First light for DIY mini-EQ mount

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First light for DIY mini-EQ mount

#1

Post by BABOafrica »


1 x 20s raw light frame
M31 4AUG22 1x20s F2-64 B-EQ rongo F.jpg
...

82 x 30s (processed with darks-bias-flats)

Rongo Deneb 4AUG22 82x30s F2-64 B-EQ rongo F.jpg


The images are nothing special. Just a wide-field of M31 (straight out of the camera with no processing) and a stack of shots of a section of the Milky Way near Deneb.

I did both of them two nights ago once the moon had set. I was in a Bortle 2 zone.The second image is heavily cropped (about 50 percent cropped) to get rid of the artifacts created by the lousy lens.


What's special is that I was using my "new" DIY mini EQ mount for tracking (see pix below).

Please note that I had to use an "inadequate" telephoto camera lens (a Minolta lens that I once dropped and did my best to fix after it literally broke in half). It's the only lens I have at this point.

I put together the new mount from a bunch of junk lying around the workshop plus a stepper-motor controlled by arduino.

I can adjust both the AZ and the ALT to get pretty good polar alignment.

I attach some pictures of the mount.

I had the lens set for 180mm. I used 180mm mainly because I just bought a vintage 1970s Nikon Nikkor 180mm f/2.8 lens. I'm still waiting for it to arrive from the US. I'll be using it on the EQ mount when I can't load up the EQ-G or the AVX on my trips. This will give me more portability.

...
BABO mini-EQ mount 06.jpg
...
BABO mini-EQ mount 04.jpg
...
BABO mini-EQ mount 03.jpg
...
BABO mini-EQ mount 01.jpg
"In lumine tuo videbimus lumen."

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Re: First light for DIY mini-EQ mount

#2

Post by petershah »


Love it...reminds me of the good old days when astronomical equipment for amateurs were virtually non existent......I remember seeing a guy make a scope out of an old metal hospital bed and a EQ mount out of an old car axil.....
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Re: First light for DIY mini-EQ mount

#3

Post by Lady Fraktor »


That is really good Babo!
I like the 'old school' approach of this mount as well, especially the piston as a counterweight!
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Re: First light for DIY mini-EQ mount

#4

Post by SkyHiker »


Very cool, how about adding some color by painting it? For unique artisan character.

I totally buy in on the idea though - at your latitude, putting an Alt/Az mount on a wedge should work better than an Atlas or AVX, because equatorial mounts really suffer by putting the RA axis at that horrible angle. Just make sure that the wedge is properly aligned, which should be quite easy because the axis is near-horizontal. You will have to do a drift alignment to get the wedge in the right position. Or maybe the new NCP-less fast algorithm in Nina or Ekos (I don't have it yet).

With that rig, I would put bearings on the axis though (unless you have some that I didn't see). From working with my barndoor mount, I know how sensitive images are to small errors such as poorly working bearings.
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Re: First light for DIY mini-EQ mount

#5

Post by STEVE333 »


Very creative Joe. Congratulations on getting your DIY mount to work. Impressive!!!

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Re: First light for DIY mini-EQ mount

#6

Post by BABOafrica »


SkyHiker wrote: Sat Aug 06, 2022 5:34 pm Very cool, how about adding some color by painting it? For unique artisan character.

I totally buy in on the idea though - at your latitude, putting an Alt/Az mount on a wedge should work better than an Atlas or AVX, because equatorial mounts really suffer by putting the RA axis at that horrible angle. Just make sure that the wedge is properly aligned, which should be quite easy because the axis is near-horizontal. You will have to do a drift alignment to get the wedge in the right position. Or maybe the new NCP-less fast algorithm in Nina or Ekos (I don't have it yet).

With that rig, I would put bearings on the axis though (unless you have some that I didn't see). From working with my barndoor mount, I know how sensitive images are to small errors such as poorly working bearings.
As far as the alignment... the stars were very close to round even with 30s subs and very rough PA (I just used a compass and a level ... I was only a few minutes south of the equator.) But I could easily do better PA with the drift method.

I was mainly trying to test tracking and it appears to be very close to ideal.

