camera dramarama

[TiffsAndAstro]

my tldr from that video. please point out anything i misunderstood

1 longer exposures gain more benefits as bortle number gets lower. 

2 rather than using unity gain as a default, use it to (ideally) just fill the well depth and so preserve as much dynamic range as possible.

3 balance the above with you gear's ability to do longer exposures and things like wind and aircraft. and guiding blips.

4 somehow magically track snr as you image so as to see when diminishing gains start to occur and can at least make a slightly informed descision on when to stop.

5 don't bother cooling camera to minus one billion degrees. cool it enough so that it is a stable temperature, above freezing to avoid frosting and low enough that dark noise (i think it is) is trivial compared to light pollution noise.

6 use same gain for flats as lights cos why not 'just in case it does matter'

7 close your eyes in a very dark room and those flashes you occasionally see are actually cosmic rays hitting your retinas  (ok i just added this to see if anyone read this far)

ty again for linking that most excellent video.

Edited June 14 by TiffsAndAstro

[900SL]

8 hours ago, TiffsAndAstro said:

the lower your bortle,  the better it is to do longer exposures it seems. or at least lower bortle gets the most out of longer exposures?

Yes. longer exposures in lower bortle. One reason I like the AsiAir in the field is that you can see the ADU values for each sub (max, min, mean etc) so you can quickly see if your exposure is in the right ball park. Nina will do the same

You've not seen anything like the Saudi desert night sky. I've been to bortle 2 locations several times, and if the seeing and dust allows, it is a diamond strewn velvet carpet from horizon to horizon.  There's so many stars it is difficult to make out constellations. And I would expose for minutes with a DSLR to get the histogram off the left hand side. The SNR per sub is waaay better than back in B5 or B7 skies

[900SL]

11 hours ago, TiffsAndAstro said:

Snip..

i lied. a better way to explain my question might be. even in bortal 9, the photons per sec from light pollution cannot be greater than the photons per second from a target source, else the target source could never be imaged. this i guess isn't true for the specific wavelengths used in narrow band (as light pollution is not strong in those wavelengths), but might be in broadband?

I may be wrong here, but photon flux from LP can, and usually is higher than flux from target, for higher bortle skies.

This is a crap analogy, but the object signal is, in effect, riding over or modulated on a carrier wave of LP. Yes, I know that's not correct You remove the LP signal during processing (but not the LP noise.. that's where stacking comes in, and why lower bortle needs less total integration))

[TiffsAndAstro]

44 minutes ago, 900SL said:

I may be wrong here, but photon flux from LP can, and usually is higher than flux from target, for higher bortle skies.

This is a crap analogy, but the object signal is, in effect, riding over or modulated on a carrier wave of LP. Yes, I know that's not correct You remove the LP signal during processing (but not the LP noise.. that's where stacking comes in, and why lower bortle needs less total integration))

Cheers it's obviously possible as people make great images on higher bottles than me, but maybe only via narrow band. Still seems to be impossible magic to me right now

[TiffsAndAstro]

7 hours ago, 900SL said:

Yes. longer exposures in lower bortle. One reason I like the AsiAir in the field is that you can see the ADU values for each sub (max, min, mean etc) so you can quickly see if your exposure is in the right ball park. Nina will do the same

You've not seen anything like the Saudi desert night sky. I've been to bortle 2 locations several times, and if the seeing and dust allows, it is a diamond strewn velvet carpet from horizon to horizon.  There's so many stars it is difficult to make out constellations. And I would expose for minutes with a DSLR to get the histogram off the left hand side. The SNR per sub is waaay better than back in B5 or B7 skies

I've never seen the milky way and that makes me sad

but there's still stuff I can do, even in bortle6 which it seems is not that bad.

huh max, min, mean are for ADU? i thought they were something else, but not sure what that something else was, lol. higher is better? at least i have a term i can google for now ty lol. 

Seems lower is better and it's relative for each set up but, I can keep an eye on it in future. Better than waiting for phd2's bonging of cloud audio.

I did find a tool called Fits Liberator which looks handy. Gives adu for previous taken images.

