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Old 07-10-2015, 01:17 PM
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Flugel88 (Michael)
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Artifact banquet first light GSO RC14

Had a crack at the Skull last night with my new setup GSO RC truss.
As you can see i have a multitude of issues to contend with.


Scope GSO RC TRuss 14"
Atik 383L
Orion OAG
Moonlite 2.5" focuser
Nautilus Filter wheel
1.25" astronomik filters


Green arrow
Firstly vignetting my 1.25" filters i'm fairly certain ill be needing to upgrade my filters and filter wheel to at least 36mm.Is a shame that Nautilus Filter wheel carousals are not interchangeable

RED
Been having major issues with moisture in my Atik Camera. I Used to be able to avoid the jack Frost crystals from forming on the CCd chip by dropping temp staged over 30 mins but now its so bad nothing seems to stop it.
So far i've tried baking the Desiccant tablets multiple times also placing camera in a sealed bag full of desiccant satchels.
I can now see what looks like either permanent water sitting to the side of the Sensor or could be some kind of residue marks .
I am certain that the red arrow is a moisture issue as it shows when i take an exposure with camera not connected to scope.

Blue
Are these dust related?
I did a test taking a flat just using camera to focuser (ie no filters or OAG)
and they were still visible. Also checked camera glass window looks spotless. Would flats eliminate these circles?

ORANGE
These odd internal light reflections are what worry me most.They look terrible.checked the all my imaging components but i couldn't see any obvious shinny or unpainted surfaces. Could this be an issue with the RC's internal Baffle flocking?

Hoping to get a chance soon to play around do some proper fault finding.
appreciate any and all help you could all offer me as you can see im going to need it


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  #2  
Old 07-10-2015, 04:29 PM
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Firstly the actual image of the Skull looks very good and you are almost resolving that double star at the centre.

The donuts are from dust on your filters. So try cleaning your filters with a photographic lens cleaning cloth and a hurricane blower. Also clean your CCD window if the same dust donuts appear with any filter showing its on the window.

The vignetting will flat field out.

The frost and water damage is more the concern. It could be a fatal error and time to look at a new camera and one that does not do that. Starlight Express, FLI, Apogee cameras all have argon in the ccd chamber and do not need desiccant nor frost over. Perhaps consider one of those. QHY are popular and inexpensive so perhaps check out if they are reliable. QSI does not have this problem either as far as I know.

Greg.
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Old 07-10-2015, 09:24 PM
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Peter Ward
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You could try a SBIG CCD

Shameless promotion aside....I'm staggered you are seeing such serious vignetting with a KAF8300 chip.

This should not be the case with a 14" RC.

I'd suggest you'll need at least 36mm or larger apertures throughout the entire imaging system to keep it at bay (1.25" filters, unless very close to the focal plane, won't cut it)

Reflections also look troublesome....they will not flat-field out.

Flocking and perhaps a shroud around the truss may help keep the weird light arcs subdued.

Last edited by Peter Ward; 07-10-2015 at 09:57 PM.
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Old 07-10-2015, 09:37 PM
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The reflections most likely will require baffles. I would baffle the primary about 10mm around the inside edge where it meets the baffle tube. Cut it out of some black cardboard and see what that does.

Next possibility is the outside edge of the secondary mirror.

Greg.
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Old 08-10-2015, 08:50 AM
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Flugel88 (Michael)
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Thanks for the input guys.
I really do hope i can come up with a way of removing moisture from my ccd chamber i might send a message to ATik Support see what they think.
The whole desiccant idea is a bit archaic! An argon filled chamber does sound more trouble free but i would have to save allot of penny's to be able to afford an Sbig.
Specially now the Aussie $ has gone down the toilet.

I won't be able to get away with my 1.25" filters though had a feeling it would be a major problem back when i decided to buy the RC.

I ordered a light shroud yesterday hoping that might help. When i packed up the scope i noticed some dew starting to form on the secondary shroud could help prevent that too with any luck.

