Beginner needing help...

[Brainstorm]

I tried my hand at astrophotography last week, but unfortunately it seems an impossible task. I have a camera adaptor but it only seems to 'see' two bright objects; The moon and Venus (even these are quite rough quality). Even when I point the camera in the general direction of the stars and leave the shutter open for 30 seconds or more, it just takes a black photo - If I lay the camera on the floor pointing up with a standard lens and use the same settings (800 ISO etc..), it takes thousands of stars. Yet nothing through the telescope.

I'm using an Orion Accutrack SVD Precision motor drive, but this does not seem to track anything (no matter the speed setting), and yes it is polar aligned, with a fresh battery.

I have absolutely no idea what I'm doing wrong.

[eddy]

When you put the camera into the scope, are you focusing it as well? Have you tried altering the focus point?

What camera/scope/adapters are you using?

[Brainstorm]

When you put the camera into the scope, are you focusing it as well? Have you tried altering the focus point?

I'm using venus as the focusing point, as it's the only thing the camera will see. Then moving the scope round to a rough area of where I want to take a photo (I have to guess as I can't see anything in either live view or the viewfinder)..

What camera/scope/adapters are you using?

I'm using a Celestron Barlow T-adaptor - 1 1/4" Model #93640 with Canon T-Ring

I've also tried removing the magnifier which makes the adaptor into a barlow, but then the focuser won't go in far enough to obtain focus.

[malc-c]

I'm not an expert, but this lack of inward travel seems common on quite a few scopes. It might be because a dobsonian is not really intended as an astro-imaging platform, more for visual observing and as such they design the placement of the focal point such that it's not far enough out of the tube to form an image on the sensor when a camera is attached.

[Brainstorm]

I wouldn't use a Dobsonian for imaging either.

[malc-c]

I wouldn't use a Dobsonian for imaging either.

But you stated

I tried my hand at astrophotography last week,

and you signature states a 10" dob.... have I missed something

[Brainstorm]

But you stated

and you signature states a 10" dob.... have I missed something

Yes, it also states "Orion Skyview Deluxe 6" EQ (+ drive)"

I also mentioned in the opening post that the scope was polar aligned. I don't think that's an option with a dobsonian.

[Brainstorm]

I managed to sort the RA motor drive; it turned out a grub screw had worked its way loose.

Any suggestions why I'm getting blank pics - and not seeing anything through the viewfinder/ live view (except the moon and venus)?

It just doesn't seem to make any sense.

[malc-c]

I assume the sensor in the camera is not sensitive enough to detect anything at the short exposures of the frame rate in live view mode.

[Shibby]

Hi Brainstorm,

Have you tried imaging since fixing the RA drive? The stars are very faint compared to Venus, and if you took your images without tracking working then they probably won't show up. But try stretching the levels in the images you took to see if anything is there. Note that a 2x barlow will make the stars 4x (I think) fainter too.

You'll only see the brightest stars through the viewfinder, so I'd suggest trying with one of these first. Also, get/make yourself a bahtinov mask, it's very difficult to get accurate focus otherwise.

[Brainstorm]

Hi Brainstorm,

Have you tried imaging since fixing the RA drive? The stars are very faint compared to Venus, and if you took your images without tracking working then they probably won't show up. But try stretching the levels in the images you took to see if anything is there. Note that a 2x barlow will make the stars 4x (I think) fainter too.

Thanks Lewis, this would certainly explain the problem. I wonder if the manufactured non-barlowed adaptors are the same length as a barlowed adaptor minus the lens, or if they have been shortened to compensate for the focussing issue?

If not, can anyone can reccommend a good (short) T-adaptor that will overcome the focusing issue? there seems to be a lot of unnecessary tubing on the Celestron one I have.

You'll only see the brightest stars through the viewfinder, so I'd suggest trying with one of these first. Also, get/make yourself a bahtinov mask, it's very difficult to get accurate focus otherwise.

Definitely looking at getting a bahtinov mask now too. I looked on ebay, but they seem scope-specific, and none appear to be available for the Orion Skyview Deluxe 6". If anyone knows where I can obtain one for this scope I would love to know.

[Shibby]

Some focusers allow you to unscrew and remove the eyepiece holder entirely, revealing a T-thread, allowing you to then screw the T-ring directly to the focuser. Don't know about the Orion but worth checking...

[Brainstorm]

Some focusers allow you to unscrew and remove the eyepiece holder entirely, revealing a T-thread, allowing you to then screw the T-ring directly to the focuser. Don't know about the Orion but worth checking...

Ironically, the dob sports this, but the Orion / EQ doesn't.

I found an adaptor without the extra tubing on ebay. So I'll wait until that arrives and see how I get on there