Autoguiding with a G-11 standard mount ?

[nandopg]

Hi Fellows,
I have a good opportunity to buy a second hand G-11S (standard). This mount being standard doesn't have goto capability, although it has a hand control to move the scope. I am afraid to buy this unless I have the following questions answered:

1- Can this standard version be controlled by a planetary program like The Sky X, so that I can sync the mount using a number of stars to calibrate the it ?

2- How does this standard version work as for autoguiding ? Is the connection a standard ST-4 port ?

3- The package available for sale, also has a JMI NGC-MAX. Does this help some in the workflow of pointing to an object for astrophotography ?

Any other comment is more than welcome.

Thanks.
Fernando

[alocky (Andrew lockwood)]

Hi Fernando,
I used a G11s for a couple of years before upgrading it to a Gemini 2.
Your Qs
1. No. It is not a goto system and has no way of knowing where it is pointed - (but q3 suggests you may be able to do something!)
2. The auto guiding is best done using a shoestring GPUSB connected to the hand controller port. This can be put through a splitter so you can have the hand controller connected as well. Any software like PHD will then be able to supply the auto guiding corrections to the mount.
3. Yes. These are digital setting circles and should let you drop any object on the chip. The analogue setting circles that come standard with the mount were usually good enough for me to get something on an Apsc chip at 1100mm focal length.

You may be able to take the output from the digital setting circles into your pc, which would let you use them with the sky x or any planetarium software. However, the fastest slew rate of a g11S is far too slow to be worth trying to slew the scope. So as long as you are not planning on unattended imaging with automated meridian flips and multiple target objects, this setup will be perfect for imaging at focal lengths below 2m.
Cheers,
Andrew.

[nandopg]

Originally Posted by alocky

Hi Fernando,
I used a G11s for a couple of years before upgrading it to a Gemini 2.
Your Qs
1. No. It is not a goto system and has no way of knowing where it is pointed - (but q3 suggests you may be able to do something!)
2. The auto guiding is best done using a shoestring GPUSB connected to the hand controller port. This can be put through a splitter so you can have the hand controller connected as well. Any software like PHD will then be able to supply the auto guiding corrections to the mount.
3. Yes. These are digital setting circles and should let you drop any object on the chip. The analogue setting circles that come standard with the mount were usually good enough for me to get something on an Apsc chip at 1100mm focal length.

You may be able to take the output from the digital setting circles into your pc, which would let you use them with the sky x or any planetarium software. However, the fastest slew rate of a g11S is far too slow to be worth trying to slew the scope. So as long as you are not planning on unattended imaging with automated meridian flips and multiple target objects, this setup will be perfect for imaging at focal lengths below 2m.
Cheers,
Andrew.

Andrew,
Thank you so much for your considerations, I really appreciated them.

One last question: relative to the motors that the G-11s, if I am not wrong they are stepper motors and one of the major upgrade that Gemini 2 provides is the change of those motors and associated electronics for DC motors with a DC servo system. Did I get that right ? If so, stepper motors and DC motors really matters that much for long exposure subs (30 minutes) regarding a maximum focal length of 1000mm, to justify the purchase of this upgrade ?

Thanks again Andrew,

Fernando

[wasyoungonce (Brendan)]

The Losmandy G11s digital drive uses stepper motors and the unit has an HC/CCD port meaning you connect the handcontroller to this and ST4 autoguide by use of a shoestring GPSUB.

This allows autoguider (and hand controller) signals to be fed to the system. This system is essentially a "push to" meaning you align your mount setting circles and push the mount to the desired object. The main reason is that the stepper drives are very slow is "slew rate" to be of any use. Alternately many users of this system use external digital setting circles and "push to" (like the JMI NGC-MAX). This is more accurate as the art of using setting circles is almost lost!

Of course this can be a bit laborious in finding dim objects but many users enjoy this part.

The Gemini 2 is a servo system that employs DC servo motors (with inbuilt encoders) and electronics system that has inbuilt object catalogues etc. You can command the system to go to an object and it will slew to it rapidly as the servo motors can run at much faster rates (compared to the Digital drive). Thus the Gemini 2 is a "goto" system meaning you ask it and it will go to the object commanded.

This makes it easy to find dim DSOs etc (if aligned well). The Gemini 2 can also be controlled by ASCOM and other planetarium programs which makes it versatile.

There no great advantages of a DC servo over a stepper system. But in this case, Losmandy has kept the digital drive system as an entry level and the Gemini 2 for those who like goto systems.

They both track in RA equally as well its just the Gemini 2 has much more functionality and connectivity, such as LAN, USB, RS232 etc. Thus this is more suited for astrophotography. Well IMHO.

[alocky (Andrew lockwood)]

Hi again Fernando,
For a single 30 min sub at 1000mm there will be absolutely no difference between the stepper and servo versions of the G11.
The only reason I upgraded mine was to enable me to go to bed after starting the system - to do automatic meridian flips you need goto and plate-solving. In practice, however the unattended imaging works about 10% of the time and I usually wake up to a 10" pointing into the ground with a bewildered Scottish terrier entangled in the cables and only an extra 5 min of data after I'd walked away. :-)
If you're happy to babysit the scope, stick with the G11s for now, and upgrade later - it takes 20 minutes to install a G2.
Cheers,
Andrew

Originally Posted by nandopg

Andrew,
Thank you so much for your considerations, I really appreciated them.

One last question: relative to the motors that the G-11s, if I am not wrong they are stepper motors and one of the major upgrade that Gemini 2 provides is the change of those motors and associated electronics for DC motors with a DC servo system. Did I get that right ? If so, stepper motors and DC motors really matters that much for long exposure subs (30 minutes) regarding a maximum focal length of 1000mm, to justify the purchase of this upgrade ?

Thanks again Andrew,

Fernando

[nandopg]

Andrew, Brendan:
Thank you guys for your time to answer my questions. Everything is clear. As an update, I should say that I turned down the business.

I will stick with the EQ-6 in its new fashion, the AZ EQ-6 GT. The reason is that I have operated my observatory in a semi-automatic way. I can't be beside the telescope the whole night because of a disability I have on my back and legs.
I have frame capture schedule, auto-focus and meridian's flips automated. I also have a clouds alarm that, once fired, I stop the session, close the roof and go back to bed.
So, to have these same capabilities, I would need the functions provided by Gemini-2.

As I've been operating my stuff with Neq-6 successfully, I thought better not change anything, even more with all of these new variables involved and just quit the G11 idea.

Thanks again guys and have all a great weekend,
Fernando