festoon

So I got hold of a Fujinon HF1.8HB-L1 1.8mm focal length Fish Eye lens, and indeed it does seem to improve significantly the off axis aberations. Also has given me signifcantly more field of view which is great.

The only strange thing is the exposure times are signifciantly longer than what I've used with the other lenses to get the same image brightness. With the standard ASI224MC lens I was taking exposures of 20s with a gain of 0 (the images in the first post), here I'm taking ~100s exposures with a gain of 135. When I left the gain at 0, the software (AllSkEye) was going beyond 180 seconds to try and achieve a median image brightness the same as before. If anything I was expecting the exposure to go down as the Fujinon lens is 'faster'. Does that mean the transmission or losses of the Fujinon lens are much worse than the fish eye lens that comes with the ASI224MC?

Usually the drift depends on how well I polar aligned. (Which I use SharpCap for). Yes do see drift in dec.

For sure I could probably go longer than 30s but that is what the optimum exposure time is due to light pollution and low read noise of the CMOS (based on the SharpCap smart histogram https://www.sharpcap.co.uk/sharpcap/features/smart-histogram)

Thanks @newbie alert,  the mount is a heq5

Thanks @Skipper Billy. Yes I’m using an tracking equatorial mount. I can understand the point that if I need to guide at a rate of say 1s exposures then they need to be different cameras. In my case my exposure is usually 30s and my stars are still not blurred during this time.

Good point @vlaiv about the software. Yes I don’t know what software would do this, and was part of the reason behind posting here if it would even be feasible. 

If I am using a CMOS camera for deep sky imaging at a focal length of 412mm.  I usually take many exposures of 30s length and stacking. Each sub there is no noticeable drift of the star or blurring.

However after maybe 2-3 subs there is a noticeable shift in the framing of the image. At this point all I would like to do is re frame the image. In this scenario is it possible to use the same camera for guiding and imaging? Probably better described as correcting the tracking and imaging using the same camera.

It took me a few attempts flying using the force and failing! but when I just used the numbers to guide me I docked successfully  

57 minutes ago, AngryDonkey said:

A lot of people are using the Arecont 1.55 for their all sky cameras which seems to work well. Also, it looks like either the camera or the lens is at a bit of an angle as the aberration only appears at the bottom of the image. If you get it all centred it will probably be better all round. I went for a Fujinon 1.8mm lens (which is even more expensive) and even then you get some aberration: https://www.allskeye.com/allskeye-live/

Mike

Thanks Mike, I noticed that too about the lens potentially being at an angle. Not sure how to fix that as the lens screws into the threaded mount on the camera and the focus is achieved by rotating the lens in the housing.

Thanks for the info on the arecont and Fujinon lenses I'll take a look at them. 

1 minute ago, paul mc c said:

I cant answer your question,but really like your pic,could you tell me how you took it please.

Thanks @paul mc c. It was taken using my ASI224MC with the wide angle lens with an exposure of about 25 seconds. The image was auto stretched using AllSkEye which is a fantastic piece of software for all sky cameras.

Just testing out my ASI224MC camera last night with the wide angle lens that came with it. I noticed how the stars in the centre of the field were focused but the stars towards the edge were out of focus. 

Is this common to see this much spherical aberration with a wide angle lens with the one supplied by ZWO? Also any recommendations for a lens that gives better results would be much appreciated.

Hi Steve, no it can only be controlled electronically

hi @RadekK and @Stu Todd sorry if you thought I was complaining - far from it. Just trying to get my sw mount and indi to work well together

I found the same issue as @stash_old...with the sw az indi there was no way to park the scope at north and level. When I tried park north it sent the Ota on a merry go round and I had to pull the plug to stop it hitting the mount legs.

and if I use the sw gti driver with indi it only parks at the north celestrial pole

This is fantastic - well done!

2 hours ago, bokser01 said:

Yes HQ camera

 

Edit: I'll try to upgrade to the buster version

Even on a buster, it won't let me go over 10.2s

 

 

I see this has also been asked on the pi camera forum. So it’s not just you  

https://www.raspberrypi.org/forums/viewtopic.php?f=43&t=272658&start=50

Might be worth asking it again in an alternative thread as no one has answered yet 

9 minutes ago, bokser01 said:

Even after a complete update, I won't get over 10.2s It's weird

Is it with the new HQ camera of pi v1 or v2 camera? 

1 hour ago, bokser01 said:

Hi how to reach 200s exposure? Raspistill allows me a maximum of 10.2s more will not let me go! What am I doing wrong?

Have you tried sudo apt update and sudo apt full-upgrade?

On 30/04/2020 at 16:35, WimH said:

Here's my attempt to link LSB and mV specs 🙂 Consider this as 1st-order approximation as it assumes e.g. ideal ADC being used etc.

