Weird star shapes

[souls33k3r]

I think i should cry out for help now.

I shot the IC1848 image a few weeks ago but did not notice the corner stars misbehaving as much but a friend of mine who has been helping me with figuring out totally separate issue noticed the corner stars on NGC7000 

Both IC1848 and NGC7000 are single image but the center and corners are elaborated to show the issue.

What could be causing the stars in such weird shape on my NGC7000 image?

IC1848

NGC7000

 

Many thanks in advance

[souls33k3r]

Just to add, it's a WO Star 71 scope which i bought off FLO and this was checked and tuned by ES Reid.

[RayD]

Was this using autofocus mate?  If so it may not have worked quite right as this looks like it is a little out of focus to me.  My Star71 was particularly susceptible to shapes like this if focus wasn't spot on.

[Hallingskies]

It’s kind of hard to tell from the images.  The first looks a lot better than the second certainly, and in the second one, the worst of the distortion appears to me to occur in the bottom third of the image?  It look like a slight dose of imaging plane tilt to me.  You could try rotating the camera and/or focusser to see if the distortion follows the rotation.  I very much doubt it’s the scope optics unless you’ve whacked it.

Is there a bolt-on field-flattener in the mix?  Sometimes the spacing between the back end of the ff and your imaging plane is critical to avoid eggy stars at the image edges, so I believe.  

I think if I got stars as round as you have on single subs, though, I’d be happy.  Depends how multiple subs stack out, I suppose.

[RayD]

17 minutes ago, Hallingskies said:

Is there a bolt-on field-flattened in the mix?  Sometimes the spacing between the back end of the ff and your imaging plane is critical to avoid eggy stars at the image edges, so I believe.  

It's a star71 which has the FF built in, ala Petzval design, so when you are in focus the FF back focus distance is set.  This is why it can affect star shapes like this if you are out of focus.

[souls33k3r]

Ah, i'm glad i asked this question and was hoping that someone with the similar scope would've noticed it if it was an issue so i'm glad you chipped in with your experience @RayD mate.

The stars in the middle look fine, it's just the corners. What should i be doing/checking to make sure this does not happen because every time when i've run the AF routine, if my HFR value isn't below 1.0, i will run it again to bring it close to 0.8HFR which is the best i've seen so far and then let my sequence run.

Oh and i would like to thank @angryowl who noticed this issue (i was too tired and sleepy to realize this).

 

[RayD]

17 minutes ago, souls33k3r said:

Ah, i'm glad i asked this question and was hoping that someone with the similar scope would've noticed it if it was an issue so i'm glad you chipped in with your experience @RayD mate.

The stars in the middle look fine, it's just the corners. What should i be doing/checking to make sure this does not happen because every time when i've run the AF routine, if my HFR value isn't below 1.0, i will run it again to bring it close to 0.8HFR which is the best i've seen so far and then let my sequence run.

Oh and i would like to thank @angryowl who noticed this issue (i was too tired and sleepy to realize this).

 

I wouldn't worry too much about the actual number as seeing can have an effect on this, meaning you could be chasing a value that isn't possible on that particular occasion.  I tend to do a 400% preview in a corner to see if I am where I expect to be, and if it looks like it could be better, I will run AF again.  

I found my Star71 very critical with respects to needing good focus.  Try running AF a couple of times as you may not have the settings quite right, with some tickling of the step size needed perhaps.

The more you use it the more you'll get used to it and understand what effect small adjustments have.

At this point I wouldn't worry about the star anomaly until you know you have absolutely nailed the focus point.

[LukeSkywatcher]

Just looks out of focus to my non-imaging eyes.

[souls33k3r]

11 minutes ago, RayD said:

I wouldn't worry too much about the actual number as seeing can have an effect on this, meaning you could be chasing a value that isn't possible on that particular occasion.  I tend to do a 400% preview in a corner to see if I am where I expect to be, and if it looks like it could be better, I will run AF again.  

I found my Star71 very critical with respects to needing good focus.  Try running AF a couple of times as you may not have the settings quite right, with some tickling of the step size needed perhaps.

