PMC-Eight GoTo or Gemini?
- BamaDon
- Earth Ambassador
- Articles: 0
- Posts: 49
- Joined: Wed Sep 04, 2019 4:53 pm
- 4
- Location: Alabama, USA
- Status:
Offline
PMC-Eight GoTo or Gemini?
Which do you prefer?
I'm not in the market yet, but I spoke with Scott - not Scott Losmandy - of Explore Scientific at the Winter Star Party about the advantages of the PMC Eight.
He said that the PMC uses stepper motors, and so if the mount runs into an obstacle that stops the mount from moving the electronics won't burn out.
and that the Gemini 2, which uses server motors, would.
Another advantage of the PMC is that the code is open source. and so others, or even I could edit the code and add features.
Comments?
I'm not in the market yet, but I spoke with Scott - not Scott Losmandy - of Explore Scientific at the Winter Star Party about the advantages of the PMC Eight.
He said that the PMC uses stepper motors, and so if the mount runs into an obstacle that stops the mount from moving the electronics won't burn out.
and that the Gemini 2, which uses server motors, would.
Another advantage of the PMC is that the code is open source. and so others, or even I could edit the code and add features.
Comments?
Don
Scopes: Criterion RV-6; 8" f/8 homebuilt; 10" Cave OTA; 12.5" Dobsonian; Celestron C11 Mounts: Losmandy G11 Eyepieces: ES 82° 24, 18, 14, 11, 8.8, 6.7, 4.7; Meade RG: Erfle 20; Ortho 16.8, 10.5, 7 Binoculars: Orion Ultraview 10x50; Filters: DGM NPB, O-III; Orion SkyGlow; DSLR: Canon t6i
Scopes: Criterion RV-6; 8" f/8 homebuilt; 10" Cave OTA; 12.5" Dobsonian; Celestron C11 Mounts: Losmandy G11 Eyepieces: ES 82° 24, 18, 14, 11, 8.8, 6.7, 4.7; Meade RG: Erfle 20; Ortho 16.8, 10.5, 7 Binoculars: Orion Ultraview 10x50; Filters: DGM NPB, O-III; Orion SkyGlow; DSLR: Canon t6i
- bladekeeper
- Inter-Galactic Ambassador
- Articles: 0
- Posts: 3603
- Joined: Thu Apr 25, 2019 2:39 am
- 5
- Location: Lowell, Arkansas, US
- Status:
Offline
-
TSS Awards Badges
TSS Photo of the Day
Re: PMC-Eight GoTo or Gemini?
Well, not much to offer, but I have a buddy who owns the EXOS-2GT PMC mount. It's a pretty darn quiet mount when slewing.
That's all I've got...
That's all I've got...
Bryan
Scopes: Apertura AD12 f/5; Celestron C6-R f/8; ES AR127 f/6.4; Stellarvue SV102T f/7; iOptron MC90 f/13.3; Orion ST80A f/5; ES ED80 f/6; Celestron Premium 80 f/11.4; Celestron C80 f/11.4; Unitron Model 142 f/16; Meade NG60 f/10
Mounts: Celestron AVX; Bresser EXOS-2; ES Twilight I; ES Twilight II; iOptron Cube-G; AZ3/wood tripod; Vixen Polaris
Binoculars: Pentax PCF WP II 10×50, Bresser Corvette 10×50, Bresser Hunter 16×50 and 8×40, Garrett Gemini 12×60 LW, Gordon 10×50, Apogee 20×100
Scopes: Apertura AD12 f/5; Celestron C6-R f/8; ES AR127 f/6.4; Stellarvue SV102T f/7; iOptron MC90 f/13.3; Orion ST80A f/5; ES ED80 f/6; Celestron Premium 80 f/11.4; Celestron C80 f/11.4; Unitron Model 142 f/16; Meade NG60 f/10
Mounts: Celestron AVX; Bresser EXOS-2; ES Twilight I; ES Twilight II; iOptron Cube-G; AZ3/wood tripod; Vixen Polaris
Binoculars: Pentax PCF WP II 10×50, Bresser Corvette 10×50, Bresser Hunter 16×50 and 8×40, Garrett Gemini 12×60 LW, Gordon 10×50, Apogee 20×100
- SonnyE
- Interdicted
- Articles: 0
- Posts: 52
- Joined: Wed Jan 29, 2020 4:08 am
- 4
- Status:
Offline
Re: PMC-Eight GoTo or Gemini?
Any comments?
Yeah, you talked to the wrong Scott. He lied to you.
But I imagine you will go whatever way you want to.
If this is what you are looking at, it isn't even close to a Losmandy mount, or a Gemini controller.
My GM811G HD tripod weighs more than that entire mount.
Yeah, you talked to the wrong Scott. He lied to you.
But I imagine you will go whatever way you want to.
If this is what you are looking at, it isn't even close to a Losmandy mount, or a Gemini controller.
My GM811G HD tripod weighs more than that entire mount.
- Lady Fraktor
- Infinity and Beyond Ambassador
- Articles: 0
- Posts: 10002
- Joined: Mon Apr 29, 2019 9:14 pm
- 5
- Location: Slovakia
- Status:
Offline
Re: PMC-Eight GoTo or Gemini?
I do not see open source programming as an advantage, it also took a couple of years for someone to write a user manual so do not expect it to be up to date or problem solving to happen quickly.
Between the two the Losmandy/ Gemini is a much better combination.
My long past G-11 had mechanical issues but I would still purchase one with the Gemini before the PMC
Between the two the Losmandy/ Gemini is a much better combination.
