Widefield Sagittarius

[Terry B]

Dear All
This shot is my first attempt at a wide field guided shot.
It is taken with a pentax 645 with a 80-160 zoom set at 130mm. I had it perched on the top of my VC200l looking down the empty tube rings that usually have my 120mm guide scope. I didn't realise at the time but the rings have caused some vignetting. It was guided using a Qguide for about 30 minutes. Film was Fuji pro400- and to prove it is film I have left the data imprint on the side.
The scanned negative at only 2400dpi still produced a hefty 65meg tiff file. You got to love these big negs.
North is to the right and east is up.

[rogerg (Roger)]

That's interesting that you can still get Provia 400 in the medium format, as they stopped doing the 35mm format a little while back

I'll be interested to see what you achieve with this camera and wide field photography. I always thought medium format astrophotography was under-done by the masses. But I never got around to buying a camera myself so can't talk.

It looks like maybe the exposure of the scan was a little too strong or something mabye? For 30mins on Provia 400 slide film I'd expect to have huge amounts of data on the slide, much more than what you have here, and it wouldn't look so over-exposed/pushed in the centre..... Is the medium format provia less sensitive do you think or just processing touches?

Irrespective of all that it's a pretty good shot for a first time The first few rolls of my film in 2000 or so were all trailing to various extreme degrees

[Terry B]

Originally Posted by rogerg

That's interesting that you can still get Provia 400 in the medium format, as they stopped doing the 35mm format a little while back

I'll be interested to see what you achieve with this camera and wide field photography. I always thought medium format astrophotography was under-done by the masses. But I never got around to buying a camera myself so can't talk.

It looks like maybe the exposure of the scan was a little too strong or something mabye? For 30mins on Provia 400 slide film I'd expect to have huge amounts of data on the slide, much more than what you have here, and it wouldn't look so over-exposed/pushed in the centre..... Is the medium format provia less sensitive do you think or just processing touches?

Irrespective of all that it's a pretty good shot for a first time The first few rolls of my film in 2000 or so were all trailing to various extreme degrees

Sorry for the misunderstanding. It is fuji pro 400ASA print film. It was a 220 roll.
My image processing is not great. I just played with the levels in photoshop elements. The only other image precessing program I have is the gimp but it runs in linux and I was too lazy last night to reboot into linux.

[Dr Nick (Nick)]

Nice detail

[leon]

Good effort Terry i quite like it, pretty sharp too.

Leon

[Terry B]

Originally Posted by leon

Good effort Terry i quite like it, pretty sharp too.

Leon

It's curious about the sharpness. This sort of image is certainly a good test of the lens. I took the photo at f4.5 ie wide open. This should have the worst image quality for the lens and it seems too. An enlarged image from the centre around M7 is pretty sharp but when you go to the edge there is some smearing of the stars especially in the corners of the image. This shows in the enlargment of M20. This is all only visible with a very big enlargement ie 5000 pixels wide. I will try it stopped down a bit next time and see how much better it is.

[leon]

Terry now that you enlarge it like that i can see what you mean, it is a fairly heavy crop though, however the first image you posted appears fairly sharp overall, the stars appear nice and round.
On a closer inspection of your first image there is a little degrading at the edges.

I, have found with most lenses that the actual infinity make is not always the best setting, sometimes a little before or a little after that make can be your best focus.

It is only a fraction of a mm, but can make all the difference.

Leon

[Ric]

A great image for your first widefield Terry.

very nice and sharp.

[Geoff45 (Geoff)]

Hi Terry
You can squeeze a lot more detail out of this. I had a quick go with PS curves and got this result. I'm sure you could get a lot more out of the original image.
Geoff

[Terry B]

Originally Posted by ghsmith45

Hi Terry
You can squeeze a lot more detail out of this. I had a quick go with PS curves and got this result. I'm sure you could get a lot more out of the original image.
Geoff

I agree
Interestingly I am looking at this on my work computer vs the home one I processed the image on. It looks much brighter on my home computer. I will have to compensate for this when I process at home.

[Geoff45 (Geoff)]

Originally Posted by Terry B

I agree
Interestingly I am looking at this on my work computer vs the home one I processed the image on. It looks much brighter on my home computer. I will have to compensate for this when I process at home.

Hi Terry,
Slightly off thread here:
You need to calibrate your home or work monitors (or both)) if they are showing different brightnesses for the same pic. If you have Photoshop, there is some software (Adobe Gamma) that comes with it and this will get it in the right ballpark, although hardware solutions (Google Spyder2 Pro) are better and of course more expensive. Getting a pic looking nice on your monitor and then finding that the print is totally different is really frustrating.
Geoff

[Terry B]

I have made another attempt at this image having downloaded the gimp for windows rather than using my old version in linux. Much easier to access now.
The curves function is very powerful. Now to learn how to tame it.