Unable to focus DSLR with powermate on Newtonian

[acarleton]

Hi

i have a astrophotography Newtonian which i picked up the other day (thanks to all for the info and help there) and i was able to focus the DSLR by itself but when i tried to add my teleview 5X powermate to take some close up shots of the moon and jupiter i was unable to focus. The scope comes with an extension for an eyepiece, when i put that in it looked like it was closer to focus. is there anything special i need to do to achieve focus? is it that the distance between the powermate and the DSLR sensor is too big? or do i just need a longer extension?

thanks for the help

Aidan

[rustigsmed]

sounds like you need a long extension tube. you can confirm first by disconnecting the powermate and dslr from the focuser and holding it steady slowly bring it further away from the focuser to see if it will achieve focus (which it sounds like it should).

[Merlin66]

Aidan,
Are you using the Powermate T thread adaptor or just fitting the Camera body to the 1.25" visual section.
To be honest, it shouldn't make much difference - the Powermates are not sensitive to the backfocus distance.

The front lens of the Powermate has to be positioned inside the prime focus of the scope to function - it sounds like this is where the problem may lie.
Have you tried the Powermate with a low power eyepiece - to see if you can reach focus?

[rustigsmed]

this sounds more likely the culprit - good pick up!

[acarleton]

I have a Canon T ring, and a 1.25" adapter which i connect to the powermate, i have connected an eyepiece to the powermate with the extension in and it focuses just fine.

[rustigsmed]

i think it sounds like you are doing everything right so it might be the outfocus.

1 canon t ring
2 1.25" adaptor http://www.bintel.com.au/Eyepieces-and-Barlows/TeleVue-/Barlows-and-Powermates/TeleVue-Power-Mate-br-T-Ring-Adapter/883/productview.aspx
3 Powermate with eyepiece section unscrewed and removed from base part of powermate.
4 focuser.

:question:

[acarleton]

so you think i need to try and get the teleview lens closer to the DSLR sensor? hence the different 1.25" adapter?

[Merlin66]

You don't need more/ less space between the Powermate lens and the CCD.
It could be you're having problems focusing solely due to the dramatic increase (x5) in focal length.
The seeing conditions and careful - I mean CAREFUL precise focusing play a critical part.

[acarleton]

I don't think that is the case because I was able to focus easily with a 10 mm eyepiece which should be more difficult. I will have a play around with it and see if I can sort it out.

[rustigsmed]

it might help if you could take a photo of the powermate connected to your DSLR and post it up :thumbsup:

[Merlin66]

Whooo
A 10mm eyepiece in a x5 Powermate is equivalent to a 2mm eyepiece.
Use this on your 250 Newt and it would give x500 magnification.
Way above usable magnification!

[acarleton]

it seemed to handle the magnification just fine, anyway i have attached a pic of the rig and the optional extension tube. i have tried it with and without the extension although there may be some wiggle room in it that i am yet to utilise.

[Merlin66]

My gut feel tells me the focuser needs to be racked inwards....
(You can buy a T thread adaptor for all the Powermates which significantly reduces the distance to the Camera body - reduces the overhang and can help with balance.)
Where the Powermate is positioned for visual with an eyepiece is where it should be for use with the camera.
Hope this helps.

[rustigsmed]

it looks like the powermate hasn't been unscrewed for camera use?