Need help with my step by step instructions please

[Tinker1947]

The speed of SD card won't matter to much as every image saved takes less than a second, and you should have maybe a 20 second gap between images to allow the sensor to cool.....the handset cable is just a normal cable straight through.......

[ianpwilliams]

Would I be looking for a 20-second gap between all types of shots, or just Lights?

[D4N]

Well your darks need to be closely matched to your lights so try and keep them the same interval and temperature.

It will depend a bit on the outside temperature, I find as it gets down to -10 the noise just disappears on its own

Bias and flat are not so temperature dependant as they are so short. Unless you are taking sky flats with a NB filter and they are particularly long.

Sent from my iPad using Tapatalk

[ianpwilliams]

Well your darks need to be closely matched to your lights so try and keep them the same interval and temperature.

It will depend a bit on the outside temperature, I find as it gets down to -10 the noise just disappears on its own

Bias and flat are not so temperature dependant as they are so short. Unless you are taking sky flats with a NB filter and they are particularly long.

Sent from my iPad using Tapatalk

Wow -10, and I thought Edinburgh was cold!

[tingting44]

Yes that's what I've got now too, seems to work pretty well. How long did you make yours? Mine is about 9", which is quite a bit shorter than I could have gone (which was basically the width of the camping mat), but I didn't want to risk it for various reasons. I just hope I didn't make it too short. But the ones I've seen pictures of online seem to be about that length.

mine was the same length as the width too and is ample

[ianpwilliams]

Well your darks need to be closely matched to your lights so try and keep them the same interval and temperature.

It will depend a bit on the outside temperature, I find as it gets down to -10 the noise just disappears on its own

Bias and flat are not so temperature dependant as they are so short. Unless you are taking sky flats with a NB filter and they are particularly long.

Sent from my iPad using Tapatalk

I think my Lights for both sessions and my Darks for the second session only had around 5 second intervals, which probably didn't help matters then. I'll go for 20-second intervals for my Lights and Darks from now on.

For the Bias and Flats, would 5 seconds be enough do you think? I've been taking loads of Bias shots in the flat, and they have all been 5 second intervals. Is that enough? I could do them again with bigger intervals if necessary, and make a point of going for bigger intervals for my flats in the future too. I suppose that seeing as I'll be doing my Flats during the session anyway, I might as well make them 20 second intervals too, even though it's a right pain holding the laptop up to the scope as it is!

[ianpwilliams]

Looks like clear skies for 55.96, -3.15 tomorrow evening:

http://clearoutside.com/forecast/55.96/-3.15?view=midday

Do you think it'd be worth trying a session 7pm-10pm based on that data? I'm a bit paranoid about the weather now following my last session, where there was clearly hidden weather issues

[D4N]

I don't think it's worth having long intervals between bias and flat frames, they don't have much temperature sensitive noise in them. I just set the interval long enough for the file to be transferred to the laptop so the buffer doesn't fill up.

TSED70Q, iOptron Smart EQ pro, ASI-120MM, Finepix S5 pro.

[ianpwilliams]

I don't think it's worth having long intervals between bias and flat frames, they don't have much temperature sensitive noise in them. I just set the interval long enough for the file to be transferred to the laptop so the buffer doesn't fill up.

TSED70Q, iOptron Smart EQ pro, ASI-120MM, Finepix S5 pro.

Good to know, glad I didn't waste all that time taking those Bias frames then!

[ianpwilliams]

I was hoping to try practicing Flats indoors, recreating the laptop and A4 paper up against the scope, do that I can work out how many pieces of paper I'll need in order to get the histogram right so I don't have to experiment outside. Would this work in theory?

And if I upload a single Flat from the other night, would someone be able to have a look at it? I know that Carole thought that the master looked good, but I'm sure the peak was off the scale on the histogram, and I thought it needed to be one third height.

[Thalestris24]

_{I was hoping to try practicing Flats indoors, recreating the laptop and A4 paper up against the scope, do that I can work out how many pieces of paper I'll need in order to get the histogram right so I don't have to experiment outside. Would this work in theory?}

And if I upload a single Flat from the other night, would someone be able to have a look at it? I know that Carole thought that the master looked good, but I'm sure the peak was off the scale on the histogram, and I thought it needed to be one third height.

The (EOS) histogram peak should be about 1/3 of the way in from the left i.e. more dark than light

Louise

[ianpwilliams]

Ah ok. I did think that at one point, which is why I went ahead with them. So does that mean that it doesn't matter if the peak went off the top of the scale at the top? Is that what happens anyway?

I need to learn more about how to read my histograms!

[ianpwilliams]

Here is one of my Flats from the other night in GIMPShop, with the histogram displayed. Do you think that is going to be ok with during my next session? I can always add another piece of paper!

[Thalestris24]

Hi

That looks ok - maybe a wee bit overexposed but will probably be fine.

Here's one of mine with screen capture of APT:

Louise

Edit: thinking about it, not sure about using Gimp as it's only 8 bit so not using the right dynamic range really.

Edit2: You need to be looking at the raw image - definitely not a jpeg!

