Join for FREE
It only takes a minute!
Zeiss - Always on the lookout for something special – Shop now

Welcome to BirdForum.
BirdForum is the net's largest birding community, dedicated to wild birds and birding, and is absolutely FREE! You are most welcome to register for an account, which allows you to take part in lively discussions in the forum, post your pictures in the gallery and more.

Afocal with 35mm compact?

Thread Tools Rate Thread
Old Thursday 8th September 2016, 01:38   #1
Registered User

Join Date: Sep 2016
Location: Woodinville, WA
Posts: 6
Afocal with 35mm compact?

I have a Sony rx1r II full frame compact camera, which produces lovely photos, particularly in low light. It has a very nice Zeiss 35mm lens and 42mp sensor. I'd like to use it for afocal astro and terrestrial photography, but I've read here that because the afocal method places a lot of glass between the sensor and object, the image quality is not great. I'm wondering to what extent using very good glass would overcome that problem or whether it would be smarter to buy a Sony A7 dslr instead and use the prime focus method. The two options I'm thinking of are as follows:

Option 1: Rx1r II camera + 49mm to 48mm step down ring to connect to T mount, which connects to Adaptaview adapter which connects to 2" 21mm televue ethos eyepiece + Explore Scientific CF 80mm telescope. The 21mm eyepiece has a field stop of 36.2mm, so my hope would be that this would minimize vignetting. Cost - around $1900 (I already own the camera).

Option 2: A7 camera (not quite the quality of the Rx1r II) + T mount + CF 80 telescope. Cost - around $2100.

Which of these do you think would produce better images? How much vignetting could I expect with option 1? Other thoughts? Thanks much.
think2100 is offline  
Reply With Quote
Old Thursday 15th September 2016, 09:25   #2
Paul Corfield
Registered User

Join Date: Feb 2005
Location: Corfe Mullen, Dorset, UK
Posts: 3,010
I can't say how much vignetting you would get. Can you get access to a telescope just to try it out? If you don't know anyone with a scope then most shops will allow you to test.

Image quality with either method would be quite similar probably but option 2 is usually slightly better. With option 1 you would need a variety of eyepieces to get a range of magnification. You would also need a good quality 45 glass prism to get the image the right way up and also orientated correctly left to right. An erecting mirror will only get the image the right way up but will be back to front on the left to right orientation. Just putting an eyepiece into the scope will mean the image is upside down for the camera. With option 2 you don't need a prism because the image is already the correct way up when no eyepiece is used.

The eyepiece you mentioned is very expensive. Plenty of eyepieces for a fraction of the cost which are still very good.

If you are using the same scope with either set up then I would try option 1 first and then go to option 2.

Get hold a cheap plossl eyepiece and try it with the camera, no need for a prism when just trying it out for quality. A cheap plossl wont be a million miles away from what you would get with the expensive eyepiece, especially at the low end like the 21mm you mention. The better eyepieces have a better field of view, better coatings etc but the difference for photography is small compared to a big difference when used for visual viewing. Explore Scientific make good eyepieces too, basically copying the Televue design. Baader Hyperions have a good reputation also. A basic plossl eyepiece will let you know if there's any merit in pursuing this method and then you can get a better eyepiece and a prism.

Benefits of option 2 are image quality will be very good, only need one or two teleconverters, start with a 1.4X and that's it. Only thing some people struggle with is manually focusing through the viewfinder. If your eyesight is good then this shouldn't be a problem.

Paul Corfield is offline  
Reply With Quote
Old Wednesday 5th October 2016, 04:20   #3
Registered User

Join Date: Sep 2016
Location: Woodinville, WA
Posts: 6
Thanks, Paul. Decided to sell the rx1r and go with option 2, although I won't be able to get the telescope for several months.
think2100 is offline  
Reply With Quote

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Stepping up from an old prosumer camera: afocal or prime? CalvinFold Micro Four Thirds 4/3 Photography 15 Thursday 2nd October 2014 01:23
Afocal digiscoping with DSLR - help me!! timcoleman106 Camera Settings 5 Monday 21st July 2014 14:21
Afocal: Can it be forced any sharper? lee pseudogrammaton Digiscoping cameras 0 Friday 17th January 2014 05:08
Depth of field in afocal systems looksharp65 Binoculars 38 Tuesday 1st October 2013 23:30
Digiscoping Adapters for Afocal Photography Grundy Digiscoping Adapters 1 Tuesday 5th March 2013 09:26

Fatbirder's Top 1000 Birding Websites

Help support BirdForum

Page generated in 0.16064906 seconds with 17 queries
All times are GMT. The time now is 01:27.