imager requirements for plate solving?

[RussellH]

They say a little knowledge is a dangerous thing, and I’m here with about 2 hours research on plate solving.

As I was looking at what it would take to control a mount and camera via my iPad, I came across the ASIAir and the Stellarmate WiFi options. Plate Solving looks like a nice way of finding and aligning things, and both kits seem to offer options to do it.

The question is, does it need to be done via your primary camera imaging, or will it work with the autoguider? If I have my Canon camera as the main imaging camera, and it isn’t interfaced with the control boxes, then I may be reliant on the autoguider image.

The ASIAir in a bundle comes with the ASI120MM mini camera (1280 x 960 pixels), and an F0340 scope which is 30mm x 120mm. I note the ASIAir manual says it requires a FoV from 0.4 degrees to 33 degrees to solve.

So, would that setup be sufficient to allow plate solving from the guide camera, assuming that’s even possible in the software (it may only allow input from the main camera, not sure) or would it not provide sufficient image quality?

If I went the Stellarmate route, I’d have to spec up all the bits and pieces individually anyway, so could pick and choose what works, but I’m still unsure what the requirements apart from FoV are. Is higher resolution imaging better for it to match the index files, or is lower resolution actually better since the image would be chunkier, which may mean the algorithm sees more distinct stars patterns to match?

Thanks. Russell.

[Camelopardalis]

FWIW, you typically plate solve using your imaging camera, as that’s the one where it’s important to get the object in the right place :)

[DavidTrap]

I have plate solved guide-scope images, mainly as a lazy way of measuring the focal length of an unknown guide-scope.

If the centre of the guide-scope FOV doesn't match the centre of your main-scope FOV, you'll be off in your alignment with your imaging camera.

DT

[RussellH]

Yes I had thought about the requirement to have the finder and camera both aligned to the same spot. I guess that’s probably easier said than done however. I’m mainly thinking of a shorter focal length scope initially anyway, so near enough may be good enough. How hard is it to start at something like Sirius to align your guide scope with some test camera images before starting plate solving?

[RussellH]

Looking into guide scope options a bit more, is this a situation where an off axis guider is an advantage, as the guider is sharing the main image? Mind you, the price for an OAG is more than the guide scope I was looking at!

[sil]

more expensive likely to mean better option to take. Astro has very few cheap quick wins. I haven't used guiders yet but I would assume you would benefit from quality optics for better crisper stars for the guider to use plus a flatter field of view likely to be desirable for accurate plate solving. Just going on my experience with plate solving my images some have proved impossible so far and some dead easy to solve.

I would also assume a guider works better on smaller single stars so aligning ota and guiderscope to same point should be less desirable as you usually want a large bright object in your view which would be more difficult for a guider to pinpoint.

I did same assume remember. Happy to learn my assumptions are wrong before I get itchy to spend on gear :)

[RussellH]

Gave up on the OAG. The two thin options I as considering, the ZWO and Orion had too many reports of not being stable. COncerns about backfocus stopped me looking at bigger solutions.