Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Collimation C9.25 - Before and after

  • Please log in to reply
8 replies to this topic

#1 Daniele

Daniele

    Sputnik

  • -----
  • topic starter
  • Posts: 38
  • Joined: 14 May 2020
  • Loc: Tuscany, Italy.

Posted 13 July 2020 - 04:39 AM

Hello,

 

Yesterday night i tried to improve my finest collimation.

 

Before: https://www.cloudyni...my-collimation/

 

Now: https://ibb.co/mqZHGb5

 

Is this good enough now? I stacked about 400 frame to achieve that picture.

 

I'm in Italy and both Jupiter and Saturn are not so high in the sky.

 

I have an ASI 290mc and Jupiter looks very bad on the screen! I barely can see some details due the turbolence. 

 

I guess the problem now is the turbolence and no longer the collimation confused1.gif


Edited by Daniele, 13 July 2020 - 04:44 AM.


#2 pathint

pathint

    Sputnik

  • *****
  • Posts: 41
  • Joined: 13 Nov 2019

Posted 13 July 2020 - 03:00 PM

I can see either pinched optics or astigmatism, or tube currents. Since this is an SCT, most likely it is tube currents. I find videos to be more helpful in diagnosing aberration. 

Hello,

 

Yesterday night i tried to improve my finest collimation.

 

Before: https://www.cloudyni...my-collimation/

 

Now: https://ibb.co/mqZHGb5

 

Is this good enough now? I stacked about 400 frame to achieve that picture.

 

I'm in Italy and both Jupiter and Saturn are not so high in the sky.

 

I have an ASI 290mc and Jupiter looks very bad on the screen! I barely can see some details due the turbolence. 

 

I guess the problem now is the turbolence and no longer the collimation confused1.gif


Edited by pathint, 13 July 2020 - 03:02 PM.


#3 chuckscap

chuckscap

    Apollo

  • *****
  • Posts: 1,180
  • Joined: 18 Jul 2009
  • Loc: Colorado Springs, CO USA

Posted 13 July 2020 - 04:40 PM

Hard to tell it's definitely better.  you need to zoom in a lot more and defocus both in and out of focus.  I generally collimate using a reticle eyepiece, but your camera can work too.  You generally want perfect rings in and out of focus at twice the magnification you will ever use.  So with my C14 I collimate with at 10m eyepiece and a 2x barlow giving approximately 800 power.



#4 MarMax

MarMax

    Vostok 1

  • *****
  • Posts: 141
  • Joined: 27 May 2020
  • Loc: Los Angeles

Posted 13 July 2020 - 06:26 PM

You can also try a Duncan Mask. I've found seeing the so called "Airy disk" almost impossible with tube currents and light pollution. If you are not using 400x or close to it you should try it. The Duncan Mask really helped with my final collimation. I just cut it out of cardboard, took about 30 minutes to lay out and cut. Here's the post with the layout for a C11 and you'll need to modify it for the C9.25, if you think it's worth trying.

 

 


  • rjaszcz likes this

#5 rjaszcz

rjaszcz

    Sputnik

  • *****
  • Posts: 29
  • Joined: 09 Jun 2017
  • Loc: San Antonio, TX

Posted 14 July 2020 - 03:07 PM

You can also try a Duncan Mask. I've found seeing the so called "Airy disk" almost impossible with tube currents and light pollution. If you are not using 400x or close to it you should try it. The Duncan Mask really helped with my final collimation. I just cut it out of cardboard, took about 30 minutes to lay out and cut. Here's the post with the layout for a C11 and you'll need to modify it for the C9.25, if you think it's worth trying.

Duncan mask really helps with my 8 inch SCT too!



#6 dansawyer

dansawyer

    Explorer 1

  • *****
  • Posts: 60
  • Joined: 22 Nov 2018

Posted 18 July 2020 - 07:09 PM

The corrector alignment pads are long missing. I speculated that insulator from small wire would work. I found short pieces from 20 gauge solid were about the right diameter and compressed to make a solid fit. 

I hope this idea works for someone else. 



#7 gnowellsct

gnowellsct

    Hubble

  • *****
  • Posts: 16,791
  • Joined: 24 Jun 2009

Posted 19 July 2020 - 10:28 AM

I can see either pinched optics or astigmatism, or tube currents. Since this is an SCT, most likely it is tube currents. I find videos to be more helpful in diagnosing aberration.

Tube currents do not make a triangular star. Something's pinched. Might be the diagonal or the primary mirror lock nut.

Also that's a 400 frame stack. Not a tube current.

Edited by gnowellsct, 19 July 2020 - 10:30 AM.

  • mclewis1 likes this

#8 pathint

pathint

    Sputnik

  • *****
  • Posts: 41
  • Joined: 13 Nov 2019

Posted 21 July 2020 - 02:51 PM

tube current goes only in one direction so even after stacking it will show. It is very rare to have pinched mirror in an SCT.

Tube currents do not make a triangular star. Something's pinched. Might be the diagonal or the primary mirror lock nut.

Also that's a 400 frame stack. Not a tube current.



#9 Asbytec

Asbytec

    Guy in a furry hat

  • *****
  • Posts: 17,191
  • Joined: 08 Aug 2007
  • Loc: Pampanga, PI

Posted 23 July 2020 - 07:50 AM

"Is this good enough now? I stacked about 400 frame to achieve that picture."

Very much improved collimation compared to your previous link.

Something is odd, though, in that the first diffraction ring has two brighter lobes and (from what I can see on my phone), the Airy disc is a bit elongated. It might well be a tube current, as mentioned. Dunno.

Can you defocus a bit inside and outside and take some images? Maybe we can get a feel for what's going on. I forget how much defocus, a couple millimeters IIRC. Enough to see a few diffraction rings, anyway.


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics