Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Is the eq platform as wonderful as the Dobsonian mount?

  • Please log in to reply
65 replies to this topic

#1 stargazer193857

stargazer193857

    Voyager 1

  • *****
  • topic starter
  • Posts: 10,524
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 25 November 2020 - 01:09 PM

Decades ago, 4-10" Newtonians rode on eq mounts. And they were heavy and hard to set up. Then Dobson invented the Dobsonian mount, paving the way for easier bigger aperture.

But astrophotographers really need to track the state. Go-to mounts don't rotate the tube, and are heavy too. So many still use 80mm refractors on eq mounts.

But I keep reading about astrophotographers wanting 10-12+" aperture, often stuck at 8" f5, or spending $$ on f3 and carbon fiber.

As a visual user, tracking planets at 300x is disappointing. So is trying to show stuff to a line of people.


Are equatorial platforms the next step past the Dobsonian mount? Now astrophotographers can take 5-10 minute shots in a 20" scope without needing an expensive or heavy mount.

Who invented them?
Are they patented?

#2 TOMDEY

TOMDEY

    Cosmos

  • *****
  • Posts: 8,451
  • Joined: 10 Feb 2014
  • Loc: Springwater, NY

Posted 25 November 2020 - 02:01 PM

They've been around almost as long as the Dobsonians. In theory, they are wonderful... but in practice, they are still quite deficient for Deep Sky Imagery.    Tom


  • jim kuhns, Starsareus and stargazer193857 like this

#3 tjschultz2011

tjschultz2011

    Messenger

  • *****
  • Posts: 400
  • Joined: 02 Feb 2019
  • Loc: Eldorado, WI

Posted 25 November 2020 - 02:20 PM

I've owned one before and it worked pretty well but neither an EQ platform or an ALT/AZ tracking system can manage 5-10 minute shots. They can keep the target in frame for that long but don't hold it still enough in the frame to image. I've been able to manage 20 second shots with my ServoCAT ALT/AZ setup on my 17.5" dob but I usually stick with 10 or 15 seconds so that I can keep most of my subs instead of having to throw away 1/3 or 1/2 of them. But I've been finding that even 10 or 15 second subs are enough to create decent images with that much aperture. Here's my latest shot, M42, with only 5 minutes worth of exposure. 

 

M42 Final 2.jpg


  • kfiscus, Bomber Bob, Elroy and 3 others like this

#4 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 89,193
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 25 November 2020 - 04:03 PM

There's a thread about imaging with a 25 inch F/5 Obsession on a Tom O. Dual Axis platform. 

 

https://www.cloudyni...m/#entry8530321

 

I have a dual axis Tom O Platform. It's very solid, tracks accurately and retains the essential Dobsonian nature, it's a Dob that tracks.

 

JStar on EQ Platform 1.jpg

 

But I found I preferred manual tracking... old habits die hard.

 

Jon


  • Marko2, Bomber Bob, stargazer193857 and 2 others like this

#5 seasparky89

seasparky89

    Ranger 4

  • *****
  • Posts: 387
  • Joined: 09 Feb 2009
  • Loc: Springfield, VA

Posted 26 November 2020 - 10:01 AM

I have two platform for my dobs.  They work very well for me.  And at my club starparties, they really help.  My scopes will track for nearly an hour before a reset is needed.  And my Intelliscope and Argo Navis systems play nicely with the platforms.  I wish there were more vendors out there to increase availability and keep the prices competitive, but I suppose the platforms are not high demand items.  Now, if the manufacturers included the platform in the design of a new line of dobs, and considering the increased interest in imaging/EAA, IMHO, there would be a significant uptick in sales.


  • astrophile likes this

#6 Second Time Around

Second Time Around

    Messenger

  • -----
  • Posts: 466
  • Joined: 08 Oct 2019
  • Loc: Rural Kent, UK

Posted 26 November 2020 - 11:23 AM

Now, if the manufacturers included the platform in the design of a new line of dobs, and considering the increased interest in imaging/EAA, IMHO, there would be a significant uptick in sales.

Sumerian in the Netherlands do an equatorial platform to go with their Dobs or stand alone.  For a 10 inch the cost is under 400 EUR.



