My EAA Adventure continues... 2023-04-30

[Big Ian 65]

Hi All, I managed to get my back focus distance set closer to where it should be, and had first light with my focus motor fitted! Seeing was not the best, and there was a lot of Dew forming! These images were taken on the evening of 2023-04-29, through into the morning of 2023-04-30. This time my calculated Focal ratio is 0.55x after uploading some of the images to astrometry.net which showed my pixel scale to be 0.462 arcsec/pixel.

I firstly had a look at some old favourites, then commenced my foray into the Caldwell Catalogue, which has some stunning objects.

The Sharpcap FWHM focus tool worked well after I dialled the settings in to suit my setup. 

My next learning exercise is getting my head around producing some Master calibration images to hopefully improve the results of the live stacking in Sharpcap - any advice from you seasoned pros out there would be appreciated - It is clear that the images need calibration frames adding, but having no experience producing the Darks and Flats correctly, I guess I just need to get stuck in and do it - I have tried the Dark, and Flats tool in Sharpcap with limited success it seemed to fail because the light frame colour depth was different, I also think I may have light leaking in which spoils the Darks too! Anyone have a cheat sheet to simplify the exposure settings etc for taking calibration frames?

Celestron CPC925, 0.63x reducer, SV605C camera, Starsense and Celestron Focus motor - Mele Quieter PC mounted on OTA running CPWI, Sharpcap and ASCOM Server - RDPing in from Home PC running Stellarium. (Oh and I love Skysafari Pro on my Ipad)

[barkingsteve]

Looks like you had a very busy night/morning    When taking a master flat, open the histogram when setting an exposure time and try and keep the peeks between 30%-70% and ( iirc ) the master dark needs to have the same settings as the lights ( exposure time, temp if cooled camera, etc. )  but you seem to be doing ok    Been a while since i done some quality EAA, think i need a few sessions  

[Jonathan_Shields]

Great captures looks like a decent session. I tried C5 and C7 last night and found them both very hard to get much detail at all with my 6 inch dob but where they are is right near some streetlights...I think I'll try again when they are better situated (or buy an air rifle!).

Darks i have tried i just put the camera outside with the cap on for 10 mins before setup then use the capture dark function in Sharpcap. I honestly didnt notice much difference but i have the ZWO585 which allegedly has no amp glow.

Flats i have never tried as they seem a faff but I'd be interested what people think about their worth for EAA.

Edited April 30, 2023 by Jonathan_Shields
Correct spelling

[Jonathan_Shields]

Btw which are the galaxies after the Iris nebula?

[Big Ian 65]

1 hour ago, Jonathan_Shields said:

Great captures looks like a decent session. I tried C5 and C7 last night and found them both very hard to get much detail at all with my 6 inch dob but where they are is right near some streetlights...I think I'll try again when they are better situated (or buy an air rifle!).

Darks i have tried i just put the camera outside with the cap on for 10 mins before setup then use the capture dark function in Sharpcap. I honestly didnt notice much difference but i have the ZWO585 which allegedly has no amp glow.

Flats i have never tried as they seem a faff but I'd be interested what people think about their worth for EAA.

Thanks for the response Jonathan, have you tried calling your local authority about the street lights - I had real problems with a badly sited lamp, and I phoned KCC and spoke to a tech guy in their street lighting team, he was really helpful, he dropped the brightness at 22:00, and again to a lower value at midnight. It really helped - these new LED streetlights are remotely programmable apparently, all I had to do was give him the serial number painted on the Lamp post and the post code!
I am also keen to hear what everyone thinks about the benefits (or not) of using Darks and flats with a modern CMOS camera for EAA with sharpcap ( I also have an IMX 585 based camera) with supposed low amp glow!

[Big Ian 65]

2 hours ago, barkingsteve said:

Looks like you had a very busy night/morning    When taking a master flat, open the histogram when setting an exposure time and try and keep the peeks between 30%-70% and ( iirc ) the master dark needs to have the same settings as the lights ( exposure time, temp if cooled camera, etc. )  but you seem to be doing ok    Been a while since i done some quality EAA, think i need a few sessions  

Thanks Steve, yeah it was busy but fun… I would really like to get the noise down a bit more if possible!

