SyedT

Dave, see above.

For anyone who cannot access the document! Measuring the absolute QE of the QHY268M Sony provides relative QE curves for the IMX571 sensor used in the QHY268M camera. However, by comparing its response with a CCD of known absolute QE, the ICX694 used in the QHY22, we can determine the absolute QE for the QHY268M. The graph below from the Sony IMX571 datasheet shows the relative QE of the IMX571.The good news here is that this curve includes the near infrared wavelengths. The QHY600M graph, for example, only shows thed QE in the range of 400 - 700nm. However, for the QHY268M we have the curve from 400 - 1000nm. It is good to know the near infrared response from 700 - 1000nm. Sony's official curves for QE are good for showing the relative response of the sensor across a range of wavelengths but, typical of Sony's QE data, the peak QE is always equal to 1 or 100%. In order to get the absolute QE, key information for astronomical and scientific imaging, we performed the following experiment to find it. First, we need a sensor with known QE. In this case we used the well-known Sony ICX694. This sensor, used in many popular CCD cameras like the QHY22, ATIK460, QSI and others, has been characterized by others like Christian Buil. The QE curve can be found here: http://www.astrosurf.com/buil/cameras/index.html (ref.1). Also, there is another value at http://www.astrosurf.com/buil/CMOSvsCCD/index.html (ref.2). To find a fit for the curve, we select one wavelengths for measurement. In this case we use an OIII narrow band filter to measure the response at the wavelengths of 500 to 505nm, because this point is very close to the peak QE point and the error will be smallest. From the ICX694 QE data we know that at OIII the absolute QE is 67% (ref.1) or 63% (ref.2). Using the same light source and lens, we measured image intensity at different exposure times for both a QHY22 and a QHY268M. Then we derive a curve of the intensity increasing with exposure time. With linear fitting we get the number of ADU's per second in both cameras. The system gain of the QHY268M on the gain/readmode of this experienment is 0.36e/ADU and the pixel area is 14.13 um^2. For the QHY22 the system gain is 0.34e/ADU and the pixel area is 20.25um^2. intensity ADU/sec/pixel intensity e/sec/um^2 QHY268M OIII 6036 153.78 QHY22 OIII 6574 110.36 From above table we can see that at the wavelength OIII it is 1.39 times that of the QHY22. ICX694 ratio IMX571 63% (ref.2) 1.39 87.57% 67% (ref.1) 1.39 93.13% From the Sony data we know the relative QE value is 0.97 at OIII. Therefore, the peak QE for the IMX571 is calculated as 0.8757*(1/0.97)*100%= 90.2% or 0.9313*(1/0.97)*100% = 95.9%. Conclusion The test results shows that the QE at OIII is at least 87% and the peak QE of QHY268M is at least 90%. As expected, this test result is very similar to the results obtained for the QHY600M (QHY600 results is 87% @ OIII). Based on the above tests, we have derived the absolute QE curve of QHY268M from 400nm-1000nm seen here:

I found these to be good reads: http://cosmic-colors.com/gear-reviews/qhy268c-review/ https://www.qhyccd.com/index.php?m=content&c=index&a=show&catid=23&id=263

Agreed, this is despite aiming towards a well lit street and clouds, so it should be even better when conditions are more favourable. I have no clear skies for the next week at least... Thanks, same here. That intermittent clear sky for me was an anomaly more than anything else! The SDK version is 20.6.26.0.

Did not realise a thread had already been created so I started another one elsewhere! I received mine yesterday, it's a beast. Had a short period of intermittent clear skies yesterday evening so had a go. Single frame of 300 seconds at the "Photographic DSO" setting (gain 102, offset 76) using 3 nm Chroma Ha 36 mm filter through a Takahashi FSQ85-EDX. TEC set at -10 degrees. No calibration frames applied. I was imaging towards a well-lit street and through intermittent clouds which explains the amount of glow (ADU was very high on SGPro as well which fits). File size 49.8 MB) present. I can see some light fall-off and star distortion towards the edges if I pixel peep (likely tilt), but I think I can live with it! All looks very promising so far, can't wait to test it out properly.

