bomberbaz

The images takes by the ZWO setup I use are saved as FITS which are the ones used for processing. Can anyone tell me the reason for it saving all the data duplicate (rather roughly) in jpeg format too?

Basically a stack of 9 images of circa 16-24 seconds plus one at 2 minutes for roughly 4 minutes then a little tweak in gimp, best I could do as sky was a little milky where I am last night. Might have overdone it but limited data.

Managed to bring out the green and there is a sign of some red ionisation running up between 1-2 o'clock.

exquisite Olly, simply sublime details, colour, dusty swirls almost like a swirling river.

My effort via eVscope. Not had chance to tidy it up though. Sorry

5 hours ago, Elp said:

I have used all sorts of gain, and find rarely does it make an iota of difference to any of the images other than with a 294 camera sensor, there's always noise which needs to be post processed out with some sort of software filter operation. Adding more hours on the target makes more difference.

Well what I am doing at the moment is following the science. Up until now I have worked on the basis of longer exposures/dark site & shorter exposures where there is LP and no idea as to best cooling if I am honest.

So I am gathering data on objects I already data of from previous projects but this time I will get my subs using a more science based approach and see how things compare, I am currently gathering on the iris nebula and will run a side by side, see where that takes me.

Steve

15 hours ago, rickwayne said:

IIRC others have commented that ASIAir does not provide a user-settable offset.

Thanks for that, it was as I suspected. It must be algorhythm controlled somehow!

1 hour ago, AstroMuni said:

The way I went about this is look at the data provided by ZWO on my camera. In your case https://www.firstlightoptics.com/zwo-cameras/zwo-asi-183mc-pro-usb-3-cooled-colour-camera.html the graph says unity gain is at 120 and read noise drops to 2 at 150 gain and dynamic range is 10ish so not too bad - so thats the gain I would aim for.

In terms of cooling the dark current drops very well beyond -10 so you could set to that level of cooling.

I set my Offset to 70 for my ASI533mc pro in Ekos but cant comment about ASIAir or Sharpcap. Here is a good discussion on this topic of offsets https://www.cloudynights.com/topic/542048-gain-and-offset-settings-for-zwo-cameras/

You could also work it out yourself - once you have your gain and exposure chosen, capture some dark frames with the selected gain/exposure. Adjust the offset to make sure that the peak in the image histogram is clearly separated from the left hand side of the graph.
 

HTH

I have since posting found out that the gain for mine is 115 according to sharpcap tools although I want to recheck that under darker skies. Also I have been given info from ZWO which suggests -15 is the cooling to aim for so only 5 degrees from the -10.

Thanks for taking time to reply though and tbf, I wouldn't be far wrong had I used those figures of yours anyway.

30 minutes ago, andrew s said:

Not sure what you mean but see this:

"

Offset is exactly as its name implies: it is an offset that is applied to the histogram curve which shifts it – offsets it – farther to the right on the histogram by some amount. This ensures that the minimum value that any pixel might record is not underexposed and is therefore clipped in the blacks. This is especially important in astrophotography because of the nature of it – some pixels on the sensor might be positioned to look at purely dark space and therefore will collect far, far fewer photons than pixels that has the light from a star, nebula, or other light-producing object pouring into it.

Avoiding clipped-black pixels means that you avoid having pixels with insufficient signal or, worse, a value of 0. This is the opposite predicament of an image that has pixels that are clipped-white. Both types of clipped pixels effectively have no data that can be meaningfully acted upon during processing."

 

From here https://daleghent.com/2020/08/understanding-camera-offset

Regards Andrew 

I mean there is nothing called offset in the zwo settings andrew, see this How do I change offset - SharpCap Forums

It was hard finding this information, I had to look all over until I found this.

However I still don't see a brightness setting in the ASI app, I will have to carry on looking. 

cheers for the explanation though.

steve

I notice there is no place in the ASIPLUS schedule for darkflats, to date I have always just used the bias section to make them, renamed them as darkflats and used as named.  However a question popped into my head today as a result of a little research I am doing and that is, do the latest ZWO cameras (mine is 183mc pro) need dark flats or should I revert to just bias along with standard darks and flats?

cheers all

steve

With ZWO camera's, OFFSET is simply brightness. Took some finding.

50 minutes ago, drjolo said:

The amount of the dark (thermal) signal  depends on the total integration time. It does not matter if you collect 1000x15s or 15x1000s of frames - you will collect the same amount of thermal noise. The only way to limit it is to cool the chip. So you may use the same temperature preset as before. Each 6-7C of temperature difference doubles the thermal signal. Thermal noise in modern cameras is not a big issue, unless you reach some larger positive values (like +10C or more), or you capture data with narrowband filters. 