If that doesn't help ill give Greg's idea ago and try some baffles.
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Old 08-10-2015, 09:28 AM
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The light shroud is unlikely to do anything. That's not light coming from outside the scope but rather reflections around the optics from a bight star outside the FOV.

I have seen them on my CDK and been through the evolution process where Planewave bit by bit sorted them out.

What they did was:

1. Redesigned the secondary shroud so the section that extends out from the mirror was 4-5mm thick where it met the mirror and tapered out to 1mm thick at the end. This effectively covered the first 4-5mm of the secondary mirror and prevented some of this arc shaped reflections (hence the round shape of the reflections).

2. Provided several cut baffles, one around the primary where it meets the internal shroud, one on either side of the corrector lens. These were basically like a stiff cardboard disc about 15mm wide to stop bright edges of the corrector lens or edges of the lenses from causing reflections.

3. I flocked the trusses but it did nothing. I flocked the inside of the secondary shroud and the walls of the main tube and that seemed to improve contrast a bit. But it was 1 and 2 above that handled the reflection arcs not anything else.

A turned down mirror edge is also a common error on RC optics
See a fair way down the page here:
http://www.bbastrodesigns.com/JoyOfM...Polishing.html


The main mirror at the very edge really needs to be covered by a baffle. A 4 or 5mm wide black cardboard to cover that last 5mm of the mirror which may have a poor edge and also cause problems. My Planewave has a metal ring that covers the last few mm of the outer edge of the primary mirror. This would be important to check you have one and if not that should be done as well.

Greg.
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Old 08-10-2015, 09:57 AM
glend (Glen)
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A black permanent marker pen can resolve almost any mirror edge issues. All the mirrors that I have had, especially with edge turn down, can produce light scatter, and blackening the edge is a simple fix. A turned down edge is easier to blacken but it can also be done on a straight edge. You need a steady hand, but it can be done pretty quickly (a turn table, lazy susan bearing, etc makes the mirror rotation easy). Any 'intrusion' onto the mirror surface can easily be cleaned up with acetone on a cotton bud at the time.
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Old 08-10-2015, 10:11 AM
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I'm not entirely convinced the darkened corners are actually caused by vignetting. I use 1.25" filters in a qsi with the same chip at f4.5 and it is nowhere near as serious as that, and at f7 I would have thought you'd be fine. The fact that there actually seems to be a very large "light donut" superimposed on your image means that once you've eliminated the stray light issues the vignetting might not be so bad. Definitely worth trying before giving up on your existing setup.
Cheers,
Andrew.

Quote:
Originally Posted by Flugel88 View Post
Thanks for the input guys.
I really do hope i can come up with a way of removing moisture from my ccd chamber i might send a message to ATik Support see what they think.
The whole desiccant idea is a bit archaic! An argon filled chamber does sound more trouble free but i would have to save allot of penny's to be able to afford an Sbig.
Specially now the Aussie $ has gone down the toilet.

I won't be able to get away with my 1.25" filters though had a feeling it would be a major problem back when i decided to buy the RC.

I ordered a light shroud yesterday hoping that might help. When i packed up the scope i noticed some dew starting to form on the secondary shroud could help prevent that too with any luck.

If that doesn't help ill give Greg's idea ago and try some baffles.
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Old 08-10-2015, 11:36 AM
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Very interesting to see these results regardless of how good or bad they are. There's been a noticeable absence of any real life results from GSO 16" RC's since their supposed release.

Thanks for sharing and I hope you iron out the problems without too much drama
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Old 08-10-2015, 12:59 PM
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lazjen (Chris)
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It might be worthwhile removing the filter wheel / filters and seeing what results you get. At least you can see if any of the problems disappear.
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Old 08-10-2015, 01:12 PM
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Those reflections are an oddity to me. I know that all the baffle tubes underwent a redesign some time ago and this should not be happening now. I wonder if there is some reflection coming off the focusor. It is a bit narrow for that light cone. I would have thought a 3" focusor would have been more appropriate. I guess putting the figures into a ray trace will tell you what is going on.

