57 replies to this topic

[Speedy1985]

So I'm contemplating getting a larger 16-18" dob at some point and I've been thinking about options for being able to track objects. I'd like to have some capability in order to be able to get some better cell phone photos both with regular glass and when using night vision. I'm torn between built in tracking like Servocat or a separate equatorial platform. Some of the things I've thought of include:

 

Both require a power supply, so that's a wash.

Cost wise, a good eq platform can be a fair bit cheaper if you get a good one from someone like Optical Ed Jones.

The platform is another piece of equipment to move.  

 

I'm not sure if I've hit on all of the nuances of each option, so for those that have used one or the other, or had both, what are your likes and dislikes of each?

[The Ardent]

If something goes wrong with the Servocat, who’s gonna fix it?

[Speedy1985]

If something goes wrong with the Servocat, who’s gonna fix it?

I know Servocat is not being made any more so not available on anything new, that was just one example of a tracking system. I know there are others systems coming, so I just used that name because it is the most widely known. 

[Jon Isaacs]

One advantage of a tracking platform is that it can be used with multiple scopes without much difficulty.

 

Do you know who is making aftermarket GOTO?

 

Jon

[Speedy1985]

One advantage of a tracking platform is that it can be used with multiple scopes without much difficulty.

 

Do you know who is making aftermarket GOTO?

 

Jon

That's true Jon.

 

I started another thread yesterday about GOTO/tracking builders. It seems that Argo Navis may be coming out with something as well as Nexus. But who knows what the timeline may be with the supply chain issues.

[Woj2007]

Have you considered Romer Optics go-to?

https://romer-optics...a-fee-dobsonian

https://cdn.shopify....df?v=1666922573

[Speedy1985]

Have you considered Romer Optics go-to?

https://romer-optics...a-fee-dobsonian

https://cdn.shopify....df?v=1666922573

Those are kits to upgrade the mass produced dobs, which I currently have. If I move to a larger size, it will be to a premium brand as it would likely be my lifetime scope.

[wrvond]

It seems you (or this thread) are moving towards GoTo and leaving simple tracking behind, in which case the EQ platform loses out. I've had GoTo and now I've got push-to with an EQ platform. GoTo is inherently more complicated than an EQ platform. Any tracking or GoTo system that moves the scope in azimuth and altitude is going to have two motors and accompanying wiring, while a platform generally has a single motor (I think Ed Jones uses two). An advantage of GoTo/tracking is that the scope will track the target for hours on end if your alignment is up to snuff while a platform is only good for 90 minutes before it needs to be reset. This pretty much exceeds the attention span of most people though.

 

GoTo/tracking is built in to the Dob, so the weight does go up appreciably while a platform can be carried separately or left at home if desired.

[Jon Isaacs]

Those are kits to upgrade the mass produced dobs, which I currently have. If I move to a larger size, it will be to a premium brand as it would likely be my lifetime scope.

 

It's possible the Romer system could adapted to a non-commercial Dob..

 

I have a Tom O dual axis aluminum platform but I prefer manual tracking.. 

 

Jon

[CowTipton]

My scope is only 14" with the Synscan system, just below your size threshold.

Here is what I figure:

 

Pros:

 

-Goto and tracking are built into the system

-Alt/az is easy and intuitive

-Alignment is simple on two stars, PAE can make it more precise after initial alignment.

-Can use NINA to platesolve/automate/re-center/mosaic/etc when taking photos

 

Cons:

 

-Base is heavy

-For DSO photography, short single exposures only. 

 

 

 

For an EQ platform:

 

Pros:

-You can use it with different scopes

-Weight is easier to manage

-For DSO photos you can take much longer single exposures

-Smoother tracking  (some even have guiding ports)

 

Cons:

-It's a separate piece of equipment to set up

-No goto

-You must polar align  (precisely if doing any DSO AP with it otherwise you're stuck doing short exposures and lose the advantage over alt/az)

-Cannot automate your AP session

-Must reset scope and re-find target after an hour or so

 

In an ideal world I'd have both but for now I'm quite happy with alt/az goto and tracking

[Peter Natscher]

So I'm contemplating getting a larger 16-18" dob at some point and I've been thinking about options for being able to track objects. I'd like to have some capability in order to be able to get some better cell phone photos both with regular glass and when using night vision. I'm torn between built in tracking like Servocat or a separate equatorial platform. Some of the things I've thought of include:

 

Both require a power supply, so that's a wash.

