autoguiding first light

calypsob

Ok so I bought the asi120mm to replace my SSAG as an autoguider. I did not realize that this camera was going to be so noisy even when it is 36 degrees farenheit outside. I took 50 dark frames and it did not make much of a difference. Once I began guiding phd 2 would say star mass lost. It also crashed phd 2 about 12 times, it would just freeze up. I spent about 12 hours in total over the past 2 nights trying to get this camera to work and I have done nothing more than loose 2 perfectly clear nights. I would really like some input on autoguiding with this camera. My gain was at 43 and my exposure was 1 second. Gamma was a little bit less than half and I took 50 darks.

Sam@ZWO

36 degrees is already very hot! a lot of hot noises will be there when do long exposure like 1s.

but the guider port of ASI120MM should be full compitable with SSAG.

if this freeze issue only happen when guiding. you may need to check your power source, is there any power leakage happen, Is the computer and mount grounded well?

calypsob

sorry, it would be 2.2 degrees celcius ambient temp. Sensor was reading 14 degree celcius. I am not sure how to check for grounding, I use a 12v deep cycle battery to power my laptop, this connects to the battery through a male cigarette lighter. I never had this problem with the orion ssag, is the asi120 designed differently? I am hoping to rule this out as user error by doing more tests tonight. Any additional advice or information about future software updates is appreciated. Thanks

calypsob

- Ok I am at home now testing the camera, it seems I may have been estimating the exposure capabilities of the camera incorrectly, at least I hope. I am in a dark room at my house using the fisheye and have gamma at 90, gain at 55, and exposure is at 7ms. I set phd to its fastest exposure time .0001 s and the laggy problem went away. I have taken 50 darks and the noise improved dramatically, even with sensor temp at 42 degrees Celcius. I think that asi 120mm users would greatly benefit from a histogram in the cam dialog application in phd.

- I will try again tonight and see if I can hopefully get better results. theoretically, should I be able to achieve the same on screen quality as my old ssag? At this point I am beginning to wonder if a 1 second exposure was just way longer than I needed.

- What is the aperture of this fisheye lens? that will help me do a better job of judging exposure times as well.

- Also, when I am using the st4 cable from the camera to my mounts autoguider port should I select asi st4 ascom, usbst4, or On camera? So far I have only used the ascom connection.

Sam@ZWO

the sensor on ASI120MM is much much better than SSAG.

So you will get a better result definilty

What is the aperture of this fisheye lens? that will help me do a better job of judging exposure times as well.

the aperture of the lens is F2. but the brigness of a star is mainly depends on the diameter of your guider scope instead of the aperture.

Also, when I am using the st4 cable from the camera to my mounts autoguider port should I select asi st4 ascom, usbst4, or On camera? So far I have only used the ascom connection.

just select on camera if you use the ASCOM driver.

more detail can have a look at here:

http://www.zwoptical.com/Eng/Cameras/ASI120/software_autoguider.asp

chripell

Hi, just my 0.02€ about guiding with the ASI120MM. I use OpenPHD modified for directly accessing the camera (no INDI/ASCOM/other middleware: they just introduce unnecessary lags): http://www.evolware.org/?p=305 The guide scope is a 80/328. I'm using an exposure time of 1s and binning because otherwise I have a very high oscillation index. Of course I keep gain very low in these condition because the guide scope is fast. For the same reason I reduced AR agresivness (i don't remember if to 95 or even 90). The problem of oscillation was only on the AR axis, not the declination one. I was thinking the reason for this was bad seeing but perhaps you're right, it could be a noise problem. There is a filter knob that can select between median and mean filtering but I don't remember if they were useful. Another strange thing is that I had to decrease "calibration step" duration, otherwise OpenPHD didn't get AR and DEC axis right (it's easy to check, just align the camera by rotating it before guiding and enable the showing of the grid). I guided a 6" f/4 and a Nikon D5100 on a NEQ6 for 5 minutes with round stars (under the skies where I live, longer exposures are useless at unity gain of the camera, 800 ISO). Of course I turned off autoguiding (just to see how good my polar alignment and PEC correction is) and with just one minute I got an interesting surrealistic painting but with no scientific value :-)

calypsob

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calypsob

Ok I was pretty confused about what I am supposed to do with all of the information in the link so I just went back to using phd 2.

Yesterday I had problems with phd crashing every couple of minutes and I realized it was because I had the framerate set to high and I was binning. It was kind of incredible to watch actually, really puts the power of this camera into perspective. I had the gain set to 1 with 640x480 binning turned on. I had camera dialog set to 200ms and I set the exposure in phd above the phd gamma control set to .0001. My calibrations steps were explosively fast and my phd graph was blazing along much faster than my old ssag which was doing 1 exposure per second. The star preview window would flash white and the whole screen would go crazy. as PHD tried to keep up with autoguiding results. I was getting a really good graph and really round stars though so I was impressed. I imagine that the camera was spending alot of time guiding on the seeing so next time I am going to set up the camera to not do binning and I will use slower exposures. I would love to see craig stark write an adaptive optics feature to utilize the speed of this crazy little camera.

Speaking of adaptive optics, I launched Metaguider after I gained a some familiarity with this camera and boy does it work well with the asi120mm. It took me about an hour to get the settings figured out, but once I got it to work my guiding was great. The only problem I have with meta guide is that you cannot dither like you can when using phd, so you get stuck with alot of noise in the final image which cannot be stacked out. Here is about 50 minutes of Ha I got on the veil yesterday morning autoguiding with the asi120mm

~~Veil Ha by LMNO Sunset Deluxe, on Flickr~~