michael8554

A camera with 5um to 6um pixels would just about cover your FL range.

Michael

I hear that the Atacama Desert in Peru has good seeing.......... ;->

Michael

Try the Mead(e) section of the Cloudy Nights Forum.

 A number of world-class Meade experts there.

Michael

Do you have the correct 0.85 Focal Reducer for the ED80 ?

Without the new adapter and any filters, attach the FR to the focuser threads, and add the ASI 585 and FR at 55mm.

How many millimeters of travel are left in the focuser ?

But you said:

"I have 55mm between then camera and the reducer"

Do you mean "55mm between the camera sensor and the reducer" ?

If you have 55mm to the camera, that will be 65.5mm to the sensor.

Which may explain why you can't focus ?

Michael

The ZWO ASI 662 camera is 1920 x 1080.

Did you select a "Region of Interest" setting to get darks 1440 x 810,  others 1440 x 1080 ?

Or the image downloads were corrupted.

Michael

If your setup is not completely permanent then, a fresh Cal every night takes very little time.

And a good Cal is fundamental to good guiding.

Michael 

"Could I attempt it by changing focus and monitoring the hfr value?"

Again, I don't know what you mean by hfr.

Do you mean HFD ?

Monitor that as you alter the focus.

Michael

Not much info on your setup and settings.

Did you PA ?

Did it Calibrate successfully ?

Did you reset the focal length after swapping OTA's ?

Could be:

Pier side wrong

Huge PA error

Guidecam rotated since last Cal.

Michael

The image looks pretty good.

1.  "hfr in phd2 was in red and over 4 most of the time "

Do you mean HFD ?

Use the HFD figure in the PHD2 Star Profile window to improve focus.

2.  "I've sorted my wiring"

I hope that's the "before "image.  :-<

All the cables bunched with the blue USB are pulling on the mount, which may affect guiding.

Also the cable joins are being pulled apart so may become intermittent, particularly the blue USB into the hub.

You may need some longer cables to avoid that. 

The dew heater cables and the dummy battery cable should be gathered with the rest of the OTA cabling and attached to the OTA, before continuing onwards.

Then gathered into a smooth loop attached to say, one of the the green knobs on the mount.

Make sure that loop doesn't snag anywhere the OTA may point.

3.  The mains setup has no protection for damp, dew, or unexpected rain.

And a mains cable drum should always be fully unwound.

Michael

1. Is it a Canon DSLR, you didn't say ?

Shoot Canon video this way:

https://www.astropix.com/html/equipment/canon_one_to_one_pixel_resolution.html

2. It doesn't matter much that planets appear as "dots" in DSLR images.

If you crop the eg 5000 x 3000 pixel images to a typical planetary camera image size of 1280 x 1024.

Hey, the planet looks the same size as if you'd shot with a planetary camera !

Also it's much easier to place that tiny dot on a DSLR sensor than in a tiny sensor Planetary camera .

3. 420mm focal length is pretty short for Planetary, even with Barlowing.

Many are using a 2000mm FL SCT and Barlowing !

Michael

Paper is translucent too.

That's why it can be used to attenuate a Flat Panel.

Michael

I've used spacers made from translucent milk bottle plastic, and was surprised how much light gets in through the edges on long exposures !

Michael

"I was using a 12v 1.5 amp power supply, I don't know if this is any good but it seems to work"

But did it work, because you got a motor fault, which can be blamed on poor power supply ?

An Unregulated 12V 1.5A power supply may supply too many volts when just tracking.

And not supply enough volts under the load of slewing at high speed.

Check it's a Regulated Power Supply.

Michael

"So you might need a 5V to 12V-15V DC Converter."

"Would this provide the minimum 2 amps required by the mount ?

45W at "presumably 5V" = 9A.

At 12V that converts to roughly 3.75A, not counting conversion losses.

But a dedicated astro power tank at roughly the same price makes better sense.

Michael

1.  Is the power supply adequate ? 

The "Test" briefly slews the motors and will Fail if the power supply is poor.

2. Have you selected ETX125 in the menus, it may be setup for a different Meade mount ?

3. If you get it working, do the Train Drives routine.

The instruction manual is available online.

Michael

That's a good idea, but it's not a complete solution.

Your mount requires 12V to 15V DC.

The USB-C provides 45W at presumably 5V, they don't specify.

So you might need a 5V to 12V-15V DC Converter.

The 120V AC out could power your laptop.

Michael

"A voltmeter would be good. I assume I should have similar power?"

The voltmeter on DC Volts range may show the average voltage of the pulses when tracking.

I'd guess the motor is powered by the red and black wires.

The board may have the encoder and feedback voltages.

Compare with the Dec motor when tracking.

Michael

Have you tried with a better power supply yet ?

But Geoff mentions that this is a stepper motor.

Skywatcher describe it as a "DC Servo motor".

As I understand it, a DC Servo motor only has a single pulse drive and feedback loop from the encoder, unlike a stepper motor, which has two phased inputs.

Could be wrong.

Although a pulsed signal, you might compare the voltages with a cheap Digital Voltmeter at slew and tracking rates.

Can you swap with the Alt motor ?

Michael

I guess then that we need to hear from other Sigma 40mm F/1.4 Ar users if they get coma like that.

Such as:

https://www.cloudynights.com/topic/824952-sigma-40mm-a-f14-star-test/

Looks like you have a lens at the far end of Sigma's QC range.

Michael

"I am powering from the mains."

But how ?

The spec is "11 to 15V @ 2amp."

Users are recommending 13.8V @ 5Amp.

And it needs to be a Regulated power supply.

Michael

1.  FF = Field Flattener,  FR = Focal Reducer.

These require the correct Backfocus, or coma will result .

2. "Askar isn't a lens, but it doesn't behave like a typical refractor."

Whatever, interesting that altering Flange Distance while still able to infinity focus does change the coma.

3.  So "Too thin spacer - still coma, but smaller".

If going thinner improves the coma, then try an even thinner spacer, or no spacer ?

Michael

1.  "Yes correct, the motors seem to be fine."

You don't agree the clutch is okay ?

2.  "I can hear the motor trying to track"

Perhaps the motor has enough oomph to start a high-speed slew.

But not enough to overcome the friction of the system, bearings etc,  when tracking.

Are you able to remove the motor and worm assembly, and check the worm runs quietly without a load ?

And that the wormwheel rotates freely without binding or much resistance ?

What power supply ?

Michael

The "brass rod" is the worm, meshing with the shiny wormwheel.

If the mount slews in Az with the hand controller, then the clutch and motor must be working - right ?

Is it tracking in Az as setup in the image ?

Put a finger mark in the grease on the wormwheel adjacent to the worm, and check that the wormwheel has moved after 10 minutes.

Michael

1.  "why my Askar denies the following rule?"

That rule is for FF and FR, not necessarily for lenses.

You can test whether altering the Backfocus does actually make a difference to the coma, not just the infinity focus.

I doubt it will.

2.   30 sec exposures are showing some central elongation, try 10 secs and stretch the jpegs, they are good enough.

Michael

Hi Vroobel

Backfocus is only of concern if you have a FF or FR.

All a lens needs is to be the correct Flange Distance from the sensor, in order to reach infinity focus.

The Canon Flange Distance is 44mm.

So you raise an interesting thought that reducing the lens to sensor distance has similar effects to altering the Backfocus from a FF or FR.

Have you started at 44mm Spacing ?

Michael