AF confirm adapter for DSLR's. Do they work for astro?

[StargeezerTim]

Hi all,

I am getting fed up with using live view on my canon to focus. Spending lots of time moving the 10X box around the screen, eventually finding and focusing on a star, then taking the sub and realising I forgot to return the ISO to a reasonable level.

I have seen these:-

http://www.ebay.co.uk/itm/EMF-AF-confirm-Adapter-T2-T-Telescope-Lens-To-Canon-EOS-EF-mount-5D-III-70D-700D-/321411906251

My question is, do they work and has anyone any experience with them? It apparently beeps and gives a confirmation light when focus is achieved. Sounds like it could save a lot of time.

Thanks, Tim. 

[RichM63]

I use one with a manual Samyang 500mm mirror lens. It works just fine even with this 'sensative' lens, however for 'astro use' so far 'NO'.

Rich...

[Thalestris24]

Hi

I don't think you can rely on autofocus with stars as they are too small. I think you'd be better off with a tablet screen, or better still with a laptop and software with focus aid/tool. 

Louise

[Knight of Clear Skies]

A Bahtinov Mask is another option. They are cheap and take the guessing out of focussing, although you still have to turn up the ISO level to see the pattern.

[RichM63]

Another feature that I recently discovered when trying out odd bits of kit is that if you are using a recognized lens on the camera but have set to manual focusing, keeping the shutter button half pressed will trigger a focus beep and red light response when you actually hit a good focus  point.

Also using the free Magic Lantern software allows the use of 'focus peaking' but you would still be using the LV screen although an in focus object is hilighted rather than a red focus point.

[cathouse42]

Auto focus at night?

Has that EVER worked?

Why not hook the DSLR up to a tablet or laptop and then focus from there.

[Skipper Billy]

Basic Windows tablet screen running the Eos software or APT etc - MUCH easier and much more accurate.

I use a Lynx and its great.

[cathouse42]

Basic Windows tablet screen running the Eos software or APT etc - MUCH easier and much more accurate.

I use a Lynx and its great.

Android would be cheaper.

https://play.google.com/store/apps/details?id=jp.co.canon.ic.eos.eosremote  FREE

Better choice of tablet specs and prices and platform is open, cost of development, free.

[StargeezerTim]

Thanks folks. I have just invested in a Lacerta MGEN to avoid using a laptop or tablet for guiding and it also controls the DSLR. I'll look into a Bahtinov mask... no idea what it is but I'll find out!

Tim. 

[Dave_D]

 I'll look into a Bahtinov mask... no idea what it is but I'll find out!

Tim. 

this is a bahtinov mask.

plonk it on the end of your scope and point at a bright star. when the star looks like this

you're focused. takes seconds. (that's vega btw)

[StargeezerTim]

Thanks Proto,

Do you have to focus on a bright star, then go to you imaging target? Or is there always a star bright enough to use it with. I ask because I usually confirm I am looking at the imaging target with an eyepiece, which would of course, [removed word] the focus up. Unless there is another way to do it or I am missing something?

Tim. 

[cathouse42]

I find it strange they put AF confirm connections onto a T-adapter, unless you have camera lenses with T-adapters.

Seems a waste of money to me.

What you are probably better of is using a micro focuser, that should make fine focusing easier since once you get it in the ball park area you just twiddle it finely.

Once you get focus you shouldn't have to change it unless you have a habit of removing your camera often during the night.

[lensman57]

I find it strange they put AF confirm connections onto a T-adapter, unless you have camera lenses with T-adapters.

Seems a waste of money to me.

What you are probably better of is using a micro focuser, that should make fine focusing easier since once you get it in the ball park area you just twiddle it finely.

Once you get focus you shouldn't have to change it unless you have a habit of removing your camera often during the night.

This is a very good point. I can only think that since a lot of these adapters were or are based on the auto extension tubes they have just carried the contacts over . Personally I find their existence rather pointless.

A.G

[Stub Mandrel]

I think they work by fooling the camera into thinking the manual focus lens is focused, so you don't get warning messages or stopped from taking a picture when in non-manual modes.

[Knight of Clear Skies]

Thanks Proto,

Do you have to focus on a bright star, then go to you imaging target? Or is there always a star bright enough to use it with. I ask because I usually confirm I am looking at the imaging target with an eyepiece, which would of course, [removed word] the focus up. Unless there is another way to do it or I am missing something?

Tim. 

You'll need to find a fairly bright star to focus on. Ideally this will be at a similar altitude to your target as the atmosphere does affect focussing very slightly. To check you're on target you could try a quick framing sub at very high ISO.

Further to Dave_D's post above here's a nice guide to using Bahtinov masks, showing what the diffraction pattern looks like both in and out of focus. You could either buy one or make it yourself out of cardboard, there are various templates online for printing.

[cathouse42]

For Autofocus most are based on Phase detection I believe, contrast based is too slow.

AF generally sucks with night scenes, never mind astronomy lol.

You will also have to keep in mind the AF points on the camera, very hard to see these in night, you may need to shine a red torch into the objective to see the HUD (viewfinder) cross hairs on the camera since you are not using the live view.