#7 stargazer193857

stargazer193857

    Voyager 1

  • *****
  • topic starter
  • Posts: 10,524
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 26 November 2020 - 12:30 PM

Orion sells a stand to get done up to a standing height. If someone is spending $99+ for that, why not get an equatorial platform too?

They are only good enough for astrophotography at their designed latitude, but they should be excellent for visusl planet viewing anywhere in the US. Who cares if a planet drifts out of view every 5 minutes? Better than 30 seconds.

#8 Second Time Around

Second Time Around

    Messenger

  • -----
  • Posts: 466
  • Joined: 08 Oct 2019
  • Loc: Rural Kent, UK

Posted 26 November 2020 - 01:02 PM

Something else I'd add is that if you have an equatorial platform you may feel that you don't need extra wide angle high power eyepieces to keep objects in the FOV for longer. This could save a lot of money and totally cover the cost of the equatorial platform.

#9 Pezdragon

Pezdragon

    Ranger 4

  • *****
  • Posts: 355
  • Joined: 10 Jun 2013
  • Loc: Bay Area, Ca.

Posted 26 November 2020 - 01:43 PM

As to who invented them I recall a article in Sky and Telescope back in the late 70’s written by Adrien Poncet describing his building such a device. I think improvements have since been made to his design. I don’t know if it was patented.



#10 astrophile

astrophile

    Viking 1

  • *****
  • Posts: 741
  • Joined: 30 Jun 2013
  • Loc: NoVA Yellow Zone

Posted 26 November 2020 - 06:13 PM

A Dob without an eq platform is like...a turkey sandwich without cranberry sauce.  Good, but not nearly as enjoyable or beneficial.  (Especially for outreach.)

 

But this is from an inveterate platform-o-phile, three of whose four dobs are configured permanently for platform use.  This includes a Starmaster 16 purchased secondhand with full GoTo, but for which I had Ryan of New Moon Telescopes custom build a stripped-down rocker box in order to use it primarily atop a platform.  Yes, I'm nuts about eq platforms.  My only scope still attached to a groundboard is an "over performing 8" (fabulous home-ground mirror by Ron King) for one-trip grab-n-go instant setup.  Hand-tracking that at 300x (in the vanishingly rare seeing that allows for such) is eminently doable but not great fun. 

 

I will say I have never attempted astro-photography with any kind of setup, dob or otherwise.


  • kfiscus likes this

#11 StephenW

StephenW

    Apollo

  • -----
  • Posts: 1,308
  • Joined: 04 Feb 2005
  • Loc: San Jose, CA

Posted 26 November 2020 - 07:58 PM

Well you can of course have tracking without a platform. My 18" Starmaster keeps targets centered at high mag without any problems. Helpful for me when planet viewing or for general outreach.

The only benefit an EQ platform would add would be to eliminate field rotation, but for visual observing (or even planetary imaging) that's generally not an issue...

Ok, so back to my turkey and cranberry dinner... ;)

#12 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 89,193
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 26 November 2020 - 08:34 PM

Well you can of course have tracking without a platform. My 18" Starmaster keeps targets centered at high mag without any problems. Helpful for me when planet viewing or for general outreach.

The only benefit an EQ platform would add would be to eliminate field rotation, but for visual observing (or even planetary imaging) that's generally not an issue...

Ok, so back to my turkey and cranberry dinner... wink.gif

 

One benefit of an EQ Platform:

 

I own five Dobs. One platform works with 4 of them.  There's no modifications necessary to the scopes required for tracking.

 

6344666-10 inch Dob on EQ platform.jpg
 
JStar on EQ Platform 1.jpg
 

That's a big plus..

 

Jon


  • Bomber Bob and stargazer193857 like this

#13 sanbai

sanbai

    Viking 1

  • *****
  • Posts: 746
  • Joined: 18 May 2019
  • Loc: Baton Rouge, LA

Posted 26 November 2020 - 10:20 PM

One benefit of an EQ Platform:

I own five Dobs. One platform works with 4 of them. There's no modifications necessary to the scopes required for tracking.





That's a big plus..

