The "No EQ" DSO Challenge!

[happy-kat]

That's a great image.  Lots of star colour. 

I'm being beaten by it getting dark too late for me.

[Filroden]

32 minutes ago, happy-kat said:

That's a great image.  Lots of star colour. 

I'm being beaten by it getting dark too late for me.

Same. I set up tonight with the intention of getting 3 hours of Ha. I failed to switch on DST so my first StarSense align failed. When I did get aligned and switched on the camera it showed a massive smear somewhere. So I stripped it down and cleaned it. Realigned and now the sensor was covered in dust. I would still have to do two more aligns and it was getting so late I was concerned about waking the neighbours so I've just packed up. I think I'm going to have to wait until August.

[rotatux]

For me it's another story as I am on holidays... I made a session for the whole night on 2017-05-24 from 10pm to 4:30am, had to stop after daylight had become too strong. Unfortunately some strong wind came after 11:30pm (black night starting around 11:00pm) and ruined most of my subs... the Nexstar SLT is so brittle that any wind will make my tubes shake , how are yours ? (especially the Synscan)

And the show must go on, here's one which came out not so bad from what I could save.

The Leo Triplet.

Gear: Olympus E-PL6 with Skywatcher 130PDS 632mm/4.86 and SWCC at f/4.55 on Celestron Nexstar SLT
Capture: 22 lights (/ 18% keep) x 30s x 3200iso, 23 darks
Process: Regim 3.4, Fotoxx 12.01+

[Shaun_Astro]

That is a nice clean image. Galaxies require so many subs.

I attacked M71 in Saggita the other night, bit of a noisy image, and I need to make better flats, also need a coma corrector, and forgot bias and needed more dark subs! But it turned out reasonable. Had to lay waste to 70% of subs again!

 

[Stub Mandrel]

1 hour ago, Shaun_Astro said:

forgot bias and needed more dark subs! But it turned out reasonable. Had to lay waste to 70% of subs again!

Bias frames last months, darks last a good while as well, I split mine into warm, cool and cold nights.

[The Admiral]

10 hours ago, Stub Mandrel said:

Bias frames last months, darks last a good while as well, I split mine into warm, cool and cold nights.

Or just don't use darks . Replace them with a good quality master bias. I think DSS has a bit of a fit (or should that be FITS? No? Too early in the morning.) if you have file names replicated in several places, so make sure that the true master bias, and the master bias used as a dark, are named differently. It's a while since I used DSS now. Also use Kappa-Sigma clipping. Seems to work for me, but don't ask me why.

Ian

Edited May 28, 2017 by The Admiral

[rotatux]

2 hours ago, The Admiral said:

Also use Kappa-Sigma clipping

BTW this algorithm has a parameter, let's call it the "sigma factor". What values are you using ?

/me depends on subs quality: poor => 0.5 or less, average => 1.0, good => 1.25 to 1.5, very good => 1.6 and above.

I also noticed how the pixel keep rate seems related to the sigma factor, e.g. 0.5 gives around 25%, 1.0 => 50%, 1.5 => 75 to 90%. So that may also be a selection criteria if you want to keep a given pixel percentage of your subs.

[The Admiral]

To be honest I just leave it at default, and that applied to DSS and now to AstroArt. I think the problem of not using darks is when there is a need to correct for amp glow.

I found an interesting thread on CN: https://www.cloudynights.com/topic/487977-can-we-talk-seriously-about-flatdarkbias-frames/

Ian

[Stub Mandrel]

Can you check what the default values are for me?

I think I changed the value too high and the help documentation doesn't give any recommended values...

[The Admiral]

13 hours ago, Stub Mandrel said:

Can you check what the default values are for me?

I think I changed the value too high and the help documentation doesn't give any recommended values...

My DSS is set to a Kappa of 2, no of iterations=5; I don't recall ever changing them. Is there not a reset to defaults option somewhere?

Cheers, Ian

[Stub Mandrel]

10 minutes ago, The Admiral said:

My DSS is set to a Kappa of 2, no of iterations=5; I don't recall ever changing them. Is there not a reset to defaults option somewhere?

