NGC 891 Questions

[Starwiz]

19 x 15 minutes stacked in DSS.

Does anyone know what these streaks might be, indicated by the yellow arrow?  My first thought was stray light getting in somewhere, but the streaks appear in the same place on all the subs over nearly 5 hours.  Also, it's fairly dark in my back garden, so I can't think what light might be getting in anyway.

Also, I noticed some distant galaxies, indicated by the blue arrows.  Does anyone know what these are and their distances?

Thanks

John

 

[tooth_dr]

Can’t help! But Lovely image, one of my favourites!

[Stub Mandrel]

Those marks align perfectly with the relatively bright star Almach.

Normally, upload your image at Astrometry.net to find mystery objects.

The free package Stellarium suggests the biggest one is NGC 898

 

[AstroCava]

Hi,

About the artifacts pointed by the yellow arrow I think they must be some kind of reflection because if they were high clouds they should have been moved between frames. With low probability (too straight perhaps), some kind of IFN.

To identify the objects, the best way is using nova.astronomy.net because is a blind solver. Then you can use PixInsight to render a better looking annotated image or using PI from the beginning.

Have fun,

Sergio

NGC-IC
NGC and IC catalogs (9900 objects)
Name;RA(deg);Dec(deg);PixelX;PixelY;Common name
NGC891;35.638410;42.348306;329.326477;204.661419;
NGC898;35.834580;41.951444;804.191402;355.774424;

PGC
PGC HYPERLEDA I catalog of galaxies (983,261 galaxies)
Name;RA(deg);Dec(deg);PixelX;PixelY
PGC2188802;35.462500;41.900278;849.840595;26.584969
PGC2193819;35.483333;42.180000;521.318876;60.246194
PGC2192495;35.488750;42.106111;608.544203;60.924226
PGC2202439;35.587917;42.611944;16.883422;174.759197
PGC2188325;35.589167;41.873056;887.030693;136.314883
PGC2191336;35.602083;42.041667;688.988820;156.648563
PGC2194478;35.606667;42.214444;485.711443;169.864307
PGC2191363;35.633750;42.043056;688.604055;184.457797
PGC9031;35.637917;42.348889;328.620778;204.262204
PGC2189635;35.649167;41.945833;803.700033;192.840092
PGC9042;35.710417;42.158333;555.833994;257.581530
PGC2192261;35.746250;42.093889;633.100003;285.603069
PGC212965;35.815000;41.922778;837.219431;337.154726
PGC9073;35.834583;41.951111;804.583582;355.760669
PGC2190563;35.875417;41.998333;750.483338;393.919882
PGC212966;35.889167;41.899167;867.785406;401.079361
PGC2189221;35.898333;41.923889;839.004927;410.344165
PGC2190710;35.935417;42.006667;742.863583;446.921389
PGC2188688;35.942917;41.894167;875.638374;448.027301
PGC9101;35.973750;42.206111;509.341062;490.128824
PGC2191807;36.002917;42.067500;673.637805;508.991811
PGC9108;36.007917;41.996389;757.572123;509.978066
PGC2189446;36.025833;41.937222;827.896770;522.877393
PGC2194768;36.032083;42.228333;485.235824;542.151006
PGC2193253;36.126250;42.146944;584.367339;620.655941

[ebdons]

Hi, love that image, a great object to image when high in the sky? those are reflections maybe from a distant light source like stun mandrel said, or it looks like a diffraction effect from a nearby light source, or maybe thru a gap near the focuser, I used to get them from my laptop screen when at a particular angle? Ton

[Starwiz]

Thanks all, for the excellent replies.  I hadn't considered Almach being the source.

Does anyone know if there's a way to clean up the unwanted artifacts in Photoshop?

Thanks

John

[ebdons]

Hi, yes I think it's the same as the remove artifacts like plane vapour and trails utility, although PS can only do so much, and I just started using PS so folks on here will help more, you might have to re-image again, I normally use a UHC on LP images, but you can get defects on that filter as well, CLS is a "good alrounder" but I rarely use it if I have a sensitive sensor and longer exp times?  you could do another set of bias? and try and subtract that I think? hope you get it sorted. Ton

[ebdons]

Hi, I just saw this info, could these dust clouds be the stuff in the image? about halfway down the page is an image of the clouds. Ton http://www.msn.com/en-gb/news/techandscience/earth-has-two-extra-hidden-moons/ar-BBPrhIj?li=BBoPWjQ&ocid=mailsignout

[Stub Mandrel]

Most unlikely, I'm afraid they are both are far too faint and each covers an area  many times larger than your whole image.

