[APML] Takahashi BRC250 and E250 information

[Gaspar Bakos <gbakos@cfa.harvard.edu>]

Hi, folks,

This is a slightly off-topic message. I am trying to contact people who
are astrophotographers (thus they CARE about how the images look like),
and they have experience with either the Takahashi BRC250 or the E250
reflectors.

In a nutshell:
I would like to find out how the stellar profiles appear/compare in
these two telescopes (quantitatively).
And I would like to know about your experience with these optical tubes
(focusing, stability, thermal expansion, tube flexure, various
comments, etc).

---------------------------------------
And here it is in a bit longer version:

As a predoctoral fellow at the Harvard-Smithsonian Center for
Astrophysics, I am in charge of designing a fully robotic astronomical
instrument for the Smithsonian Astrophysical Observatory and Harvard
University. We are contemplating about using the Takahashi E250 epsilon
astrograph, or the BRC250 Ritchey-Cretien system coupled with our own
robotic telescope mount and large format CCD detectors.

Unfortunately, I found very scarce technical information on the web on
these telescopes, and I am turning to the astro-photographer community
for help.

0. I read that the list is limited to traditional film photography, but
as i see no other source, let me ask: does anyone have FITS files taken
with the E250 or BRC250 telescopes? High res scans of photos would be
also informative.

[[ Maybe even TIFF or other commercial format pictures would help. Raw
images would be the best, i.e. not ones that have been combined/stacked
from several individual images. ]]

Takahashi claims a 2 micron stellar size in the center for BRC250,
which is hard to believe. I can imagine maybe a 5 micron size. How is
E250 compared to this?

1.  Maybe you even have a spot diagram?
We would use the inner 37mm area centered on the optical axis in the
wavelength range of 500 to 900nm.

2. Another related issue: how did your find the appearance of the
out-of-focus profiles? Maybe you have images that were taken out of
focus? They would be very useful.

3. Do you have an idea what fraction of the light is blocked by the
secondary mirror for both E250 and BRC250?

4. My understanding is that BRC250 is very well corrected against
thermal changes. Is this correct?

5. Have you ever experienced tube flexure?

I am looking forward to hearing from you. It would be of GREAT help.
Please send images, or show me a link from where I could download
them.

With best regards,

Gaspar A. Bakos

Predoctoral Fellow, Solar, Stellar and Planetary Sciences Division
Harvard-Smithsonian Center for Astrophysics
60 Garden Street, Cambridge, MA 02138 (USA)
Phone(office): 617-495-7410 Fax: 617-495-7049
email: gbakos@cfa.harvard.edu or bakos@konkoly.hu
homepage: http://cfa-www.harvard.edu/~gbakos

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