Orion nebula with zoom lens

[Jim Smith]

I know that zoom lenses are considered a compromise compared to telescopes. However, I closed the aperture down a bit and got better results than I usually do. Interesting diffraction spikes on the brightest stars.

Nikon D5500, Sigma 120-300mm f/2.8 @ 300mm f/4.0, 60x30s, ISO 400

SkyWatcher AZ-EQ5, Affinity Photo, Astroflat Pro, Topaz De-noise

Edited March 9, 2021 by Jim Smith

[shropshire lad]

Thats a great result  Jim, are you sure it was f4, don't usually get spikes  ...... any filters used and you must be in a quite dark sky area?

Did you have to crop the image to get this?

 

 

Edited March 11, 2021 by shropshire lad

[Jim Smith]

Thank you.

Yes, it was f/4.0. I had previously done a comparison of f/2.8 and f/4.0 with this lens. Pictures below...everything the same except for focal ratio. I didn't like the asymmetric, blobby stars I get at f/2.8. f/4.0 has diffraction spikes but I don't mind those so much! I raised the exposure of the f/4.0 photo in post to make the comparison easier so it's a bit noisier.

No filters...just the D5500 directly on the back of the lens.

Clear Outside says I'm Bortle 4. Yes, it was cropped.

Third image below shows full field of view captured.

[shropshire lad]

Ok thanks Jim for the reply ... think I will try f4 next time I'm out as I agree and get blobby stars myself @ f2.8 and f3.2 .... may even try f5.6

 

 

[Jim Smith]

I would be interested in any findings from your experiments. 🙂

[shropshire lad]

41 minutes ago, Jim Smith said:

I would be interested in any findings from your experiments. 🙂

Ok will do ... have you done any tests for the best ISO to use, I'm never really sure what is best.

I saw a list somewhere online for best Iso for different cameras but can't find it now?

 

[alacant]

8 hours ago, Jim Smith said:

f/4.0 has diffraction spikes

Hi

Lovely shot and good to dispel some of the myths surrounding zoom lenses when used for astrophotography.

A 105-75mm step down filter ring (or a cereal box) will give you f4. With the lens set at f2.8, the diaphragm will be masked, thus giving spike free stars. Not sure if they'll hold up the toward the corners of the frame though.

Cheers

Edited March 11, 2021 by alacant

[BCN_Sean]

A few diffraction spikes don't take away from the overall image there!

[Cobberwebb]

I've been having good results with my kit zoom lens (Nikon Z50, 50-250mm F4.5-6.3).
I'm fairly new to this, so I'm excited to get a dedicated astro lens. Would something like the ZenithStar 61 be really good?

Edited March 11, 2021 by Cobberwebb

[Jim Smith]

2 hours ago, shropshire lad said:

Ok will do ... have you done any tests for the best ISO to use, I'm never really sure what is best.

I saw a list somewhere online for best Iso for different cameras but can't find it now?

 

I've not done any formal testing but I understand that the sensor in my D5500 is "ISO invariant" so I have been using anything from ISO 200 to 1600 and increasing the exposure in post if necessary.

try this... https://dslr-astrophotography.com/iso-dslr-astrophotography/

[Jim Smith]

3 hours ago, alacant said:

A 105-75mm step down filter ring (or a cereal box) will give you f4.

That's an interesting idea. I might try that.

EDIT: Just ordered a 105mm to 77mm step down ring from ebay.

Edited March 11, 2021 by Jim Smith

[shropshire lad]

1 hour ago, Jim Smith said:

I've not done any formal testing but I understand that the sensor in my D5500 is "ISO invariant" so I have been using anything from ISO 200 to 1600 and increasing the exposure in post if necessary.

try this... https://dslr-astrophotography.com/iso-dslr-astrophotography/

Yes Jim that's the list ... and apparently my Canon 80D is also ISO invariant ....