Mono DMK as autoguider?

[Ben Ritchie]

Anybody using a monochrome DMK (with PHD) as an autoguider? I have the 640x480 one, and was experimenting last night with an 80ED as guidescope, but was surprised at how insensitive it appeared to be. I'm very happy with it in it's intended role as a lunar/planetary camera, so i'm wondering if i've messed something up.

By default it seems to set itself using 1/30s exposures, so I set it to 2s in the camera options window (button you click in the bottom right corner), and then set 2s in the main exposure time drop-down. That appeared to be refreshing the screen every two seconds, which looks right. But I still only picked up one or two suitable guidestars when pointing in a rich starfield, and none when pointing at M81. The contrast (?) slider on the main screen didn't really help much either.

Generally I guide with 15s integrations, so sensitivity isn't a problem with that, but I need to calibrate first and with multi-second integrations PHD seems to move the mount while the integration is in progress, so I get star-trails in the calibration process unless I use 1s integrations. That appears odd, but...

Anyway, is anybody using this setup successfully, and, if so, what have I messed up?

[Ant]

Hi Ben,

I use the DMK21 (USB version) as a planetary cam. I also use it as a guide scope.

Usually through a ED80 (f6.9).

I do agree that the number of guide stars available are low and I was expecting more than there were - I also use 2 second guide subs.

I always expected this cam to be more sensitive than it was - I always put it down to the fact that I was using an 80mm scope, and the fact that this cam was supposed to be used for lunar / planets.

Cheers

ant