Cost wise, a good eq platform can be a fair bit cheaper if you get a good one from someone like Optical Ed Jones.

The platform is another piece of equipment to move.  

 

I'm not sure if I've hit on all of the nuances of each option, so for those that have used one or the other, or had both, what are your likes and dislikes of each?

I've just received a new Tom Osypowski eq platform for my manual 12.5" Dob.  This is my first experience with a eq platform.  I've always observed with tracking Dobs, most with Servocat. I'm still testing the platform out on this Dob having only observed with it for three nights. So far, I like what it does with this telescope for my observing. Objects now stay centered in my eyepiece at all my chosen eyepiece powers. The DEC and RA movement is just as smooth as it was before in its original state with the ground board attached.  I chose the dual-axis model giving me more Dob movement control using a wired hand box with N-S-E-W directional buttons for DEC/RA fine object centering at the eyepiece.  Observing at 350X, the tracking is dead on for 60 minues plus.  When the 12.5" Dob was made, I though that I would be satisfied with a push-to scope, Nexus, and encoders. I've always had driven/tracking Dobs for 25 years and totally missed having this on my most recent 12.5" Dob.  In its untracking state using 200X and higher, the viewed objects were racing to fast across my eyepiece FOV and this was disatisfying. I was losing 50% of my observing time recentering the views by hand. My other Dob, a 16", has ServoCat installed with Nexus Pro and I'm delighted with it, but it is a more complicated system. True, SC is built in keeps the eyepiece height a few inches lower and isn't an added piece of equipment to set up but it's another set of electronic parts that have their own issues like not operating properly in the middle of an observing session and wasting precious observing time. The eq platform uses very little 12V power, internally or externally, for two small DC motors.

 

My newest 12.5" Dob (in photo) was built with no tracking thoughts in mind and I regrettied that after initially observing with it. Most of my observing is done at mid-to-high powers (200X-400X) without tracking, a lot of discriminating observing can't be done with eyepiece objects moving across the FOV so quickly.  I also sketch a lot and that makes it almost mandatory to have tracking as my hands are preoccupied with holding a pencil and sketch board, no free hand available to push a scope with. Using my 12.5" Dob with the eq platform required me to remove the ground board so that the rocker box now pivots directly on the top piece of the eq platform. Total height with eq platform underneath changed things putting the eyepiece 5" higher versus what it had with the original ground board. Now, the most vertical position of the Dob locates the eyepiece 2" above my eyes.  That's not much or an issue since 90% of my chosen sky objects for a night lie more than 10° from directly from vertical in the sky and so the telescope can point a little lower which puts the eyepiece lower.  Bottom line, the Dob is still a ladderless telescope, for my 70" eye height.

 

The benefit of a tracking platform is that you can hand push the telescope around the sky and not interfere with its active tracking. No drive clutches to engage/disengage as with ServoCat.  Nothing is locked in. Total freedom of telescope movement as if it was still manual, push-to.  My Nexus Pro DSC also works well on the telescope with the eq platform. Nexus Pro has a tracking timer function in its Alignment menu to keep pace with the tracking, for one complete track of the platform of 70-80 minutes. Nexus needs the same vertical + two-star alignment procedure on the platform as it does with a standard ground board Dob. Nexus does require a new re-alignment procedure with each new tracking sequence of the platform, but that only take a few minutes each time.

 

Photo: 12.5" f/5.5 Dob with Tom Osypowsky Dual-Axis Equatorial Platform.

 

Attached Thumbnails

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[Speedy1985]

It seems you (or this thread) are moving towards GoTo and leaving simple tracking behind, in which case the EQ platform loses out. I've had GoTo and now I've got push-to with an EQ platform. GoTo is inherently more complicated than an EQ platform. Any tracking or GoTo system that moves the scope in azimuth and altitude is going to have two motors and accompanying wiring, while a platform generally has a single motor (I think Ed Jones uses two). An advantage of GoTo/tracking is that the scope will track the target for hours on end if your alignment is up to snuff while a platform is only good for 90 minutes before it needs to be reset. This pretty much exceeds the attention span of most people though.

 

GoTo/tracking is built in to the Dob, so the weight does go up appreciably while a platform can be carried separately or left at home if desired.

Thanks for the insight Warren. I have push to right now with the Nexus II on my dob(as well as my frac) and I like it a lot. The allure of the goto system is having it do the work to find and keep an object in the "window". I know it will track longer with a good alignment, but I can't see me spending that much time on a single target. So does that give the goto/tracking the advantage over a platform?