My long past G-11 had mechanical issues but I would still purchase one with the Gemini before the PMC
Gabrielle
See Far Sticks: Elita 103/1575, AOM FLT 105/1000, Bresser 127/1200 BV, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS 100/1000, Vixen SD115s/885
EQ: TAL MT-1, Vixen SXP, SXP2, AXJ, AXD
Az/Alt: AYO Digi II, Stellarvue M2C, Argo Navis encoders on both
Tripods: Berlebach Planet (2), Uni 28 Astro, Report 372, TAL factory maple, Vixen ASG-CB90, Vixen AXD-TR102
Diagonals: Astro-Physics, Baader Amici, Baader Herschel, iStar Blue, Stellarvue DX, Tak prism, TAL, Vixen
Eyepieces: Antares to Zeiss (1011110)
The only culture I have is from yogurt
See Far Sticks: Elita 103/1575, AOM FLT 105/1000, Bresser 127/1200 BV, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS 100/1000, Vixen SD115s/885
EQ: TAL MT-1, Vixen SXP, SXP2, AXJ, AXD
Az/Alt: AYO Digi II, Stellarvue M2C, Argo Navis encoders on both
Tripods: Berlebach Planet (2), Uni 28 Astro, Report 372, TAL factory maple, Vixen ASG-CB90, Vixen AXD-TR102
Diagonals: Astro-Physics, Baader Amici, Baader Herschel, iStar Blue, Stellarvue DX, Tak prism, TAL, Vixen
Eyepieces: Antares to Zeiss (1011110)
The only culture I have is from yogurt
- Voyageur
- Orion Spur Ambassador
- Articles: 0
- Posts: 682
- Joined: Mon May 06, 2019 1:50 pm
- 4
- Location: Leelanau County, Michigan, USA
- Status:
Offline
Re: PMC-Eight GoTo or Gemini?
You already have the Losmandy G11 and are debating which goto to add, is that correct?
The Gemini uses servo motors (not server). Maybe read more about the servo motors before deciding they are inferior. I won't go so far as to call theES rep a liar, but he is naturally going to promote the in-house product. Hope you can obtain some unbiased reviews.
The Gemini uses servo motors (not server). Maybe read more about the servo motors before deciding they are inferior. I won't go so far as to call the
Scopes: Vixen VMC200L, D=200mm, F=1950, f/9.75; Televue 2" Everbright diagonal. Coronado PST; AstroTech EDT 80mm, F=480, f/6.
Mounts: Vixen SXW/Starbook (original); Stellarvue M2C alt-az.
Eyepieces: Televue: 55mm Plossl, 22mm Panoptic, 17.3mm Delos, 13mm Nagler, c. 1980, 11mm Plossl, 7mm Nagler, 5mm Radian; Meade 15mm Super Plossl; VERNONSCOPE 2.4X BARLOW
Binoculars: Leica 8x32 Trinovids, circa 1997; Orion Megaview 20x80, Orion Paragon Plus mount.
Mounts: Vixen SXW/Starbook (original); Stellarvue M2C alt-az.
Eyepieces: Televue: 55mm Plossl, 22mm Panoptic, 17.3mm Delos, 13mm Nagler, c. 1980, 11mm Plossl, 7mm Nagler, 5mm Radian; Meade 15mm Super Plossl; VERNONSCOPE 2.4X BARLOW
Binoculars: Leica 8x32 Trinovids, circa 1997; Orion Megaview 20x80, Orion Paragon Plus mount.
- SkyHiker
- Local Group Ambassador
- Articles: 0
- Posts: 2293
- Joined: Sat May 11, 2019 8:40 pm
- 4
- Location: Santa Barbara, CA
- Status:
Offline
-
TSS Photo of the Day
TSS Awards Badges
Re: PMC-Eight GoTo or Gemini?
I wish you phrased that differently. Scott Roberts is the founder of Explore Sientific and has supported our community in many ways, by supporting star parties financially, and providing affordable products with great value. The link you should have provided is this one as you could easily have found by going to theSonnyE wrote: ↑Thu Mar 05, 2020 3:25 am Any comments?
Yeah, you talked to the wrong Scott. He lied to you.
But I imagine you will go whatever way you want to.
If this is what you are looking at, it isn't even close to a Losmandy mount, or a Gemini controller.
My GM811G HD tripod weighs more than that entire mount.
I followed the development of the PMC8 somewhat from the beginning, when I met the developer at the RTMC many years ago. Scott always brought his G11 with feet buried into the ground. Having an alternative to the Gemini system is never a bad thing, of course this alternative also costs quite a bit. Originally it was controlled by a Windows tablet that is
The client side ExploreStars
Acceptance of the PMC8 system has been a bit of a struggle early on but the system should now hopefully be mature. I would look for user reviews because you don't want to depend on programming skills to fix any problems yourself. That said, compared to other companies that sell closed hardware and software this open architecture is nice to have. Especially the client side that supports
I suppose this is comparable to using Stellarium (also open source) or
... Henk. 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
- pakarinen
- Inter-Galactic Ambassador
- Articles: 0
- Posts: 4033
- Joined: Fri Jun 14, 2019 3:33 pm
- 4
- Location: NE Illinois
- Status:
Offline
-
TSS Awards Badges
Re: PMC-Eight GoTo or Gemini?
FWIW, I think Rod Molise (sp?) wrote that he really dislikes PMC-8. Don't remember details and I could be attributing that comment to the wrong person, so take it with a pinch of salt and some lime.
I agree that more research would be a wide course of action.
I agree that more research would be a wide course of action.
=============================================================================
I drink tea, I read books, I look at stars when I'm not cursing clouds. It's what I do.
