Polar alignment
- Piet Le Roux
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Polar alignment
- OzEclipse
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Re: Polar alignment
My method relies on using a bright green laser. This may not be appreciated at a star party although it the procedure only takes 4-5 mins and can be performed during late twilight before
The laser is attached to a fixed part of the mount not too far from the polar axis to minimise parallax. I attach mine to the top of the south leg.
To find the pole stars in the small binoculars, I usually start at the
Once the laser is pointed, to just have to point the polar finder to the laser. I usually lower the polar axis elevation down below the pole, sweep the mount across until I see the beam in the finder then elevate the axis to the point of the beam.
The only problem for you is that you need to fit a polar finder. Once fitted, spend one night doing an accurate drift alignment and once aligned, set and lock the polar finder in position. If the finder is to be removable, you need to have a positive exact locating connection like a three pin registration plate.
Over 40 years in astronomy, I have used many methods of polar alignment, drift aligning, magnetic correction applied to compass and clinometer. This is by far the quickest and easiest. If the engineering & machining required to fit a polar finder is beyond your skills, you may wish to look at the polar master or sharp star computer assisted. But this method is quicker and at least as accurate.
Cheers
joe
Amateur astronomer since 1978...................Web site : http://joe-cali.com/
Scopes: ATM 18" Dob, Vixen VC200L, ATM 6"f7, Stellarvue 102ED, Saxon ED80, WO M70 ED, Orion 102 Maksutov, ST80.
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- Piet Le Roux
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Re: Polar alignment
here is a photo of my wedge/tripod south facing side. My leg is facing North but I don't see a problem mounting a adjustable laser mount on the tripod. But a polar scope is not a option. What if I set the laser on the polar South, the scope in its home position and then use my East/West fine adjuster and my wedge angle adjustment to fine tune it while I look through the telescope with a illuminated Astrometric eyepiece? I have a right angle spotting scope that I can mount on the scope would that not work?
- Star Dad
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Re: Polar alignment
I use "water-proof" duct tape to mark where my tripod legs go on my asphalt driveway. I've begun to notice that the legs (which have a nub on the bottom) are beginning to make an indentation in the asphalt - so my accuracy in placing the mount on the tape is really good, I guess. I have to replace the tape ~ every 4 months or so, but it is red and glossy and shows up well using a red flashlight. Also the tape leaves a white residue when it is worn out which makes placing replacement tape easy to do.
Hope this helps!
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- Piet Le Roux
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Re: Polar alignment
- SkyHiker
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Re: Polar alignment
The idea is to first find the scope's
If you try this you will probably find that the hardest part is to get the center of the circular tracks of the
- Gulf Coast Guy
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Re: Polar alignment
https://www.sharpcap.co.uk/sharpcap/fea ... -alignment
Works North or South. You just need to get within ~5° of either pole and follow the on-screen instructions.
GCG
Mount/tripod's: Meade LXD-75 EQ; Orion Starseeker IV ALT/AZ; Celestron Heavy Duty ALT/AZ Farpoint UBM (Universal Binocular Mount)
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- Piet Le Roux
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Re: Polar alignment
hope the weather clears so I can start testing!
- Piet Le Roux
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Re: Polar alignment
- OzEclipse
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Re: Polar alignment
Hi Piet,Piet Le Roux wrote: ↑Mon Dec 02, 2019 10:04 pm I had a look at my old equatorial mount and the polar scope is mounted at your latitude angle and when it faces the celestial pole your mount is aligned. The polar scope is independent of any Ra and Dec movement. I have mounted my laser in the same way. So if my laser is aligned with my mount and is pointing exactly at the celestial pole, and my OTA is also pointing to the celestial pole, I can begin my two star alignment and I should be good to go? So Joe my conclusion is if you replace your polar scope with a laser you don't need a polar scope ?
I am glad you seem to have solved your problem. The method you are using is different to mine but yes, if the laser moves in ALT AZ with the polar axis and is precisely aligned then no you don't need a polar scope.
In my method, it is essential that the laser be attached to a stationary part of the mount. The laser is trained on the pole and then the mount pointed at the bright laser spot on the sky. I did it this way because I already have a precisely aligned polar scope but because of the mount weight, it's difficult to scan the loaded mount around and work out where I am pointing. The laser gives me a beam and an end point that are easy to fine with the mount
It's great that your scope has polar home position. This is effectively a polar scope so you don't need a separate one as I suggested. My technique does not work if the laser moves as you adjust the polar axis direction.
By attaching the laser to the wedge, the artificial pole star moves with the mount. Does it only move in azimuth or in elevation as well? I cannot tell from your picture.
If the laser moves in ALT and AZ with the polar axis then this is a defacto polar scope.
1 set the scope to polar home position
2 adjust the laser to the centre of the field of the scope
3 use handheld binoculars in one hand or the telescope finder to find the pole stars.