[Big Ian 65]

1 hour ago, Jonathan_Shields said:

Btw which are the galaxies after the Iris nebula?

Hi Jonathan, the next image after the Iris nebula is C7, then two images of C12, and two of C21…

I assume that you cannot see the file names of the images - does anyone know how to show the image file names in a post?

[PeterC65]

Your images look great. I'd be very happy with them. I sometimes tweak the snapshots I take of live stacks on the night. I use Affinity Photo and Topaz DeNoise, just a minimal workflow with no masks or anything complex but it does sometimes substantially improve the images.

I've only recently started using dark frames for EAA. Previously I had been using the SharpCap Hot Pixel Removal feature which does work well. I took some master dark frames in the warmer daytime, compared these with HPR and decided that they didn't work as well (the background sky was brighter and there were still some hot pixels when I used the dark frames). Then I tried taking the dark frames on the night, they where noticeably better than HPR and this is now my standard approach.

I let the scope and camera cool to equilibrium, then cover the scopes objective and run the SharpCap darks capture function with the same camera settings I will use for the session. It's very simple to do and takes 5 minutes, with SharpCap auto selecting the new dark frames for use at the end of the process. I don't change the scope / camera / reducer setup during a session and almost always use the same camera settings for DSOs (gain of 400 and exposure of 4s with my IMX585 based Uranus-C camera).

Taking the dark frames on the night like this means they are an exact match. I wouldn't try to create a set of master darks to use across sessions.

I do have an electronic filter wheel and changing filters may make a difference when using dark frames. I've yet to decide. In theory it shouldn't make a difference.

I haven't taken flat frames, mainly because doing so seem like a lot of effort and it takes long enough as it is to get setup for a session. I'd be interested to know how people take flat frames quickly.

 

[Xio1996]

That was a great observing session. 

I agree with @PeterC65 that darks have the edge on SharpCap's Hot Pixel Removal. However, I found Hot (Cold) Pixel Removal with SharpCap's unguided ASCOM dithering function covered up a multitude of evils 😄 I do find myself using 4, 8 and 15s subs during an evening, depending upon the object being observed. If I stuck to one (sub-exposure) then maybe I wouldn't find darks quite the chore!

As has been pointed out, creating darks is a straightforward activity even with an uncooled camera. Give them a go.

I don't know if it is down to the chip size of my camera (AA294C) or just my individual preference but I do like a flat calibration frame. A flat does improve my observing experience but I have done plenty of observing sessions without flats. To create flats I use a cheap A3 light panel off Amazon to provide the illumination. Using SharpCap's Flat Capture seems straightforward - Monochrome flat with dark, 25'ish frames, short 200-600ms subs, lowest gain. Flats allow a more aggressive image stretch before dust and the vignetting become objectionable (to me 😄) without them. 

Have fun.

Pete

[Big Ian 65]

11 hours ago, PeterC65 said:

Your images look great. I'd be very happy with them. I sometimes tweak the snapshots I take of live stacks on the night. I use Affinity Photo and Topaz DeNoise, just a minimal workflow with no masks or anything complex but it does sometimes substantially improve the images.

I've only recently started using dark frames for EAA. Previously I had been using the SharpCap Hot Pixel Removal feature which does work well. I took some master dark frames in the warmer daytime, compared these with HPR and decided that they didn't work as well (the background sky was brighter and there were still some hot pixels when I used the dark frames). Then I tried taking the dark frames on the night, they where noticeably better than HPR and this is now my standard approach.

I let the scope and camera cool to equilibrium, then cover the scopes objective and run the SharpCap darks capture function with the same camera settings I will use for the session. It's very simple to do and takes 5 minutes, with SharpCap auto selecting the new dark frames for use at the end of the process. I don't change the scope / camera / reducer setup during a session and almost always use the same camera settings for DSOs (gain of 400 and exposure of 4s with my IMX585 based Uranus-C camera).