If anyone is interested, I've received the 268M and have done an initial test run: QHY268M Unboxing & Test Run

I've been impatiently awaiting the QHY268M's release, and finally received it today alongside the QHYCFW3 thanks to Bernard at Modern Astronomy. Below are images of the unboxing with the various components: Straight off the bat, what hit me was the quality of the packaging and how neatly everything was arranged. I know we're paying a premium for these cameras so it's to be expected, but still a nice thing to see. They've included an AC to DC adapter, alongside plenty of spacers to get you going, and a desiccant hub with desiccant balls. The camera itself is very chunky (as expected), and has a really nice weight and premium feel to it. There is a USB 3.0 connector and a 4-pin connector for the QHYCFW series, alongside a 11-13V DC input socket. I would want to make a comment at this point regarding QHY not taking the initiative to add in a USB hub, as that would be really useful; not sure why that's not the case as of yet. I'm using the 268M with the CFW3, 36 mm Chroma filters, Takahashi FSQ85-EDX and the Takahashi 1.01x EDP Flattener. I've also attached some images of the QHYCFW3, because why not. The great thing about the 268M is that they've engineered it so that it now has 5 mm less backfocus distance, i.e. 12.5 mm vs 17.5 mm before. As can be seen below, the CFW3 can be bolted directly to the 268M, which results in a total backfocus of 30 mm. I was concerned about backfocus initially as I use a reducer in my train, but this step from QHY meant that I had 5 mm remaining once everything was accounted for. Again, the CFW3 comes with plenty of extras, including thumbscrews if you fancy using the dovetail plate instead of directly bolting it, required cables and lots of extra screws and washers to fix the filters to the carousel (I think I had about 15 washers left over once I was done). So far it's operating flawlessly via the 4-pin connector. I got lucky tonight with a short window of clear skies, and got a couple of images. Initial results look very promising, although I can see some definite light fall-off which is to be expected with 36 mm filters. I've left everything at default settings, and am using the DSO option within the 268M's driver settings as below. The TEC is running at 12% power to maintain a temperature of -10, and about 35% for a temperature of -20. Ambient temperature tonight is 0 degrees. Below is a single sub of IC1805 of 300 seconds @ -10 degrees, with a FITS file size of 49.8 MB. I'm not sure how interpretable this is, as there were patches of cloud passing over whilst I was capturing it, and the scope was pointing towards a streetlamp (hence the right-sided glow). There are plenty of bad pixels present (less so at -20 as expected), which will hopefully calibrate out easily. As it has now clouded over, I think I'll create a sequence of dark frames at various gain settings to run overnight. If nothing else, at least I managed to put everything together, get it all focused nicely and take a sub! Will update this thread as and when I get to test it more (although this whole week looks cloudy). Hopefully someone finds this rambling useful! Cheers

I previously used the Pegasus Pocket Powerbox with an Anker 10-port USB hub, which worked really well. If you're not fussed about an all-in-one, I see absolutely no reason as to why you shouldn't go for it. In terms of specifics, what I found really useful on the Pegasus was the auto dew control function; as it keeps the temperature just above dew point, there's a much lower risk of cooking the objective! I ended up replacing the PPB and USB hub with an Ultimate Powerbox as I also purchased an Intel NUC to make the setup fully remote.

I'll agree with those saying that the generic brand batteries can work fine, I've owned them for my Canon 650D and now a Canon 6D, both hold more charge and have performed faultlessly. There is the danger of variable QC however, so it may be that you got a bad sample.

Hi there, I didn't use any calibration frames actually, just cropped out the minor vignetting at the edges. I did image from a Bortle 4 zone, not sure what the LP level within your area is as that may make a difference. Cheers

Easily the best horsehead and flame image I've seen, outstanding!

Thanks Olly, that's really helpful. I'm looking forward to getting the 268M, will post with feedback once I've done some test runs.

I wrote to ZWO and they've said the 2600MM will likely come sometime in 2021. I've ordered the QHY268M which will be shipping from 15th Jan. Wow, that's lovely! I find I would get a better field without the reducer, and I've added a field flattener to improve results a bit and it seems to have worked. I've ordered the QHY268M, looking forward to getting it! In terms of money? Yes. Time? No! 😖 Stunning work as usual Olly. I've not used a full-frame camera myself so can't comment on the results, but doing some reading around I found that the best size to aim for is APS-C with the 1.01x flattener, so I've ordered the new QHY268M which is shipping in January. I've been working on M31 as a 2-panel mosaic, but the weather and moon have not been on my side unfortunately and I don't have as much data as I'd like. I've taken a screenshot of what the QHY268M's field would look like using SGPro's Framing and Mosaic Wizard. I would probably miss out the faint outer halo particularly to the left, but should get most of it?

