Mosaics: how to image "blank" areas...

Discuss how you are able to get those fantastic images!!!
Post Reply
User avatar
ram United States of America
Saturn Ambassador
Articles: 0
Offline
Posts: 349
Joined: Tue Jun 11, 2019 3:21 am
4
Location: Youngstown, NY, USA
Status:
Offline

TSS Photo of the Day

Mosaics: how to image "blank" areas...

#1

Post by ram »


As most targets that one plans to do a mosaic with aren't perfect rectangles, there's a lot of "blank" space that may contain a small portion of the target (let's say 10%) but 90% of it is the sky background. It'd be nice if one spent 10 hours on the main target area to not spend 10 hours also on the frame for the corner. But if you go under significantly it makes matching the images harder (or at least it has been though I got around it eventually by matching the noise levels using TGVdenoise which I promptly then forgot how to do again).

Is it possible to do mosaics as I'm suggesting above, take 10 hours (say) of one part of the target, and take one hour of another part and have it stitch togeher acceptably? Or does each panel need to be 10 hours for it to work out?

What's the secret to getting a bunch of master lights of different parts of the sky that could be stitched together to form a mosaic look even? Is it controlling the background? Is it the noise level? The lightness? What?

--Ram
Tubes: Celestron 9.25" 235mm f/10 XLT EdgeHD SCT; Meade ETX 80mm f/5 achromat; Coronado SolarMax II 60mm f/6.6 Hα <0.7Å BF10 solar; Stellarvue 70mm f/6 triplet apochromat; Obsession UC18 457mm f/4.2 with Argo Navis & ServoCAT; Takahashi FS128 5" f/8.1 and FC100DF 4" f/7.4 fluorite doublet apochromats. Mounts: AVX; LXD75; Paramount MyT. Eyepieces: 2" Tele Vue Ethos 4.7/13/21mm, Paracorr, 2,4x Powermate; Stellarvue 0.8x, Takahashi 0.7x, 0.66x reducer/corrector. Cameras: ZWO ASI120MC-S; Lodestar X2c; X2m; Canon T7i; QHY163M; QHY247C; QHY294M-Pro. Filters: 1.25" Astrodon 5nm Ha, 3nm O3 and S2; Chroma LRGB.
Image
User avatar
yobbo89 Australia
Moderator
Moderator
Articles: 0
Online
Posts: 2561
Joined: Sat May 11, 2019 7:44 pm
4
Location: australia qld brisbane
Status:
Online

TSS Photo of the Day

Re: Mosaics: how to image "blank" areas...

#2

Post by yobbo89 »


I would like to know the conclusion too, I have a 9 panel and one corner has no signal and pix insight has made a bad histogram fit, it's almost looks like I need to make 2 x more. Integration for that last panel..
scopes :gso/bintel f4 12"truss tube, bresser messier ar127s /skywatcher 10'' dob,meade 12'' f10 lx200 sct
cameras : asi 1600mm-c/asi1600mm-c,asi120mc,prostar lp guidecam, nikkon d60, sony a7,asi 290 mm
mounts : eq6 pro/eq8/mesu 200 v2
filters : 2'' astronomik lp/badder lrgb h-a,sII,oIII,h-b,Baader Solar Continuum, chroma 3nm ha,sii,oiii,nii,rgb,lowglow,uv/ir,Thousand Oaks Solar Filter,1.25'' #47 violet,pro planet 742 ir,pro planet 807 ir,pro planet 642 bp ir.
extras : skywatcher f4 aplanatic cc, Baader MPCC MKIII Coma Corrector,Orion Field Flattener,zwo 1.25''adc.starlight maxi 2" 9x filter wheel,tele vue 2x barlow .

Image
User avatar
UlteriorModem
Local Group Ambassador
Articles: 0
Offline
Posts: 2112
Joined: Sat May 11, 2019 1:32 am
4
Location: Florida
Status:
Offline

TSS Photo of the Day

Re: Mosaics: how to image "blank" areas...

#3

Post by UlteriorModem »


Thing is you want all the panels to be more or less the same. That includes unfortunately background noise.