Taking the dark frames on the night like this means they are an exact match. I wouldn't try to create a set of master darks to use across sessions.

I do have an electronic filter wheel and changing filters may make a difference when using dark frames. I've yet to decide. In theory it shouldn't make a difference.

I haven't taken flat frames, mainly because doing so seem like a lot of effort and it takes long enough as it is to get setup for a session. I'd be interested to know how people take flat frames quickly.

 

Thanks for the advice Peter - I will try your technique regarding darks - will let you know how I get on! TBH I have been using the smart histogram for each target and using its recommendations for exposure and gain - it does seem to give reasonable results - down side is that the gain changes for each target!  Do you think it is feasible to run the dark tool prior to each target?

[Big Ian 65]

5 hours ago, Xio1996 said:

That was a great observing session. 

I agree with @PeterC65 that darks have the edge on SharpCap's Hot Pixel Removal. However, I found Hot (Cold) Pixel Removal with SharpCap's unguided ASCOM dithering function covered up a multitude of evils 😄 I do find myself using 4, 8 and 15s subs during an evening, depending upon the object being observed. If I stuck to one (sub-exposure) then maybe I wouldn't find darks quite the chore!

As has been pointed out, creating darks is a straightforward activity even with an uncooled camera. Give them a go.

I don't know if it is down to the chip size of my camera (AA294C) or just my individual preference but I do like a flat calibration frame. A flat does improve my observing experience but I have done plenty of observing sessions without flats. To create flats I use a cheap A3 light panel off Amazon to provide the illumination. Using SharpCap's Flat Capture seems straightforward - Monochrome flat with dark, 25'ish frames, short 200-600ms subs, lowest gain. Flats allow a more aggressive image stretch before dust and the vignetting become objectionable (to me 😄) without them. 

Have fun.

Pete

Thanks for the advice Pete, I appreciate your thoughts… Do you think it’s better to try and use recommended gain and exposure settings for each target then? That of course is a ball ache for matching the darks, I made a flats ‘filter’ out of two layers of T-shirt material and an embroidery hoop which works ok on those days when the sky gives a reasonable illumination - will probably try the light panel off Amazon too… 

 

[PeterC65]

1 minute ago, Big Ian 65 said:

Thanks for the advice Peter - I will try your technique regarding darks - will let you know how I get on! TBH I have been using the smart histogram for each target and using its recommendations for exposure and gain - it does seem to give reasonable results - down side is that the gain changes for each target!  Do you think it is feasible to run the dark tool prior to each target?

I think running the dark capture tool before each target would be too much effort, and unnecessary.

I started off using the smart histogram tool to determine the required gain and exposure then I did some tests, collecting snapshots of live stacks with the same number of frames at different gain and exposure settings which I studied side by side in the daytime. It's difficult to compare things serially on the night I find.

I was quite analytical about it. I came to the conclusion that a gain of x400 was best, anything lower was too dark, anything more was too noisy. For the exposure time, 4s gave good results and is short enough for near real time observing which is important to me. I sometimes use 8s on fainter targets and very occasionally 15s but that is about the limit of my AZ mount.

So for me, I know I'm going to use x400 and 4s so I take the dark frames with that setting. If I do happen to change exposure (I almost never change the gain) then I switch back to Hot Pixel Removal.

 

[Big Ian 65]

Hi guys, I have a few more questions, which also seem to have a bearing on whether flats and darks work in Sharpcap.

What colour space do you guys use is RAW 8 bit reasonable or is RAW 16 preferable? And when do you need to change colour space?

Do you guys use region of interest and routinely change the capture area? If so when and why - or is it just a simple matter of framing?

To Bin or not to Bin… thoughts and benefits/downsides?

