calibrating PHD with QHY5 and 50mm finder

[libraryman]

It as clear all last night but i spent too long trying to calibrate PHD, 60+steps..then failed due to lack of star movement??

Reading through previous posts it's clear that it can work and iv'e tried different settings as advised in the posts.

The stars are tight on the screen and selecting a star does not seem an issue, i'm useing 2.5/3.0 exposures and i get the crosshairs indicating calibration started.

i have run the manual guide facility and get movement on the drives so communication does not seem to be an issue, however.. when auto calibration is running i do not feel any pulses in Dec.

I know that polar alignnment is not perfect and this might be an issue but it's not far off and i get 30 subs unguided.

frustrated and tired at 5:00 this morning i need a little help to bottom it, any advise on settings etc appreiciated.

Ray

[swag72]

Can you do a quick screen grab of the settings in the 'brain icon'. I use a QHY5 and 9x50 finderscope and I've yet to fail to get a star. If you are using a finderscope, then you need to be looking at really upping the calibration steps in the brain icon. Mine is set at 2200.

Infact, I'll do a quick screen grab in a bit. That will show you the settings I use and I calibrate within 10-12 steps.

[swag72]

Here's a screen grab of my settings in the brain icon. Guiding with the QHY5 and 9x50 finderscope. Hopefully this will help you and others who use a similar set up who struggle for calibration and settings.

[adamsp123]

Yes first step is as Sara said, up the calibration step till you get the calibration done in roughly 10-20 steps.

Secondly set your minimum motion way down for a finderscope, I have mine set to zero!! but 0.05 will do.

Thirdly make sure you are using fairly long exposure times to allow PHD to calculate the guide star centre without the affects of seeing, so 3 secs or longer, I now go for 4 to 5 secs.

HTH

[libraryman]

Hi Guy's i think i've attached a printscreen of my settings, thanks for the advise i'll give it a try next chance i get.

you can see that my settings differ greatly from those that your useing but i did take these settings from a previous post.

My guider is the 8x 50mm type, i dont suppose that makes any difference.

one thing i'm uncertain about is the star feild that i see,, they are very tight..small and in fact mere dots and i wondered if they are too small?? although as iv'e said i am able to select on one to guide.

Ray

[swag72]

I do believe that PHD will guide better if the stars are out of focus slightly.

[libraryman]

Cheers Sara, is that what you find yourself, Do you need to defocus slightly?

Ray

[swag72]

I don't think it's intentional, but yes, my stars are oof!! Never failed yet though!!

[libraryman]

Ive just come across the graph tool, any idea how i can use it?

Ray

[step_hen]

Are you sure you havent selected a dead pixel- fooled me many times!

Stephen

[libraryman]

Hi; to be honest it would not suprise me, i find it hard to tell what i'm picking up on, as i've said the stars appear very tight, Strangly i am thinking that the stars i thought i was useing ( and i tried many times) did appear to be in the same area of screen if i recall correctly.

is there a way of telling?

Cheers Ray

[step_hen]

real stars will move if you tap or wobble the scope. Dead pixels will stay in the same spot

Stephen

[libraryman]

I should have thought of that Duh!!!

Ray

[Skuber]

You might want to consider pointing it at a bright star to get the focus first - that way if it's out of focus, you should still see something which will help with the focus.

Also, if you are getting dead pixels, then I think they can be subtracted if you take dark frames first - the dark frames should clean up the picture a little as well.

[libraryman]

Cheers Skuber. i'll give that a try, one of my concers are the number of apparent stars in the feild, i'm sure some of them could be hot pixels.

Ray

[GrantEb]

Taking a dark frame should take care of most of the "apparent stars".

HTH

[libraryman]

Cheers, now i'm waiting for another clear night, tommorrows looking hopefull!!!!!

Ray

[libraryman]

Yeh it all works now; thanks a lot for all the advise, got an imaging run going on M82/81.

calibration took little more than a couple of min's one of the main problems was focus, once that was sorted of i went.

Thanks again Stargazers rocks.