[Aavso-photometry] Flats

[Tim Crawford]

David,

I use the Reveal bulbs by GE that Arne mentioned in a
previous email..... set up a couple of white cards in
front of the scope and bounce the light off of
them.... I have a reostat on the bulb which resides in
a metal reflector behind the scope and aimed up at the
white cards.... sorta dome flats... works great as
long as I have a good focus.

Simple setup.

my two cents worth

Ad Astra

Tim Crawford  CTX
Arch Cape Observatory




--- David Trowbridge <David at tinyblue.com> wrote:

> I generally take my flats right after sunset, aiming
> the telescope low in
> the eastern sky at an azimuth roughly opposite to
> where the sun went down. I
> put a T-shirt over the end of the telescope and take
> 4-5 images with each
> filter, then stack them. Would aiming higher in the
> sky, close to the zenith
> give better flats?
> 
> Occasionally I use a light box with incandescent
> bulbs, but it requires a
> long exposure, especially with the B filter. I
> probably need to replace the
> incandescent with halogen bulbs.
> 
> David Trowbridge
> 
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