So 'blank' panels (if such a thing exists) would be shot at the same duration, gain, offset, whatever, to match the other panels.
Tom

Current Equipment:
Mount: Celestron CGX-L
Scope: 130mm f7 APO
Cam: ASI071mc-pro
User avatar
JayTee United States of America
Universal Ambassador
Articles: 2
Offline
Posts: 5619
Joined: Thu Apr 25, 2019 3:23 am
4
Location: Idaho, USA
Status:
Offline

TSS Awards Badges

TSS Photo of the Day

Re: Mosaics: how to image "blank" areas...

#4

Post by JayTee »


[mention]JimMinCT[/mention] let's see if Jim can answer this question. Hey Jim, can you answer this question?
∞ Primary Scopes: #1: Celestron CPC1100 #2: 8" f/7.5 Dob #3: CR150HD f/8 6" frac
∞ AP Scopes: #1: TPO 6" f/9 RC #2: ES 102 f/7 APO #3: ES 80mm f/6 APO
∞ G&G Scopes: #1: Meade 102mm f/7.8 #2: Bresser 102mm f/4.5
∞ Guide Scopes: 70 & 80mm fracs -- The El Cheapo Bros.
∞ Mounts: iOptron CEM70AG, SW EQ6, Celestron AVX, SLT & GT (Alt-Az), Meade DS2000
∞ Cameras: #1: ZWO ASI294MC Pro #2: 662MC #3: 120MC, Canon T3i, Orion SSAG, WYZE Cam3
∞ Binos: 10X50,11X70,15X70, 25X100
∞ EPs: ES 2": 21mm 100° & 30mm 82° Pentax XW: 7, 10, 14, & 20mm 70°

Searching the skies since 1966. "I never met a scope I didn't want to keep."

Image
User avatar
Graeme1858 Great Britain
Co-Administrator
Co-Administrator
Articles: 1
Online
Posts: 7217
Joined: Mon Jun 24, 2019 7:16 pm
4
Location: North Kent, UK
Status:
Online

TSS Awards Badges

TSS Photo of the Day

I Broke The Forum.

Re: Mosaics: how to image "blank" areas...

#5

Post by Graeme1858 »


Good question Ram. My Lunar mosaic recently had the same issue. The best I could do was visually compare the thumbnails of the 9 frames and tweak each curve to try to manually match them.

Looking forward to seeing more effective solutions posted!

Regards

Graeme
______________________________________________
Celestron 9.25 f10 SCT, f6.3FR, CGX mount.
ASI1600MM Pro, ASI294MC Pro, ASI224MC
ZWO EFW, ZWO OAG, ASI220MM Mini.
APM 11x70 ED APO Binoculars.

https://www.averywayobservatory.co.uk/
User avatar
ram United States of America
Saturn Ambassador
Articles: 0
Offline
Posts: 349
Joined: Tue Jun 11, 2019 3:21 am
4
Location: Youngstown, NY, USA
Status:
Offline

TSS Photo of the Day

Re: Mosaics: how to image "blank" areas...

#6

Post by ram »


So I have some solutions that I've been using for certain targets under certain conditions (my two most recent at this point). Let's say the main part of the target covers 50-75% of the frames in the telescope you want to image in. So you spend all your effort on that main part. Now, if you want to get the remaining 50-25%, then you need to do a mosaic which could be multiple panels but at least two. This takes away time from going in depth and focussing on breath or time that could be used on other targets. A solution I have is to use to image scales/resolutions. Do the main part with the best resolution you want to do it at, and then do the wider field one with an appropriate scope that covers the whole area desired. If necessary, you can even just use a camera lens which will give you a huge area.

I've now done this for two targets and I'm still processing them slowly which, like learning to do mosaics, comes with its set of headaches and experimentation. The tools used for mosaic processing and for handling different exposure lengths (GradientMergeMosaic, GradientHDRComposition, HDRComposition) can be used here but I've found that ImageIntegration with LocalNormalization and Drizzle solves all of this, even doing the borders and creating seamless images. Drizzle is designed to compensate for undersampling (which you'll likely do in the wider field imaging) and LocalNormalization will help deal with the borders/seams and help with creating an even appearance throughout.