=============================================================================
AT50, AT72EDII, ST80, ST102; Scopetech Zero, AZ-GTi, AZ Pronto; Innorel RT90C, Oberwerk 5000; Orion Giantview 15x70s, Vortex 8x42s, Navy surplus 7x50s, Nikon 10x50s
I drink tea, I read books, I look at stars when I'm not cursing clouds. It's what I do.
=============================================================================
AT50, AT72EDII, ST80, ST102; Scopetech Zero, AZ-GTi, AZ Pronto; Innorel RT90C, Oberwerk 5000; Orion Giantview 15x70s, Vortex 8x42s, Navy surplus 7x50s, Nikon 10x50s
- SonnyE
- Interdicted
- Articles: 0
- Posts: 52
- Joined: Wed Jan 29, 2020 4:08 am
- 4
- Status:
Offline
Re: PMC-Eight GoTo or Gemini?
>SkyHiker wrote: ↑Thu Mar 05, 2020 12:36 pmI wish you phrased that differently. Scott Roberts is the founder of Explore Sientific and has supported our community in many ways, by supporting star parties financially, and providing affordable products with great value. The link you should have provided is this one as you could easily have found by going to theSonnyE wrote: ↑Thu Mar 05, 2020 3:25 am Any comments?
He asked: "Any comments?"
Yeah, you talked to the wrong Scott. He lied to you.
But I imagine you will go whatever way you want to.
If this is what you are looking at, it isn't even close to a Losmandy mount, or a Gemini controller.
My GM811G HD tripod weighs more than that entire mount.ES website: https://explorescientificusa.com/collec ... o-software
I followed the development of the PMC8 somewhat from the beginning, when I met the developer at the RTMC many years ago. Scott always brought his G11 with feet buried into the ground. Having an alternative to the Gemini system is never a bad thing, of course this alternative also costs quite a bit. Originally it was controlled by a Windows tablet that isASCOM based. Fortunately they now support INDI as well and you can use Android and iOS to control it, too, see https://explorescientificusa.com/pages/ ... ght-system
The client side ExploreStarsapp is open source I think, the PMC controller firmware is not but it uses a documented public API so I suppose you can substitute your own hardware and firmware while the ExploreStarsapp will still work. This is nice because writing your owngoto logic is the hard part. I got this info from https://explorescientificusa.com/pages/ ... -community , hopefully I understood it correctly.
Acceptance of the PMC8 system has been a bit of a struggle early on but the system should now hopefully be mature. I would look for user reviews because you don't want to depend on programming skills to fix any problems yourself. That said, compared to other companies that sell closed hardware and software this open architecture is nice to have. Especially the client side that supportsASCOM , INDI and ST4.
I suppose this is comparable to using Stellarium (also open source) orCDC in combination with EQMOD and/orASCOM , which is what most of us use. Since the PMC8 supportsASCOM you can probably control it that way too without using ExploreStars, I don't know for sure. Both Gemini and PMC8 supportASCOM so you should be able to use anyASCOM based alternatives. The one thing you won't have with the PMC8 is a hand controller but you can use an Android cell phone or tablet.
>
>
>
OK, SkyHiker, I'll elaborate for you.
"He said that the PMC uses stepper motors, and so if the mount runs into an obstacle that stops the mount from moving the electronics won't burn out.
and that the Gemini 2, which uses server motors, would."
I can't say he did say. Nor can I say he did not say. But the broad brush statement is wrong. Therefore, it is untrue.
Based on my personal experiences, my GM811G HAS "crashed" into itself twice. It stops, shuts down, reboots, and waits for the operator to wake up and pay attention.
It did not burn out.
Overloading is controlled in the drive for the device. NOT in the type of motor used.
Also, the Gemini system is, in and of itself, a micro computer. The PMC8 requires an external computer to "think" for it. Based on what I've read on it.
Further, Stepper motors have just that, steps they operate in. I can give you instances where one step is too much, and one step back is not right either.
I built my own focuser drive from Tekky Daves project. In my case, I have >24,000 steps in the full range of the draw tube of my refractors travel. Each step works out to 0.00123" (123/10,000 of an inch, or 3.1242e-5 meter). Or roughly 1 1/4 thousandths of an inch.
Stepper motors are absolute. This step, or that step. No therebetween.
Servo motors are not. Controlling the voltage and current, a servo can be engineered to stop, or more importantly, not stop, at any of the places a stepper misses. Or to make it clear, a Servo has infinite places it can be brought to. Or it can simply creep through that .00123" distance.
In the case of tracking and guiding, a stepper drive is going to step. I never really thought a 6 second video I made would ever be of value when I made it, but this is a good spot for it in this conversation. An Unguided mount and how it's adjustments affect its motion.
That motion helps to demonstrate why stars can get "bloated" in astrophotography. I used to get horribly bloated stars when I first started out. But, I knew I would get better. And I have over the years.
So, now you have been presented these truths about the differences between the two types of drives. A Stepper is here, or it is there. But a servo can infinitely adjust as is moves like clockwork with the rotation of the Earth.
The camera never lies. It simply records what it is presented. When the device it is mounted to can smoothly follow the stars as the Earth rotates. If it steps, the recorded image will also show that Second Hand ticking type of motion.
I hope that helps you, and more importantly, Others, there is indeed a distinct difference. And Scott Losmandy has the experience to know it. He's been hands on involved since 1986. His goal is not the sale, but the quality in his products.
Other folks, well, lets say they have sales to make. If they can sway an interested party to their wares, Cha-Ching, next in line. Even if it means making purported statements that are lies.
And that is IF the guy really said that.
You folks don't know me well yet, but I have over 42 years experience in the Electro-mechanical world of controls. I'm trying to forget some of the absolute Bologna that is in my head. But if I can, I will try and share some of what I've learned in life.
