Pardee Lake Obervatory

[AlanP]

USB Net Power 8800 by Aviosys.

I just did some Online searches and did not see the same pricing offered currently. Maybe they were clearing out stocks... Currently looks to be about $30, including on Amazon.
AlanP

[AlanP]

The Cog gear is keyed to the Gear Drive Motor shaft. In placing two Motors onto the Cog Drive System Tracking, the two Cog Gears need to be in sync, they need to both engage the Drive Track with a set spacing between them.

On my first attempt to install, I disconnected power to the second drive and slowly indexed the Drive Track until the second Motor Cog would engage. Unfortunately, I neglected to reconnect the power to the second Motor at initial testing. The second Motor became a brake, and caused damage to the powered drive's gear pack. On the positive side, inspection showed that the design does provide nicely for a "shear pin" type safety to prevent major damage to the motors.

In got a new 4-level gear pack shipped in. Changeover was simple and now I have three sets of back-up Gear Levels [silver lining].

So this time I made sure both Motors had power for testing. Start ups now are very smooth without any lurching due to torque run away. I can still power up the drives at the higher motor control settings, to a point where they can get jumpy, with issues in the Dome rotation geometry.

There is a convenient flaw [an air bubble] in the cover label of the motor control that is conveniently about the highest speed that is still very controlled and stable. At that setting, one full rotation of the Dome takes 6-minutes. So then, any slew can be reached in 3-minutes or less. Good enough for that task.

At the lowest index marker on the Motor Controller, the Dome travels 3" in one minute. I did some testing and dropped that down lower, to 2" travel in one minute and below, but it will be easier to work with the convenience of a index marking to line up to. So I decided to try out the 3"/one minute timing for last night's imaging session.

The face plate flaw marker worked nicely for slewing to the targets. Very comfortable vibrations, noise and not too long in duration... I am very satisfied with that part of the performance.

I set up on M101 for 20+ minute imaging sunframes. And I have a comfort level for about how long I can currently stretch out the subframes in the available Shutter opening.

Using the USB controlled power switch over VNC, I cycled the software Off/On Timer for two one-minute rotations [6" of rotation]. As M101 was at a high altitude and the skies were stable, guiding was running about .28 rms or less in X and Y axis. I could not detect any change in the smooth guiding during the powered Dome rotation cycles. Rotation movement was totally invisible. Meridian flip required, so I inspected the Dome/Shutter to Scope relationship. Everything looked great for a longer imaging run, if the Mount had not run out of available travel.

So once reset after the meridian flip, I ran some more sessions, again injecting a remote Dome rotation from time to time. Clouds began to threaten further progress. So time for something called sleep. The shut down inspection showed again that I had comfortable room for extended imaging, if the weather had co-operated. I ran from 10 PM until 4 AM without having to visit the Dome at all, beyond the meridian flip requirement.

At this point, the Project is a complete success for me. The twin motors provide over 800 in-ounces of torque. More than enough for any Winter icing. And at the lower rotation setting, I cannot detect vibration anywhere that I have placed my hand on. So now I just focus on imaging... AlanP

[AlanP]

Turned out to be the best night in a long while. I picked up strong enough Guide Stars, that got even better as M101 climbed. And I was able to get long sessions from both sides of Meridian. The AP Mount is able to be set to shoot well beyond a Meridian Flip. But that takes setting up, which I have no experience at. The Guide Charts dropped into the .1 RMS range in X and Y. It looked like it flat lined and had me concerned about some form of problem. But turns out the Guiding was just that good...

The first run was about 160-minutes, a new record for me stretching the Shutter Window. The Scopes were centered in the open Shutter at time for the flip.

The second session, after that meridian flip did not fair as well, as I could not recall reducing the Motor speed prior to leaving the Dome. Turns out that I had set it properly. But as I was not sure, I did not cycle the rotation enough. So I ran out of Shutter at about 4AM. Frankly, the shut down allowed for some sleep.

