Using CCDinspector to collimate a scope

[gregbradley]

I was using CCD Inspector a few weeks ago to collimate my CDK17.
It seemed fairly helpful except it was not totally clear in which direction to adjust the secondary as it shows a 3 knob secondary collimation setup whereas the Planewave has 4 knobs.

My question though is how reliable are measurements from CCD inspector?

If I got a result that seemed odd I would repeat taking a fresh image and measuring it. Sometime I got the same result other times it would be different.

So the bottom line seems to be use it as a guide and only on a night of good seeing.

Would it be best practice to then collimate with a high powered eyepiece on a night of good seeing?

Greg.

[Paul Haese]

I have never found it to be reliable Greg. It will get you close but the best way is to get an image of an out of focus star in the centre of the frame. Make an adjustment, return the star to centre and repeat as many times are necessary to get collimation nice. Al's collimation aid also helps too.

I use Maxim so I can have the cross hairs to centre the star. I set maxim to focus mode and then just repeat. It just chugs along and I make the adjustments I need to make.

[DavidTrap (David)]

Hi Greg,

I used a method of collimating my RC as described by the manufacturer, deep sky instruments.

It uses out of focus stars and described how to adjust both primary and secondary mirrors, based on the shape of the doughnuts and the asymetry of their brightness. When I checked the result in CCD inspector, it gave me an almost perfect score. CCD inspector gives very weird results on tight clusters or nebulae. Best results are on open clusters.

The methodology explains why a collimation scope may not be your friend either - mechanical vs optical alignment.

Happy to send it to you - if you send me an email, I'll forward it to you.

DT

[gregbradley]

Originally Posted by Paul Haese

I have never found it to be reliable Greg. It will get you close but the best way is to get an image of an out of focus star in the centre of the frame. Make an adjustment, return the star to centre and repeat as many times are necessary to get collimation nice. Al's collimation aid also helps too.

I use Maxim so I can have the cross hairs to centre the star. I set maxim to focus mode and then just repeat. It just chugs along and I make the adjustments I need to make.

Good advice. Thanks Paul.

Originally Posted by DavidTrap

Hi Greg,

I used a method of collimating my RC as described by the manufacturer, deep sky instruments.

It uses out of focus stars and described how to adjust both primary and secondary mirrors, based on the shape of the doughnuts and the asymetry of their brightness. When I checked the result in CCD inspector, it gave me an almost perfect score. CCD inspector gives very weird results on tight clusters or nebulae. Best results are on open clusters.

The methodology explains why a collimation scope may not be your friend either - mechanical vs optical alignment.

Happy to send it to you - if you send me an email, I'll forward it to you.

DT

PM Sent. Thanks Brett.

Greg.

[Joshua Bunn (Joshua)]

Cant really comment on CCDIns for collimation, but I would second Pauls Advice. Then what I do after that is bring a star field to focus then adjust the secondary collimation bolts based on the star shapes in the corners of the frame, rotate the frame 90 deg and check again. Since you use a square detector, this may not be a step you need to do, bit the stl11000, yes. draw some diagrams that show you which collimation bolt does what to the star field through trial and error. It's quite sensitive I have found, and I think the 4 bolts make it easier than 3 since 4 bolts mean the collimation axis are orthogonal to each other.

Josh