Off axis guider settings ?

Hi,
stupid question of the week coming........

Kstars asks for the focal length and aperture of the guide camera. I intend to use an oag. Therefore, should I tell it my scope details or camera. ?

(I can almost hear the howls of laughter and derision)

Thanks in advance,

cas

No laughter or howling from me. What "focal length and aperture" does the camera have? You need to enter the scope details and of course the pixel size and amounts of the camera.

Clear skies, Wouter

Hello, thanks for your reply.

The camera is a zwo asi290mm mini. Pixel size is 2.9 microns. There is nothing listed for fl or fr, only its back focus, this is 12.5 mm

Regards,

cas

Hi Cas,

In case of ZWO cameras Ekos gets the pixel info from the camera itself so that's why you don't need to specify that.


Clear skies, Wouter

Great,

thanks very much

Clear skies,

cas

I Read the above - you didn't really get your answer did you. = )

In most cases if wants the guiding scope info. For a guide scope (see their specs) often 50mm and maybe 240mm.
With a OAG you need to enter your primary scopes specs.

When I use a OAG. (which is most of the time). When I'm setting up my 80mm. I enter the focal length for the scope (480mm) in the stellarvue specs. It's aperture is 80mm. (size of the objective).
If I use a field flattener (usually) it's the 480mm x .8 (.08 FF) so that makes it a 384mm aperture 80mm.

When I use my 6" APO it has a .75 FF. So it's a 1216mm scope. AP is 152mm. (6") with the FF it's 1216 x .75 so I enter 912mm FL and 152mm AP. (aperture). size of the primary for light gathering.

If will often ask for pixel size and often the width and height of the guide cameras sensor. Find that in the specs for your camera.

So to answer your question - enter the FL and objective mm of the primary telescope which is (WITH A OAG) also your guide scope.

OAG's are great - I have 3. I like to leave them on each scope as a single unit to swap out. The hardest part is adjusting the depth of the prism into the FOV and not allow it to cast it's shadow on the primary cameras sensor. If you pull it out to far you will get distorted stars on the fringe of the projected image. So better to get in INTO the projection area to get a nice sharp star.... but not so far in that it leaves a shadow on the primary image. A little balance is called for. Then the distance of the guide camera has to be the same distance as the main camera... because they both need to be set to focus at the SAME POINT from the primary scopes focuser. Focus the telescope and primary camera first. Once in focus slide the guide camera up and down (to change distance) while looping the view and find the spacing with the best focus. Lock it down with the set screw(s) and then when you focus the primary image the guide image will also be in focus. Sometimes this will take extra extension tubes to find the proper focus distance. Once set - forget about it!

I never fear asking a dumb question because after someone answers it, I'm not as dumb as before I asked! = )
Couple pics attached if two different scopes with my OAG's.

Rather than ask stupid questions I like to do stupid things... it's called Learning the hard way. = )

Hi Ron,

thanks for your extended answer.

I think(or the way I took it anyway )wvreeven's second sentence was what he was getting at. You've confirmed that for me, thanks

Did you REALLY set up Hyperstar like that ??????

Thanks,

cas

Third, rather

Yeah Ron has a rather lengthy way of confirming what I wrote in that third sentence


Clear skies, Wouter

It's the sofa mount I like Guide corrections by moving a small weight across the cushions.
Perhaps Ron has his house on an equatorial mount. Hope it's a fork mount, a pier flip doesn't bear thinking of.

I'm old and retired - what else do I have to do. Plus after 72F last weekend - there is a snow blizzard thing going on out there today.
(white out)

YES I did that - it's a RASA (similar to a hyperstar). And YES it worked... I ordered the mini guide camera and hoped it would tuck down in behind the EFW.
to my disappointment the focus point had the camera extended "to far out" for my initial concept. (instead of being behind the EFW).

I removed the OAG and went back to an external guide scope for guiding. But the EFW is still installed. = ) The problem was the SPIKE from the hard line of the guide camera.

When people fear posting a dumb question, a vague response will often puzzle them and surely they won't ask again. I wanted to be sure you received a helpful welcoming answer.