[ianpwilliams]

It's not a RAW, but it's not a JPEG either. I couldn't find a way to view the histogram of the RAW in Digital Photo Professional, so I exported the RAW as a TIFF and opened it in GIMP. Can't think of another way to check it really, other than copying it back to the SD card and taking a photo of the histogram on the camera...

[lensman57]

here

Hi

That looks ok - maybe a wee bit overexposed but will probably be fine.

Here's one of mine with screen capture of APT:

Histo_Flat.JPG

Louise

Edit: thinking about it, not sure about using Gimp as it's only 8 bit so not using the right dynamic range really.

Edit2: You need to be looking at the raw image - definitely not a jpeg!

I have read somewhere that the camera should be set to +2EV in AV mode for taking flats. If I find the article again I will post the link.

A.G

[Thalestris24]

I have read somewhere that the camera should be set to +2EV in AV mode for taking flats. If I find the article again I will post the link.

A.G

I have to do mine in manual mode as it's a full-spectrum modded one...

Louise

[ianpwilliams]

That's reminded me. There are various other settings on my camera which seem to exist even in Manual mode, such as Auto White Balance etc, and I was wondering if I needed to adjust any of these?

[Thalestris24]

It's not a RAW, but it's not a JPEG either. I couldn't find a way to view the histogram of the RAW in Digital Photo Professional, so I exported the RAW as a TIFF and opened it in GIMP. Can't think of another way to check it really, other than copying it back to the SD card and taking a photo of the histogram on the camera...

You can select view -> tool palette in Digital Photo Prpfessional

[D4N]

A lot of those settings like white balance don't effect the raw data, they are just appended to the file for display.

Gimp 2.9 is ok for processing but as Thalestris24 states earlier versions are 8 bit so you will lose a lot of data using it to process.

TSED70Q, iOptron Smart EQ pro, ASI-120MM, Finepix S5 pro.

[ianpwilliams]

You can select view -> tool palette in Digital Photo Prpfessional

Didn't know that, I'll have a look tomorrow.

[ianpwilliams]

A lot of those settings like white balance don't effect the raw data, they are just appended to the file for display.

Gimp 2.9 is ok for processing but as Thalestris24 states earlier versions are 8 bit so you will lose a lot of data using it to process.

TSED70Q, iOptron Smart EQ pro, ASI-120MM, Finepix S5 pro.

Good to know. And yes I'm aware that GIMP isn't really up to the job, which is why I'm going to upgrade my hardware and software in the new year.

Anyway, if it does turn out to be clear skies tomorrow night then I'm going to have a go at the Pleides. Fingers crossed...

[lensman57]

I have to do mine in manual mode as it's a full-spectrum modded one...

Louise

 I have also read that the histograms displayed by the capture software are not accurate as they are based on the 8 bit jpeg conversion of the14 bit raw file, perhaps someone could clarify this. If correct then only the histogram of a processing software could be trusted to show the true values and as I also take flats in manual mode using both APT and Nebulasity then all bets are off. I have also encountered a problem in Nebulasity 3 and my modded Canon 1100d. No matter what value I set the exposure at, the ADU reading of the flats are about 15000 approximately. I wonder if this is a bug in Neb3 or something is not behaving itself. The other point is that the ADU value of the flat for a 14bit DSLR should be about 50% of the max well depth in which case it works out about 8190. Curious affair these flats are.

A.G

[carastro]

I'm a bit puzzled why you can't view your flats in Digital Photo professional (Canon utility suite), these are flats I took back in 2010 with a DSLR and a screen shot of when I was doing them which shows the Flats in RAW format and the histogram:

[Thalestris24]

 I have also read that the histograms displayed by the capture software are not accurate as they are based on the 8 bit jpeg conversion of the14 bit raw file, perhaps someone could clarify this. If correct then only the histogram of a processing software could be trusted to show the true values and as I also take flats in manual mode using both APT and Nebulasity then all bets are off. I have also encountered a problem in Nebulasity 3 and my modded Canon 1100d. No matter what value I set the exposure at, the ADU reading of the flats are about 15000 approximately. I wonder if this is a bug in Neb3 or something is not behaving itself. The other point is that the ADU value of the flat for a 14bit DSLR should be about 50% of the max well depth in which case it works out about 8190. Curious affair these flats are.

A.G

Hi AG

Not sure about that but with APT I suspect you're probably right! Maybe Yoddha / Ivo can confirm... I imagine the same applies to the on-camera histogram. It would be great if APT could display 16bit values and ADUs but in order to do that I Imagine you'd have to set the gain and offset - can't do that with a dslr. However, it does appear to show the histogram peaks at the correct relative position... I don't think I have any software that will display a histogram with ADUs or that shows 65536 (16 bit) levels . The QHY EZCap does display ADU's but only works when capturing i.e. not after the fact with a file. It also only works with certain QHY cameras so no help with dslr images. So maybe it doesn't matter if you use 8-bit software to display the histogram... I've downloaded the latest Gimp build and it does seem to load 16 bit images now

I've converted a Canon RAW flat to 16bit *Tiff and loaded it in Gimp 2.9.1. I don't know my way around Gimp at all but with the histogram display (linear) it has a choice of 'value' or individual R, G, B. I'm presuming 'value' is net luminance. The peak does seem to be at pretty much the same place as the APT display:

Hope that's of some interest/use

Louise