As for 2-4 seconds subframes it was probably calculated for light polluted sky, so for your specific case the read noise amount becomes not significant when you use 2-4s subframes, or longer. You can make subframes longer, and then you need to consider the pixel capacity (so they will be saturated) and your tracking/guiding capabilities.  Collecting few hours of frames in 2-4s subframes probably is not reasonable, unless you would like to do a kind of lucky imaging and then select best frames to stack this selection into better resolved final image. 

PS - offset is as far as I remember called "black level" in SharpCap currently

Actually that makes perfect sense. End picture is a result of lots of stacked data, so thermal will be the same. I shall maintain things as they have always been.

Thanks for the tip ref offset but there is no control for black level either. I should point out that A. I am on V4 sharpcap, recentl;y released and B. there is no mention of an offset value on the sensor analysis report and that there is no black level in ASIAIR either.

Hello all.

I am currently in the process of gathering data on my camera's (ZWO 183MC Pro) optimum settings for data gathering.  Following on from watching the excellent video of Dr Robin Glover (Link Dr Robin Glover ), I decided to make the very modest investment into Sharpcap Pro again, (previous subscription expired) this so I can use the tools available in the programme, these being sensor analysis and smart histogram. 

Following this I discovered to my surprise I had been vastly over doing it in terms of exposure length, especially from my home.  I knew they were a little overdone following watching the video link above, but not to the extents of what it was.

The actual result wasn't realistic in terms of data gathering (2-4 seconds), however previous times of 2 minutes at home can comfortably be reduced to 12-15 seconds, any less and the number of subs for a five hours session will just become very silly. I also found my optimum unity gain should be slightly lower (-4) but I will leave it unchanged to the ZWO default. I have yet to settle on the final sub setting from home but I can't imagine it will change much from said 12-15.

So whilst on with this research of optimum settings, I started to dig into things further and keep coming across the use of offset during the taking of subs to avoid clipping of data but cannot seem to find settings for the alteration of offset either in sharpcap or ASIAir+, am I missing something very simple here?  I am actually wondering if this has been automated in some sort of algorythm, can anyone help?

On cooling there appears to be nothing in sharpcap or the wider forums that advises the best setting of this, (maybe missing this too but it is getting quite overwhelming hence this post) but I am thinking that for 15 second subs, cooling will not be such an issue anyway!

Cheers for any advice on this matter.

Steve

Cracker that, lovely nebulosity.

What skies were you under, also be interested to discuss your process as we use the same image processing software if you don't mind?

Added some new data to that I already had for both these objects but I think I am getting less improvement on the data as time goes by as you would expect.  I have a plan to maybe increase returns without significantly increasing imaging time but don't know how well this works. Got the info from a youtube video, anyway, I digress.

Here are my last effort from 2022 and from additional data added .

&

Here is the Deer Lick group and Stephan's, the image difference isn't significant but it just seems a little tidier.

&

Decided to have a go out to my local dark site tonight, other than the sub zero temperatures the conditions were very good.  The drive there was uneventful other than the last 5 miles behind the slowest taxi driver in the world.

So got there and it started within minutes, nothing major but a culmination of many little bits.

Lifted the hatch and reached for my bag of bits, grabbed the head torch and my diffuser fell off it onto the frozen floor, could I find it, grrrrr!

Started setting up the dob, missed off one of the key parts of this operation, namely use the level to get it reasonably so, this came back to haunt me later.

Only after setting the dob up did I realise it was doing a passable imitation of a certain building in Pisa. This in turn created havoc with alignment until I got to grips with the adjustment needed to allow for the "tilt" in the scope.

I eventually managed a decent alignment  so onto observing. I wanted to do a shootout comparison with my UHC vs OIII using my new 20mm plossl, only thing was I left the plossl at home along with a zoom I had plans for later.

Also all this additional messing around meant my first DSO's had dropped to low to be available for viewing so that also spoilt part of my plans.

Shortly after this the dob lost balance, I managed to save a wholesale disaster and it only partially fell but the mirror box partly slipped from the rocker.  No major damage but the slider strip on the rocker had a slight crimp in it, it is already nearly gone from use.

But I did have to remove the top secondary box to realign the rocker and primary mirror box. After this I put the secondary box back on, forgot to tighten the bolts up and the box nearly fell off. 

Shortly after an eyeguard extender pinged off an eyepiece and disappeared into the dark. Torch out and I found it, along with the lost diffuser from the start so one ray of light. 

Packing up I lost the cover from the focuser to cap it off, pun intended.

I don't really have anything to report in terms of viewing although I did spot  the galactic wanderer for the first time but nothing much to report about in what I saw, just something I had on my to get list. 

The best thing to report on was my new cold weather gear performed well so through all the strife at least I wasn't cold.  I have been fed up either too cold or barely able to move because of too much gear. So I bought new thermal vest/long johns, a pair of TOG 24 waterproof leggings, heated body warmer and a new TOG24 jacket which is superb.

