Anyone have any experience with GSO newts and star deformity? I've tried every collimation technique known to man and simply can't get round stars with or without coma corrector! I get stars with spike tails and out of focus stars that look wonky. It's frustrating as on the bench it seems perfectly collimated yet in the field it's NEVER showing round stars. I've tweaked secondary but havnt yet pulled out the primary to tweak that. See pics . Any help appreciated.
I'd say your primary is pinched so loosen the clips and you should be good.
After pulling apart some old GSO's recently I'll second that suggestion, my newish SW had the clamps pretty firm on the mirror as well with no play. The older GSO had the pads deforming it was so tightly wound down.
My collimation with a cheap collimator still needs a tweak on the field for best results. If I was to spend money again on collimation tools, I think I'd get an artificial star generator over a collimator for around the same price.
After pulling apart some old GSO's recently I'll second that suggestion, my newish SW had the clamps pretty firm on the mirror as well with no play. The older GSO had the pads deforming it was so tightly wound down.
My collimation with a cheap collimator still needs a tweak on the field for best results. If I was to spend money again on collimation tools, I think I'd get an artificial star generator over a collimator for around the same price.
I'd say your primary is pinched so loosen the clips and you should be good.
Thanks guys. I took your advice and removed the primary mirror. Was a bit tight especially on one end so I loosened all. What I noticed after using the artificial star as theybseem better collimated. Also seems the collimation tools I sued are much more aligned than before. The real test will be on stars so fingers crossed. Thanks
I’ve only had issues with my 6” GSO newt , all types of weird Star shapes mostly flared stars to one side ( 2 years ago )
My 8” and 10” GSO Newts have been less troublesome
With the 6” I did the following -
Fit new 3mm thick cork pads behind the primary mirror
Loosen the 3 primary mirror retaining clips so they just touch the mirror and can wiggle
Cut out a plastic Milk bottle to the shape of the secondary mirror holder and place behind so collimation screws pit into plastic not alloy
I use an Orion Cheshire and Orion Laser collimator
My newts are f5 and f6
If your Newts are f3 or f4 you definitely need more precise collimating tools
I’ve only had issues with my 6” GSO newt , all types of weird Star shapes mostly flared stars to one side ( 2 years ago )
My 8” and 10” GSO Newts have been less troublesome
With the 6” I did the following -
Fit new 3mm thick cork pads behind the primary mirror
Loosen the 3 primary mirror retaining clips so they just touch the mirror and can wiggle
Cut out a plastic Milk bottle to the shape of the secondary mirror holder and place behind so collimation screws pit into plastic not alloy
I use an Orion Cheshire and Orion Laser collimator
My newts are f5 and f6
If your Newts are f3 or f4 you definitely need more precise collimating tools
Cheers
M.
Thanks Martin. Good tips. Hope I don't have to do all of that but at least I know now the places to tweak
Not good. Took the whole thing apart. Fixed all.as per below. Got it fully collimated. Stars perfect donuts. Then focused. Took 30sec test image. And stars looked like mini comets.
It's either reflections or something else but it's not pinched mirror or collimation or coma.
Star test is good? Planets etc look sharp on visual?
Chuck the camera in and you get mush?
One is your optical path the other a different kettle of fish to do with spacers and a heap of things I've only just learned to speel, yet alone tried...
If its still no good on visual, how is your secondary mirror secured, glued, clamps, or within a cylinder?
Star test is good? Planets etc look sharp on visual?
Chuck the camera in and you get mush?
One is your optical path the other a different kettle of fish to do with spacers and a heap of things I've only just learned to speel, yet alone tried...
If its still no good on visual, how is your secondary mirror secured, glued, clamps, or within a cylinder?
Actually you ate right. Visual is good. Imaged a planet via vid as a test and turned out ok. Just stars are not right. Mirror is secured via rubber cleats but not too tight
Actually you ate right. Visual is good. Imaged a planet via vid as a test and turned out ok. Just stars are not right. Mirror is secured via rubber cleats but not too tight
Hi Paul, I too am often battling with my Newtonian to get round stars. I was looking at your first image. It looks calibrated. How is your illumination on non-calibrated subs? Central? What telescope and coma corrector are you using? What is your back spacing? Do you use an OAG &/or filter wheel? (Both are notorious for introducing tilt with fast optics)
One thing that helped me was to run an aberration inspector through NINA’s plugin Hocus Focus. It will make a back focus recommendation and tell you what tilt corrections to make.
That is astigmatism so something still pinched.....check secondary as well Paul and re check main mirror and loosen clips more.
With the secondary It's well known that silicon can pinch It too and could cause what your seeing.
On my GSO 6" I had to re do the secondary and that fixed the stars but with the GSO 8" the main mirror clips were too tight and once loosened the stars come good.
When using a coma corrector make sure the spacing is spot on....although this isn't the problem I see here.
Hi Paul, I too am often battling with my Newtonian to get round stars. I was looking at your first image. It looks calibrated. How is your illumination on non-calibrated subs? Central? What telescope and coma corrector are you using? What is your back spacing? Do you use an OAG &/or filter wheel? (Both are notorious for introducing tilt with fast optics)
One thing that helped me was to run an aberration inspector through NINA’s plugin Hocus Focus. It will make a back focus recommendation and tell you what tilt corrections to make.
Hi Stephane
Yes these things are important too but you should first sought out this other issue first without any correctors in place and once stars look good.
Then with coma corrector in re collimate with good spacing.
Good point Louie. I missed your post. It might be the secondary mirror as you say. Paul indicated that he loosened the clips holding the primary mirror. How though do you check the secondary mirror for pinched optics due to silicon? And how do you “re do” the secondary?
Good point Louie. I missed your post. It might be the secondary mirror as you say. Paul indicated that he loosened the clips holding the primary mirror. How though do you check the secondary mirror for pinched optics due to silicon? And how do you “re do” the secondary?
If It's silicon on remove It and re do It....plenty of how to on youtube.
Yes Louie's on the money. That is glass pinched. If it's not the clips on your primary then it is the silicone pulling at the back of your secondary. Cut it off with a stanley knife then clean it out. Put 3 dabs at 120 degrees on an ellipse at 75% from the center of the secondary. Put the mirror face down on a flat surface. Get a wooden paddle pop stick as a spacer and rest the aluminium cylinder onto the silicone and let it cure. When it cures it will shrink, pull and jam the wood spacer. Slide it off to release the pressure and you'll be good to go.
PS: make sure to make a note of the secondary offset before re gluing.
