Need advice on refractor issue

[obrads (Alex obradovic)]

hey guys i am new to this hobby and have become aware of some weird refraction i am getting in my images, i have contacted saxon about it and they gave me some advice but i heard people here where very experienced and would like a second opinion below i will list some photos and the whole story, thank you.


so i use a saxon ED100 and have been imaging with it. i use a T48 adaptor to a nikon D3. around bright stars i get a warped halo with refraction at long exposures. i use a focusing mask so it isn't bad focus and my tracking total error is always below 0.60 seconds. i posted on redit forums and Facebook and people suggested a few reasons. 1. over exposure 2. lens is not aligned correctly. 3. not everything in the scope is aligned.
it can't be over exposure because my mate with the same set up can get much more data and over expose and he doesn't get the warping and i did some test with making sure my camera was straight and that wasn't the issue. it only comes up with more exposure and brighter objects (had no issue with eta Carinae) . i messaged saxon and they said it could be the focusing rod not aligned? and i can adjust it myself. what do you think of that? i nervous to adjust the scope incase i make stuff worse and then they won't replace it if there is an issue. don't really know what to do or where to go. i don't know what the issue could be or how to fix it. some advice would be greatly appreciated thank you. i can't upload the files for some reason so here is a link to my facebook album with the photos in a public album: https://www.facebook.com/obrads/medi...5411197&type=3

[Merlin66 (Ken)]

Alex,
Love to help, but for many various reasons I don't do Facebook, so I'm unable to access your images/ video.

[glend (Glen)]

Ditto, i refuse to use Facebook. Suggest you look at the Astrobin free account option.

[obrads (Alex obradovic)]

ok i have uploaded them to astro bin please have a look now thank you https://www.astrobin.com/users/obrads/

[Atmos (Colin)]

Are you using a field flattener?
The stars in the centre are nice and round but the brighter stars out towards the edge are showing some effects. This I think is because of field curvature.

[jenchris (Jennifer)]

Mine doesn't do that.
Same scope

[obrads (Alex obradovic)]

no field flattener but it was because in those photos i was using a t ring that was to small for a full sensor camera, i have no idea what is creating the strange shapes though :\

[Atmos (Colin)]

With no field flattener you are going to get less than perfect star shaped as they move away from the centre of the field.
It could be a combination of field curvature, tilt in the system and even possible interaction with micro lenses on the pixels.

[obrads (Alex obradovic)]

yeah thats alright, the issue i have though is the stars in the middle that are very strange, when you say tilt in the system could that mean something not aligned in my setup?

[JimsShed (Jim)]

As a process of elimination, have you tried imaging with a different camera?
IMHO most of the stars are consistent and don't exhibit any "flaring", which would tend to indicate that overall the optics are aligned. I'm thinking some sort of filmy substance on a lense or the camera's sensor.

[glend (Glen)]

Aside from the obvious vignetting, the star flares look very strange. The Horsehead photo seems to indicate a flare to one side. Have you checked the collimation of this scope? I would start there. And check the focuser collimation too. Make a simple paper target the diametre of your objective and put a dot in the exact centre, Place a laser in the focuser and see where the laser dot falls in relation to your paper centre spot. Adjust your focuser alignment screws so thst the laser sits on the centre spot. Next step is to do a star test to check for objective tilt.

[obrads (Alex obradovic)]

Thanks glen! I'll give that a go, I just don't know what screws hold my focuser :/ would you be able to help with that?

[skysurfer]

Probably it is the same as my ED110.

I pictured the focuser and marked two of the three adjustment screws (the third is behind). They require a hex key of 2mm.
I hope it is the same with your ED100.

[Merlin66 (Ken)]

Hmmmm
Those small screws hold the focuser onto the rear cell (-and allow rotation of the focuser) but will not facilitate re collimation of the focuser.
The rear cell in the OTA would have to be adjustable, which in this case doesn't seem to be possible.

[obrads (Alex obradovic)]

Hmmm dam :/ mine is a bit different, I'll do some testing tonight to see if I can fix it , if not should I ask Saxon to replace it?

[glend (Glen)]

Sorry, not all focusers can be adjusted, or aimed, if that is the case with yours then your stuck with maybe adjusting the objective. Does the objective cell have adjustment screws?

[obrads (Alex obradovic)]

Nah the objective doesn't have screws, do you think that is the issue though? Something not aligned?

[glend (Glen)]

Originally Posted by obrads

Nah the objective doesn't have screws, do you think that is the issue though? Something not aligned?

How does it look with an eyepiece? If there is no adjustment capability, then there is not much you could do if it is misaligned. I would still use the laser to check the focuser alignment and do a star test both with a camera and visually. If it is ok with an EP it could be distorting under the weight of the camera. A "tilt adjuster" ring might help but you need to know for sure what is causing it.

[obrads (Alex obradovic)]

through the eye piece it looks fine and i have imaged the moon with no issues. the camera i use is very heavy so i will try tonight with a lighter camera see how it goes. i never considered the camera could creat the issue so thank you for your help! if it is the camera being to heavy is there anything i can do about that?