I got a total of 11x 23-minute subframes in Mono [253-minutes] and 9x 32-minute subframes in OSC [288-minutes], for a total of 9-hours of data for the night.

I do have to work myself into some habits. But so far it looks like I can stretch the Shutter time nicely enough, if I remember to set up for rotation as I leave the Dome. Not too much different than my having to think before I focus a Scope, as I run four MicroTouch Focusers through one Switch Box. I haven't sent focusing command to the wrong Scope in a long time... AlanP

[AlanP]

Well it's time for a change. I have reworked the dual Mounting Tooling for the Scopes. The 5" Refractors have been pulled and will be replaced by two AT8RCs. They will start at 1218mm FL and will carry the twin TMB92SS Refractors at ~500mm FL.

The wider spread of the RCs will mean that remote rotation will become more important to extend imaging sessions. That's the plan at least. Looks like the weather won't clear for many more days. AlanP

[AlanP]

I posted some images taken on the second night session in the Astrophotography Section. The change from 5" Refractors to AT8RC Scopes: 1) moved the imaging from 910mm to 1610mm FL, 2) greatly reduced the length of the Scopes swinging in the dark [and totally prevents any crashing] and 3) resulted in a large drop in payload. So what is not to like? AlanP

[AlanP]

For the M106 and M101 [recently posted images in the AP section] imaging session, I babysat the process in the Dome, to make sure the Murphy did not get me. So I got a chance to monitor the drive motion for the Dome Shutter.

Using the supplied software, I set the timer routine to 15-seconds and dialed the motor speed control to the first marking. You can hear the switch at power on. No vibrations can be felt, and the on axis guider, operating at 1617mm [.94as/p image scale] shows no sign of reacting to the Dome rotating. No granted, dialed down like it is, you cannot see the motion. But over several minutes of cycling ON/Off at 15-second timings, it definitely moved.

Why cycle rather than a start On then Off switching? It gives me an opportunity to easily shut down the process for motion. If cycling at 15, 30 or even 60-seconds, you then have a 15, 30 or 60-second Off window to cancel the timing. The other thing I like about this cycling is that I can run the motion every time I have to monitor/work at the control Laptop [assuming that I am running remote from the house]. For example, each time I reset the AO, I let it pulse for some number of cycles...

As there are to motors now running, the torque available will no doubt work through snow and ice. Speed wise, I tend to start the Dome rotating and then send the slew command to the Mount. Generally the Mount finished first, giving me time to dial down the rotation to set the edge of the Shutter about where it needs to be. AlanP

[Tombstone17]

Wow, Now I know what star gazing heaven looks like, Thanks for the pics, if I win the Lotto I know what I am asking for!!!!

[AlanP]

I think there will be another change coming. Likely that I will install a CF AT10RC with Focal Reducer to run Mono, while keeping an AT8RC to continue gathering OSC. I can get a small boost in resolution, gather more light, result in the TMB92s riding at about the same height and also drop the Focal Ratio a touch. I am guessing that I will end up with about 1720mm FL when that phase is complete. At that point, I think I will have pushed my luck about as far as it can be stretched. So hopefully the signature image will be changing by this Fall. AlanP

[fmhill]

AlanP,

A great and very interesting thread, Thanks for taking the time to document what you are doing...

[AlanP]

Hopefully It will inspire a "That might work!" moment for someone else. So far my only regret was that I had wished the Dome was one foot larger. That wish changed with the AT8RC install. Now I can comfortably move about in the Dome and have been pleasantly surprised at the minimal trade offs the longer Focal Lengths have brought.

Converting on 8" to the AT10RC will come with some pain. There will probably be a 20# boost in weight. The focal length and amount of diameter growth, will eat up more Shutter width and will force a touch better focus and guiding. And the Scope will take back some of the Dome available area. But I expect the pay off to be enough to justify reworking the Mount again... AlanP