Takahashi Epsilon 130 Zwo Asi 071 Reflection issue?

[Allinthehead]

I hope someone might be able to give some insight into what is the cause of the suction cup like reflections i seem to get with my combination of gear. Could it be the primary mirror reflecting onto the camera's Ar window?

I use an Ir filter which i removed to test if it was the cause, but the result was the same. I've had this issue since i started using this combination of gear.

Maybe there's a fix in post processing?

Richard.

[Allinthehead]

Anybody have any ideas?

[Laurin Dave]

Maybe a reflection back off the sensor window ...   with dust donuts you can use Dust Donut Calculator to calculate how far from the sensor the dust is, not sure how you work it out for reflections though.. either double or half the distance I'd guess.

nice image

Dave

 

[tooth_dr]

On 10/10/2018 at 20:12, Allinthehead said:

I hope someone might be able to give some insight into what is the cause of the suction cup like reflections i seem to get with my combination of gear. Could it be the primary mirror reflecting onto the camera's Ar window?

I use an Ir filter which i removed to test if it was the cause, but the result was the same. I've had this issue since i started using this combination of gear.

Maybe there's a fix in post processing?

Richard.

Can’t help but really nice image. Does there seem to be reflection issues surrounding the ZWO cameras in general?

[Allinthehead]

36 minutes ago, Laurin Dave said:

Maybe a reflection back off the sensor window

That was my thinking too, however this camera has an Ar window and i've used it with an 80 ed and WO Star 71 and had zero issues with reflections. Must look into dust donut calculator thanks Dave.

8 minutes ago, tooth_dr said:

Can’t help but really nice image. Does there seem to be reflection issues surrounding the ZWO cameras in general?

Thanks Adam, yes the 1600 definitely has an issue around the brightest of stars but the 071 isn't known for such problems. I suppose i should shoot some rgb with the 1600 and see if the problem lies with the sensor.

[Laurin Dave]

Richard

Did you image bright stars stars with your other scopes? Also looking at the dust donut equation I think because your Epsilon 130 is f3.3 the halos will be much larger and therefore more evident than with your slower refractors.  Out of curiosity I looked on the ZWO website Astrophotography gallery 1071 images..  there are halos on bright stars, M45 and around the Horsehead..  so maybe it is the camera.. perhaps have a look on Astrobin or similar to see what others achieve with similar gear,  also if it's like mine your ASI1600 will show diffraction patterns (caused by the micro lenses) around the bright stars of M45  which are far more intrusive and which may mask any halo... it also has AR window....    just checked on ZWO gallery... ASI1600 M45 image has diffraction pattern plus halos...   I think it's just the brightness of the stars..  

Dave

[Allinthehead]

1 hour ago, Laurin Dave said:

Richard

Did you image bright stars stars with your other scopes? Also looking at the dust donut equation I think because your Epsilon 130 is f3.3 the halos will be much larger and therefore more evident than with your slower refractors.  Out of curiosity I looked on the ZWO website Astrophotography gallery 1071 images..  there are halos on bright stars, M45 and around the Horsehead..  so maybe it is the camera.. perhaps have a look on Astrobin or similar to see what others achieve with similar gear,  also if it's like mine your ASI1600 will show diffraction patterns (caused by the micro lenses) around the bright stars of M45  which are far more intrusive and which may mask any halo... it also has AR window....    just checked on ZWO gallery... ASI1600 M45 image has diffraction pattern plus halos...   I think it's just the brightness of the stars..  

Dave

I just had a look at the Zwo website and i can see those reflections especially on the image taken with the reflector. Thanks for this, i struggled to find images that had the same issue as i have. I had been thinking about the full frame Nikon 810 sensor. Maybe time to give it some more thought.

[sharkmelley]

These look like the typical halos caused by a double reflection within a glass filter or glass window.

The distance given by the dust donut calculator will be the extra optical path light travels during this double reflection.  But halving this distance won't give you the actual glass thickness because there's still a scaling required for the refractive index of the glass.

Mark

[Allinthehead]

9 hours ago, sharkmelley said:

These look like the typical halos caused by a double reflection within a glass filter or glass window.

Thanks Mark. I wonder can the Ar window be removed on these cameras.

[ollypenrice]

I'd either live with this (you'll see it in professional images, after all) or try to cure it at source but I do like a processing challenge so I had a go at the star second from the left and got this far with it:

Before

After

I wouldn't go down that road myself but, for the record, I made a copy layer and pulled down the bottom like this:

...then lowered to saturation and erased the halo from the top layer.

Olly

 

 

 

[RichLD]

8 hours ago, ollypenrice said:

I'd either live with this (you'll see it in professional images, after all) or try to cure it at source but I do like a processing challenge so I had a go at the star second from the left and got this far with it:

Before

After

I wouldn't go down that road myself but, for the record, I made a copy layer and pulled down the bottom like this:

...then lowered to saturation and erased the halo from the top layer.

Olly

 

 

 

Now all you've got to do is get rid of the diffraction spikes ??

[Allinthehead]

11 hours ago, ollypenrice said:

erased the halo from the top layer.

Thanks Olly. That definitely looks better. I'll go for the cure long term and this patch in the short term.

[Allinthehead]

2 hours ago, RichLD said:

Now all you've got to do is get rid of the diffraction spikes ??

? If they're good enough for Hubble. They do help mask poorly processed stars tho.