Author Topic: Quick test of Pentax 6x7 lens  (Read 3202 times)

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Rocket Pooch

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Quick test of Pentax 6x7 lens
« on: Aug 23, 2010, 22:49:46 »
Hi,

I have just quickly posted this 3x10 minute Ha of IC1396, the camera and lens is now doing 12 20minute subs for tonight.

As I had expected the edge resolution of the lens is excellent and its really easy to focus at F4, its in focus or its out :-)

Anyway, the flickr link has the fill size version there


test1 by chrissuddell, on Flickr

Fay

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Re: Quick test of Pentax 6x7 lens
« Reply #1 on: Aug 23, 2010, 23:08:59 »
thats looking good Chris. Wish i had a large chip
It is healthier to be mutton dressed as lamb, than mutton dressed as mutton!

Rocket Pooch

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Re: Quick test of Pentax 6x7 lens
« Reply #2 on: Aug 23, 2010, 23:26:51 »
You still have time to get one delivered before the 3rd :-)  :o

MarkS

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Re: Quick test of Pentax 6x7 lens
« Reply #3 on: Aug 23, 2010, 23:33:35 »

That is certainly a very wide view, Chris.  I've never seen seen the Elephant's Trunk Nebula with so much surrounding context.

It's very sharp in the centre but I detect a slight ovalness at the extreme bottom left - but you only notice it at full size.

Nice one!

Mark

Rocket Pooch

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Re: Quick test of Pentax 6x7 lens
« Reply #4 on: Aug 24, 2010, 08:19:35 »
Hi,

I've done a little analysys on the image from last night, there is a gradient from bottom to top, probably the full moon I guess, also this lens does need a flat frame when imaging here, its probably will not when at Olly's.

Just trying to work out the field of view, I think its about, err I dont know, large I think, Rob can you plate solve the image in Maxim to get the actual size, bye the looks of it I will get the whole of the north american in, the whole of the heart and sole nebula or the complete vail?

On the bottom left there are some miss shaped stars, this might be some flex in the whole setup, I'll tighten everything.

Also I can't see the appature reduction in the image, I stopped the scope down to F4 and yet all the stars seem quite round.

Anyway, this little baby is packed for France, after I do some flat frames and make a dew shield for it.

Now where that bloody 8".

Chris

P.S. Here's an invert to show the field of the nebula.


IC1396 Invert by chrissuddell, on Flickr


RobertM

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Re: Quick test of Pentax 6x7 lens
« Reply #5 on: Aug 24, 2010, 09:10:15 »
That's looking quite good Chris, the lack of contrast is probably the full moon but stacking the rest of the frames should improve that a lot.

Will plate solve tonight but size wise look at my North American/Pelican, Heart/Soul and California images.  They were all with a 200mm lens.  Flex wise it's a difficult choice with a heavy lens, does the camera hold the lens or the lens hold the camera.  I'd suggest the former with a guide scope ring holding the lens because of the size of the chip.

Looking forward to the final result..
Robert

Rocket Pooch

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Re: Quick test of Pentax 6x7 lens
« Reply #6 on: Aug 24, 2010, 09:15:10 »
Hi Rob,

The camera holds the lens and its bloody heavy about 1.5kg, so I'm going to grab an aluminium plate and put one set of 5" guide rings on the lens in front of the camera, last night all of it was held on a dual dovetail by a Mofrotto camera plate :-( this I'm not happy with I kept watching it thinking, your going to drop!

So I'll make that up before we go away and ensure there is enough room to the right for my EOS1000D as well, then I'll have a dual camera setup.

Chris

MarkS

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Re: Quick test of Pentax 6x7 lens
« Reply #7 on: Aug 24, 2010, 10:26:14 »
Quote from: Rocket Pooch
... this lens does need a flat frame when imaging here, its probably will not when at Olly's.

I don't completely understand that logic.  Even with pristine skies you still don't want dust bunnie in your nebulae.

Rocket Pooch

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Re: Quick test of Pentax 6x7 lens
« Reply #8 on: Aug 24, 2010, 10:53:44 »
I don't have dust bunnies :-) here's my flat.  Also if the signal to noise is great enough uneven illumination is not really a big issues unless its bad.


MasterFlat (Medium) by chrissuddell, on Flickr

PhilB

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Re: Quick test of Pentax 6x7 lens
« Reply #9 on: Aug 24, 2010, 11:06:36 »
I especially like the negative image, Chris. I find it much easier to see fine detail in it.

Looking at this, the France trip images should be worth waiting for.
“Never worry about theory as long as the machinery does what it's supposed to do.”  Robert A. Heinlein

MarkS

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Re: Quick test of Pentax 6x7 lens
« Reply #10 on: Aug 24, 2010, 15:14:00 »
Quote from: Fay
Wish i had a large chip

Go on Fay!  You know you want to!

mickw

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Re: Quick test of Pentax 6x7 lens
« Reply #11 on: Aug 24, 2010, 15:43:26 »
Quote
Go on Fay!  You know you want to!

She hasn't got the bottle :roll:

Can't have an observatory.
Can't get a large chip.
Only allowed to play with rats and foxes.

Where will it all end  :roll:
Growing Old is mandatory - Growing Up is optional

Fay

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Re: Quick test of Pentax 6x7 lens
« Reply #12 on: Aug 24, 2010, 15:51:01 »
not in a good mood at th emoment. Got my T adaptor stuck again!!!!!!!! Cut two fingers trying to get it off. I am having a special tool made, but it is not ready yet. Saw a possible solution on EBay, which I have sent for....but I NEED IT NOW!!!!!!!
It is healthier to be mutton dressed as lamb, than mutton dressed as mutton!

Rocket Pooch

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Re: Quick test of Pentax 6x7 lens
« Reply #13 on: Aug 24, 2010, 16:04:29 »
Honestly, fay if you do things on the cheap you have all kind of problems, I'd suggest you get a nice QSI or FLI camera the 9000 KAF chip and a good astrograph like a planewave and maybe a decent mount, you will same money in the long run..

And fingers...

Fay

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Re: Quick test of Pentax 6x7 lens
« Reply #14 on: Aug 24, 2010, 16:06:47 »
I have 3 tools on order now!
It is healthier to be mutton dressed as lamb, than mutton dressed as mutton!