space Hunter
4.5 w/ GOTO
4.5 newt w/ home built Dob mount
Omphaloskepsis - I didn't realize that there is a word for what I do while waiting for web pages to download 
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Relativist
Carpal Tunnel
Reged: 10/11/03
Posts: 2982
Loc: OC, CA, USA
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Just out of curiosity, how good is that home depot inclinometer? Could we maybe make our own that was a bit better?
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.......Curtis
20mm T2 Nagler, 10mm SW 82degrees, 5-8 SW Zoom:
All of the above replaced with WO Binoviewers!!!
Siebert OCA 1.25x-3.5x
10" OPT Starhunter (flocked & upgraded focuser)
10x50 & 15x70 Celestron Bino's
2" 2x GSO Barlow
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csa/montana
Astro Ambassador
Reged: 05/14/05
Posts: 28286
Loc: montana
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It's about 4-3/4" high (circular), with magnetic base. As Rod Nabholtz said, using the inclinometer, it's independent of the base, so no leveling is required.The scale is quite small & a little difficult to read at night, but works. During my viewing session, My Altitude degree scale matched the inclinometer with each change. The ideal one is what Rod has now; MD SmartTool digital level. It runs $100 though. I'm quite happy with my setup & accuracy.
Carol
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Carol
AstroTech 16" Dob (Thanks ASTRONOMICS!)
AstroTech 66ED / Vixen 80MF/AstroTech Voyager
Masuyama's 7.5, 15, 25W, 35mm,
Tak LE 5mm B/TMB 3.2
7mm Pentax XL, 10mm Pentax XW
14mm Meade 4000 UWA
22mm Pan, 35mm Pan
DreamCatcher Dobservatory, #2
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Relativist
Carpal Tunnel
Reged: 10/11/03
Posts: 2982
Loc: OC, CA, USA
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Ok, so let me ask this, could you use the inclinometer to "calibrate" the Altitude scale, bypassing the need to level the base? The idea would be to move the arrow as is done with the Azimuth scale.
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.......Curtis
20mm T2 Nagler, 10mm SW 82degrees, 5-8 SW Zoom:
All of the above replaced with WO Binoviewers!!!
Siebert OCA 1.25x-3.5x
10" OPT Starhunter (flocked & upgraded focuser)
10x50 & 15x70 Celestron Bino's
2" 2x GSO Barlow
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R_Angkasa
scholastic sledgehammer
Reged: 02/16/06
Posts: 899
Loc: SO PAS - CA
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Boy this is such a good thread . . . thank you for all . . . especially Carol who initiate this thread. Also to Rob and SkyArcher who make the Alt/Az degree circle work.
I also plan to do the same since it is doable.
My question will be when you have a tracking platform how do you calibrate the level. When you just start tracking you will have the platform swing to the east side and then it will end as it swing all the way to the west for 60 - 80 minutes.
I guess one solution will be searching for the object while the rocker base is level and after the object is in the FOV - turn on the tracking device.
Ridwan
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10x42L IS
FS128
12" DSH
3.5, 5, 7,
10, 14, 20,
30, 40
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rnabholz
scholastic sledgehammer
Reged: 07/25/04
Posts: 764
Loc: Iowa
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Curtis,
Using a scale without a level base is problematic because while you can always set the scale to match an inclinometer determined setting, when you turn the rocker on the base, the scale reading will be off immediately and will not be exactly accurate until you return it to the same azimuth you set it at.
Now, depending in the degree of deviation from level, this error could be small, but it could also be very large and make finding things in a one degree or so field of view very difficult.
The inclinometer takes away the possibility of this error, and so makes it the choice for me. The analog inclinometer mentioned in this thread is about $10, a cheap efficient solution.
Of course leveling the scope is another option, and actually, I do both to make things as accurate as possible.
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Rod Nabholz
Home Built Astronomy Projects
Wild Bird Photography
Edited by rnabholz (05/09/06 10:39 AM)
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rnabholz
scholastic sledgehammer
Reged: 07/25/04
Posts: 764
Loc: Iowa
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Ridwan,
I have given the tracking platform issue some thought, as I am conisidering building one for my scope.
I think the only approach that will work is stopping and returning the platform to level during the object acquisition process and then turning the motors on.
You would sacrifice 50% of your tracking period, but depending on the platform you would likely have 20 to 30 minutes of travel left. That would generally be enough for my purposes.
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Rod Nabholz
Home Built Astronomy Projects
Wild Bird Photography
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R_Angkasa
scholastic sledgehammer
Reged: 02/16/06
Posts: 899
Loc: SO PAS - CA
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Rod,
That is what I thought . . . having the dob level - align to the object (Alt/Az) - then turn on the tracking. Thank you for that confirmation.
Or another idea would be . . . calculating the difference between a leveled platform and a maximum swing platform. Then we can use this different to a Alt/Az value from the pocket star.
What do you think about that one?
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10x42L IS
FS128
12" DSH
3.5, 5, 7,
10, 14, 20,
30, 40
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rnabholz
scholastic sledgehammer
Reged: 07/25/04
Posts: 764
Loc: Iowa
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Quote:
Or another idea would be . . . calculating the difference between a leveled platform and a maximum swing platform. Then we can use this different to a Alt/Az value from the pocket star.
What do you think about that one?
Well, here is what I have come up with as I have pondered using a platform.
Remember that if you adopt my strongly preferred approach for altitude - an inclinometer, not a scale, the tube reading is always read independent of the base. So even on a platform the altitude reading will be accurate.
It is the azimuth that is vexing. Visualizing the base and the azimuth scale and the different possible orientations of that scale to the tilt of the platform, it seems to me that you would have an infinitely variable factor to consider.
For example, consider the scope pointing precisely perpendicular to the axis of platform rotation or pointing precisely parallel to the axis of rotation. In these cases, your azimuth is likely to be pretty accurate.
Now consider the scope pointing in between those points. It seems to me that depending on the degree of the platform tilt, you would compromise the accuracy of the scale because you have in effect compressed the spacing of the degree marks by tilting the scale.
If my visualizations are correct (and PLEASE, anybody who sees this differently please let me know your thoughts) you would have a very difficult time quantifying the deviation and therefore could probably not easily adjust for it.
Edited by rnabholz (05/09/06 12:28 PM)
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SkyArcher
Carpal Tunnel
Reged: 04/12/06
Posts: 2010
Loc: 9545' in Colorado
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Rob, I'm just having a little brain fart here, but I'm thinking that if you're using a tracking platform, wouldn't it be better to use the other set of coordinates (RA-DEC) and set up a different set of degree circles. I confess that I don't know what Ra-Dec coordinates are other than they are used on EQ mounts.
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An 8" Deep Space Hunter
4.5 w/ GOTO
4.5 newt w/ home built Dob mount
Omphaloskepsis - I didn't realize that there is a word for what I do while waiting for web pages to download
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