Cause of this star flare artifacts. Alnitak's fault?? - Forums

Topic starter

Jan 10, 2024

Hello, everyone. (I hope I am in the right topic)
Yesterday, after two months of only clouds, I managed for the first time to do an hour's integration on flame nebula and horse-head nebula before the clouds returned (again).

This is the stack of 21 x 3' poses calibrated only with master bias and master flat to make it fast. Slightly post produced (badly) to see the data a little.

As you can see above alnitak there are two circular flares.

The very same type of artefact is present on all lights.

I also realised that I had a tilting problem in this session.

What could have generated this artefact? Alnitak? The tilting? Both? Anything else?

My current optical train consists of
- SW Evostar 72ED (APO)
- OVL Field Flattener
- Optolong UHC filter
- Canon 2000d astromodified.

The shots were taken at:
- 180 sec
- 1600 iso (too many)

Thank you very much!!

CS!

FT

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Robert Žibreg

Jan 10, 2024

It's most definitely caused by Alnitak. Bright stars will do that

FilippoTib

Topic starter

Jan 10, 2024

Robert Žibreg:
It's most definitely caused by Alnitak. Bright stars will do that

thank you for your reply. Do you know if there is anything I can do at the acquisition stage or should I just work in post? Thanks again!

Robert Žibreg

Jan 10, 2024 · Edited: Jan 10, 2024

How does your imaging train looks like? I'm not sure if there is anything other then post-processing. I even found the similar question on cloudy nights

Paul Macklin

Jan 10, 2024 · Edited: Jan 10, 2024

Likely introduced by the filter-image train-target combo.

I ran into that a lot with some combos with my older Optolong filters (which tend to halo a lot anyway). I once even had a green blob show up from an L-Pro interacting with the Pleiades, but only when combined with a specific flattener. Took a bit to decide it wasn't something more interesting (and real) like a comet.

Have you considered trying without the light pollution filter? You might be pleasantly surprised with how well it goes after you're done with your processing.

The data and processing are otherwise very promising!!

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FilippoTib

Topic starter

Jan 10, 2024

Robert Žibreg:
How does your imaging train looks like? I'm not sure if there is anything other then post-processing. I even found the similar question on cloudy nights

Thanks for the reply and the reference!

Paul Macklin:
I ran into that a lot with some combos with my older Optolong filters (which tend to halo a lot anyway)

Thank you very much for your reply.
The idea was to upgrade to an l-enhance and from what I understand, by tightening the bandwidth, the problem should become more pronounced, or should it?

Paul Macklin:
Have you considered trying without the light pollution filter? You might be pleasantly surprised with how well it goes after you're done with your processing.

I live in an area with relatively little light pollution but I have neighbours with a lamp pointed in the direction of my setup. In addition, right above my head, there is an orange street lamp.

Without a filter I saturate the histogram already at 30/40 seconds.

In any case, this is the first time I have shot with this filter in combination with the OVL field flattener...

I have to try to move to an area without light pollution and try the flattener without filter.

Thank you again.

CS!

F.T.

Paul Macklin

Jan 10, 2024

Understood! A couple things to possibly consider:

1) The closer you can get the filter to the sensor, the better it ought to go. Can you find a way to get it between the flattener and the sensor? Right now, it looks like it's substantially in front of the flattener. I think that's very consistent with all the internal reflections you are seeing.

2) Can you try putting up some screens to block neighbor light?

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FilippoTib

Topic starter

Jan 10, 2024

Paul Macklin:
) The closer you can get the filter to the sensor, the better it ought to go. Can you find a way to get it between the flattener and the sensor? Right now, it looks like it's substantially in front of the flattener. I think that's very consistent with all the internal reflections you are seeing.

I think I can bring the filter closer to the sensor by using a rotator that holds the filter instead of the nose connection. (And it is one of the next upgrades I would like to make)

However, I don't think I can fit it between the camera and the leveler so as not to change the backfocus (at most I would have to buy the clip version)

Paul Macklin:
2) Can you try putting up some screens to block neighbor light?

Yes the neighbour's light is already partially shielded and does not create any problems except for a very slight gradient.

The real problem is the street lamp which really makes a mess....
Not even being 20 metres away I am forced to shoot mainly subjects to the north or that are high enough not to be affected by the orange light...

Thank you again!

CS!

F.T.

Paul Macklin

Jan 10, 2024 · Edited: Jan 10, 2024

Paul Macklin:
) The closer you can get the filter to the sensor, the better it ought to go. Can you find a way to get it between the flattener and the sensor? Right now, it looks like it's substantially in front of the flattener. I think that's very consistent with all the internal reflections you are seeing.

