How to find suitable serial cable for Canon EOS 40D

[roadrabbit]

In order to activate mirror lock in astrophotography it says I need a serial cable for my Canon EOS 40D camera.

Where do I get such a cable, and how is it attached to the camera?

I already have a USB cable attached to connect to my laptop (W10 pro 64 bit).

[astroman133]

Use of mirror lock is usually unnecessary. This is especially true if you are taking long duration images of deep sky objects. The proof is to try imaging without mirror lock.

If you still feel that you need mirror lock functionality you should follow the links given at the top of the "supported cameras" page (click on the link in the footer of this page) to check out the Hap Griffin and Shoestring Astronomy web sites.

Note that these serial cables do not replace the USB cable, they are used in addition to it. The USB0 end of the cable plugs into an empty port on the PC that is running BYE and the other end plugs into the remote shutter jack on the camera.

You also need to follow the instructions in the BYE User Guide to use the serial cable for shutter control and mirror lock.

[roadrabbit]

Hi Rick, and thanks for the fast reply.

A little more reading has also helped!

I am setting up my new system in a remote garden observatory. This means that when I initiate a capture session I should not be anywhere near my telescope but in my office. Thus, as I understand it, one of the prime objectives of having mirror lock working has been removed - I will be too far away for me to cause my rig to vibrate  😇

Regarding long duration images my BYE manual (page 102) implies I may not be able to take individual (TV) images longer than 30 seconds. However, my 'Capture Plan' window allows settings of way more than this. Am I misunderstanding the tag "TV"?

[astroman133]

First, mirror lock is NOT intended to eliminate vibration effects caused by you. Operation of your camera and telescope should be entirely hands off. With a DSLR there are multiple actions that occur when you press the shutter button. Consider that you are operating the camera manually with an autofocus lens installed. When you press the shutter button the mirror that allows you to see through the lens for framing and focusing flips up, then the shutter opens to allow light to be captured by the sensor. Then the shutter closes and the mirror flips down.

In BYE, mirror lock is designed to allow a configurable delay period between when the mirror flips up and when the shutter opens. This allows any vibration caused by the mirror flipping up to dissipate. That is all it does. Vibration from the mirror flipping up is typically negligible and so is seldom used.

If you do get a newer camera that supports Mirror Lock over USB then no serial shutter cable is necessary to allow you to use Mirror Lock. In either case, you need to go into BYE's Advanced Settings and enable Mirror Lock and also set the mirror lock delay interval in the capture plan settings. If you do use a serial cable then you need to select that cable in the Cable Support dropdown list in the Capture Plan Center on the Imaging panel.

Now to try to answer your question about Tv exposures.

Tv exposures are "timed values". This is where you select an exposure, say 1/500th of a second,  press and release the shutter and the camera takes an exposure with that specified duration. Canon cameras typically support Tv exposures from 1/4000 sec to 30 seconds. To shoot exposures longer than 30 seconds you need to put the camera into BULB mode.  Different Canon cameras support BULB mode differently, so be sure to read about it in the 40D user manual.

If your camera is in BULB mode and you are operating it manually, the shutter stays open for as long as you press the shutter button. 

With BYE you specify the exposure duration and BYE takes care of sending the open shutter and close shutter commands to the camera. This allows totally hands-off operation.

I have a newer T5i. To use BULB mode with BYE I put the camera in Manual shooting mode via the rotary dial on the top of the camera. Then I use the BYE Shutter dropdown control in the first row of the capture plan to select BULB from the list of Shutter settings. This enables the Duration control where I can specify the duration of the bulb exposure, like 600 seconds. I also set the ISO to typically 800 (for you camera you might choose 400). You can also set the pause interval between exposures, but for long duration imaging 0 is typical. You can also set a delay interval. A non-zero delay will cause BYE to pause between when you press the Start Capture button and when BYE executes the first row of the capture plan.

I hope this helps.

[roadrabbit]

Wow! You are the man!

Thank you again for your swift reply - I am so grateful.

To your first point, I feel a little stupid. Of course I knew that it removed vibration from the mirror flipping open - how could I forget? I guess that from a long shutter opening (such as 300 secs) the duration of any vibration will be a tiny fraction of the total shutter open time, so its effect, as you suggest, would be comparatively negligible.

Regarding BULB setting - yes, thankfully, I can set it just as you describe for your T5i, also the Delay interval is available as well. It was this I was thinking about regarding the first point and the effect of my heavy feet!

There was a point when I was beginning to think my EOS 50D was going to prove unusable. I am so pleased that this is proving not to be the case.