Revs

3 minutes ago, symmetal said:

By USB Speed do you mean using USB2 vs USB3 or the USB Speed setting in the driver.

The latest cameras use memory in the camera to read out and store the images quickly before transferring them to your PC via USB. Earlier cameras without this memory had issues with excessive amp glow using USB2, mainly with short exposure imaging. So now USB2 just means it takes longer to download the image and doesn't affect the quality. The USB speed setting in the driver is to avoid sending the data too fast that the PC can't cope. If set too high you may get dropped frames or no image at all.

As many CMOS camera have 'amp-glow', (the later more expensive ones don't) bias frames are not very useful as you need to use darks to calibrate your lights and flats. The darks already contain the bias signal so using darks takes care of bias and amp-glow.

The position of the peaks in the histogram don't need to match the lights. The light peaks will always be higher than the darks as extra light is entering the camera causing the peak to move to the right with increasing exposure.

The offset needs to be the same setting for all your images, lights, darks, flats, and bias (if used). The offset value used is to avoid getting any image values at zero which means clipped data. If different offset values are used then you can't calibrate the data correctly.

Alan 

Thanks for that Alan, much appreciated

13 minutes ago, kirkster501 said:

Why should the USB speed cause AMP glow?  USB is a digital medium to connect two devices together.  It should have no effect at all on the media being transferred between the two devices.

OK just confirmed it makes no difference. Tried speed of 40 compared to 80 and they're just the same. So USB speed is sumply to get the transfer done faster. Must have mis-read or mis-understood what I was reading.

4 minutes ago, kirkster501 said:

Why should the USB speed cause AMP glow?  USB is a digital medium to connect two devices together.  It should have no effect at all on the media being transferred between the two devices.

I'm probably wrong but I'm sure a read that amp glow was caused during the transfer of data, so the faster you can get that done the less amp glow.

4 minutes ago, Astrosharkey said:

I keep everything the same for all settings, and use -10c for all my imaging.  When I make a library i take 50 frames with the cap on in a dark place, all the same cables in the same ports and then when i process my first image with the darks let DSS stack them into a master frame.  I have a set for 350 and 500 gain (but that is my camera) and a range of exposure times that I might use.

Cheers. Did you spend much time finding a good offset setting for each gain setting or just go for a 'safe' amount for both?

Hi. After some saving I've taken the plunge and purchased a cold CMOS camera, the ZWO ASI294MC Pro. I've got the day off and I'm using this time to collect some dark/bias calibration frames. But I have some questions. I understand that the temperature and gain have to be the same for all frames and that exposure times of the darks and lights needs to match, but...

Which of following camera settings used to take darks/bias frames have to match the settings used for light frames...

USB speed - My understanding is slower means more amp glow, so will have to be the same, at least on the darks, right..?

Offset - do the positions of the peaks of the darks/bias frame have to be in the same place on the histogram as the lights?

Any input appreciated 🙂 also any other tips for a newby more than welcome!

Pretty sure this is a good one..

That has knocked a lot of the medium brightnees stars down a lot though, kinda lost it's twinkle.

From what I remember, he selected the brightest areas using a FWHM selection method, deselected the bits he didn't want to effect and feathered the selection that were left. Turn that in to a mask and adjusted the curves, etc. Then blended the layer in using opacity. I'll try and find the vid...

32 minutes ago, tooth_dr said:

do you make stars in separate channels smaller or in the combined RGB data etc

From what I've seen it would be tweaked at any stage of the PP as desired, so probably both. This guy has a lot of good vids..

AstroBackyard.. https://www.youtube.com/playlist?list=PLt97PtQt5dJEUdzqgBIJv-xs8anU7F6D-

But there are dozens of great astro related channels

3 minutes ago, tooth_dr said:

Great observations, thanks! I’m not sure how to go about making the stars smaller. I didn’t control them earlier on. I also don’t know the process of making them smaller when combining separate LRGB data - do you make stars in separate channels smaller or in the combined RGB data etc. 
The big blue stars dominate the image in my eyes. However this is a consistent thing in all my recent images so it’s either a) data capture issue or b) processing issue or both. Given than most things can corrected in processing, hopefully I can learn WHEN and HOW to control the stars 

It doesn't strike me as an 'issue' as such, more just that the blue ones are the brightest and blow out the most (I'm sure there's a correct term for this but I don't know it), so they do dominate.

