Venus via iPhone through mirror telephoto lens

[silv]

That's right. I handheld my iPhone 4s in front of the T2 adapter on the mirror telephoto lens Bower 500mm f/6.3 (https://www.amazon.com/Bower-High-Power-Telephoto-Mirror-SLY50063/dp/B001D3W80S).
The phone has a wonderfully small pixel size of 1.5 um and I was trying whether it's feasible to use it as planetary imaging camera with my mirror lens.
In theory, it should work. There's stacking software even for iPhone planetary videos - like Registraxx called "Keith's Image Stacker".

It's just that this mirror lens has an obstruction in the middle and the iphone apparently can't look around it. (I wonder how my camera manages that, though.)

Would that change if the focal path were longer than the length of the t2-adapter? For example if I attached an additional 2x converter and mounted the iPhone on that - would that help to reduce the obstruction?

Would that happen with a proper Mak telescope, too, when I mount my iPhone on focuser or eye piece?

[Wavytone]

Annette that’s not really an image of Venus - what you have captured is the out-of-focus disk of light from Venus. If you had the iPhone exactly at focus the image (and what you’ll see using your eye) is a bright disk filling the aperture of your scope, not an image of Venus !

To obtain an image you need an eyepiece to produce an afocal beam - exactly as you would see looking into a telescope.

The next issue is that if you can get an eyepiece onto the back of that mirror lens you’re going to find the image of Venus is disappointingly small - the focal length and resolution of that mirror lens are both hopelessly too small and you DO need a rather larger telescope.

Now THIs is a nice picture of Venus https://artsandculture.google.com/asset/the-birth-of-venus/MQEeq50LABEBVg?hl=en&avm=2

[silv]

Thanks. It's out of focus alright of course. And Venus wouldn't be my preferred target with this setup, either.

My question concerns only the obstruction really. Why can't the iPhone look around it like the normal camera does?

[iborg]

Hi

I think it is because you have put the mirror lens too close to the iphone lens.
The iphone is inside the region the mirror lens can generate a complete image.

Perhaps if you move the iphone further away you may get an image.

A suggestion, try using the mirror lens in front of your eye. That may give you an idea for distantances.

Philip

[Wavytone]

The difference between an iPhone and a body that is attached to the lens is that the iPhone has a lens built-in, whereas a DSLR body does not.

You you attached a compact lens to the DSLR body and then used that to peer into the back of the mirror lens it would show exactly the same as the iPhone does.

Regrettably the lens in an iPhone is not removable - if it was, you could indeed use the iPhone sensor as a camera held up to the back of almost any lens and get a decent image - if you had a steady hand.

[astro744]

Exactly what Wavytone said. See http://www.televue.com/engine/TV3b_page.asp?return=Advice&id=85 for more info.

Afocal (digiscoping) = lens or telescope with eyepiece + camera with lens

Prime focus = lens or telescope + camera without lens.

You either need to

1. Get an adaptor or star diagonal to hold an eyepiece and attach it to the lens and then take the photo with your iPhone through the eyepiece or

2. Get a DSLR without lens plus a T-Ring/adapter and connect it direct to the lens.