Bode’s Galaxy and Cigar Galaxy using Star Adventurer mount

I continue to try and get the most out my 300mm PF lens on the Nikon J5 camera, since this combination allows reasonable images of DSOs as small as 10 arcminutes across – e.g. the Cigar galaxy. With the small plate scale of 1.63 seconds guiding is necessary on the Star Adventurer to achieve sufficiently low RA error.

A 77-62mm step down ring (equivalent to f/4.8) was used to improve star shapes obtained with the 300mm PF f/4. This seems to give much better star shapes than f/4 images (previously described – with some justification - as “horrible shapes”).

I tried (manual) dithering for the first time. If anyone knows how to get PHD2 to dither at regular time intervals without a link to the image camera (not possible on the J5) I’d be very pleased if you could let me know how to do it. Can this be done using AstroPhotographyTool ?

I used ISO 6400 (max analogue gain for the J5) in order to minimise the effective read noise (at ISO 6400 on the J5 read noise is 1.4 electrons). At ISO 6400, 30s and f/4.8 the histogram main peak was at 20%.

The 2x drizzle was used mostly for one point: to enhance the shape of the double star just above and to the right of Bode’s galaxy.



Equipment:

Nikon J5 Camera (1 inch 20MP sensor), 300mm PF f/4 lens, FT1 adaptor. Plate Scale 1.63 arcseconds / pixel. Star Adventurer Mount and Wedge. ZWO ASI 120 MM guide camera and 30mm mini guide scope

Imaging:

98 x 30s images, f/4.8 (using step down ring), ISO 6400. Polar alignment was done with PHD2 drift alignment and was within 5 arcminutes. Guided with PHD2 (RA tracking was about 2.3 arcseconds) and dithered after every frame (using PHD2 manual dither command). 60 Bias frames. Bortle 4 zone. Ambient temperature -2C

Processing:

All images converted to tiffs and stacked in DSS with 2x drizzle and Kappa Sigma stacking. Final adjustments and crop in Lightroom.

Regards,

Andy

Impressive work. I tried & failed to setup an auto guiding rig for my Astrotrac. I just couldn't find a way to connect the Synguider all-in-one camera. I was going to try a dedicated guide camera linked to PHD instead but it seemed too much trouble for a mobile rig.

Anyhow, right now I have an all new Fornax LighTrack 10 II, which is supposed to have excellent unguided tracking capabilities, so I will see how I go. I will use the supplied polar scope for the time being, but I may decide to adapt the Polemaster from my Astrotrac to fit the Fornax, if I think I need more perfect polar alignment, then I shouldn't really need to bother with auto guiding as long as I keep my subs at a max of 5 minutes with a small refractor.

Nice image by itself. Very nice image given your light setup!!!

I am the happy owner of a Nikon 300mm F4 PF which I dont dare use (!!) for AP given all the bad things I have read and heard about it.

If I understand you well, the 77-62mm step down ring reduces (or solves, according to your image) the problem with the shape of stars

Would you know if the step down ring can be used with a DX or a full frame Nikon camera ?

TIA

Breughel,

Thanks for your comments on the image.

The step down ring attaches to the lens filter thread as shown, so works with any camera. However, since the visible optical aberrations from the lens are much more severe away from the image centre, the step down ring will have most impact on images from large sensors - particularly in the image corners.



The f/4.8 equivalent setting with this step-down ring seems to work well when using the J5 with its 1-inch sensor. I plan to test it with an APS-C camera (Nikon D7100) next time there is some clear sky...

Most of the negative writing on the 300mm PF lens has been on the issue of flare associated with the PF design. In practice, only very bright stars show some flare with this lens - but so do other lenses. On the other hand, the lens is by far the lightest in its class, has very low chromatic aberration and is exceptionally sharp in the image centre - and all of these are definite positives for astrophotography. You might want to check out the photos by Atigun in this forum to see examples of what can be achieved with the 300mm PF lens.