Any Comments? Well, that opens the door... to a dark and sometimes scary place. But remember, knowledge is power. Gather when you can.
If you would like, HERE is a link to true Losmandy Users who can elaborate much more, and probably much better than I.
But I can tell you that (Theoretically) it takes 6.25 X 10 to the 18th power (625, followed by 26 zeros) of electrons passing a point with 1 volt of pressure to equal 1 amp of current. (Oh, how I wish I could forget that!)
Oh, and as an aside, my mount, and everything involved, is being run by
Stepper motors are good for some things. I do actually like the repeat accuracy I'm seeing with my stepper driven focuser. I have target steps for my most used filters I can enter and land close to in-focus. Then step a bit this way, or step the other, then make single steps to try and achieve as close to focused as I can see.
But are they the cats meow for mount driving? Humm, I personally can see a difference. The Earths rotation doesn't step. What do you think?
(I don't have anything to sell)
- Graeme1858
- Co-Administrator
- Articles: 1
- Posts: 7453
- Joined: Mon Jun 24, 2019 7:16 pm
- 4
- Location: North Kent, UK
- Status:
Offline
-
TSS Awards Badges
TSS Photo of the Day
I Broke The Forum.
Re: PMC-Eight GoTo or Gemini?
It takes 6.25 x 10 ^18 electrons (625, followed by 16 zeros) passing a point with 1 volt of pressure per second to equal 1 amp of current.
Regards
Graeme
______________________________________________
Celestron 9.25 f10 SCT, f6.3FR, CGX mount.
ASI1600MM Pro, ASI294MC Pro, ASI224MC
ZWO EFW, ZWO OAG, ASI220MM Mini.
APM 11x70 ED APO Binoculars.
https://www.averywayobservatory.co.uk/
Celestron 9.25 f10 SCT, f6.3FR, CGX mount.
ASI1600MM Pro, ASI294MC Pro, ASI224MC
ZWO EFW, ZWO OAG, ASI220MM Mini.
APM 11x70 ED APO Binoculars.
https://www.averywayobservatory.co.uk/
- sdtopensied
- Earth Ambassador
- Articles: 0
- Posts: 5
- Joined: Thu Mar 05, 2020 9:05 pm
- 4
- Location: Atlanta, Georgia (USA)
- Status:
Offline
Re: PMC-Eight GoTo or Gemini?
I have a G-11 PMC-Eight and I'm happy with it.
I saw some comments that the OP was lied to by Scott Roberts atES . I think it's more likely that Scott was a bit misinformed and his statement lacked context. I've known Scott for a long time and while I have known him to be misinformed at times, I have never known him to deliberately mislead anyone.
Getting back to what the OP was asking for...
If you prefer a mount with a traditional, self-contained hand controller, the PMC-Eight is not for you. The PMC-Eight is just a motor controller and all of the intelligence has been abstracted up a layer toASCOM , INDI, or the Explore Stars app . The iPad version of the Explore Stars app is great. I'm not crazy about the Windows version or the Android version of the app , particularly the install processes as they're more difficult than they should be. The ASCOM driver is solid. It's not written as a server so you'll need to use POTH for multiple connections (e.g. PHD2 and Cartes du Ciel). A server version of the driver is pending but no ETA that I'm aware of. The INDI driver is solid as well. I've used it a bit with StellarMate and had no issues. I prefer Windows, so I stick with ASCOM .
There have been some growing pains and that's not something that was unexpected. I've had the mount for over a year and I'm pretty happy with it.
A bit of advice if you're looking at a G-11 from Explore Scientific with the PMC-Eight...do yourself a favor and get a couple of one piece worm blocks. The two piece worm blocks thatES ships the mount with will be fine until you have to adjust the mount, and you will eventually have to adjust it. The trials and tribulations of adjusting the two piece worm block are well documented and can be readily found with a little Googling.
I have used quite a few mounts over the years, some with servo motors and some with stepper motors. In retrospect, I had fewer issues with mounts with stepper motors (e.g.EQ -6, PMC-8) than I had with mounts with servo motors (Celestron CGEM , Meade LXD-75), so a general mount requirement of mine is that it needs to have stepper motors to make my short list.
You'll get a good mount either way you go. You'll get a more mature product if you go with a Losmandy/Gemini-II. If you like to see what goes on under the hood and you have some coding skills and you want to be involved with the product or fork it and go a different direction on your own, consider the PMC-8. TheASCOM driver is written in VB and C#. I believe Explore Stars is written in C#/.NET Core for all versions and is a UWP app .
TheES folks on the PMC-Eight Groups.io group are responsive and helpful and keep the forum open, friendly, and organized. Most of the talk lately is about the iExos 100 as there are a lot more of them out there.
My perception of the Losmandy Groups.io group is that it's community driven rather than driven by Losmandy so you may or may not get the ear of someone who can solve your problem.
I wrote a review of the PMC-Eight and it's posted on theES site that has more details. I was honest and up-front about the issues I had and the review wasn't edited before it was posted on their site. I also wasn't compensated for the review.
https://explorescientificusa.com/blogs/ ... eight-g-11
My astrobin page with images taken using the G-11 PMC-Eight and other mounts...the good, the bad, and the ugly. Most of my stuff survived the meltdown.
https://www.astrobin.com/users/sdtopensied/
Hope this helps.
-Steve
I saw some comments that the OP was lied to by Scott Roberts at
Getting back to what the OP was asking for...
If you prefer a mount with a traditional, self-contained hand controller, the PMC-Eight is not for you. The PMC-Eight is just a motor controller and all of the intelligence has been abstracted up a layer to
There have been some growing pains and that's not something that was unexpected. I've had the mount for over a year and I'm pretty happy with it.