4 Point the laser at the 7th mag pole star and fine tune through the main scope
This method relies on the scope being able to reproducibly and accurately point at the mounts polar axis position. You can check this by pointing the scope polar axis at a distant object(even a close one would be ok since there is zero parallax), put the mount into polar home and slew the
Joe
Amateur astronomer since 1978...................Web site : http://joe-cali.com/
Scopes: ATM 18" Dob, Vixen VC200L, ATM 6"f7, Stellarvue 102ED, Saxon ED80, WO M70 ED, Orion 102 Maksutov, ST80.
Mounts: Takahashi EM-200, iOptron iEQ45, Push dobsonian with Nexus DSC, three homemade EQ's.
Eyepieces: TV Naglers 31, 17, 12, 7; Denkmeier D21 & D14; Pentax XW10, XW5, Unitron 40mm Kellner, Meade Or 25,12
Cameras : Pentax K1, K5, K01, K10D / VIDEO CAMS : TacosBD, Lihmsec.
Cam/guider/controllers: Lacerta MGEN 3, SW Synguider, Simulation Curriculum SkyFi 3+Sky safari
Memberships Astronomical Association of Queensland; RASNZ Occultations Section; Single Exposure Milky Way Facebook Group (Moderator) (12k members), The Sky Searchers (moderator)
- Piet Le Roux
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Re: Polar alignment
- SkyHiker
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Re: Polar alignment
This is why I advocate methods that use an
- Piet Le Roux
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Re: Polar alignment
I don't understand the point you trying to make: The fork mount is a polar mount and works like any other. The fork's rotation is yourSkyHiker wrote: ↑Tue Dec 03, 2019 10:56 am With all respect, I doubt if this will work Joe. Your step 2 is difficult to implement and depends on uncertain assumptions. First, can we assume that the mechanical fork axis is exactly perpendicular to its base? Secondly, if that is the case, can we assume that the optical axis is aligned with the fork's mechanical axis? Third, can you align the laser exactly to the center of the scope's FOV? Each of these three requirements must be accurate to about 1'. I think everything combined with your method this can easily be off by a full degree, and it is a lot of unnecessary alignment work.
This is why I advocate methods that use an RA slew to determine where the RA axis is pointing relative to the Az axis, then adjust the Az axis using the AltAz controls so this point coincides with the SCP. By doing that, none of your assumptions are needed and any inaccuracies resulting from implementing these assumptions, are avoided. By locating the center of RA rotation on a digital camera then moving that point to the SCP with the AltAz controls, you can achieve 1' accuracy directly. The Polemaster, Sharpcap and the computer-less method that I proposed will all do that. The use of a camera makes all of the intermediate alignment steps that you require, obsolete, and makes it possible to do PA to within 1' quickly.
- Piet Le Roux
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Re: Polar alignment
I don't understand the point you trying to make: The fork mount is a polar mount and works like any other. The fork's rotation is yourSkyHiker wrote: ↑Tue Dec 03, 2019 10:56 am With all respect, I doubt if this will work Joe. Your step 2 is difficult to implement and depends on uncertain assumptions. First, can we assume that the mechanical fork axis is exactly perpendicular to its base? Secondly, if that is the case, can we assume that the optical axis is aligned with the fork's mechanical axis? Third, can you align the laser exactly to the center of the scope's FOV? Each of these three requirements must be accurate to about 1'. I think everything combined with your method this can easily be off by a full degree, and it is a lot of unnecessary alignment work.
This is why I advocate methods that use an RA slew to determine where the RA axis is pointing relative to the Az axis, then adjust the Az axis using the AltAz controls so this point coincides with the SCP. By doing that, none of your assumptions are needed and any inaccuracies resulting from implementing these assumptions, are avoided. By locating the center of RA rotation on a digital camera then moving that point to the SCP with the AltAz controls, you can achieve 1' accuracy directly. The Polemaster, Sharpcap and the computer-less method that I proposed will all do that. The use of a camera makes all of the intermediate alignment steps that you require, obsolete, and makes it possible to do PA to within 1' quickly.
here is a conventional polar mount compared to a fork mount in polar configuration...
- SkyHiker
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Re: Polar alignment
Yes I understand exactly what you are doing and what Oz is doing. I just want to point out that IMHO you will never get about 1' or 2' accuracy, which is what is needed for good astrophotography. I suspect that yours will be 10' or more. This results in
This is why I pointed out that there are better methods using a camera that will give you better alignment. Many have failed making
- JayTee
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Re: Polar alignment
As another alternative, I recently adapted my ZWO planetary webcam to fit my Canon lenses. If you get a "V" or "D" bar for the top of your
JT
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- Piet Le Roux
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Re: Polar alignment
step one: I want to find a practical way to do polar alignment(in the southern hemisphere) that does not need a lot of gear and is a pain to do.
Step Two: I want to learn to test my polar alignment with the drift method for the southern hemisphere.
Step three: I want to learn to do
Once I am competent doing the above I will attach a camera.
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