"Photobombing" Stars. - Forums

Topic starter

Mar 14, 2021

Over the past few nights I have been doing some NB imaging of Sh2-308 aka The Dolphin Head Nebula.

It is a challenging and faint object. However, that can be addressed simply with more time.

What really irked me was the presence of the bright star 1 sigma Canis Majoris in the "forehead" of the Dolphin.

Differing reflections of my NB filters impressed an ugly tattoo on my Dolphins forehead in the final image. Perhaps this could have been fixed by more sophisticated processing techniques (which I am too old to learn) or by Astrodon NB filters (which I am too mean to buy) but it got me thinking what other really annoying stars are there out there for AP'ers.

The "poster child" is probably Alnitak which photobombs the Flame and Horsehead.

But what others have driven you mad? I would love to learn (and potentially avoid). These things are more annoying than Starlink.

matthew.maclean

Mar 14, 2021

The bright star on the edge of the Veil Nebula (52 Cygni I believe) often looks awkward in processed shots to me. The Trapezium cluster in the Orion nebula is always a struggle too!

Victor Van Puyenbroeck

Mar 14, 2021

Tejat near IC443 (Jelly fish nebula) is another annoying one, especially for the microlensing in the popular ASI1600MM camera.

Brian Boyle

Topic starter

Mar 14, 2021

Matthew, Good call on the 52 Cygni. The Trapezium I can forgive, but only because a few 3-5sec subs and use of the HDRCombination tool in PI works a treat on them. CS Brian

Brian Boyle

Topic starter

Mar 14, 2021

Hi Victor, Another good suggestion for the list. I notice you mention the microlensing effector on the ASI1600MM camera. Is this what I am seeing with my NB filters (and some of the broadband ones too)? The scattered light looks an orthogonal cross with small points and arc in the corners. A bit disappointing if this were the case.

Björn Arnold

Mar 14, 2021

Hi @Brian Boyle ,

I admit I haven't been shooting NB yet, so I can only talk about my full spectrum imaging. Just as a little foreword.

Since you've mentioned Alnitak, which I had great respect for when I tried to shoot the Flame and Horsehead, I am wondering if you'd consider Alnitak on this image as "photobombed" (it's not a quantitatively well defined term, I guess)? https://astrob.in/czh203/0/
IMHO, I think I could tame that horse quite well, as I had seen images where Alnitak was much brighter without Flame and Horsehead being much brighter at the same time.

CS!
Björn

CCDMike

Mar 14, 2021

Same here on my horsehead https://astrob.in/895i5y
I could smoth it a little bit awy with the ligh pollution tool in APP (sounds right

) but I am with others here, too: It's part of the composition.

Victor Van Puyenbroeck

Mar 14, 2021 · Edited: Mar 14, 2021

Brian Boyle:
Hi Victor, Another good suggestion for the list. I notice you mention the microlensing effector on the ASI1600MM camera. Is this what I am seeing with my NB filters (and some of the broadband ones too)? The scattered light looks an orthogonal cross with small points and arc in the corners. A bit disappointing if this were the case.

That's the microlensing effect indeed. Panasonic delivers the MN34230 sensor without an AR coating on the chip cover glass. Camera manufacturers cannot fix this. The effect will be more or less pronounced depending on the brightness of the star and properties of the optical train.

Filter reflections will look different, they are normally circular and can stack on top of the orthogonal arc pattern from the microlenses.

Honeycakehorse

Mar 14, 2021

Haha, good topic!
My "pain in the *ss" award goes to 52 Cygni as well!
I really love the veil nebula and it was one of my first narrowband images. Without much knowledge about processing, i wasn't able to cope with these ugly reflections.
Still it is one of my worst images and i hate that star nearly as much as i hate a fullmoon.

What else drives me mad…? hm.
I like the hubble palette and try to shoot classic SHO style.
Often i try to get 10+ hours per filter - sometimes over serveral nights.
Unfortunately some object tend to have really weak SII layers, which makes the final image really bad in comparison to a nice, clean bicolor image.
Wasting so much imaging time hurts bad ._.