I think your filters are causing the vignetting. All the adapters that come with the scope are over 100mm. Maybe the 2.7" focusor might be causing some vignetting too. Again ray trace diagrams will help.

Quote:
Originally Posted by rogerg View Post
Very interesting to see these results regardless of how good or bad they are. There's been a noticeable absence of any real life results from GSO 16" RC's since their supposed release.

Thanks for sharing and I hope you iron out the problems without too much drama
Hey Roger, they won't give me one for free so that is why there had not been many images coming from them.

Seriously though I don't know why there have not been many images. There has been the odd one or two getting around on CN but not like there is a lot out there. I doubt there is any real problem with them.
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Old 08-10-2015, 01:20 PM
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I agree with Paul. A 2.7 inch focuser seems inadequate and certainly will not work with full frame or larger sensors.

Often its best on any RC to ditch the focuser and get a fixed length adapter made up by Precise Parts and install an electronic focuser of some sort or maybe a Moonlite or Feathertouch focuser (3.5 inch models).

The AP focuser on my Honders is a work of art but focus is way too critical to easily achieve manually so I have a fixed length adapter and a FLI Atlas focuser (expensive though). But you wouldn't have to go to that expense to get a good result.

I thought step 1 with GSO RCs was to bin the focuser.

Greg.
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Old 08-10-2015, 01:31 PM
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Quote:
Originally Posted by gregbradley View Post
.......I thought step 1 with GSO RCs was to bin the focuser.

Greg.
Yep agreed. I think those are junk personally and have told Jim that several times.
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Old 08-10-2015, 07:00 PM
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Flugel88 (Michael)
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I've had a good look at the scope today and taken some pix for reference.
I'm still a novice at all this so some suggestions are a bit technical for my level of current understanding.

Some things i have noticed!

Some of you suggest that the rough sides to my mirror could be a problem. Had a good look at that and i can see an edge about 5mm of rough glass that runs around the primary.

There is a black ring that runs around the Central baffle outer edge that sits on the primary.
Same sorta ring sits inside the secondary where the baffle meets the glass.(picture included)

I also noticed my Moonlite focuser has a rather bright stainless hex head bolt that sits inside the focuser.
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Old 08-10-2015, 07:22 PM
glend (Glen)
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Michael the black ring the runs around the centre of the primary is the collar that the baffle tube screws onto, on mine there is a thin rubber gasket that sits between the centre edge of the mirror and the collar, I think all the GSOs are the same in that regard. The bright bevelled primary edge, which is done to prevent edge chipping into the mirror surface, I would blacken with a marker pen but you will need to remove the primary to do that, not everyone is confident with doing that.

Last edited by glend; 08-10-2015 at 07:34 PM.
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Old 09-10-2015, 08:06 AM
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What I did to an RCOS I had was make a circular donut that covered the last 10mm of the mirror. This is pretty normal in high end RCs. My CDK has a black metal ring that covers the last 5mm of the mirror.

Greg.
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Old 31-10-2015, 10:34 PM
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Thought i would update my progress in dealing with my setup issues with the GSO 14 Truss.

Thanks to the help from everyone here and particularly some tips from Thava I think that i have managed to eliminate those horrid internal light reflection.

I have also fixed the issue's i was having with my Atik 383 freezing up after getting some help from ATik Support.

So basically all i have done is extend the central baffle tube using some black foam tape from clark rubber and flocked my Moonlight focuser.
I made up a little jig cut to mirror the size of my 8300 Chip so i could work out how much to extend the length of the baffle until there was no stray light.I still need to do some testing to see what works better extending the baffle or using thicker foam tape.
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I still have some problems with Vignetting that i need to figure out.

A test shot of ic 5148 with 6x LUM subs stacked with CCD stack with Darks/flats/bias.
Weather has been a real drag lately hope to get some real data soon
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Old 01-11-2015, 11:04 AM
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Good to hear that you are making progress, Michael.
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