QHY5v Guider set up

[obscura]

I have read that the guider usually works first time.

I gave mine its first airing last night and am puzzled as all I appear to get is just noise like an untuned tv. It was attached at prime focus on a ST80 tube, scope on, eqmod/cduc/aascom and PHD. Exposure settings didn't appear to make much diff from 0.2 to 5 secs - but I never altered gamma. I racked the focusser took a dark but still no diff. There appears to be a number of hot pixels albeit small.

The guider hasn't been dropped etc etc.

So what could be wrong?

If clear again tonight I will give it another whirl.

[jgs001]

I get the same thing with mine with a fresh install of PHD... adjust the screen gamma, so the slider is fully right. The darks normally take care of most of the hot pixels/noise issues for me without a problem. Make sure you adjust the calibration step in the PHD Brain, otherwise, with the ST80, the mount won't move far enough to complete the calibration in the allotted time. A value of around 2000-2500 works nicely for me.

[acme]

Oldgit,

Do your testing in daylight, it may be just a focus issue. I had the same problem on my first outing only to find it was because I could not get enough back focus. I unscrewed the optics off an old cheap barlow and it works just fine. The ST80 and the QHY5 is a great guiding setup.

Hope this is of some help.

Acme

[obscura]

Hi John. Many thanks for your quick reply.

I'll try that out as soon as possible - I'll post results.

Rgds

Brian

[obscura]

Hi Acme.

I believe things are looking up. With John's suggestions and a quick trial as you suggest - a black screen (camera covered) with no hots in sight. Now await a clear dark one tonight. Thanks for your input - its good to know others have had this and not just me.

Brian

[acme]

Brian,

That's good news matey. Keep the back focus issue in mind though, don't end up loosing another clear night trying to find focus on your guide star. If you don't have a 1.25 50mm extension tube then do try the barlow barrel method to get the correct distance. You won't need a diagonal either so that helps reduce the chances of differential flexure.

Acme

[jgs001]

Brian, something else to think about, as Acme said... even with the screen gamma set that way, if the image is out of focus, then it will appear noisier, so can be quite a good guide... Keep either a barlow, sans lens, handy, or worst case, the diagonal... you shouldn't use a diagonal, but it'll do in the meantime, if you can't get focussed... I used a prism diagonal till I got the extension tubes sorted out, and that worked fine, albeit somewhat weighty ...

[Photosbykev]

when you connect to the QHY5 under properties I ramp the gain upto 100% rather than the default 50% and then find with a 3 second exposurs I have a reasonable chance of finding a guide star.

As other have said you will need extra out movement on the focuser, a lens-free barlow tube is ok and I use one but a 50mm extension tube would be better as the drawtube wouldn't be extended as far out of the scope body. Dark frames also help and note until the stars are very close to the correct focus point you won't see anything.

[obscura]

Many thanks. I finally got out there and got it all to work together. Result was very good with a decent black sky pincushioned with hundreds of stars. Only used for this outing a Canon 80-200 set at 80 and anSW LP filter piggy backed. Next time will be with the 350D at the WO 80 prime focus. Centre stars were v. good but not unsurprising, edge were a nadge distorted. But I am chuffed at this first image.

This could not have happened without all the help received from SGL.

Many thanks again.

Brian

[jgs001]

Nice one Brian... You can "correct" the edge stars using the filter, distort, lens correction filter in processing... You will lose some of the edge, but it's better than cropping.

[obscura]

I'll have a play with that but I will keep the original for posterity. (May well turn out to be my best)

Rgds

Brian

[obscura]

I did use a diagonal on the focusser but have taken note on extension tube or a Barlow barrel 'sans' lens. Fortunately, I have a cheapy barlow which has been suitably cannabilised and will use that next time round.

Thanks for the tips.

Brian