Odd Shaped Stars

Discuss deep sky objects.
Post Reply
User avatar
Graeme1858 Great Britain
Co-Administrator
Co-Administrator
Articles: 1
Online
Posts: 7216
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.

Odd Shaped Stars

#1

Post by Graeme1858 »


The attached shows the top right corner of a recent image I captured. The stars are lopsided all facing a way from the centre of the image. I'm confident the collimation is good and the focus is good too. Can anyone tell me what the cause is please?

Image

It's M108, almost!

Thanks

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
Ruud
Orion Spur Ambassador
Articles: 0
Offline
Posts: 813
Joined: Sun Feb 09, 2020 9:56 pm
4
Location: the Netherlands
Status:
Offline

Re: Odd Shaped Stars

#2

Post by Ruud »


That looks like coma. Is this a new development on your SCT? Could also be coma + field curvature.

If this is new, did anything change like camera spacing?
7x50 Helios Apollo 8x42 Bresser Everest 73mm f/5.9 WO APO 4" f/5 TeleVue Genesis 6" f/10 Celestron 6SE 0.63x reducer 1.8, 2, 2.5 and 3x Barlows eyepieces from 4.5 to 34mm
User avatar
John Baars Netherlands
Co-Administrator
Co-Administrator
Articles: 5
Online
Posts: 2723
Joined: Sat May 11, 2019 9:00 am
4
Location: Schiedam, Netherlands
Status:
Online

TSS Awards Badges

TSS Photo of the Day

Re: Odd Shaped Stars

#3

Post by John Baars »


I agree with Ruud. Coma.
Quite normal for a normal standard SCT if it occurs in all corners. Deflection by the weight of the camera could be a cause.
Refractors in frequency of use : *SW Evostar 120ED F/7.5 (all round ), * Vixen 102ED F/9 (vintage), both on Vixen GPDX.
GrabnGo on Alt/AZ : *SW Startravel 102 F/5 refractor( widefield, Sun, push-to), *OMC140 Maksutov F/14.3 ( planets).
Most used Eyepieces: *Panoptic 24, *Morpheus 14, *Leica ASPH zoom, *Zeiss barlow, *Pentax XO5.
Commonly used bino's : *Jena 10X50 , * Canon 10X30 IS, *Swarovski Habicht 7X42, * Celestron 15X70, *Kasai 2.3X40
Rijswijk Public Observatory: * Astro-Physics Starfire 130 f/8, * 6 inch Newton, * C9.25, * Meade 14 inch LX600 ACF, *Lunt.
Amateur astronomer since 1970.
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: Odd Shaped Stars

#4

Post by UlteriorModem »


Yep looks like tilt to me.

Might look into a tilt ring.

https://optcorp.com/products/t2-tilt-ad ... gKhRPD_BwE

They are a bear to set up though, fair warning.
Tom

Current Equipment:
Mount: Celestron CGX-L
Scope: 130mm f7 APO
Cam: ASI071mc-pro
User avatar
Graeme1858 Great Britain
Co-Administrator
Co-Administrator
Articles: 1
Online
Posts: 7216
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: Odd Shaped Stars

#5

Post by Graeme1858 »


Ruud wrote: Sun May 10, 2020 10:55 am That looks like coma. Is this a new development on your SCT? Could also be coma + field curvature.

If this is new, did anything change like camera spacing?

Thanks Rudd.

Yes, it is a new development. As it goes, there's been quite a few changes recently! I added a guide scope mounted on a second dovetail bar on top of the OTA. Also, the black coat paint started to flake and I removed the corrector plate to clean it out. Also, the OTA has been posted to Yorkshire and back in a futile attempt to ascertain the reason for the faulty black paint coating. And finally, the camera fell out onto the brick patio a few weeks ago!

John Baars wrote: Sun May 10, 2020 1:53 pm I agree with Ruud. Coma.
Quite normal for a normal standard SCT if it occurs in all corners. Deflection by the weight of the camera could be a cause.

Thanks John

I've always used the same Canon 600D and I have only just noticed this effect in my images. Other than ensure all the fittings are tight is there any other solution if the weight of the camera is the cause?

UlteriorModem wrote: Sun May 10, 2020 3:37 pm Yep looks like tilt to me.

Might look into a tilt ring.

https://optcorp.com/products/t2-tilt-ad ... gKhRPD_BwE

They are a bear to set up though, fair warning.

Thanks Tom

That looks like a prescision adjustment tool. Now I know the cause, I'll try setting up more tightly and carefully. If that doesn't work then I'll look into trying a tilt ring.

Cheers chaps.