I found out the hard way that flats and darks (obviously) have to match capture area and Colour space - I felt such a plonker when I tried to apply different size and different colour space D&F’s… Der!

and final question for today… how do you ‘nudge’ the black and intermediate level bars in the histogram… I really struggle with the resolution of dragging with the mouse?

[Big Ian 65]

15 minutes ago, PeterC65 said:

I think running the dark capture tool before each target would be too much effort, and unnecessary.

I started off using the smart histogram tool to determine the required gain and exposure then I did some tests, collecting snapshots of live stacks with the same number of frames at different gain and exposure settings which I studied side by side in the daytime. It's difficult to compare things serially on the night I find.

I was quite analytical about it. I came to the conclusion that a gain of x400 was best, anything lower was too dark, anything more was too noisy. For the exposure time, 4s gave good results and is short enough for near real time observing which is important to me. I sometimes use 8s on fainter targets and very occasionally 15s but that is about the limit of my AZ mount.

So for me, I know I'm going to use x400 and 4s so I take the dark frames with that setting. If I do happen to change exposure (I almost never change the gain) then I switch back to Hot Pixel Removal.

 

I like this approach Peter - will definitely give it a try!

[Xio1996]

1 hour ago, Big Ian 65 said:

Do you think it’s better to try and use recommended gain and exposure settings for each target then?

I'm not sure what the recommended gain/sub settings are for an object. Its just that some objects like globular clusters/open clusters/PN etc are bright, hence I shorten the sub length. I don't alter the gain settings that much. For a long time now I was using a gain of 900 (Altair Astro scale, HCG start point). However, I have moved up a little to 1000 recently as my 294 chip has problems at that LCG/HCG crossover point. Maybe, I should just pick a single sub length and go with it? 

One thing I found on flats is that the black level (offset?) has to be the same as the light frames. Using darks and flats together is most probably the best solution but SharpCap can use hot pixel removal and flats together as long as the lights black level is the same as the flats. 

As always, give it a go and see what you prefer. 🙂

 

[Big Ian 65]

50 minutes ago, Xio1996 said:

I'm not sure what the recommended gain/sub settings are for an object. Its just that some objects like globular clusters/open clusters/PN etc are bright, hence I shorten the sub length. I don't alter the gain settings that much. For a long time now I was using a gain of 900 (Altair Astro scale, HCG start point). However, I have moved up a little to 1000 recently as my 294 chip has problems at that LCG/HCG crossover point. Maybe, I should just pick a single sub length and go with it? 

One thing I found on flats is that the black level (offset?) has to be the same as the light frames. Using darks and flats together is most probably the best solution but SharpCap can use hot pixel removal and flats together as long as the lights black level is the same as the flats. 

As always, give it a go and see what you prefer. 🙂

 

Thanks again Pete, the recommended settings I was referring to are the ones in the smart histogram ‘brain’ dialogue box, once you have run the sensor calibration, it uses the results and the limiting parameters you dial in to recommend gain, exposure and recommended number of subs…it does a scan of the current live target image to decide. So far for me it has worked quite well… when I put in limiting parameters of say max 10 sec exposure and total exposure limit of half an hour it tends to recommend a gain close to the gain crossover point… for my camera it is around 295 and then around 200 subs of 3-5 sec (at least in that order of magnitude) I seem to have got reasonable results after less than half of the recommended total exposure time - it seems that after a certain no of stacked images the gain in clarity is not worth the extra wait… at least for my eyes and equipment!

After all that, it sounds like the other Peters empirically derived method shows that using a fixed preset exposure has reasonable results and allows easier production and use of calibration frames… I guess the big question is does this approach with good cal frames give better results than trying to optimise the gain/exposure ratio to minimise noise and maximise light capture…

Hopefully we will get some clear skies again soon so I can try some different options… I guess this is all part of the fun! 
As I have said before, I am still constantly amazed at what the EAA method allows me to see from my back garden in light polluted Margate - it is more than I ever hoped for from home astronomy, and as you said - those eyepiece things now seem assigned to the bottom drawer!

