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zwo asi 174

sooot

By sooot
in Discussions - Cameras

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JamesF

JamesF

Posted
Posted

So, fixed the EXCEL sheet. So, both the 120 and 174 are the same size eh? 

Learned a lesson not to trust the first link I find on the net  :tongue:

They're not the same size.  From memory the ASI120 has 3.75um pixels and the ASI174 5.86um.  The ASI174 also has a much higher pixel count than the ASI120 (1936x1216 compared with 1280x960).

James

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Luke

Luke

Posted
Posted

Here's my attempt to bring out a bit more structure with a sort of inverted version. Just a first shot, I could see from the image on screen that it looks a good cam, I need to tinker with gamma etc.. Anybody got an idea what a good "neutral" gamma for h-alpha should be? I think I used halfway.

15925892214_2ba89f257c_o.jpg

PS wife has four wheels now. Postage order will be restored in the Universe when Michael's 174 arrives! :blob7: Oh, and Shaun's Quark!

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Davey-T

Davey-T

Posted
Posted

Hi James, is there some simple way of calculating the focal length of an SCT after sticking filter wheel, 2X Powermate, camera on the back and cranking the mirror in and out to focus.

My B'Fly has 4.8 pixels which seems to suggest f/25ish but no idea what it ends up as.

Dave

Apologies to Craig for thread drift :)

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JamesF

JamesF

Posted
Posted

Hi James, is there some simple way of calculating the focal length of an SCT after sticking filter wheel, 2X Powermate, camera on the back and cranking the mirror in and out to focus.

My B'Fly has 4.8 pixels which seems to suggest f/25ish but no idea what it ends up as.

Not really, no.  The effective focal length is a function of (amongst other things) the distance between the primary and secondary mirrors which is information us mere mortals aren't likely to have.

The way I generally do it is to capture and process an image (of Jupiter, say), then measure the diameter of the planet in pixels, multiplying that by the camera pixel size to give the size of the image on the camera sensor in mm.  It's generally possible to look up the apparent diameter of Jupiter from the Earth at any given date and time, which gives you an arcseonds per millimetre figure.  Dividing that into 206265 gives the effective focal length.

FireCapture does actually do this for you and stick an estimate for the focal length in the data file accompanying the capture, as long as it knows what the target is.  I intend to do the same in oaCapture once I get my head around the necessary steps.  I assume it runs some sort of blob detection on the image and takes the average diameter in pixels, combines it with information it has about the camera and has some library for looking up ephemeris data for solar system targets to get the apparent diameter.

James

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Amra

Amra

Posted
Posted

This is a bit off topic, but do you guys know of a way to use these cameras (either a 1.25" or 2" adapter) with Canon lenses? I think it could be fun to use this sensor some time with a widefield lens or something.

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JamesF

JamesF

Posted
Posted

This is a bit off topic, but do you guys know of a way to use these cameras (either a 1.25" or 2" adapter) with Canon lenses? I think it could be fun to use this sensor some time with a widefield lens or something.

The thread on the camera body is a standard T2 thread as far as I'm aware.  There are converters/mounts that accept an EF/EF-S lens and convert to a T2 thread.  The tricky bit is getting the correct back-focus.  I believe it should be 44mm from the lens mounting flange to the sensor with an EF/EF-S lens, 17.5mm of which will get used by the body of the ASI174.

James

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Amra

Amra

Posted
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Awesome, thanks a lot.

Anyway thinking about it, my APS-C lenses are of course made for a much bigger sensor than ASI174MM, the Canon APS-C sensor is about 4 times bigger, so the FoV with ASI174mm would naturally be a quarter of the FoV I get on my Canon DSLR, so it might not really be that useful after all, maybe I need to look into lenses made for smaller sensors, if they aren't prohibitively expensive. 

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JamesF

JamesF

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It's not that uncommon to use DSLR lenses with CCD cameras to be honest.  It can work quite nicely with short focal length lenses.  Agreed you won't get the same field of view as with an APS-C sensor, but sometimes you don't need that.

James

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Amra

Amra

Posted
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It's not that uncommon to use DSLR lenses with CCD cameras to be honest. It can work quite nicely with short focal length lenses. Agreed you won't get the same field of view as with an APS-C sensor, but sometimes you don't need that.

James

True. Also the center of the lens provides the least distortion so that would be an added benefit I suppose.
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JamesF

JamesF

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It can open up the choice of lenses, certainly.  With my 450D and the stock 18-55mm lens there can be a fair bit of distortion around the edges of the frame, so I usually end up cropping images down anyhow.  Ok, so it's not a great lens to start with and you'd probably not use it if you had other options, but if it does the job with a smaller sensor then why not?

James

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rwg

rwg

Posted
Posted

This is a bit off topic, but do you guys know of a way to use these cameras (either a 1.25" or 2" adapter) with Canon lenses? I think it could be fun to use this sensor some time with a widefield lens or something.

I butchered a cheap 2x teleconverter to attach the camera to a Pentax lens - write up here : http://www.astronomyshed.co.uk/forum/viewtopic.php?f=35&t=24189

cheers,

Robin

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michael.h.f.wilkinson

michael.h.f.wilkinson

Posted
Posted

Here is my new toy in all its technicolor glory

post-5655-0-69513200-1424176327_thumb.jppost-5655-0-30684400-1424176337_thumb.jp

I was really impressed how it ran at 128FPS full throttle out of the box (12 bit ADC mode), without any issues at full res on my not top of the line Lenovo laptop. I did cut down the resolution to 1280x1024 to avoid sweet-spot issues in H-alpha (nothing to do with the camera), and increasing exposure time did cut the speed, but at 6.7ms I got 145 FPS on average on 1000 frame runs (results fit in RAM so HDD speed not an issue). At 16.7ms I got a healthy 59-60 FPS. I had no real issues with the (beta) software (FireCapture 2.4 beta7 and the new drivers). At one point I unseated the USB 3.0 connector, and FC would not easily reconnect. After restarting FC everything ran smoothly, and I had no further issues.

Very pleased indeed, and I wonder how it will do on planets. Maybe I can find out ths evening

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