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
yobbo89 Australia
Moderator
Moderator
Articles: 0
Offline
Posts: 2560
Joined: Sat May 11, 2019 7:44 pm
4
Location: australia qld brisbane
Status:
Offline

TSS Photo of the Day

Re: Odd Shaped Stars

#6

Post by yobbo89 »


looks typical from a non edge sct and a full frame, is this in all corners or just one ?, how was your star test inside and out ? a reducer corrector should clean that up .
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: Odd Shaped Stars

#7

Post by UlteriorModem »


yobbo89 wrote: Sun May 10, 2020 4:37 pm looks typical from a non edge sct and a full frame, is this in all corners or just one ?, how was your star test inside and out ? a reducer corrector should clean that up .
Oh wait, that was not the full frame?

Can he post a full frame image? I may have been off base.
Tom

Current Equipment:
Mount: Celestron CGX-L
Scope: 130mm f7 APO
Cam: ASI071mc-pro
User avatar
yobbo89 Australia
Moderator
Moderator
Articles: 0
Offline
Posts: 2560
Joined: Sat May 11, 2019 7:44 pm
4
Location: australia qld brisbane
Status:
Offline

TSS Photo of the Day

Re: Odd Shaped Stars

#8

Post by yobbo89 »


yeah op, mentioned he attached an image of the top right section .
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
Graeme1858 Great Britain
Co-Administrator
Co-Administrator
Articles: 1
Online
Posts: 7216
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: Odd Shaped Stars

#9

Post by Graeme1858 »


yobbo89 wrote: Sun May 10, 2020 4:37 pm looks typical from a non edge sct and a full frame, is this in all corners or just one ?, how was your star test inside and out ? a reducer corrector should clean that up .

Thanks Yobbo.

I don't recall seeing this at all before the session of 07/05/20. I will have to go back and study a few images from the past.

What's a star test? :)
______________________________________________
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
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: Odd Shaped Stars

#10

Post by UlteriorModem »


yobbo89 wrote: Sun May 10, 2020 5:55 pm yeah op, mentioned he attached an image of the top right section .
Yea my bad for skimming the thread. Thanks for the correction.
Tom

Current Equipment:
Mount: Celestron CGX-L
Scope: 130mm f7 APO
Cam: ASI071mc-pro
User avatar
Graeme1858 Great Britain
Co-Administrator
Co-Administrator
Articles: 1
Online
Posts: 7216
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: Odd Shaped Stars

#11

Post by Graeme1858 »


Graeme1858 wrote: Sun May 10, 2020 6:17 pm
yobbo89 wrote: Sun May 10, 2020 4:37 pm looks typical from a non edge sct and a full frame, is this in all corners or just one ?, how was your star test inside and out ? a reducer corrector should clean that up.

Thanks Yobbo.

I don't recall seeing this at all before the session of 07/05/20. I will have to go back and study a few images from the past.

What's a star test? :)

So, I searched for star test inside and out! Didn't know there was a significant difference between which side of focus a doughnut could be! So I only did the one collimation adjustment and I don't know if it was inside or outside. I made a pin hole in tin foil, put it over a torch and put the torch at the end of the garden 40m away.

Here is the post adjustment image:

Image

Two new concepts learnt in one thread! :)

Thanks

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
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: Odd Shaped Stars

#12

Post by JayTee »


A better artificial star is to use a stainless steel ball bearing stuck in some modelers clay and the clay stuck on a fence post 50 to 100 meters away. Obviously, the sun needs to be out for this to work.

JT
∞ 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: 7216
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: Odd Shaped Stars

#13

Post by Graeme1858 »


My new hand set has arrived! Hooray! So I set up last night to sort out my collimation.

After aligning I chose Dubhe as my test star as it was close to the Zenith.

Here's moving in uncollimated.
Dubhe Move In.PNG
Here's moving out uncollimated.
Dubhe Move Out.PNG
Here's moving in collimated.
Dubhe Move In-C.PNG
Here's moving out collimated.
Dubhe Move Out-C.PNG
I'm happy with that!

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
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: Odd Shaped Stars

#14

Post by JayTee »


By jove, I think you've got it.
∞ 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: 7216
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: Odd Shaped Stars

#15

Post by Graeme1858 »


JayTee wrote: Tue May 12, 2020 10:53 pm By jove, I think you've got it.

Yeah, it looks ok. So the camera must have not been in properly last time or something.

Also, I think I need to collimate more frequently.

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/
jgass
Earth Ambassador
Articles: 0
Offline
Posts: 1
Joined: Fri Jul 17, 2020 4:04 pm
3
Location: USA
Status:
Offline

Re: Odd Shaped Stars

#16

Post by jgass »


Hello Graeme,

Please remember that after you collimate your telescope with the out of focus image at this level, you should move it closer to focus, such that the Poisson spot is visible so that you can judge its centering. Eventually, moving to in focus at high magnification to be able to judge the even illumination of the airy disk.

And, it is critical to always judge the adjustments after recentering the star in the field of view. Do always finish the last focuser move of an SCT anti-clockwise to seat the primary properly on the baffle.

Jim
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 “Deep sky”