Problem with black spot when trying to take photos

[cthulhugazes]

Hi!

I’m a total noob and I’m a bit baffled, I have a celestron astromaster 114eq and whenever I try and use my iPhone to take photos of the moon there is a black spot that shows up in the middle of the image and when viewing (I usually use the 40mm eyepiece for the full moon). It’s focused but this spot is just visible, I know it’s probably something super simple and I’m just dumb. I usually just hold my phone upto the eyepiece (I’ve since ordered the celestron phone mount which amazon have managed to lose but that’s another story!) is that the issue? I’ve included a few photos to show what I mean.

any help would be super appreciated! 

[Knighty2112]

That’s the secondary mirror that you see there. One of the problems with newtonians is that you will see this obstruction when viewing, especially with certain EP’s etc. As your iphone is held slightly further away than your eye to take the image it becomes more noticeable too.

[Waldemar]

Agreed with Gus. It is the secondary mirror.

The further you are out of focus the more obvious the 'shadow' will be. Your pictures are out of focus, so maybe if you try focussing through your iphone, meaning first get a live view and then focus the telescope to what you see, you may get better results.

[cthulhugazes]

Thanks guys, I’ll give it a go and see if I get better results

[Louis D]

Yes, that's the secondary mirror's shadow.  You might try other slightly shorter focal length eyepieces as well to see if they react better to the moon/telescope/eyepiece/camera combination.

As far as technique goes for afocal photography, first, focus with your glasses you use for distance vision.  That way, the image is focused for infinity focus which makes life easier for the phone's camera.  Second, work the camera in toward the virtual image until you just see the field stop pop into view.  Make sure your camera is centered and level relative to the eyepiece and focused on the image (you may need to tap on the edge of the moon on the phone's screen where contrast is greatest to get best focus), and then snap a series of photos as you think you've achieved best alignment and focus.  Putting your thumb and forefinger between the eyepiece and phone can help steady and level the interface.  Try this all in the daytime focused on a distant object to get the hang of it first.