The more you use it the more you'll get used to it and understand what effect small adjustments have.

At this point I wouldn't worry about the star anomaly until you know you have absolutely nailed the focus point.

The step size perhaps needs a little tickle ... Do you think increments would be better or decrements? In any case, by what number? +/-5? I suppose i should go back and re-check my steps size once again.

I agree mate, i guess i'm asking all these questions because i'm wanting to learn more about the system.

You're right, i shouldn't worry too much knowing now that you've seen the same star anomaly with your Star 71 too which was related to focusing. 

Can't thank you enough mate. Really really do appreciate your input

3 minutes ago, LukeSkywatcher said:

Just looks out of focus to my non-imaging eyes.

Cheers mate, yeah that's what Ray has been saying as well. I really should look at my AF once again

[RayD]

8 minutes ago, souls33k3r said:

The step size perhaps needs a little tickle ... Do you think increments would be better or decrements? In any case, by what number? +/-5? I suppose i should go back and re-check my steps size once again.

I agree mate, i guess i'm asking all these questions because i'm wanting to learn more about the system.

You're right, i shouldn't worry too much knowing now that you've seen the same star anomaly with your Star 71 too which was related to focusing. 

Can't thank you enough mate. Really really do appreciate your input

No problem at all.  It's worth spending a little time before astro dark just fine tuning.  Personally, seeing your out of focus value, I would say you can afford to increase the step size.  Try +10 to see where it takes you, knowing that you are looking at a point of around 4 times the in focus value.

You'll get there for sure.

[souls33k3r]

Just now, RayD said:

No problem at all.  It's worth spending a little time before astro dark just fine tuning.  Personally, seeing your out of focus value, I would say you can afford to increase the step size.  Try 10 to see where it takes you, knowing that you are looking at a point of around 4 times the in focus value.

You'll get there for sure.

Will do sir. 

I think i've eaten everyone's brain enough for today so i'll shut up, go away, make these changes, test and come back with hopefully good results and news

Once again, can not thank you enough mate.

[RayD]

Had my brain picked a few times, but never had it eaten......very Hannibal Lecter ?

[souls33k3r]

17 minutes ago, RayD said:

Had my brain picked a few times, but never had it eaten......very Hannibal Lecter ?

I wouldn't have thought anyone was able to clock on to that reference that quickly ? I'm impressed mate ? 

[souls33k3r]

@RayD many thanks for your brain, it was delicious and am happy to report that it was indeed the focusing that was causing it. 

Last night while i was out, this issue became so much more prominent within 5 frames. The top half of the image was in focus where as the bottom half was not. 

Can't thank you enough mate

[souls33k3r]

OK that was a lie. My friend kindly helped me look at the focused image (i stopped half way through my imaging run last night to check the step sizes) and this weirdness still shows  Could it be collimation? I take extra care of my kit and for sure never dropped or banged it.

 

[souls33k3r]

Going through my images from last year (when i first received it) and can see the same artefacts on the data   I seriously wouldn't have noticed it if my friend hadn't pointed it out to me. 

Maybe i didn't spot this on individual subs because i hardly pay attention to anything other than the object that i'm imaging and clearly did not spot it when stacked.

I just hope it's not a big issue and can be easily fixed. Getting worried and paranoid.

@FLO can you help?

[souls33k3r]

A bit more update on the situation. 

Like i mentioned above, i went back to my images from last year when i first got the scope and found the similar (yet small) anomaly in the stars. Thought that my mind might be playing tricks on me so got a friend to verify this and he too found the same. 

Eventually emailed FLO and their great support suggested me a few things which i had already tried. FLO have agreed to pick the scope up and send it off to ES Reid to have it checked. 

Scope will be picked up on Monday.

FLO have done it again and gone well beyond any customer satisfaction experience. Can not thank them enough

[RayD]

1 minute ago, souls33k3r said:

A bit more update on the situation. 

Like i mentioned above, i went back to my images from last year when i first got the scope and found the similar (yet small) anomaly in the stars. Thought that my mind might be playing tricks on me so got a friend to verify this and he too found the same. 

