Help required with Long Exposure Webcam settings

[Screwdriverone]

Hi All,

Now that I have (hopefully) sorted my tracking motor issues on the Eq2 (yeah I know its crap) I would like some advice on the best settings for the Toucam to take long exposures of say, M42 and globulars etc.

In the past when trying this, I have been unsure of what to set the gain and gamma and shutter speed (probably doesnt apply I know for LE) to get the best LE subs.

Apart from Darks, flats and bias frames etc which I will worry about later, what should I try for a passable LE shot of M42, should I set the LE time to 20 secs, and take craploads of them or try for longer but take less shots?

Can anyone assist please? I am hoping to get some practice in on Saturday night so any tips would be great.

I have heard people say that without tracking you can get up to 2 minutes only, but I cant get anywhere near this without trailing stars of some description, even when the mount is spot on with drift alignment. I assume they mean without AUTOGUIDING? The issues with my gears are hopefully sorted now so I should be close to spot on dead centre for minutes at a time with the RA motor on.

Before you suggest an HEQ5 pro or better, no money for that, also considering that its a waste of time mounting my SW135 tube on it but thats another story.

Thanks and cheers

Chris

[renormalised]

Maybe no money for a HEQ5, but what about an EQ5??. Heavier mount and you can get Synscan for it. Andrews is selling the EQ5 for $299 with an aluminium tripod ($399 for steel one). You could get the Synscan later.

How long can you track for before you start to get trailing??. You could take heaps of 20sec subs and then stack them. But you would be better off if you can get 60sec subs without trailing. The longer you can expose for, the better your piccies should turn out. I'd suggest you try some images out for field rotation and trailing, just to see where and when it starts to occur with your setup. Then you'll know what to avoid.

[Screwdriverone]

Thanks Renormalised,

Yeah, I could get an Eq5, but the minister for finance has just approved the funds for a very special Dobsonian purchase today so the available budget is going into that, stay tuned for more exciting developments on that front tomorrow......

Whats I found is that even on a 20 sec exposure, I was getting "jitter" from the drive gear on the RA wheel, caused by some minor damage that has been happening while I have been slewing around with the drive motor disengaged but still too close to the wheel and burring has resulted in some spots.

I have rectified this with a nail file and by extending the drive wheel off the shaft slightly by loosening the allen key that holds it on so that the drive wheel and the driven RA wheel are matched up in the MIDDLE instead of only the last third of the motor wheel touching the big one.

A quick check shows me that the drive looks smoother now, the consequence of it before is that it looked like the trapezium stars in M42 were smudged in little squiggles as the motor turned causing the LE trails.

Not so much as a long trail in one direction, but more like a little kid's crayon scribble, even on subs as short as 10 secs.

I havent yet tried it out again to see if its improved, but more to the point I want to check what settings for gain and exposure I should use, should I set the gain in the middle for short and low for long subs? or just leave it for all and experiment.

I am trying to shortcut the guessing game so if anyone has practiced this and perhaps mastered it, let me know. I am off to trawl Mike's guides and see if he mentions it at all.

Thanks for commenting.

Chris