DSLR, 6.3 Reducer, ZWO filter drawer and back focus on CPC925

[AstroGS]

Good evening to all.

Today was the 2nd weekend trying to figure things out.

I want to add a ZWO filter drawer for 2” filters to be used with my astromodded Canon 450d.

The equipment consists of:

CPC925 GPS

Antares Reducer 6.3

Celestron T-Adapter SCT (https://www.firstlightoptics.com/adapters/celestron-sct-t-adapter.html)

T-Ring: Baader Ultra Short Canon EOS T-Ring (https://www.firstlightoptics.com/adapters/baader-ultra-short-canon-eos-t-ring.html)

ZWO filter drawer 2” (M42/M48): https://www.firstlightoptics.com/zwo-accessories/zwo-2-filter-drawer-m42-m48.html

 

The issues I’m having are 2:

1) When trying to connect The T-Adapter with the ZWO filter drawer it does not lock in position. I’m probably missing an additional adapter here but, not sure what.

2) The backfocus should be 105mm between reducer and sensor. I cannot seem to get this right either. Before start buying more adapters, I wanted to check with you what exactly adapters would I need to get it right and use the zwo filter drawer?

 

many thanks in advance

George

[michael8554]

1) When trying to connect The T-Adapter with the ZWO filter drawer it does not lock in position

You'll have to be more specific. The T adapter has a T2 female thread into which the T2 male of the filter drawer screws. 

When you've screwed those together tightly they're locked.

2) you have 44mm DSLR + 2mm T2 Adapter + 21mm T2 Filter Drawer  = 67mm

So you need 105mm - 67mm = 38mm of spacers.

I'd try 40mm which is 2mm too much, and check the star shapes in the corners of images.

With a "normal" 11mm T2 adapter for the DSLR you'd need 29mm, so a 30mm spacer would only be 1mm out.

Michael

 

[AstroGS]

18 hours ago, michael8554 said:

1) When trying to connect The T-Adapter with the ZWO filter drawer it does not lock in position

You'll have to be more specific. The T adapter has a T2 female thread into which the T2 male of the filter drawer screws. 

When you've screwed those together tightly they're locked.

2) you have 44mm DSLR + 2mm T2 Adapter + 21mm T2 Filter Drawer  = 67mm

So you need 105mm - 67mm = 38mm of spacers.

I'd try 40mm which is 2mm too much, and check the star shapes in the corners of images.

With a "normal" 11mm T2 adapter for the DSLR you'd need 29mm, so a 30mm spacer would only be 1mm out.

Michael

 

Thanks for your input - i will try and get a video to show what i mean as it seems i did not explain it properly. Regarding your 2nd point i bought today a Baader VariLock 46 Lockable T-2 Extension Tube to sort this issue. I hope it works this time 🙂