Newbie question... Odd photo effect - what causes it?

[Leebert]

I got myself a 3x Tal barlow and tried some astro-photography with it but the images came out with a bright spot in the middle.

The image looked nice visually. What causes it and is there a way around it?

Many thanks.

http://farm8.staticflickr.com/7017/6588189519_e99330e445.jpg' alt='6588189519_e99330e445.jpg'>

DSC_0010 by MrLeebert, on Flickr

[nightfisher]

can you give details of how you made this image, like what scope and camera

[dtumacde]

What kind of filter are you using? When looking through the lense so you see this glare with your eyes?

[Leebert]

The scope is a Skywatcher Skymax 127 with a Nikon D5000 at prime focus (via the 90 deg).

There was no apparent glare when viewing by eye. I didn't use any filters.

I took a photo without the barlow and that came out okay:

http://farm8.staticflickr.com/7148/6524626703_cbb515ef1f.jpg' alt='6524626703_cbb515ef1f.jpg'>

DSC_0003 by MrLeebert, on Flickr

[Leebert]

Whilst putting all the gear away the other night, I noticed that the base of the Tal barlow is chromed.

Could this cause reflections and therefore the effect that I am seeing in the image?

Cheers,

Lee

[ollypenrice]

Yes, a good lead to follow up. Just try some matt black paint. I have an old TeleVue Pronto which needed reblackening in the back of the tube inside. Now perfect.

Oly

[Cornelius Varley]

It could be an internal reflection from the Barlow, but I would remove the diagonal from the imaging path. This could also be causing problems and is another air/glass surface to degrade the image.

Peter

[nightfisher]

looks like its the barlow:eek: it would do no harm at all to get some matt black paint and carefully conceal any area that could reflect onto the diagonal

[LukeSkywatcher]

Looks like the barlow is to blame. Most barlows do not have a flat end like the one you have.

[Leebert]

I'm surprised that they are made like that but then it didn't affect normal viewing by eye though

I have some matt black blackboard paint so I'll give it a go.

Once we get some clear skies I'll experiment with putting the camera adapter straight on to the OTA and then add things one by one to see what causes it.

[LukeSkywatcher]

The camera is more sensitive to light so it will show up in images while observing with your eyes you will not notice it because the moon is so bright and the eye is not as sensitive.

Sorry the above is just stating the obvious.