35 replies to this topic

[Daniel Dance]

Here is a single panel image of the Witchhead nebula region in the constellation of Eridanus captured with a Sigma ART 85mm. 

 

I'm really loving this lens this year.  I have previously imaged with three (3) Rokinon 135mm rigs, but I'm finding the 85mm to give a bit more field, especially for doing larger mosaics.

 

Sigma ART 85mm F1.4

ASI2600MC

60 x 180s exposures @ f2.8

Nightfall Astro Ring Platform for Sigma 85mm

ZWO AM-5 Mount

 

 

Ghastly Pillars and the Witch Nebula Widefield by Daniel McCauley, on Flickr

[Jlex]

Awesome job!  The Sigma Art series of lenses are incredible.  I'm working on a project using the 24-70 mm, I'm very happy with the subs so far.  Dang thing cost more than my telescope 

[Stevemr2t]

Jaw dropping 

[Daniel Dance]

Thanks so much!  This 85mm lens is becoming my new favorite imaging instrument!

 

Daniel

[whwang]

The quality is amazing, especially given the short integration of just 18 minutes.

 

That being said, the camera you use doesn't seem to fit this particular forum.  The quality of your image definitely belongs to the "experienced" forum.

 

May I also ask how did you stop down the lens to F2.8?

[Daniel Dance]

The quality is amazing, especially given the short integration of just 18 minutes.

 

That being said, the camera you use doesn't seem to fit this particular forum.  The quality of your image definitely belongs to the "experienced" forum.

 

May I also ask how did you stop down the lens to F2.8?

Thanks for the kind words.
Yeah, I agree, it could probably fit the Advanced Imaging section, but I included it here since its using a standard camera lens and not a specialized astrophotography instrument like a refractor, etc...

 

Not sure where you're getting 18 minutes from.  This was 60 x 180s, which is 180 minutes or 3 hours total.

 

The lens was stopped down using the variable aperture of the lens.  The aperture can be adjusted from F1.4 through F16.

[savitar]

Thanks for the kind words.
Yeah, I agree, it could probably fit the Advanced Imaging section, but I included it here since its using a standard camera lens and not a specialized astrophotography instrument like a refractor, etc...

 

Not sure where you're getting 18 minutes from.  This was 60 x 180s, which is 180 minutes or 3 hours total.

 

The lens was stopped down using the variable aperture of the lens.  The aperture can be adjusted from F1.4 through F16.

Great Photo, Im looking forward to buy one these Art series.

 

I think what whwang was trying to ask is How did you stop down when you connect the lens to a CCD since there is no direct control of aperture. One way is that you can hook it up to a DSLR in manual mode, set it to the desired F number, hold down the DOF preview button, then disconnect the lens while holding down that button, another way that maybe step down rings https://www.amazon.c...m/dp/B0012FMX34

[Daniel Dance]

Great Photo, Im looking forward to buy one these Art series.

 

I think what whwang was trying to ask is How did you stop down when you connect the lens to a CCD since there is no direct control of aperture. One way is that you can hook it up to a DSLR in manual mode, set it to the desired F number, hold down the DOF preview button, then disconnect the lens while holding down that button, another way that maybe step down rings https://www.amazon.c...m/dp/B0012FMX34

That is an excellent question.

The easiest and most reliable method is using a DSLR as you describe.  I've done this once over a year ago, have used the rig hundreds of times, and never had it reset on me.

 

There is also an electronic adapter which you can put in line that will do this automatically and can be controlled through ASCOM.

[whwang]

Thanks for the kind words.
Yeah, I agree, it could probably fit the Advanced Imaging section, but I included it here since its using a standard camera lens and not a specialized astrophotography instrument like a refractor, etc...

 

Not sure where you're getting 18 minutes from.  This was 60 x 180s, which is 180 minutes or 3 hours total.

 

The lens was stopped down using the variable aperture of the lens.  The aperture can be adjusted from F1.4 through F16.

Sorry.  My brain was't clear.  It's 180 minutes, not 18 minutes.

 

So the lens you used has an aperture ring?  Which mount is it?  I had the Nikon F mount version of this lens, and it doesn't have an aperture ring.

[Paulimer]

Hi! How do you connect the lens with the 2600MC?