Brian Boyle

Topic starter

Mar 14, 2021

Honeycakehorse:
Haha, good topic!
My "pain in the *ss" award goes to 52 Cygni as well!
I really love the veil nebula and it was one of my first narrowband images. Without much knowledge about processing, i wasn't able to cope with these ugly reflections.
Still it is one of my worst images and i hate that star nearly as much as i hate a fullmoon.

What else drives me mad...? hm.
I like the hubble palette and try to shoot classic SHO style.
Often i try to get 10+ hours per filter - sometimes over serveral nights.
Unfortunately some object tend to have really weak SII layers, which makes the final image really bad in comparison to a nice, clean bicolor image.
Wasting so much imaging time hurts bad ._.

Hi HCH,
52 Cygni is now ahead by a nose in the race to the most annoying star.

Great point about the SII strength. As a veteran of 3 NB images (!), I wholeheartedly agree.

At the risk of contradicting Kermit, it is quite easy to be green. You can sub the s**t out of [SII] and still get no red.

I guess many folks use SNCR (or its equivalent in non-PI software) to take out the green from the SHO palette, leaving the classic baby blue and orange colours. I prefer something, a little more (three) colourful and how found the tip of stretching the hue in CurvesTransformation, couple with a little bit of SNCR to work for me.

But, of course, that is based on extensive experience with three images. And one not only had no [SII] but very little Halpha either.

CS Brian
One is then faced with the dilemma of "Do I sub the s**t out of SII, stretch the same out of the red channel in post-processing.
I have taken the coward's approach so far. Simply take the same in each SHO NB and then use a little bit of SNCR

Honeycakehorse

Mar 16, 2021 · Edited: Mar 16, 2021

Ok lets go on! I thought about this topic for a while and there is so much that annoys me

1) Getting started ! Without help of someone who is into that hobby, it felt like studying to a masters degree.
I had so many many questions and was swimming in quicksand.
Equipment choices, which accessories do i need?
What is a reducer? Do i need a field flattener? FWHM? f/l? binning? ASCOM? Backfocus?
Why are 17 of my 56 required drivers and software not working ?
Why is my new usb cable not compatible to my mount?
(before getting to know plate solving ->) Where the f*ck are my stars for 3 star alignment? (this was really nearly impossible for me)
How do i stop my heart attack after the mount moved the telescope into impossible angles and made stuttering noises with my poor motors, after a failed alignment?
... i could go on for hours with that list..

2) Setting up the equipment and disassembling it ... again... and again....... aaaand again. All these beaufitul screws and cables and knobs..
Doing the balancing game over and over again, finding polaris over and over again...
I wish i had a house with a garage or a selfmade AP shed like some of you built on your own (yes @Brian Boyle i saw your pictures and i'm a little bit jealous for your comfort ;P)

3) Flats! Jesus! SII, why can't you be like L? 400s for SII, 300s for HA and 210s for OIII is a pretty long time for each session :-( (thats only to get at about 50% ADU values... could even be worse!)

4) I hate my old images! The more experience i get, the more i hate older images.
Why did i butcher the galaxy by oversaturating it by 300%?
Why did i use Curves like a maniac?
Why didn't i recognise that i'm completly out of focus?
Why is there vignetting in my final image? What went wrong with DBE?

... and so on. This list could go on forever as well. On top of that, i usually try to print my astrophotography onto acrylglas, which is not cheap. Realising that the images sucks, hurts twice.

Enough for today. Did you suffer similarly?
Clear skies,
honeycakehorse

Patrick Graham

Mar 31, 2021

I gotta laugh! Thought I was the only one out here overwhelmed by all the "stuff" we have to do to get a good image. I've been learning (a challenging thing to do for this 67 year old!) that even with all the best equipment (there's always something I gotta have), there is no substitute for good old fashioned trial and error learning. The secret for me - and often elusive- is patience, and making small improvements over time. My guitar teacher would always say, "practice, practice, practice; the only way to play like the pros". So true here!

Clear Skies

Patrick