Great idea about the bearing. It should be even smoother.

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Scopes: Stellarvue SV80 Raptor Carbon Fiber ED Doublet / Celestron SCT C8
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Re: First light for DIY mini-EQ mount

#7

Post by Ylem »


Very cool mount, love the piston :)
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Re: First light for DIY mini-EQ mount

#8

Post by Larry 1969 »


How cool!

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Re: First light for DIY mini-EQ mount

#9

Post by Bigzmey »


Nice DIY mount Babo! I tried once to make a mount myself, but I am not as mechanically inclined. :)
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Re: First light for DIY mini-EQ mount

#10

Post by messier 111 »


very ingenious, thx.
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Re: First light for DIY mini-EQ mount

#11

Post by AstroBee »


If you are only a few minutes south of the equator then your R.A. angle is way off in your setup unless I'm not 'reading' your photos right???
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Re: First light for DIY mini-EQ mount

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Post by BABOafrica »


AstroBee wrote: Sun Aug 07, 2022 1:54 am If you are only a few minutes south of the equator then your R.A. angle is way off in your setup unless I'm not 'reading' your photos right???
Well, that's an interesting observation. I certainly cannot claim expertise in telescope mount construction. So let me try to understand and comment.

The business of a few minutes south of the equator for this particular dark site where I was imaging is indisputable. I am very sure I got the proper latitude and longitude from my phone locator app. Besides, I have been living in this area for 30 years. So I know the territory.

I have no idea what you mean by the phrase "R.A. angle". I normally think of a mount being polar aligned to both altitude and azimuth. As far as I know, this means making the axis of rotation for RA rotation coincide (align) as closely as possible with the earth's axis of rotation.

For a geographical location near the equator, the axis of rotation for the mount has to be close to level with the ground.

The axis of rotation for the RA rotation on my mini-EQ mount is the horizontal steel bar in the pictures above. The counterweights hang down off of that horizontal bar (riding on a perpendicular blue bar) and the camera is mounted on top of that. (One of the CWs is an old piston from a car engine... :D )

The RA rotation is controlled by a stepper motor and a gear train (see the BIG gear on one side of the mount connected to some smaller gears). (It took incredible effort to get that big gear centered on a block of wood...)

I can start my imaging session at any RA position that allows the camera to point towards the sky -- all the way from east horizon to west horizon.

I can rotate the camera to any DEC position -- all the way from north horizon to southern horizon. But I have to do that manually and then it remains fixed during an imagining session.

In the pictures posted, the camera is facing a slightly northern DEC position and the RA position is towards the western horizon.

One thing I am sure of -- as you can see in the images above -- is that I got fairly round stars with 30s light frames using a 180mm camera lens. That actually pretty hard to do if you have ever tried.

If you still think there's a problem, please let me know. I would be surprised if I have some big problem. But then again, I have made my fair share of really stupid mistakes over the years.

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Scopes: Stellarvue SV80 Raptor Carbon Fiber ED Doublet / Celestron SCT C8
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Post by AstroBee »


I have no doubt that you know where you are and know what your latitude and longitude is for your location. I saw in your profile also that you are from Kenya.
I meant to say your DEC angle seemed way off, not your R. A. angle.
This is what makes using a regular EQ mount so close to the equator so difficult. Your DEC angle (That steel bar) would need to be pointing directly at the pole.
What I wasn't sure about is if the bottom board was tilted to make additional declination tilt.
While you closeup image is way better than a completely unguiding mount, because it is compensating for the R. A. motion with the motor, there is still significant star trailing in the image. That is because your DEC angle is only compensating for about half of the DEC angle.
I'm at work at the moment on my phone so it's a bit difficult to type and add images, I'll try and add a photo to visually explain what I'm talking about regarding your DEC angle.
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#14

Post by AstroBee »


Here's a photo of my regular EQ rig. I'm at 36° north latitude and if you look closely at the photo, the mount is in the home position pointing directly towards the north pole.