With your help I now have the outside scope setup nicely and other than a couple of trips outside to check the power lead is not fouling I can sit inside and align, focus and capture remotely in the warm! 

[Jonathan_Shields]

On 30/04/2023 at 21:54, Big Ian 65 said:

Thanks for the response Jonathan, have you tried calling your local authority about the street lights - I had real problems with a badly sited lamp, and I phoned KCC and spoke to a tech guy in their street lighting team, he was really helpful, he dropped the brightness at 22:00, and again to a lower value at midnight. It really helped - these new LED streetlights are remotely programmable apparently, all I had to do was give him the serial number painted on the Lamp post and the post code!
I am also keen to hear what everyone thinks about the benefits (or not) of using Darks and flats with a modern CMOS camera for EAA with sharpcap ( I also have an IMX 585 based camera) with supposed low amp glow!

Thanks i might try that. They do seem ridiculously bright by default.

[PeterC65]

13 hours ago, Big Ian 65 said:

What colour space do you guys use is RAW 8 bit reasonable or is RAW 16 preferable? And when do you need to change colour space?

I always use RAW16 which gives the best possible image. I'm considering getting a monochrome camera for their better sensitivity to use alongside the Uranus-C and so I sometimes switch to MONO8 to see what the object might look like in monochrome, but that's the only reason I ever switch from the RAW16 colour space.

13 hours ago, Big Ian 65 said:

Do you guys use region of interest and routinely change the capture area? If so when and why - or is it just a simple matter of framing?

Framing can be dealt with on the night by just zooming in to the part of the image that interests you, and afterwards by cropping. For me, an ROI is only useful when I want to select just a small part of the field of view AND I want to capture frames, as a smaller ROI makes the file size of the captured frames much less. I only do this when observing the Moon and Planets, and then only when I want to capture many frames (1000+) for later post processing. For me, EAA is all about the experience on the night, so I generally try to observe the Moon and Planets live, and that means without live stacking which requires stars to align the frames. So I observe full resolution live frames and just zoom in. The Moon and Planets are not good targets for EAA in my opinion, but I have enjoyed observing the Moon with an IR pass filter and with auto colour balance enabled. The IR pass filter gets rid of a lot of the atmospheric wobble. What I like about it is being able to see the live image on a second monitor and a virtual Moon atlas on the laptop screen, allowing me to identify what I'm observing.

13 hours ago, Big Ian 65 said:

To Bin or not to Bin… thoughts and benefits/downsides?

I'm still investigating the effects of binning, but so far ...

I only use software binning as hardware binning (binning performed in software but on the camera) has unpredictable effects, at least with my Uranus-C.

I uses 2x2 binning when the object is faint and I want to increase the light captured per pixel (by a factor of 4). 2x2 binning with a 4K camera still gives a full HD image but more that 2x2 and I think the resolution is reduced too much, and there is something very odd with 3x3 binning on the Uranus-C camera.

Given that I'm using binning to increase the light captured, I only use sum binning as average binning divides the signal by 4 taking it back to what it was without binning.

I use 2x2 sum binning rarely, usually only when I'm using a Barlow to observe smaller objects and need to compensate for the slower scope configuration that is caused by the Barlow.

13 hours ago, Big Ian 65 said:

how do you ‘nudge’ the black and intermediate level bars in the histogram… I really struggle with the resolution of dragging with the mouse?

If you grab a histogram bar (hold down the left mouse button over it) then move the mouse cursor upwards, outside of the histogram window, then you get fine control of the histogram bar as you move the mouse left and right. The higher up the screen you move the mouse cursor the finer the control.

Unfortunately when you have the image displayed on a second monitor as I do and the histogram fills the main part of the laptop screen, there is no space above it to get this fine control.

 

[Big Ian 65]

2 hours ago, PeterC65 said:

I always use RAW16 which gives the best possible image. I'm considering getting a monochrome camera for their better sensitivity to use alongside the Uranus-C and so I sometimes switch to MONO8 to see what the object might look like in monochrome, but that's the only reason I ever switch from the RAW16 colour space.

