Spongey

7 hours ago, Endolf said:

This is just 30 minutes of Ha data with the Antlia 3nm Ha filter on the QHYCCD 268M, no calibration frames yet. This is so much better than I was getting before, it's almost like going from a DSLR to your first astro cam again. Just 6x300s (Gain 50, offset 15). I think I'm going to like this

Very nice! What scope are you using?

Also good to see that you aren't having reflection / halo issues like I am. Hoping I just got a dud or that flipping the filter will solve my issues.

Also, what readout mode are you using? Gain 50 seems like an odd choice considering HCG kicks in at gain 56.

1 hour ago, Sp@ce_d said:

Nice.. This camera is looking very promising! I'm still trying to decide on QHY or ASI, probably won't be till next season as I'll loose astro darkness before one turns up anyway. My Antilia 3nm turned up yesterday, still waiting on SII & OIII. Not looked at it yet, is there an orientation marking? Be interesting to see what they say.

There is no specific orientation marking, but their website says that the non-ghosting side should be towards the sky, so that is how I installed it. I have yet to hear back from them but will update this thread when I do. 

I've also flipped the filter to see if that helps, but with no clear skies forecast it doesn't look like I'll get the chance to test any time soon.

3 hours ago, peter shah said:

Wow that deep.... beautifully done

Thank you Peter, I can only hope to get to your level one day!

15 minutes ago, souls33k3r said:

Very nice indeed. The Antlia weren't supposed to give halos as they made a big thing about that on Facebook. 

Also, your stars do look off, more like pinched optics to me. Maybe someone else with a bit more knowledge and better eye can chime in. 

Cheers, as said I've emailed their support line asking for feedback but no response yet. You're correct, I do suffer from pinched optics in the cold. I detailed it in another thread as linked below. I have accepted it as a 'signature' of my scope, and it doesn't bother me too much.

I had a clear patch last night, and despite a flurry of other issues with my gear, I was able to capture a total of 13x300s subs on IC410 with my new QHY268M and Antlia 3nm Pro Ha filter. Shot at gain 56 offset 10.

This is the full field of view, only cropped to remove stacking artefacts around the edges.

Uploaded in 1:1 for all your pixel peeping desires

Shot with my Esprit 100 and CEM40.

Very happy with the camera so far!

I do notice the halos around the bright stars at the bottom of the frame, and have got in touch with Antlia about them. 

CC welcome, as always

Nina crashed just after I went to bed so only managed 13x 300s in the end  

A quick stack and stretch, no other processing applied.

Honestly I am both amazed and thrilled with this outcome! I can only imagine what 5+ hours would look like. I do have a halo on one of my stars at the bottom which isn't ideal. I might try flipping the filter.  

Managed to snatch a clear spot. First 300s sub with 268M and Antlia 3nm Ha Pro. Gain 56 Offset 10. Calibrated and stretched, that is all.

Having a host of other issues with my focuser etc. so used the bahtinov mask for this one.

Amazed with the depth from a single sub though... Taking some more subs now before the cloud comes in later tonight. Will stack tomorrow and see what I can get 

Cheers

Hi, are there updates to share about the progress of this project?  

Incredible depth for a single 300s sub! I'm dying to get mine out under the stars, but it might be a while until we get a clear night here 

Updated BasicCCDParameters based on 99s and 999s darks:

Gain 0 offset 10

Gain 56 Offset 10

Dark current looks better on these, but still higher than expected / published. Not sure of the root cause, I don't think the script works well with such small values of dark current. In any case I'm not concerned.

Some more info incoming...

I ran the BasicCCDParameters script using some of my calibration frames for both Gain 0 Offset 10:

and Gain 56 Offset 10:

Looks like the specs match up quite well with the published graphs. I do note that the dark current seems quite high, but this is based on relatively short dark frames and it's been noted already that using short darks for this messes up the script. I'm taking some 99s and 999s darks at the moment so will re-run the script with these once they are done.

Just now, tooth_dr said:

Thanks, going to do my calibration tonight.  I was aiming for -10deg, that should be ok?

I'm also using -10 degrees. At this level of dark current going to -15 isn't necessary imo, and sticking with -10 means I can safely achieve that temperature all year round.

3 minutes ago, teoria_del_big_bang said:

TBH I would be not that sure what would indicate that Bias frames are unstable but yes I agree  they both look pretty much the same.

From what I have heard, some CMOS cameras can exhibit strange banding or blotchiness in very short exposures. I don't see any of that in my master bias or in the darkflat, and the statistics tool in pixinsight shows that they are almost identical.

2 minutes ago, tooth_dr said:

What exposure length is the bias?

Bias exposure length was set to 0 in NINA, FITS header reads it as 0.000001s

1 minute ago, teoria_del_big_bang said:

TBH I would be not that sure what would indicate that Bias frames are unstable but yes I agree  they both look pretty much the same.
So you think going with the normal workflow in PI using the master super bias is the way to go ?

Steve

Yes, calibrate flats with master bias (not superbias - there is conflicting info about this process), and calibrate lights with master dark and master flat.

Cheers

3 hours ago, Spongey said:

It is a good question and one I'm not sure of the answer to just yet.

I'll be building a flat library tonight and will also take some flat darks to compare with the bias frames. My understanding is that flat darks are preferable to bias frames with cameras that have unusual very short exposure effects (e.g. ASI1600). When dark current is negligible (which it is at -10c) and the camera is stable at very short exposures, bias and flat dark frames are essentially identical. From what I have seen and read, people with the QHY600 / ZWO6200 have been using bias frames over flat darks with no issues. I would hope that the IMX571 would be similar in this regard. 

In any case shooting off 50 bias frames doesn't take long!

