Posts Made By: Michael Minnhaar

A few shots of Holmes before the moon came up in Portland tonight.
All 1:1 crops, inserts on the right are the JPG's straight out of
the camera (Canon 350D), which were used to compose the main shot.

Michael

Here is what professional astronomers do when the skies are
not that transparent:

http://amandabauer.blogspot.com/2007/12/hotel-mauna-kea.html

Enjoy,
Michael

Given these are plain 4-element ploessl's I'd expect around
52-55deg AFOV. The inner diameter of a 2" barrel would start to
vignette around 50deg AFOV at 50mm FL.

You that's about what you might see.

Michael

... until next Fieldday.

Michael

for Thursday Aug 28th to Monday Sept 1st, on the usual Airstrip with great Mt Lassen views. Unfortunately it's the same weekend as OSP, guess there are only so many new moons in a given summer.

Michael

I noted recently a couple of postings complaining about email response times.
Now it struck me and I wonder if I'm now to slow to deserve dealing on Astromart:

I reponded to a sellers ad, the seller responded by saying its still up
and what the total with shipping would be and if its ok with me.

I replied "$xx is fine with me, please let me know where to paypal the funds".

He replied "... send to xxx ...", but I did't read this answer for another 20hrs,
as I was out watching the perseids and then sleeping in.

The next day at noon I have two emails: The above to pay and another one that he
now sold to someone else. Both sent within less than 20hrs of each other.

In the followup he declares I have issues with promptly takeing care of my business,
he had no idea I'll actually buy it and that 20hrs is obviously enough time for others,
like his current buyer.
There was no mentioning of deadlines or urgency up to this point, nor did he reply
to my previous emails the same day, Given we were in different timezones, this is
came as no surprise to me.

I wonder: Is answering emails once a day no more acceptable for normal (i.e. not time-critical) business ?

Also, for me a deal was mutually confirmed. Should I leave feedback to document
such rude attitude ? I'm thinking of 3 stars, per FAQ the "average" rateing, but
still well below the real average rateing.

Wow,
I'm just afraid this means some significant change is comeing up at Vixen. I doubt any manufacturer would risk alienateing his resellers by direct selling at such discounts.

Michael

There is tons of fairly scientific stuff on compareing DSLR for deep sky imageing, see at the end.

My 2 cents would be: There is little difference.
The (older) Nikon D70/D200 were a bit worse in noise and sensitivity than Canon 20D/30D and RebelXT/XTi. The new Nikon D50 seems to do better now, I haven't read anything scientific on the K100, yet. That's about where the differences for astro photography end.
All above cameras have the same size of sensor, for all there are t-mount adapter rings to mount it to a scope. The Nikon's and Canon's all have a "bulb" mode to take any long exposure you want, Pentax very likely, too. All the Nikons take all Nikon lense ever made, the Canon take all Canon EF lenses ever made, the Pentax ...

From experience, if you already own certain lenses or have friends to swap lenses with, that's a factor to consider, too.

Michael

http://www.clarkvision.com/imagedetail/
http://www.astrosurf.org/buil/20d/20dvs10d.htm
http://www.pbase.com/terrylovejoy/dslr_tech&view=tree

IMO it only makes sense as a standalone exposure device.
A few weeks ago I had to decide between this and a traditional USB-parallel port adapter+optocouplers:

* All the timing functions it provides are already built into software I use to control my camera. There is even a freeware, scriptable exposure program out there.
* A traditional USB/parallel adapter needs no extra 9V/12V source
* As of a few weeks ago, DslrStar lacked a "dumb" mode to just emulate a parallel port. Thus you *need* to have exisiting software rewritten to use it, while a parallel port emaulator works right out of the box.
* When used as a stand alone device, it draws so much current, I have to haul the big battery again.

Michael

Removeing the IR/AA filter should change the required backfocus only by some 0.2-0.3mm, which is unlikely to do much for your problem.
On the top of the camera body should be a symbol like a circle with a dash through it. This is the exact location of the focal plane/sensor inside it.
Try useing a (simple) eyepiece with a known location of its fieldstop & focus it.
Then compare the fieldstop location with the focal plane indicator on the mounted camera and you know if you can place it within range.

Michael