But supposing that both the ImageIntegration approach AND the mosaic reconstruction approach doesn't work or you want to do something even easier, then all you have to do is create an integrated image of the central area, a separate image of the background area (with the lower resolution), process both, and insert the smaller region into the larger region using Steve's method of image insertion he talked about.

I think both these solutions get around the differential in noise and signal problem in different ways but that's the idea, that for the most of the background that isn't as important, you don't have to spend as much time as the main area, and even if you did, worst case the effort is as much as a two panel mosaic, not a five or six panel one.

Let's say you're a perfectionist and you want 100% of your image area to be filled at the highest resolution and therefore you indeed do a 12 panel mosaic but now you're left with some holes that will require more than one panel, then again, you can use the above trick.

--Ram
Tubes: Celestron 9.25" 235mm f/10 XLT EdgeHD SCT; Meade ETX 80mm f/5 achromat; Coronado SolarMax II 60mm f/6.6 Hα <0.7Å BF10 solar; Stellarvue 70mm f/6 triplet apochromat; Obsession UC18 457mm f/4.2 with Argo Navis & ServoCAT; Takahashi FS128 5" f/8.1 and FC100DF 4" f/7.4 fluorite doublet apochromats. Mounts: AVX; LXD75; Paramount MyT. Eyepieces: 2" Tele Vue Ethos 4.7/13/21mm, Paracorr, 2,4x Powermate; Stellarvue 0.8x, Takahashi 0.7x, 0.66x reducer/corrector. Cameras: ZWO ASI120MC-S; Lodestar X2c; X2m; Canon T7i; QHY163M; QHY247C; QHY294M-Pro. Filters: 1.25" Astrodon 5nm Ha, 3nm O3 and S2; Chroma LRGB.
Image
User avatar
yobbo89 Australia
Moderator
Moderator
Articles: 0
Online
Posts: 2561
Joined: Sat May 11, 2019 7:44 pm
4
Location: australia qld brisbane
Status:
Online

TSS Photo of the Day

Re: Mosaics: how to image "blank" areas...

#7

Post by yobbo89 »


very nice ram, i'll have to break out the wider refractor when nebula are in season again, i have a nice 9 panel that i'm still keen on finishing ...

i've done mix matching of different scopes before with ok results, but never on a mosaic.
scopes :gso/bintel f4 12"truss tube, bresser messier ar127s /skywatcher 10'' dob,meade 12'' f10 lx200 sct
cameras : asi 1600mm-c/asi1600mm-c,asi120mc,prostar lp guidecam, nikkon d60, sony a7,asi 290 mm
mounts : eq6 pro/eq8/mesu 200 v2
filters : 2'' astronomik lp/badder lrgb h-a,sII,oIII,h-b,Baader Solar Continuum, chroma 3nm ha,sii,oiii,nii,rgb,lowglow,uv/ir,Thousand Oaks Solar Filter,1.25'' #47 violet,pro planet 742 ir,pro planet 807 ir,pro planet 642 bp ir.
extras : skywatcher f4 aplanatic cc, Baader MPCC MKIII Coma Corrector,Orion Field Flattener,zwo 1.25''adc.starlight maxi 2" 9x filter wheel,tele vue 2x barlow .

Image
User avatar
UlteriorModem
Local Group Ambassador
Articles: 0
Offline
Posts: 2112
Joined: Sat May 11, 2019 1:32 am
4
Location: Florida
Status:
Offline

TSS Photo of the Day

Re: Mosaics: how to image "blank" areas...

#8

Post by UlteriorModem »


I so want to do some mosaics with the f3.9 astrograph. Problem is I cant get enough clear sky time to pull it off.

Hopefully maybe this winter.
Tom

Current Equipment:
Mount: Celestron CGX-L
Scope: 130mm f7 APO
Cam: ASI071mc-pro
Post Reply

Create an account or sign in to join the discussion

You need to be a member in order to post a reply

Create an account

Not a member? register to join our community
Members can start their own topics & subscribe to topics
It’s free and only takes a minute

Register

Sign in

Return to “Image processing”