M13 Globular cluster

[RogerTheDodger]

I can't believe 31st March was the last time I was out... Anyway, here is M13 from last night, 10 x 120s 800ISO.

I lost a fair bit of time due to USB problems, I think I nee to go to active cables as these 5m normal ones seem a bit finnicky.

Last night was also the first time out for my SW coma corrector and my QHY5 guide camera. I think the collimation is slightly out, but I'm concerned that the focusser tube is visible in the stars - any ideas on that?

[Stephen]

Lovely detail resolved in there Roger

You do have that hemispherical indentation in the left hand side of the stars I'd probably suspect the focuser tube too, but I'm afraid I don't have a solution for that.

[steppenwolf]

This is a nice image with plenty of star colour. There is a nip at 9 o'clock and would agree that this is most likely the intrusion of the focus tube which is tricky to resolve without machining.

You could adjust the primary mirror further up the optical tube to move the focus position outwards but this would have possible repercussions for sensor illumination as the secondary mirror would be intercepting the light cone at a wider point.

[RogerTheDodger]

Thanks Steve. I wonder why other people with the same kit don't exhibit the same problem? I'll look at shortening the focuser tube.

[Gina]

Very nice detail

[Quatermass]

Lovely shot roger so good to get out there again isn't it.

[RogerTheDodger]

It was indeed

[Gina]

Oh absolutely! Only trouble is that having been "grounded" for a month I need some time to get into things again.

[RogerTheDodger]

I know what you mean, I was out for nearly 2hrs before I took a single good sub... after that it wasn't too bad apart from the USB niggles I had.

[morimarty]

Hi roger,

I had this problem with my focuser on my 250pds.I did have to resort to a bit of machining though as steve suggests above. I stripped down the focuser and cut 10mm off the tube end, you will also have to move the two front bearings 10mm back, you will need to drill and tap these. it is not a big job but you will need a vice and pillar drill at the least. Nice image by the way!

[Tiddles]

Looks like you've got NGC 6207 in top left of the image too.

[Quatermass]

Yeah me too I was faffing around for ages before I got back into the swing of things

[RogerTheDodger]

Thanks for that info morimarty, I'll look into doing that at some point.

[Anweniel]

Yep see galaxy in the top corner too and the cluster is very impressive I think when you look at your webcam pics this demonstrates how good the DSO webcam shots you have taken are as they are not too disimilar. The focuser tube intruding on the pics must be a real annoyance, no need for pacman too have intruded Seriously though hadnt really noticed until you pointed it out but now that you have its hard to miss.