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Is this bad collimation?


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Hi, I had my first light with 130PDS and HEQ5 about two months ago:

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It's not great, and my processing leaves alot to be desired, but my main worry is the halos around the stars. I thought I wasn't meant to be getting that in a reflector. I don't think it's coma as I don't get coma using this cam (Atair GPCAM) with a 130p. Could it be due to seeing conditions or collimation? The halos are in single subs so I don't think its the stacking.

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3 minutes ago, michael.h.f.wilkinson said:

All scopes will get some degree of halos around bright stars, these are just the "wings" of the point-spread function of the optics (Airy disc). What I do not see is a coloured halo around the stars, which you do see with many refractors (often blue)

Fair enough, the stars still do not seem right though. Could it be tracking? Or could it be the seeing conditions?

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I don't think it's collimation, as that would result in non-circular stars and the halo seems fairly circular, at least in the centre of the image.

I do see what looks (at least to me) like coma at the edges. There seems to be a bit of a cometary shape to the stars, most noticeable in the halo.

Agree that the stars do not look right. There is more light in the halo than there should be and a bit of a "separation" between the star and the halo. Not sure what could be causing that - won't be tracking. Seeing conditions could contribute. Was it damp where you were - wondering if fogging on your optics could have added to the effect?

Billy.

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Looking at some of the largest brightest stars in bottom left corner looks like either seeing might not been so good or perhaps your glass isn't as clean as it should be but the stars their self show good collimation . I use a Clear Sky Chart to see how clouds and seeing is . If you have one close by you can use it to check seeing . 

 

http://www.cleardarksky.com/csk/

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I think it was a bit damp but I was using a dew shield and that seemed to be doing it's job. It could be possible that the sensor could have fogged up. The 130PDS is brand new and spotless. I'm giving it another go tonight so we'll see how it goes. It seems that collimation isn't the problem so thanks for the replies, hopefully tonight seeing will be better.

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