What is possible with short exposure (and good weather)

[Jean-Francois]

Hello,

Yesterday evening, I did some tests with my mount (other topic about the MoveAxis command).
I remarked that the sky was very good ... and so it was my first observation of this year.

I like the simplicity ... today SharpCap allows to have good result with low workload.
I did no guiding, no dark, no flat, no long processing (only adjust the image in PaintShop Pro 7).
I only used the automatic removal of the hot/cold pixel in SharpCap.
The individual images are between 10 and 30 seconds and the stacks were (only !) 10 minutes (two images with 5 or 20 minutes).

Here the list of the targets:
Ae and Phi Aur region, IC444 (two parts), M1, M35, M37, M51, M63, M81, M82, M94, M95, M97, M97, M101, M106, M109, NGC2175, NGC2683, NGC2903.

Equipment:
Newton FD4 with ASA reducer/corrector to FD 2.9 mounted on EQ8R-h mount.
Camera QHY174GPS cooled at -30°C.

Newton_2025-30-02_a.jpg (851.58 KiB) Viewed 1467 times

Newton_2025-30-02_b.jpg (629.13 KiB) Viewed 1467 times

Regards,
Jean-Francois

[admin]

Hi Jean-Francois,

a great collection of images for just one evening's imaging You really have taken advantage of the fast f-ratio and the sensitivity of the monochrome camera there.

I quite often image in a similar way - no darks, no flats, no guiding, hot/cold pixel correction and 10 to 30s exposures going into live stacking - nice and easy!

cheers,

Robin

[Jean-Francois]

Hello,

Thanks.
My goal was not to have the deepest image with hours and hours (or nights).
The first image stack was done at 21:24 and the last image stack at 02:10. In total it was 22 targets.

Here again some of the target without pixel scaling. The relative size between the objects are conserved.
It is clear that the images could have a better processing.
But again ... no dark, no flat, it is the PNG generated by the Live Stacking of SharpCap.
Only a little brightness/contrast adjustment between the images.

Newton_Zoom_2025-30-02.jpg (412.92 KiB) Viewed 1301 times

Regards,
Jean-Francois

[timh]

Hi Jean-Francois. That's great. Actually -as an astronomer viewing in the pre-camera era - my aim was just the same - to get good views of as many interesting objects as possible in the course of a night. Moving on to EEA it was the same - and as your pictures demonstrate- it is now possible to get actually very good images within 20 min or so so and get through a lot within a few hours and end up with some good images to keep too. Over the years though I have been sort of seduced into astro-imaging - imaging the same object night after night just in the hope of getting enough frames to build a really good image of one object. But occasionally I do like to do what you have and simply scroll through and just take a look at many objects -- even had the eyepieces out again a few nights ago -- which was good but also reminded me of why I moved over EEA in the first place. Tim

[Jean-Francois]

Hello Tim,

Thanks.

I do rarely a visual observation. It is fast impossible with the Newton mounted on the EQ8 mount.
The focuser is oriented to the mount side and I do not want to dismount the camera setup or rotate the tube.
I can install the mobile mount outside with a different telescope ... but not every night.
Ideally would be to have a big (all weather) Dobson ready on the terrace ... but only if all my neighbours will move away.

Regards,
Jean-Francois

[takuya_t]

Hi Jean-Francois & all,

Wonderful images!
This is exactly what I aim for. For DSOs, I also enjoy observing about 10 to 20 objects in a night, with exposure time about 15 to 30 minutes per object. SharpCap is the best tool for this purpose. Regarding the final images, I think the "Time Performance" of SharpCap's live stacking is excellent compared to thoroughly post-processed images. (The difference is not as significant as the difference in time spent)

Here are some questions for everyone, and I would greatly appreciate any advice or comments on the following:
"To take the best possible astrophotographs while enjoying EAA." This is my goal.
But I always struggle with the appropriate exposure time & gain & offset settings for each object.
With the settings recommended by Brain, it seems to take a long time for Live Stack to appear clearly, so I always set a higher gain than that
Basically, I decide the exposure time and gain based on the following considerations, but are there any ideas that need improvement?

・The exposure time is generally 10 to 30 seconds, and set the gain so that the histogram takes correct shape.
If the left end of the histogram is cut off with a 30-second exposure using a strong filter like DBP,
I extend the exposure time further to prioritize the shape of the histogram.
・The histogram shape meets the conditions listed in the SharpCap manual.

＜Equipment＞Camera…533, Mount…AVX For nebula… SkyWatcher Evoguide50EDⅡ/ F5（mainly use)
　　　　　　 For galaxies… SkyWatcher Mak127 with 0.7x reducer / F8 ※The Mak127 is not suitable for EAA, but it's the only one I have for now...

Thanks in advance.
Takuya

[Jean-Francois]

Hello Takuya,

I think that the seek of the best settings for the best image will be like the perpetual momentum ... never happen.

But we can try ... the SharpCap Sensor Analysis is a good start. The next is experience.
But, some day you will have new software or new camera technology (see the big step between analogic and digital sensor, and the change from CCD to CMOS) ... and we restart the discussion

It is not only the camera exposure or other camera settings.
All are modified with different extern conditions ... sky and target.

Now with your equipment F#6 or F#8 needs relative long (single and total) exposure.
Compared to my images here with F#2.9 or alternative with an RASA at F#2. That make a big difference.
Some nights I overexposed my QHY168 with the RASA8 with 30s exposure.

Regards,
Jean-Francois

[takuya_t]

Hi Jean-Francois,

Thank you for your kind response.
Indeed, there are various factors beyond just the choice of telescope and camera settings. To adapt to these, experience is crucial.
I have always loved space and studied astronomy, but I have only been doing astronomical observations for about 1.5 years.
I think I have grasped the basics to some extent, but there are still many moments where I think, "Huh? This isn't going as planned "
It's a deep and challenging world.
However, when I actually capture celestial objects with EAA, the knowledge I've gained in the past connects with the image in front of me,
and my mind overflows with information. Including that, it's incredibly enjoyable.

I would appreciate your continued advice!!

I am considering introducing a telescope with a smaller F-number in the near future.
I'm thinking around F3, and I believe it will significantly change the EAA environment, so I'm looking forward to it

Regards,
Takuya