1000mm Lens Question

[David Mitchell]

Hi all,

Sorry I haven't been on here that much, been very busy with work at the moment, I am however looking for a 1000mm lens for something I want to try out. I could just use a 1 dioptre lens to make this, which would work fine as a LF lens, I am however thinking about something that I don't have to build. I am currently a bit stuck with making a rear standard which holds a 5x4 holder correctly which is the issue.

I am thinking about perhaps getting a 500mm mirror lens and just bolt a teleconvertor onto it, they seem easy to get in a M44 mount which I already have a teleconverter for. The issue being is that the negative would be very small although might be ok if using film.

I guess my options for something I am trying out is either:

35mm film using an m44 mirror lens
LF using paper negative and custom lens

I don't think my speed graphic can quite handle such a long focal length - I do have a T mount adaptor so I could actually get a telescope for this lol

Is there anywhere I can get a basic rear standard for a 5x4 holder?

 

[Hamish Gill]

What's the effective equiv to 35mm focal length you are aiming for... That will certainly help answer the question!

Assuming 1000mm, what sort of light gathering power do you need?

Mirror lenses will certainly provide an inexpensive entry. But you might also want to consider mounting a spotting scope. The problem with both these options is the relatively small apertures

 

[David Mitchell]

I won't be using a digital camera for this, I will be doing some solar photography so a small aperture isn't an issue as I will probably also be using welding glass as a filter as well.


I could use a telescope and attach a camera onto it - will have a look around for some telescope mounting kits as well. 1000mm was chosen as this seems to be the correct sort of length needed to photograph the sun (usually tested out on the moon as its the same size in the sky).

I should be able to simply use a 35mm film camera as I can scan the image in and convert it, whereas if I did use a paper negative it would be a bit harder and I wouldn't know the exact ISO of the paper for the correct exposure.

 

[Hamish Gill]

What's your budget?
If you are serious, an astro telescope, a sun filter, a t-mount adapter to mount it to an slr would be the conventional method ... Have a look a Meade scopes, we used to sell them at the shop and only had positive feedback!
Why not use your digital slr? It strikes me as the obvious choice...

 

[Paul Lange]

Can't help with the lens but have you seen Thousands Oaks Solar Filters?

 

[David Mitchell]

I think I will use my NEX on this then, it has the M44 adaptor on it so I can add in the 2x tele convertor, will have a look at those solar filters. I know that you can simply get some of the solar film in A4 sheets.

My largest current lens is a 300mm Tair lens so with the crop factor of 1.5 and a 2x tele convertor that brings it to a 900mm equivilent which might be good to try out on the moon.

I guess using a 500mm mirror lens with the 2x tele and NEX crop factor I should get some decent magnification - at last, something good about having a crop sensor!

I could always go with a telescope though, just seen an 8" Dobsonian parabolic telescope which has a 1,200mm focal length so that would be awesome with a crop sensor camera. There seem to also be a few Meade telescopes that aren't too expensive which offer around 1000mm focal length which should get me into the usable range.