144 replies to this topic

[erictheastrojunkie]

I have a thought. I'm writing loud.

By the famous lens equation

 

1/o + 1/i = 1/f, where o = object distance, i = image distance, f = focal length

 

In camera lens system with given focal length of f, the only way to make a focus to specific object distance of o, is to move lens element distance relative to sensor and make change of i. So, amount of allowable lens movement would define minimum focus distance. 

So, say, there is a 50mm prime lens with minimum focal distance of 0.38m ( Sony SEL 50mm F1.8, for example ), image distance at minimum focal distance would be

 

i = of / (o + f), (o is typically negative, so use positive numbers when move to right term for simplicity) = 0.05 * 0.38 / (0.05 + 0.38 ) = 0.044m

 

and o at infinity, i = f = 0.050m, i.e. there should be about 6mm lens movement. 

 

of course this is 'simple lens' equation and camera lens is not but the idea is that lens has to move by in the order of 6mm. 

 

So, what if, we design an adapter that has 6mm longer than E-mount's 18mm backfocus requirement? 

Now, if my thought is correct and simple lens equation applies to the same way to camera lens, the lens will focus at infinity when lens is moved to minimum focal distance because the lens is trying to make image distance to 44mm while actual sensor distance becomes 6mm longer, making 50mm distance which is to focus at infinity. 

Because we as astronomer only need focus at infinity with this adapter, we can repurpose this 6mm movement slack for other purpose like a room for filter (typically 5mm in thickness) or not to have to remove sensor tilt adapter for ASI2600. 

 

I already designed and published the design in Thingyverse https://www.thingive...m/thing:4664592 that connects small ASI cameras to E-mount lens that has nothing but E-mount bayonet and M42/0.75 thread. If above hypothesis is right, we can use this adapter on ASI2600 with E-mount lens at close to minimum focal distance of the lens to the star.

 

Ah.. I really wish I had a manual focusable E-mount lens to prove this. 

 

Eric, have I sent the adapter to you as bundle? I don't remember, if I had, can you try?

Yes, you sent me that adapter, I'll throw it on the 2600mc and see if I can even get the mountain across from my house in focus. As Linwood said, it may be suitable for central focus, but result in some bad astigmatism in the corners, but worth a shot. 

[erictheastrojunkie]

Just tested it out, doesn't come to infinity focus, with the lens racked all the way out to it's past infinity point you can see the distant mountain coming into focus but it never reaches. I believe your equation is fine, but where it breaks down in understanding is if your lens adapter is LESS than the required back focus (ie, if your adapter allowed between 12mm and 18mm back focus distance you can still reach infinity, not between 18mm and 24mm).

Edited by erictheastrojunkie, 21 January 2021 - 07:42 PM.

[Rustler46]

I designed 3D printer model to use Sony E-mount lens 35mm F/1.8 on ASI533MC to take picture of Bernard's loop. FOV is just right.

But found that the lens doesn't allow me to manually focus once it's detached from Alpha camera. So I wasn't be able to actually test it with star, while it seems to be able to reach focus in some distance. 

It could be useful if somebody has a lens that allows manual focus without camera body. So posting here.

 

https://www.thingive...m/thing:4655644

 

If anybody interested in to be a beta tester of it, please print it and give me a feedback if any modification is needed.

Please read note on thingiverse description for printing instruction and tightness.

 

Hope this helps!

Thanks for the informative feedback. I won't waste any more time trying to get my 35mm/1.8 to work with my ZWO camera. Too bad since it is awesome wide open for meteor photography. Here's a low resolution composite image of the Perseids - I call it the "Polar Perseids":

 

 

Composite showing 30 meteors during the 2015 Perseid Meteor Shower; static tripod centered near Polaris - 30 meteors out of 788 15-second exposures, ISO 1600, Sony NEX-5N

 

Best Regards,

Russ

Edited by Rustler46, 23 January 2021 - 02:30 AM.

[Jinux]

Just tested it out, doesn't come to infinity focus, with the lens racked all the way out to it's past infinity point you can see the distant mountain coming into focus but it never reaches. I believe your equation is fine, but where it breaks down in understanding is if your lens adapter is LESS than the required back focus (ie, if your adapter allowed between 12mm and 18mm back focus distance you can still reach infinity, not between 18mm and 24mm).

Now think about my equation and your explanation, I realized that my mistake of disregarding sign for simplicity. 

 

-Jinux

[Jinux]

BTW, I designed an adaptor to attach Sony E-mount lens to ASI2600.

Main idea is to create the same hole pattern as ASI2600 tilt adapter, so that using these hole to attach ASI2600 and tilt adjust if necessary.

Holes have matching threads to fit.

