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topgearuk

1st Light in 2 years, New Equipment - Horsehead Nebula - What's going on?

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IanL    817

Definitely something wrong with your dark frame . On the left is your dark auto-stretched in PI  (600 seconds, unity gain, temperature -20C). In the middle is a dark frame take with my camera with the same stretch applied, and on the right a clone of it with an auto-stretch (600 seconds, unity gain, temperature -15C). Yours has a median of 2,144 ADU (16 bit scale), and mine has a median of 384 ADU.

Dark.thumb.png.ce2b96dfae92c7dbce7181707f5063b0.png

The 5C temperature difference is not enough to explain the much higher levels and the gradient in your darks. It could be a faulty camera but I suspect you have light leaking in to the imaging train somewhere. The first step would be to take the camera off the filter wheel, cap the end and then cover the cap with aluminium foil (plastic caps can allow in IR which the camera will pick up). Make a new dark frame and check it to see if you get something closer to what I have.

Edited by IanL

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topgearuk    38
4 minutes ago, Allinthehead said:

I just had a look at your dark and my first instinct is that your camera is faulty. However your bias doesn't seem to have the same issue.

How do you take your darks? I cover telescope, camera, everything really and i only take them at night.

Hi Richard, thank you so much for your fast reply.

I took my darks in work, telescope wasn't covered, just on a bench and set to -20c

4 minutes ago, Allinthehead said:

If i were you i would change the usb cable connecting the camera.

I will try another usb cable, although it was a different cable that I used to take the Darks and Bias.

4 minutes ago, Allinthehead said:

You could try taking the camera in doors with no scope or filter wheel attached, just camera with the cap on. Don't bother with cooling for now. Connect directly to laptop with a different usb cable and try a short dark say 60 seconds at lowest read noise gain. Do it with the camera covered and lights off. This should eliminate the possibility of light leakage. If you get the same result then i would send an email to your supplier with a dark frame attached.

Richard.

I will try this tonight when I get home from work, using a different usb cable, if I upload this here would you mind taking a look at the dark frame? What gain would you suggest?

Many Thanks

David

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topgearuk    38
11 minutes ago, IanL said:

Definitely something wrong with your dark frame . On the left is your dark auto-stretched in PI  (600 seconds, unity gain, temperature -20C). In the middle is a dark frame take with my camera with the same stretch applied, and on the right a clone of it with an auto-stretch (600 seconds, unity gain, temperature -15C). Yours has a median of 2,144 ADU (16 bit scale), and mine has a median of 384 ADU.

Dark.thumb.png.ce2b96dfae92c7dbce7181707f5063b0.png

The 5C temperature difference is not enough to explain the much higher levels and the gradient in your darks. It could be a faulty camera but I suspect you have light leaking in to the imaging train somewhere. The first step would be to take the camera off the filter wheel, cap the end and then cover the cap with aluminium foil (plastic caps can allow in IR which the camera will pick up). Make a new dark frame and check it to see if you get something closer to what I have.

Thank you too, yes there seems to be a large difference in dark frames between mine and yours.. My dark's were taken in a brightly lit office (not thinking this would cause any problems) as it was attached to the scope with the cover on.

I will take another dark tonight, just camera only and as you described, I will do both a 60 second (as mentioned by Richard) and a 600 second sub and post here if you would be good enough to look for me? 

Thanks

David

Edited by topgearuk
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IanL    817

No problem. Bear in mind that you'll need to eliminate the source of the leakage for your lights and flats too (unless it's simply coming through the telescope cap). Unless you have a totally dark imaging location, ambient light will leak on to the imaging train and affect all frame types to a greater or lesser extent.

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Allinthehead    1,181
23 minutes ago, topgearuk said:

What gain would you suggest

It doesn't matter that much i was just suggesting a high gain with short duration 60 seconds at about 300 gain. Short duration so you don't have to wait 10 minutes for an answer.

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Stub Mandrel    6,059
On 08/01/2018 at 17:15, topgearuk said:

Just to answer your post 1st, this is a single 10 minute frame, no stacking was done, this is a screen shot straight from SGP, with it using it's own stretch function.

Scope: TS 102 mm f/5.1 APO, ZWO 1600 mm-cool, ZWO Filter wheel with Astronomik 31mm Ha 6nm @ unity gain (139), -20C

It is the 1st photo shot with this scope, filter, mount and camera. So with so many changes It's hard for me to find the culprit or is it just amp glow?

Before this I used a Canon 450d with clip filter and a Skywatcher Evostar 80ED.  So this is my 1st time shooting with mono, with new soft and hardware.

IanL Thanks for your replies and will reply in a separate post.

