The EQ3 DSO Challenge

[bobro]

First attempt at a 'proper' image with the new config of Arduino/PHD2 driving the Economy RA/DEC motors. Of course clouds did their best to thwart this : only 6 subs at 5 minutes. Trouble finding guide star so this was a bit away from the image - result was trailing (tried to fix in processing) due to polar alignment not being good enough. Still good to see M58 and the Siamese Twins in the image, plus a few other smaller galaxies.

[Nigel G]

Nice one bobro.

I also processed an image of multiple galaxys from a couple of weeks ago, have been waiting for clear skys since then.

This is just 10 x 4 minutes with flat dark and bias. Seeing was bad at the time so not a great image but at a close inspection there is at least 34 distant galaxys in the image.

The colours were quite bad so I went for B&W.

The Virgo galaxy cluster. 80ED pro, eq3 pro, canon 1300d. Orion 50mm mini guide scope and Orion starshoot guide cam.

Cheers

Nige.

I think there all galaxy's

[Filroden]

57 minutes ago, Nigel G said:

I think there all galaxy's

I think you've missed a few or a few dozen! I can see many more after just a quick glance. If you are still trialling PixInsight then it's got a couple of good scripts to solve and annotate images. That should nail all of them!

[Peco4321]

Have you tried:

http://nova.astrometry.net/

 

[Filroden]

1 hour ago, Peco4321 said:

Have you tried:

http://nova.astrometry.net/

Whilst it's great for solving imaging, it doesn't give you any control over the annotation (at least that I've found). PixInsight allows you to choose what to annotate (stars, constellations, galaxies, etc) and to fine tune it (magnitude limits, colour, font size, etc). It therefore is better for annotating the less well known galaxies.

astrometry.net

PixInisght (showing galaxies only though I suspect it may have solved some noise!)

Edited April 19, 2017 by Filroden

[Nigel G]

WOW there's a few in there

Thanks for the link Peter  

I think my PixInsight trial is about to expire, I'm very impressed with it.

There's some great tools and mostly unexplored by me. When processing an image I find myself mainly using Startools then loading up in PI for a couple of tools then finishing off in PS  

To be honest my best images have come from ST because I know it well, I'm sure PI would give a better image but I'm quite lost when straying from the few tools I use.

A long focal length scope will be before PI. And I still want a CCD  

Nige.

 

[mikey2000]

That's a lot of galaxies!   I'm keen to take a tilt at some virgo clusters soon.   At the moment, my roof blocks the view in that general direction.  Leo is just getting into view at this time of year (unless I stay up all night!).

 

I've been gathering the odd bit of data over the last few weeks.  Here are my latest efforts, all crops from APS-C shots through the 150PDS

m94  (24x3mins) (Startools managed to find some texture in the galaxy, Noel's actions helped recolour the stars)

 

M3 - again a startools colour extravaganza.  29x2mins

 

NGC2392 - Eskimo Nebula.  This is a *heavy* crop!  On the full image, it's not much more than a 'fat star'.  I 2xdrizzled this one in DSS.  Given the graininess of the rest of the pic, maybe the nebula looks a bit fake.... 7x3mins

 

 

And an old favourite - m51.  (14x2mins + 7x4mins)  I think I'll revisit this one to try and even out the somewhat blotchy background...  I was pleased with the detail in the galaxy arms

 

finally, just for fun, I put my guide camera (QHY5L-ii) into the eyepiece holder and filmed the moon for stacking and processing.  I can't wait until Jupiter clears my roof :-)

Edited April 21, 2017 by mikey2000
Updated M51 pic. Still needs deblotching though!

[Peco4321]

Great session last night, getting better at polar alignment all the time, and picking up some processing tips. These are my best yet of each target, M3 and the Leo Triplet. I can get about 45-60 sec exposure but my intervelometer only does 30 or bulb, so these are all 30 sec as I couldn't be bothered to stand and click all night. All at ISO 1600, no darks or flats as I really struggle with flats. I also renamed the master bias frame to re-use as a master dark, as I think that was mention a few pages ago. Anyway, here you go, again cc appreciated.