I haven't uploaded it to Thingyverse yet and waiting for Eric's test report to see there is something need to fix.

I'll update this thread after upload.

 

-Jinux

 

ps. I have one test copy of original E-mount to ASI pro camera adapter. This doesn't have protruding origin marker but usable. I'll make a dot with marker.

If anyone wants it, please PM me. It's free and you pay only postage.

Attached Thumbnails

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[AstroCatinfo]

Looking forward on how this adapters progress. Thanks for sharing. I am really excited to use my new ASI294MM with my Sony lenses (Samyang 135mm & Sigma Art 50mm are really promising).

 

Thanks.

[erictheastrojunkie]

Looking forward on how this adapters progress. Thanks for sharing. I am really excited to use my new ASI294MM with my Sony lenses (Samyang 135mm & Sigma Art 50mm are really promising).

 

Thanks.

I'm down in Southern Utah right now trying to escape the clouds, been nothing but cloud covered skies since Jinux sent me the adapter. I was able to do a little bit of imaging last night, I spent a big chunk of the night working through some setup issues with my tablet and eventually had to switch to my ASIAir which was annoying. I tried making some adjustments with the tilt plate to correct some minor (but visible) tilt in the images, I'm using a Voigtlander 50mm f2 APO which seems like a perfect widefield pairing with this camera. The adapter sits perfectly on the camera and the push/pull screws work very well, minor adjustments in those make obvious differences in the image. I really need to be at home where I have access to my computer and software like ccdinspector or PixInsight so I can see how those adjustments are precisely changing the tilt. So for tonight I'm hoping to just get a bunch of imaging done and worry about fine tuning the tilt until I get home. I have the Voigtlander 110mm APO waiting for me when I get home, was hoping to have that for this trip, but of course the package got delayed a day thanks to our awful weather we're having here in the states and was delivered after we left. 

[calypsob]

I designed 3D printer model to use Sony E-mount lens 35mm F/1.8 on ASI533MC to take picture of Bernard's loop. FOV is just right.

But found that the lens doesn't allow me to manually focus once it's detached from Alpha camera. So I wasn't be able to actually test it with star, while it seems to be able to reach focus in some distance. 

It could be useful if somebody has a lens that allows manual focus without camera body. So posting here.

 

https://www.thingive...m/thing:4655644

 

If anybody interested in to be a beta tester of it, please print it and give me a feedback if any modification is needed.

Please read note on thingiverse description for printing instruction and tightness.

 

Hope this helps!

the 533 must have a short flange distance. My 2600 has like 17.5mm  And a Sony FE flange distance is 18mm so theres no way you could make a .5mm adapter

 

Astromechanics does make Ef and Nikon adapters whihc have af and electronic aperture control for astro lenses.  You could probably buy a lens chip and program af yourself.

[calypsob]

it would definitely be worth having some of these machined if you get the tolerances right.

[Linwood]

the 533 must have a short flange distance. My 2600 has like 17.5mm  And a Sony FE flange distance is 18mm so theres no way you could make a .5mm adapter

If the 2600 is like the 6200 there's 5mm in a tilt adapter that just unscrews.  Though 5.5mm is not enough room either in all likelihood.

 

I think the MILC world in general with tiny flange distances has screwed up people's ability to use astro cameras, with an extra nail in the coffin with some of the better lenses having focus-by-wire (i.e. if no power provided to the lens the focus ring does not focus). 

[calypsob]

If the 2600 is like the 6200 there's 5mm in a tilt adapter that just unscrews.  Though 5.5mm is not enough room either in all likelihood.

 

I think the MILC world in general with tiny flange distances has screwed up people's ability to use astro cameras, with an extra nail in the coffin with some of the better lenses having focus-by-wire (i.e. if no power provided to the lens the focus ring does not focus). 

Yea its a double edged sword.  The shorter flange distance of MILC is also what helps the lens formulas gain an edge on resolution. 

 

Im sure the astro cmos manufacturers could design a sensor with minimal backfocus. And a simple 4 axis cnc could produce an adapter to fit a 5mm space, but .5mm no way lol. 

[cucubits]

The 533 is also at 17.5mm with the 11mm spacer on it. Isn't this the same for almost all ASI DSO cameras?

 

[Linwood]

The 533 is also at 17.5mm with the 11mm spacer on it. Isn't this the same for almost all ASI DSO cameras?

 

533.jpg

On the 6200 there's a 5mm tilt adapter screwed on (i.e. bolted on not threaded), which you can remove..  That spacer isn't involved on the 6200.