Edited June 14 by TiffsAndAstro

[TiffsAndAstro]

well, its done. tec cooled imx533, plus filter drawer plus uv/ir cut filter delivered and customs/taxes all covered (i guess we'll see) for £514. which seems a good deal. 

they have another 'flash sale' on reduced the price by about another £60.

[Vroobel]

Already purchased? 

[TiffsAndAstro]

6 minutes ago, Vroobel said:

Already purchased? 

yup, got confirmation email. ill do an unboxing, first light and review video lol  in 9 to 15 days including custom clearance....

 

Edited June 14 by TiffsAndAstro

[Vroobel]

Good choice! 👍

Regarding the rotator, are you looking for any manual one, eg. M48/M48? 

[TiffsAndAstro]

5 minutes ago, Vroobel said:

Good choice! 👍

Regarding the rotator, are you looking for any manual one, eg. M48/M48? 

yes manual. i did order one origionally from flo way back, but there seemed no way to actually attach it to my optical train. i'll ask them again once i get camera set up and working as i have a feeling ill need at least some other adapters/spacers. it was only about £20. sent it back with my first scope (the one with the welded on dew shield).

i think i'd like a nicer rotator at least with markings on it for orientation. looks more pro too. i think i can use it and the filter drawer to contribute to back spacing without using it all up. but who knows, lol?

for £16 i wanted this https://www.svbony.com/sv210-caa-camera-angle-adjuster-for-sv550-80f6/#W9162A but it seemed a struggle to work out how/if it would fit my gear.

amd i assume M48 but all those Ms really confuse me as a beginner. don't even ask about the M4 screws i bought on ebay. god knows what they really are.

Edited June 14 by TiffsAndAstro

[DaveS]

With a square sensor, once you have it aligned orthogonal there's no need to rotate it.

[TiffsAndAstro]

12 minutes ago, DaveS said:

With a square sensor, once you have it aligned orthogonal there's no need to rotate it.

that would be nice. but, orthogonal to what? currently with my stuff screwed in finger tight my dslr is where it is, if that makes sense. i don't think i could make it orthogonal to anything. 

im hoping i won't need to do anything from this random link i found:

http://www.company7.com/library/techin/orthogonality.html

i haven't had to, so far.

Edited June 14 by TiffsAndAstro

[900SL]

5 hours ago, TiffsAndAstro said:

I've never seen the milky way and that makes me sad

but there's still stuff I can do, even in bortle6 which it seems is not that bad.

huh max, min, mean are for ADU? i thought they were something else, but not sure what that something else was, lol. higher is better? at least i have a term i can google for now ty lol. 

This series might be useful, part 1 of several here:

https://cloudbreakoptics.com/blogs/news/astrophotography-pixel-by-pixel-part-1

 

[Vroobel]

1 minute ago, 900SL said:

This series might be useful, part 1 of several here:

https://cloudbreakoptics.com/blogs/news/astrophotography-pixel-by-pixel-part-1

 

Yes, it is, indeed. 

[TiffsAndAstro]

24 minutes ago, 900SL said:

This series might be useful, part 1 of several here:

https://cloudbreakoptics.com/blogs/news/astrophotography-pixel-by-pixel-part-1

 

Will have a look ty

[TiffsAndAstro]

2 hours ago, Vroobel said:

Good choice! 👍

Regarding the rotator, are you looking for any manual one, eg. M48/M48? 

Ty but I will need to learn 2 or 3 panel mosaics via free tools just for m31. An old unsupported panarama stitching tool from Microsoft called ice might do the trick, apparently it can stick linear data together. Gradients might be an issue then, but I can experiment with removing them first.

If there is a gap in clouds tonight I might try a test and see.

I say three so I can have one for center of m31 and then one either side, so no chance of a seam through the middle.

Edited June 14 by TiffsAndAstro

[Elp]

36 minutes ago, TiffsAndAstro said:

ice

Use this with caution, I don't see how it has the "intelligence" to stitch an astro image together even when you order the layout of the images prior to doing the stitching. When I tried it with a nine panel mosaic (3 x 3), the output certainly looked impressive, but I had manually aligned it prior so I could compare the result. ICE had deleted degrees of the sky and even complete galaxies, so for me it was absolutely no good (and I'd also be cautious with any tool which doesn't have some sort of plate solving database within to actually know what it's looking at before stitching).

