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

Orion ED80T CF possible focuser sag or bad flattener?

  • Please log in to reply
9 replies to this topic

#1 Rydeen 98

Rydeen 98

    Explorer 1

  • *****
  • topic starter
  • Posts: 70
  • Joined: 06 Feb 2018
  • Loc: New Mexico

Posted 22 October 2020 - 04:08 PM

Hi all.  I have an Orion ED80T CF that I recently purchased new from Highpoint Scientific.  It seems to be a great little scope but I've now discovered a small issue.  I recently took one of my best images with it but I also noticed that my stars are elongated only on the top right corner.  I would think if it was back focus it would be uniform in all of the corners.  My image train is my ASI294mc Pro with the 11mm spacer, the 16.5mm spacer, a ZWO filter drawer (basically a 21 mm spacer) connected to the Orion Field Flattener for Short Refractors (non-reducing) into the scope.  I use the camera with my other scope which used the same + a few more spacers into a Starizona SCT corrector III.  There is no elongated star issues in my SCT set up which makes me want to disregard possible sensor tilt.  Is there anything that is known to cause this issue with the stars?  I know many people replace the focuser on these with a Moonlite.  Or maybe I just got a bad flattener?

 

M45 the Pleiades 10/17/20

 


  • areyoukiddingme likes this

#2 astronautgenius

astronautgenius

    Vostok 1

  • *****
  • Posts: 106
  • Joined: 07 Jul 2015
  • Loc: Los Angeles, CA

Posted 22 October 2020 - 04:36 PM

It looks like the stars in the lower-right corner are streaking horizontally, and in the upper-left they are streaking vertically, more or less. The star aberrations seem to be "pointing" to the lower-left corner, do you know if that corner would have been the one that was oriented "down" during imaging?



#3 Rydeen 98

Rydeen 98

    Explorer 1

  • *****
  • topic starter
  • Posts: 70
  • Joined: 06 Feb 2018
  • Loc: New Mexico

Posted 22 October 2020 - 04:50 PM

It looks like the stars in the lower-right corner are streaking horizontally, and in the upper-left they are streaking vertically, more or less. The star aberrations seem to be "pointing" to the lower-left corner, do you know if that corner would have been the one that was oriented "down" during imaging?

I'm not sure on this.  I honestly didn't even see that issue as it's barely apparent.  This was pre-meridian flip so everything was oriented right side up.  If this was the case what would you recommend I try?  Fine tune the back focus?  I have a few of those 1mm spacers that came with the camera.



#4 astronautgenius

astronautgenius

    Vostok 1

  • *****
  • Posts: 106
  • Joined: 07 Jul 2015
  • Loc: Los Angeles, CA

Posted 22 October 2020 - 05:19 PM

It's hard to say what the culprit could be, you'll have to experiment a bit. It certainly seems the "center of focus" on the sensor is shifted to the lower left in that image, so maybe try some test shots with the camera rotated to different orientations. Also, try an image with no filter, here's a thread where the suspected focuser sag ended up being a defective filter:
https://www.cloudyni...age-plane-tilt/



#5 Rydeen 98

Rydeen 98

    Explorer 1

  • *****
  • topic starter
  • Posts: 70
  • Joined: 06 Feb 2018
  • Loc: New Mexico

Posted 22 October 2020 - 05:31 PM

It's hard to say what the culprit could be, you'll have to experiment a bit. It certainly seems the "center of focus" on the sensor is shifted to the lower left in that image, so maybe try some test shots with the camera rotated to different orientations. Also, try an image with no filter, here's a thread where the suspected focuser sag ended up being a defective filter:
https://www.cloudyni...age-plane-tilt/

That is a good point.  I just introduced the filter drawer for this imaging session and because I had a collection from my DSLR days, I'm still using my old Canon Clip filters with an EOS to 2 inch filter adapter (In this case an Astronomik L-2).  I'll have to do as you have said and try with and without the filter.



