Some HHHR Astro shots with the 75mm f1.8 and OM-1 - Lyra and Andromeda

[BDennis]

We had a clear night on July 27th/28th so I set up to try my 75mm and OM-1 for some astrophotography with a few targets in mind. After a short time so clouds rolled in but I got a few shots.

Constellation of Lyra - processed with OM Workspace to TIF then some more work in CaptureOne Pro


Constellation of Lyra by Bill Dennis, on Flickr

Same shot, processed with DxO PR + C1 Pro and cropped it. The Ring Nebula M57 it visible as a small turquoise / blue dot between the bright lower stars
Constellation of Lyra by Bill Dennis, on Flickr

Lyra shot plate solve showing the position of M57


The curved line of dots in this image is a HHHR artefact. I think a bright pixel caused this, there are 12 dots one for each sub-image. The HHHR alignments causes the hot pixel to be in a different position in the final output. Curiously they have different spacing and are not in a straight line, I'm not sure what we can deduce from this - the sky is rotating for one thing and star alignment is happening. Also the timing of the HHHR 12 shots may not be at equal intervals perhaps?



A bit more exciting, the Andromeda Galaxy was up next...

Full frame processed to TIF in OM Workspace then more PP in C1Pro
Andromeda Galaxy by Bill Dennis, on Flickr

This is the same shot cropped and processed to bring out more detail I processed this to TIF in DxO PureRaw then loaded into the free Siril astro package to do some photometric colour correction and "stretching" of the levels.
Andromeda Galaxy HHHR - PP With Siril by Bill Dennis, on Flickr

This is a plate-solve in Siril of the above Andromeda cropped image:


I found some more HHHR pixel artefacts in the full Andromeda HHHR images. Look how the lines of 12 coloured dots are all the same curved snake shape, it's surely got to be the way hot pixels come out in the HHHR final image with the star alignment going on. I need to run the dead pixel re-mapping function on my OM-1!


Bill

[Ian]

Wow - that's excellent, thanks Bill. Which resolution setting did you use and what was the exposure/ISO?

Did you use mechanical or silent shutter (does it make a difference?) Dark frame noise reduction only seems to work if you use mechanical shutter mode.

Ian

[blu-by-u]

No dark frames deductions in Silent So I have been sitting there waiting for no reason

[wornish]

Excellent star detail and no trailing.

Stacking lots of images makes a massive difference when targeting faint objects.

I posted this image of Andromeda on here last year, taken with my OM1 and 40-150mm. Using the zoom lens also makes finding your target a lot easier and then centering it and zooming in.

https://www.e-group.uk.net/forum/forum/show-your-photos/foto-fair/astro-photography/993559-another-go-at-andromeda

[BDennis]

Thanks Dave.

A great image you got last year - somehow I missed your post at the time.

I must try my 40-150 f2.8 again for some deep sky objects, I got the 75mm f1.8 for wider field astro when I saw a deal on it - it's really a portrait lens! Actually I think the 75mm has some quite noticeable coma wide open.

Bill

[BDennis]

Wow - that's excellent, thanks Bill. Which resolution setting did you use and what was the exposure/ISO?

Did you use mechanical or silent shutter (does it make a difference?) Dark frame noise reduction only seems to work if you use mechanical shutter mode.

Ian

Thanks Ian. I use the 50Mp HHHHR mode resolution which is the maximum in case I want to crop the images.

Exposures were 3.2 seconds, f1.8, ISO 3200 for the Lyra shot and 2 seconds, f1.8, ISO 6400 for the Andromeda shot.

The high res modes are silent shutter only, so no dark frame subtraction.

Oddly, live composite mode another computational mode I use for astro shots always uses mechanical shutter and does support dark frame noise reduction, not sure why - maybe I'm missing something.

BIll

[Ian]

I couldn't get higher than ISO 1600 with the Tripod Mode Hires shot - I will have to check how HHHRES works.

[BDennis]

Ian - It's a restriction of the tripod Hi Res mode that you can't go higher than 1600 ISO. With hand held Hi Res mode you have the full ISO range. I never found anything in the manual about this, just through experimentation!

This might be of help - Thomas Eisl has a short guide on the high res modes to go with a video he had about it

https://thomaseisl.photography/technique/om-system-om-1-high-res-shot

This is the video

[blackfox]

wow that's something else bill