[ebdons]

Yes they are large, but maybe only a part would be illuminated depending on the light source, anyway I never knew of these clouds of dust, right on our "doorstep"?

[Starwiz]

Here's what I ended up with after grabbing another 16 frames a few nights ago.  So, 35 x 15 minute frames in total from which I stacked the best 20.

Not the easiest of targets I've tried.

John

[ebdons]

Yes the definition is coming along nicely, a bit of a halo on the brighter stars, but that can be common on newts, you use the CLS but I get them using the UHC so maybe my 825 mono is just very sensitive? and you got some background galaxies as well. good work.

[AstroCava]

I prefer the first version mostly because the background... too much clip of shadows in last version in my opinion.

[Starwiz]

5 minutes ago, AstroCava said:

I prefer the first version mostly because the background... too much clip of shadows in last version in my opinion.

Yes, I did think that myself to some extent, but followed the Doug German tutorials and he set the black point at 7-8, so that's what I did too.  It got rid of the horrible lens-flare or whatever it was, so I decided to go with it.  Thanks for the comments.

John

[ollypenrice]

I think off-shot flare from Almach will, indeed, be the cause of the streaks. I do a lot of mosaics and the strange thing is that bright stars don't usually produce flares when they are in the frame, they only produce flares in frames further away. You might be lucky and find that by moving the galaxy well down in the framing you'd get a clean bit of background sky from which to make a patch. You wouldn't need a deep stack to do this, just enough to get some background sky. Making patches is much easier if you have Registar, by the way.

If trying to fix this in PS then I'd suggest making a copy layer and working first on the bottom layer with the top invisible. In Curves, pin the background sky at its normal level (Cursor on background then Ctrl Click) and put a fixing point in below that. Next pull down the curve above just above the background so as to kill the flares. Ignore the effect on the stars and galaxies.

 

Next make the top layer active and erase just the flares from the top layer. If you select the flares and background sky using the Colour Select tool you'll find it easier to avoid the stars and galaxy. This was working quickly on just a screen grab.

 

While you've improved the galaxy in your second version I really do think the background is clipped. So does Photoshop!

 

You should always have a least a little flat line to the left of the histogram pedestal.

Olly

 

[Starwiz]

3 hours ago, ollypenrice said:

I think off-shot flare from Almach will, indeed, be the cause of the streaks. I do a lot of mosaics and the strange thing is that bright stars don't usually produce flares when they are in the frame, they only produce flares in frames further away. You might be lucky and find that by moving the galaxy well down in the framing you'd get a clean bit of background sky from which to make a patch. You wouldn't need a deep stack to do this, just enough to get some background sky. Making patches is much easier if you have Registar, by the way.

If trying to fix this in PS then I'd suggest making a copy layer and working first on the bottom layer with the top invisible. In Curves, pin the background sky at its normal level (Cursor on background then Ctrl Click) and put a fixing point in below that. Next pull down the curve above just above the background so as to kill the flares. Ignore the effect on the stars and galaxies.

 

Next make the top layer active and erase just the flares from the top layer. If you select the flares and background sky using the Colour Select tool you'll find it easier to avoid the stars and galaxy. This was working quickly on just a screen grab.

 

While you've improved the galaxy in your second version I really do think the background is clipped. So does Photoshop!

 

You should always have a least a little flat line to the left of the histogram pedestal.

Olly

 

 

Many thanks Olly.

I'm at home at present recovering from a hernia op, so that's given me something to have a go at ?

John

[Starwiz]

On 15/11/2018 at 10:11, ollypenrice said:

You should always have a least a little flat line to the left of the histogram pedestal.

Hi Olly,

I checked my PSP data as per the final image I posted, and the graph is telling me that I hadn't clipped the black point, so I'm wondering if saving it to JPEG affects it in this way?

Thanks

John

 

[ollypenrice]

1 hour ago, Starwiz said:

Hi Olly,

I checked my PSP data as per the final image I posted, and the graph is telling me that I hadn't clipped the black point, so I'm wondering if saving it to JPEG affects it in this way?

Thanks

John

 

Strange, and the answer is that I don't know. What does the JPEG's histo look like on your machine?

In any event I'm sure the image as posted here is clipped: the indicators are the smooth, uniform blackness of the sky and way the stars are hard edged. Their gradual emergence from the background has been clipped.

Olly