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Old 12-09-2020, 06:44 PM
DaBris (Daniel)
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Star glow/aura/spikes

Hi,
Just looking for some feedback as to why the bright stars in my images are showing extreme shine/spikes etc.
I have recently changed from DSLR AP to purchasing an ASI183MC Pro, I am seeing a lot of my bright stars wit this extra shine or glow/rays. I thought it was focus, but I have spent a long tine in ASI air working to the lowest fwhm in focus mode could it be back focus? I have set it at the recommended distance. Is there something wrong with my optics
I have attached a single 100gain 180sec exposure for reference. Would appreciate help on this
Cheers
Daniel
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Last edited by DaBris; 12-09-2020 at 09:28 PM.
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Old 13-09-2020, 05:37 AM
DaBris (Daniel)
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I also forgot to say that I have a 1.25Ē ZWO IR/cut filter screwed inside in between the camera and reducer, perhaps it is this filter that could be causing this? I will remove this to compare difference
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Old 13-09-2020, 06:16 AM
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PKay (Peter)
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Hi Daniel

It always takes time (for all of us) to sort things out.

Your image is too small to be of much help.
Try downloading it to IIS at about 1Mbyte.
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Old 13-09-2020, 06:50 AM
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xelasnave
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Hi Daniel, may I suggest to cut out five small sections from your images selecting each corner and a square from the middle small enough such that each image will upload without downsizing, ... looking at the stars in each region should be sufficient to see the problem I hope.
Alex
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Old 13-09-2020, 12:22 PM
DaBris (Daniel)
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I think this one is a little bigger, having trouble uploading it keeps reducing size down quite a lot.
From what you can see in this shot, the 2 larger stars have the problem I am talking about.
I may ditch the IR/Cut filter to compare the differences.
Thanks again
Daniel
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Old 13-09-2020, 01:20 PM
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PKay (Peter)
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Daniel

More questions :-)

What mount are you using, and what is it sitting on (timber deck, concrete)?
Are you auto guiding?

What type of scope?
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Old 13-09-2020, 01:36 PM
RyanJones
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Hi Daniel,

I’m going to try and make a diagnosis without all of the information. Essentially it seems like essentially what is going on is that the lensing isn’t corrected evenly . This is exacerbated by the I/R cut filter calming the red end of the spectrum but not the U/V ( blue ) end. This is giving you the halo all in blue end. I guess it’s all a matter of taste and I agree your glow is probably slightly too large, but some glow around your stars can give your image a dynamic feel and add depth. It appears that you’re imaging though a refractor from the look of the image which I must admit is not my area so I could be taking from my rear end....

Cheers

Ryan
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Old 13-09-2020, 04:22 PM
glend (Glen)
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Quote:
Originally Posted by DaBris View Post
I think this one is a little bigger, having trouble uploading it keeps reducing size down quite a lot.
From what you can see in this shot, the 2 larger stars have the problem I am talking about.
I may ditch the IR/Cut filter to compare the differences.
Thanks again
Daniel
Daniel, what type of scope was used? Blue star bloat is very common in refractors with poor colour correction. It does not look like an image taken through a mirror system scope, like a Newtonian, where you get true colour rendition. Can you identify the scope?
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Old 13-09-2020, 05:28 PM
raymo
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If it is of any help to anybody, if you put your screen to 3 or 4 hundred %
you can see that the two bright stars have within their halos a definite pattern
somewhat like a weird Bahtinov mask.
raymo
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Old 13-09-2020, 06:13 PM
DaBris (Daniel)
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Pkay and glend,

My scope is a 72ed, Mount heq5pro, main imaging cam asi183mc pro cooled and a .85x skywatcher reducer/flattener.
Sitting on concrete footings, auto guided with ASIAIR.
Only filter I use is the ir/cut filter.

Ryan, thanks, yes this is why I will remove the or/cut filter first chance and report back.

Thanks you all for your time helping me sort this one out
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Old 13-09-2020, 07:29 PM
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Quote:
Originally Posted by DaBris View Post

Ryan, thanks, yes this is why I will remove the or/cut filter first chance and report back.
Itís likely that by removing the I/R filter you wonít get rid of the issue. You probably need to change the filter to an I/R U/V cut filter to take care of both ends of the spectrum. The reason you didnít have this issue with your DSLR is because it has a UV IR cut filter built into it.

I hope this clarifies things

Cheers
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Old 13-09-2020, 08:27 PM
DaBris (Daniel)
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Hi Ryan,
Thanks again here is an image of Antares showing exactly what I am experiencing. You are right, I removed the air/ cut filter and nothing changed, however, z was stated does not have much in the blue and I am still getting the large spiral spikes
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Old 13-09-2020, 10:13 PM
RyanJones
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So I think the Iris looking spikes are a different issue all together. Normally the shape of defraction lines are a product of the shape of image train or the shutter on the camera. Youíll often notice a TV camera looking at a bright light will produce a hexagonal pattern, newtonian 4 vane secondary spiders produce a cross and even your eye lashes if you squint looking at a light will produce their own unique multi spike pattern. It is possible that the iris pattern in the halo is actually quite normal for your particular camera but it normally wouldnít be evident because the halo would be so significantly smaller. If it were me, I think my process of diagnosis would be to deal with the size of the halo first by way of UV and IR filtering and then reassess the pattern within and see if it still is significant enough to worry about.

Ryan
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Old 13-09-2020, 10:24 PM
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mswhin63 (Malcolm)
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I have exactly the same things as well, Mine is DSLR on an 80mm TS APO Triplet. Not really that annoying until your post picked out. It would be curious if it can be processed out.

I have an HEQ5 Pro as well. It is not the mount
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Old 14-09-2020, 05:14 AM
DaBris (Daniel)
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The Iris lines are exactly what I am talking about, and effectively that is what these stars all look like to me now, eyeballs.
As it turns out Ryan my filter is a UV/IR cut filter made by ZWO specifically for these cameras without an AR protect window. So in theory I should have the correct filter in place. Not sure how to process the iris lines out, guess I will be getting used to having eyes looking back at me through my images for a while until I figure it out.
Cheers
Daniel
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Old 14-09-2020, 06:09 AM
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Hi Daniel

Just for a reference, see attached my image taken of Antares.
I think it is perfectly normal!
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Old 14-09-2020, 06:14 AM
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Certainly does sound like you have the right filter in place Daniel. My next question would be is there any chance that you have a light layer of dew building up on the filter ? I had this happen on my filter on my DSLR. I would have thought in therory that in a refractor system, that should be mostly sealed off but I guess if there is moisture in the focuser when you put the camera in it is in theory possible. This would cause a defraction of the light causing the bloat. Can you maybe compare an early sub and see if the ď iris ď is there ? If that isnít happening, Iím really not sure but youíve posted an interesting problem and Iíll be watching keenly to see what the outcome is.

Ryan
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Old 14-09-2020, 06:58 AM
DaBris (Daniel)
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Thanks, Peter, I see that your stacked image of Antares is very similar to what I am seeing in mine. I think I will need to improve my processing skills until I am happy with it, which will probably be never haha!

Ryan, I wasn't getting these squiggly iris lines with my Canon 60d attached to the same refractor, and last night I removed the filter and took a few snaps and still had the same result. With the filter now ruled out, it leaves the combination of 72ED optics, ASI183MC-Pro, and 0.85x reducer. Therefore my next experiment will be trying different back-focus spacing between the camera and reducer, it may be just out either side of the optimal distance.
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