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RC12 images show cureved banding

Ritchey-Chrétien NGC2736 Nebula Deep Sky NGC Objects
Ritchey Chretien telescopes GSO Family •8 replies•160 views
Brian Boyle avatar
Brian Boyle avatar
I have recently upgraded to an RC12, and the initial commissioning went very well.  I was able to produce a good NB  image of the Pencil nebula.   

But for my first LRGB image (Thumbprint nebula in the Chameleon Cloud 6hours total exposure), I ended up with this horrible curved banding structure.  This is not in my flatfields - but in the lights themselves.  Most obvious in B and L sub-frames and less obvious in G and R.   To me this looks a lot like a stray light problem - and I know that the RC 1ary mirror baffle has had issues before about not being long enough.  When I asked my telescope supplier the said that the problem had been fixed, but this image *might* suggest otherwise.   

Has anyone seem a similar thing with their RC12?  Is this a 1ary mirror baffle problem,  or is it something else?  

Thanks is advance, 

Brian
scatteredlight.jpg
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meteoritehunterjim avatar
meteoritehunterjim avatar
Hi Brian, It was a baffle problem on my 10 inch RC and that of Paul H. We posted a long series of posts a couple years ago in the forum here. We got a baffle for the secondary which was much better than extending the primary baffle. It cut out nearly no good light but took away the problems of the arcs in the corners. Sorry i don't have time today to look up the link for the topic from two years ago. This is the product we got for the 10 inch I would guess they make one for the 12 inch.

https://app.astrobin.com/equipment/explorer/accessory/19999/ts-optics-light-shade-for-the-baffle-tube-of-10-rc-telescopes

Good Luck, hope you can solve the problem it is nasty and hard to process out.
CS,  Jim
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Brian Boyle avatar
Brian Boyle avatar
Thanks Jim. 

Its funny, but I thought someone was up when I did the collimation, as I could see the 3ry reflections of the spider between the 1ary baffle and the secondary.  

On my RC8, I had to remove the 1ary baffle before I could see the reflections, so this make me wonder whether the baffle was indeed too short on the RC12.  

Need to hunt down that 2ary baffle.


Thanks

Brian
Mario Wunderlich avatar
Mario Wunderlich avatar
I had an issue with the baffle length and aperture of my 16" RC.

I didn't have banding, but instead every sub was affected with a pronounced dark halo around the center, which couldn't completely be removed with flats. My solution was a bit artisanal… I purchased a 16" extension (which on its own wasn't enough to fix the problem) and a 12" extension. I attached the 12" extension to the front of the 16" extension, in order to extend and taper. This completely fixed the issue.

It took me a while to figure this one out, so just thought I'd share in case it helps anyone.

Best,

Mario
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Matthew Proulx avatar
Matthew Proulx avatar
Brian Boyle:
I have recently upgraded to an RC12, and the initial commissioning went very well.  I was able to produce a good NB  image of the Pencil nebula.   

But for my first LRGB image (Thumbprint nebula in the Chameleon Cloud 6hours total exposure), I ended up with this horrible curved banding structure.  This is not in my flatfields - but in the lights themselves.  Most obvious in B and L sub-frames and less obvious in G and R.   To me this looks a lot like a stray light problem - and I know that the RC 1ary mirror baffle has had issues before about not being long enough.  When I asked my telescope supplier the said that the problem had been fixed, but this image *might* suggest otherwise.   

Has anyone seem a similar thing with their RC12?  Is this a 1ary mirror baffle problem,  or is it something else?  

Thanks is advance, 

Brian
scatteredlight.jpg



Brian, I am a RC12 owner and this looks to be an issue with the baffle not being correct. The RC12 truss seems worse than the tubes because of this. Mine is a 2022 model and as far as I know this issue is not corrected. My 2023 model RC10 neither. I have buckeye 3d printed baffles in both.
I did briefly have 2 newer RC8s in 2022 and they were corrected. It's possible they didn't update the 10s and 12s yet, I don't know. Either way these work on mine.

https://buckeyestargazer.net/Store/GSOBaffleEXT.php
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Brian Boyle avatar
Brian Boyle avatar
Thanks Matthew. I now have the baffle extension piece from Telescope Service, and it works perfectly.

Interestingly, my retailer (despite at first denying it could be a baffle problem) contacted GSO who immediately sent out a longer, fully-machined baffle.

I ended up not using this (as the 1ry mirror cover doesn't fit over it), but it makes me really frustrated when manufactureres clearly know there is an issue, but are prepared to lie about it to the retailers [as they did in this case] until they are found out. 

Nevertheless the RC12 is a great scope, and I am very happy with it. 

CS Brian
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Craig avatar
Craig avatar
I think I'm having the same problem with my TPO 10" RC.  I've noticed this quite a bit on subs.  This is a stretched image of a stacked image in the luminance channel.
Brian Boyle avatar
Brian Boyle avatar
Hi Craig,  Yes that's the issue.  You need an extension to the 1ary baffle.  It is shocking that a) this slipped through GSO design and b) now that this is well known, neither GSO or their vendors flags this as a problem.  Contact your vendor and shame them into supplying the corrective extension.  To be fair to GSO, they did just that for me. 

CS Brian
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Craig avatar
Craig avatar
Good to know.  My vendor closed shop.  It was OPT in California.  However, I do know you can buy an extension or even 3D print one.  Thanks for replying!