Dual mirrorless piggyback imaging setup

[gregbradley]

I fancied some mirrorless camera imaging last weekend.

I rigged up my Sony A7r2 with a Zeiss 85mm F1.8 lens and a Fuji XT2 with a Fuji 16-55 F2.8 lens with intervalometers (the Fuji has its own inbuilt one so I did not end up using the external intervalometer for it).

On top of my CDK17 autoguided with a MMOAG and SBIG STi guide camera on top of an AP1600 mount under dark skies.

14 x 5 minutes ISO640 for the A7R2 (ISO 640 is one point where the dual gain amplifier reduces read noise) and 10 x 8 minutes ISO800 (same point for Fuji) under a 1/3rd moon.

Later I setup a Pentax 67 75mm F4.5 with a FLI colour filter wheel and Proline 16803 camera autoguided as well same as above. Wow. I like that one.

Resulting images shortly.

http://www.pbase.com/image/165775752

There are so many different ways to enjoy astrophotography.

Greg.

[Octane]

Greg, your link has an extra http:// in front of it. :)

H

[beren]

Very nice setup Greg.....How do you find the Fuji 16-55 2.8 ? compared to the 18-55 fuji lens?

[gregbradley]

Thanks Humi. Fixed. The IIS box puts one in front and the copy and paste of the address had one too.

I don't have an internet internet stutter stutter - honest!

Greg.

[RickS]

Very cool, Greg! I'd love to do some work with a good quality camera lens and a big sensor one of these days...

[gregbradley]

I have had 2 copies of the 18-55. I used the first one a lot. At 18mm F2.8 its great for astro. But of course as you zoom in you lose your F2.8. I found the image quality great on the XT1.

My current 2nd copy I am assuming is fine. But with the 24mp XT2 I find its performance a little less satisfactory. Its a fine lens but I notice now it has a sharpish area in the middle of the image.

The 16-55 first of all of course is a bit wider at 16, plus its constant F2.8. So if you zoom in to frame the shot you retain your F2.8 which is what I did with it on the weekend imaging Rho Ophiuchi.

The 16-55 is a very even lens, excellent performance anyway I use it, great colour, sharp. Is even slightly better in performance than the legendary Canon 24-70 F2.8Lii which I also use sometimes. So yes a very very nice lens and probably my favourite Fuji lens. Its a tad large but not compared to full frame 24-70 lenses.

I have already done a nightscape with it and it performed great. It really does have prime lens performance across the zoom range. A really top lens.

Greg.

[gregbradley]

As much fun as the mirrorless are they don't even vaguely come close to the Proline's performance which is mind blowing with this lens. I was loving the Ha downloads. I have used it before but this was shot at altitude at a dark site under great seeing (it often is there) with excellent tracking (very slight tilt in the lens a note for next time to correct it). There are features in the Milky Way rarely presented in images.

I shot a 4 panel mosaic (was planning 7, had the clear nights to do it but had generator problems that lost me 1 night). Its coming soon. More panels next new moon. 1/3rd of a moon didn't seem to bother it but 1/2 moon did.

Greg.

[Camelopardalis]

Nice one Greg :thumbsup:

There's something to see at every focal length :D

[gregbradley]

There sure is.

Greg

[beren]

Cheers.....more temptation :thumbsup:

[RobF]

What do you do for focus and dew control Greg?

I'm guessing you've got some protection at your remote site from the elements, but not a dome?

[gregbradley]

Cheers.....more temptation :thumbsup:[/QUOTE]

Yes endless isn't it?




Leave the camera outside in the car before using it. Don't take it from inside the house as at 5C it will likely dew up straight away. I was not imaging all night but only for about an hour and a half so dew was not an issue. I have in the past used a self adhesive heat pack that I stick around the lens and then a coat of a piece of foam insulation held on with a rubber band. That would work for 6 hours or more for time lapses.

Focusing is easy on a mirrorless.Set the camera to manual focus, use ISO6400, pick a bright star and use magnified view.Now simply focus so the star is smallest. With some lenses strangely exact focus seems to occur when the star appears to disappear for a second on the LCD or EVF. I don't use focus peaking as it interferes with the view of the star too much. I usually go back and forth around correct focus so I can see where it should be. On lenses you'll see chromatic aberration come and go and the point where there is no chromatic aberration is also the correct the focus point.

I usually take a 30 second exposure and then check it using magnified view to confirm focus is sharp. I have taken a long series in the past only to realise later focus was off so I learnt my lesson there.

lonelyspeck.com sells a focusing aid if you want. Most DSLRs have live view these days and that is much the same procedure. Not sure if they have magnified view or not they probably do.

Greg.

[Atmos]

I'll also usually drop it to its fastest F/stop and focus it there as it has the smallest critically focus zone. I am using a bahtinov mask though. The one I have it good for telescopes but I don't think there are enough gaps or small enough gaps to get a nice focusing image.

[gregbradley]

Not a bad idea. I usually image at the widest on most lenses but when on my mount I focused at the imaging focus. Some lenses have focus shift where it may be in focus at one F stop but not at another. So keep that in mind if you get soft photos.

lonelyspeck.com has a focusing aid which is a custom Bahtinov Mask. Its not designed to work on really wide focal lengths though. 85mm it should easily.

Greg.