 

It's possible the Romer system could adapted to a non-commercial Dob..

 

I have a Tom O dual axis aluminum platform but I prefer manual tracking.. 

 

Jon

This is true Jon.

The Tom O platforms are nice, but they cost about the same as what a good goto tracking system would cost, based on looking at past costs.

 

My scope is only 14" with the Synscan system, just below your size threshold.

Here is what I figure:

 

Pros:

 

-Goto and tracking are built into the system

-Alt/az is easy and intuitive

-Alignment is simple on two stars, PAE can make it more precise after initial alignment.

-Can use NINA to platesolve/automate/re-center/mosaic/etc when taking photos

 

Cons:

 

-Base is heavy Do you think this would more so with commercially available dobs who are already pretty heavy?

-For DSO photography, short single exposures only. If the system is tracking the object, why? Isn't that the reason for tracking, so that you can do longer exposures? 

 

 

 

For an EQ platform:

 

Pros:

-You can use it with different scopes

-Weight is easier to manage 

-For DSO photos you can take much longer single exposures

-Smoother tracking  (some even have guiding ports)

 

Cons:

-It's a separate piece of equipment to set up

-No goto

-You must polar align  (precisely if doing any DSO AP with it otherwise you're stuck doing short exposures and lose the advantage over alt/az) I've never had to do this, so I'm not sure how difficult it would be

-Cannot automate your AP session

-Must reset scope and re-find target after an hour or so

 

In an ideal world I'd have both but for now I'm quite happy with alt/az goto and tracking

Thank you Mike. 

 

A couple of thoughts in red

[Peter Natscher]

So I'm contemplating getting a larger 16-18" dob at some point and I've been thinking about options for being able to track objects. I'd like to have some capability in order to be able to get some better cell phone photos both with regular glass and when using night vision. I'm torn between built in tracking like Servocat or a separate equatorial platform. Some of the things I've thought of include:

 

Both require a power supply, so that's a wash.

Cost wise, a good eq platform can be a fair bit cheaper if you get a good one from someone like Optical Ed Jones.

The platform is another piece of equipment to move.  

 

I'm not sure if I've hit on all of the nuances of each option, so for those that have used one or the other, or had both, what are your likes and dislikes of each?

A internal tracking system for a Dob, like ServoCat, requires the space in the rocker box for the electronics and drives. If you have a Dob you are already using but without tracking and without the space to install SC, then SC can't be chosen. A eq platform is the answer.

 

The advantage of ServoCat GoTo function versus unpowered hand pushing is that the SC drives point the Dob to the chosen object as directed by a DSC i.e. Nexus versus you hand pushing to an object while watching the DSC display of that chosen object to find it.  The DSC is the brains with this.  Either way, you can watch the slewing of the Dob on the Nexus display while the object is being brought to and centered at the eyepiece.  Actually, hand pushing to center an object in the eyepiece is faster and quieter, and uses less of your DC battery power during the observing session. I have SC installed on my 16" Dob along with Nexus Pro and at most observing sessions I choose to disengage the SC drives and hand point the Dob to the object while watching the Alt-Az numbers on the Nexus display until the numbers for the object are zero'ed out and object centered in eyepiece. I then re-engage the SC drives for Dob tracking to take place. The Nexus DSC is doing all the object finding. Whether you use the SC drive's GoTo function or hand push to an object is secondary to that.  I find hand pointing my Dob's more expedient than usijg SC's GoTo drives. I personally value the ServoCat on my 16" Dob for its tracking ability and not it's GoTo.  Yes, you can keep the drives engaged with SC all night and GoTo to your heart's content.  That's probably a good choice for outreach and showing many deep sky objects to lines of people waiting to have a look. Observing by myself, I end up engaging and disengaing the drives back and forth with each object to hand push between engaging the drives for tracking.  It's extra work but I find the result more satisfying, as I'm still looking a paper star charts and manually doing something with my telescope.  Keeps me functioning better at 72.
 

Edited by Peter Natscher, 24 January 2023 - 06:16 PM.

[a__l]

Tilt on the EQ platform. The higher the latitude, the greater the tilt. Dobson's mirror cell is usually made for tilt=0.
If you have a thin mirror, additional astigmatism may appear.

