My guiding graph from PHD

[swag72]

Perhaps my ongoing guiding and panicking saga is drawing to a conclusion. Last night I went through all the PA steps using PHD to check it and try to attain the minimum amount of drift. I was happy with the graphs and so decided to do some imaging.

I wanted to image M33 again, but this time without the CLS filter. So I set my remote and took 30 x 300s subs - Here is a copy of my guiding graph after 2.5 hours worth of guiding.

Anyone any comments?

[ashworthacca]

I've been getting 10 minute subs with nice tight stars and my graph is a mess compared to yours. I'd say you've cracked it looking at that.

[Whippy]

I think showing us the image would be better Sara .

Tony..

[swag72]

The subs are just being chewed between DSS as we speak Tony! I hope to have it up some time today, even if it is pants.

[Psychobilly]

Excellent... Time for less worrying and more imaging

[swag72]

Mmm, I hope so, but I am still seeing some form of rotation. Will post up image soon.

[Psychobilly]

Oh no

[martin_h]

Is is me or can I not see a graph?

[swag72]

Sorry Martin, should see it now, I moved it about in the albums!!

So, here's the awaited for image - A quick and dirty edit, please ignore the background 'issues'!! This is a full incropped image, I am looking in the bottom left and I feel that the stars are 'whooshing into the centre' - That's just for starters!!

[Psychobilly]

It doesn't look like Field rotation this time...

What was the setup used this time ?

[RobH]

The graph looks fine Sara....better than I often get with my AP1200!

What you're seeing on the image isn't field rotation, it's coma.

You need a field flattener with a DSLR sized sensor to deal with that.

Cheers

Rob

[Psychobilly]

Looks to me like soemthings not sitting square as well

[swag72]

I've got a .85 reducer - Is that the same thing? I didn't use it last night as I wanted to use the full 900mm and that takes it down to 720mm.

That can only be the camera really that may not be square as it's not a screw in thread. I thought I had it square in though.

[Psychobilly]

yep.... your better off using it and cropping the image

[swag72]

OK that's good to know. Cheers.

So you reckon my field rotation problem was fixed last night?

[Psychobilly]

yep

[martin_h]

I would use the reducer, if you read the bumpf for it - "Effectively reduces the telescope’s focal length by a factor of 0.85x and provides much improved field-edge correction"

[martin_h]

Also, by using the reducer screwed directly to the focuser and the dslr mounted directly onto the reducer, everything should be fairly square to each other.

[swag72]

Would I have to use a reducer on all scopes or just the 120ED? I ask as there's really little point in having 900mm if you can't use it!!

Mmm, food for thought for tonight - Longer subs me thinks!!

[Psychobilly]

Give me 720mm and a flat field over 900mm and a curved one any day...

[martin_h]

You dont have to use it at all, just get your image centred a bit better and crop the dodgy bits off the edges. But the reducer will make the scope that little bit faster!

[swag72]

Thanks so much - I really wouldn't be at this stage without your help.

[martin_h]

I have the 80ED and the 100ED and use the reducer on both. I still crop the image slightly(for missaligned frames ect)

[Psychobilly]

For framing take short test exposure at the highest ISO you camera will go to... remember to drop it back before capturing the proper data...

I normaly compare the brightest stars against a quick sketch if I havent got the lappy with me...

[Digz]

I cant seem to see the graph either. Im interested in this as I am about to venture into guiding once the skies clear so would like to know what I should be aiming for.