I'm just getting back in to astro after a long time away and I'm using Photoshop for the first time as of last week. But I've watched a lot of tutorials on YouTube in the last week and am literally just learning about shrinking stars using masks, etc now. So I can't really help much but there are a lot of tutorials and PP walk-throughs on YT. I also picked up the Astro Photography Tool plugin for Ps which does a lot of this using 'actions' in seconds... once you know how to use them 😆

The reason I say that is that the blacks are really black and the stars have less colour than in the first one, suggesting clipping.

As you say, maybe half way. But the first one looks good to me

BTW I'm not professing to be an expert, I'm still very much learning, especially the PP side.

V1 is very nice but V2, wow that's really nice. So many galaxies, they're everywhere! The colours are lovely, especially the stars.

I'm looking on an OLED and the colour balance looks fine to me mate. Though there are a lot of big blue stars in that image and they kinda effect the overall tone. But instead of adjusting the colour I might have a go at tightening up just the big blue ones a touch. It might just make the difference.

BTW I'm no expert, just throwing ideas out there

On second thoughts maybe a teeeeeeny bit more red..? I'm seeing green as much as blue.

I do prefer a softer image. But I didn't used to so I know where you're coming from

The first one is nice, good colour and detail.

If you don't mind me saying; the second one is over-stretched and you've lost detail in both the dark areas and the core/stars. I don't think the extra sharpness gained is worth it. The first looks much more natural imo

Might not be what you intended but it looks gorgeous nonetheless. Good stuff 👍

Thanks guys

Jules, not setup at Digley res before, lovely spot though. Was thinking a little further along the road and a little higher; Holme Moss, 527m asl. Prolly a bit breezy up there though.

Hi Guys and Gals.... I'm back!

I thought I'd better reintroduce myself as I haven't posted for a such long time, going on 8 years I think. I hope everyone's doing well in these weird times. With all the extra time I've had I found myself watching astro vids on YouTube. Next thing you know I'm dusting off my scopes and reacquainting myself with the HEQ5. I've had a couple of nights out with the 10" dob hoping to see some planets but only Venus and the Moon could be found, but it was so nice to see them again.

I decided it was time to retire my slow-as-hell 12 year old astro notebook and pickup something a lot newer and faster. Then had to re-learn the ASCOM install process and figure out how to get the old QHY5 to talk to Windows 10 (x64). I was struggling, I had almost given up and was looking at QHY5Lii's, but I found the info/link I needed here, got the right drivers installed and got it working again, which made my day

The only issue now is that I'm in a very light polluted area and don't wanna get in trouble by travelling to darker skies.

Anyway, see you in the forums, cheers!

Just found out very sad news. We've lost one of our few true national treasures. RIP Patrick, you'll be well remembered.

My last picture was a bit blurry plus i now have a splash of green in the case now, i added the 18mm BGO

Nice one Jules. I wouldn't mine a look through the 18BGO next time I see you

Wow that's a lot of green. The 22T4 is a belter init

Glad it found a good home, Mark. That's quite a set ya got there now

Did you notice any reflections or ghosting when looking at Jupiter Revs ??

I'll go in to detail over the weekend as I'm aware that most of my posts in this thread have been a bit off topic. But the sort answer is; yes and no

I have turned into an ep junkie and haven't had a fix in over a fortnight

Seriously though, that 6mm is a lovely piece of kit and i look forward to reading your full review. Enjoy.

Cheers. One thing has become apparent to me over the last few months and that is that the saying; the eyepiece is half of the scope, is so true. In fact I'd go further than that. With scope optics being of generally excellent quality now-a-days in all but the cheapest scopes, the EP is the component that will make or break the visual experience.

Ok, if everyone could please refrain from posting any more pics or positive comments regarding the Delos it would be greatly appreciated. I am trying so hard not to succumb to temptation, again

Why would you do that to yourself??

The pics were taken on my phone which has a short FL giving a fish-eye effect. It's not that big really, just long

Nah , this one's a keeper. If I get chance this weekend I'll do a full report and post comparison pics

Just got in from a couple of hours with the Dob, checking out M57, the double double and Jupiter. The Delos is very impressive indeed!

Consistent across the field; sharp and bright (the contrast is superb). Trying a side-by-side with the 12T4 in the Ultima on Jupiter, the Delos wins hands down. While the detail was similar, the Delos had the extra sharpness and far more contrast. In moments of steady seeing I saw Amalthea, for the first time.

M57 showed more detail than I'd seen before at 200x despite viewing from very light polluted skies.

There's nothing to dislike really, even the price is reasonable. Highly recommended.