using BYE w lenses

[johnhenry]

I wanted to start into this gradually so I was planning on using a Canon 200mm f/1.8 with BYE on my 7D until I get my GEM properly aligned and that the syc motor is working correctly

 

Does anyone have experience/tricks/features that are particularly useful with longer/faster lenses like this one?

[astroman133]

How are you going to mount the camera? fixed tripod? tracking mount? piggybacked on a scope with a tracking mount?

 

Here are my suggestions, regardless of the answer to my previous question.

 

First, watch the tutorials on this site.

Second, practice with BYE indoors to become familiar with how to use it and verify that your cabling works.

 

Now for some tips:

1) Do not try to use LiveView for focusing with the lens. You won't find stars that are bright enough to be useful. There are 3 ways that you can focus, besides LiveView...

a- Use the moon as your focus target,

b- Shoot a short of 10-15 second Snap image and measure the FWHM of the star in BYE of a reasonably bright star in the image; adjust focus; repeat to get the lowest FWHYM, or

c- Play with the focus during the day to figure out how far true infinity is from the focus stop, and then re-create that position at night. Then use to nail focus.

2) Set the ISO to 800

3) Close the lens iris down a couple of stops. This can improve star shape for many lenses.

4) Shoot RAW images, unless you don't have software that can process the RAW images. Plan to get some image processing software that can read and stack Canon RAW files.

5) Try a 1 minute exposure. Depending on sky conditions, star shape, image brightness, lengthen or shorten the exposure. Once you have a good exposure, shoot an hour's worth of exposures.

6) After shooting light frames, shoot at least 20 minutes worth of dark frames with the same ISO and exposure as the lights (just cover the camera lens).

 

That should be enough to get you started.