[Daniel Dance]

Hi! How do you connect the lens with the 2600MC?

That's a great question.

ZWO sells several different Canon adapters.

 

1.  Canon adapter with 2" filter drawer built-in

2.  Canon adapter - standard - no filter  (If you're not using filters, buy this one)

3.  Canon adapter for use with ZWO 2" filter wheel - use if using RGBHa filters, etc....

[Paulimer]

That's a great question.

ZWO sells several different Canon adapters.

 

1.  Canon adapter with 2" filter drawer built-in

2.  Canon adapter - standard - no filter  (If you're not using filters, buy this one)

3.  Canon adapter for use with ZWO 2" filter wheel - use if using RGBHa filters, etc....

Thank you. I'm trying to find an M54 connection because I will be using the 2600Air for trips. 

[BQ Octantis]

Bewdy!

[nhmorgan79]

That's a great question.

ZWO sells several different Canon adapters.

 

1.  Canon adapter with 2" filter drawer built-in

2.  Canon adapter - standard - no filter  (If you're not using filters, buy this one)

3.  Canon adapter for use with ZWO 2" filter wheel - use if using RGBHa filters, etc....

Great work!! This is an awesome image!

 

Note to add for the poster who asked the question: you also need to attach the lens to the DSLR camera and set the aperture then disconnect it while the camera is still on. This "freezes" the aperture for use with the ZWO camera. 

[Daniel Dance]

Thanks so much!

[akdwivedi]

its an amazing pic.. would you also show a picture of your rig. did you get some sort of mounting ring to mount the guide scope.

[Daniel Dance]

its an amazing pic.. would you also show a picture of your rig. did you get some sort of mounting ring to mount the guide scope.

Thank you for the kind words.

 

Great question.  I'm using the Nightfall Astro ring platform system for mounting of the Sigma 85mm, guidescope, and NINA miniPC.  This is a really nice mounting system.

I also am using their 50mm ring platform.

 

Here is the link to their website.

https://nightfallastro.com/

 

Thanks for looking - glad you liked it!

[desmc]

Here is a single panel image of the Witchhead nebula region in the constellation of Eridanus captured with a Sigma ART 85mm. 

 

I'm really loving this lens this year.  I have previously imaged with three (3) Rokinon 135mm rigs, but I'm finding the 85mm to give a bit more field, especially for doing larger mosaics.

 

Sigma ART 85mm F1.4

ASI2600MC

60 x 180s exposures @ f2.8

Nightfall Astro Ring Platform for Sigma 85mm

ZWO AM-5 Mount

 

 

Ghastly Pillars and the Witch Nebula Widefield by Daniel McCauley, on Flickr

Fabulous image - congratulations.

 

I have a more or less identical rig using the ZWO filter drawer for EOS.

I am trying to tune the back spacing with M42 spacer rings camera side.

 

Do you have any pointers please - e.g. optimum f stop/ spacer combo.

I've started with f2.8 and 0.5mm spacer in combination with a Baader L filter.

I realise that the 2600MC has a uv/ir cut window - it's just that I might want to use a dual band filter so want to minimise the messing around with back focus.

 

Thanks in advance.

 

Des

[Tulsa]

Since I already own the Sigma Art 85mm, I now have one more item to add to my ever growing list of things I’d like to buy.  

 

Thanks for posting this. 

[Daniel Dance]

Fabulous image - congratulations.

 

I have a more or less identical rig using the ZWO filter drawer for EOS.

I am trying to tune the back spacing with M42 spacer rings camera side.

 

Do you have any pointers please - e.g. optimum f stop/ spacer combo.

I've started with f2.8 and 0.5mm spacer in combination with a Baader L filter.

I realise that the 2600MC has a uv/ir cut window - it's just that I might want to use a dual band filter so want to minimise the messing around with back focus.

 

Thanks in advance.

 

Des

Thank you.  Great question.  If you're using the standard ZWO camera adapter with filter drawer, you don't need any additional spacers even when using filters.

 

Basically - ASI2600MC - ZWO adapter to Canon with Filter Drawer - Sigma 85mm ART

 

If you don't need a filter, ZWO also sells an adapter without the filter drawer.

