New to OAG - Eggy stars.. any quick start tips?

[Sp@ce_d]

I wonder if the OAG experienced could offer any quick start tips..

I normally use a finder guider (or ST80) but trying to reduce weight now I'm working on a triple shooter setup so I've got an SX USB Mini FW/OAG paired with my CoStar. I've had a go getting it running with PHD & have some pretty eggy stars @ 15min Subs.

Now on closer inspection i noticed that the guide stars on the PHD display appear to be slightly elongated too.

So, questions to start with:

Could this be caused by tilting/positioning of the prism by the screw lock? The column seems a pretty tight fit.

Would this have an effect on guiding.. I know PHD concentrates on the star centroid.

Any good starting PHD settings perhaps?

What else?

[Ibbo!]

yes its more than likely the prism.

PHD should be able to guide on it, it uses centroid guiding so do not saturate the guided star exposure.

I use phd on the grab and go mount and it has guided fine on eggy stars.

(I normally use maxim and it can guide on seagull like stars)

Steve

[ollypenrice]

I had to make a brace to hold the SX OAG turret anything like still. Yes, I'll say it. How do you manage to get the product so wrong? It really isn't very good, is it?

Later ones are supposed to be sorted. Do you think it could be a rocking turret?

Olly

[Sp@ce_d]

Yes I thought they were sorted. This is the mini FW with built in QAG. I'm just having a play in the obsy now.ok theres slight movement when its not tightened but it needs that clearance to slide up & down. I'm guessing to get elongated stars the prism would have to twist slightly. I've only had the one try so far so it could very well be my PHD settings as I've just reduced the calibration steps & min motion settings from those that I use for the finder guider.

I was just going to check guiding was fine with the finder/guider then switch to the OAG & test..., although the weather is ignoring the forcast right now.

[Sp@ce_d]

Hmm I have it running. Albeit on 2 min subs so far.. just trying a 15min at the moment. I think I know what it was, hopefully. I had the prism quite a way out and I think it was showing the curvature at the edge. I've pushed it further in as I'm only using the 314L+ so plenty of room before it blocks the sensor.

The graph is not quite the flatline I'm used to with the Finder/Guider

[Ibbo!]

I should have read your first message more carefully

I would believe that with the extra focal length phd will show more errors now

[Sp@ce_d]

Right... that's better..  a couple of subs.. just a gentle stretch

2min L

and a 15Min in Ha... (as the seeing is bad/clouded out and the Moon would wash out a Lum anyway)

[Sp@ce_d]

Well.. I thought I had it sorted...

Having another play as the Moons up & high cloud... Looks like the OAG needs further tweaking for overhead targets... such as IC1396 at the moment..

Guess I should try and get my head around tweaking PHD yet again..   I wonder if its time to look at PHD2 ?

OAG guiding 15 Mins

Finder Guider 15 Mins