 

 

Edited April 21, 2017 by Peco4321

[bobro]

Images look fine for 30 second exposures. The lack of flats can probably be got round with processing for images with small galaxies, but could be an issue for nebulae or single galaxies. Flats aren't really that difficult : keep the scope/camera config unchanged, put a piece of paper across the scope, point to an even source of light at least a couple of meters away (don't point a source of light at the scope) and take flats at the same ISO so that a mid-point grey image is the result. For me the single biggest (and easiest) improvement to imaging was flats - really worth doing! I hope this makes sense/helps?

Bob

[Peco4321]

Yes it does make sense thanks @bobro, I will have another go. I seem to get flats with a darkish band at the top then quite bright white. I usually leave the camera connected once packed up after a session and go back the next day some time so focus is the same etc and I put it in AV mode and take about 20 images pointing up at a bright sky but not at the sun (as it's always bloody clear in the day) with a white pillow case over the scope. 

I will persevere, also, I'll post a flat on here sometime for advise as well. 

[SteveNickolls]

On 4/19/2017 at 16:22, Nigel G said:

The colours were quite bad so I went for B&W.

There's something special about a monochrome image and galaxies that ticks lots of boxes. Well done :-)

Cheers,
Steve

[happy-kat]

I keep mine simple the only thing to change when taking flats is shutter so the histogram peak is in the centre. I leave my camera is M mode just like it was for taking the lights.

[Peco4321]

38 minutes ago, happy-kat said:

I leave my camera is M mode

Thanks, so I just need to increase shutter speed up to what sort of level then please? 

[alacant]

1 hour ago, Peco4321 said:

to what sort of level

Hi. With your diffuse light source as described above, set to Av. Depress the shutter far enough to get a shutter speed reading. Now flip back to M with the same speed you just recorded in Av. Fire away; 20 snaps work well. If you're using the sky, work quickly.

1 hour ago, Peco4321 said:

increase shutter speed

You'll almost certainly need to decrease the shutter speed for the flat frames in comparison with that which you used for the light frames. HTH.

Edited April 22, 2017 by alacant

[happy-kat]

I tend to find that the shutter speed becomes something like 1/160 to get the histogram in the mdidle with everything else unchanged.

[Stub Mandrel]

I just switch to AM mode for the flats.

[bobro]

Tuesday had a lovely clear night, but Air Traffic Control decided to route every available plane right across my imaging view! From 23 subs, 5 had plane trails, with the 2 worst shown below. So I decided to try DSS with Kappa Sigma clipping, keeping all 23 subs rather than discarding those with trails. The final image didn't show the plane trails, but I don't quite understand how Kappa Sigma clipping works. Anyone care to explain? Was this the best approach?

Thanks

Bob

Edited April 27, 2017 by bobro

[Stub Mandrel]

58 minutes ago, bobro said:

Kappa Sigma clipping works. Anyone care to explain?

Imagine you are calculating the average height of a class of kids, but your tape measure sometimes 'glitches'. If you ignore three or four 'way out' measurements the average you get will still be pretty close to the actual average if all the measurements were OK, and much better than if you had included the random giants!

kappa Sigma basically spots the height measurements that are outside the expected range and ignores them - it works out the standard deviation of the data and dsicrads any points atht are more than a certain amount away from the mean. It then recalculates the mean.

Your plane trails just give one 'high' reading (or more where trails cross) to a series of points on the image, which kappa sigma ignores.

 

[bobro]

1 hour ago, Stub Mandrel said:

it works out the standard deviation of the data and dsicrads any points atht are more than a certain amount away from the mean. It then recalculates the mean.

Thanks Neil - sort of what I thought might happen, though DSS has an iteration count (5 used in my example). Is this just an iterative way of arriving at the final pixel value by discarding the values farthest from the mean? So if an iteration shows that all values are within an acceptable range the iteration stops? Starts to make sense now.

Also, because we are presumably talking about individual pixel values, all of the other pixels that aren't affected by the plane trails benefit from the increased number of subs - which means lower noise? So best to keep all subs rather then discard those with problems in small areas?

Perhaps I'm being lazy, but with Kappa Sigma clipping also eliminating noisy/dead pixels and the use of dithering, I now don't bother with darks. OK, I know my images are pretty basic, but is this appropriate?

Sorry for so many questions, but this seems to be part of this astro imaging journey - working out what works best for your own setup and inclinations! (Until you change things of course.)

