Ha Milkyway - Crux to Scorpius *lens stop*

[multiweb]

Here's another 3 panels I shot tonight. Still playing with the QHY8 and my Pentax lens. I held the front of the lens into a centering ring this time so I have less flop but still need to tweak things. Anyway it's a better result than my previous attempt (http://cid-6930d3ad12d5044c.photos.live.com/self.aspx/Astrophotography/milkyway%5E_A%5E_ha%5E_f.jpg#resId/6930D3AD12D5044C!974). That's 10x10min for each panel so abit under 5h.

There's a bigger one here (http://memkxw.bay.livefilestore.com/y1pPLLPuthE3NVVHdYemEiORt-c1HEjtXLP2NCFgZTgg55Z0FwOUF2FjpRhcZ 0a4DBTcLZoo47NJ3DQzk4rwJ17nXWOGYY4N 5-E/milkyway_A_ha_f.jpg?psid=1). Had to crop a bit to fit the three stiched in one panorama as it's a very big area. Maybe third time lucky I manage to get a flat field with no coma across the whole pic. :)

PS: Well I managed to squeeze some more subs before the clouds rolled in around 22:00. First panel same field center on Rigil Kent but I closed the aperture of the lens a bit and it made a huge difference. Reference frame attached below. Big fuzzy in the top left is Omega Cent. Still a bit of tilt on the right side but very manageable. Big thanks to Greg :thumbsup: Tomorrow I should be able to reshoot the whole milkyway this time as it clears the roof. Whoohoo! :party:

[AlexN]

Impressive... We want colour! :D

[Ross G]

Hi Marc,

An amazing photo.

Sharp and so much detail.

You have got the Pentax lens working well. The stars are sharp points even in the corners.

Thanks.


Ross.

[gregbradley]

Cool shoot Marc. These sorts of shots are pretty spectacular.

What's the setup? What problems have you had with it?

I am about to do some Pentax lens imaging with the Proline. Just waiting on the adapter to arrive.

Greg.

[multiweb]

Thanks guys but ... nah, doesn't look to good this morning with fresh eyes. :question: I have to try to stop this lens a bit see what happens. Will do some more tonight if weather holds. Got to sort out this field first.

Just a 18-35mm pentax lens [67mm dia] with an adapter, Greg.

[gregbradley]

The usual thing with most lenses is they need to be stopped down 2 or 3 stops. So an F2.8 may only be good at F4 for example.

I've used Nikon 50mm F1.4, Nikon 180mm F2.8 ED, Canon FD 85mm,200mm. The Canon's needed to go up to about F5.6, the Nikon ED was good wide open and the Nikon 50mm was good wide open. I needed a Canon FD to EOS adapter (ebay) to use them on an STL11.

Your standard camera lens is not made to the standards of most telescope lenses and also use cheaper glass that gives chromatic aberration.

I got some "cheap" Pentax 67 lenses. The 55mm F4 is supposed to be super sharp, also have a 165 and a 300mm and I think a 105mm. They are quite large for their aperture. The setup is FLI Proline, filter wheel, FLI PDF focuser adapter and the lenses. Then a guide scope ring to hold the longer ones at the end for support.

The 300mm 67 (medium format 6cm x 7cm) F4 EDIF as we know from Marco's work is the king of the crop and very hard to find one. Also expensive at around US$1200 to $1500+.

Pentax 67 lenses have a lot of backfocus. I have a list of various lenses and their backfocus. Pentax aren't the only ones with large backfocus.

Greg.

[multiweb]

Thanks a lot for all the info Greg. So if I need to go to F4 that means I need to close the lens let's say 15-20% from its full aperture for the same zoom setting right? At the moment it's fully open. So you don't even see the diaphragm hexagonal shape. When it's on the Pentax body it's driven electrically. On the QHY8 I have a bit of plastic wedged at the back to keep it open. I'll have to make a thinner one so it opens a bit less and try again.

The first pic I did I got from Crux past M8 down to M16/17 in one field. That was set to 18mm. Last night I did 35mm so it zooms from crux to just past the pointers down to Ara not even reaching NGC6188. So it's much tighter. Using 35mm vs. 18mm didn't do anything about the aberrations I have in the field though. :shrug:

[jjjnettie]

An image of epic proportions!
I'm not game to try a mosaic yet. But you've got me thinking, I should get the Nifty 50 out for some exercise.
A little more contrast maybe to bring out those dust lanes?

[Cosmic]

I totally agree with you jjj, that sums it up nicely. Just looking at that image makes you feel so surreal. Excellent Marc, what a great multiple capture of the milkyway.

[Stevec35]

Looks pretty good Marc but I think you do need to stop the lens down a bit. Going to be spectacular in colour.

Cheers

Steve

[multiweb]

Thanks guys. :thumbsup: Here's what it looked like before I cropped it... and the camera set up too - yep, it's a sock! :P

[RobF]

Really nice Marc, and thanks for showing the setup. Will eagerly await some more!

[jjjnettie]

You've certainly inspired me Marc.
While I'm not tackling a mosaic, I'm shooting a very wide field of the region right now with my stock 18-55mm lens.

[Hagar]

What a massive field Marc. Great detail now just a matter of adding some RGB to drive you mad trying to blend it all together.

[multiweb]

Thanks Rob. :thumbsup: Last night was no-go despite a clearish forecast. Tonight's not either but I'm hopeful I can further test the lens Wednesday and Thursday nights. Not much else to do with the screaming Jetstream of late, but that's what's keeping the high clouds off Sydney lately so I'm not complaining.


Are you kidding? :lol: I'm trying to keep up with your colorful awesomeness. :thumbsup:


Thanks Doug. :thumbsup: Color blend should be fine once I have a valid Ha scaffold. I have to sort out this field stop first though before I can go in production mode.

[gregbradley]

Yes that's right. No matter what focal length you set the lens to, you will almost certainly need to stop it down unless it is one of these exceptional lenses.

I remember on the Yahoo digital camera group there was one guy who spent a lot of time testing lenses and his findings were almost always you need to stop them down. The last part of the curvature of these lenses are where all their aberrations are. Not true of all lenses so a bit trial and error. A few quick test luminance images at various F stops will tell you.

But for instance last time I used lenses was Canon FD and Nikon 50mm on my STL11. The Canons needed to be stopped down to f5.6 as I recall but the Nikon did not require that.

I am about to test my Pentax 67 lenses but its already been tested by others so it should be a safe bet. The 300mm may not be great for LRGB
(chromatic aberration) but fine for NB. I am hoping the shorter ones will be OK for LRGB.

I have also seen great results from Zeiss 300mm lenses. Wolfgang Promper I think it was or perhaps Johannes Schedler.

Greg.

[multiweb]

Thanks Greg. Doing some testing right now actually. I closed the aperture a bit. It helped but I'm closing it a bit more see what happens until I find the sweet spot.