 

The filter drawer is annoying since its only held magnetically.  I usually seal it with a piece of black electrical tape.

 

 

[desmc]

Many thanks.

I seem to have wonky stars in the corners even when stopped down to f2.8 and with 0.5 and 0.8mm spacers. The flying angel stars - for that is what they look like - point radially outward indicating perhaps that the camera needs to be moved back further. The aberration is worse than when attached to a dslr I think. Blurxterminator does a reasonable job of tidying things up.

Are your stars similarly affected?

Best, Des

[dan_hm]

Many thanks.

I seem to have wonky stars in the corners even when stopped down to f2.8 and with 0.5 and 0.8mm spacers. The flying angel stars - for that is what they look like - point radially outward indicating perhaps that the camera needs to be moved back further. The aberration is worse than when attached to a dslr I think. Blurxterminator does a reasonable job of tidying things up.

Are your stars similarly affected?

Best, Des

I've used fast lenses extensively with astro cameras.  Your problem could be with spacing, the Baader filter, the lens itself, or all three.  

 

Which DSLR did you test the lens with?  You'd want to see how it does with a 26MP APS-C DSLR.  The issue with putting something like a Canon 6D on it is the pixels of that sensor are huge compared to the 2600MC, so you're not really getting an accurate reading.  Normally, spacing is well configured between the DSLR sensor and the lens, so stars look better on the DSLR.  The problem with translating that to an astro-camera is that we're working with extremely fine scales here.  Even the thinnest Delrin spacer might be too thick.  Ideally, you'd want to use something like an Octopi or Photon Cage to dial in tilt and spacing within microns - which is the scale that this kind of adjustment demands.  Unfortunately, those are in the order of $500+ even if bought used, and you might just end up discovering that the issue is inherent to the lens and thus unfixable.  

 

Also, the Baader filter is 2mm thick, which is pretty much the upper limit for a fast lens.  Putting that much extra glass between the sensor and the rear element is bound to cause problems. 

[desmc]

Thanks for sharing your experience.
All sounds like good advice.
No substitute for taking a systematic approach to be sure.

I tested it on a canon 800d.
The corner stars were not great even at f2.8.
Thinking that the lens may not be the best of copies, although the other factors you highlight are more likely to be key. However there are only a few days left to return it so I might do that.

I know that when I tested my sigma 40mm the stars looked good on the dslr even wide open. When I switched to a 2600mc the quality of the stars dropped.

Cheers, Des

[dan_hm]

Thanks for sharing your experience.
All sounds like good advice.
No substitute for taking a systematic approach to be sure.

I tested it on a canon 800d.
The corner stars were not great even at f2.8.
Thinking that the lens may not be the best of copies, although the other factors you highlight are more likely to be key. However there are only a few days left to return it so I might do that.

I know that when I tested my sigma 40mm the stars looked good on the dslr even wide open. When I switched to a 2600mc the quality of the stars dropped.

Cheers, Des

Personally I’d return it. They don’t have great resale value.

[Daniel Dance]

Thanks for sharing your experience.
All sounds like good advice.
No substitute for taking a systematic approach to be sure.

I tested it on a canon 800d.
The corner stars were not great even at f2.8.
Thinking that the lens may not be the best of copies, although the other factors you highlight are more likely to be key. However there are only a few days left to return it so I might do that.

I know that when I tested my sigma 40mm the stars looked good on the dslr even wide open. When I switched to a 2600mc the quality of the stars dropped.

Cheers, Des

Can you post some samples of the images that show the coma?

 

Just remember that coma is going to exist on any optical instrument that has a curved lens.  You see it more in the corners because the corners are the farthest linear distance from center and coma is worst the farther from center you go - which is why we stop down the lenses to begin with, so we're not shooting through that curved region of glass near the edges of the lens.

 

But anyways, every lens will have coma to some extent.  I have three 85mm SIGMA ARTs, and they all have a small amount of coma in the corners.  I also have four Rokinon 135mm, and they have coma as well. 

 

In the end, if the photo looks good on the medium you are publishing or showing it on, that is all that matters.  

 

You can take a look at all my images with the 85mm on FLICKR.  Every one of those images has coma in the corners, but at the display size / resolution you can't see it.