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Progression


-Joe_
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I've spent the past few weeks assembling my astrophoto gear and working out what I need and how I might use it.

After all the rubbish weather recently, we got 3 clear nights (if you can call them that this time of year).

 

25th June 2019:
EQ6-Pro Mount, Celestron 6SE scope, ZWO ASI1600MM with L filter.
Using Ekos/KStars to control everything from my macbook, I spent a good  3 hours getting a polar alignment. Time for a quick exposure of 30s, pointed at M13 and got, well, something a bit rubbish. But it was *my* rubbish. Processed to hell to at least get something i can look at (StarTools)2019-06-25-m13.jpg.9fc266427e900626cd6929c99a7f2558.jpg
 

26th June 2019:
My new SkyWatcher 72ED arrives (still waiting for the flattener). Add a filter wheel and RGB filters, then ZWO OAG and camera.
Polar align now took about 30 mins - accurate to 50" according to ekos.

Aimed at Brocchi's Cluster, 40x30s of each of LRGB, guided, with darks & dark flats (I'm amazed that worked so easy). Stacked DSS, then StarTools. 

2019-06-26-brocchis-cluster-(no-flats).thumb.jpg.c8c344257f5be24e754b349fb488e480.jpg

27th June 2019:
Plan on North American Nebula. Same equipment but 2x binning on RGB this time.
Polar alignment is done in 10mins now.
20x3min L, 8x3min each RGB, flats, dark, dark flats.

2019-06-27-north-american-nebula.thumb.jpg.aaca34f727ac49f9f097a84ed47a0734.jpg

A long way to go yet, but feel I'm actually getting something out of it now..
Criticisms/advice/insults more than welcome :), as it's mostly thanks to reading all your discussions/advice that I've got this far.
 

Edited by -Joe_
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Yep, I maybe sort of near you in progression, but like you said the sky is clear but still hazy sometimes , your NA nebula is pretty good for the conditions, I just need longer to perfect my guilding etc. I don't know star tools but if it helps me than great. keep posting the images. ton

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Excellent progress. What camera gain do you use? With 3 mins exposures, you are probably using unity gain or lower, I guess.

The NA nebula is mainly an Ha region, only emitting at that wavelength. Luminance frames won't do you any good on that target. In fact, they can deteriorate your image, especially if you have light pollution. Even small amounts of lp will add noise but no more signal than either an Ha filter or a red filter. Better to use an Ha filter, and unbinned rgb for the stars. For Ha you either need a longer exposure time than for rgb, or use a higher gain setting, and shoot many more frames. In my experience, cmos images improve dramatically if you increase the number of exposures to several tens per channel.

The lower corners of the NA image also seems black clipped. You will probably see a general improvement if you lower the black point while stretching (ie, keep the left side of the histogram slightly above 0).

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2 hours ago, wimvb said:

Excellent progress. What camera gain do you use? With 3 mins exposures, you are probably using unity gain or lower, I guess.

The NA nebula is mainly an Ha region, only emitting at that wavelength. Luminance frames won't do you any good on that target. In fact, they can deteriorate your image, especially if you have light pollution. Even small amounts of lp will add noise but no more signal than either an Ha filter or a red filter. Better to use an Ha filter, and unbinned rgb for the stars. For Ha you either need a longer exposure time than for rgb, or use a higher gain setting, and shoot many more frames. In my experience, cmos images improve dramatically if you increase the number of exposures to several tens per channel.

The lower corners of the NA image also seems black clipped. You will probably see a general improvement if you lower the black point while stretching (ie, keep the left side of the histogram slightly above 0).

Thanks. Yes unity gain (I think) at 139.

Interesting info about the Ha and L frames.. I have a Ha filter on the way, so will give it a go. 

When you say “several tens per channel” are you talking about reducing the exposure and fitting more frames into the same time, or just increasing the number of 3 min frames? Of course I spent the majority of my time on the L frames, so next clear night might try just RGB frames to compare.

 

 

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8 hours ago, -Joe_ said:

just increasing the number of 3 min frames

Increase the number of exposures. The exposure time should be long enough to clear the read noise floor. If your uncalibrated light frames have bands (read pattern), then you probably need longer exposures.

 

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Thanks @wimvb,

plan is tomorrow go for 3 hours RGB.. see wher that gets me, then next night do 3 hours of Ha.. then can compare all 3.

Also want to redo my darks. Suspect I did them inside, and may be borked. Will reprocess and see if a better set of darks helps (The comment about black clipping got me thinking..)

Have been planning what I call my “black box” so I can get a nice set of darks for reference.

 

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5 hours ago, -Joe_ said:

Have been planning what I call my “black box” so I can get a nice set of darks for reference

If by black box you mean a light tight box to shoot darks, then be careful. Such a box will also trap heat from your camera. Better to wrap the front of your camera in double layers of aluminium foil. Then in a dark room or cabinet/closet, which doesn't trap heat as much. Even a cooled camera will have to work harder to maintain its temperature in a box.

