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tooth_dr

First light - M51 M101 widefield - star shapes odd?

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A very short first light, but I really wanted to try out the camera and lens under the stars.

5 x 60s IOS1600 Nikon D800E and Nikkor 180mm F2.8 lens.

@davew tagged as promised lol

 

Would anyone mind having a look at the star shapes, esp the bottom right quarter of the image.  I'm new to imaging with a camera lens.

Do you think the focus would have the effect on the stars shapes that is seen here?  I tried stopping down the lens, right to F22, and the shapes on the bottom right stars was still there, but lesser.

The CA is more than I would have expected too, but again maybe this is normal at F2.8 and with this type of lens.

I don't mind if this is what to expect, just want to make sure the lens is ok, as it was expensive.

 

(I'm going to need a new PC too, my laptop struggled even just opening the massive RAWs, let alone processing 5 subs.  I plan to do some mosaics so that will really test the CPU.

 

Thanks!

Adam

 

 

 

St-med-300.0s-NR-x_1.0_LZ3-NS-full-qua-add-sc_BWMV_nor-AA-RL-noMBB-St.jpg

St-med-300.0s-NR-x_1.0_LZ3-NS-full-qua-add-sc_BWMV_nor-AA-RL-noMBB-St-1.jpg

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Posted (edited)

I had the same lens and the same issue. I was however using a Canon 450d with it. Even at f5.6 i had problems. This lens gets rave reviews for astrophotography on the web. I sent mine back to the seller on Ebay and replaced it with a Canon 200 mm f2.8 USM which i`m over the moon with. 

I don`t think your problems are as bad as mine though. Over half the frame was unusable. I think an element was misplaced

Alan

Edited by Vixen4eva

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1 minute ago, Vixen4eva said:

I had the same lens and the same issue. I was however using a Canon 450d with it. Even at f5.6 i had problems. This lens gets rave reviews for astrophotography on the web. I sent mine back to the seller on Ebay and replaced it with a Canon 200 mm f2.8 USM which i`m over the moon with. 

Alan

Thanks Alan. What do you think I should do here? 

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Posted (edited)

According to most users on the net this lens should be usable @ f4. I`ve seen some great images taken with them!!! I assume this is the Nikon 180 f 2.8 ED? Mine was the slightly newer version. Are you using stop down rings i don`t see any diffraction spikes?

Alan

Edited by Vixen4eva

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20 minutes ago, Vixen4eva said:

According to most users on the net this lens should be usable @ f4. I`ve seen some great images taken with them!!! I assume this is the Nikon 180 f 2.8 ED? Mine was the slightly newer version. Are you using stop down rings i don`t see any diffraction spikes?

Alan

Thanks Alan. This was taken at F2.8, fully open.  I think this is the new version too? Autofocus and aperture control work with my camera.

 

 

53006301-8DE1-4568-8431-279D693C4427.jpeg

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I've downloaded the bottom image and yes, I do see CA. I think that's a combination of the age of the design and the f 2.8. That amount of CA wouldn't put me off as it would disappear with processing.

The stars don't look great all along the bottom and not just in the bottom right. Happy-cat has a diagram of where to focus and if it was me I'd try focus finesse first. That would mean putting the focus star about half way between the centre and bottom right corner. That has the effect of reducing field curvature within the lens. ( Apparent )

Most of the reviews you see on both the Canon lens and this Nikon lens are done with APSC cameras. That may indicate that both lenses would struggle with FF. I used mine at f 2.8 but as I said, up to now, I've not used it with an FF camera. I must try it as I know the corner stars are good with what I have used up to now. I saw one reasonably good astrophotographer who reviewed this lens mounted on an APSC Canon !

When using an EQ mount, as Alan said, these lenses tend to be used at F4. I didn't.

Bottom line ... no matter if you have the finest example of this lens or not, if it doesn't please you then send it back if you can. Do try and find the best focus point and focal ratio first though.

Dave.

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Hi Adam, I’m no expert but the big bright star top left doesn’t look very good to me, particularly if I zoom in. I’d hope it would look more round at F4 or F5.6, although I’m not sure what to expect from this lens. Hope you get some more feedback from others. 

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Thanks guys for the great responses.

@davew I’ll try to find the info by @happy-kat about focusing. I did focus not in the centre but It wasn’t at the bottom right. Would you mind marking when I should place the star when focusing please?

This lens isn’t supported by a bracket. Would that possibly cause an issue? I just attached a dovetail bar to bottom screw and placed it onto a clamp on a homemade rig  

 

1A329819-8514-4A25-B87A-C54E7359D807.jpeg

BE35EC97-52FC-42BC-AF80-821A0F2B4013.jpeg

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38 minutes ago, tooth_dr said:

Thanks guys for the great responses.

@davew I’ll try to find the info by @happy-kat about focusing. I did focus not in the centre but It wasn’t at the bottom right. Would you mind marking when I should place the star when focusing please?

This lens isn’t supported by a bracket. Would that possibly cause an issue? I just attached a dovetail bar to bottom screw and placed it onto a clamp on a homemade rig  

 

Try these positions for focus. This applies to more or less all lenses and scopes that don't use a field flattener, not just this lens.

301673013_focuspoints.thumb.jpg.49f8835a84f3be8fd4c86f63e7882522.jpg

 

I don't think the lens should require a full supporting bracket. On a genuine body it either works or doesn't as it's not that long or heavy.

