The EQ3 DSO Challenge

[Stub Mandrel]

Here's my Andromeda galaxy from last night. 20 5-minute subs. Long exposures seem to give much better star colours.

[jjosefsen]

3 minutes ago, Stub Mandrel said:

Here's my Andromeda galaxy from last night. 20 5-minute subs. Long exposures seem to give much better star colours.

Very nice! I'm struggling so much with my gear right now I'm about to go nuclear.. So seeing that you can get 5 min subs with your eq3-2 gives me a little hope.

[Stub Mandrel]

46 minutes ago, jjosefsen said:

5 min subs with your eq3-2

That's with guiding...

Pleiades, 13 five-minute subs:

[jjosefsen]

Yeah I figured it was with guiding, mine is just acting up and drifting in seemingly random directions. And that's without guiding.

[Stub Mandrel]

6 minutes ago, jjosefsen said:

Yeah I figured it was with guiding, mine is just acting up and drifting in seemingly random directions. And that's without guiding.

See if you can get one of the new  reticle polarscopes.

[jjosefsen]

2 hours ago, Stub Mandrel said:

See if you can get one of the new  reticle polarscopes.

Im pretty sure I have one actually.

 

The thing is this:

After a rough polar alignment I was checking my alignment with the drift alignment function in Backyard Nikon, and by all accounts (and luck) I had a spot on alignment.

After recording for 2 minutes had minimal drift, so I thought I was good for atleast 90 seconds subs. But after slewing and balancing again to be a little east heavy, my 90 seconds subs came back with lots of trailing on both axis.

Ended up going down to 60 seconds, the problem persisted but some frames came back quite good and were keepers. I was ASCOM dithering every 3 frames, and I have been speculating if slack in the gears could be the source after a dither.. Thoughts?

I might just end up taking the whole thing apart and servicing it, found a good tutorial on youtube.

[Stub Mandrel]

Far from happy with the colour in this one. An hour and ten minutes of 2 minute subs is far from enough here. The cooled subs show more detail than last years efforts, but colour is p*** poor and sadly mixing them wasn't very successful. I shall come back to this data and try other permutations - and add more cooled data, skies willing!

 

[mikey2000]

It looks nice and sharp and noise free.  I'm sure the info is in there somewhere....  It looks to me like you dragged the saturation slider all the way to max on this one.

[Stub Mandrel]

3 minutes ago, mikey2000 said:

It looks nice and sharp and noise free.  I'm sure the info is in there somewhere....  It looks to me like you dragged the saturation slider all the way to max on this one.

To be honest I gave up trying to get the flame to be a different colour from the other nebulosity :-(

In contrast, I just went to my M1 data and that almost processed itself:

[rotatux]

Nice M1... I personally struggled to frame it (too weak and too small) last year in my H-LP sky and abandonned, so that's some achievement

Oh and question about your HH+Flame: what filter did you use ? your colors look like what I get with my UHC...

[Stub Mandrel]

8 hours ago, rotatux said:

Nice M1... I personally struggled to frame it (too weak and too small) last year in my H-LP sky and abandonned, so that's some achievement

Oh and question about your HH+Flame: what filter did you use ? your colors look like what I get with my UHC...

I use my moon and skyglow, which is quite a cheap one but works well. Good point though, it may have killed all the yellow in the flame. If it'[s clear tomorrow I will have another shot. Tonight was a bit of a write off for reasons far to complex to explain :-(

My previous M1 just looked like cotton wool, this one has some 'cobweb' texture so quite pleased. I will have a go with the 150PL which will double the image scale.

[Nigel G]

On Wednesday, November 15, 2017 at 20:48, Stub Mandrel said:

Far from happy with the colour in this one. An hour and ten minutes of 2 minute subs is far from enough here. The cooled subs show more detail than last years efforts, but colour is p*** poor and sadly mixing them wasn't very successful. I shall come back to this data and try other permutations - and add more cooled data, skies willing!

 

How did you add the Ha, I take it it's Ha + RGB. Looks like they haven't blended well. 

[furrysocks2]

Another go at M33...

What a pain... I've got a Datyson T7M/ST102/EQ3, no finder, RA stepper on an Arduino with no RTC or timer interrupt, just a sleep/step/sleep/step loop.

Tracking kept dropping out, but I twiddled the current limiter and it seemed to settle down.

As before, 2x2bin max-gain ~1s exposure to focus (not very successfully) and snapshots from SharpCap with a script monitoring the output folder, plate-solving and displaying FoV in Stellarium... twiddle the dec slomo, loosen the RA clutch to reposition, lock it up, re-snapshot, wait until Stellarium updates, repeat until I find M33.

I didn't polar align more than being able to see Polaris while sitting on the ground. That, and the poor timing on the Arduino, still means that darkness creeps up from the edge of the stack.

Anyway... 30s 66 gain, 10 darks, live stack of 10. Only real difference this time is I took it 16 bit. I'm pushing my shonky setup at 30s, stars are elongated, but that's ok cause they're not in focus anyway. Dropped resolution to compensate. Levels twiddled in Gimp 2.9.

 

Tonight, I give up. I don't care about Auriga. Too much like hard work.

[furrysocks2]

5 minutes ago, furrysocks2 said:

Another go at M33...

Not easy. Maybe I should buy myself a Canon...

[jjosefsen]

8 hours ago, furrysocks2 said:

Not easy. Maybe I should buy myself a Canon...

Man you really do it on hard mode.. ? I fibd this hobby difficult enough with "better" gear.

[Stub Mandrel]

11 hours ago, Nigel G said:

How did you add the Ha, I take it it's Ha + RGB. Looks like they haven't blended well. 

That bad eh?

It's just OSC RGB :-(

[Stub Mandrel]

11 hours ago, furrysocks2 said:

Another go at M33...

