Using a ND filter for variable stars

pscharff

Hello,

I am doing photometry on variable stars by using my Seestar S30. At the moment the target is T CrB. I usually use a setting of 10-30x 10s subs. But on the last 10 days I have got a saturated T CrB star more and more when using these settings.

Now I consider to place a ND filter in front of the Seestar to reduce the bightness of the stars.

Can you please tell me, if this procedure would work correctly, or does the Seestar compensate it by turning up the gain, so that the filter is useless?

Patric

marvindj

Use your filter then inspect the fits file(s) generated by the S30. The GAIN used is stored in the FITS header. My guess is it will continue to use what appears to be a hard coded value of 200. If you want to manage the GAIN value used, try using the seestar_alp application rather than the native Seestar app. Though if you are performing photometry, perhaps you are already using seestar_alp....

pscharff

marvindj
At the moment I would rather use the "official" app, but thanks for the hint. Perhaps ZWO will add corresponding features to the app in the future, like the possibility of setting shorter exposure times.

Patric