warts & all,new camera

[muletopia (Chris)]

Hello Folks,
A single 20 minute shot at gain 10 with a QHY8l.


Off axis guiding , PHD2. mewlon 210 at prime focus.

10 darks, demosaiced , dark stack an light demosaiced and pre-processed with
Nebulosity 4.


Auto developed and coloured with Startools 1.5,final contrast pass in Nebulosity.


More data? What else?


Cheers
Chris

[Atmos (Colin)]

Your guiding looks good! Adding more data will make a big improvement in many areas.
Taking flats will also help as you will be dealing with vignetting.
If you want the corner stars to look better you’ll need to get the reducer/corrector for the Mewlon 210 but that’s a personal choice.

[etill (Elliot)]

I recently got a QHY10 and while I'm terrible at photos I did find it useful and even pretty fun to go through a couple of processes with the camera to work out some of it's specs.

There's a pdf document called "How to Scientifically Determine CCD Gain and Offset Settings" which was a great start. Google will find you a copy, it's an excellent way to set up your gain and offset. Mine came out at 12 and 126, but cameras are all going to be subtlly different. That gain isn't the gain that software like PixInsight is asking for if you come across something that needs it (subframe selector, etc), it's the gain of one of the amps in the camera. You can calcualte the gain quite easily though.

Once I had setup the gain and offset, I ran through Craig Stark's process for calculating gain, full well capacity, etc here:

https://www.cloudynights.com/article...r-camera-r1929

It's not as hard as it sounds, you can do it with tin foil and a cut up sheet of paper. I stacked about 7 or 8 pieces of copier paper on top of the camera and removed one at a time to take the flats with it sitting on a desk in a well lit room. You can get all of the values you need from PI, and I'm assuming nebuloisty as well (because he wrote it)

There's a screen shot of how the QHY10 came out following the instructions in that article. I'm pretty sure its not quite right as it differs from published specs, and from the limited data points it seems like the cameras response isn't linear. I should drop that last data point and / or collect a bunch more, I'm going to do it again and collect 8. I did the same thing with my Canon and it was within 5% of the specs, so the process is correct, my data is just incomplete for the QHY10.

Anyway, my images didnt get any better yet, but I understand the camera now and in the future when all my other issues are worked out I'm sure this will help with correct exposure lengths and things like that. My calibration subs improved significantly as soon as I understood what was going on under the hood, flats in particular. I also like collecting data and putting it in spreadsheets, so it was a fun afternoon.

[muletopia (Chris)]

Thanks Colin & Elliot,


Colin,I have just received a flattener/reducer from Claude,Joshua Bunn is making me an adapter/spacer for the QHY. Putting an OAG in there seems difficult so I have ordered a 700mm fl OTA for guiding, I will not miss the fiddle of finding an off axis guide star and then rotating the camera for image orientation.


Elliot,your procedure sounds very good. It is forecast to rain here this afternoon and evening so I will try to comprehend what you have said and read your links,many thanks. We sure need the rain as our dams only just made it to the first rain this year.


Chris

[etill (Elliot)]

I am still fighting with the OAG, I have the ZWO OAG and ASI120 guide camera.

I have it very close, it's been a real struggle moving spacers around trying to get the OAG to focus with the main camera. I may have it right now, hopfully testing tonight if the weather is any good.

Getting it into the zone where you I can get it to focus with the main camera requires about a 6mm to 8mm spacer between it and the camera for me, a 5mm spacer had it just out of focus moved in on its stalk as far as I could.

[muletopia (Chris)]

Hello Elliot,
Rather than trial and error for determining spacer distance for the guide camera I did the following, with the aid of a competent friend.


In daylight we did it both for my Canon 60 and the QHY
For each camera we focused on a war memorial about 150 -200 metres away.
Running sharp cap for the imaging camera we had focus when the small lettering on the memorial was sharp. The the guide camera ( a zso 120mm in my case) was connected to sharp cap and the focus changed until the lettering was sharp again.
The distance the imaging camera moved is the length of the spacer required.
We did the Canon before I got the QHY, this required a fixng the distance of the guide camera on the OAG unit.
When we came to do the QHY we decided to leave the guide camera fixed and measure the required spacer distance to the QHY.
This means that removing the spacer from the output side of the OAG unit I can still use my Canon.
The spacer is a bout 2 cm long


A micrometer fixed to the telescope allowed the measurements to be taken.
For you I think fixing the guide camera and measuring the required spacer length would do.


I hope this helps you.



Chris

[etill (Elliot)]

Yes i think that process is probably the best way. My backyard doesn't really allow pointing a telescope anywhere but up though and I've only had the OAG for a couple of weeks - so no moon or that many clear nights for testing so far.

I found what I think is the issue while adjusting the spacers tonight. I've only had it setup up three or four times so I never noticed before but the prism has a pretty major defect. Hopefully I can just return that part of OAG instead of the whole thing, but eitherway it certianly explains why I thought I was spot on with adjustment then after slewing to another target it was completely out of focus again without actually touching the focuser.

You can see the spot in the prism where the defect is in the photo attached.

I've had a set of calipers out measuring it repeatedly and just couldn't figure out what was up, but then I have only looked at it outside it the dark until now - never saw that imperfection in the prism until now.

[muletopia (Chris)]

Yes, my scope id permenantly pier mounted & cant see horizon,So all the OAG & camera gear was taken to my fiends house and mounted on his telescope.
The whole procedure was done from his front verandah.


I asked him earlier for a photo of the set up,he has just sent me a composite image which is attached.


In reality we ran two laptops one on the guider and one on the QHY, this made life much easier.


Chris

[muletopia (Chris)]

My friend is helpful

[etill (Elliot)]

I tried it last night this way, just had to find a guide star that wasn't inside the blemish in the prism.

It was so much easier to measure the focuser travel than trying to measure the travel of the guide camera on the stalk, I had been fiddling around in the dark with a caliper for several nights. This way I had it measured and focused in two adjustments.

It works just as well with a star if the moons not up or no distant objects can be seen.