What a pain... I've got a Datyson T7M/ST102/EQ3, no finder, RA stepper on an Arduino with no RTC or timer interrupt, just a sleep/step/sleep/step loop.

Tracking kept dropping out, but I twiddled the current limiter and it seemed to settle down.

As before, 2x2bin max-gain ~1s exposure to focus (not very successfully) and snapshots from SharpCap with a script monitoring the output folder, plate-solving and displaying FoV in Stellarium... twiddle the dec slomo, loosen the RA clutch to reposition, lock it up, re-snapshot, wait until Stellarium updates, repeat until I find M33.

I didn't polar align more than being able to see Polaris while sitting on the ground. That, and the poor timing on the Arduino, still means that darkness creeps up from the edge of the stack.

Anyway... 30s 66 gain, 10 darks, live stack of 10. Only real difference this time is I took it 16 bit. I'm pushing my shonky setup at 30s, stars are elongated, but that's ok cause they're not in focus anyway. Dropped resolution to compensate. Levels twiddled in Gimp 2.9.

 

Tonight, I give up. I don't care about Auriga. Too much like hard work.

If you need accurate timing (which you do) you need to use a timer interrupt. just use it to reset the timer and set a flag. Outside the interrupt another loop can watch teh flag and when it sees it set, step teh stepper and reset the flag.

[furrysocks2]

3 minutes ago, Stub Mandrel said:

If you need accurate timing (which you do) you need to use a timer interrupt. just use it to reset the timer and set a flag. Outside the interrupt another loop can watch teh flag and when it sees it set, step teh stepper and reset the flag.

Yeah. I calculated the inter-micrcostep interval and nobbled the stepper driver demo code, haven't revisited. As it happened, my quick and dirty sidereal tracking rate is almost bang on for lunar tracking. I'll get the other stepper wired in and house it all with sensible hookup. Intending to go down the OnStep/ASCOM route. May need to revisit stepper supply before I fry either of the drivers. I might look to buy stock items if I get any money at Christmas time.

[rotatux]

13 hours ago, furrysocks2 said:

just a sleep/step/sleep/step loop

Beware that if you use a fixed delay in the sleep, this kind of loop has inherent timeshifting builtin because of various lags in execution.

Unless it's already the case, you should aim for fixed average frequency, by using the builtin clock to compute the next delay each cycle. I mean something like:

avgPeriod = CONSTANT
target = clock() + avgPeriod
while (tracking) :
	step()
	sleep(target - clock())
	target += avgPeriod

NB: BTW, this kind of code works very well even without any interrupt handling, it will absorb and correct minor local variations of time and execution as long as your clock is stable enough.

Edited November 17, 2017 by rotatux
React to later post of Neil

[furrysocks2]

2 minutes ago, rotatux said:

Beware that if you use a fixed delay in the sleep, this kind of loop has inherent timeshifting builtin because of various lags in execution.

Unless it's already the case, you should aim for fixed average frequency, by using the builtin clock to compute the next delay each cycle. I mean something like:

avgPeriod = CONSTANT
target = clock() + avgPeriod
while (tracking) :
	step()
	sleep(target - clock())
	target += avgPeriod

 

Sweet, yeah precisely. I think it's the additional latency/imprecision that means it works better for the moon than for the background.

In terms of things to be getting on with, it's definitely "mount first". Clear tonight, but no time to spend today. :/

[Stub Mandrel]

I found this (I usually use AVR Assembler) http://www.hobbytronics.co.uk/arduino-timer-interrupts

 

Just change the code to give the correct interval for your stepper and pulse the stepper instead of an LED:

/* 
Example Timer1 Interrupt
Flash LED every second
*/

#define ledPin 13
int timer1_counter;
void setup()
{
  pinMode(ledPin, OUTPUT);

  // initialize timer1 
  noInterrupts();           // disable all interrupts
  TCCR1A = 0;
  TCCR1B = 0;

  // Set timer1_counter to the correct value for our interrupt interval
  //timer1_counter = 64911;   // preload timer 65536-16MHz/256/100Hz
  //timer1_counter = 64286;   // preload timer 65536-16MHz/256/50Hz
  timer1_counter = 34286;   // preload timer 65536-16MHz/256/2Hz
  
  TCNT1 = timer1_counter;   // preload timer
  TCCR1B |= (1 << CS12);    // 256 prescaler 
  TIMSK1 |= (1 << TOIE1);   // enable timer overflow interrupt
  interrupts();             // enable all interrupts
}

ISR(TIMER1_OVF_vect)        // interrupt service routine 
{
  TCNT1 = timer1_counter;   // preload timer
  digitalWrite(ledPin, digitalRead(ledPin) ^ 1);
}

void loop()
{
  // your program here...
}

Edited November 17, 2017 by Stub Mandrel

[furrysocks2]

1 hour ago, Stub Mandrel said:

(I usually use AVR Assembler)

We AVR going a PIC off-topic....

(Edit: The day I met my wife, I had just used assembly and interrupts to get an LED flashing on a PIC)

Edited November 17, 2017 by furrysocks2

[Stub Mandrel]

1 minute ago, furrysocks2 said:

(Edit: The day I met my wife, I had just used assembly to get an LED flashing on a PIC)

Just goes to prove that using a PIC needn't spoil your whole day

[Peco4321]

Thursday nights Double Cluster, always a great target. Managing to get 45 sec exposures regularly now, will work on pushing thatvto 60 sec next time out. This is 35 x 45 sec ISO 800 plus darks and bias. May add flats later and reprocess. 

[Peco4321]

My latest attempt at M42, 58 x 45 sec ISO 800, darks and bias, flats made it worse!!  150p eq3-2 canon 1100d dual motors.