Good luck.

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1st July 2019:

Taking Wim's advice 3 hours of RGB. I've also been reading up on gain/exposure for the camera and come across these tables:
https://www.cloudynights.com/topic/573886-sub-exposure-tables-for-asi-1600-and-maybe-qhy163/
So change to 120x30s for each of RGB. Gain 139. 
Stacked in DSS with darks and flats, then processed in StarTools with the R as the luminance.
Definitely an imporvement (feels a little overprocessed to me)
2019-07-01-north-american-nebula-RRGB.thumb.jpg.4f37cd922f31e37e86f3ce745f1a9edd.jpg

Just set up for tonight - 3hrs of Ha, and lets see what that adds...
 

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21 minutes ago, wimvb said:

Massive improvement. It suddenly looks like that continent. The lower right looks a bit dark though.

I thought it might be just the dust lanes obscuring background stars, but will give it a bit more attention tomorrow when I have the Ha frames...

 

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The dust lanes are dark, but not solid. There is very weak detail in them. Showing that is a bit of a challenge. I think that the Ha will lift this image even more. Good luck.

Thanks for the link, btw.

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On 02/07/2019 at 22:40, wimvb said:

The dust lanes are dark, but not solid. There is very weak detail in them.

Just looking at the frame again for Ha processing. There is detail in those dust lanes, but Star Tools has dropped them quite severely compared to how they look in Star Tools. 
I was quite suprised by the lack of options when you output to jpg, so probably need use something else (Gimp? reccomendations?) to convert from the final fits to jpg..

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Had to throw the Ha frames away... all out of focus, just enough to look ok the small preview. Not sure how I messed that up, but there’s a lesson to be learnt...

I did consider PixInsight, but settled on StarTools as its workflow gelled with me when trying them all out... 

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Have you tried saving as png rather than jpeg? Otherwise, when you save a jpeg the software should ask which quality (compession) to save the image in. Both PixInsight and GIMP do that. Normally, a setting of 90 will do (100 being the best quality). This will compress the image to a manageable size, but still keep enough detail.

But jpeg is a 8 bit image format, so you will always lose information and quality during conversion.

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23 hours ago, wimvb said:

Have you tried saving as png rather than jpeg? Otherwise, when you save a jpeg the software should ask which quality (compession) to save the image in. Both PixInsight and GIMP do that. Normally, a setting of 90 will do (100 being the best quality). This will compress the image to a manageable size, but still keep enough detail.

But jpeg is a 8 bit image format, so you will always lose information and quality during conversion.

png would be my preference normally, for the reasons you give. Star Tools just gives the option of fits or jpeg (with no controls) output... a bit strange, but will save fits in future and use gimp to produce a png/jpeg/whatever

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On 04/07/2019 at 18:31, -Joe_ said:

Had to throw the Ha frames away... all out of focus

Have you got a Bahtinov mask?

I use mine every time to check focus, even when my eyes tell me it's OK, it can be slightly out.  Does your scope have a thumb screw to lock the focuser position?  I check with the Bahtinov again after I've tightened this.

John

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No I don’t.. been meaning to make one.

this wasn’t slightly out of focus though - they were big doughnuts... must have knocked when tightening the locking screw and not bothered to check.

i went and got hold of the zwo auto focus - was super easy to use. The next night out I had super focussed star trails (Don’t ask!)

hoping the forecast holds for tomorrow night and I might get something useful ..

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32 minutes ago, -Joe_ said:

No I don’t.. been meaning to make one.

this wasn’t slightly out of focus though - they were big doughnuts... must have knocked when tightening the locking screw and not bothered to check.

i went and got hold of the zwo auto focus - was super easy to use. The next night out I had super focussed star trails (Don’t ask!)

hoping the forecast holds for tomorrow night and I might get something useful ..

I made my own Bahtinov mask which worked fine, but ended up buying one which was more robust than the balsa wood I had used.

Good luck with the forecast.

John

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On 04/07/2019 at 14:13, -Joe_ said:

Star Tools has dropped them quite severely

Hi. Nice progress.

IIRC, it's not StarTools which loses the detail; it happens whenever you convert a decent looking image to jpg. If you want to show the detail, you could post the jpg along with a link to the .TIF or .png. 

It's also quite an eye opener viewing your image on other devices; what looks ok on your screen can look hideous on e.g. an iPad, your mate's 'phone...etc.

Cheers and keep up the good work.

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13 hours ago, alacant said:

It's also quite an eye opener viewing your image on other devices; what looks ok on your screen can look hideous on e.g. an iPad, your mate's 'phone...etc.

Very true.  In the past I've received a few comments that I've clipped the black level when I know I haven't and it looks fine on my own screen.  Perhaps allowing a greater margin for this would work better for me, so it looks more pleasing on other screens.

John

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