Mars images update

On Fri, 25 Jul 2003 07:51:14 +0100, "Russell Healey"
wrote:

Setup #1 (Afocal):
Magnification: 902*2/20=90.2x
System focal length=70*90.2=6314 mm
System focal ration = 6314 /101.9=f 61.96 call it f 62!!

Setup #2 (Afocal):
Magnification: 902/5=180.4x
System focal length=70*180.4=12628 mm
System focal ration = 12628 /101.9= f 124

My behind-the-scenes helper (I'll keep Mr Tonkin's identity hidden)
pointed me to the formula yesterday.

I wanted someone else to do the calculations independently though
because to me f62 & f124 are figures that jump out at me as being
rather extreme.

Any imagers out there care to comment - or am I worrying about
nothing?

But I wish I was more a a practician than a theoretician when it comes to
astrophotography - I'm still stuck between
(1) Buying a digital camera and wading through the minefield of adapters and
supports.

Yes - it's easy for those of us who have slogged through the minefield
and come out on the other side to forget just how many options there
are out there.

(2) Using my SLR with eyepiece adaptor / T adaptor and waiting "ages" for
the results.

Film vs digital. Go argue that one on rec.photo.digital. Astronomers
are regarded as a minority on there and the arguments we put forward
for digital over film don't carry much weight as a consequence.
Cherry picking of arguments I think.

What really amazes me are the images that were taken with really big
scopes back in the mid-late 70's early 80's. By big, I'm talking 1.3m
reflecators and 0.4m refractors. The images I saw in one of my old
Mars books last weekend were made using film.

What can I say? Imaging has come on a lot ;-)

I have tried camera supported by separate tripod offered up to the eyepiece
but I find this very tricky to get square and focussed.

Russell Healey
Orion Optics Europa 200mm f6

Seperate tripod to the eyepiece isn't going to work very well at all.

If I can be so bold...

I have an Orion Optics 250mm f4.8 (IIRC!). It's an older model and
came on one of Orion's early GEM mounts. Although the mount is fine
for visual work, it's pushing the limit photographically.

You need a steady mount, and a decent RA drive (preferably DEC as well
to help you get things set up correctly).

I bought the accessory pack for my Europa which included a camera
adapter. That's the same adapter I now use to attach my digicam to my
Vixen refractor. Unfortunately, Mr naive here was a bit stupid and
glued a coupling thread to the end of the adapter to allow it to fit
my camera's thread. All I needed to get was a step-down ring for the
camera. We live an learn g.

Details of the adapter coupling can be found here...

http://homepage.ntlworld.com/p.lawre...icoupling.html

I don't know it this helps at all - if you need any additional info.
about my set-up please just ask.


--
Pete
Homepage at http://www.pbl33.co.uk
CCD/digicam astronomy