[image]https://photos.smugmug.com/photos/i-SZG ... 6RW-X3.jpg[/image]

If you were to measure the angle (tilt) of the telescope tube from horizontal, you would see that the angle is roughly 36°, matching my latitude.
Greg M.~ "Ad Astra per Aspera"
Scopes: Celestron EdgeHD14", Explore Scientific ED152CF & ED127 APO's, StellarVue SV70T, Classic Orange-Tube C-8, Lunt 80mm Ha double-stack solar scope.
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Post by starfield »


That's fantastic. Quite an accomplishment.
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Re: First light for DIY mini-EQ mount

#16

Post by SkyHiker »


AstroBee wrote: Sun Aug 07, 2022 2:56 pm I have no doubt that you know where you are and know what your latitude and longitude is for your location. I saw in your profile also that you are from Kenya.
I meant to say your DEC angle seemed way off, not your R. A. angle.
This is what makes using a regular EQ mount so close to the equator so difficult. Your DEC angle (That steel bar) would need to be pointing directly at the pole.
What I wasn't sure about is if the bottom board was tilted to make additional declination tilt.
While you closeup image is way better than a completely unguiding mount, because it is compensating for the R. A. motion with the motor, there is still significant star trailing in the image. That is because your DEC angle is only compensating for about half of the DEC angle.
I'm at work at the moment on my phone so it's a bit difficult to type and add images, I'll try and add a photo to visually explain what I'm talking about regarding your DEC angle.
The RA axis is the horizontal axis at the top, which is indeed nearly horizontal as it should be. You are right that the star trails should have been eliminated if the bottom board had its hinge pointed parallel to the equator and would have been slightly tilted to eliminate the few arc minutes error in the RA axis. For a single motor device with everything else ideal (not), it should eliminate star trails.

If you want to autoguide, for a normal equatorial mount the DEC would be built on top of the RA axis. Here, not so. The DEC axis is really the hinge of the bottom board - and the RA axis is built on top of the DEC axis. For that you can add a bolt and a nut that moves the far side of the board up and down and control it with a second Arduino. The lines described by per-axis actuation however will then no longer be perpendicular in the celestial frame, so regular autoguiding algorithms will only work perfectly if the scope is pointed at the meridian and less perfect elsewhere - but probably still good enough if it is not too far away. I speak from experience because this is how I did it with my dual-axis autoguided barndoor with my 10" Dobsonian on top.
... Henk. :D Telescopes: GSO 12" Astrograph, "Comet Hunter" MN152, ES ED127CF, ES ED80, WO Redcat51, Z12, AT6RC, Celestron Skymaster 20x80, Mounts and tripod: Losmandy G11S with OnStep, AVX, Tiltall, Cameras: ASI2600MC, ASI2600MM, ASI120 mini, Fuji X-a1, Canon XSi, T6, ELPH 100HS, DIY: OnStep controller, Pi4b/power rig, Afocal adapter, Foldable Dob base, Az/Alt Dob setting circles, Accessories: ZWO 36 mm filter wheel, TV Paracorr 2, Baader MPCC Mk III, ES FF, SSAG, QHY OAG-M, EAF electronic focuser, Plossls, Barlows, Telrad, Laser collimators (Seben LK1, Z12, Howie Glatter), Cheshire, 2 Orion RACIs 8x50, Software: KStars-Ekos, DSS, PHD2, Nebulosity, Photo Gallery, Gimp, CHDK, Computers:Pi4b, 2x running KStars/Ekos, Toshiba Satellite 17", Website:Henk's astro images
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Re: First light for DIY mini-EQ mount

#17

Post by AstroBee »


I was obviously looking at the wrong steel bar. I was looking at the one with the counterweights on it.
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Scopes: Celestron EdgeHD14", Explore Scientific ED152CF & ED127 APO's, StellarVue SV70T, Classic Orange-Tube C-8, Lunt 80mm Ha double-stack solar scope.
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Eyepieces: 27mm TeleVue Panoptic, 4mm TeleVue Radian, Explore Scientific 82° 30mm, 6.7mm , Baader 13mm Hyperion, Explore Scientific 70° 10mm, 15mm, 20mm, Meade 8.8mm UWA
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Re: First light for DIY mini-EQ mount

#18

Post by SkyHiker »


SkyHiker wrote: Sun Aug 07, 2022 3:32 pm The RA axis is the horizontal axis at the top, which is indeed nearly horizontal as it should be. You are right that the star trails should have been eliminated if the bottom board had its hinge pointed parallel to the equator and would have been slightly tilted to eliminate the few arc minutes error in the RA axis. For a single motor device with everything else ideal (not), it should eliminate star trails.

