Astrophotography using a medium format camera

[Parag Shankar]

Dear all

Greetings! I am a new user on this forum. I am an astronomy researcher and communicator for last 30 years and I am interested to enter into a new domain of Astrophotography with a medium format camera.

1. I read on internet that Pentax 645z is better for the purpose. I don't know why? Is anybody out there doing astrophotos with this camera? I also have a query regarding the digital zoom of 645z? How much it is? 10x?

2. Anybody aware about a lens which can fit on this camera but having a front diameter more than 72mm? In Astro, we need large frontal diameter lenses as we work on nearly zero light. So larger the diameter of the mens more photons hit the sensor.

Thank you.

Best Wishes

Parag Shankar

India

 

[JimKasson]

Dear all

Greetings! I am a new user on this forum. I am an astronomy researcher and communicator for last 30 years and I am interested to enter into a new domain of Astrophotography with a medium format camera.

1. I read on internet that Pentax 645z is better for the purpose.

Better than what?

I don't know why? Is anybody out there doing astrophotos with this camera? I also have a query regarding the digital zoom of 645z? How much it is? 10x?

You don't want to use in-camera digital zooming for astrophotography. If necessary, crop in post.

2. Anybody aware about a lens which can fit on this camera but having a front diameter more than 72mm?

With adapters, you can use just about any MF camera on just about any telescope, giving you apertures as large as your wallet can stand. However, not all telescopes will cover all fornats.

In Astro, we need large frontal diameter lenses as we work on nearly zero light. So larger the diameter of the [lens] more photons hit the sensor.

That's important only for stars. For extended objects such as nebulae, the f-stop is the key metric.
Jim

 

[Navman]

I've been exploring use of the 50R for astro, with a mix of widefield and more zoomed in images. I'd previously used a Sony A7RII in continuous mode (to avoid Sony's star-eater algorithm), and the 50R represents a substantial jump in performance. In my experience the gains come both from the better low-light performance, and the freedom from the Sony restriction of staying under 30 seconds to avoid star-eater filtering. I've done exposures up to 2 minutes with my 50R with great results, and the built in long-exposure and mulit-exposure options greatly simplify image capture.

The GF 45/2.8 is perfect for widefield shots, with a little vignetting being the main issue when used wide-open. The GF 110/2 is a phenomenal lens for tighter shots, and is oikay at F/2, but improves a great when used at F/2.8. I've also just purchased a GF 250, and used on a tracker, this would have to be the sharpest tele I've ever used for astro. At F/4 it has some comma around larger stars in the corners, but stopped down to F/5.6 the corner image quality is close to indistinguishable from the centre.

Processing was initially a challenge as the standard raw-import routines in the software that I use don't recognise the .RAF files from the Fuji - converting to DNG gets around that. The image below is a stack of 10 1-minute and 15 40-second exposures with the GF 110 at F/2.8 showing the Orion and horsehead nebulas, Barnard's loop, and (faintly) the Witch head nebula.

John

 

[JimKasson]

I've been exploring use of the 50R for astro, with a mix of widefield and more zoomed in images. I'd previously used a Sony A7RII in continuous mode (to avoid Sony's star-eater algorithm), and the 50R represents a substantial jump in performance. In my experience the gains come both from the better low-light performance, and the freedom from the Sony restriction of staying under 30 seconds to avoid star-eater filtering. I've done exposures up to 2 minutes with my 50R with great results, and the built in long-exposure and mulit-exposure options greatly simplify image capture.

The GF 45/2.8 is perfect for widefield shots, with a little vignetting being the main issue when used wide-open. The GF 110/2 is a phenomenal lens for tighter shots, and is oikay at F/2, but improves a great when used at F/2.8. I've also just purchased a GF 250, and used on a tracker, this would have to be the sharpest tele I've ever used for astro. At F/4 it has some comma around larger stars in the corners, but stopped down to F/5.6 the corner image quality is close to indistinguishable from the centre.