Jon

Even for a single dob. Something like ServoCAT costs north of $3,000. A platform is usually under that price. In the other hand, they only work in a small latitude range and may not work that well with DSC (?).

I'll consider the summerian platform when I go back to Germany for my NMT 12.5" I have on order. First I want to experience full manual movements and DSC. Baton Rouge is too south for a germany-tuned platform, so it's not an option at this moment.
  • Jon Isaacs likes this

#14 osbourne one-nil

osbourne one-nil

    Surveyor 1

  • -----
  • Moderators
  • Posts: 1,965
  • Joined: 03 Jul 2006
  • Loc: Cumbria, England 54.5ºN 2.5ºW

Posted 27 November 2020 - 02:22 AM

I've often been tempted by one of these, purely for visual, but I still can't quite get my head around how they work. However, there are a lot of things out there that I don't understand but still work perfectly, so that doesn't put me off. The thought of combining one with a stand to raise everything off the floor is appealing to me.  


  • Jon Isaacs likes this

#15 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 89,193
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 27 November 2020 - 07:37 AM

I've often been tempted by one of these, purely for visual, but I still can't quite get my head around how they work. However, there are a lot of things out there that I don't understand but still work perfectly, so that doesn't put me off. The thought of combining one with a stand to raise everything off the floor is appealing to me.  

waytogo.gif

 

I have a basic understanding of how they work, I don't think I could design one without doing some research.  And sometimes I have had to look at a picture to make sure I know which end points north, smile.gif

 

This is my understanding:

 

Imagine you had a large cone whose central axis was pointing at the polar axis and riding on bearings.  If you were sitting on the cone, if it rotated at sideral rate (23hours 46 minutes), then the sky would not move, it would track as an equatorial mount.

 

If you now cut that cone off so it has flat surface, that flat surface also tracks.  

 

That's my understanding of how an equatorial platform works. 

 

Jon


  • Scott in NC, osbourne one-nil and sanbai like this

#16 stargazer193857

stargazer193857

    Voyager 1

  • *****
  • topic starter
  • Posts: 10,524
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 27 November 2020 - 08:31 AM

I understand how they work, though it took some extra thinking.

They can work at many latitudes as long as you are provided different arcs that can be swapped out or ordered before a trip. Making the arcs interchangable would be easy.


My other concern is whether slewing while it is running would damage anything. Altitude should be fine. Azimuth slew has me concerned.
... Someone posted that the drive motor is on the north bearing. No risk of damage there. Only need to disengage when resetting. Then re-acquire.

Edited by stargazer193857, 27 November 2020 - 10:46 AM.


#17 junomike

junomike

    ISS

  • *****
  • Moderators
  • Posts: 20,750
  • Joined: 07 Sep 2009
  • Loc: Ontario

Posted 27 November 2020 - 08:50 AM

Never owned one (Platform) but have used/viewed through a Dob using one. 

initial Polar alignment  and Resetting after 60 - 90 min is somewhat of a pain (IMO), but better than nothing.



#18 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 89,193
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 27 November 2020 - 08:53 AM

They can work at many latitudes as long as you are provided different arcs that can be swapped out or ordered before a trip. Making the arcs interchangable would be easy.

 

Not so easy.  The angle of the south bearing depends on the latitude.  

 

These are precision devices.  

 

My other concern is whether slewing while it is running would damage anything. Altitude should be fine. Azimuth slew has me concerned.

 

 

 Why would you slew an EQ mount in Altitude and Azimuth?  They slew in RA and quasi-declination.  To slew in alt-az, you'd need another set of motors and drives. 

 

Jon



#19 Jon Isaacs

Jon Isaacs

    ISS

  • *****
  • Posts: 89,193
  • Joined: 16 Jun 2004
  • Loc: San Diego and Boulevard, CA

Posted 27 November 2020 - 09:03 AM

Never owned one (Platform) but have used/viewed through a Dob using one. 

initial Polar alignment  and Resetting after 60 - 90 min is somewhat of a pain (IMO), but better than nothing.

 

That probably depends on the platform.  With the Tom O. platform, you just grab the handle and pull.  It takes maybe 5 seconds.  Then you have to reacquire the target but the actual resetting is super easy.  

