Newbie Sky-watcher 72ed owner questions

[CP30]

Hi,

Sorry for the silly questions but I am trying to find out what the correct back focus should be for a Sky-watcher 72ed, I have searched high and low on the internet for a manual thinking this would tell me.  I have a few CCD's but these have been used for planets using a CPC925, I have got a skyris 618m, ASI224mc, Alatir GPcam and a Alatir GPCAM 2 mono for guiding.

I would like to try my 72ED with a ASI224MC and try some DSO imaging, when I tried to focus with the ASI I could not achieve focus.

1) Do I need a 50mm 2" extension for a DSLR and a 80mm 2" extension tube for a CCD.

2) Do I need a field flattener and a smaller extension tube if the flattener is used?

3) What would be a good CCD for imaging with a 72ed refractor?

Any help or advice would be great

Many thanks

Craig

 

[CP30]

I have emailed Skywatcher Support and I have asked what is the correct distance for back focus for DSLR and CCD, I will update with the reply from Skywatcher.

[Louis D]

Hmmm, I've never tried photography with my 72ED.  I'll have to give it a go sometime to see if I can reach infinity focus without a diagonal or extension tube installed.  You'll definitely want a field flattener.  It has so much field curvature, I rigged up a TSFLAT2 on the front of my 2" diagonal to flatten the visual field.  Without it, it reminds me of using a fast Newt without a coma corrector.

[Alien 13]

As with 99% of scopes of this type you  need a 2 inch extension to get focus with a DSLR  if using a FR/FF you can get focus without any other adapter, not sure about a flattener only though...

Alan

Edited February 21, 2018 by Alien 13

[alexbb]

You will reach focus with the OVL field flattener. The backfocus with that flattener appears to be 55mm - DSLR + T -> EOS adapter + flattener + scope produces a good image during the day, I can't yet confirm with stars, perhaps some day...

I don't know about other flatteners.

[CP30]

Many thanks for all your replys, more things to buy and try.

Craig

 

 

[CP30]

Hi,

Just a quick update on the 72ed, I can get focus using the 2" Diagonal with the Altair GPCAM and the GPCAM2130M, but my ASI224MC and the Skyris 618m cannot focus.

Really please with the scope, here is a quick snap of the moon using a GPCAM130m

[SilverAstro]

And looks like you neatly caught the Lunar X and V being discussed over THERE

Nice one !

[Demonperformer]

Wow! What a result first time out! Congratulations. 

[CP30]

49 minutes ago, Demonperformer said:

Wow! What a result first time out! Congratulations. 

Thanks, I didn't realise how hard this is with a refractor seems so sensitive to focus. 

[CP30]

57 minutes ago, SilverAstro said:

And looks like you neatly caught the Lunar X and V being discussed over THERE

Nice one !

Thanks this is quite hard to do for me, steep learning curve but fun

[CP30]

Sorry last one, this is M42 using the mono gpcam as I cant get my ASI224 to focus.

 

[xs4allan]

Just got the Evostar 72ED and also have an ASI224MC. Did you manage to get it to focus? Would like to know before I buy any extension tubes/FF.