Both mV and LSB quantify the luminosity response of a pixel under specific conditions, when expressed in mV the measurement is before the ADC (analog domain), when expressed in LSB the measurement is after the ADC (digital domain). There is no real way of comparing them unless we know for instance more about the ADC specs and settings used. IMX477 has for instance 8, 10 and 12-bit ADC settings. When looking at the IMX477 datasheet, it mentions 250LSB sensitivity and 1023LSB saturated signal. This means 10-bit ADC setting was used for the sensitivity measurement.

Furthermore, the datasheet mentions the sensor uses an analog supply voltage of 2.8V. Accepting that this is also the input signal range of the ADC (which is not 100% correct, but again, this is 1st order approximation), a 250LSB response at the output of the ADC would equate to 683mV on the input.

If Sony is really talking about mV per pixel and not mV per um2, this looks like an acceptable number, considering the difference in pixel area between both sensors (assuming both sensors have similar quantum efficiency and charge conversion rate).

 

Assuming these values are correct, if you bin the IMX477 at 4x4 the sensitivity would be 2732mV with a pixel size of 6.2x6.2um and an image resolution of 1012x760 which for the price is pretty impressive

And just to confirm what @WimH posted last week...... 200s exposures can be achieved with this camera module

Good stuff @Dan13....the video is great stuff and a helpful tutorial. The only difference here that the user needs to follow is 1) Open Synscan app on windows. Connect to mount in synscan app. And instead of selecting EQMOD ASCOM Simulator on the ASCOM telescope chooser dialogue just select SynscanMobile Telescope on the drop down list

Thanks @Dan13. For me I found for an AZ GTI you need to connect using the SynscanMobile telescope and the app needs to be connected otherwise this doesn't work.

Yes you use the app as a connection bridge. Once the mount is connected to PC with the app you can use the SynscanMobile Telescope ASCOM driver in any suitable program. Then you can happily control the mount in software like stellarium

With the synscan app for windows you need to leave the app open and left connected to the mount.

Once this is achieved you can then control the mount with any program that uses ASCOM using the SynscanMobile Telescope ASCOM driver

In Stellarium, go to configuration window. The go to plug-ins. The select telescope control. Then configure. Then add a "Telescope controlled by" ASCOM. Under ASCOM settings below press choose ASCOM telescope. Then select SynscanMobile Telescope. Give the scope a name an press OK.

You can then press connect and the status should change to connected.

The important step is to ensure you keep synscan open and connected to use any other ASCOM connections (using the driver Synscanmobile telescope) with other software e.g. stellarium, Sharpcap

The next thing you need to do is using Synscan app for windows, go to connect settings and select Serial and ensure the correct port number is selected

I did not have to play with any baud rate settings (the driver installed itself when I inserted the cable for the first time, and I did not alter the settings baud 9600, data bits 8, parity none).

If you can confirm that using the app you can connect to the mount and move it using the app then this would be very helpful diagnosing the problem 

I have this set up and all works fine in az mode

can you confirm you have this cable

https://www.firstlightoptics.com/sky-watcher-mount-accessories/lynx-astro-ftdi-eqdir-usb-adapter-for-sky-watcher-az-gti-mounts.html

13 minutes ago, discardedastro said:

Think I'll give it a punt. Need to work out how best to power it and keep it all dry, but I have some thoughts on that front, and can test easily enough on a dry night. Just going to get the "default" lens and I can go buy a C-mount fisheye later if the exposure settings etc work.

Edit: never mind, The Pi Hut are all sold out! Guess demand is high. Will watch the internet with interest. Also, I would've thought for basic use the indi_webcam driver would work for the Pi camera out of the gate - it's exposed as a v4l device.

If it works in indi, can do 30 secs exposure and sensitive then it will be a very cool gadget for all all sky cam

9 minutes ago, Gina said:

I'm not sure there's any significant advantage of using KStars/Ekos/INDI for an all-sky camera for capturing the images.  This is a much simpler application than standard astro imaging.  As long as you can access the RPi and camera over WiFi it doesn't really matter what software you use.  I think Raspian as OS on the RPi covers this but I haven't investigated.  I'm using INDI to control cooling and dew heater on my present ASC with a ZWO astro camera (ASI178MM or ASI178MC).  All this works fine using modified a Astroberry Board INDI driver for cooling and dew heater control.  I would like to use INDI with the Pi camera as I'm familiar with INDI.  Any other software would need programming the GPIO lines for cooling and dew heater control.

Completely agree Rasbian would be fine just for connect to over network. However, the advantage I found is that using INDI allows you to work with AllSkEye across the network on another PC.