Anyway, all in, a pretty rubbish night but at least not cold.

On 21/12/2022 at 15:50, AstroMuni said:

Have you seen this? I know its not about DSLRs but it will give you a bit of background on the topic as the sensors are pretty much the same on both DSLR & Astrocams.

This is a very good video, some very useful tips there. Thnkas for posting up

I have been looking at the 23mm on and off for a while and being honest struggle with my inner EP argument to find a suitable rationale to buy one.

The exit pupil argument doesn't hold water as it is far to close to the APM 24 (4.7 vs 4.9), extra FOV is 20% greater than said APM but locking up the best part of £500 for a line filter eyepiece (the APM's main use) is not selling it. Plus the fact I really do like using the APM 24, probably the easiest to get on with EP I have.

I will wait to run a comparison with 24mm APM if one comes along via a star party and see if the view persuades otherwise. 

Happy viewing folks. 

13 hours ago, leo82 said:

I've come to use my az gti for the first time in a while. It won't align with any stars I try to align it with, brightest star or North level alignment. It's always about 4-5 degrees off target.

I only use it in alt az with no eq wedge.

I have tried using synscan and synscan Pro apps.

I have updated the mount to the current firmware.

I have put fresh duracell batteries in. 

When I first set it up, I make sure I'm pointing north by manually finding polaris in the telescope. I then lower the telescope so it's lying horizontal.

I then turn the mount on and try to align with polaris. It's always off target so I use the app buttons to centre it. Then off to second star. The same thing happens so I centre it up again and pick a target I want to observe. Again it's way off target.

I could get closer to an unknown manually than by using goto, which shouldn't happen.

I must be doing something wrong, I just don't know what?

Any help would be greatly appreciated.

Sorry if this has been answered already but don't you need to have the scope to the left hand side of the mount during point level north?

Also re-install the software from the link below rather than playstore. Apparently it can glitch in download and install from playstore.

https://www.skywatcher.com/download/software/synscan-app/

TBF I stopped doing point level north alignment, pain in the proverbial. 

Some new thermals, great price at a 5er each garment. The old ones had got ermm, a little small 😅

Very sad news, his absense had been noted by a few. RIP John, a very well liked and respected member

1 hour ago, michael.h.f.wilkinson said:

I noticed the skies were showing some large clear patches early this morning, so despite moonlight I trotted out the Helios LightQuest 16x80 mm bins and had a look. The comet had moved significantly since my last sighting, so it took a while to get to the right spot, at which point clouds interfered. I went back to making breakfast, but kept an eye on the weather, and at 7:15 I spotted another large clear patch. This time I could clearly spot the comet, showing up as a much more elongated patch of fuzz. The dust tail was clearly visible, but no hint of the ion tail. No chance of imaging, of course, but at least I have had another sighting of this comet

I admire your dedication michael, these days there is usually only one 7 oclock in my day

This came up in a group I follow, so definately not mine. 

Hubble claims the bragging rights but of all the images I have seen recently, this is the biggest standout to me since the James Webb reveal from last year, seems almost CGI. Anyway, enjoy.

I have 6.5 diopters of astigmatism, I do not really like using glasses, never found myself comforatable with them, spoils the experience.

Solution A. I use a televue dioptrix down to 24mm when using the dob, beyond that I observe without glasses.  I know the view is affected by my astigmatism until I get down to lower exit pupils, but I prefer that to glasses. With my frac I never observe with glasses as the starting exit pupil is 2mm.

Solution B. Toric contact lens, I have some waiting to be used with the dob, just not tried them yet. I did use them last year on my giant bins and found them quite easy to get on with so I reckon they should be fine.

3 hours ago, josefk said:

Very nice. Unlike Steve I’ve failed to detect this (I think twice) this year visually. I’n reality i’m underpowered (don’t have enough aperture) for it so it is lovely to see your image of it this morning. 👍🏼

Think you might be right regarding the aperture or lack thereof. I was using the 350Pro at B2 skies and only just managed it although it was fully resolved. 

I reckon your classic cass could do it but you would benefit adding a reducer to it with a UHC filter and keep your exit pupil quite large. Oh and very, very dark skies 😉 

That's decent considering how big and diffuse it is also considering your conditions. 

I visually bagged this early last year, extremely difficult to get and certainly nothing like the detail you managed here. 

Nice to be re-introduced albeit virtually.

3 hours ago, PeterStudz said:

Well, I do that and really it goes without saying. But some people simply have zero interest in visual and AP. My wife is like that. She’s seen the moon and Saturn but from what I can remember that’s it. 

 

Sounds exactly the same as my wife, actually as you alluded to, the complete lack of interest is something of a blessing in disguise. This discourages her having any interest in costs. For example all eyepieces cost in the region of 20-80 quid and telescopes a few hundred. Actually the telescope one isn't wrong, just not specifically correct either. 😉