Framing can be dealt with on the night by just zooming in to the part of the image that interests you, and afterwards by cropping. For me, an ROI is only useful when I want to select just a small part of the field of view AND I want to capture frames, as a smaller ROI makes the file size of the captured frames much less. I only do this when observing the Moon and Planets, and then only when I want to capture many frames (1000+) for later post processing. For me, EAA is all about the experience on the night, so I generally try to observe the Moon and Planets live, and that means without live stacking which requires stars to align the frames. So I observe full resolution live frames and just zoom in. The Moon and Planets are not good targets for EAA in my opinion, but I have enjoyed observing the Moon with an IR pass filter and with auto colour balance enabled. The IR pass filter gets rid of a lot of the atmospheric wobble. What I like about it is being able to see the live image on a second monitor and a virtual Moon atlas on the laptop screen, allowing me to identify what I'm observing.

I'm still investigating the effects of binning, but so far ...

I only use software binning as hardware binning (binning performed in software but on the camera) has unpredictable effects, at least with my Uranus-C.

I uses 2x2 binning when the object is faint and I want to increase the light captured per pixel (by a factor of 4). 2x2 binning with a 4K camera still gives a full HD image but more that 2x2 and I think the resolution is reduced too much, and there is something very odd with 3x3 binning on the Uranus-C camera.

Given that I'm using binning to increase the light captured, I only use sum binning as average binning divides the signal by 4 taking it back to what it was without binning.

I use 2x2 sum binning rarely, usually only when I'm using a Barlow to observe smaller objects and need to compensate for the slower scope configuration that is caused by the Barlow.

If you grab a histogram bar (hold down the left mouse button over it) then move the mouse cursor upwards, outside of the histogram window, then you get fine control of the histogram bar as you move the mouse left and right. The higher up the screen you move the mouse cursor the finer the control.

Unfortunately when you have the image displayed on a second monitor as I do and the histogram fills the main part of the laptop screen, there is no space above it to get this fine control.

 

Thanks Peter, that explains a lot… I sometimes fall into the trap of thinking that because the software can do something, then I MUST use it… I am coming to the conclusion that for EAA it is best to keep it simple and be more productive at actually observing amazing things… which after all is why we are doing it! The flip side is the unknown and that eureka moment when you enable a setting and all of a sudden your average view becomes a great view! I guess as Pete (Xio1996) told me - sometimes you have to stop faffing and get on with the observing (my words - not his, he is far more eloquent 😉 )

[PeterC65]

1 hour ago, Big Ian 65 said:

I sometimes fall into the trap of thinking that because the software can do something, then I MUST use it… I am coming to the conclusion that for EAA it is best to keep it simple and be more productive at actually observing amazing things… which after all is why we are doing it!

It's worth remembering that while SharpCap is the software tool of choice for EAA (at least when you don't have an ASIair), it has been designed for AP as well and some of its features are aimed at that. That's how I regard the smart histogram function. It suggests the number of frames to capture for example, which I don't find useful for EAA.

I usually observe an object for around 5 minutes, so between 50 - 100 frames at 4s per frame. As you mentioned earlier, it is a case of diminishing returns as you add more frames. After 10 frames each new frame adds 10% more data, after 50 frames it is just 2%. After about 20 frames I find it hard to notice any change with each new frame. I generally watch the image build over 50 frames (3.5 minutes) then move on to another object or try a different filter on the same object. I generally only collect more than 50 frames if the object is showing hints of interesting detail or if I have something else to do (decide which object to observe next for example). If I'm after the detail then I let the live stack run for up to 15 minutes, collecting many more than 50 frames, as that's the only way to get a significant improvement.

I often capture snapshots at different stages of the live stack and when these are compared side by side it is just possible to see the difference made by an extra 10 frames (the sky background darkens and the object detail gets clearer). I almost always keep (as a record) the snapshot taken with the most live stacked frames.