A bit of advice if you're looking at a G-11 from Explore Scientific with the PMC-Eight...do yourself a favor and get a couple of one piece worm blocks. The two piece worm blocks that
I have used quite a few mounts over the years, some with servo motors and some with stepper motors. In retrospect, I had fewer issues with mounts with stepper motors (e.g.
You'll get a good mount either way you go. You'll get a more mature product if you go with a Losmandy/Gemini-II. If you like to see what goes on under the hood and you have some coding skills and you want to be involved with the product or fork it and go a different direction on your own, consider the PMC-8. The
The
My perception of the Losmandy Groups.io group is that it's community driven rather than driven by Losmandy so you may or may not get the ear of someone who can solve your problem.
I wrote a review of the PMC-Eight and it's posted on the
https://explorescientificusa.com/blogs/ ... eight-g-11
My astrobin page with images taken using the G-11 PMC-Eight and other mounts...the good, the bad, and the ugly. Most of my stuff survived the meltdown.
https://www.astrobin.com/users/sdtopensied/
Hope this helps.
-Steve
- helicon
- Co-Administrator
- Articles: 592
- Posts: 12374
- Joined: Mon May 06, 2019 1:35 pm
- 4
- Location: Washington
- Status:
Offline
-
TSS Awards Badges
Re: PMC-Eight GoTo or Gemini?
Hello Steve and Welcome tosdtopensied wrote: ↑Thu Mar 05, 2020 11:24 pm I have a G-11 PMC-Eight and I'm happy with it.
I saw some comments that the OP was lied to by Scott Roberts at ES. I think it's more likely that Scott was a bit misinformed and his statement lacked context. I've known Scott for a long time and while I have known him to be misinformed at times, I have never known him to deliberately mislead anyone.
Getting back to what the OP was asking for...
If you prefer a mount with a traditional, self-contained hand controller, the PMC-Eight is not for you. The PMC-Eight is just a motor controller and all of the intelligence has been abstracted up a layer to ASCOM, INDI, or the Explore Stars app. The iPad version of the Explore Stars app is great. I'm not crazy about the Windows version or the Android version of the app, particularly the install processes as they're more difficult than they should be. The ASCOM driver is solid. It's not written as a server so you'll need to use POTH for multiple connections (e.g. PHD2 and Cartes du Ciel). A server version of the driver is pending but no ETA that I'm aware of. The INDI driver is solid as well. I've used it a bit with StellarMate and had no issues. I prefer Windows, so I stick with ASCOM.
There have been some growing pains and that's not something that was unexpected. I've had the mount for over a year and I'm pretty happy with it.
A bit of advice if you're looking at a G-11 from Explore Scientific with the PMC-Eight...do yourself a favor and get a couple of one piece worm blocks. The two piece worm blocks that ES ships the mount with will be fine until you have to adjust the mount, and you will eventually have to adjust it. The trials and tribulations of adjusting the two piece worm block are well documented and can be readily found with a little Googling.
I have used quite a few mounts over the years, some with servo motors and some with stepper motors. In retrospect, I had fewer issues with mounts with stepper motors (e.g. EQ-6, PMC-8) than I had with mounts with servo motors (Celestron CGEM, Meade LXD-75), so a general mount requirement of mine is that it needs to have stepper motors to make my short list.
You'll get a good mount either way you go. You'll get a more mature product if you go with a Losmandy/Gemini-II. If you like to see what goes on under the hood and you have some coding skills and you want to be involved with the product or fork it and go a different direction on your own, consider the PMC-8. The ASCOM driver is written in VB and C#. I believe Explore Stars is written in C#/.NET Core for all versions and is a UWP app.
The ES folks on the PMC-Eight Groups.io group are responsive and helpful and keep the forum open, friendly, and organized. Most of the talk lately is about the iExos 100 as there are a lot more of them out there.
My perception of the Losmandy Groups.io group is that it's community driven rather than driven by Losmandy so you may or may not get the ear of someone who can solve your problem.
I wrote a review of the PMC-Eight and it's posted on the ES site that has more details. I was honest and up-front about the issues I had and the review wasn't edited before it was posted on their site. I also wasn't compensated for the review.
https://explorescientificusa.com/blogs/ ... eight-g-11
My astrobin page with images taken using the G-11 PMC-Eight and other mounts...the good, the bad, and the ugly. Most of my stuff survived the meltdown.
https://www.astrobin.com/users/sdtopensied/
Hope this helps.
-Steve
-Michael
Refractors: ES AR152 f/6.5 Achromat on Twilight II, Celestron 102mm XLT f/9.8 on Celestron Heavy Duty Alt Az mount, KOWA 90mm spotting scope
Binoculars: Celestron SkyMaster 15x70, Bushnell 10x50
Eyepieces: Various, GSO Superview, 9mm Plossl, Celestron 25mm Plossl
Camera: ZWO ASI 120
Naked Eye: Two Eyeballs
Latitude: 48.7229° N
Refractors: ES AR152 f/6.5 Achromat on Twilight II, Celestron 102mm XLT f/9.8 on Celestron Heavy Duty Alt Az mount, KOWA 90mm spotting scope
Binoculars: Celestron SkyMaster 15x70, Bushnell 10x50
Eyepieces: Various, GSO Superview, 9mm Plossl, Celestron 25mm Plossl
Camera: ZWO ASI 120
Naked Eye: Two Eyeballs
Latitude: 48.7229° N
- BamaDon
- Earth Ambassador
- Articles: 0
- Posts: 49
- Joined: Wed Sep 04, 2019 4:53 pm
- 4
- Location: Alabama, USA
- Status:
Offline
Re: PMC-Eight GoTo or Gemini?