Eventually emailed FLO and their great support suggested me a few things which i had already tried. FLO have agreed to pick the scope up and send it off to ES Reid to have it checked. 

Scope will be picked up on Monday.

FLO have done it again and gone well beyond any customer satisfaction experience. Can not thank them enough

Great news matey.  Reaping the benefit of buying kit from an extremely reputable retailer.  Hope you get it sorted.

[souls33k3r]

Just now, RayD said:

Great news matey.  Reaping the benefit of buying kit from an extremely reputable retailer.  Hope you get it sorted.

Cheers mate. Absolutely. Can not fault their dealings with customers. I mean stuff like this wants you to go back to them over and over again and i have and will continue to do so

[RayD]

12 minutes ago, souls33k3r said:

Cheers mate. Absolutely. Can not fault their dealings with customers. I mean stuff like this wants you to go back to them over and over again and i have and will continue to do so

Likewise.  And the fact that they are sending it to Es is again a testimony to them taking it seriously.

You'll be staring at pinpoint stars before you know it 

[souls33k3r]

8 hours ago, RayD said:

Likewise.  And the fact that they are sending it to Es is again a testimony to them taking it seriously.

You'll be staring at pinpoint stars before you know it 

Can not agree more mate.

The thing is that i have MaximDL installed on my acquisition laptop which i used to use before taking the plunge in to the awesome world of SGP and by default all my subs open up in MaximDL if i were to inspect them but never bothered looking at them in SGP while the subs were coming in. Scary that the scope had this issue which went un-noticed through my untrained eyes for so long. I guess i have to be a little more a.n.a.l about my star shapes from now on. 

Like you said, i can not wait for pinpoint stars (My missus said, your images are fine but what does she know anything about how particular we lot are about our star shapes ?)

[Davey-T]

Hope you get sorted mate, any idea how long it will take ? you're welcome to borrow one of my Star 71s in the meantime as long as you don't find eggy stars in the corners 

I never look too hard myself.

Dave

[souls33k3r]

2 hours ago, Davey-T said:

Hope you get sorted mate, any idea how long it will take ? you're welcome to borrow one of my Star 71s in the meantime as long as you don't find eggy stars in the corners 

I never look too hard myself.

Dave

Cheers mate, so do I.

You're too kind mate. It actually gives me a chance to start using my EdgeHD for a change. My wife has been on the case for me to sell the EdgeHD because I've been using this little guy far too much

[peter shah]

As suggested it might be a collimation issue. But to me its looks like you have tilt in the imaging train. Could be a caused by a couple of things.  

Its also worth checking if the stars in the lower frame come into focus while the upper frame goes out of focus...this will confirm the issue.

Possible causes:

1. Your sensor isn't flat enough to cope with the F ratio,  (quite common and often overlooked and it will be more evident on faster scopes)

2. The focuser is flexing either under  load and needs tightening up or the camera kit is too heavy for the focuser.

3. I've even seen this caused by a filter not sitting flat in the filter wheel, but normally you would see eggy stars across the whole field. 

 

There are more manufactures putting in tilt adjustments on their cameras now

Hope you get it sorted soon

cheers

Peter

[souls33k3r]

21 hours ago, peter shah said:

As suggested it might be a collimation issue. But to me its looks like you have tilt in the imaging train. Could be a caused by a couple of things.  

Its also worth checking if the stars in the lower frame come into focus while the upper frame goes out of focus...this will confirm the issue.

Possible causes:

1. Your sensor isn't flat enough to cope with the F ratio,  (quite common and often overlooked and it will be more evident on faster scopes)

2. The focuser is flexing either under  load and needs tightening up or the camera kit is too heavy for the focuser.

3. I've even seen this caused by a filter not sitting flat in the filter wheel, but normally you would see eggy stars across the whole field. 

 

There are more manufactures putting in tilt adjustments on their cameras now

Hope you get it sorted soon

cheers

Peter

Salam Peter, hope you're well. Thank you for your insight on the subject. Too late to check any of the above as the scope has just been picked up by DPD.

Will be able to report what FLO/ES Reid have to say about this.