EQ8 DEC backlash question..

[Stub Mandrel]

8 hours ago, gorann said:

By coincidence I just saw this video advertizing the more recent EQ8-R, and at the end of the video the seller proudly announces that it is capable if guiding at 0.6"/pixel, and that was with OAG on a 1000mm FL telescope. As long as seeing cooperates I regularly get 0.4"/pixel with my old EQ8 (recent curve attached) even if it is carrying 40 kg of SCT and 40 kg of counterweights

I think they deliberately quote conservative figures. My HEQ5 was guiding at 0.79" last time I was out, with a 1200mm scope on it. I'm not surprised an EQ8 can halve that, and I bet the EQ8R can as well.

[tonyowens_uk]

Hi Goran. Your point about the original EQ8 and the quality of guiding it provides is well made. I have modernised or refurbished a number of them and all provides around 0.5 arcsec RMS following error on each axis when they left.

Neither revised nor original EQ8 offer antibacklash gearing. Also, the original EQ8 used a badly designed clutch that directly caused minute deformations of the mount that manifested as image shifts and (for Declination axis) binding and run-out. The Declination shaft bearings can make this problem worse, as can other constructional details. But all of this is soluble, and if done properly the mount is very dependable. 
The Freedom Find encoders were a piece of whimsy I believe. They can't be used during precision pointing such as imaging, and were aimed at casual visual users with a product mentality who stick with the Synscan control paddle. Those encoders never protected against pier crashes and contributed nothing to accuracy. Which given their tendency to deteriorate with moisture ingress into the Declination worm wheel shroud, was just as well!

With proper sealing, updated clutches, steel shafts, precision bearings and an antibacklash Declination gear, an EQ8 controlled using Green Swamp server, (a modern alternative to EQMOD) will point and autoguide a 35 kg imaging payload for years, with excellent reliability. 

[Stub Mandrel]

20 hours ago, tonyowens_uk said:

With proper sealing, updated clutches, steel shafts, precision bearings and an antibacklash Declination gear, an EQ8 controlled using Green Swamp server, (a modern alternative to EQMOD) will point and autoguide a 35 kg imaging payload for years, with excellent reliability. 

What is this 'green swamp' of which you speak?

Is it ASCOM compliant and more importantly is it more stable than EQMOD on W10 machines?

[michael8554]

Green Swamp seems to be an Astro software suite:

GS Server includes ASCOM telescope support and the Synta Protocol for SkyWatcher and Orion mounts: EQ8, EQ8-R, HDX110, AZ-EQ5GT, Sirius Pro AZ/EQ-G, AZ-EQ6GT, Orion Atlas Pro AZ/EQ-G, EQ6-R PRO, NEQ6, HEQ5, EQ5, EQ4, AzGTi.

I didn't think the Bog Snorkeling search results were relevant........

Michael

 

 

[tonyowens_uk]

3 hours ago, michael8554 said:

Green Swamp seems to be an Astro software suite:

GS Server includes ASCOM telescope support and the Synta Protocol for SkyWatcher and Orion mounts: EQ8, EQ8-R, HDX110, AZ-EQ5GT, Sirius Pro AZ/EQ-G, AZ-EQ6GT, Orion Atlas Pro AZ/EQ-G, EQ6-R PRO, NEQ6, HEQ5, EQ5, EQ4, AzGTi.

I didn't think the Bog Snorkeling search results were relevant........

Michael

 

 

I'm sure Bog Snorkelling is an important formative experience for Irish undergraduates: 

 

 

As for Green Swamp server (GSS) its been around for a while. Unlike EQMOD its in active development. Initially the target mount was just EQ8/HDI 110 but it now includes other Nantong Schmidt EQ mounts.

There are several controls which extract better performance from EQ8's when autoguiding than EQMOD does. One, is homing that is far more reliable. But the key ones for imagers are motor current doubling during tracking and autoguiding, (which doubles stepper motor torque in small corrective moves to reduce following error) and use of short range GoTo commands while autoguiding using pulse guiding. These improve corrective move accuracy, reducing control loop dither around the target position. It is necessary to download a bugfix version for the EQ8 firmware to access the full feature set. There is a discussion groups here: groups.io/GSS/

Tony