blinky Posted January 18, 2010 Share Posted January 18, 2010 Normally when imaging I have the guide cam set to exposures of 1 second but tonight when doing that it's all over the place. Now what I normally do is assume the problem is my polar alignment and I drop the exposure to 0.5secs but tonight this made it worse so..... I upped it to 5 seconds and it seems a lot better. Weird huh?Do you experienced imagers reckon this is down to bad seeing?Here is a 1sec guide and 5 secs guide image to compare. Link to comment Share on other sites More sharing options...
greenkat Posted January 19, 2010 Share Posted January 19, 2010 No idea as to the cause of your problem but a definate improvement in image 2And its a nice image as well , bonus Link to comment Share on other sites More sharing options...
jgs001 Posted January 19, 2010 Share Posted January 19, 2010 That certainly made a difference Craig as to why... I've no idea... but I'd be interested to hear. Link to comment Share on other sites More sharing options...
themos Posted January 19, 2010 Share Posted January 19, 2010 Hm, the drift looks to be in the SE-NW direction, I don't think it's seeing related. Link to comment Share on other sites More sharing options...
MartinB Posted January 19, 2010 Share Posted January 19, 2010 Lengthening the guide exposure makes a lot of sense when the seeing is poor. The rapid scintillations are averaged out making the centroid a more reliable indicator of the true star position than when using a 1 second exposure. I never use 1 second exposures these days, 3-5 seconds is plenty short enough for most reasonable mounts Link to comment Share on other sites More sharing options...
Catanonia Posted January 19, 2010 Share Posted January 19, 2010 I agree with Martin, if the seeing is bad i tend to have to go from 1 second to 2 or 3 seconds.I like to stick with 1 second, but sometimes it is not possible.If i get this situation, I check the lense and clip filter to ensure not misted over or frosted, and if they are clear, then more than 1 second on PHD via the guide scope is a definite indication to me that it is misty /foggy and so bad seeing compared to normal.Sometimes it looks clear on a zero moon night, but you can't see the mist or thin cloud layers. PHD will see it via the short exposures as the average is much less. Having to up the rate means it needs more data and all things being equal means the starlight must be blocked by something. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.