Generally once you have infinity focused you are set and should not have to change it at all, unless you are messing about with your camera all night (why?).

http://www.digitalcameraworld.com/2013/12/06/how-live-view-autofocus-works-what-your-cameras-manual-doesnt-tell-you/2/

Cambridge in colour website is a great source of technical photographic information.

http://www.cambridgeincolour.com/tutorials/night-photography.htm

[RichM63]

That Cambridge site is indeed interesting and informative. Thanks for the link.

My use of AF confirm adapter is when using either and ST80 telescope of a fully manual Samyang mirror as long lenses for daytime Photography. These are evidently fixed aperture at f5 and f6.3, but the programable AF adapters also allow programing to include all whole apertures and thus trick the camera into 'thinking' that I'm at f11 at ISO 800 and thus give me a sensible shutter speed when in AV mode.

With an unchipped adapter the camera does not think that there is a lens attached at all, so only f00 wide open is available, which is not very handy if looking for different shutter speeds. (daytime use only).

Also it makes focusing slightly more possible.

[cathouse42]

That Cambridge site is indeed interesting and informative. Thanks for the link.

My use of AF confirm adapter is when using either and ST80 telescope of a fully manual Samyang mirror as long lenses for daytime Photography. These are evidently fixed aperture at f5 and f6.3, but the programable AF adapters also allow programing to include all whole apertures and thus trick the camera into 'thinking' that I'm at f11 at ISO 800 and thus give me a sensible shutter speed when in AV mode.

With an unchipped adapter the camera does not think that there is a lens attached at all, so only f00 wide open is available, which is not very handy if looking for different shutter speeds. (daytime use only).

Also it makes focusing slightly more possible.

I don't see how having the camera set your shutter speed is going to help astrophotography, I have never seen anybody use AV mode for astrophotography.

Will be interesting to see the results.

My DSLR runs at f00 with no AF confirm and I get space pictures fine.

When the DSLR is on the Telescope as a lens, the focuser has to move, I don't see how auto focus is going to help here. It is not physically connected for focusing the telescope.

I also didn't know they made Samyang lenses in T-mount fittings. They come in Canon EF or Nikon fittings as far as I knew and these work fine without any AF confirm adapters.

[Alien 13]

The use of these chipped adaptors for astro is very limited maybe to lunar shots I use mine all the time for daytime photography with my scope acting as a telephoto lens but they are not as good as the live view image if you want perfect focus.

I do feel that the camera screen liveview at x10 gets better focus than any other method be it software or bat mask especially if using less than perfect optics i.e. older camera lenses.

Alan

[brendant]

Lots of comments on this post but how many have ever used one first hand rather than posting dismissive comments. In fact they are extremely useful and make focusing very accurate, and especially useful for beginners, just place a bright star on the central focusing point and move focuser until it beeps,highly recommended..

Sent from my Nexus 7 using Tapatalk

[cathouse42]

Lots of comments on this post but how many have ever used one first hand rather than posting dismissive comments. In fact they are extremely useful and make focusing very accurate, and especially useful for beginners, just place a bright star on the central focusing point and move focuser until it beeps,highly recommended.. Sent from my Nexus 7 using Tapatalk

Yes I've tried using auto focus with a bright star, even with AF confirm on a PROPER lens its better to use manual. I don't use AF for a reason.Astrophotography isn't point n shoot

If the screen is too small, use a larger one.

If you cannot master using live view for a simple focus, well, astrophotography is going to get a lot more "demanding" later.

It is not like you have to manually focus 100 times a night. Where is the difficulty in setting the focus ring? Sounds like somebody is impatient.

If you cannot focus a lens, photography is not for you. If you do not like photography, well, astrophotography isn't for you either.  Why pump money and time into something when a focus ring puts you off photography?

I recommend sticking to Afocal photography with an iPhone in this case.

[lensman57]

Hi all,

I am getting fed up with using live view on my canon to focus. Spending lots of time moving the 10X box around the screen, eventually finding and focusing on a star, then taking the sub and realising I forgot to return the ISO to a reasonable level.

I have seen these:-

http://www.ebay.co.uk/itm/EMF-AF-confirm-Adapter-T2-T-Telescope-Lens-To-Canon-EOS-EF-mount-5D-III-70D-700D-/321411906251

My question is, do they work and has anyone any experience with them? It apparently beeps and gives a confirmation light when focus is achieved. Sounds like it could save a lot of time.

Thanks, Tim. 

Hi Tim,

Someone has to say it so here it goes. With all due respect if you are going to succeeded in astro imaging then I am afraid that even a Bahtinov mask is of little use. The most reliable and accurate system is the use of a capture software with FWHM. The software constantly measures the width of the star using the image that is displayed via live image and the numbers will tell you when you have reached focus. I use APT which is free in evaluation and the full version is about £12.00 a bargain as far as AP software is concerned. During a long imaging session as temp drops the focus point changes with FWHM all you have to do is run the routine for a few seconds on a star and you'd know if all has been in vain. Manual or even live view assisted focusing using the camera LCD or even a laptop is a total waste of time for critical focusing and the sooner you learn to use the proper focusing routines the better. I use Bahtinov from time to time for visual and here it is fine but have never used it for imaging.

A.G

[StargeezerTim]

OK... thanks all for your comments and views. Some of you have been constructive and informative, others have not, but I guess that is the nature of this way of communicating. 

The message I get is that these AF chips can work but that there are other ways to achieve focus more reliably and accurately. 

Thanks, Tim...