Field of view for plate solving

[rpsutton]

Hi,

I've looked around in the forum here and have found some posts that seem to deal with my question, but I'm still confused. I am trying to learn about plate solving for both polar alignment and GOTO alignment. My main imaging scope is an Edge HD 8 inch with the .7 reducer which yields a focal length of approx 1422mm and I image with either the asi294mc or the asi385mc. I have a 10x50 finder scope with removable ep that has a focal length of 240mm and was going to outfit it with an asi290mini.According to astronomy tools, that will yield a fov of 1.34° x 0.76°. Is that wide enough to use for plate solving for both polar and GOTO?

Thanks in advance for the help -

RP

[admin]

Hi,

the field-of-view with your finder scope and either the 294 the 385 camera should be fine for polar alignment. You should also be able to use that for plate solving if you wanted, but there is a drawback to that… Unless you carefully lineup the finder scope with the main telescope then you will be plate solving and adjusting to put the target in the centre of the finder rather than in the centre of the main scope!

The field-of-view for the main telescope and camera will be smaller – about 0.75×0.5°. This will probably be too small for polar alignment, but you may be able to get plate solving to work if you install enough index files for your plate solving engine. With a small field-of-view like that the index files needed become very large and the processing time can become longer. You can also end up sometimes hitting an area of the sky where there simply aren't enough stars.

Cheers, Robin

[rpsutton]

Hi Robin,

Thank you for replying. I did realize that about plate solving for my main imaging scope. The finder and the main scope are very well aligned using crosshairs - Will it be good enough? I will try and let you know!

thanks again,

patrick

[admin]

Hi Patrick,

yes, if you've gone to the trouble of aligning the finder scope then you should get pretty good results – if you find that everything is slightly off centre then maybe move to plate solving using the main scope, or tweak the alignment.

Cheers, Robin

[rac19]

The recently introduced "multiple reticules" can be used to finely calibrate finder/guide scope to the OTA, having previously achieved a basic physical alignment of course.