As for the top left star, I've seen quite a few lenses do this from all makes. Some would suggest trying a step down ring.

I have to say that it's a bit disappointing to see !

Dave.

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27 minutes ago, davew said:

Try these positions for focus. This applies to more or less all lenses and scopes that don't use a field flattener, not just this lens.

301673013_focuspoints.thumb.jpg.49f8835a84f3be8fd4c86f63e7882522.jpg

 

I don't think the lens should require a full supporting bracket. On a genuine body it either works or doesn't as it's not that long or heavy.

As for the top left star, I've seen quite a few lenses do this from all makes. Some would suggest trying a step down ring.

I have to say that it's a bit disappointing to see !

Dave.

Thank you. 

Its looking partially clear tonight, so I’ll try this. 

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This is one of my images taken with a modded 450D..... One side looks in focus the other side isn`t. This was @ f5.6

NAN 171018 Nikon 180 ED f5.jpg

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Focus where a third intersects spreads focus better then using the centre for stars.

IMG_20180122_202713.JPG.6c8f515f7b61b0a9c110adc272b93505.JPG

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Something I never knew.  We are all constantly learning in this hobby...

Alan

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It was a tip given by a member on here who is well respected for his photography.

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You might have an issue with this specific lens, or maybe not. 

To me it seems there is some tilt in the System, maybe in the lens, or in the sensor (which is what i have in my Canon 600d): maybe it's there with shorter lenses too an you just don't see it? 

I'd try to stick some scotch tape on the bottom of the bayonet and take another shot @ f2. 8, high ISO, focusing at centre. Look whether it gets better or worse. If worse stick the tape on the bottom and retry. 

If nothing changes, your issue can't be solved by this Simple trick. 

No sense in stopping down to f22, diffraction steps in. 

Try some real subs at f4 and decide whether you can live with it or not! 

Good luck, 

Fabio

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32 minutes ago, happy-kat said:

Focus where a third intersects spreads focus better then using the centre for stars.

IMG_20180122_202713.JPG.6c8f515f7b61b0a9c110adc272b93505.JPG

Not to be used when cropping, because sharpness is degraged at centre, through. 

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Depends how heavy you know you will crop by and whether you have a tracking mount.

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Hi Guys

There was again a very brief clear spell between clouds and heavy downpours, I nearly got caught out too, managed to slide the roof over quickly.

 

Here are the images from this evening.  I will be very grateful if anyone could cast their eye over the images.

First one is 120s F2.8

Second one is 120s F4.0

ISO200_120s_F2-8.thumb.JPG.aae8b8338d3f761cae65bb204682e253.JPG

ISO200_120s__F4.thumb.JPG.fd87b66d8110a178d8cb71bbdd851775.JPG

I focused at the bottom right as you view the image, as per the green circle placement above.

I think it looks better.  I was guiding well this evening at 1 arc-sec/px.  There is still some distortion, but it seems more evening spread throughout the frame.

 

I also took the camera out with the kids today, and it seems like a nice lens to a non-photographer such as myself.

DSC_1414_1.thumb.jpg.f50852105cfd04853551ad09317c846b.jpg

DSC_1416_1.thumb.jpg.b4c3c3a98df11037e0602bd25d8c305d.jpg

DSC_1441_1.thumb.jpg.f0ca82bb9584839e882fda560e534813.jpg

 

 

 

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This is way better than mine!! I think mine was tilt if I'm honest due to it being a Canon body but I'm happy enough with the 200 mm for 2.8 I replaced it with....

Regards 

Alan

I'm no expert but I could live with it!

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Nice Adam, what mount were you using for the astro images?

I'm not into AP but I looked at the second image on a my large hi-res monitor and zoomed in.

The stars around the central bright star with the diffraction spikes, zoomed in look like a hot air balloon rally from a distance. (they seem to be just that shape with basket off the bottom).

I have no idea what causes this or how to address it.

Your kids look happy.

Maybe look at stopping down for dof and AF Point (1&3).

PS love the hats. :)

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2 hours ago, RichM63 said:

Nice Adam, what mount were you using for the astro images?

I'm not into AP but I looked at the second image on a my large hi-res monitor and zoomed in.

The stars around the central bright star with the diffraction spikes, zoomed in look like a hot air balloon rally from a distance. (they seem to be just that shape with basket off the bottom).

I have no idea what causes this or how to address it.

Your kids look happy.

Maybe look at stopping down for dof and AF Point (1&3).

PS love the hats. :)

Thanks Rich

I'm using a Skywatcher EQ6, which was autoguided - overkill to the max for the lens.  

The second image in the first post was one where I focused in the middle.  I then went back and took more images, focusing as per the guidelines above.  These are the 'bluer' images above.  The starry artefacts looks lessened in these ones, but I can see what you mean about small tails on the stars in the top images.

Forecast not looking great for the next 10 days.

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Is it fair to say that the lens isnt a new design, and the camera is particularly high resolution with no AA filter and 36MP, so some artefacts are expected!

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I had a quick run on Thursday night with the lens/camera.  11 x 150s, no flats or bias.

I'm happy with this, and it's looking clear tonight too so going to give it some more testing!

 

Cass_Wide.jpg

Cass_Wide_Small.jpg

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