[Tangerman]

I believe Tom O also builds dobs using a more unique tracking system than either servocat or his equatorial platforms. Unfortunately, I know little about it. I'd recommend asking him about its capabilities.

[Peter Natscher]

Tilt on the EQ platform. The higher the latitude, the greater the tilt. Dobson's mirror cell is usually made for tilt=0.
If you have a thin mirror, additional astigmatism may appear.

That might be true for mirrors on sling mounts but my Dobs use edge supported wiffle tree mounts that are not affected by the max 10° telescope angle a eq plaform incurs.

 

I observe at 36° N.  In a eq platform, the rocker box remains level to the ground in it's N-S DEC axis.  What changes on this axis is its E-W tracking angle as it tracks the sky. The angle you refer to is the tracking angle as the Dob swings through its tracking from beginning to end, 10° angled east at start and ending 10° west at its end track, a total of E-W 20° angle movement.  Yes, a Dob's mirror requires a superior mount with good edge support as it's being angled with that amount of degrees movement.  OTOH, I personally know of two Obsesion 18" owners with Obsession 'sling' mirror mounts who use eq platforms withn them and with no issues. Their mirror alignment remains adequate.

Edited by Peter Natscher, 24 January 2023 - 06:33 PM.

[Speedy1985]

I've just received a new Tom Osypowski eq platform for my manual 12.5" Dob.  This is my first experience with a eq platform.  I've always observed with tracking Dobs, most with Servocat. I'm still testing the platform out on this Dob having only observed with it for three nights. So far, I like what it does with this telescope for my observing. Objects now stay centered in my eyepiece at all my chosen eyepiece powers. The DEC and RA movement is just as smooth as it was before in its original state with the ground board attached.  I chose the dual-axis model giving me more Dob movement control using a wired hand box with N-S-E-W directional buttons for DEC/RA fine object centering at the eyepiece.  Observing at 350X, the tracking is dead on for 60 minues plus.  When the 12.5" Dob was made, I though that I would be satisfied with a push-to scope, Nexus, and encoders. I've always had driven/tracking Dobs for 25 years and totally missed having this on my most recent 12.5" Dob.  In its untracking state using 200X and higher, the viewed objects were racing to fast across my eyepiece FOV and this was disatisfying. I was losing 50% of my observing time recentering the views by hand. My other Dob, a 16", has ServoCat installed with Nexus Pro and I'm delighted with it, but it is a more complicated system. True, SC is built in keeps the eyepiece height a few inches lower and isn't an added piece of equipment to set up but it's another set of electronic parts that have their own issues like not operating properly in the middle of an observing session and wasting precious observing time. The eq platform uses very little 12V power, internally or externally, for two small DC motors.

 

My newest 12.5" Dob (in photo) was built with no tracking thoughts in mind and I regrettied that after initially observing with it. Most of my observing is done at mid-to-high powers (200X-400X) without tracking, a lot of discriminating observing can't be done with eyepiece objects moving across the FOV so quickly.  I also sketch a lot and that makes it almost mandatory to have tracking as my hands are preoccupied with holding a pencil and sketch board, no free hand available to push a scope with. Using my 12.5" Dob with the eq platform required me to remove the ground board so that the rocker box now pivots directly on the top piece of the eq platform. Total height with eq platform underneath changed things putting the eyepiece 5" higher versus what it had with the original ground board. Now, the most vertical position of the Dob locates the eyepiece 2" above my eyes.  That's not much or an issue since 90% of my chosen sky objects for a night lie more than 10° from directly from vertical in the sky and so the telescope can point a little lower which puts the eyepiece lower.  Bottom line, the Dob is still a ladderless telescope, for my 70" eye height.

 

The benefit of a tracking platform is that you can hand push the telescope around the sky and not interfere with its active tracking. No drive clutches to engage/disengage as with ServoCat.  Nothing is locked in. Total freedom of telescope movement as if it was still manual, push-to.  My Nexus Pro DSC also works well on the telescope with the eq platform. Nexus Pro has a tracking timer function in its Alignment menu to keep pace with the tracking, for one complete track of the platform of 70-80 minutes. Nexus needs the same vertical + two-star alignment procedure on the platform as it does with a standard ground board Dob. Nexus does require a new re-alignment procedure with each new tracking sequence of the platform, but that only take a few minutes each time.

 

Photo: 12.5" f/5.5 Dob with Tom Osypowsky Dual-Axis Equatorial Platform.

This is all great info and gives me plenty to ponder!