[erictheastrojunkie]

The adapter Jinux sent me works perfectly as a tilt spacer, you just remove the standard metal one that comes on the 2600mc (or 6200) and use the screws to attach the 3D printed one. I downloaded CCDinspector on my tablet and ran a couple frames through the analysis that I did last night with the Voigtlander 50mm APO on my 2600mc shot at f2.8 (gain 100 and 40 second exposures at a bortle 2 area), here is the FWHM plot:

 

 

and the 3D plot:

 

 

With no adjustments made to the 3D printed tilt adapter you can see there is a slight amount of tilt, that bottom left corner being the primary area that needs to be addressed. Right now I have the plate fully screwed down, I think I'll bring back each pull screw 1 full turn and then adjust each push screw a slight amount to try and dial it in. I'm honestly impressed the tilt is so good with no adjustments being a 3D printed adapter, the overlap I have with my panels will easily cover the tilted areas so I could probably get away with it as is. Tonight I'm going to try shooting a full mosaic at f2 to see how it handles that. 

[erictheastrojunkie]

If the 2600 is like the 6200 there's 5mm in a tilt adapter that just unscrews.  Though 5.5mm is not enough room either in all likelihood.

 

I think the MILC world in general with tiny flange distances has screwed up people's ability to use astro cameras, with an extra nail in the coffin with some of the better lenses having focus-by-wire (i.e. if no power provided to the lens the focus ring does not focus). 

There is plenty of room with the 5mm adapter removed, as I've shown, I have quite a bit of beyond infinity play with the adapter to make tilt adjustments as I need. I agree focus by wire lenses suck and it's part of the reason I've moved from a MILC (Z7) to an astro cam, right now the Voigtlander lenses are a fantastic option for people looking to widefield stuff with MILC lenses on an astro camera, the Voigtlander lenses are fully manual and the APO offerings are a perfect match (no focus by wire, very sharp, mostly free of aberrations like LoCA and Coma, and quite lightweight/small). 

Edited by erictheastrojunkie, 21 February 2021 - 05:44 PM.

[cucubits]

Well shoot. I kept putting off printing an adapter to use a Sigma 30mm prime lens with an ASI533 for some wide field shots and now I started getting excited about this again, until I actually took the lens out. I had completely forgotten that it has electronic focus. Without power, I can spin the ring but nothing happens.

 

Sad. I was looking forward to this and planned not to spend any more $. For sure I'm not buying new lenses or expensive powered adapters.

 

Wondering if there's a way to get the focus working. I'm sure I can find the pinout, maybe if I just power the lens?

Edited by cucubits, 16 March 2021 - 02:08 PM.

[spitonoikokurhs]

hi guys, got a samyang 135mm (sony e), was wondering if there are any updates/ways to connect to a qhy268c?

[galacticinsomnia]

The canon EOS have a straight through adapter, I think ZWO makes them.

But for Sony wouldn't something like this work?
https://www.amazon.c...4340150&sr=8-11

 

Clear Skies

 

Whoops NVM, Sony LENS to M42 or M48 is what you are looking for ??

 

Edited by galacticinsomnia, 15 October 2021 - 06:25 PM.

[Linwood]

It lists itself as 17-31mm (and M42 is pretty small).

 

The Sony E-mount flange distance (distance to sensor) is 18mm.  If I wanted to put that on a camera, like my ZWO, there's a 12.5mm screen-mount to sensor for the camera.  So it starts at 30.5mm.  I can't see how that would focus. 

[galacticinsomnia]

It lists itself as 17-31mm (and M42 is pretty small).

 

The Sony E-mount flange distance (distance to sensor) is 18mm.  If I wanted to put that on a camera, like my ZWO, there's a 12.5mm screen-mount to sensor for the camera.  So it starts at 30.5mm.  I can't see how that would focus. 

I guess I don't know because I don't use Sony, but I believe you can follow a similar process to make your own adapter.
Things I have used to create adapters to and from lenses and cameras.

Inexpensive macro tubes, usually give at least 2 parts of each, a Lens Mount, and A body Mount.  So you can take them apart and usually mockup your own if you don't mind a little dremel work or hand sanding, adding an M42 or M48 Spacer ring and voila, instant adapter.   And parts left over for you to make more for your friends

Spacer Rings, work great in M42 or M48 sizes to use as connectors for your various lenses, or cameras.

I believe my mono cam uses the M42, and I can use that with any of my canon lenses or scopes by making an adapter with various parts.  You really don't need that much.
I've made a few sets of Canon M to M48 so I can use filter slider etc etc. 

Clear Skies !!

[Linwood]

The problem with Sony mirrorless (and really most Mirrorless) is the flange distance.

On DSLR's flange distance was long, e.g. Nikon F mount was 46.5mm.  This gave you plenty of room for an adapter, mount, even filters and electronics even after subtracting say 12.5 for sensor distance on a camera.