#6 astronautgenius

astronautgenius

    Vostok 1

  • *****
  • Posts: 106
  • Joined: 07 Jul 2015
  • Loc: Los Angeles, CA

Posted 22 October 2020 - 05:40 PM

I'll be interested to hear your results, since I have the same scope, but equipped with a Moonlight focuser and the Hotech flattener. The corner stars for my images aren't as flat as I'd like, but I'd say about 80% of the frame is usable (ASI1600MM-P).



#7 John SC

John SC

    Vendor - JP Products

  • *****
  • Vendors
  • Posts: 143
  • Joined: 20 Apr 2018

Posted 23 October 2020 - 09:22 PM

I have one as well.  The first one went back to Orion because of a focuser issue (my SLR was kinda rocking around), they ended up replacing the whole scope when they could not get it to stop.  As soon as I got it back I took the (now new) focuser off and replaced it with a Moonlite.  No issues with that combination.  I have the Orion small refractor flattener, but have not had time to check that entire combination out.



#8 Rydeen 98

Rydeen 98

    Explorer 1

  • *****
  • topic starter
  • Posts: 70
  • Joined: 06 Feb 2018
  • Loc: New Mexico

Posted 24 October 2020 - 07:54 AM

I tested this out again last night with my 0.8x reducer and it has the same problem though it's a little less noticeable because of the focal reduction.  I'm thinking it has something to do with the ZWO filter drawer though I'll have to remove it to confirm.  Here's a couple of older images with the same gear but no filter drawer and they look great.  I really wanted that filter drawer to work to easily switch between my Ha and UV/IR cut to help in keeping the framing the same but if it's causing problems it has to go.  I'll get another chance to test it check tonight.

 

Andromeda galaxy
 
Eagle Nebula

 



#9 KenR

KenR

    Lift Off

  • -----
  • Posts: 15
  • Joined: 22 Jul 2018

Posted 01 November 2020 - 11:36 AM

I have the same telescope, ZWO filter wheel and ASI1600MM camera. Couple of things I found and fixed:

 

1. My carbon fiber tube had a loose ring on the focuser end. It's a really poor design to hold the weight of the tube and cell with four tiny screws through the carbon fiber. So I use a little epoxy and fixed this connection. https://youtu.be/OCN5rT-sJd0

 

2. The stock focuser sucks. I found it was not collimated well and the rotator was just sloppy. Using a laser collimator I discovered the focuser axis did not align with the center of the cell. It was off my 4mm or so. I replaced the focuser with a Moonlite and I'm very pleased this this! Highly recommended. The alignment looks great now and the Moonlite is solid.

 

3. Even after the items above I still had poor looking stars in the corners although the corners are now pretty closer to the same. Now I started experimenting with all my field flatteners: a) William Optics 0.8x reducer/flattener. Not terrible but still not "acceptable" to me. b) Televue TRF-2008 0.8x reducer/flattener. Little bit better than the William Optics but not much. c) Stellarvue SFF6 flattener only. Still poor in the corners, almost looks like astigmatism. Also, not sure yet but I think I'm seeing some sort of reflection issue. So I'm going to stick with the TRF-2008 for now but am considering trying the Orion flattener you're using.

 

4. I then tested Astrophysics method of spacing the field flatteners. I did this for the William Optics and Stellarvue. They talk about adjusting by a few millimeters but what I found with my setup is I needed an additional 10mm spacing to get the focal points the same between center and the corners! This gives me the flattest field BUT it's still not perfect! https://astro-physic...d-flattener.pdf

 

So now I'm trying to figure out what I think is a reflection issue. I'll post separately on that. I'm also starting to suspect the ZWO filter wheel is causing some of my issue.


  • astronautgenius likes this

#10 astronautgenius

astronautgenius

    Vostok 1

  • *****
  • Posts: 106
  • Joined: 07 Jul 2015
  • Loc: Los Angeles, CA

Posted 02 November 2020 - 02:55 PM

I have the same telescope, ZWO filter wheel and ASI1600MM camera. Couple of things I found and fixed:

 

...

 

Incredibly useful post, thank you. I haven't found a post comparing these flatteners side-by-side on this scope anywhere! Also, that link detailing how to fine tune the spacing is great, never seen that method before.




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