Wow - I did not anticipate such a whirlwind of responses!
RE “server” motor - that’s a typo. I know they’re “Servo” Motors.
I know servo motors can be of extremely high quality. I’ve worked with Parker Motors, and programmed them through LabView. One of my concerns with steppers is that they step - finite steps over and over, which can create a constant jerking motion. It’s possible to micro-step the motors to reduce this, and if it gets small enough the results might be acceptable, but I’d prefer servos.
Servos are DC motors with a computer to control them, and encoders to measure their motion. You can command them to move at a given speed, accelerate at a certain rate, move to a given position - they are great! And they move smoothly. You give them a velocity and they move at that rate. If it’s too slow, you adjust the velocity. You can control the acceleration when moving from one velocity to another. Servos are the modern solution to moving telescopes.
Which is why I was curious about the PMC Eight. I wanted to know why they would use steppers. I saw an opportunity to ask, and I did.
I was also intrigued that the PMC Eight is at the same price point as the Gemini.
FYI I have a big, heavy G11 mount - an older model with the Celestron branding.
Thanks to everyone for their comments.
RE “server” motor - that’s a typo. I know they’re “Servo” Motors.
I know servo motors can be of extremely high quality. I’ve worked with Parker Motors, and programmed them through LabView. One of my concerns with steppers is that they step - finite steps over and over, which can create a constant jerking motion. It’s possible to micro-step the motors to reduce this, and if it gets small enough the results might be acceptable, but I’d prefer servos.
Servos are DC motors with a computer to control them, and encoders to measure their motion. You can command them to move at a given speed, accelerate at a certain rate, move to a given position - they are great! And they move smoothly. You give them a velocity and they move at that rate. If it’s too slow, you adjust the velocity. You can control the acceleration when moving from one velocity to another. Servos are the modern solution to moving telescopes.
Which is why I was curious about the PMC Eight. I wanted to know why they would use steppers. I saw an opportunity to ask, and I did.
I was also intrigued that the PMC Eight is at the same price point as the Gemini.
FYI I have a big, heavy G11 mount - an older model with the Celestron branding.
Thanks to everyone for their comments.
Don
Scopes: Criterion RV-6; 8" f/8 homebuilt; 10" Cave OTA; 12.5" Dobsonian; Celestron C11 Mounts: Losmandy G11 Eyepieces: ES 82° 24, 18, 14, 11, 8.8, 6.7, 4.7; Meade RG: Erfle 20; Ortho 16.8, 10.5, 7 Binoculars: Orion Ultraview 10x50; Filters: DGM NPB, O-III; Orion SkyGlow; DSLR: Canon t6i
Scopes: Criterion RV-6; 8" f/8 homebuilt; 10" Cave OTA; 12.5" Dobsonian; Celestron C11 Mounts: Losmandy G11 Eyepieces: ES 82° 24, 18, 14, 11, 8.8, 6.7, 4.7; Meade RG: Erfle 20; Ortho 16.8, 10.5, 7 Binoculars: Orion Ultraview 10x50; Filters: DGM NPB, O-III; Orion SkyGlow; DSLR: Canon t6i
- sdtopensied
- Earth Ambassador
- Articles: 0
- Posts: 5
- Joined: Thu Mar 05, 2020 9:05 pm
- 4
- Location: Atlanta, Georgia (USA)
- Status:
Offline
Re: PMC-Eight GoTo or Gemini?
A possible alternative to both the PMC-Eight and the Gemini II...
Haven’t had the guts to pull the trigger and order one yet, but I’ve talked to one person who has it on their G-11 and they’re happy with it. You’ll useEQ -Mod to control it. I’ve ordered other smaller stuff from these folks in the past and have been pleased.
Uses motors and couplers similar to the PMC-Eight.
https://astro-gadget.net/gadgets/contro ... r-losmandy
-Steve
Haven’t had the guts to pull the trigger and order one yet, but I’ve talked to one person who has it on their G-11 and they’re happy with it. You’ll use
Uses motors and couplers similar to the PMC-Eight.
https://astro-gadget.net/gadgets/contro ... r-losmandy
-Steve
- SonnyE
- Interdicted
- Articles: 0
- Posts: 52
- Joined: Wed Jan 29, 2020 4:08 am
- 4
- Status:
Offline
Re: PMC-Eight GoTo or Gemini?
The only reason I can think of for the industry moving towards stepper motors would be like cars and laundry detergent.
Draw folks to "New! and Improved!"
But a stepper, even at a tremendously low gearing, is still ticking the motion.
Where a servo can be smooth in between the steps of a stepper motor.
I use a Stepper Motor to drive my focuser. It works great and can go back to steps that were in focus at a previous time and temperature, and all the variables we must deal with.
Then I still have to fish around to get what my eyes think are the focus of the moment. But I have seen where one is off that way, but the other appears off the other way.
Something in-between would be just right.
Where all bets are off is when ground vibrations are considered. We are on a bowl of Jello. Or a ball, if you will.
I had the opportunity to work with Seismologists installing equipment back to a seismic pedestal.
Equipment so sensitive it recorded us moving near it, and vibrations from traffic 1/2 mile away. And up to The Big One that never has shown up.
Lots of options! Choose what you like, and Please report back. My choice is a Losmandy mount, and a Gemini 2 controller.
As always, your mileage may vary.
But saying one will burn out if stalled, is not in fact true.
Interesting discussion!
Draw folks to "New! and Improved!"
But a stepper, even at a tremendously low gearing, is still ticking the motion.
