sky watcher esprit 120ed Connecting ASI2600mc to Reducer/Flattener and Esprit 120ED and working out backfocus

[dylannaran7]

Hi guys, 

Hope I'm posting this in the correct area. 

I'm looking for some help with getting the correct back focus/connection for my new Esprit 120ed and ASI2600mc. 

Just as a general background on my equipment:

• Telescope - Esprit 120ed
• Camera - ASI2600mc pro
• Mount - EQ6-R pro
• Guidescope 60mm 
• Guide camera - ASI120mm mini
• ASI air plus 
• Filters: Antlia ALP-T and Optolong L-Pro 
• ZWO EAF
• ZWO Filter Drawer 
• SW 0.77x Reducer for Esprit 120ed 

So I haven't had the chance to try connect everything up but i was wanting to know what i exactly need in the train to get my set up ready to go and was wondering if anyone had any advice? 

My thought is: 

ASI2600mc (17.5mm)  -> ZWO m42 filter drawer (21mm) -> M48-M42 adapter (0mm) -> T2-M48 adapter (16.5mm) -> M48-M42 adapter (0mm) -> 0.77x esprit 120ed reducer -> Esprit 120ed 

Does this seem correct? is there anything else i need to purchase to do this?

Cheers

Dylan

[teoria_del_big_bang]

I do not have this setup but from what I can see you are correct.

Only thing I would add is that with a filter the back-focus will increase by 1/3 thickness of filters used. This does not sound a lot (if filters 3 mm thick the need to add 1 mm) but you will see distorted stars in corners if you do not account for this. Most filters are between 2 and 3 mm thick. So you may need some thin shims available from FLO and other good astro suppliers just to tune to the exactback-focus.

Steve

[dylannaran7]

Thank you for getting back. Awesome that makes sense. I have just ordered a 1mm adapter. Hopefully once it all arrives i can get it all out together and finally start using it once the clouds clear up haha

 

thank you