Adjusting cone error with camera and no view of pole?


Tom Blahovici
 

Hi
How does one adjust cone error if you have no view of the pole and use a camera?
Thanks


Steven Panish
 

Tom - Look up the ConeSharp program, from the SharpCap folks.  Very easy to use, no need to use a specific star.  Adjusters make life easier than shimming.

Steve

On Sat, Aug 28, 2021 at 2:11 PM Tom Blahovici <tom.va2fsq@...> wrote:
Hi
How does one adjust cone error if you have no view of the pole and use a camera?
Thanks


Roland Christen
 

I pick a star near the zenith, slew and center it and hit recal. Then I press "flip scope" on the keypad and the star will be acquired on the opposite side. Any difference in RA direction will be 2 times the Ortho error. Ignore the N-S error since that is a function of the polar misalignment.

Roland



-----Original Message-----
From: Tom Blahovici <tom.va2fsq@...>
To: main@ap-gto.groups.io
Sent: Sat, Aug 28, 2021 1:11 pm
Subject: [ap-gto] Adjusting cone error with camera and no view of pole?

Hi
How does one adjust cone error if you have no view of the pole and use a camera?
Thanks

--
Roland Christen
Astro-Physics


Christopher Erickson
 

First, if you are using APCC-Pro, modelling compensates for cone error so you don't have to shim or adjust anything. It's all taken care of via APCC software in the model.

Second, I prefer adjusting cone error during the day. Too hard for me to go from a dim eyepiece to a flashlight and tools and bolts and shims and back to the dim eyepiece. I pick a distant terrestrial object near straight East or West on the horizon, turn off tracking and flip back and forth over the meridian on that object, taking into consideration the parallax distance as I flip back and forth. And I use the sides of pop cans cut with scissors and a paper punch for shims. I shim between the dovetail bar and the OTA rings or radius blocks.

And make sure your OTA is very carefully collimated before evaluating or adjusting the cone error. No big deal on refractors but a big deal on reflectors.

Cone error, a.k.a. orthogonality a.k.a. perpendicularity, is the relationship between the DEC axis and the optical axis, not the OTA axis.

"My advice is always free and worth every penny!"

-Christopher Erickson
Observatory Engineer
Summit Kinetics
Waikoloa, Hawaii


On Sat, Aug 28, 2021 at 8:11 AM Tom Blahovici <tom.va2fsq@...> wrote:
Hi
How does one adjust cone error if you have no view of the pole and use a camera?
Thanks


Tom Blahovici
 

All of these are good. I do plan on using a model so maybe this is all moot.
Thanks, Tom