Where a servo can be smooth in between the steps of a stepper motor.
I use a Stepper Motor to drive my focuser. It works great and can go back to steps that were in focus at a previous time and temperature, and all the variables we must deal with.
Then I still have to fish around to get what my eyes think are the focus of the moment. But I have seen where one is off that way, but the other appears off the other way.
Something in-between would be just right.
Where all bets are off is when ground vibrations are considered. We are on a bowl of Jello. Or a ball, if you will.
I had the opportunity to work with Seismologists installing equipment back to a seismic pedestal.
Equipment so sensitive it recorded us moving near it, and vibrations from traffic 1/2 mile away. And up to The Big One that never has shown up.
Lots of options! Choose what you like, and Please report back. My choice is a Losmandy mount, and a Gemini 2 controller.
As always, your mileage may vary.
But saying one will burn out if stalled, is not in fact true.
Interesting discussion!
- SonnyE
- Interdicted
- Articles: 0
- Posts: 52
- Joined: Wed Jan 29, 2020 4:08 am
- 4
- Status:
Offline
Re: PMC-Eight GoTo or Gemini?
Thank You Graeme!Graeme1858 wrote: ↑Thu Mar 05, 2020 11:22 pm
It takes 6.25 x 10 ^18 electrons (625, followed by 16 zeros) passing a point with 1 volt of pressure per second to equal 1 amp of current.
Regards
Graeme
At the time the College Professor stated that, I raised my hand.
I told him that when I needed to know the currant in a circuit, I used a snap-on ammeter.
It fairly stopped him dead in his tracks. My boss and my coworkers were all well seasoned electrical personnel.
And our boss who had arranged this semester in base electrical theory did not know it would be that basic.
Once the Professor knew that, he could help us much better. And we all gained some knowledge.
I can say in all my years, I've seen some things. I ran towards, when others ran away.
But I can say I've never seen an electron, and never counted any individually.
If the new accepted total is 16 zeros, I stand corrected.
But if need be, I still have a clamp on Amprobe in my bag of tricks. (For AC currant)
- Graeme1858
- Co-Administrator
- Articles: 1
- Posts: 7453
- Joined: Mon Jun 24, 2019 7:16 pm
- 4
- Location: North Kent, UK
- Status:
Offline
-
TSS Awards Badges
TSS Photo of the Day
I Broke The Forum.
Re: PMC-Eight GoTo or Gemini?
It's not a new accepted total. 6.25 x 10 ^18 is 625 followed by 16 zeros, it always has been.
I'll be using one of those clamp on ammeters tomorrow night to measure traction current on the Croydon Tram supply!
Regards
Graeme
______________________________________________
Celestron 9.25 f10 SCT, f6.3FR, CGX mount.
ASI1600MM Pro, ASI294MC Pro, ASI224MC
ZWO EFW, ZWO OAG, ASI220MM Mini.
APM 11x70 ED APO Binoculars.
https://www.averywayobservatory.co.uk/
Celestron 9.25 f10 SCT, f6.3FR, CGX mount.
ASI1600MM Pro, ASI294MC Pro, ASI224MC
ZWO EFW, ZWO OAG, ASI220MM Mini.
APM 11x70 ED APO Binoculars.
https://www.averywayobservatory.co.uk/
- SkyHiker
- Local Group Ambassador
- Articles: 0
- Posts: 2293
- Joined: Sat May 11, 2019 8:40 pm
- 4
- Location: Santa Barbara, CA
- Status:
Offline
-
TSS Photo of the Day
TSS Awards Badges
Re: PMC-Eight GoTo or Gemini?
Maybe Scott meant to say that he does not want to bother with having to implement anti-burn-out systems for the gear that he develops. We don't know the context for sure since this quote was second hand information. If your servo did not burn out once, will it not burn out when it happens 100 times?SonnyE wrote: ↑Thu Mar 05, 2020 6:15 pm "He said that the PMC uses stepper motors, and so if the mount runs into an obstacle that stops the mount from moving the electronics won't burn out.
and that the Gemini 2, which uses server motors, would."
I can't say he did say. Nor can I say he did not say. But the broad brush statement is wrong. Therefore, it is untrue.
Based on my personal experiences, my GM811G HAS "crashed" into itself twice. It stops, shuts down, reboots, and waits for the operator to wake up and pay attention.
It did not burn out.
Overloading is controlled in the drive for the device. NOT in the type of motor used.
I have experience with one type of stepper motor. I built a dual axis autoguided barndoor drive for a 10" Dobsonian using small micro-stepper motors controlled by Arduinos. These 28BYJ-48 motors are a few bucks a piece. The step angle is 5.625 degrees (64 pulses per internal revolution) with a 64-fold internal gear reduction. For one external revolution you need 64x64=4096 steps. The motion got further reduced by mechanical means. I can't recall how many steps per second it takes nominally but I think it was about 1000 Hz or so. At that rate, given the weight of the system and the mechanical gear to move it, the impact of the steps in terms of the final motion being jagged is completely negligible because it is a low-pass system dominated by mechanical errors. I like this stepper motor because it is super easy to use in open loop and I don't have to worry about encoders or feedback control or burn-out. The steppers were blocked several times but they were never damaged.SonnyE wrote: ↑Thu Mar 05, 2020 6:15 pm Further, Stepper motors have just that, steps they operate in. I can give you instances where one step is too much, and one step back is not right either.
I built my own focuser drive from Tekky Daves project. In my case, I have >24,000 steps in the full range of the draw tube of my refractors travel. Each step works out to 0.00123" (123/10,000 of an inch, or 3.1242e-5 meter). Or roughly 1 1/4 thousandths of an inch.