 

Jstar on EQ Platform reset handle.jpg

 

I am not sure how one resets other platforms, the Tom O. platforms use steel against brass for the northern axis which is where the drive is and roller/ball bearings on the southern axis.  

 

Jon


  • stargazer193857 likes this

#20 Chucky

Chucky

    Apollo

  • *****
  • Posts: 1,191
  • Joined: 16 Apr 2010

Posted 27 November 2020 - 09:20 AM

It boils down pretty simply for me.  I don't always use my Tom O. platform, but when I do I ALWAYS-ALWAYS get a better observing experience.  I see more by taking my time.....use more eyepieces/filters.  Overall more relaxed.  Much reduced time and effort to keep object centered.

 

I use this platform on 3 tubed dobs.  The platform acts as the groundboard on all 3 scopes.  I can easily switch out pad size/placement into brass threaded inserts.  The center pin has a nylon insert allowing for easy/fast setup with the rocker box-encoder.

 

For plaform viewing, this is about as good as it gets.

Attached Thumbnails

  • Platform.jpg

Edited by Chucky, 27 November 2020 - 09:40 AM.

  • The Ardent, astrophile, Bomber Bob and 1 other like this

#21 sw196060

sw196060

    Messenger

  • *****
  • Posts: 487
  • Joined: 16 Apr 2020

Posted 27 November 2020 - 10:00 AM

Chucky,

  That wooden platform looks nice.   Who made it?  Is that a Tom O. platform?


  • stargazer193857 likes this

#22 stargazer193857

stargazer193857

    Voyager 1

  • *****
  • topic starter
  • Posts: 10,524
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 27 November 2020 - 10:32 AM

Not so easy. The angle of the south bearing depends on the latitude.

These are precision devices.


Why would you slew an EQ mount in Altitude and Azimuth? They slew in RA and quasi-declination. To slew in alt-az, you'd need another set of motors and drives.

Jon

The south bearing angle can be wedge that's part of the bearing, with bolt holes perpendicular to the mating surface, not tangent to the bearing sides. The north bearung can be a ball and socket. Non issue. As for the rollers, short of them being able to pivot, those two could be interchangeable and paired with their bearing.
The bearing vertical height would not change, though the width would. So the rollers might need to vary their separation distance, although they actually don't since they can engage the bearing anywhere and are best above the platform feet and below the Dobsonian feet. Roller bearings, unlike pads, accommodate several angles automatically at the same separation distance.


As for alt az, because that is what a dob does and is simpler. The eq platform was never intended to sleep in RA and declinations. It just tracks. ... Ah... I mean manual slewing and motor tracking. Best of all worlds. Did you mean that an eq platform can slew? I doubt it, not would I want that.

Edited by stargazer193857, 27 November 2020 - 11:08 AM.


#23 stargazer193857

stargazer193857

    Voyager 1

  • *****
  • topic starter
  • Posts: 10,524
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 27 November 2020 - 10:40 AM

Never owned one (Platform) but have used/viewed through a Dob using one.
initial Polar alignment and Resetting after 60 - 90 min is somewhat of a pain (IMO), but better than nothing.

For astrophotography, polar alignment needs to be more accurate, and is limited by the bearing exactly matching the latitude. For visual, one could point it generally north aiming from the hip and get dramatically lengthened planetary drift times.

Edited by stargazer193857, 27 November 2020 - 11:08 AM.


#24 Chucky

Chucky

    Apollo

  • *****
  • Posts: 1,191
  • Joined: 16 Apr 2010

Posted 27 November 2020 - 11:31 AM

Yes

(( That wooden platform looks nice. Who made it? Is that a Tom O. platform? ))

#25 stargazer193857

stargazer193857

    Voyager 1

  • *****
  • topic starter
  • Posts: 10,524
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 27 November 2020 - 12:22 PM

Do eq platforms need much smaller motors and batteries than go-to?

If they cost $400+, I wonder why more scope makes are not building them. Maybe the buyer base is unaware of the benefits? The main drawback I see is the extra height if the scope was otherwise already the perfect height. I also wonder how well they handle vibrations.


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics