michael8554

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

PHD2 likes to Cal where the stars are "moving ' the fastest ie near Dec = 0

Michael 

Depends how you are Polar Aligning.

With a polarscope, most have a year scale for compensating for Polaris's shift.

If you run out of years then you can guesstimate. 

After all the polarscope is only really good enough for visual.

If you have a PC based tool, I don't know if they even use Polaris.

Michael

What is the worm end-float like when loaded ?

Michael

Time to say what your equipment is - mount, focal lengths, pixel sizes.

Lets say you have one of those tiny guidescopes that give 6arcsec/pixel.

And you're imaging at 2arcsecs/pixel.

A 12 pixel dither on the imaging camera is 2 x 12 = 24arcsecs.

How many pixels does the guidecam have to Dither to make the imaging camera Dither 24arcsecs ?

24/6 = 4 pixels.

If the NINA setting is for the guidecam, your 7 pixel Dithers are too much, and probably increasing Settling times.

If the NINA setting is for the imaging camera, then you should try 12.

Michael

Was that 7 pixels of the imaging camera, or the guide camera ?

12 pixels of the imaging camera on every image is common.

Michael

"Stars didn't look tight in test shots,"

2 arcsec/pixel may be Under Sampling, leading to enlarged stars.

Or poor focus ?

"cuiv the lg" ?

Beats me.

Closest I could find was  Cuiv, The Lazy Geek

Michael

You haven't said which camera ?

Dithering, Darks, and Flats.

Michael

1. Can't see the settings as the screen grab is overexposed.

If you hit the print screen or Prnt Scrn button at the right of the top row of your keyboard you get a copy of the screen in the Clip Board that you can paste.

2. Everything is green on the status bar.

RA =  0.29,  Dec = 0.20,  Tot =  0.35 look good.

As long as your Imaging scale is larger than about 0.4arcsec/pixel you should have round tight stars.

3.   "i can't change the scale from pixels in phd2 its greyed out"

I can only suggest you reload PHD2.

Don't erase it, you will loose your settings.

Just reinstall, it will overwrite.

Michael

At 1626mm FL you'll need a guidecam with big pixels, to get a sensible pixel scale.

The Costar is 5.2um, the ASI 220MM only 4um, a LodeStar has 8.2umx8.4um pixels.

Perhaps the ASI 220MM Binned 2X or 3X would do.

But the guidecam sensor needs to be a good size-match for the 10mm x 10mm prism, the ASI 220MM is only 7.68mm x 4.42mm.

Probably there are better matches out there.

Michael