Thank you. It's classed as Bortle 4 with distant city lights causing significant air glow to the right. I had to work fairly hard to keep the LP down in processing, but it's better than doing it from home! Cheers for pointing that out, my bad! Hopefully when I revisit this image I'll change it.

Yes, should be able to! Great suggestion. I actually really enjoyed just looking and seeing what I could spot without using a chart and then labelling it manually, but your idea would definitely save time!

Never gets old for me. Certainly is! I just used the line and text tool in Photoshop to label it manually, took a few minutes but worth it. Thank you. I could look at it every day and still be fascinated by it. Taking more of an interest in Sirius recently too, it's stunning.

Orion has to be my favourite constellation in the night sky, there's just something about its familiarity that provides a source of wonder and comfort. This is a composite of 39 x 30 second exposures taken with a stock Canon 6D and 70-200 mm f2.8 lens @ 70 mm mounted on a Skywatcher Star Adventurer on a Manfrotto tripod. Considering the level of light pollution I wasn't expecting much in the way of faint details, and so was very pleased to see that there are plenty of deep sky objects visible. I think I can also see a hint of Barnard's Loop. This is definitely a composition I'll be going for again, just to see how much more detail can be obtained with a longer total exposure time.

Just got a response from ZWO: 2600MM won't come this year but there is such plan next year

The issue with these 16-bit APS-C sensors is that they're all colour e.g. https://www.firstlightoptics.com/zwo-cameras/zwo-asi-2600mc-pro-usb-30-cooled-colour-camera.html and https://www.modernastronomy.com/shop/cameras/cooled-ccd/qhy-cooled-ccd-cameras/qhy268c-photo/ Same sensor, different companies. I'm getting in touch with both companies to see whether there is a mono version of the above on the cards, which would be perfect. I did hear of the QHY268 getting a mono version, but there don't seem to have been any updates since: http://www.iceinspace.com.au/forum/showthread.php?t=184422 EDIT: Just saw this https://www.qhyccd.com/bbs/index.php?topic=8252.0 Re: the iPolar, I did test it out yesterday. It's a bit more fiddly than the PoleMaster, but I was aligned fairly quickly. Didn't get to do any imaging as clouds rolled in, however, so the true test is yet to come.

I think you'd be OK with the 1600MM and 300 second exposures. I used to have a 1600MM; my main issue was the 12-bit ADC giving posterisation in some scenarios, which is why I switched to CCD (Atik 490EX). However, all that may well change as there are 16-bit CMOS sensors being released, although I'm waiting for an APS-C size mono 16-bit sensor which would match well with my scope. For polar alignment, have you looked into getting an iOptron iPolar? It's an electronic polarscope which doesn't require a view of Polaris.

You can have a look at one of my integrations here: I only did 300s subs due to inconsistent guiding because of wind/poor seeing etc. You can see there's a fair amount of background noise which means it doesn't look as "clean" as it should, despite a good overall integration time.

I owned a set of Baader LRGB and NB filters. While they were great, they're no match for the Chroma set I replaced them with (managed to get them less than half price each as part of a package). I would go for it. The main issue with 3 nm NB is that it takes long exposure times to lift the histogram off the left edge, so you need to either have a fairly sensitive camera (the 1600MM definitely ticks that box) and a mount capable of guiding these. On the plus side, I'm yet to see those horrible halos you get with some filters!

Very interesting find, thank you for that! It does seem like it would be a great match.

I've become quite used to the pinpoint stars and lack of haloes which comes with my current setup, so wouldn't want to change scopes! Guess I need to keep looking around, perhaps a mono iteration of the 2600MC might be on the cards.

Thanks David. The 294MM just about fits in M31 into the view. Ideally, I'd like a larger FOV than that. Any other suggestions? It would be nice to go to an FSQ106 and 50 mm filters, but it's not really an extra expense I can justify at the moment.