Cool Rho Ophiuchus Region

[avandonk]

Finally got a complete clear night with reasonable conditions. So I added much more data to data from the other night.

Details Canon 5DH, Canon 300mm F2.8L at f/5 with aperture.

Exposures all at 400 ISO and the fridge set to -5.0C. The interior is at a constant -0.9C at this setting. This is the environment the camera is in.
Exposures 12X(2m&4m), 24x8m, 8x16m. The usual HDR method.

Large full resolution image 4MB.
http://members.optusnet.com.au/~fmlee/rho09.jpg

The faint dust shows up much better with less noise due to the cooled camera. This is a crop and the FOV is 5.4x4.6 degrees.

Bert

[strongmanmike (Michael)]

Man, that lens is now a beauty Bert! Can't believe you left it so long before fixing it Beautiful pinpoint stars all over

Does need a lot more exposure but the sharpness and wide field is a pleasure to view

Mike

[bluescope]

Very smooth Bert ... the dark lanes really show up well and the colours blend nicely.

[Craig_L]

Stunning Steve! Whats the lens like at 2.8?

[multiweb (Marc)]

Very nice. Superb widefield

[Garyh]

Lovely Bert! Nice and deep!
My 100mm is itching to have a shot of this region!

[jjjnettie (Jeanette)]

Beautiful image Bert.

[h0ughy (David)]

ooohhhhhhhhhh thats nice

[avandonk]

Thanks all, for the comments.

Mike it is difficult to put an aperture of 56mm in front of a lens of 104mm clear aperture. The resulting image quality is of course superb as you are only using the central almost perfect region of the optical train.

All secondary aberrations are almost non-existant and any diffuse scattering inside the lens gone.

In the past when I used the lens' iris the diffraction spikes on the bright stars looked terrible, at least to me.

The fridge gives me the edge with the very weak nebula and dust signal at my light polluted site. Notice how the dust near Antares now has the colour of the faint Cometary Globules rather than being swamped with orange from internal scatter from the very bright Antares.

It feels as if I have just started to use this lens for the first time..

Bert

[Tom Davis (Tom)]

Always wonderful to see!

Tom

[troypiggo (Troy)]

That's a ripper!

[telecasterguru (Frank)]

Fantastic image.

[gregbradley]

Really nice image Bert. Its great when you get your gear all finely tuned up.

Greg.

[marc4darkskies (Marcus)]

Very nice image there Bert for sure. Tight stars and lovely colour - it definitely does justice to this lovely patch of sky. Some more data wouldn't go astray of course.

Cheers, Marcus

[sheeny (Al)]

Superb, Bert!

Al.

[tornado33]

Excellent work mate. The 300mm lens here from you has a very fancy iris with a large number of leaves, making a stopped down setting almost perfectly round. I must try some stopped down imagery and see what I get
Scott

[avandonk]

Thanks all for the comments. It just shows if you keep at it you can get better.

Yes Scott the manual lens does have a very good iris as it is manual. The autofocus and auto iris motors can only handle so much mass to work quickly. Although having the aperture before the lens stops all light that does not contribute to the image. This minimises contrast loss due to scattered light inside the lens from this unwanted light.

I will collect more data. This image has only had the levels tweaked from the image that EasyHDR produced.

Here is a full resolution tiff 46MB if anyone wants to have a play in PS.

save it and use your favourite viewer.

http://d1355990.i49.quadrahosting.co.../RHO_large.tif

I have just organised a new host for images with 1GB storage limit. Bigpong Bigblog with extra storage stopped working and after two hours on the phone to attempt to rectify the situation and now weeks later no change. I gave up. The phone call (mobile)would have paid for the first three months of the new provider. They are based in Melbourne so if anything goes wrong there will be instant response.


Bert

[avandonk]

Greg it was Mike S. that convinced me to stop down. I am glad I took his advice. It was me who was pig headed by insisiting on using the lens wide open. The very slight aberrations become quite noticeable with long exposure astro work. The lens is not baffled as well as high end OTA's.

When attempting to optimise a system we scientists call this being stuck in a local minima when the real one is over the next tiny maxima.

Bert

[gregbradley]

That's interesting about the iris causing spikes on some lens shots. I often wondered why lens shots often showed those multiple spikes.

There's a guy called Pertti who posts on the Yahoo digital group and he was very informed various lenses and often posted reviews. He would often say most lenses did not perform fully open and needed to be stopped down 2 stops. I have a few lenses as well and I found they needed to be stopped down usually.

As I recall he felt the Canon 200mm F2.8 was a good one, so is the Nikon 180ED F2.8. I like my Nikon 50mm F1.8, I also have a 85mm Canon older style that's quite good.

I have seen some hot shots with a Zeiss 300mm F4 (but no better than yours).

The bog standard Canon 18-55 ain't that bad also.

Pentax 6 x 7 lenses seem to do well.

I have a 2x Canon 105mm lenses. One I haven't used for Astrowork and that may be nice as it is quite new and is supposed to correct for the 1.6X factor for APS sized chips.

I'd love to do a panoramic mosaic of the Milky Way this winter.

Also be nice to do one in colour + Ha. Like a really full on one.

Greg.

[avandonk]

Here is the 40MB PNG file that should display in your browser

http://d1355990.i49.quadrahosting.co.../RHO_large.png


Bert