Asiair and EAA

[LaurenceT]

I've got the idea of tonight trying EAA using a colour planetary camera, asi224mc, and my Asiair taking 10 second subs. The idea is to also use my Seestar and make a comparison of the images. 

I'll be using my WO ZS61ii, it has a field flattener but I have some Explore Scientific extension tubes to get 55mm back focus, the target will be the Crescent Nebula. My question is will I have to do a polar alignment with the Asiair before moving to the target?

Thanks for looking.

[StevieDvd]

The Seestar would calibrate, plate-solve and track - it has no guide camera.  it's also AZ as standard unless you are using it on a wedge. 

Is the other setup in eq mode, if so then best to do PA. The AsiAir will also plate-solve on a goto and track but unless PA is reasonable the tracking will be off.

[LaurenceT]

1 hour ago, StevieDvd said:

The Seestar would calibrate, plate-solve and track - it has no guide camera.  it's also AZ as standard unless you are using it on a wedge. 

Is the other setup in eq mode, if so then best to do PA. The AsiAir will also plate-solve on a goto and track but unless PA is reasonable the tracking will be off.

Thanks for the reply. As it happened I couldn't even get focus using the EAF so I think I was being over optimistic in judging the back focus using the asi224mc instead of my usual asi533mc pro.

I decided to abandon that exercise adopting Homer Simpsons advice "if at first you don't succeed, give up".

Dark nights in the UK are too precious to waste time with some of my dafter ideas so I'll follow a more conventional route and use Sharpcap and my Az GTi for EAA.

[Elp]

The front of camera to sensor distance is different from the 224 compared to the typical camera design of the 533 which has an upstanding nose, it's nearly double at 12.5mm compared to 6.5mm, so you have to account for this difference.

 

[StevieDvd]

I thought the WO ZS61ii needed 67.7mm back focus! So 67.7 - 12.5 =  55.2 deduct the flattener from that to get the correct spacing.

[Elp]

Their flatteners have different specs. My flat 61A is 55mm backfocus distance, so with a 224 I'd need 42.5mm spacing.

Considering how small the sensor is on the 224 I wouldn't even use the flattener, just use the 1.25 inch t adaptor that came with the camera and just push into the visual back, find focus with the focuser.

[LaurenceT]

I use 55mm with a 1mm spacer when using the 533 with my zs61ii and my Askar FMA180 and the stars look good to me. When I was using Stellarmate for EAA I just stuck the 224 into the tube and focused from there, that's much simpler, but I'll take note about the

differences between the 2 cameras regarding back focus.