Cheers, Ian

Ah thanks, that's what mine are set to. I was made nervous by @rotatux's comment giving a range from 0.5 to 1.6, and the fact that the 'adaptive' version seems to work better.

I can't find a reset button, there may be one somewhere!

[The Admiral]

3 minutes ago, Stub Mandrel said:

Ah thanks, that's what mine are set to. I was made nervous by @rotatux's comment giving a range from 0.5 to 1.6

I think he uses Regim, Neil. To be honest, I 've not got my head around how these values affect the final outcome, and I certainly haven't done any tests. By the sound of it, you have.

Ian

[Stub Mandrel]

5 minutes ago, The Admiral said:

I think he uses Regim, Neil. To be honest, I 've not got my head around how these values affect the final outcome, and I certainly haven't done any tests. By the sound of it, you have.

Ian

I thought I had, but it seems not!

[rotatux]

2 hours ago, The Admiral said:

My DSS is set to a Kappa of 2, no of iterations=5

Interesting: so DSS does multiple iterations, while Regim does only one. Hence the very different "kappa" values. It might just as well fall back on my values range if using iterations=1.

While I'm highly confident at the mathematical / statistical meaning of doing only one iteration, I'm more in unknown territory about doing many, especially as it will progressively shift the average value used as criteria. I still have to think about it as it seems to "just work" for many people.

Is there some kind of synthetic report in DSS, where it would indicate the net proportion of kept pixels, so we can get an idea of the final selectivity of this algorithm ?

Edited May 29, 2017 by rotatux

[scitmon]

May I submit my first ever real attempt at a DSO with my ED80 Ds-Pro and Az GOTO SynScan...

M27 Dumbbell Nebula:

Edited June 18, 2017 by scitmon

[rotatux]

38 minutes ago, scitmon said:

May I submit my first ever real attempt at a DSO with my ED80 Ds-Pro and Az GOTO SynScan

No need to ask and welcome to altaz imagers.

That's a very nice image, with crips stars and beautiful colors (stars and nebula). The blue background is nice too, after all.

Did you have any experience with astro imaging before ? if that's your first it's a very good one.

[scitmon]

Thank you for positive comments.  I have a lot to learn about post images processing, hence the blueish tint to the image which seems to be a side effect of trying to tease out those colours of the nebula in Photoshop.  I've only dabbled in moon shots and Jupiter until now.  My original planned target last night was the Black Eye Galaxy but I was getting star trails even with 5 second exposures.  I'm not sure why some targets seem to have less trailing than others, I guess its down the the proximity Polaris?  I still need to astro mod my DSLR and buy a FF too, so hopefully better things are to come.

[The Admiral]

You most certainly can and welcome. Indeed, nice small and round stars, and an excellent 1st DSO. What camera are you currently using, how many subs and what sort of exposure?

Certainly processing can't be undervalued, and although Photoshop can and is used for astro work, you might wish to look at other more specialised applications.

I'm sure you already appreciate that there are essentially 2 types of trailing with Alt-Az imaging, field rotation which depends on the direction you are pointing the scope, and the degree of tracking. The former you can't do anything about, apart from limiting exposure duration, and the latter seems to involve black magic and in what mood the mount is in! Levelling and aligning are both critical though, but even after taking all the care you can, sometimes things just don't work out. I think if it was me I'd hone your skills with your existing camera. Don't foget that the larger the sensor the more obvious the field rotation will be at the frame edges, so you will end up cropping.

Keep posting your images!

Ian

[SteveNickolls]

13 hours ago, scitmon said:

I'm not sure why some targets seem to have less trailing than others

Hi, and thanks for posting. You might want to get a copy of, 'Astro-photography on the Go-Using Short Exposures with Light Mounts' by Joseph Ashley, available from the SGL's sponsors. A very worthwhile read on the whole subject. As The Admiral pointed out you are witnessing the effects of field rotation and some mount movement, the book has a field rotation table identifying the maximum exposures of objects at different positions in the night sky, basically longer for objects in the East and West and at lower altitudes.

I'm interested too at the performance of your telescope, do you find there's light aberration, particularly blue fringing (certainly not judging by your image)? The D80 Ds-Pro sounds excellent value at £349.

