Dslr flats and bias with Asiair pro

[AstroNebulee]

Hi

I haven't got to try my Asiair pro in anger yet. I use my Canon 600D to image with and was hoping for. Before my AAP I used to take my bias frames with cap on and turning the exposure to 1/4000 as that's the fastest I have and when taking my flats I switch the aperture priority mode to put a t-shirt over the end of the scope and rest my phone white screen on the end and let the dslr determine the exposure time. Both in the same iso as the lights. My question is how can I input 1/400 into my AAP and also take my flat frames with settings on my dslr and AAP. Sorry if I'm being completely thick here but I've searched on the Internet and it's mostly all about using osc cameras. 

[AstroNebulee]

An update to this thread I started, I've experimentwd indoors as I've had no clear night's so far to test taking flats and bias with my AAP. To set my bias I've taken the exposure time down to to the lowest on the AAP will give me which is 0.000032 and taking the flat files, the AAP determines the exposure time itself and this was around 8 seconds, which I'm thinking can't be right as when I take flats with my intervalometer and dslr setting av mode it's very short exposures. I attach a white t-shirt double folded to my scope and then hold my phone rubbish screen on the end as usual. I'll include an image of my bias and flat file. So regarding the flat files do I have to switch my dslr to av mode as usual. There's no help anywhere...... Edit I have taken the auto setting off for the flat files and changed exposure time myself to 8sec and now getting this screen with looks more like the flats I usually got before and the histogram is in the middle as people suggest it should. So there therefore I shall not use auto mode for flats. 

Edited August 7, 2021 by AstroNebulee

[Richard_]

Hi pal, I've taken photos with exactly the same setup so hopefully I'm qualified to help

When using the Canon with the ASI Air Pro (AAP) I stick the camera in "M" manual mode and leave it alone. Bias should be the shortest exposure time of the camera, so 1/4000s is 0.00025s so use that for your bias images (I can see the filename of your bias is 250us which is exactly 0.00025s so the AAP is using the minimum already). 

For flats, I use the t-shirt method too and a bright uniform light source. My light source is a lenovo android tablet. I unticked auto brightness and set to maximum brightness. Ensure that "night mode" or equivalent is also switched off. I then load a white image designed for flats which was referenced in a book I have (link: http://www.covingtoninnovations.com/dslr/blank/white.html),and this way I know I have a uniform white light source which is repeatable. In the AAP program, you can tick a box under flats to determine exposure time (kinda like using Aperture Value "Av" on the camera). From memory, my flats are around 200ms and you can control the time by having multiple layers of t-shirt as it's a bit more difficult to remember exact brightness set on the iPad/tablet screen. 

From your comment, you seem to be getting flats at 8 seconds. For me, this takes around 4 layers of t shirt to attain, so either your light source isn't bright enough or your t shirts are very thick! Are you using any filters at all, or is this just the camera and lens? What telescope are you using? 

I don't recall my DSLR, but for my ASI533 camera I believe I need to aim for an average ADU of 30,000 to get a good flat. If I recall, I believe that the AAP chooses the correct exposure time to get you to around 30,000 ADU which can be seen on the lower right of your final image. 

[AstroNebulee]

Hi thank you so much for your informative reply. Really appreciate it. I'm using my Skywatcher 72ed ds pro on az gti mount. For taking my bias frames I set the dslr to M as always thought the whole process of using my AAP,tgrn set the exposure to. 000032. For my flat files I unticked the auto box set to 6 or 7 seconds to get the peak around halfway on the histogram. I cover my scope with a t-shirt through 2 layers of it and hold my smartphone with a blank white screen down it. I will download your white screen you use, tick the auto box and up my brightness on my screen as I think I had it to low. 

Thank you again for helping me 

Edited August 8, 2021 by AstroNebulee

[Richard_]

56 minutes ago, AstroNebulee said:

Hi thank you so much for your informative reply. Really appreciate it. I'm using my Skywatcher 72ed ds pro on az gti mount. For taking my bias frames I set the dslr to M as always thought the whole process of using my AAP,tgrn set the exposure to. 000032. For my flat files I unticked the auto box set to 6 or 7 seconds to get the peak around halfway on the histogram. I cover my scope with a t-shirt through 2 layers of it and hold my smartphone with a blank white screen down it. I will download your white screen you use, tick the auto box and up my brightness on my screen as I think I had it to low. 

Thank you again for helping me 

No problem, keep the post updated with your results. The link above is an active website, so you can just save the bookmark to your smartphone Web browser and open it up each time. 

Try the one layer of t shirt and hold the smartphone right up to the t shirt. Does your smartphone cover the entire diameter of the objective lens or are there some gaps? 

Out of curiosity, when you were taking flats without the AAP, the camera was in Av mode right? What exposure time was used for your flats and what was the ADU readout of the flats? (assuming you have pixinsight, you can find this out my going to Process > All Processes > Statistics). 

[AstroNebulee]

There is a slight gap on the two sides of the scope end when the phone is over it, what I may try and do is use my tablet as the quite screen and use my phone to use with AAP to take the flats or just once I have carried my set up back indoors use my laptop screen as the white screen but this may dislodge the dust motes on the scope I'm thinking? I can't remember what the exposure tone was when taking flats with my intervalometer but they were fast exposures compared to the flats with the AAP.