Ed Greding Loc: Texas

I have a Nikon DSLR 5100, and want to use it to take photos through a Cassegrian telescope by attaching a short extender to the opening in the back, then attaching the other end of the extender to the camera, using a T-ring. No eyepiece would be used (although one could). The picture would be taken straight through the telescope, focusing by using the LCD. The problem is that the camera evidently will not recognize the telescope as being a lens. The mode is on manual (M). A message comes onto the LCD saying "No lens", and nothing happens when I press the shutter release or use a remote to avoid shake. I'm pretty new to digital photography, but it seems clear that I'm either doing something incorrectly, or not doing what I need to do with the camera. Any advice will be appreciated.

Rongnongno Loc: FL

Ask this is the Astronomical Photography forum. Folks there are informed, much more that the the general UHH 'population'.

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

You need to have both exposure and focusing set to manual on the camera. If you don't have them both set to manual, the camera will electronically look to the lens for data, and not getting any, will report "no lens attached"

Pages 39 and 45 in the manual describes how to change the focus mode to manual.

http://cdn-10.nikon-cdn.com/pdf/manuals/noprint/D5100_ENnoprint.pdf

Are you aware that Nikon now offers a camera that is dedicated to deep space photography, without the red filter?

https://www.slrlounge.com/nikon-d810a-announcement-first-full-frame-astrophotography-dedicated-dslr/

Also, Canon has cameras that have generally done better with astrophotography than Nikon's but this could be a game changer.

Good luck, Ed. Let's see some results!

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Yes, you are apparently correct - the general UHH population is less informed. No need to go to the astro forum when the Ed is just having a problem with a camera error message that can be resolved with a setting.

Bobspez Loc: Southern NJ, USA

Gene is correct. The autofocus must be set to manual and the exposure must be set to manual. This is the same as if you use an old nikkor film lens with no electronics in your camera. I don't know what you are taking pics of and whether you have tracking. If you do have tracking, planetary pics are generally taken with video and the frames (usually a thousand frames or so) are stacked in a free program like registax to give a superior image of a planet.

Ed Greding Loc: Texas

Thanks to those who replied. I'll check with the astronomical forum.

imagemeister Loc: mid east Florida

Sony's have a release without lens option in the menus - don't know about Nikons.....?

Ed Greding Loc: Texas

Gene51and others trying to help: Thanks! The problem is that setting the exposure involves (I assume) setting the shutter speed and the f-stop. First I put the Mode Dial on M, then set the ISO. Next comes the shutter speed on the LCD by turning the Command Dial to the desired speed. The last should be to set the f-stop, which is normally done also on the LCD. With the regular lens present I then would press the Aperture Button, which doubles as the Exposure Compensation Button---hold it down and turn the Command Dial until I have the aperture I want; it works fine if the lens is there. With the telescope replacing the Nikon lens,however, the f-stop place on the LCD just reads "f____, and remains that way, indicating no aperture number. And the message "no lens" remains. Please forgive my lengthy description---some of these terms are new to me. ---Ed

blackest Loc: Ireland

This essentially seems no different to using a fully manual lens, usually there is an aperture ring of some sort where you would set your f-stop. Without that aperture ring there is no way to adjust the f-stop it is what it is and you just need to set shutter speed and iso to suit.

There is no lens the camera understands since there is no communication between the lens and the body. This is perfectly normal. For modern lenses the focusing is done with the aperture wide open and then stopped down to the desired value for the photograph. This works fine since a difference of 1 stop is half the light. If the metering at wide open on an f4 lens was say 1/500 of a second and the desired aperture was f5.6 then the exposure would be 1/250th f8 would be 1/125th f11 1/60th ...

With something like an m42 lens i would use aperture priority mode and the body calculates a shutter speed for that iso and aperture If i then stop down the shutter speed will reflect the reduced light directly. Some of my russian lenses are preset lens where you set a minimum aperture in practice you can set the aperture anywhere between max and min , which i often do in order to realise a minimum shutter speed.

With km lenses on a pentax the lens can be stopped down by the body but to an unknown value in this case the green button is used to step down measure the light and calculate the exposure. With the km lens the aperture lever movement wasn't proportional to the f-stop with the ka type lens it was and lenses were encoded with max and minimum apertures and the body could move the aperture lever to any aperture in between.

Anyway in your case the aperture is unknown which is why f-- and in manual mode you need to set an appropriate shutter speed and iso.
in aperture priority mode the camera could attempt to set an exposure but since most of what it see's is black it will over expose to try and make it gray. You might be able to use exposure compensation to correct it but you are probably better to just chimp it in manual that is set an exposure see if it is too long or too short and adjust it.

I would imagine nikon would work similarly to my Pentax. or even my Panasonic g5 when i attach a dslr lens to it. The g5 needs to be told in a menu item to shoot with no lens attached (really just undetected).

RWR Loc: La Mesa, CA

Is your Focus-Mode selector set to “M”?

Ed Greding Loc: Texas

Thanks blackest. I think it may work as you apparently suggest: put it on Manual using the Mode Dial, then use shutter speed, adjusting through results. On the LCD the only manual setting is an M, but it's " faded", and the cursor cannot be placed on it. I think that M on the LCD relates to focus, which I can do with the telescope itself. Thanks! Ed