 

Nikon's Z (mirrorless) mount dropped it from 46.5 to 16mm.  Take 12.5 off that and you have 3.5, and it's basically not room for anything except just possibly maybe a very thin mount.

 

The Astro industry has a bazillion adapters and such predicated on DSLR's, with their ample (and fairly predictable) distances.  The new mirrorless lenses are making that rather problematic.  Not necessarily impossible, e.g. the 18mm for Sony and 12.5 for ZWO gives room for an adapter.  But not really for electronics, so it has limited utility, only focus-by-gear lenses.

[galacticinsomnia]

The problem with Sony mirrorless (and really most Mirrorless) is the flange distance.

On DSLR's flange distance was long, e.g. Nikon F mount was 46.5mm.  This gave you plenty of room for an adapter, mount, even filters and electronics even after subtracting say 12.5 for sensor distance on a camera.

 

Nikon's Z (mirrorless) mount dropped it from 46.5 to 16mm.  Take 12.5 off that and you have 3.5, and it's basically not room for anything except just possibly maybe a very thin mount.

 

The Astro industry has a bazillion adapters and such predicated on DSLR's, with their ample (and fairly predictable) distances.  The new mirrorless lenses are making that rather problematic.  Not necessarily impossible, e.g. the 18mm for Sony and 12.5 for ZWO gives room for an adapter.  But not really for electronics, so it has limited utility, only focus-by-gear lenses.

I get what you are saying, and Focus by Wire is not something I have ever considered a plus in a camera lens either.. OUCH.  It's hard enough when the Aperture won't move once removed from the camera. Ugh...

This is exactly why I haven't purchased any Canon RF lens, and the only canon M lenses I have are kit lenses because I have L glass that I am not about to sell off and replace, so I use adapters.

That is indeed an issue when working with these new Flange distances and why it is important to consider your use scenarios before purchasing.  I do sympathize and understand what you are trying to do and that has to be incredibly frustrating.

I love the 18mm Flange distance on my Canon M, because I get 26mm extra room to play with if I plan my adapters right.

 

I do believe you should be able to do the right pinouts with the right voltage to power the lens to enable your focusing. 
http://camera-wiki.o...everse_engineer

Also the flange distance without any rings on the asi is 6.5mm  So between 6.5 and 18mm is 11.5, more than enough room to make a mock up adapter

Very cool that you are pursuing and hope to see some kind of positive development.  That would indeed be very cool !

Clear Skies !!

 

[Linwood]

Also the flange distance without any rings on the asi is 6.5mm  So between 6.5 and 18mm is 11.5, more than enough room to make a mock up adapter

I guess that varies by camera, my ASI6200MM is 12.5mm with the tilt adapter removed, and cannot be made smaller.  It's also full frame, a good match for my 400mm Sony lens.  Except of course it won't fit much less the filter drawer it would need.  

[spitonoikokurhs]

The specific lens, Samyang/Rokinon 135mm, is completely manual, both focus and the aperture. Planning to use a belt driven 3d print focuser so that solves the 1st problem

2nd problem, aperture it will be always at f/2 unless something drastic changes, so far it has given me great results with my Sony a7iii

 

3rd and most serious, is making an adapter to work. I wont use any filterwheels or oag, just need to create/design something to properly mount it on a qhy268c camera :/

 

 

 

p.s.Im located in a "semi" remote island, so it is not possible to go to a machinery or to a specialist give the lens and the camera to try design and make it work :/

Edited by spitonoikokurhs, 16 October 2021 - 11:57 AM.

[Jinux]

The specific lens, Samyang/Rokinon 135mm, is completely manual, both focus and the aperture. Planning to use a belt driven 3d print focuser so that solves the 1st problem

2nd problem, aperture it will be always at f/2 unless something drastic changes, so far it has given me great results with my Sony a7iii

 

3rd and most serious, is making an adapter to work. I wont use any filterwheels or oag, just need to create/design something to properly mount it on a qhy268c camera :/

 

 

 

p.s.Im located in a "semi" remote island, so it is not possible to go to a machinery or to a specialist give the lens and the camera to try design and make it work :/

Based on the mechanical drawings from QHY below, making the adapter is doable. 

Backfocus is 14.3mm from the top of the camera where E-mount requires 18mm flange to focus distance. E-mount bayonet requires at least 5mm from the flange but QHY268 has wide opening that can hold this bayonet inside. Attachment to camera is just 6 M3 screws.

I may be able to design 3D model for it but I don't have QHY268 nor lens to test. 

If there is enough interest on this design and someone who has 3D printer is willing to try and feedback to me, I may try design one but it may take some time to actually do it.