Hi Paul,

I'm trying out CCD-I to help collimate my C11 with Hyperstar. I acquire images from my QHY8 (OSC camera) with Nebulosity 2 which saves them as raw FITS files. This works fine for automatically calculating curvature and FWHM values etc. However when I try to use the real time collimation tool with a defocused star all I get is a black window. It blinks and shows an hourglass when the new image is detected but no image ever shows up.

I have uploaded two images, one was binned 2x2, the other is 1x1. CCD-I 'knows' I use an OSC camera but I now realize I should have disabled that on the binned image.

Is there any way to analyze collimation from a defocused star without using 'real time'? I couldn't figure that out, sorry.

Sorry, forgot to include the link with 2 images: http://cid-a93625fef5ca95fb.sk...aspx/CCD-I?uc=2&nl=1

Thanks,

Sander

Hi Sander,

I'm not sure what you mean by "no image shows up". Does the One-Star Collimation Viewer display a number and a direction? Does the color change to red after the image is picked up? Make sure it's the One-Star collimation viewer that is shown, and not the multi-star one.

Setting CCDI to Bayer matrix image type will have very little effect on the collimation viewer if the image is binned 2x2, or is, in reality, monochrome. It certainly shouldn't stop it from processing the image.

I downloaded your FITS files, and set up my CCDI to use Generic Camera driver, then selected a blank folder. I then opened One Star Collimation Viewer and real-time Image Viewer. I then proceeded to copy one of the FITS files into the blank folder.

The collimation viewer displayed an error of 7.8, and the image viewer displayed the star, the error and the direction.




Maybe you can describe all the configuration settings you use with CCDI, as well as the step-by-step procedure you use to do the single-star collimation.

Regards,

-Paul

sander.jpg (65 KB, 177 downloads)

Hi Paul,

ah, the key is the 'generic camera driver'. When I installed CCD-I I selected that option but somehow it still thought I had CCDSoft. Regular folder monitoring also worked fine so I did not suspect a problem with that setting.

I was able to reproduce what you did (blank folder, copy an image). Is this the only way to measure defocused collimation on an image that was already taken? Can't I just load an image and select 'one star collimate' somewhere?

Finally I read elsewhere on the forum that you measure collimation by looking at energy distribution rather than geometry. As you can see in my images I have a rather big shadow caused by the camera cables. Would this throw of the measurements?

Thanks!

Sander

Hi Paul,

update. I tried another image I took last night and this displayed 'all black' until I tweaked the range. Shouldn't it adjust the display range automatically?

Anyway, does the collimation indication look OK to you in the attachment? I uploaded the file (donut...) to the same Skydrive folder as before.

Thanks,

Sander

CCD-I_01.png (11 KB, 20 downloads) before adjusting range

And after adjusting the range

CCD-I_02.png (68 KB, 26 downloads)

Hi Sander,

One star collimation is only available as a real-time tool. I didn't anticipate anyone wanting to save and/or measure images of a largely defocused star. The generic camera driver is the primary way to get it to process from a file.

Defocused star tool does use energy distribution (flux). The actual geometry isn't important, unless the star is very far out of round. If that happens, CCDI will tell you that the star is mis-shapen.

The shadow from the camera/cable will have a slight effect on the calculation, but from your image, it appears to obstruct only a few % of the overall star flux, and so shouldn't matter much. Something like a hand in front of the corrector, on the other hand, will have a significant effect

It is important, to try to eliminate other bright stars in the image frame. While CCDI tries to focus only on the brightest object in the FOV and ignore all others, a close-by bright companion can skew the calculation.

Proper centering of the star is also very important.

Regards,

-Paul

Hi Paul,

so what about the two images I posted? Do those look OK? Shouldn't the black/white point scale automatically? Is the strange (to me) indicator in the second picture caused by the star not being 100% dead center?

This is an image of Vega so it's by far the brightest star in the image and should be easy to detect.

Thanks,

Sander

Hi Sander,

Display scaling is mostly automatic, but sometimes image contents can confuse the algorithm. I've loaded all three FITS files you provided, and they all scaled properly. I'm not sure what had happened with the one image that came up dark, but that's why there's a manual display scaling selector.

That said, it's not very important to look at the Image Viewer (or even to have it opened) while collimating. All the important information is displayed in the collimation viewer, and you can look at the star and its position on the chip in your favorite acquisition software, if you prefer.

The image seems OK to me. It is off-center from the chip, which is why the the cross-hair and the circle are offset relative to the star. The cross-hair is there to mark the center of the chip, and the circle is a guide you can use to help size the star properly.

The collimation adjustment arrow is always shown emanating from the star center.

Regards,

-Paul

Hi Paul,

Ok, got it. Mind that when things weren't working there's no distinction between a black screen because the image didn't load and a black screen because the range is set incorrectly. In the second image the same file is loaded but I manually fiddled with the limits to make the donut appear. So if this happens again I'll simply keep looking at the star with Neb while having the collimation window floating on top.

Alright, will try this again when the skies clear up.

Thanks for the help,

Sander