So I've just stacked 30 dark flats at 0.68s each for my Lum filter and flat panel and the result is attached.

My conclusion: dark flats are not necessary with this camera and a master bias is sufficient to calibrate flats correctly.

My reasoning: The master bias I attached in my last post is essentially identical to this.

Master darkflat.xisf

5 minutes ago, teoria_del_big_bang said:

Do you think we should be using Bias frames with this camera ?
I never used them with the 1600 as most people said that CMOS cameras gave unstable bias frames and to use just darks and flats that have been calibrated with dark flats.

Steve 

It is a good question and one I'm not sure of the answer to just yet.

I'll be building a flat library tonight and will also take some flat darks to compare with the bias frames. My understanding is that flat darks are preferable to bias frames with cameras that have unusual very short exposure effects (e.g. ASI1600). When dark current is negligible (which it is at -10c) and the camera is stable at very short exposures, bias and flat dark frames are essentially identical. From what I have seen and read, people with the QHY600 / ZWO6200 have been using bias frames over flat darks with no issues. I would hope that the IMX571 would be similar in this regard. 

In any case shooting off 50 bias frames doesn't take long!

My camera arrived yesterday and looks great, it is a big beast though! Very well packaged from MA so top marks there.

I've attached a few photos:

Filters are Baader LRGB, and Antlia 3nm PRO Ha, Oiii (waiting on this one), and Sii.

I managed to build my bias and dark library overnight too, and have attached some files if anyone wants to poke around. Each stack is 50 subframes. I've never used a cooled camera like this before but they look good to me, with minimal fixed pattern noise and few hot pixels.

Looking forward to first light with my first foray into mono imaging!! 

Cheers

Gain 56 Offset 10 Master Bias.xisf Gain 0 Offset 10 Master Bias.xisf Gain 56 Offset 10 300s Master Dark.xisf Gain 0 Offset 10 180s Master Dark.xisf

9 hours ago, vlaiv said:

Since geometry does not change, effects of nominal F/ratio onto filter effectiveness remain the same.

While I agree with everything Vlaiv has said, is it not true that scopes with a central obstruction will be affected worse by filter 'aperture stop' effects due to fast f ratios?

As a higher proportion of waves come in at an angle, more light is lost when compared to a refractor of the same speed. I seem to recall reading an article on this some time ago, I think it was documented over on CN. I'll try to find the link.

Cheers

Edit: found the thread

I will detail it for sure, though I will most likely start a new thread dedicated to the 268M as this one has wandered very far from it's original intent.

My 268M has just shipped! Should be here over the weekend or Monday.

I can't wait! 

11 minutes ago, teoria_del_big_bang said:

FYI

Just received the following info from Rupert at Astrograph about the QHY268M cameras:

I have just opened up one of the 268M's we just had in to confirm what is supplied.

The camera provides 12.5mm BF from the back of the filter wheel.
It also  includes;

- a threaded M54 adapter of 4mm length giving you 16.5mm BF
- a threaded M48 adapter of 5mm length giving you 17.5mm BF
- 1 pc 1mm M54 spacer
- 3 pc 3mm M54 spacer
- 1 pc 10mm M54 spacer
- 1 pc M54 to 2" nose

So if you are using the SW flattener, this should have an 8mm spacer to M48 on the back of it which is 8mm thick. That is supposed to leave 55mm back focus.
The adapters supplied with the 268M, assuming the camera is bolted to the QHY CWF3-M-US will provide 44.5mm (1xM48 5mm, 1x1mm, 3x3mm, 1x10mm). This allows you to add a QHY OAG if need as that is 10mm and takes you up to 55mm. (Note the BF tolerance on the camera is +/- 0.5mm)
I also keep various adapter sets for the cameras, one of which includes 0.5mm, 1mm, 2mm, 3mm and 7mm. This would give you the 10mm otherwise needed. 

 

Just thought this might be useful for some to now up front 🙂 

Steve

Great info, thank you.

Looks like the package includes everything as stated by QHY in this post and diagram (blue and red), minus the filter wheel:

First batch of 2600MM finished! 

1 minute ago, gorann said:

If it is a tilt adjuster it must be one of the least accessible ones.

I've just re-read the post and he mentions that the tilt adjuster adds 5mm. I've asked for a photo / further clarification.

13 minutes ago, gorann said:

Thanks - very good to know! The M48 adapter is what I need. It will turn the QHY268M it into an ASI2600MM👍. The post says something about a tilt plate but someone here said that there was no tilt plate in the QHY268M.

I believe that he is referring to this top 'plate', which is screwed into the camera.

On previous cameras such as the 268C this top plate is not present and instead is replaced with the dovetail style attachment. I have read people saying that this dovetail is what was labelled as the tilt plate on the previous cameras, hence my previous comment regarding the poor translation.

If this is actually a tilt adjuster then that would be quite useful, but it doesn't look particularly easy to adjust if it is! 

Based on the below diagram for the 268C, it looks like this is simply the top part of the camera, which encloses the sensor chamber. Removing the top plate and adjusting the screws in the above photo would not be a good idea in that case. My suspicion is that the top plate as above simply replaces the dovetail attachment and serves no tilt adjustment function.

Some info on the 268M and its supplied adapters: https://www.cloudynights.com/topic/753265-received-my-qhy268m/#entry10841589

I have ordered the QHY 268M for similar reasons to those mentioned above, but primarily availability and price. 

If the two cameras were the same price then I probably would have gone with the ZWO, but £400 is a significant chunk. If I end up needing a USB hub then I'm sure the savings from the camera will cover it 

Considering both of these cameras are based on their colour counterparts, one other thing possibly worth noting is the issues with residue on the 2600MC sensor due to grease used in manufacture. I haven't heard of any similar issues with the 268C.