Regards,

Andy

Andy Lucy said:

I continue to try and get the most out my 300mm PF lens on the Nikon J5 camera, since this combination allows reasonable images of DSOs as small as 10 arcminutes across – e.g. the Cigar galaxy. With the small plate scale of 1.63 seconds guiding is necessary on the Star Adventurer to achieve sufficiently low RA error.

A 77-62mm step down ring (equivalent to f/4.8) was used to improve star shapes obtained with the 300mm PF f/4. This seems to give much better star shapes than f/4 images (previously described – with some justification - as “horrible shapes”).

Click to expand...

Thank you for the encouraging post - I own both the 300 PF and 500 PF and plan to use both for DSO astrophotography. My biggest concern was the flare problem that many seemed to talk about but very few had examples of. From what I understand the 500 PF has coatings that the 300 PF does not have to help reduce flare. We shall see how it works. I'm just getting back into AP after several years away, so any issues will likely be with my technique rather than the lens.

Thank you again for this post, it gives me hope in being able to use my light telephoto lenses in situations where I need to reach for certain objects.

I'd be very interested to see how you get on for DSOs with the 500mm PF, particularly on a full frame camera. The MTF charts indicate that the 500mm PF could be much better than the 300mm PF at the edges of the frame, and the improved coatings should help as well. The lenstip review for the 500mm PF also indicated that it could be very good for astrophotography:

https://www.lenstip.com/540.11-Lens_review-Nikon_Nikkor_AF-S_500_mm_f_5.6E_PF_ED_VR_Summary.html

Regards,
Andy

Thank you so much for your reply.

Did not even know about stepdown rings.... and how they attach !

I will be waiting for the results of your experiment with the D7100 (which I own).

I LOVE my 300mm F4 PF. It is light and so sharp. I use it for birds in flights (etc) and I am very happy with it. But a guy I know, more knowledgeable than me in photography, has tried it for AP and ended up selling it .... So I never tried it for AP !

A lovely image of M81, M82 and NGC 3077. Well done!

Andy Lucy said:

Breughel,

Thanks for your comments on the image.

The step down ring attaches to the lens filter thread as shown, so works with any camera. However, since the visible optical aberrations from the lens are much more severe away from the image centre, the step down ring will have most impact on images from large sensors - particularly in the image corners.

The f/4.8 equivalent setting with this step-down ring seems to work well when using the J5 with its 1-inch sensor. I plan to test it with an APS-C camera (Nikon D7100) next time there is some clear sky...

Most of the negative writing on the 300mm PF lens has been on the issue of flare associated with the PF design. In practice, only very bright stars show some flare with this lens - but so do other lenses. On the other hand, the lens is by far the lightest in its class, has very low chromatic aberration and is exceptionally sharp in the image centre - and all of these are definite positives for astrophotography. You might want to check out the photos by Atigun in this forum to see examples of what can be achieved with the 300mm PF lens.

Regards,

Andy

Click to expand...

Nice Bode's and Cigar galaxies Andy. Nice to see that the J5 does not have the 0.8 sec exposure limit with the FT1-1 adapter. Thanks for pointing to my images with the 300PF.

You might find my recent test comparing two different bodies effect on the flare of the 300PF interesting: https://www.dpreview.com/forums/post/62015698 , D5100 showed more pronounced flare than the D7100 when tested on an artificial "star cluster". I also included a couple of real deep space captures, but from different nights.

Here is a capture of the Bode's and Cigar galaxies with the 300PF at f/4.5 (lens stopped down) on D7100, tracked with the SkyTracker, about 1 hour total integration time, 2x Drizzle in DSS, on a not so moonless night (posted a couple of years back).


ode's and Cigar galaxies with the 300PF at f/4.5 on D7100, tracked with the SkyTracker, about 1 hour total integration time, 2x drizzle in DSS.