If you want to autoguide, for a normal equatorial mount the DEC would be built on top of the RA axis. Here, not so. The DEC axis is really the hinge of the bottom board - and the RA axis is built on top of the DEC axis. For that you can add a bolt and a nut that moves the far side of the board up and down and control it with a second Arduino. The lines described by per-axis actuation however will then no longer be perpendicular in the celestial frame, so regular autoguiding algorithms will only work perfectly if the scope is pointed at the meridian and less perfect elsewhere - but probably still good enough if it is not too far away. I speak from experience because this is how I did it with my dual-axis autoguided barndoor with my 10" Dobsonian on top.
I have to correct myself - what I called the DEC axis is really the Alt axis of an equatorial mount. The DEC axis here is the one where the piston is pointing, as with a regular EQ mount. My bad! It all looks different. Anyhow, the easiest way to do some form of autoguiding is actuating the Alt axis, I think.
... Henk. :D Telescopes: GSO 12" Astrograph, "Comet Hunter" MN152, ES ED127CF, ES ED80, WO Redcat51, Z12, AT6RC, Celestron Skymaster 20x80, Mounts and tripod: Losmandy G11S with OnStep, AVX, Tiltall, Cameras: ASI2600MC, ASI2600MM, ASI120 mini, Fuji X-a1, Canon XSi, T6, ELPH 100HS, DIY: OnStep controller, Pi4b/power rig, Afocal adapter, Foldable Dob base, Az/Alt Dob setting circles, Accessories: ZWO 36 mm filter wheel, TV Paracorr 2, Baader MPCC Mk III, ES FF, SSAG, QHY OAG-M, EAF electronic focuser, Plossls, Barlows, Telrad, Laser collimators (Seben LK1, Z12, Howie Glatter), Cheshire, 2 Orion RACIs 8x50, Software: KStars-Ekos, DSS, PHD2, Nebulosity, Photo Gallery, Gimp, CHDK, Computers:Pi4b, 2x running KStars/Ekos, Toshiba Satellite 17", Website:Henk's astro images
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Re: First light for DIY mini-EQ mount

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Post by BABOafrica »


Thanks for looking at that details.
SkyHiker wrote: Sun Aug 07, 2022 3:32 pm
The RA axis is the horizontal axis at the top, which is indeed nearly horizontal as it should be. You are right that the star trails should have been eliminated if the bottom board had its hinge pointed parallel to the equator and would have been slightly tilted to eliminate the few arc minutes error in the RA axis. For a single motor device with everything else ideal (not), it should eliminate star trails.
There is a hinge for the two boards that make up the bottom platform. This allows me to adjust the altitude of the RA axis.

I know I need to keep the RA axis facing exactly north - south (for proper azimuth alignment). Which is the same as keeping the hinge on the board parallel to the equator.

I did not spend a lot of time the other night trying to get good polar alignment. I just used a compass to set the AZ and a level to set the ALT.

Perhaps I am biased, but I think the second image above (which is a 50% crop) shows lots of nice round stars.

BABO
"In lumine tuo videbimus lumen."

Scopes: Stellarvue SV80 Raptor Carbon Fiber ED Doublet / Celestron SCT C8
Williams Optics 66mm APO / DIY 8" f/4 Newtonian astrograph / Nikon 180mm f/2.8
Mounts: Orion Atlas EQ-G / Celestron AVX / DIY mini-equatorial
Cameras: QHY163m / Fujifilm X-A1 (modded) / Fuji X-A2 (not modded) / Orion StarShoot Auto Guider
Filters: ZWO 7nm NB set / ZWO LRGB set / ZWO Dual Band / Astronomics UHC
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