I was about to try an 'in camera' stack using the multi exposure feature on the pentax k50 when the clouds rolled in. But before they did, I got a single 5 minute exposure through the sigma 70-300 at around 200mm f4.5. ISO 800. bit of ghosting on the brighter stuff and a bit of CA too but having said that, it is 'only' a $200 lens. Keen to see what happens if I stack half a dozen or so images in the camera. Note to self: must download DSS soon too!
Yes, good start, but I'm curious to know why you felt it necessary to
guide at all. If your polar alignment is good you should be able to
make 8 - 9 min. exposures at 200mm.
raymo
My polar alignment may well be a little off plus I can actually see the star 'wobbling slowly' inside the illuminated square of the eyepiece so I don't think my gearing on the HEQ5 is accurate enough not to guide. Having said that, I don't think I've recently tried 'not guiding' on, say, a two minute exposure.
Lots of experimenting to do. Got 6 x 2 minute photos last night and stacked them in DSS - the result was slightly better than my single exposure after a bit of PS'ing. Next time, I'll turn the noise reduction in the camera off and do a few dark and bias frames and that way I should get a lot more done instead of waiting around for the in-camera noise reduction.
Well, this was 6 x 2minutes at 200mm. My polar alignment is definitely off as I can see movement between the frames so a bit of tweaking to be done before the next session. this is my first effort with DSS and automated stacking - it's a little better than the single 5 minute shot.
Even if your P.A. is not that good, you should be able to get far more than
two minutes at 200mm. Maybe your rig is too well balanced. You need a
bit of weight against the drive to keep the gears firmly meshed. Some movement within the centre square of the reticle is o.k. especially if you
are using very high power to guide with.
raymo
Something screwy is definitely going on with the mount. Spent an hour last night trying to drift align it....it would start off drifting a little to the left, then I 'd have a look a minute or two later and it had reversed and gone the other way! I'll try slightly unbalancing it next time and have another go. Clouds rolled in 4minutes into my first exposure. Guiding at 100X.
