A Quick Ha Pelican - First outing with a Mono Cam

[Xiga]

Lately I've been thinking of picking up an 8300 camera on the 2nd hand market, and recently @tooth_dr was very kind to offer me the loan of one of his own, a Qhy9, and after a brief dry run a couple of weeks ago during a near-full moon just to figure out how to actually use it, i finally managed to get out and capture some actual data with it. 

This was shot on May 14 with no Moon, but also no Astro Dark, just Astronomical Twilight. And in fact, the last sub was even shot in Nautical Twilight. In truth, it was mostly a frustrating night, as i was fighting mount & guiding issues for most of it. Even though i had used the camera the week before without issue, on this occasion Phd2 just wouldn't calibrate properly for me. In the end, after wasting over 2 hrs of what was already going to be a short night, i finally worked out it was due to Dec imbalance, as i was now too camera-heavy (even though it had worked ok previously). So in true MacGuyver form i stuck a kitchen utensil to the front of the ota with some duct tape 😂 and all of a sudden it calibrated fine! Anyways, even after that the guiding was still awful, ~1.1" compared to the usual 0.8"ish. Thankfully i got away with it due to the imaging scale being 2.2". I'm still not sure what was going on exactly (the HEQ5-Pro was blinking erratically at one point, so much so I unplugged it and started over again, and it seemed to behave better after that). I'm putting the crap guiding down to seeing. At least i hope that's all it was! Also, i was late in setting up, and because i was in a hurry, i accidentally put the Ha filter in instead of the Oiii one. With no moon about, this was supposed to be an Oiii night! 🙄 

Anyways, aside from all that, i am very impressed with the Qhy9. This is my first time using a mono camera, and boy what a difference it makes. I went back and looked at some of my old Ha data shot with the D5300, and the difference when comparing subs of the same length was remarkeable (albeit unsurprising - stating the obvious i know). I was still able to turn out decent NB images with the D5300, but jeez the Qhy9 data is just amazing by comparison. 

Capturing and processing this was a joy. It was nice only having to deal with a handful of subs for a change, instead of the usual hundreds that comes with CMOS (that might be changing now though with the newer CMOS cameras that are 16bit).  I started out with a 10min sub, but the Mean ADU looked low in SGP, so i upped it to 15 mins. Again, i thought it was still on the low side, so i finally upped it again to 20 mins. I was surprised at how little the Mean ADU increased from 10 mins to 20 mins, but even just visually i could see the 20 min subs looked a lot better so i kept it at that. If i had a better mount, and more reliable skies, i wouldn't hesitate to increase the subs even further tbh. 

So in the end this is just 6 subs and 100 mins in total, made up of 1 x 600s, 2 x 900s, and 3 x 1200s of Ha (2" Baader 7nm) and a SW 80ED. Stacked in APP and processed in PS. The only processing done was a DDP stretch in APP, star removal using Starnet++, Topaz Denoise AI followed by some Curve adjustments in PS. 

Hopefully i'll get a chance to nab some Oiii, and maybe even some Sii, before the Astronomical Twilight goes. But if not, i'll still have a go. Us Northern folk don't have many other options at this time of year!

Clear skies, and stay safe all. 

[Mr Spock]

Nice image and a good write up too.

[x6gas]

That's lovely and very impressive with relatively modest total integration time.

[tooth_dr]

Good to see it is working well for you!  Too many folks criticise the 8300 chip.  That’s excellent for 100 minutes.

I haven’t shot above 10 mins, maybe I should be looking longer?  Like you I didn’t see much increase in ADU, so I stuck with 10 mins.

Hope you get some Oiii and Sii soon.  I didn’t realise you had an Sii filter!

[Xiga]

2 hours ago, Mr Spock said:

Nice image and a good write up too.

Thanks Michael

2 hours ago, x6gas said:

That's lovely and very impressive with relatively modest total integration time.

Thanks Ian

[Xiga]

42 minutes ago, tooth_dr said:

Good to see it is working well for you!  Too many folks criticise the 8300 chip.  That’s excellent for 100 minutes.

I haven’t shot above 10 mins, maybe I should be looking longer?  Like you I didn’t see much increase in ADU, so I stuck with 10 mins.

Hope you get some Oiii and Sii soon.  I didn’t realise you had an Sii filter!

Thanks Adam ,and thanks again for the loan of the camera!

Yeah I was surprised too at just how little the ADU went up, but in the end I just trusted my eyes as I could see a noticeable improvement. I would definitely try longer subs Adam. With CCD's, you generally want fewer longer subs rather than more shorter ones. So in this case, 1 x 20 mins should be better than 2 x 10 mins as you only get one hit of Read Noise instead of 2 (the RN is significant with these cameras). Now, if you were able to sufficiently bury the RN in each sub, then it wouldn't matter so much, but by my calculations I would need a Mean ADU of about 2400 in order to bury the RN by a factor of 10, whereas at ~1300 (with 20 min subs) I am only managing a factor of just over 3, which is down at the minimum end of the scale. So I think with this setup I am just aperture-limited with the 80mm scope when doing NB. Not a show-stopper that's for sure, it's still possible to get an image with good SNR so it wouldn't put me off the 8300 sensor at all. You should have no problem getting a much higher ADU Adam when you get your Tak 180 up and running.

I picked up an Sii filter last year. Still yet to use it! lol

[ApophisAstros]

I love those dust lanes , great image.

Roger