Qustion about PHD Guiding

[BlackWidow]

:help:My first night of trying to get my guiding system up and running. I have never done this and have a qestion. I am trying PHD and using an LX modded Philips SPC900nc Webcam. I am looking at Sirius at the moment and have been able to lock onto the star with PHD and have it set to frmerate of 1.5. Is it normal for short moments of star loss (picture loss) is this when the LX exposure resets? or should I never loose the image even for a split second?

Also I am not sure that the SPC900nc is going to be light sensitive enough to pick up stars in faint areas when I do deep space images..


Any advice would be be a help so I can get my head around the guiding process


Regards
Martin

[Moon]

Martin,
The image should not be lost. It should look like a normal video stream, but with a frame rate that you specify. On Sirius you should be able to have a much faster frame rate. From memory, the number you select is the duration of each frame in seconds, so try 0.1 or 0.01 on Sirius. 1.5 seconds is too long.

I occasionally struggled to find guide stars with an unmodified SPC900nc. In comparison I found the QHY5 much easier to use.
James

[[1ponders]]

Hi Martin, unless you use very short exposures sirius will be far too saturated to be really effective as a guidestar. I use both ToUcam 840 and 900 unmodded with guiderings and its very rare that I can't get a guidestar to use with 1/25 sec and 5 fps and gain around 80%. Having said that longer exposures would be prefered. A 1 sec exposure should get you stars just about anywhere.

[BlackWidow]

Thanks guys I will go back outside and try those options. I have just downloaded Guidedog and that seems to bee working fine. I just had to swap the east west settings and it seems to be working. I will also go back to PHD and try that again also.

I have a full version of K3CCDTOOLS and have not tried that yet. Want to keep it simple but still get a good result. I will have to play some more to work out which one works best for me...


Thanks again as you advice does really help


Mardy

[[1ponders]]

K3 is a great program, I used it for quite a while when I first started astrophotography. But since PhD came along I haven't gone back to it.

[BlackWidow]

Thanks paul. I found that Guide dog was difficult to understand orientation. K3ccdtools seems to hold the star in the cross hair without any problems and I can see the N nudge button light up ever so often showing the corrections.

I went back and gave PHD anothe shot. It is a simple interface to use. When I selected the star it seemed to do a setup where it nudged north and south etc. then is said Guiding and went about holding the star in the cross hair. I do get a beep from my computer and the bottom of the PHD display flashes red. It happens just for a millisecond every so often.. Is this part of the program and is what it does?


Regards
Mardy

[Moon]

That means something bad happened (low SNR of the guide star). Usually the star was not bright enough. Try making the exposure longer.
0.5 sec is a nice guide rate to try.
James

[xcoupeb]

Im having the same problem of dropped frames with phd and modded spc900nc. i have read somewhere on the net that in the brain menu the time lapse setting should be 20ms+ and also the le read delay needs to be played with so the frames dont drop. I havent had a chance to try it as yet but hoping thats the issue. i too have played around with frame rates and gain etc but nothing stopped the dropped frames.

[mithrandir]

What version of PHD is it? The first couple of versions with "star mass tolerance" calculations (1.12.1 and 1.12.2) have trouble with poor seeing changing the size of the guide star. 1.12.0 doesn't use it. 1.12.3 you are supposed to be able to turn it off.

See the http://www.stark-labs.com/prerelease.html page.

Andrew