Cheers,
Steve

 

Edited June 19, 2017 by SteveNickolls

[happy-kat]

You might want to research the benefits or not of ff camera, vignetting will be one draw back so there may be no advantage. A bigger sensor may be too big for the light cone the telescope has.

[scitmon]

2 hours ago, happy-kat said:

You might want to research the benefits or not of ff camera, vignetting will be one draw back so there may be no advantage. A bigger sensor may be too big for the light cone the telescope has.

There is a Skywatcher FF that was made for the ED80 and I just assumed that would be beneficial regardless of the camera used.  Thanks, I'll look into that and make sure it will be beneficial.

 

3 hours ago, SteveNickolls said:

Hi, and thanks for posting. You might want to get a copy of, 'Astro-photography on the Go-Using Short Exposures with Light Mounts' by Joseph Ashley, available from the SGL's sponsors. A very worthwhile read on the whole subject. As The Admiral pointed out you are witnessing the effects of field rotation and some mount movement, the book has a field rotation table identifying the maximum exposures of objects at different positions in the night sky, basically longer for objects in the East and West and at lower altitudes.

I'm interested too at the performance of your telescope, do you find there's light aberration, particularly blue fringing (certainly not judging by your image)? The D80 Ds-Pro sounds excellent value at £349.

Cheers,
Steve

 

Thank you for that book recommendation.  I'll make a point to adding that on my next FLO order.  I've not seen any light aberration, and the DS-pro supposedly virtually eliminates it.  Having said that, I'm not really the person to ask as I have not had any experience with other telescopes to form a basis of comparison.  I would recommend looking at this thread for ideas of what the ED80 can achieve: 

13 hours ago, The Admiral said:

You most certainly can and welcome. Indeed, nice small and round stars, and an excellent 1st DSO. What camera are you currently using, how many subs and what sort of exposure?

Certainly processing can't be undervalued, and although Photoshop can and is used for astro work, you might wish to look at other more specialised applications.

I'm sure you already appreciate that there are essentially 2 types of trailing with Alt-Az imaging, field rotation which depends on the direction you are pointing the scope, and the degree of tracking. The former you can't do anything about, apart from limiting exposure duration, and the latter seems to involve black magic and in what mood the mount is in! Levelling and aligning are both critical though, but even after taking all the care you can, sometimes things just don't work out. I think if it was me I'd hone your skills with your existing camera. Don't foget that the larger the sensor the more obvious the field rotation will be at the frame edges, so you will end up cropping.

Keep posting your images!

Ian

I was using a unmodified Canon 1000D on 1600 ISO for 15 seconds exposures. I think I will seriously look into getting Pixinsight, it looks impressive (and pricey).

[SteveNickolls]

54 minutes ago, scitmon said:

I think I will seriously look into getting Pixinsight

Thanks for the link to the discussion on the D80 Ds-Pro, it sounds very useful.

Have you tried StarTools for your image processing? You can try it for free though you can't save images unless you later decide to purchase. Ivo is a very helpful person and you can read more here-http://forum.startools.org/viewforum.php?f=3 and there's a long video in The Astro Imaging Channel you could watch-http://forum.startools.org/viewforum.php?f=3

Cheers,
Steve

[happy-kat]

@scitmonSorry confusion.

I thought you meant full frame as in ff dslr. I now realise you meant field flatner when you wrote ff.

[The Admiral]

5 hours ago, happy-kat said:

@scitmonSorry confusion.

I thought you meant full frame as in ff dslr. I now realise you meant field flatner when you wrote ff.

Ah, me too!

Ian

[Filroden]

On 6/18/2017 at 18:58, scitmon said:

May I submit my first ever real attempt at a DSO with my ED80 Ds-Pro and Az GOTO SynScan...

M27 Dumbbell Nebula:

Really nice first attempt. There's a lot of data hidden behind that blue cast. I don't know how to fix it in Photoshop but a quick pass through PixInsight's ColourCalibration and some crude curve adjustments shows you this. I've broken the stars (they are all showing orange) but there is a lot of colour in the nebula that you could bring out.