Processing was initially a challenge as the standard raw-import routines in the software that I use don't recognise the .RAF files from the Fuji - converting to DNG gets around that. The image below is a stack of 10 1-minute and 15 40-second exposures with the GF 110 at F/2.8 showing the Orion and horsehead nebulas, Barnard's loop, and (faintly) the Witch head nebula.

John

That is very impressive. Does the GFX have much response at the hydrogen alpha line?

--
Posted as a regular forum member.
https://blog.kasson.com

 

[Navman]

That is very impressive. Does the GFX have much response at the hydrogen alpha line?

I've not seen any measurement of its response, Jim - my impression, not formally tested, is that it is capturing more nebula detail than I did with the A7RII when given equivalent exposure.

-John

 

[rcautox]

Great photo John! I don’t think I quite understand you post-the photo is a stack of 10 taken at 1min 15s? Or from 1:15 to 0:40s?

 

[Navman]

Great photo John! I don’t think I quite understand you post-the photo is a stack of 10 taken at 1min 15s? Or from 1:15 to 0:40s?

Multiple exposures, aligned and stacked to increase the signal to noise ratio - a common approach in astrophotography...

-John

 

[Parag Shankar]

Dear Jim,

Thank you for your response to my relatively naive queries...

I refined my queries here:

In Astro work, I need to zoom the "live view" which is seen at the back LCD screen. Does Fujifilm GFX 50S LCD has a zoom feature?

(My existing Canon 60D does it with 10x. I need to to check the Bahtinov diffraction pattern of stars for accurate focusing in the dark moonless night. I prefer manual focussing.)

After reading multiple reviews, I have realized that Fujifilm GFX 50S wins over Pentax 645z in the following:

Tilting screen to all angles (which I need for astro)

Pixel size little larger (So theoretically higher resolution and lesser noise for longer exposures in the range of 30-60 sec)

Weighing much lesser (mirrorless)

Have you used the 50S in the extreme low light conditions. If yes, then can you share your personal experience.

Thank you once again.

 

[Parag Shankar]

Hi John,

Awesome image of Orion Nebula. I am researching for a new set up for my astrophotography. (Existing I have Canon 60D and 200L on a motorized mount of SkyWatcher)

After reading many reviews on 645z and GFX 50S, I believe the Fuji wins over due to the following:

1. Modern sensor (645z was released 3 years before?)

2. Little larger pixel size (So better resolution and lower noise)

3. Fully flexible LCD screen which I need for Astro

How you compare 50R with the above especially with the LCD Live View zoom magnification? My Canon zooms digitally the Live View by 10x.

How you focus in the dark night?

Your experience will really help me, especially with Fujifilm MF camera.

Thanking you

Parag

 

[Parag Shankar]

The Great Orion Nebula M42 in Monochrome mode, Canon 60D APSc sensor with 200L.

The Great Orion Nebula with my existing set up. Canon 60D with 200L. 25-30-35 sec exposures stacked. No dark frame or bias frame subtraction. No further processing.

Monochrome mode.

Parag .

 

[NancyP]

I haven't seen a lot of work with MF on landscape, planetary, or deep space object astrophotography. Michael Reichmann of Luminous Landscape tried the Pentax 645Z https://luminous-landscape.com/pentax-645z-astrophotography/ and other articles, but he is deceased.

What is your interest? Landscape, planetary, DSO? I assume you have a good tracker / equatorial mount already, and one or more telescopes.

Have you checked Cloudy Nights AP subfora for medium format users? Astrobin?

 

[NancyP]

Splendid image there!

 

[NancyP]

If so, you aren't limited by the type of live view magnification. Plus, easier mount control.

BTW, if you modded your 60D for Ha, would you recommend the company that did the mod? I have been thinking of modding my 60D for full-spectrum, filter use only (UV project)

 

[JimKasson]

Dear Jim,

Thank you for your response to my relatively naive queries...

