kman42

It's not marked anywhere that I've found, but it looks identical to Skywatcher mounts except that it's a different colour. Maybe it's an older version?

I got the scope and mount both secondhand. The mount is a Skywatcher EQ5.

Do you have to go through a Laptop, or can you control things through Arduino?

What kind of guiding camera is usually recommended?

I just did some tests with the tracking mount. After getting perfect polar alignment using the drift technique, I achieved a tracking accuracy ratio of 9000/FL (compared to the general rule of 500/FL for untracked astrophotography). In other words I was able to shoot 45 second exposures at 200mm and 30 second exposures at 300mm with no streaking. This was pointing at Sirius (almost at the zenith) where tracking times will be the worst.

I'm in Australia so a polar scope would be noe use to me unfortunately... I have to resort to other means!

I don't do astrophorography often, but when I do I still use it. If I can get the polar alignment right, it's very accurate and consistent.

I can't remember sorry. It was a long time ago. I think instructions on quarter stepping motors are pretty well documented though.

A Dec axis motor is definitely on the list. But for now, I have some example photos from a weekend of astrophotography. Carina Nebula: 4 minute exposure, 800 ISO, f/2, 58mm Helios lens on Pentax K7. It looks like streaking but that is just coma. Jupiter: 5 second exposure, 100 ISO, f/5, 1000mm through Skywatcher 200p on Pentax K7. Acturus: 15 second exposure, 500 ISO, f/5, 1000mm through Skywatcher 200p on Pentax K7. The stars are just starting to streak. MIlky Way: 7 1/2 minute exposure, 1000 ISO, f/4, Pentax 17-70 f/4 @ 17mm on Pentax K7. The verdict: the mount can track some brighter DSO's - I'll have to find some more impressive objects to see what results I can get from it. However, it excels at shorter focal lengths.

I'm using a Skywatcher 200p, 1000mm focal length. Is aperture important at all for the guide scope?

That was the plan - take some pictures and see how much drift there is. How big a scope do you need for the guide scope?

Dammit kens, I thought I was finished. Now you've got me researching autoguiding...

I recently completed a little project in which I built a low-cost motorised drive for my EQ5 mount. I thought I'd share my results for other people looking for a solution, as commercial drives tend to start at $200 in Australia. My drive only turns the RA axis, as it is primarily for astrophotography. Because of this, I don't need any tracking systems - it is simply a motor that spins the RA axis at the correct rate of 1 revolution per 24 hours. My drive system uses a 4 wire, bipolar stepper motor, driven by an A4988 stepper driver and an Arduino Nano, all powered using a 12V battery. The stepper motor runs in quarter-steps, and drives the pre-existing RA fine-turning gear via a V-belt. This way, I still have full manual control over the mount if I wish. Here is a parts list in Australian dollars inc. postage. Everything was purchased from either Ebay or the local Jaycar: 1. Nema 14 4 wire bipolar stepper motor : $22 2. A4988 stepper driver: $7.55 3. Arduino Nano V3.0: $6.52 4. 2x T2.5 5mm bore timing pulleys: $20.80 5. T2.5 6mm wide, 145mm long timing belt: $6 6. 4-prong locking plug (male and female): $4 7. Jiffy box: $1.95 8. 2x DPDT switches: $4 9. Locking 2 way connector: $3 10. Alligator clips: $4 For a total cost of $79.80 The counter-weights for the EQ5 weigh 11.5kg in total. The maximum distance the weights can be placed on the counterweight rod is 0.33 metres, therefore the maximum torque that a motor would ever need to turn the mount is 11.5x2x0.33 = 7.59 Nm. The RA fine adjustment knob on the EQ5 mount turns 144 rotations for every full rotation of the telescope's RA axis. Therefore, the maximum torque I would need to apply to the RA fina adjustment gear is 7.59/144 = 0.0527 Nm or 5.27 Ncm. I chose a Nema 14 Stepper motor with 18 Ncm holding torque and a maximum current draw of 0.8A per phase. This motor takes 200 steps to complete a revolution; therefore, if I want to revolve the telescope every 24 hours, I'm looking at 1 rotation of the RA fine adjustment knob every 10 minutes, or 1 step of the motor every 3 seconds. Using quarter steps to smooth out the motion, thats 1 quarter step every 0.75 seconds. The arduino is programmed with a ridiculously simple code: const int stepPin = 3; void setup() { pinMode(stepPin,OUTPUT); } void loop() { digitalWrite(stepPin,HIGH); delay(375); digitalWrite(stepPin,LOW); delay (375); } This sends a pulse to the A4988 'step' input every 0.75 seconds. That's all the programming done. The arduino is powered via 12V, which then outputs 5V to the stepper driver logic controls, while 12V also goes to the stepper driver motor voltage input. The unit is controlled with a power switch stop and start the motor, and a switch to reverse the motor's rotation by swapping the wires to one of the poles. The RA fine-adjustment shaft needed to be modified to fit the T2.5 pulley. First, I bored the pulley to 6mm to match the shaft. Then, the locking nut of the shaft was removed and the brass nut with the external thread was cut down to be flush with the housing. New notches were cut to faciulitate tightening of the brass nut, and a hole was drilled into the side of the housing to accept a locking screw to replace the locking nut, which no longer fit. The result of this was that the RA shaft now had enough room to fit the T2.5 pulley. After this, the motor was bolted in place using mechano peices, and a hole was drilled in the cover for the 3 prong locking connector. Once the cover was fitted to the mount, the 4-prong connector was the only visible sign of any modifications. Below are some pictures to illustrate the build: The original mount with the RA drive case attached: The original mount with the RA drive case removed to show where the motor will go: The modified shaft with the T2.5 gear: The stepper motor in place. The triangular plate ensures the motor can never move enough that the belt loses tension: The 4 prong locking connector - the motor's wires run through this: The completed control unit - the circuit boards were held in place using RTV silicone. The entire circuit was soldered before dropping the whole thing into the box. Made things much easier: The completed unit. I put a neo magnet on one of the tripod's leg bolts, and the control unit just clips on to the magnet when in use. The magnet is strong enough that it will never get bumped off. All that is left is to test its accuracy with some photos!