[TiffsAndAstro]

51 minutes ago, Elp said:

Use this with caution, I don't see how it has the "intelligence" to stitch an astro image together even when you order the layout of the images prior to doing the stitching. When I tried it with a nine panel mosaic (3 x 3), the output certainly looked impressive, but I had manually aligned it prior so I could compare the result. ICE had deleted degrees of the sky and even complete galaxies, so for me it was absolutely no good (and I'd also be cautious with any tool which doesn't have some sort of plate solving database within to actually know what it's looking at before stitching).

Not even installed it yet but it's the only free option I've found so far

I'll keeping looking around but I doubt there's a free tool that includes plate solving. 

appreciate the warning though. If I get half a clear sky I can try out and see with little time wasted with this weather.

[Elp]

I think ImageJ might do it (get the Fiji install), I tried to do it briefly but didn't get the right result with it.

It doesn't really take long to do it manually as long as you're good at pattern recognition. The longer part is getting lighting/exposure blends right between panels.

[TiffsAndAstro]

2 minutes ago, Elp said:

I think ImageJ might do it (get the Fiji install), I tried to do it briefly but didn't get the right result with it.

It doesn't really take long to do it manually as long as you're good at pattern recognition. The longer part is getting lighting/exposure blends right between panels.

Manually? In gimp maybe? I was thinking that but not sure (yet) how I'd deal with only showing one panels overlap, if that makes sense?

I was thinking just aligning by eye in gimp, but I think of a lot of things that are trickier than I initially think

my plan is to align then gradient removal or gradient remove from each panel then align.

I Was also thinking of taking one sub of one panel, then one on next panel etc. sort of to even out gradients and possibly not dither? 

[Elp]

If you're doing deep sky you'll still need to do the same processes (dithering, PP gradient removal), then drag all the images into the same file, make the canvas larger (you can do it in PS so I expect gimp to be the same) then move, rotate align whilst the working layer is slightly transparent so you can align to the bottom layer. Some very slight scaling might be needed too to get them to align. You want sufficient overlap so if theres any edge distortion from your optics you're good to mask it out when you blend each panel/layer together. I'd get some good deep sky images doing first before even contemplating mosaics.

[TiffsAndAstro]

31 minutes ago, Elp said:

If you're doing deep sky you'll still need to do the same processes (dithering, PP gradient removal), then drag all the images into the same file, make the canvas larger (you can do it in PS so I expect gimp to be the same) then move, rotate align whilst the working layer is slightly transparent so you can align to the bottom layer. Some very slight scaling might be needed too to get them to align. You want sufficient overlap so if theres any edge distortion from your optics you're good to mask it out when you blend each panel/layer together. I'd get some good deep sky images doing first before even contemplating mosaics.

Hadn't even considered edge of field issues of which I'm likely to have at least some. 

I'll definitely concentrate on non mosaics if my new camera turns up, but I'll try and take some test data to practice with whole I wait just 9 to 15 days

M31 won't be high enough to image for me for at least a couple of months. I could always swap back to my dslr for m31 if needed, I hope.

[Elp]

I was going to suggest if you want to try mosaic just use the dslr and take short 5-10s exposures, depending on the lens you can also test overlap percentages and then try combining.

[TiffsAndAstro]

28 minutes ago, Elp said:

I was going to suggest if you want to try mosaic just use the dslr and take short 5-10s exposures, depending on the lens you can also test overlap percentages and then try combining.

Lol I'd need at least 2 or even 3 minutes of clear sky for that ;(

[TiffsAndAstro]

ø2.1 x ø5.5 x 12mm center positive dc jack is what flo website says about my mount power supply cable. i have no idea if my camera, if it ever arrives includes a powersupply, but either way i'd like to use a splitter from it - one split going to the mount and the other via a detachable extension cable to my camera.

can i just search on ebay for a cheapo version that matches the "ø2.1 x ø5.5 x 12mm center positive dc" ? i've seen a few already. also seems i can get a right angled adapter as i don't like using a straight one it seems to put unessecery stress on the power in socket even though i use some velco to take the weight off.