I would be very concerned if the ASI1600MM-Cool has more amp-glow than my home modified cooled Canon 450D. I can stretch my 5-minuite darks until they sweat and there's no sign of effects like that. the speckles on this master dark are not hot pixels, just the brightest 'dark pixels' stretched far more than I would stretch any data.

MasterDark_ISO800_300s.thumb.jpg.fe13d8940fd94f226d9ba63eeb53cf16.jpg

Edited by Stub Mandrel

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topgearuk    38

Here are some pictures of my setup and I have just taken a 10 minute sub Dark at unity gain at -20c.

https://www.dropbox.com/s/6bpwu5o4000pmkx/Target 1_600sec_1x1__frame1_dark.fit?dl=0

Due to not being able to get some of the metal ring pieces a part to fit the dust cap to front of camera (I have ordered some strap wrenches for tomorrow, good old Amazon), I had to loosely place dust cap on front of camera nose down like shown in the attached picture, but did place camera at the back of a draw and managed to close it other then the usb cable coming out the front side, very small gap, I had a battery in the draw to work the cooler and was set to -20c

This was a new usb 3 cable, do you think I have a problem with the camera?

 

 

IMG_0647.JPG

IMG_0649.JPG

IMG_0652.JPG

Edited by topgearuk

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IanL    817

The new dark is visually identical to the old one. Median ADU is 2,112 vs 2,144 for the previous one, so marginally better but still miles off where it should be.  It doesn't look like a light leakage to me following the latest test, especially given the pattern is identical despite the different capture conditions.

Can you confirm you are using the latest ZWO driver and that you set the gain and offset using the 'Unity Gain' setting in the dropdown?  I think this is starting to look like a camera electronics issue to be honest and would contact your supplier for advice.

Edited by IanL

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Allinthehead    1,181
5 minutes ago, IanL said:

The new dark is visually identical to the old one. Median ADU is 2,112 vs 2,144 for the previous one, so marginally better but still miles off where it should be.  It doesn't look like a light leakage to me, especially given the pattern is identical despite the different capture conditions.

Can you confirm you are using the latest ZWO driver and that you set the gain and offset using the 'Unity Gain' setting in the dropdown?  I think this is starting to look like a camera electronics issue to be honest and would contact your supplier for advice.

I agree with Ian, as a last try i would confirm drivers are up to date take another dark, and send to it to your supplier if it's still the same. 

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topgearuk    38

Thanks for your replays, here are 2 screen shots, look's like latest drivers installed.

The camera is 2 weeks short of one year old (only just got round to using the camera, had all intentions last year, but a new baby put stop to that lol) if these settings look fine then will get in touch with UK supplier

Camera settings.JPG

Driver.JPG

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Stub Mandrel    6,059

I'm not familiar with the software but the gain says 139 and I woudl expect to see '1' if it was set to Unity.

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IanL    817

Yes, 139 gain, 21 offset are the correct settings for unity. I usually use USB limit 40 for deep sky and calibration frames so again that is correct. Get on to the supplier before the warranty expires.

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topgearuk    38

Thanks for everyone’s help and advice, I have emailed the shop, earlier today.. They replied and said they have never seen this before. I have emailed them more dark subs as requested and they are speaking to ZWO.

I hope I get a quick out come as I’ve been waiting for the winters sky. 

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topgearuk    38

As above, I'd like to thank you all for your help, this hobby is very challenging (I like a challenge) and when you are muddling by, without the knowledge, it's hard to work out if it's something your doing wrong or a problem with the kit as in this case, and allinthehead without your help i'd have gone on thinking it was as it should be or the problem was elsewhere, the shop got back my faulty camera yesterday and confirmed they were seeing the same thing.

I would like to thank First Light Optics, for great customer service.. They are loaning me a demo unit while mine gets sent back for repair. And even offered me to keep it if I like as it hasn't been used much, I am condensing this. Loan camera will be with me today. That is great customer service in my book.

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Allinthehead    1,181
7 hours ago, topgearuk said:

As above, I'd like to thank you all for your help, this hobby is very challenging (I like a challenge) and when you are muddling by, without the knowledge, it's hard to work out if it's something your doing wrong or a problem with the kit as in this case, and allinthehead without your help i'd have gone on thinking it was as it should be or the problem was elsewhere, the shop got back my faulty camera yesterday and confirmed they were seeing the same thing.

I would like to thank First Light Optics, for great customer service.. They are loaning me a demo unit while mine gets sent back for repair. And even offered me to keep it if I like as it hasn't been used much, I am condensing this. Loan camera will be with me today. That is great customer service in my book.

Great result and delighted you got it sorted. 

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