I think I can bring the filter closer to the sensor by using a rotator that holds the filter instead of the nose connection. (And it is one of the next upgrades I would like to make)

However, I don't think I can fit it between the camera and the leveler so as not to change the backfocus (at most I would have to buy the clip version)
Paul Macklin:
2) Can you try putting up some screens to block neighbor light?

Yes the neighbour's light is already partially shielded and does not create any problems except for a very slight gradient.

The real problem is the street lamp which really makes a mess....
Not even being 20 metres away I am forced to shoot mainly subjects to the north or that are high enough not to be affected by the orange light...

Thank you again!

CS!

F.T.

You bet, and good luck!

Hmm, FWIW, I try to place my filter drawer right after my reducer (or flattener) and OAG. It can be part of your total distance. If you get a shorter T-ring, you might be able to work it out that way, too.

*edit* Now I think I see the separate T-ring in teh photo. Sorry, it's a little dark. What is that big adapter between the T-ring and your reducer? */edit*

FilippoTib

Topic starter

Jan 10, 2024

Paul Macklin:
Paul Macklin:
) The closer you can get the filter to the sensor, the better it ought to go. Can you find a way to get it between the flattener and the sensor? Right now, it looks like it's substantially in front of the flattener. I think that's very consistent with all the internal reflections you are seeing.

I think I can bring the filter closer to the sensor by using a rotator that holds the filter instead of the nose connection. (And it is one of the next upgrades I would like to make)

However, I don't think I can fit it between the camera and the leveler so as not to change the backfocus (at most I would have to buy the clip version)
Paul Macklin:
2) Can you try putting up some screens to block neighbor light?

Yes the neighbour's light is already partially shielded and does not create any problems except for a very slight gradient.

The real problem is the street lamp which really makes a mess....
Not even being 20 metres away I am forced to shoot mainly subjects to the north or that are high enough not to be affected by the orange light...

Thank you again!

CS!

F.T.

You bet, and good luck!

Hmm, FWIW, I try to place my filter drawer right after my reducer (or flattener) and OAG. It can be part of your total distance. If you get a shorter T-ring, you might be able to work it out that way, too.

As I think about it, I *might* have a spare integrated filter drawer / cannon T-ring. I can dig for it at home to see if you like.

*edit* Now I think I see the separate T-ring in teh photo. Sorry, it's a little dark. What is that big adapter between the T-ring and your reducer? */edit*

A -> EOS-T2 Adapter
B -> Field Flattener
C -> Field Flattener nose (I would like to replace this piece with a rotator)
D -> Filter

FilippoTib

Topic starter

Jan 10, 2024 · Edited: Jan 10, 2024

Paul Macklin:
Paul Macklin:
) The closer you can get the filter to the sensor, the better it ought to go. Can you find a way to get it between the flattener and the sensor? Right now, it looks like it's substantially in front of the flattener. I think that's very consistent with all the internal reflections you are seeing.

I think I can bring the filter closer to the sensor by using a rotator that holds the filter instead of the nose connection. (And it is one of the next upgrades I would like to make)

However, I don't think I can fit it between the camera and the leveler so as not to change the backfocus (at most I would have to buy the clip version)
Paul Macklin:
2) Can you try putting up some screens to block neighbor light?

Yes the neighbour's light is already partially shielded and does not create any problems except for a very slight gradient.

The real problem is the street lamp which really makes a mess....
Not even being 20 metres away I am forced to shoot mainly subjects to the north or that are high enough not to be affected by the orange light...

Thank you again!

CS!

F.T.

You bet, and good luck!

Hmm, FWIW, I try to place my filter drawer right after my reducer (or flattener) and OAG. It can be part of your total distance. If you get a shorter T-ring, you might be able to work it out that way, too.

*edit* Now I think I see the separate T-ring in teh photo. Sorry, it's a little dark. What is that big adapter between the T-ring and your reducer? */edit*

Come to think of it, though, I have never tried to disassemble the front of the flattener... Maybe I can shorten the distance.... mmmm... I'll try tomorrow.

Thank you again!

Paul Macklin

Jan 10, 2024

Thanks! Hmm, and that "nose" goes into the 2" eyepiece holder in the OTA? interesting design. It's too bad you can't somehow get that filter in between A and B.

Could this or sometign like it work?

https://www.firstlightoptics.com/adapters/baader-protective-t-ring-for-canon-eos.html

Paul Macklin

Jan 10, 2024

Good luck! Please let us know!

FilippoTib

Topic starter

Jan 10, 2024

Paul Macklin:
Thanks! Hmm, and that "nose" goes into the 2" eyepiece holder in the OTA? interesting design. It's too bad you can't somehow get that filter in between A and B.

Could this or sometign like it work?

https://www.firstlightoptics.com/adapters/baader-protective-t-ring-for-canon-eos.html

I should try...

Thank you again!