Need help figuring out focal length for Stowaway and AP130EDFGT / Field Flattener and more for inputting into ASIAir Pro


Denice Woody
 
Edited

I am running into problems figuring out the focal length to use with my new ZWO ASIAir Pro and ZWO ASI071 MC Pro camera and AP Stowaway.  I have tried inputting 0 to have the ASIAir Pro calculate it but it comes up with 648 or 649, and I'm not sure it takes into account the field flattener (or the Precise Parts Adapter).  I haven't used the Pro with the AP130 Gran Turismo yet since I'm having so much trouble.  And I have tried uploading an image from the first night where things worked to Astrometry.net to calculate but it's going on 12 hrs processing/queued!  Unfortunately I didn't write the focal length down for reference later that first night.  So my plate solves are a crap shoot and I get told my FOV is  ? x ? and outside the range and plate solve fails.   I have posted questions on the ZWO Facebook group and on the Celestron AVX group and still no clear answers.  

Any help in figuring this out would be much appreciated.  Here are the two scenarios I would be using per George at Astro-Physics.

Per George:

          The adapter setups below are shown following the light path from left to right (scope on the left & camera to the right).

 

                      130 EDFGT with 67PF562 field flattener: 
 

                                67PF562 + A1262 CCD Adapter + A3503-A (Extension) + ADA27-42 + new camera (ASI071MC Pro)

 

                      Stowaway with 92FF field flattener:

                                92FF + Precise Parts Adapter + ADA27-42 + new camera (ASI071MC Pro)
                                            
                              The below screenshot is the info on the Precise Parts Adapter: on my Stowaway:


Kenneth Tan
 

Put the focal length that is stated in the specs of the scope. Then shoot and do a plate solve in asi air. It will then update the correct focal length into the field after sync to mount

On Wed, 26 May 2021 at 23:57, Denice Woody <astrowoody@...> wrote:

[Edited Message Follows]

I am running into problems figuring out the focal length to use with my new ZWO ASIAir Pro and ZWO ASI071 MC Pro camera and AP Stowaway.  I have tried inputting 0 to have the ASIAir Pro calculate it but it comes up with 648 or 649, and I'm not sure it takes into account the field flattener (or the Precise Parts Adapter).  I haven't used the Pro with the AP130 Gran Turismo yet since I'm having so much trouble.  And I have tried uploading an image from the first night where things worked to Astrometry.net to calculate but it's going on 12 hrs processing/queued!  Unfortunately I didn't write the focal length down for reference later that first night.  So my plate solves are a crap shoot and I get told my FOV is  ? x ? and outside the range and plate solve fails.   I have posted questions on the ZWO Facebook group and on the Celestron AVX group and still no clear answers.  

Any help in figuring this out would be much appreciated.  Here are the two scenarios I would be using per George at Astro-Physics.

Per George:

          The adapter setups below are shown following the light path from left to right (scope on the left & camera to the right).

 

                      130 EDFGT with 67PF562 field flattener: 
 

                                67PF562 + A1262 CCD Adapter + A3503-A (Extension) + ADA27-42 + new camera (ASI1071MC Pro)

 

                      Stowaway with 92FF field flattener:

                                92FF + Precise Parts Adapter + ADA27-42 + new camera (ASI1071MC Pro)
                                            
                              The below screenshot is the info on the Precise Parts Adapter: on my Stowaway:


M Hambrick
 

If you have MaxIm DL you can also use PinPoint Astrometry to do your plate solve. You can use it with the GSC-1.1 catalog which can be downloaded free. 

You will need to enter the approximate RA and Dec at the center of the image and an image scale. The first time I used it to solve an image from my Stowaway I had entered the incorrect image scale, and it solved it very quickly anyway. When I noticed that PinPoint kept coming back with a different image scale on my Stowaway images, I realized that I had calculated the original image scale using the wrong focal length. I was using the native focal length of 612 mm, but since I have the 92FF flattener in my imaging train, I should have been using a focal length of 644 mm per the 92FF specifications.

Mike


Kevin Cook
 

Denice - Exactly what Kenneth said.  Start with the nominal focal length for your scope, shoot an image and let the ASIAIR software plate solve that image, and that will tell you the actual focal length.  In my case with an older AP130EDFS, the nominal focal length for this f/6 scope is 780mm but the actual focal length from plate solving is 834mm (with no flatteners or other elements added into the optical path).  Kevin Cook


On Wed, May 26, 2021 at 8:44 AM Denice Woody <astrowoody@...> wrote:

[Edited Message Follows]

I am running into problems figuring out the focal length to use with my new ZWO ASIAir Pro and ZWO ASI071 MC Pro camera and AP Stowaway.  I have tried inputting 0 to have the ASIAir Pro calculate it but it comes up with 648 or 649, and I'm not sure it takes into account the field flattener (or the Precise Parts Adapter).  I haven't used the Pro with the AP130 Gran Turismo yet since I'm having so much trouble.  And I have tried uploading an image from the first night where things worked to Astrometry.net to calculate but it's going on 12 hrs processing/queued!  Unfortunately I didn't write the focal length down for reference later that first night.  So my plate solves are a crap shoot and I get told my FOV is  ? x ? and outside the range and plate solve fails.   I have posted questions on the ZWO Facebook group and on the Celestron AVX group and still no clear answers.  

Any help in figuring this out would be much appreciated.  Here are the two scenarios I would be using per George at Astro-Physics.

Per George:

          The adapter setups below are shown following the light path from left to right (scope on the left & camera to the right).

 

                      130 EDFGT with 67PF562 field flattener: 
 

                                67PF562 + A1262 CCD Adapter + A3503-A (Extension) + ADA27-42 + new camera (ASI071MC Pro)

 

                      Stowaway with 92FF field flattener:

                                92FF + Precise Parts Adapter + ADA27-42 + new camera (ASI071MC Pro)
                                            
                              The below screenshot is the info on the Precise Parts Adapter: on my Stowaway:


Lee Decovnick
 

Denice, 

As Kenneth and Kevin noted, I used the ASIAIR Pro plate solve  using two different ASI cameras on the same scope, an SV115 Triplet APO. Stellarvue's spec was 800mm, but the with the ASI2600 MC is came it at 803mm and with the AS294MC 799 mm. YMMV  It's interesting, after two hours of shooting, and the scope finally reaching an ambient temperature, the the 803mm focal length changed to 801mm. 

I love the AAP polar alignment, I'm running 300 second subs unguided with wonderful pinpont stars....but getting my Mach1 to dead on on both axis takes about 15 minutes and 3 iterations of the PA program. That said,  the AAP guiding still leaves a lot to be desired.. ;-)

Lee