Stepper motors are absolute. This step, or that step. No therebetween.
Servo motors are not. Controlling the voltage and current, a servo can be engineered to stop, or more importantly, not stop, at any of the places a stepper misses. Or to make it clear, a Servo has infinite places it can be brought to. Or it can simply creep through that .00123" distance.
In the case of tracking and guiding, a stepper drive is going to step. I never really thought a 6 second video I made would ever be of value when I made it, but this is a good spot for it in this conversation. An Unguided mount and how it's adjustments affect its motion.
That motion helps to demonstrate why stars can get "bloated" in astrophotography. I used to get horribly bloated stars when I first started out. But, I knew I would get better. And I have over the years.
But this is just one case where the system is only used for tracking and guiding, not for
The point is, it all depends. My AVX uses steppers, my G11 has the originally Celestron based kit with stepper motors (just for tracking and guiding), many other mounts use stepper motors. I presume the companies that make these systems made sure that the steppers don't significantly affect the smooth motion that the mount needs. My AVX ran the scope into the legs several times and it never was a problem. I believe the AVX also has a controller that senses it and turns it off though I am not sure. In my experience, polar alignment, periodic error, mechanical gears, stiction, balance and wind determine the image quality, not the choice between steppers or servos. At least not at the level where I'm at.
That's great.SonnyE wrote: ↑Thu Mar 05, 2020 6:15 pm Oh, and as an aside, my mount, and everything involved, is being run by ASCOM with my "Baby Dell" 2 in 1. I think I'm in heaven. PHD2 is being moved by pulse guiding through ASCOM. I don't know how that works, but I can see the results in my imaging. And it makes me smile.
I don't either and I learned something. Especially Steve's PMC-8 review and the astro-gadget link are useful.
... Henk. 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
- SkyHiker
- Local Group Ambassador
- Articles: 0
- Posts: 2293
- Joined: Sat May 11, 2019 8:40 pm
- 4
- Location: Santa Barbara, CA
- Status:
Offline
-
TSS Photo of the Day
TSS Awards Badges
Re: PMC-Eight GoTo or Gemini?
Thanks Steve! This is an affordable alternative. Right now with my G11S I polar-align first then use the setting circles to get to my target. It works for me but if I get tired of it I may buy this kit and add a laptop or mini PC withsdtopensied wrote: ↑Fri Mar 06, 2020 12:33 am A possible alternative to both the PMC-Eight and the Gemini II...
Haven’t had the guts to pull the trigger and order one yet, but I’ve talked to one person who has it on their G-11 and they’re happy with it. You’ll use EQ-Mod to control it. I’ve ordered other smaller stuff from these folks in the past and have been pleased.
Uses motors and couplers similar to the PMC-Eight.
https://astro-gadget.net/gadgets/contro ... r-losmandy
-Steve
... Henk. 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
- SonnyE
- Interdicted
- Articles: 0
- Posts: 52
- Joined: Wed Jan 29, 2020 4:08 am
- 4
- Status:
Offline
Re: PMC-Eight GoTo or Gemini?
I wasn't going to reply Graeme, because it is highly possible I'm mistaken since the bad memory of that class is ~50 years old. And it is Theory. Just another thing assumed to be true.Graeme1858 wrote: ↑Fri Mar 06, 2020 6:49 pm
It's not a new accepted total. 6.25 x 10 ^18 is 625 followed by 16 zeros, it always has been.
I'll be using one of those clamp on ammeters tomorrow night to measure traction current on the Croydon Tram supply!
Regards
Graeme
And I would think you are familiar with the definition of assume.
But I did think I should come back and let you know that you have obviously mistaken me for someone who cares.
- Graeme1858
- Co-Administrator
- Articles: 1
- Posts: 7453
- Joined: Mon Jun 24, 2019 7:16 pm
- 4
- Location: North Kent, UK
- Status:
Offline
-
TSS Awards Badges
TSS Photo of the Day
I Broke The Forum.
Re: PMC-Eight GoTo or Gemini?
SonnyE
It was not my intention to be a smartass. I thought your 26 zeros was a typo since 16 is the correct figure.
It would be good if you were to tone down the argumentative style of your responses as posted in this topic. We don't behave like that onTSS and we don't tolerate it when new members do.
Anyway, you'll be pleased to know I was able to measure the Tramlink East Croydon substation traction current in the DC track return cables last night. There was a variance which indicates a high resistance joint in one of them.
Regards
Graeme
It was not my intention to be a smartass. I thought your 26 zeros was a typo since 16 is the correct figure.
It would be good if you were to tone down the argumentative style of your responses as posted in this topic. We don't behave like that on
Anyway, you'll be pleased to know I was able to measure the Tramlink East Croydon substation traction current in the DC track return cables last night. There was a variance which indicates a high resistance joint in one of them.
Regards
Graeme
______________________________________________
Celestron 9.25 f10 SCT, f6.3FR, CGX mount.
ASI1600MM Pro, ASI294MC Pro, ASI224MC
ZWO EFW, ZWO OAG, ASI220MM Mini.
APM 11x70 ED APO Binoculars.
https://www.averywayobservatory.co.uk/
Celestron 9.25 f10 SCT, f6.3FR, CGX mount.
ASI1600MM Pro, ASI294MC Pro, ASI224MC
ZWO EFW, ZWO OAG, ASI220MM Mini.
APM 11x70 ED APO Binoculars.
https://www.averywayobservatory.co.uk/
Create an account or sign in to join the discussion
You need to be a member in order to post a reply
Create an account
Not a member? register to join our community
Members can start their own topics & subscribe to topics
It’s free and only takes a minute