[Speedy1985]

A internal tracking system for a Dob, like ServoCat, requires the space in the rocker box for the electronics and drives. If you have a Dob you are already using but without tracking and without the space to install SC, then SC can't be chosen. A eq platform is the answer.

 

The advantage of ServoCat GoTo function versus unpowered hand pushing is that the SC drives point the Dob to the chosen object as directed by a DSC i.e. Nexus versus you hand pushing to an object while watching the DSC display of that chosen object to find it.  The DSC is the brains with this.  Either way, you can watch the slewing of the Dob on the Nexus display while the object is being brought to and centered at the eyepiece.  Actually, hand pushing to center an object in the eyepiece is faster and quieter, and uses less of your DC battery power during the observing session. I have SC installed on my 16" Dob along with Nexus Pro and at most observing sessions I choose to disengage the SC drives and hand point the Dob to the object while watching the Alt-Az numbers on the Nexus display until the numbers for the object are zero'ed out and object centered in eyepiece. I then re-engage the SC drives for Dob tracking to take place. The Nexus DSC is doing all the object finding. Whether you use the SC drive's GoTo function or hand push to an object is secondary to that.  I find hand pointing my Dob's more expedient than usijg SC's GoTo drives. I personally value the ServoCat on my 16" Dob for its tracking ability and not it's GoTo.  Yes, you can keep the drives engaged with SC all night and GoTo to your heart's content.  That's probably a good choice for outreach and showing many deep sky objects to lines of people waiting to have a look. Observing by myself, I end up engaging and disengaing the drives back and forth with each object to hand push between engaging the drives for tracking.  It's extra work but I find the result more satisfying, as I'm still looking a paper star charts and manually doing something with my telescope.  Keeps me functioning better at 72.
 

If I buy used, I'll have to decide up front if goto/tracking is something I want. I don't want to have to retrofit a system later.

 

I think I like the idea of having the option to disengage the clutches to use it as push to, then re-engage. Especially when it comes to saving some battery power. And how much extra work is it really, a few seconds? 

[a__l]

That might be true for mirrors on sling mounts but my Dobs use edge supported wiffle tree mounts that are not affected by the max 10° telescope angle a eq plaform incurs.

 

 

I think for Obsesion this is not good. Perhaps for others. If the location is correct, the OP will have a larger angle.

[Peter Natscher]

If I buy used, I'll have to decide up front if goto/tracking is something I want. I don't want to have to retrofit a system later.

 

I think I like the idea of having the option to disengage the clutches to use it as push to, then re-engage. Especially when it comes to saving some battery power. And how much extra work is it really, a few seconds? 

Sure!  The DSC is still functioning and keeping track of the sky's objects because the encoders are functioning whether Servocat is operational or not.

[a__l]

I think I like the idea of having the option to disengage the clutches to use it as push to, then re-engage. Especially when it comes to saving some battery power. And how much extra work is it really, a few seconds? 

It makes no sense to get an additional headache because of this. Usually used to work with or without motors. When you turn on/off the motors, you are almost guaranteed to move the telescope, especially at high magnifications.

 

I will add. If we consider ServoCat.

Edited by a__l, 24 January 2023 - 07:07 PM.

[a__l]

Yes, even a nuance. The cable for Az has a limited resource. Especially when the springs tension is high. If you pull it often, you will have to repair it often. For this, some spare parts are needed.

Edited by a__l, 24 January 2023 - 07:13 PM.

[Peter Natscher]

I think for Obsesion this is not good. Perhaps for others. If the location is correct, the OP will have a larger angle.

There is no difference in the angle of the base of the Dob, the angle of its rocker box, no matter what latitude you are observing from.  The differences in each of them custom built for their latitudes lie in the other moving parts of the platform.  Take a look of the different size telescopes on Tom's platforms that are located in different parts of the US at different latitudes.  Their base rocker boxes all appear level in their DEC axis.

 

http://www.equatoria...platforms.shtml

[a__l]

It does not matter. Even 10 degrees can cause the mirror on the belt (cable) to shift. Two consequences, additional collimation and additional astigmatism.

[Peter Natscher]

If something goes wrong with the Servocat, who’s gonna fix it?

Gary Myers at StellarCat is still supporting his ServoCat with services.  He's great with service!  I recently got a replacement part for my ServoCat from him.  Supply chain delays are affecting availability of his inventory.
 

Edited by Peter Natscher, 24 January 2023 - 07:48 PM.