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

ASTAP - TILT & Backfocus Measurement

  • Please log in to reply
10 replies to this topic

#1 Zwiesel

Zwiesel

    Lift Off

  • -----
  • topic starter
  • Posts: 5
  • Joined: 05 Dec 2023

Posted 11 December 2023 - 07:41 AM

Hey Guys, 

 

I recently bought a RASA 8 and I operate it with a ZWO 2600MC + 7.5mm spacer. And - like 99% of all Rasa Users - I see 

unsharp stars in my right upper corner - even worse at the very right - and still at the bottomo right corner. 

 

I am trying to elaborate whether this is back-focus or Tilt. And for this, I was told ASTAP is one of the best tools.

When I run Monitor - and press F5 and F4 I get this result

 

ASTAP-Result.png

 

Question: Is there anyone who can give me some introduction, how to proceed best? 

 

Thanks

 

 

 

 



#2 GaryShaw

GaryShaw

    Mercury-Atlas

  • *****
  • Posts: 2,989
  • Joined: 28 Nov 2017
  • Loc: Massachusetts / Wyoming

Posted 11 December 2023 - 08:58 AM

Hi - there was no ‘result’ attached….


  • Zwiesel likes this

#3 Zwiesel

Zwiesel

    Lift Off

  • -----
  • topic starter
  • Posts: 5
  • Joined: 05 Dec 2023

Posted 11 December 2023 - 09:09 AM

Maybe this way?

 

ASTAP-Result.png



#4 GaryShaw

GaryShaw

    Mercury-Atlas

  • *****
  • Posts: 2,989
  • Joined: 28 Nov 2017
  • Loc: Massachusetts / Wyoming

Posted 11 December 2023 - 09:17 AM

There you go! ASTAP says you have a tilt issue. If you have a tilt plate on your camera, you can just start the adjustment process. I recall reading posts recently about how to get continuous visual feedback as this diagram changes - as you make tilt adjustments. You might seek those posts out if you haven’t already found them. I imagine this might be a tedious process so good luck, go slow and have patience.

Gary


  • Zwiesel likes this

#5 fmendes

fmendes

    Surveyor 1

  • *****
  • Posts: 1,633
  • Joined: 20 Apr 2020
  • Loc: Houston, TX

Posted 11 December 2023 - 09:51 AM

Yes, there's a whole topic about this (more than 40 pages!), but I can't find it right now.

 

So, to add to this subject, remember that the image from ASTAP is upside down. If you want to see it upside-up, there's an option under the menu View.

 

Also looks like backfocus is a tiny bit short.


  • Zwiesel likes this

#6 Zwiesel

Zwiesel

    Lift Off

  • -----
  • topic starter
  • Posts: 5
  • Joined: 05 Dec 2023

Posted 11 December 2023 - 10:00 AM

Thanks Gary

Yes I have seen plenty posts about this issue. Especially when it comes to the Rasa ;)  the question is: In ASTA there shall be an information quoting which screw I need to adjust. But yet I cant find this information - cause atm, which of these 3 I need to touch :D

@ Apollo: Yes I have found some, but yet I havent found a good tutorial how to proceed best step by step. :) for example - ASTAP is obviously able to tell you which corner of your Astrocam you should focus on to adjust the screw. Cause yet, I havent found that menu or information. How can I know which screw it is? 

and Backfocus: Due to the Off-Axis Abberation? I hope not, cause the backfocus of the RASA is 25mm and the Zwo 2600 has 16,5mm and therefore I added 1x 7,5mm Spacer 



#7 nou

nou

    Mariner 2

  • -----
  • Posts: 214
  • Joined: 28 Apr 2022

Posted 11 December 2023 - 10:49 AM

1. switch to triangle in ASTAP inspector window

2. set angle so the triangle correspond to adjusting screws in tilt.

3. adjust screw that is off according to triangle diagram.


  • Zwiesel likes this

#8 Zwiesel

Zwiesel

    Lift Off

  • -----
  • topic starter
  • Posts: 5
  • Joined: 05 Dec 2023

Posted 11 December 2023 - 11:24 AM

Hey Vostok 1

 

thanks for the hint. Short question(s)

 

1. From that pic - how could I know which Corner belongs to which Screw (when I stand in front of the camera). or is it then, try and error? :)

2. Do I read the picture correctly, that the perfect corners (all 3) would be at 3,90 

 

 

Rectangle.png



#9 fmendes

fmendes

    Surveyor 1

  • *****
  • Posts: 1,633
  • Joined: 20 Apr 2020
  • Loc: Houston, TX

Posted 11 December 2023 - 12:12 PM

Hey Vostok 1

 

thanks for the hint. Short question(s)

 

1. From that pic - how could I know which Corner belongs to which Screw (when I stand in front of the camera). or is it then, try and error? smile.gif

2. Do I read the picture correctly, that the perfect corners (all 3) would be at 3,90 

 

 

 

 

0. To make your work easier, find out where is the top of the camera. You can use the gas filling screw as reference. It is either on top or bottom of the sensor, depending on the manufacturer. Rotate your camera so top os the sensor is point up physically.

1. Say that you obtained the above image after task above. As I said, looking from behind, the image shown in ASTAP is flipped upside down, left is left and right is right. So, still looking the camera from behind, the right side of the sensor should be brought closer to the telescope. Always refocus between measurements.

2. Around that, but remember that seeing also represents a very relevant factor.



#10 GaryShaw

GaryShaw

    Mercury-Atlas

  • *****
  • Posts: 2,989
  • Joined: 28 Nov 2017
  • Loc: Massachusetts / Wyoming

Posted 11 December 2023 - 04:38 PM

and Backfocus: Due to the Off-Axis Abberation? I hope not, cause the backfocus of the RASA is 25mm and the Zwo 2600 has 16,5mm and therefore I added 1x 7,5mm Spacer 

Perfect, then add a 1mm ring and you’re there. 
Gary



#11 Zwiesel

Zwiesel

    Lift Off

  • -----
  • topic starter
  • Posts: 5
  • Joined: 05 Dec 2023

Posted 14 December 2023 - 03:25 AM

Thank you very much for your input - I am waiting now for a CS (havent had it since weeks) and gonna try it 

 

I keep you posted




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