Nereid (m 18.7) - the third largest of Neptune’s moons

[Dennis]

Since fitting an ESATTO 2 inch motorised focuser to the Mewlon 210 and enjoying the larger FOV of the ASI1600MM Pro, I am re-visiting some old targets as I shake down the new gear and techniques.

I captured 60x60 secs of Neptune and an old favourite, Nereid a faint moon of Neptune (mag 18.7) on 24th and 27th August using the Tak Mewlon 210 and ASI1600MM.

Nereid is the third largest of Neptune’s moons, and the second to have been discovered. It was discovered on 1st May, 1949 by the Dutch American astronomer Gerard P. Kuiper (for whom the Kuiper Belt is named) using photographic plates from the McDonald Observatory in Fort Davis, Texas. It is named after the numerous daughters, called Nereids, of the sea god Nereus in Greek mythology.

Nereid has a diameter of about 340 km (210 miles). It revolves around Neptune with a period of just over 360 days in a highly elliptical orbit—the most eccentric of any known moon—that is inclined by more than 7° to the planet’s equator. Its mean distance from Neptune is 5,513,400 km (3,425,900 miles), which is about 15 times farther from Neptune than Triton. Nereid is exceedingly faint, making observations with even the largest Earth-based telescopes very difficult.

• #1 – the FOV combined for both nights showing the movement of Neptune, Triton and Nereid over that period.
• #2 – a cropped region focusing on these bodies.
• #3 - #2 annotated
• #4 - #2 with an overlay from SkyTools 4 Imaging to show the magnitudes of some of the field stars.

The ASI1600MM delivers a 29x22 arcmin FOV at 0.38 arcsec/pixel and a plate solve indicates the Mewlon 210 F11.5 with the Tak x0.8 Reducer/Flattener at the spacing I have it, gives me a fl of 2080mm at F9.9.

I am very satisfied with the ESATTO 2” Robotic Focuser and having the ability to inject automated @Focus3 “focusing runs” with The Sky X Pro, along with the Dithering option in The Sky X Pro and the Batch Processing Script in PI, when all combined have certainly breathed new life into the hobby for me. I was stuck in the 1990’s with techniques acquired in the era of small chips and manual methods.

Cheers

Dennis

[PeterM]

Just brilliant Dennis!
Fabulous to see "amateurs" pushing the limits and going off the well worn and beaten track of the usual suspects, bravo.

Did a little googling and found this interesting arxiv paper. The abstract and introduction are about as far as I got but this caught my eye "Nereid has the most unusual photometric history of all objects in the Solar
System."
https://arxiv.org/ftp/arxiv/papers/0804/0804.2835.pdf

[multiweb (Marc)]

Great stuff Dennis. Love the annotated version.
Do you drizzle? I'm surprised because you're already over sampling at that FL aren't you? Or do you mean dithering to reduce noise?

[Dennis]

Originally Posted by PeterM

Just brilliant Dennis!
Fabulous to see "amateurs" pushing the limits and going off the well worn and beaten track of the usual suspects, bravo.

Did a little googling and found this interesting arxiv paper. The abstract and introduction are about as far as I got but this caught my eye "Nereid has the most unusual photometric history of all objects in the Solar
System."
https://arxiv.org/ftp/arxiv/papers/0804/0804.2835.pdf

Thanks Peter, I appreciate your comments.

Cheers

Dennis

PS - I have saved the file in your link for a bed time read - thanks heaps.

[Dennis]

Originally Posted by multiweb

Great stuff Dennis. Love the annotated version.
Do you drizzle? I'm surprised because you're already over sampling at that FL aren't you? Or do you mean dithering to reduce noise?

Thanks Marc, looks like I got my drizzling and dithering all mixed up.

I meant "Dither" where I set The Sky X Pro to Dither for 1 Pixel with a settle of 0.5 Pixels for every frame.

Before I discovered the art of Dithering, my Aligned & Stacked Frames were awful, despite all the Bias, Darks, Flats, Normalisation, etc. and I had pesky noise pixels wandering all over the place but Dithering fixed all of that at a single stroke. Yipee.

So much new stuff to learn.

Cheers

Dennis

[multiweb (Marc)]

Originally Posted by Dennis

Thanks Marc, looks like I got my drizzling and dithering all mixed up.

I meant "Dither" where I set The Sky X Pro to Dither for 1 Pixel with a settle of 0.5 Pixels for every frame.

Before I discovered the art of Dithering, my Aligned & Stacked Frames were awful, despite all the Bias, Darks, Flats, Normalisation, etc. and I had pesky noise pixels wandering all over the place but Dithering fixed all of that at a single stroke. Yipee.

So much new stuff to learn.

Cheers

Dennis

That new focuser really looks the part. Jealous.

[Dennis]

Originally Posted by multiweb

That new focuser really looks the part. Jealous.

Hi Marc

I used to shoot say 10x3 min subs, Pause, slew to a focusing star (field), fit Bahtinov Mask, touch up the focus, remove Bahtinov Mask, slew back, re-frame and shoot another set of subs. And I still suffered from focus drift, possibly mechanical rather than thermal.

Now, I can just inject an @Focus3 focus run in The Sky X Pro (Camera Add On) and in the 3 or 4 weeks where I have been doing this, it all seems to work very well.

The ESATTO has 0.04 micron steps and makes a lovely noise when focusing. Oh, and its also a nice, bright, Italian Red colour.

Cheers

Dennis