I refined my queries here:

In Astro work, I need to zoom the "live view" which is seen at the back LCD screen. Does Fujifilm GFX 50S LCD has a zoom feature?

Yes.

(My existing Canon 60D does it with 10x. I need to to check the Bahtinov diffraction pattern of stars for accurate focusing in the dark moonless night. I prefer manual focussing.)

I find focusing on a point source difficult, especially a dim one. If I would you, I would find an easier-to-focus target at sufficient distance, and focus on that.

After reading multiple reviews, I have realized that Fujifilm GFX 50S wins over Pentax 645z in the following:

Tilting screen to all angles (which I need for astro)

Pixel size little larger (So theoretically higher resolution and lesser noise for longer exposures in the range of 30-60 sec)

For the same objective lens, the resolution in cycles/mm will be less on a sensor with a coarser pitch.

Weighing much lesser (mirrorless)

Have you used the 50S in the extreme low light conditions.

Only for testing.

If yes, then can you share your personal experience.

As the light gets dimmer, the EVF experience gets worse. I would much prefer parallax focusing (looking at an aerial image and moving your head) if I were doing this.

Are you using parallax focusing on your Canon? If the sensor and the crosshairs are aligned properly, that's the gold standard, I think.

Jim

 

[Parag Shankar]

Dear Nancy

Thank you for your comments..

Here is the link to mode your camera:

Loading…

www.imaginginfinity.com

I paid some $ 350 for the operation! But great work by Hap Griffin.

Thank you.

 

[Parag Shankar]

Not much on Cloudy nights subfora on MF AP. I am member of it.

May be very few people can afford MF for AP along with its expensive lenses....

I think so.

Thank you.

 

[Parag Shankar]

Dear Jim

Thank you very much for your advise.

May I ask:

How to check whether the sensor and the cross-hair on the LCD are aligned properly? Is there a brief article? (I would like to perform it on my Canon 60D)

Can you let me know the digital zoom (10x or more) on the "Live mode" please? For the models:

• Fujifilm GFX 50S MF
• Pentax 645z MF

(I couldn't get it on the web)

Thank you.

 

[JimKasson]

Dear Jim

Thank you very much for your advise.

May I ask:

How to check whether the sensor and the cross-hair on the LCD are aligned properly? Is there a brief article? (I would like to perform it on my Canon 60D)

I'm sorry I don't. And, although I did this many years ago, I can't remember the details. But here's something that should be a crude measure. Focusing by parallax, make 16 exposures of a star bright enough that you can expose to just below clipping at a short shutter speed. Examine them. Is the average image sharp?

Can you let me know the digital zoom (10x or more) on the "Live mode" please? For the models:

• Fujifilm GFX 50S MF

I don't know what the max focus magnification is. 10x sounds about right.

• Pentax 645z MF

Never used one. Sorry.
Jim

 

[Pedro Oliveira]

Hi John,

Awesome image of Orion Nebula. I am researching for a new set up for my astrophotography. (Existing I have Canon 60D and 200L on a motorized mount of SkyWatcher)

After reading many reviews on 645z and GFX 50S, I believe the Fuji wins over due to the following:

1. Modern sensor (645z was released 3 years before?)

Both cameras have the same Sony sensor.

2. Little larger pixel size (So better resolution and lower noise)

Both cameras have the same sensor thus the same pixel size.

3. Fully flexible LCD screen which I need for Astro

Both cameras have the same external LCD orientation skills but the Fuji can tilt to the right also.

How you compare 50R with the above especially with the LCD Live View zoom magnification? My Canon zooms digitally the Live View by 10x.

The Pentax 645Z in Live View has 16x.

How you focus in the dark night?

Your experience will really help me, especially with Fujifilm MF camera.

Thanking you

Parag

 

[Parag Shankar]

Thank you very much. Best Wishes.