Help Needed

[Fraser32 (Fraser)]

Hi guys,

I finally got around to purchasing a motor drive for my scope and my T-Ring for my 5D came today in the mail.

I attempted to take a few shots of jupiter and mars but didnt even get close to anything in focus!

I am hoping it is something simple but have no clue where to start fault finding. I have included some photos of my set up and a couple of my failed shots. any help would be greatly appreciated.

ALSO here is the link for the T adapter i bought, I have a feeling I was supposed to purchase something else??

http://www.ebay.com.au/itm/Camera-Le...IAAOSwhRxXLInx

[wasyoungonce (Brendan)]

Hi Frazer, welcome to IIS.

Lets explain it all first. What happens is the eyepieces magnify the image light at the focus point from the mirrors (primary and secondary). This focus point is a point inside the tube. The problem you have is that your "T" adaptor and camera "backfocus" add length to the image train, thus your image you are trying to focus on is too far fwd. You cannot reach focus as the focuser will not rack in enough.

The "T" adaptor adds probably around 15mm and the camera image plane is 55mm (most canons are this) from the front surface of the lens adaptor. You will notice the camera has a "Ø" on it at the top. This is camera sensor image plane inside the camera.

Ok how to fix this....you need to move the primary mirror forward or use a low profile focuser. It's preferred to move the primary, see here, around 50mm. There are other ways but this is the preferred.

This means taking out the primary, re-drilling the tube (nice and square) so the primary is now re-mounted 50mm fwd up the tube. All this brings the primary mirror image plane 50mm fwd "volia" you can achieve focus! However, when using this with an eyepiece, you may need/will need an extension adaptor of 50mm to achieve eyepiece focus from now on.

Be careful doing all this, do not touch the mirror surface do not get dust on it etc etc. Good luck and get back if any questions.

[wasyoungonce (Brendan)]

Sorry...55mm is most likely the distance added with the "T" adaptor. The canon backfocus is 44mm.

[Fraser32 (Fraser)]

Thanks for your help!I dont know if i would be confident to move the mirror in the tube seems like it would be tricky to get right. Perhaps a low profile focuser would be better? Why do you say this would be less preffered?

[glend (Glen)]

Honestly i would not tamper with modifying that scope with your level of experience. It is not an imaging capable scope (without significant work).
There is one possibility, you could try using a camera with a very short back focus requirement, that lets out most all dslrs. A ZWO ASI camera could work in and it will fit into a focuser tube with adaptor that comes with it. Think of it as a webcam, it comes with software that enables video capture or stills. You don't need an expensive one, the bottom of their range would do the job to get you started.

[Rex]

Hi Fraser, mate I tend to agree with glen, however if your just trying out astro-photography and you are on a very limited budget try a Prostar LP-Guide camera. They operate very similarly to the zwo ones but much cheaper. A link below, to where I bought mine.
http://www.myastroshop.com.au/produc...sp?id=MAS-025B

And a link to a thread on this site wear I have been discussing this camera with another IIS member. And a test image I did. They are very noisy but with calibration the result is acceptable.

http://www.iceinspace.com.au/forum/s...d.php?t=146329

[wasyoungonce (Brendan)]

Originally Posted by Fraser32

Thanks for your help!I dont know if i would be confident to move the mirror in the tube seems like it would be tricky to get right. Perhaps a low profile focuser would be better? Why do you say this would be less preffered?

Its expensive for a low profile focuser and more than likely it will not move the image plane in enough....just guessing.

IMHO a DSLR is a great imaging tool...but as others have said....this is a delicate job. Do you know of a local astro shop or club?

[raymo]

This is all a bit strange. As far as I know, all modern Saxon Newts are
rebadged Synta[Skywatcher] scopes, and all Skywatcher Newts have
sufficient back focus for DSLR prime focus photography. Is your Newt
an old model?
raymo

[croweater (Richard)]

I shifted my mirror up the tube of my Parks 8" to get focus to my pentax film slr years ago and all I did was mount the camera . Then I unbolted my mirror cell andcarefully slid it up the tube a bit at a time until I could get focus in the camera. This gave a good idea of the distance needed to shift the mirror without too much measuring. Then carefully drilled holes at the new position (just measure same distance up from each original hole) and remounted the cell. Worked fine. Cheers Richard

[glend (Glen)]

Being in Brisbane he could drop round to the astroshop in Mt Gravatt and they should be able to help him.

[Rodmac (Rod)]

Originally Posted by glend

Being in Brisbane he could drop round to the astroshop in Mt Gravatt and they should be able to help him.

Pete at astropetes in Mount Gravatt (on Logan road) stays open late on Friday evenings and has telescopes out for viewing and normally a few other knowledgeable people set up and are willing to help out as well. You could even take your scope and camera down and they would be able to look at it and advise. I'm new to astronomy and astrophotography and they have been great at helping me out. They also have a star party on on Saturday night and you'd be more than welcome to come along and set up or just look and talk to people.
Cheers
Rod

[jsmoraes (Jorge)]

You can use a barlow mode 1.5x. It will solve your problem of backfocus. You loose some FOV, but you can image planetary and DSOs.
With planets and Moon barlows is very important to see details. So, you loose nothing.