Backfocus - what do I need to order?

[AweSIM]

Hi,

I have a SkyWatcher 200 PDS OTA and a Nikon D90 camera for imaging. A friend of mine is coming to Pakistan from Australia and I'm planning to have him purchase and bring over some gear for me.

I'm ordering a SkyWatcher Coma Corrector for F5 scopesscopes, and perhaps a ZWO ASI294MC ProPro camera as well.

I want to ensure that when he comes, I will have everything I need and not some missing items. In particular, I'm worried about back focus distances and spacers required.

I want to ensure that I be able to use both my D90 and ASI294 MC Pro with the coma corrector. But I'm not sure what spacers I will need.

The coma corrector manual states it requires a back focus distance of 55mm.

The ZWO manual states it has a back focus distance of 6.5mm with the 11mm T2 extender taken off. There are some spacers included in the package but I'm not sure what they are for and if they will fit my setup as I'm not really well versed in the science of thread types.

I don't know what is the back focus distance of D90.

Can you guys please help me identify what adapters and spacers I'll need to ensure that both my D90 and ZWO can be coupled to my scope?

Since we don't have any astronomy shops in Pakistan, and my friends don't come frequently from abroad, I want to avoid the situation where I have the cameras and the coma corrector but can't use it since I don't have the proper spacers or adapters.

Thanks and best regards,

Asim Sohail

Pakistan

[AweSIM]

Any advice from anyone here? 🙂

[wimvb]

Have you checked the ZWO site? 

Assuming the coma corrector has 55 mm backfocus, like this

https://www.firstlightoptics.com/coma-correctors/skywatcher-coma-corrector.html

Just make sure the threads match (M42, M48) 

Edited December 2, 2019 by wimvb

[AweSIM]

On 02/12/2019 at 13:27, wimvb said:

Have you checked the ZWO site? 

Assuming the coma corrector has 55 mm backfocus, like this

https://www.firstlightoptics.com/coma-correctors/skywatcher-coma-corrector.html

Just make sure the threads match (M42, M48) 

Hi! Thanks a lot for that information mate! I had thought that I would've needed to buy extra extension rings or adapters. But you're right, the camera itself comes with all the required accessories. That is impressive. 🙂

[wimvb]

53 minutes ago, AweSIM said:

That is impressive. 🙂

What's even more impressive is that the zwo filter wheel and oag fit in this scheme. No extra adapters needed, just attach one to the other. They seem to have thought this through.