Bob

[wimvb]

8 hours ago, bobro said:

 

Also, because we are presumably talking about individual pixel values, all of the other pixels that aren't affected by the plane trails benefit from the increased number of subs - which means lower noise? So best to keep all subs rather then discard those with problems in small areas?

Perhaps I'm being lazy, but with Kappa Sigma clipping also eliminating noisy/dead pixels and the use of dithering, I now don't bother with darks. OK, I know my images are pretty basic, but is this appropriate?

 

Bob

A. Yes, but you probably only see the effect if the number of subs dropped is about the same as the number kept. Removing two subs out of a stack of 30, hardly makes a difference. But removing those out of a stack of 5 will.

B. Yes again, if you dial in the correct kappa value. Adding a bad pixel map in lieu of darks also helps. As will other methods, such as cosmetic correction, which looks at each pixel neighbours in each individual sub, and then replaces it if it deviates more than a certain amount (again in units of standard deviation).

Edited April 28, 2017 by wimvb
Typos

[Stub Mandrel]

10 hours ago, bobro said:

Thanks Neil - sort of what I thought might happen, though DSS has an iteration count (5 used in my example). Is this just an iterative way of arriving at the final pixel value by discarding the values farthest from the mean? So if an iteration shows that all values are within an acceptable range the iteration stops? Starts to make sense now.

Also, because we are presumably talking about individual pixel values, all of the other pixels that aren't affected by the plane trails benefit from the increased number of subs - which means lower noise? So best to keep all subs rather then discard those with problems in small areas?

Perhaps I'm being lazy, but with Kappa Sigma clipping also eliminating noisy/dead pixels and the use of dithering, I now don't bother with darks. OK, I know my images are pretty basic, but is this appropriate?

Sorry for so many questions, but this seems to be part of this astro imaging journey - working out what works best for your own setup and inclinations! (Until you change things of course.)

Bob

I agree with Wim, yes you are right but I wouldn't use it instead of darks unless I had a bad pixel map, because the better and cleaner the image before it goes through kappa sigma, the better the result..

[bobro]

Thanks Neil and Wim - KS clipping is much clearer now. (Neil - FYI - I've ordered an AR0130 sensor module from Amazon. Should be testing in a couple of weeks.)

Bob

[mikey2000]

And now a quick question about EQ3 Pro DEC motor adjustment.....

 

I discovered I had some kind of 'retrograde backlash' in Dec.  Eg, when slewing North then changing to south, it would actually continue North for a moment (even accelerating slightly!) then abruptly head of S in the end.   At 8x speed, there was even a noticeable jumping movement in the wrong direction before starting off in the correct direrection.  It happened in both reversals, N to S or from S to N.

 

Anyway, I readjusted the Dec worm and it seemed to have gone.  I now have a Dec axis that operates smoothly with minimized backlash using the manual controls. (no retrograde action any more!!)

 

But with the Dec motor reattached, the backlash is significantly greater.   It seems the motor gear doesn't exactly fit the worm spur gear - there's a bit of slop before it re-engages against the cog surfaces as I change direction.

 

I can only see one possible asjustment for the Dec motor - the allen bolt that holds it on to the mount.  I just pushed it as hard and as level as I can, hoping to get the motor cog to sit as cleanly as possible against the worm gear.  I just can't get rid of the motor/worm backlash though.

 

It's a bit annoying!  I found two tiny allen screws under the motor (see pic).  Might they be of some use?

 

Any clues appreciated!

 

 

[bobro]

My new AR0130 guide camera module arrived earlier than expected, so decided to give it a go by imaging M3 - first time on this target and I was surprised how pretty it is. The guide camera worked very well - practically no need to move the guide scope to find a guide star, so I will post details under DIY Astronomer. M3 image (cropped): 13 subs at 300 secs. Kappa Sigma clipping stacking used again due to planes!

Edited April 29, 2017 by bobro

[Stub Mandrel]

55 minutes ago, bobro said:

My new AR0130 guide camera module arrived earlier than expected, so decided to give it a go by imaging M3 - first time on this target and I was surprised how pretty it is. The guide camera worked very well - practically no need to move the guide scope to find a guide star, so I will post details under DIY Astronomer. M3 image (cropped): 13 subs at 300 secs. Kappa Sigma clipping stacking used again due to planes!

 

Jings!

Is that the ne off ali baba?