--

Atigun valley, a place north in Alaska

Bill,

Many thanks for the comment - and for identifying NGC 3077. I had wondered what it was but was confused since it doesn't seem to have any image in Stellarium.

Regards,


Andy

The J5 gives a resolution enhancement over the D7100, but the small J5 pixels make low level noise harder to manage. If you look closely at my Bode's / Cigar image you can see a faint, broad, dark green grid - your image is cleaner.

I used 30s exposures with the J5 and FT1 adaptor, which is just about sufficient at f/4.8. However, I've recently found that if you block the electrical contacts on the FT1 the bulb mode becomes undisabled - and this allows exposures up to 2 minutes. Unfortunately you can't use the intervalometer with bulb mode, and there is no remote control on the J5, so you have to start the exposure by touching the touchscreen (preferably with exposure delay enabled) and either wait two minutes or touch the screen again to end the exposure. In fact, a generic manual adaptor for F-mount lenses to Nikon 1 (about 10% of the cost of the FT1 adaptor) also allows bulb mode to be used. The absence of AF, metering etc with a manual adaptor doesn't matter for AP.

Andy

Andy Lucy said:

The J5 gives a resolution enhancement over the D7100, but the small J5 pixels make low level noise harder to manage. If you look closely at my Bode's / Cigar image you can see a faint, broad, dark green grid - your image is cleaner.

I used 30s exposures with the J5 and FT1 adaptor, which is just about sufficient at f/4.8. However, I've recently found that if you block the electrical contacts on the FT1 the bulb mode becomes undisabled - and this allows exposures up to 2 minutes. Unfortunately you can't use the intervalometer with bulb mode, and there is no remote control on the J5, so you have to start the exposure by touching the touchscreen (preferably with exposure delay enabled) and either wait two minutes or touch the screen again to end the exposure. In fact, a generic manual adaptor for F-mount lenses to Nikon 1 (about 10% of the cost of the FT1 adaptor) also allows bulb mode to be used. The absence of AF, metering etc with a manual adaptor doesn't matter for AP.

Andy

Click to expand...

Thanks Andy for the tip about taping the contacts. I always thought my AW-1 was limited to 0.8sec, but just tried the response without the FT-1 attached. I thought I would get a lens not attached message, but this time I could go all the way down to bulb mode. The AW-1 is my favorite for moon and sun imaging, exposing to the right with 300PF/TC-14E - I might try a tracked moon eclipse next time I get a chance if this continues to work (last one failed miserably with AW1 and I had to revert to D7100).

I have the wireless adapter for the AW1, however that turns everything to automatic mode so there is hardly any control from the cell phone.

--
Atigun valley, a place north in Alaska

Andy Lucy said:

I'd be very interested to see how you get on for DSOs with the 500mm PF, particularly on a full frame camera. The MTF charts indicate that the 500mm PF could be much better than the 300mm PF at the edges of the frame, and the improved coatings should help as well. The lenstip review for the 500mm PF also indicated that it could be very good for astrophotography:

https://www.lenstip.com/540.11-Lens_review-Nikon_Nikkor_AF-S_500_mm_f_5.6E_PF_ED_VR_Summary.html

Regards,
Andy

Click to expand...

Finally have some clear skies and the 500 PF is grabbing some lights...

Breughel,

This image was taken with the 300mm PF lens on a D7100 using a 77-62mm step down ring, equivalent to a f/4.8 aperture. 60s exposure at iso 800 on a guided star adventurer mount. Captured in raw and then converted to a jpeg in lightroom but with no processing (including no chromatic aberration removal, no profile corrections, no levels adjustment).

In the corners the stars are egg-shaped, but overall I think the star shapes are not too bad.

Andy

Thank you so much Andy

Wanted to try but the weather is definitely NOT cooperating around here (Montreal).

Indeed, the stars are OK in the center and get to be egg shaped the closer one gets from the corner

Not perfect but very far from the disastrous images I was shown

Thanks again

P